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Effects of a rubber-slatted flooring system on cleanliness and foot health in tied dairy cows
Preventive Veterinary Medicine 52 (2001) 75±89
Effects of a rubber-slatted ¯ooring system on cleanliness and foot health in tied dairy cows Jan Hultgren*, Christer Bergsten Department of Animal Environment and Health, Swedish University of Agricultural Sciences, P.O. Box 234, SE-532 23 Skara, Sweden Received 29 November 2000; accepted 16 May 2001
Abstract Effects on animal cleanliness and foot health of a new rubber-slat system for tied dairy cows, with the ability to drain faeces and urine, were studied in a 2-year controlled quasi-randomised trial in a Swedish university herd. Swedish Red and White cows were kept tied in 42 traditional longstalls with rubber mats. In total, 82 cows were observed. In 21 stalls, the rearmost 0.74 m of the solid stall ¯oor was replaced with nine rubber-coated 53 mm wide slats, divided by 29 mm slots. The cleanliness was assessed subjectively weekly (year 1) or bi-weekly (year 2) by observations of the hind part of the body. Claw measurements and foot health in hind feet were assessed in connection with hoof trimmings at the beginning, middle and end of the housing period. The foothealth recordings were blinded to ¯ooring. For the analysis of both cleanliness (1781 records, 73 cows) and foot health (240 records, 79 cows), logistic regression was applied, using marginal models and cow observations as repeated measures within each year. The risk of getting dirty on the rubber-slatted ¯oor was signi®cantly lower (odds ratio 0.12 for hind feet when short stall dividers were used, 0.39 for hind legs and 0.38 for thighs and udder), comparing with the solid stall ¯oor. The prevalence of foot diseases in hind feet at trimming was signi®cantly lower on the rubber slats (odds ratio 0.23 for dermatitis, 0.09 for heel horn erosion, and 0.34 for sole ulcer or sole or white line haemorrhage). # 2001 Elsevier Science B.V. All rights reserved. Keywords: Dairy cattle; Housing; Floor; Cleanliness; Digital dermatitis; Interdigital dermatitis; Heel horn erosion; Laminitis; Sole haemorrhage; Sole ulcer
1. Introduction Intensive milk production with high-yielding cows requires excellent housing, management and feeding to maintain proper hygiene and to avoid environmentally evoked diseases. Two of the most-common production diseases are foot and udder disorders. *
Corresponding author. Tel.: 46-511-67103; fax: 46-511-67134. E-mail address: [email protected] (J. Hultgren). 0167-5877/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 8 7 7 ( 0 1 ) 0 0 2 3 7 - 9
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With intensi®ed diets, larger herds and less labour spent on each cow, hygienic conditions are impaired and hygiene-related foot disorders are common during the housing season. Some of the most-prevalent contagious and hygiene-dependent foot diseases are interdigital and digital dermatitis, and heel horn erosion (Andersson and LundstroÈm, 1981; Murray et al., 1996; RodrõÂguez Lainz et al., 1996). In a recent study of Swedish dairy cows' hoof health, heel horn erosion was found in 67% and dermatitis in 30% of cows examined during the housing season (Manske, T., Swedish Univ. Agric. Sci., 2001, pers. commun.). Foot disorders are of great economical as well as animal welfare concern (Kossaibati and Esslemont, 1997; Noordhuizen, 1998; Broom, 1996). Dermatitis in the bovine foot may be caused by bacterial or viral infections, by parasitic infestations or by mechanical or chemical in¯uences. Both digital and interdigital dermatitis are in part due to poor ambient hygienic conditions (Walker et al., 1995; RodrõÂguez Lainz et al., 1996; Bergsten, 1997). Heel horn erosion is an irregular loss of bulb-horn tissue (Collick, 1997), which may be caused by poor ambient hygienic conditions. However, its principal cause is most likely dermatitis in the interdigital cleft or on the bulbs (Toussaint Raven et al., 1985). Laminitis is a non-infectious in¯ammation of the soft tissue of the claw, inside the horn capsule (Nilsson, 1963). Risk factors include a concentrated diet, trauma, overloading and infections (Ossent and Lischer, 1998). Previous cases of laminitis are seen at trimming as discolourations of the claw horn of the sole (Peterse, 1980). A sole ulcer is a defect in the sole horn, probably caused primarily by laminitis, poor horn quality and overloading of a limited area of the sole (Nilsson, 1963; Greenough, 1985; Ossent and Lischer, 1998). In Sweden, most cases of foot diseases are treated at routine hoof trimming, which is generally performed once or twice a year (Hultgren et al., 1998). Incidence estimates based on veterinary-treated cases alone probably depart greatly from true incidences. Based on observations of 2011 cows in 50 Swedish dairy herds at routine hoof trimming in the spring of 1996 and 1997, the prevalence of moderate or severe heel horn erosion was 46%, severe sole haemorrhage 15% and sole ulcer 14% (Bergsten et al., 1998), while the lactational incidence of veterinary-treated cases of all foot disorders during the same period was only 2.1% (Swedish Dairy Association, 1997). Because foot diseases generally last for most of the lactation or housing period (Andersson and LundstroÈm, 1981; Singh et al., 1993), prevalences at trimming should be fairly good estimates of the lactational (or yearly) incidences. In Sweden, dairy cows are housed except for 2±4 months of grazing from May to October, with approximately 80% of the animals kept tied in either short-stalls or longstalls. Loose housing has been recommended and tends to be used in newer dairy facilities Ð but in the near future, most Swedish dairy herds probably will remain tied. To keep short-stalls cleaner, feeding barriers have been developed that restrict the cow's space and thus increase the likelihood that she defecates in the gutter. An alternative way of improving hygienic conditions and animal comfort Ð without restricting the cows' movements Ð is to equip the stalls with a ¯ooring that drains faeces and urine. Mainly due to concerns about udder health and cow comfort, traditional concrete or wooden-slatted ¯oors have not been permitted for tied cows in Sweden. Rubber-coated slatted ¯ooring might, however, have less-adverse effects on animal health and comfort.
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Since the seventies, a type of rubber-slatted ¯ooring has been used in a Swedish beef herd of foster cows. It was a further development of that rubber-slat system that was tested in this study. Our objective was to evaluate the effects of a manure-draining rubber-slat system on hygiene and foot health in tied dairy cows. This was carried out as part of a pre-testing procedure for new housing equipment according to the Swedish statute on animal protection. Behavioural effects are reported elsewhere (Hultgren, 2001). 2. Material and methods 2.1. Animals and management system The study was carried out during two consecutive housing periods (1997±1999, years 1 and 2) in an experimental dairy herd of Swedish Red and White cows belonging to the Swedish University of Agricultural Sciences. The animals were tied in two rows of 21 long-stalls each, on either side of an aisle with mangers. Totally 82 cows were observed. Stall length was 2.20 m and mean stall width 1.19 m (range 1.11±1.23 m). The stall fronts had self-locking feeding barriers that were kept unlocked except during milking. Short (0.50 m) or long (0.85 m) stall dividers were placed between every second cow. In one of the rows (with 21 stalls), the rearmost 0.74 m of the solid ¯oor was replaced with a new type of slatted ¯ooring (Fritz Foderstyrning AB, NaÈssjoÈ, Sweden; Fig. 1). The slatted ¯oor had nine rubber-coated, 53 mm wide slats and the slots between them were 29 mm wide. The underlying manure gutter was cleaned with a similar scraping system to the rest of the building. During several housing periods preceding the study, all cows had been kept tied in ordinary solid-¯oored long-stalls with rubber mats. They were grazed from May to September. The cows calved in a separate maternity pen.
Fig. 1. Design of the rearmost part of the stall floor and manure gutter in stalls equipped with rubber-slatted flooring (mm).
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The anterior solid part of the stalls with rubber slats had ethyl-vinyl-acetate mats (Komfort, DeLaval AB, Tumba, Sweden) and each stall was bedded twice daily using approximately 1 kg of chopped straw (study week 1±17 during year 1) or 0.7 kg of wood shavings (the rest of the study) per day. The stalls with solid ¯oor had rubber mats (Gummimattan Marianne Larson AB, Gothemburg, Sweden) and received 3 kg of chopped straw per day given in the morning and afternoon. The herdsman was present in the building from 5:30 to 10 a.m. and from 1:30 to 5:30 p.m. The cows were fed concentrates individually ®ve times and silage four times daily from a computerised feeding wagon, according to production. All lactating cows were fed 2 kg hay manually twice daily; dry cows received additional straw. Water bowls were placed in the stalls between each cow. The cows were milked in their stalls twice daily. The herd average milk production during the 2-year period was 10,400 kg energy-corrected milk (ECM). The stall ¯oor was scraped clean of manure manually before and after milking and whenever the herdsman found it necessary. In November both years, all animals were sheared with an electric clipper on their hind parts, including the tails. Furthermore, all cows were groomed manually twice daily, after feeding and milking in the morning and before feeding and milking in the afternoon; the most contaminated body parts (hock, thigh, gaskin, and udder) were cleaned with an ordinary metal curry comb. The feet were not cleaned. In September (at the beginning of both housing periods), all cows were distributed between the two stall rows to achieve a strati®ed random allocation of treatments. This was done by listing the cows in order of parity and number of days in milk (or, in the case of heifers, days before expected calving). Every second cow on the list (random start by coin toss) was placed in a stall with rubber-slatted ¯oor. No cow changed group during the housing periods. Throughout the year, cows were culled and replaced by heifers in late pregnancy, all of which had been kept tied in long-stalls in another building. No culling was related directly to foot disorders. 2.2. Records of cleanliness Contamination of animals with manure was scored by the same person once a week during year 1 and once every second week in year 2. The observations were made in the morning, before grooming and milking, so the animals had been exposed to the different ¯oor types for at least 12 h without any cleaning measures. For practical reasons, the recordings were not blinded to ¯ooring. The extent of contamination with manure on the hind parts of the cows was assessed visually on a 4-level ordinal scale (Table 1). The recording system was developed by the authors for the speci®c purposes of this study, based on earlier experiences (Hultgren, 1999). Nine separate body divisions were rated: left and right hind foot (the dorsal part of the claws, the pastern and the dew claws), left and right hind leg (above the foot and including the hock area), left and right thigh (the gaskin, the thigh itself, the rump, and the areas around the ilial and ischial tuberosities), left and right side of the udder, and hind part of the udder (Fig. 2). Within each cow record, these scores were added in three groups, resulting in three sum scores, representing three principal body parts, referred to below as
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Table 1 Definition of different levels of scoring of cleanliness, dermatitis, heel horn erosion and sole lesions for dairy cows Trait
Score
Definition
Cleanliness
0 1
No or almost no contamination with manure One solitary large spot or several small spots of manure, together covering less than a fifth of the total area One solitary spot or several small spots of manure, together covering between one fifth and half of the total area More than half of the area covered by manure Skin of the foot intact Exudative or hyperkeratotic/proliferative dermatitis; erosions and(or) ulcerations Intact heel horn or superficial loss of heel horn (``pitting'') Marked fissures or craters No haemorrhage of the solar horn or only slight haemorrhagic discolouration of the horn (``paint brush'') Extensive and(or) distinct, more profound haemorrhage, not disappearing at slight trimming Intact sole horn Exposed corium on the solar surface
2 3 0 1
Dermatitis Heel horn erosion Sole/white line haemorrhage
0 1 0 1
Sole ulcer
0 1
foot, leg and body (thighs and udder). A total of 1781 cow-cleanliness records were obtained from 73 cows. 2.3. Records of claw measurements and foot diseases Claw measurements, hoof trimming and assessment of foot diseases were carried out in all animals at 3±4-month intervals; shortly after housing (September 26, year 1; October 22, year 2), half way into the housing period (January 22, year 1; February 17, year 2) and shortly before grazing (April 30, year 1; May 5, year 2). Claw measurements before
Fig. 2. Divisions of the hind part of the body for assessment of cleanliness.
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trimming included toe length (measured with vernier callipers) and lower toe angle (measured with a special angle meter at the distal 2 cm of the dorsal toe wall). Trimming and recording were carried out outside the cowshed, and the observer was not aware on which type of ¯ooring the examined cows were kept. In accordance with Bergsten (1995), severity of foot dermatitis heel horn erosion, haemorrhage of the sole, haemorrhage of the white line and sole ulcer were assessed in all hind feet on 2- or 4-level ordinal scales, which later were reduced to 2 levels (Table 1). The choice of cut-off points was based on a judgement of the clinical importance of the lesions. The presence of wart growth (papillomatous dermatitis), interdigital hyperplasia (®brous growth of the interdigital skin), white line separation (®ssure in the white line), double sole (two separate layers of sole horn), and abnormal claw shape (asymmetric or cork-screw claw) was noted. Similar recordings had been made during the housing period prior to the study (trimmings on February 7 and May 9, year 0). Three veterinary researchers were engaged in the recording, two of which recorded at only one occasion each (May of year 0 and 2). At each occasion, all recordings were made by the same veterinarian. Between trimmings, any of two veterinary researchers recorded all new cases of foot diseases. The intrarater reliability of the scoring system was assessed in a separate analysis using photographic slides and judged to be good, with averaged kappa coef®cients (for three raters) above 60% for heel horn erosion, haemorrhages of the sole and the white line, sole ulcer, dermatitis and white line separation (Manske, T., Swedish Univ. Agric. Sci., 2001, pers. commun.). A total of 330 cow foot health records were obtained from 82 cows. 2.4. Statistical analyses The effects of ¯ooring (FLOOR; 0: solid ¯oor; 1: rubber-slatted ¯oor) on cleanliness and foot health were analysed using the generalised estimating equations (GEE) approach (Liang and Zeger, 1986), the GENMOD procedure in SAS (SAS, 1997) and six logistic regression models, speci®ed further below. All models had the following general form: X g E Y a bm X m where g is the logit link function, E(Y) the expected values of the outcome variable Y, a the intercept and bm the regression coefficients for the included predictor variables Xm. Manure contamination on the three principal body parts was expressed by the binary outcome variables FOOT, LEG, and BODY. These were assigned a value of 1 for sum scores of at least 5, 4 and 6 (of maximum 6, 6 and 15), respectively, and a value of 0 for lower sum scores. The cut-off points were chosen before the analysis, based on the objective of the study and to achieve maximum relevance. Foot health was expressed by the three binary outcome variables DERM, HEEL, and SOLE. DERM and HEEL assumed a value of 1 for occurrence of dermatitis or heel horn erosion, respectively, in at least one of the hind feet. Similarly, SOLE received a value of 1 for occurrence of sole/white line haemorrhage or sole ulcer in at least one of the hind feet. For non-occurrence, the variables assumed a value of 0. All heifers (17 records) were excluded from the foot health data, to allow for a certain period of exposure before assessment of ¯oor effects.
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Study year was expressed by the class variable YEAR (1, 2). In the analysis of foot health, one additional level of YEAR (0) was introduced, representing the preceding housing period (1996±1997). Each record of a cow at a given occasion was regarded as an observation, resulting in repeated measures. The variable COW (eartag number), nested within YEAR, was included in the models as the subject effect (SAS, 1997). Thus, observations of a cow were assumed to be correlated only if they were from the same year (35 animals were present during only 1 year, 35 animals during 2 years and 12 animals during all 3 years). Recording occasion within YEAR was expressed by the class variable REP, entered into the models as the within-subject effect (SAS, 1997). In the case of cleanliness, REP contained the number of weeks since the beginning of housing 1; 2; 3; . . . ; 32, and in the analysis of foot health it represented trimming occasion (1, 2, 3). An exchangeable correlations structure was speci®ed (assuming all within-cow correlations between observations to be equal). The type of stall divider (on one side of each cow) was expressed by the dichotomous variable DIVIDER (0: short; 1: long). The type of bedding material was contained in the dichotomous variable LITTER (0: wood shavings; 1: straw). PARITY (1: ®rst parity; 2: second parity or older) was used to express age. The number of days in milk or, in heifers, the estimated number of days until calving (negative value) was expressed by the continuous variable DIM, which also was squared (SQ) to obtain DIMSQ. The individual milk yield was expressed by the continuous variable YIELD (kg ECM per day) and YIELDSQ. Yields on days of cleanliness and foot health recordings were calculated by interpolating between the yields at the two nearmost monthly routine milk recordings. For heifers and dry cows, YIELD was given a value of 0. In the analysis of foot health, the nominal variable VET (A, B, C) was used to identify the veterinary researcher who did the recording. The variation according to categorical explanatory variables in the cleanliness and foot health data is shown in Table 2. DIM median interquartile range for solid versus rubber-slatted ¯oors were 114 144 and 102 143 (cleanliness data), and 151 144 and 142 184 (foot health). YIELD median interquartile range for solid versus rubber-slatted ¯oors was 32:4 12:2 and 32:0 12:5 (cleanliness), and 34:0 12:0 and 34:3 10:7 (foot health). The correlation between independent variables was checked and the associations found were considered unlikely to cause any substantial multicollinearity r < 0:75. The models were formed by a manual backward stepwise procedure, starting with full models of main effects and excluding or re-entering one of them in each step. In the analysis of cleanliness, the independent variables FLOOR, YEAR, REP, DIVIDER, LITTER, PARITY, DIM, DIMSQ, YIELD and YIELDSQ were tested initially. In the analysis of foot health, the potential confounders YEAR, REP, VET, DIVIDER, LITTER, PARITY, DIM and YIELD were included with FLOOR in the full models. FLOOR was forced into all models and the criterion used for inclusion of other effects was a >15% change in the coef®cient estimate for FLOOR. Having selected main effects, ®rst-degree interaction terms with FLOOR were tested for inclusion, using a backward elimination procedure and a signi®cant likelihood-ratio test P 0:05 as the inclusion criterion. Odds ratios (OR) for FLOOR were calculated. In the analysis of cleanliness, all 1781 observations (101 cow-year clusters) were used. Interaction was found between FLOOR and DIVIDER. Therefore, the corresponding
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Table 2 Distribution of observations according to categorical explanatory variables in cows on solid and rubber slatted floor, in a study of cleanliness and foot health in 82 Swedish Red and White cows in 1997±1999 Variablea
Level
Cleanliness
Foot health
Solid floor n
%
Slatted floor
Solid floor
n
%
n
Slatted floor %
n
%
YEAR
0 1 2
± 605 292
± 67 33
± 594 290
± 67 33
79 63 63
39 31 31
0 62 63
0 50 50
DIVIDER
0 1
702 195
78 22
153 731
17 83
166 39
81 19
30 95
24 76
LITTER
0 1
0 897
0 100
613 271
69 31
0 330
0 100
83 42
66 34
PARITY
0 1 2
61 365 471
7 41 53
62 366 456
7 41 52
9 87 109
4 42 53
8 51 66
6 41 53
VET
A B C
± ± ±
± ± ±
± ± ±
± ± ±
144 40 21
70 20 10
104 0 21
83 0 17
a
For a detailed explanation of variables, see text.
model was constructed with FLOOR nested within DIVIDER. In the three models, 1349, 1091 and 837 observations, respectively, were cases response 1. The ®nal models were speci®ed as: FOOT FLOOR DIVIDER DIVIDER LITTER; LEG FLOOR DIVIDER LITTER; BODY FLOOR DIVIDER LITTER YIELD All autumn trimming records of foot health were omitted from the final analysis, because the foot status at these occasions was considered to reflect mainly the benefits of the grazing period. To check for differences between the two floor groups at the beginning of the housing period, FLOOR was replaced by a predictor with four levels REP 1 and FLOOR 0; REP 1 and FLOOR 1; REP > 1 and FLOOR 0; REP > 1 and FLOOR 1. There was no significant P > 0:15 difference between the two types of flooring at autumn trimming. Finally, FLOOR was used and the model selection procedure was repeated. In total, 240 observations (79 cows, 125 cow-year clusters) were used. In the three models, 49, 80 and 75 observations, respectively, were cases. The three final models were specified as follows: DERM FLOOR YEAR VET; HEEL FLOOR YEAR; SOLE FLOOR YEAR DIVIDER LITTER The associations between foot health at trimming (DERM, HEEL and SOLE) and cleanliness at all recordings since the previous trimming (means of FOOT, LEG and
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BODY) were assessed by a correlation analysis on all observations at the third trimming of years 1 and 2 (83 observations). To indicate stall cleanliness and support the interpretation of results regarding foot lesions, a piece of sole horn from 13 randomly selected cows, among which seven were kept on rubber slats, was analysed for dry-matter content at each of the three trimming occasions during year 1. The means for the two ¯oor groups were compared using Student's t-test. 3. Results 3.1. Cleanliness When compared to the solid ¯oor, the rubber-slatted ¯oor was associated with signi®cantly lower odds of manure contamination on foot when short stall dividers were used, and on leg and body with either type of stall divider (Table 3). With long stall dividers, there was only a tendency for reduced odds of manure contamination on foot. Generally, there were only small differences in cleanliness between recording. Based on the chosen cut-off points for response variables, the overall percentages of cows considered to be dirty on foot, leg and body on solid and rubber slatted ¯oors were 91 and 61, 80 and 43, and 59 and 35%, respectively. The cleanliness models ®t the data relatively well, as judged by the ratios of the deviances to their degrees of freedom (0.90, 1.15 and 1.25, respectively). A comparison between observed and expected percentages of cases in each stratum of discrete covariates (FLOOR, DIVIDER and LITTER) revealed only small-to-moderate differences. In the three models, the correlation between two observations of a given cow was estimated to be 0.23, 0.34 and 0.30, respectively. 3.2. Foot health Generally, foot disorders were much less common at the autumn trimming (shortly after the start of housing) than at the two trimmings in the spring, while the differences between Table 3 Effect of rubber-slatted versus solid flooring on contamination with manure on hind feet (FOOT), hind legs (LEG), and thighs and udder (BODY) in a study of 73 Swedish Red and White cows in 1997±1999; three logistic regression models using 1781 observations Outcomea
Effect in model
Stall divider
FOOT
FLOOR (DIVIDER) FLOOR (DIVIDER) FLOOR FLOOR
Shortb Longc ± ±
LEG BODY a
b 2.14 0.68 0.94 0.96
For a detailed explanation of traits and models, see text. Using long stall divider as base level. c Using short stall divider as base level. b
S.E. (b)
P
OR
95% CI for OR
0.53 0.53 0.43 0.39
<0.001 0.20 0.03 0.01
0.12 0.50 0.39 0.38
0.04, 0.18, 0.17, 0.18,
0.33 1.43 0.91 0.82
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Table 4 Mean prevalences (%) of recorded foot diseases at hoof trimming in January±February and April±May years 0, 1 and 2, in cows on solid and rubber slatted floora; Swedish Red and White cows 1997±1999 Disease
Dermatitis Heel horn erosion Sole or white line haemorrhage Sole ulcer White line separation Double sole Abnormal claw shape a
Year 0, solid floor n 79
Year 1
Year 2
Solid floor n 42
Slatted floor Solid floor n 41 n 42
Slatted floor n 42
29 59 33 8 13 0 0
36 38 36 2 12 0 0
7 0 49 0 15 0 2
7 10 12 0 12 2 5
17 33 17 7 21 2 0
For a detailed explanation of diseases and groups, see text.
the latter were smaller. Table 4 shows the mean prevalences of all recorded foot disorders at the two spring trimming occasions during years 0, 1 and 2 in the two ¯oor groups. The dynamics (year and repetition) of the prevalences of dermatitis, heel horn erosion and sole lesions in the two ¯oor groups is presented in Fig. 3. No cases of wart growth or interdigital hyperplasia were found. Table 5 shows the models of foot health. When compared to solid ¯oors, the rubber-slatted ¯ooring was associated with signi®cantly lowered odds of dermatitis and heel horn erosion. There was also some indication of a reduced risk of sole lesions. The foot-health models ®t the data relatively well (ratios of the deviances to its degrees of freedom were 0.91, 1.03 and 1.18, respectively). Comparing observed and expected percentages of cases in each stratum of discrete covariates (FLOOR, YEAR, VET, DIVIDER, and LITTER), only small to moderate differences were found. For the three outcomes, the correlation between two observations of a given cow was estimated to be 0.07, 0.16 and 0.05, respectively. In the group of cows on solid ¯oor, four incidents of lameness were recorded and treated between regular trimmings. These were diagnosed as one case of sole haemorrhage, one of sole ulcer and two of white line separation. Only one case of lameness due to sole haemorrhage was treated in the group of cows on rubber slats. The overall mean (and S.D.) of toe length and lower toe angle before trimming in cows on solid and rubber slatted ¯oor were 85 mm (6.7 mm), 82 mm (7.0 mm), 428 (6.08) and 408 (6.48), respectively. There were only small variations between trimming occasions. Dry-matter content of claw horn mean S:D: at the three trimmings year 1 was 71 4:9%; 72 4:7% and 69 4:9% on slatted ¯oor, and 67 2:2%; 68 5:2% and 62 3:2% on solid ¯oor t24 2:46; P 0:02. The correlation between foot health and cleanliness was low to moderate (Table 6). Signi®cant Pearson correlation coef®cients were found between HEEL and FOOT, HEEL and LEG, HEEL and BODY, and SOLE and FOOT. The three cleanliness outcomes were fairly strongly correlated with each other, and there was also correlation between DERM and HEEL.
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Fig. 3. Prevalences of dermatitis, heel horn erosion and sole lesions (haemorrhage or ulcer) in cows on solid (Ð) and rubber slatted (- - -) floor at hoof trimmings 1±3 of years 0±2 in a study of Swedish Red and White cows in 1997±1999; in each floor group, n 39 40 year 1 and n 17 21 years 2±3. Table 5 Effect of rubber-slatted versus solid flooring on foot dermatitis (DERM), heel horn erosion (HEEL), and sole lesions (SOLE) in 79 Swedish Red and White cows in 1997±1999; three logistic regression models using 240 observations Outcomea
Effect in model
DERM HEEL SOLE
FLOOR FLOOR FLOOR
a
b 1.48 2.41 1.09
S.E. (b)
P
OR
95% CI for OR
0.50 0.55 0.63
0.003 <0.001 0.08
0.23 0.09 0.34
0.08, 0.61 0.03, 0.27 0.10, 1.16
For a detailed explanation of traits and models, see text.
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Table 6 Correlation between outcomes for foot health at hoof trimming (April of year 1 and May of year 2) and mean cleanliness since previous trimminga in a study of Swedish Red and White cows in 1997±1999 (Pearson correlation coefficients at upper right and corresponding significance levels at lower left); n 83
DERM HEEL SOLE FOOT LEG BODY a
DERM
HEEL
SOLE
FOOT
LEG
± 0.05 0.13 0.09 0.11 0.68
0.22 ± 0.70 <0.001 <0.001 0.002
0.16 0.04 ± 0.001 0.86 0.82
0.19 0.38 0.36 ± <0.001 <0.001
0.18 0.42 0.02 0.64 ± <0.001
BODY 0.05 0.33 0.03 0.42 0.53 ±
For a detailed explanation of traits, see text.
4. Discussion The risk of getting dirty on the rubber-slatted ¯oor was lower, when compared to a solid stall ¯oor, and the prevalence of foot diseases in hind feet at trimming was lower on the slatted ¯oor. Health effects of manure-draining rubber slats as part of the tie-stall ¯oor have not been studied in full scale before. Nilsson and Walberg (1979) studied gratings with a surface of rubber instead of steel, and found no differences in the occurrence of leg injuries. Nilsson and Svennerstedt (2000) tested a rubber-slatted ¯oor system (similar to that we used); the ¯ooring did not seem to change the cows' resting behaviour. In loose-housing facilities, insuf®ciently drained and scraped alleys increase the risk of heel horn erosion and the need for veterinary treatment of other foot disorders, when compared to concrete-slatted ¯ooring (Coehen, 1980; Buchwald et al., 1982; Maton, 1987). On the other hand, badly designed concrete slats in loose-housing result in hoof and leg trauma (Kirchner and Boxberger, 1987). Good drainage promotes a dry ¯oor surface with a lower risk of slipping (Svennerstedt and Praks, 1997) Ð the slats must be wide enough to give suf®cient support for the hooves (Kirchner and Boxberger, 1987). Bedding material generally decreases the draining capacity (Nilsson and Svennerstedt, 2000). After the ®rst months of the present study, wood shavings were used instead of chopped straw (on both types of ¯ooring), because the straw clogged the slots. This in¯uenced cleanliness, too, and a variable indicating litter material was included as a confounder in the multivariable models. All recordings of cleanliness were carried out by the same person, which probably reduced variation. For practical reasons, the recording was not blinded. In the case of foot health, the recording was blinded to ¯ooring, but the data were not balanced with respect to two of the observers. A variable for ``recording veterinarian'' was, however, considered in the foot health models, and the risk of systematic differences in assessment of cleanliness or foot lesions between the two types of ¯ooring was considered small and of no practical importance. Cleanliness scoring systems for loose-housed cattle have been described by, e.g. Scott and Kelly (1989), but were not considered completely appropriate for tied dairy cows. The
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tails were not included in the study, since their cleanliness is mainly in¯uenced by the condition of the gutter, rather than the type of stall ¯oor. Both the cleanliness and foot health data were longitudinal, with repeated measures of individual cows over time resulting in correlated observations. By using the GEE approach, the covariance, standard error and signi®cance-level estimates were adjusted accordingly, and the correlation matrices were computed separately. The within-cow (and within-year) correlation was moderate in the cleanliness analysis, which indicates that some cows were more or less constantly clean Ð while others were constantly dirty (which we feel is a common experience among farmers). In the case of foot health, the within-cow correlation was lower. On foot, the effect of ¯ooring on cleanliness was clear only when short stall dividers were used. This may have been due to long dividers not allowing the cows to move much to the side Ð thus keeping the stalls cleaner and making the slatted ¯ooring less necessary. A variable for stall divider acted as a confounder in all three cleanliness models. However, no signi®cant interaction between ¯ooring type and stall divider type was found in the analyses of cleanliness on leg or body. There is no reason to believe that the two types of ¯ooring should differ with respect to claw horn growth or wear, because both had a rubber surface. The claw measurements did not differ much between the ¯oor groups. When compared to a bare concrete tie-stall ¯oor, rubber mats result in longer toes (Bergsten et al., 1998). We believe the improved foot health on the rubber-slatted ¯oor to be mainly, if not only, an indirect effect of the improved hygienic conditions on the rubber slats. The differences in prevalence of dermatitis and heel horn erosion between the two types of ¯ooring increased distinctly during the housing period, most clearly seen in year 1, in accordance with earlier studies (Andersson and LundstroÈm, 1981; Bergsten and Pettersson, 1992). No strong correlation was found between foot diseases at trimmings in April and May and preceding cleanliness, but the signi®cant relationships agree well with earlier ®ndings that heel horn erosion is associated with poor hygiene. In this study, there was a tendency for a reduced overall prevalence of sole lesions in cows on rubber slats, although both stall types were equipped with mats. It is possible that this reduction was secondary to lower prevalences of dermatitis and heel horn erosion (and thus, superior claw horn quality) Ð but it also might have been due to a slightly softer rubber on the slatted ¯oor. The models ®t the data well. However (as judged by the ratio of deviance to d.f.), there was overdispersion in the data on cleanliness on body. This might be explained by the fact that adjacent animals may become dirty (especially on the thighs and back) from contact with the manure of the neighbouring cow. Alternatively, correlated observations from different years may have caused some clustering at the cow level. Similarly, there was some indication of overdispersion in the data on sole lesions, possibly re¯ecting clustering due to production factors, e.g. milk yield or diet, or slightly correlated observations within cows and between years. The higher dry-matter content of the claw horn found in cows on rubber-slatted ¯oor, and the apparent increasing difference between the two ¯ooring types during the housing period, support cleanliness and foot health ®ndings. Bergsten and Pettersson (1992) were able to show a higher dry-matter content in claw horn from cleaner tie-stalls and
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furthermore a negative correlation between dry-matter content and the presence of heel horn erosion. In this experiment, the rubber-slat system was used in traditional Swedish long-stalls. We believe the effects on cleanliness and foot health would be similar in short-stalls. However, if the stalls are kept relatively clean by other means, the effect of the rubber slats would probably diminish (as was seen in the analysis of cleanliness on hind feet, where there was a signi®cant interaction between the type of stall divider and the ¯ooring). It is not possible to conclude from this study the optimum design of the rubber-slatted ¯ooring (width of slats and slots, percentage of the stall length covered by slats, etc.) or the effects on, e.g. udder health. Available data from the experimental herd, however, do not indicate any such effects (Hultgren, 1999). 5. Conclusions We conclude that the tested rubber-slat system substantially improved the cleanliness of the hind part of tied dairy cows, and reduced the prevalences of foot dermatitis, heel horn erosion and sole lesions (ulcer or haemorrhage) at routine hoof trimming. Acknowledgements The study was carried out with ®nancial support from the Swedish Board of Agriculture, È ST and the Foundation for technology transfer in Gothemburg. We also acknowlAGROVA edge Thomas Manske for foot health recordings, Rune Karlsson and Gunnar Fritz for creative co-operation, and Linda Keeling for assisting with the English. References Andersson, L., LundstroÈm, K., 1981. The influence of breed, age, body weight and season on digital diseases and hoof size in dairy cows. Zbl. Vet. Med. A 28, 141±151. Bergsten, C., 1995. Digital disorders in dairy cattle with special reference to laminitis and heel horn erosion: the influence of housing, management and nutrition. Dissertation. Swedish University of Agriculture Science, Skara, Sweden. Bergsten, C., 1997. Infectious diseases of the digits. In: Greenough, P.R. (Ed.), Lameness in Cattle, 3rd Edition. Saunders, Philadelphia, PA, pp. 89±100. Bergsten, C., Pettersson, B., 1992. The cleanliness of cows tied in stalls and the health of their hooves as influenced by the use of electric trainers. Prev. Vet. Med. 13, 229±238. Bergsten, C., Hultgren, J., Manske, T., 1998. Claw traits and foot lesions in Swedish dairy cows in relation to trimming interval and housing system. A preliminary report. In: Ossent, P., Lischer, C.J. (Eds.), Proceedings of the 10th International Symposium on Lameness Ruminants, Lucerne, Switzerland, September 7±10, 1998, pp. 46±48. Broom, D.M., 1996. Animal welfare defined in terms of attempts to cope with the environment. Acta Agric. Scand. A (Suppl. 27), 22±28. Buchwald, E., Blom, J.Y., Smedegaard, H.H., Thysen, I., 1982. Klovsundhedens afhñngighed af gulvtype og lejetype. In: éstergaard, V., Hindhede, J. (Eds.), 532 Beretning fra Statens Husdyrbrugsforsùg. Report. Copenhagen, pp. 109±119.
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Coehen, J., 1980. Mehr Augenmerk den Klauen schenken. DLG-Mitteilungen 95, 1270±1272. Collick, D.W., 1997. Heel horn erosion. In: Greenough, P.R. (Ed.), Lameness in Cattle, 3rd Edition. Saunders, Philadelphia, PA, pp. 116±118. Greenough, P.R., 1985. The subclinical laminitis syndrome. Bovine Pract. 20, 144±149. Hultgren, J., 1999. Gummispaltgolv foÈr bundna kor och ungdjur. Provning av ny teknik enligt DjurskyddsfoÈrordningen (Rubber-slatted flooring for tied cows and young cattle. Testing of new technical equipment according to the Swedish statute on animal protection). Special Report 9. Dept. Anim. Environ. Health, Swedish Univ. Agric. Sci., Skara, Sweden. Hultgren, J., 2001. Effects of two stall flooring systems on the behaviour of tied dairy cows. Appl. Anim. Behav. Sci. 73, 167±177. Hultgren, J., Bergsten, C., Manske, T., 1998. Claw trimming routines in relation to herd size and housing. A survey in Swedish dairy herds. In: Ossent, P., Lischer, C.J. (Eds.), Proceedings of the 10th International Symposium on Lameness Ruminants, Lucerne, Switzerland, September 7±10, 1998, pp. 26±27. Kirchner, M., Boxberger, J., 1987. Loading of the claws and the consequences for the design of slatted floor. In: Wierenga, H.K., Peterse, D.J. (Eds.), Cattle Housing Systems, Lameness and Behaviour. Martinus Nijhoff, Dordrecht, pp. 37±44. Kossaibati, M.A., Esslemont, R.J., 1997. The costs of production diseases in dairy herds in England. Vet. J. 154, 41±51. Liang, K.Y., Zeger, S.L., 1986. Longitudinal data analysis using generalized linear models. Biometrika 73, 13±22. Maton, A., 1987. The influence of the housing system on claw disorders with dairy cows. In: Wierenga, H.K., Peterse, D.J. (Eds.), Cattle Housing Systems, Lameness and Behaviour. Martinus Nijhoff, Dordrecht, pp. 151±159. Murray, R.D., Downham, D.Y., Clarkson, M.J., Faull, W.B., Hughes, J.W., Manson, F.J., Merritt, J.B., Russell, W.B., Sutherst, J.E., Ward, W.R., 1996. Epidemiology of lameness in dairy cattle: description and analysis of foot lesions. Vet. Rec. 138, 586±591. Nilsson, S.A., 1963. Clinical, morphological and experimental studies of laminitis in cattle. Dissertation. Acta Vet. Scand. 4 (Suppl. 1). Nilsson, C., Svennerstedt, B., 2000. DraÈnerande gummigolv foÈr noÈtkreatur Ð utformning, djurbeteende och draÈneringsfoÈrmaÊga (Draining rubber floors for cattle Ð design, animal behaviour and draining capacity). Special Report 234. Dept. Agric. Biosyst. Technol., Swedish Univ. Agric. Sci., Alnarp, Sweden. Nilsson, C., Walberg, K., 1979. Gummilister Ð ett alternativ till staÊlgaller oÈver goÈdselraÈnnan? Orienterande undersoÈkning av skador paÊ mjoÈlkkor. Special Report 85. Dept. Agric. Engin., Swedish Univ. Agric. Sci., Lund, Sweden. Noordhuizen, J.P., 1998. Production diseases in dairy cattle: the veterinarian's role in disease control in the new millennium. In: Wensing, Th. (Ed.), Proceedings of the 10th International Conference on Production Diseases in Farm Animals, Utrecht, the Netherlands, August 24±28, 1998, pp. 1±9. Ossent, P., Lischer, C.J., 1998. Bovine laminitis: the lesions and their pathogenesis. Practice 20, 415±427. Peterse, D.J., 1980. De beoordeling van de runderklauw op basis van het optreden van zoollaesies (Judgement of bovine claws by the occurrence of sole lesions). Dissertation. Rijksuniversiteit, Utrecht, the Netherlands. RodrõÂguez Lainz, A., Hird, D.W., Carpenter, T.E., Read, D.H., Lainz, A.R., 1996. Case-control study of papillomatous digital dermatitis in southern California dairy farms. Prev. Vet. Med. 28, 117±131. SAS, 1997. SAS/STAT Software: Changes and Enhancements through Release 6.12. SAS Institute, Cary, NC. Scott, G.B., Kelly, M., 1989. Cattle cleanliness in different housing systems. Farm Build. Prog. 95, 21±24. Singh, S.S., Ward, W.R., Lautenbach, K., Hughes, J.W., Murray, R.D., 1993. Behaviour of first lactation and adult dairy cows while housed and at pasture and its relationship with sole lesions. Vet. Rec. 133, 469±474. Svennerstedt, B., Praks, O., 1997. UndersoÈkning av draÈneringsfoÈrmaÊga och ammoniakemission fraÊn draÈnerande golvsystem. Report 112. Dept. Agric. Biosyst. Technol., Swedish Univ. Agric. Sci., Alnarp, Sweden. Swedish Dairy Association, 1997. DjurhaÈlsovaÊrd 1996/1997. RedogoÈrelse foÈr husdjursorganisationens djurhaÈlsovaÊrd. Report. Eskilstuna, Sweden. Toussaint Raven, E., Haalstra, R.T., Peterse, D.J., 1985. Cattle Footcare and Claw Trimming. Farming Press, Ipswich, UK. Walker, R.L., Read, D.H., Loretz, K.J., Nordhausen, R.W., 1995. Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis. Vet. Microbiol. 47, 343±355.
Effects of a rubber-slatted ¯ooring system on cleanliness and foot health in tied dairy cows Jan Hultgren*, Christer Bergsten Department of Animal Environment and Health, Swedish University of Agricultural Sciences, P.O. Box 234, SE-532 23 Skara, Sweden Received 29 November 2000; accepted 16 May 2001
Abstract Effects on animal cleanliness and foot health of a new rubber-slat system for tied dairy cows, with the ability to drain faeces and urine, were studied in a 2-year controlled quasi-randomised trial in a Swedish university herd. Swedish Red and White cows were kept tied in 42 traditional longstalls with rubber mats. In total, 82 cows were observed. In 21 stalls, the rearmost 0.74 m of the solid stall ¯oor was replaced with nine rubber-coated 53 mm wide slats, divided by 29 mm slots. The cleanliness was assessed subjectively weekly (year 1) or bi-weekly (year 2) by observations of the hind part of the body. Claw measurements and foot health in hind feet were assessed in connection with hoof trimmings at the beginning, middle and end of the housing period. The foothealth recordings were blinded to ¯ooring. For the analysis of both cleanliness (1781 records, 73 cows) and foot health (240 records, 79 cows), logistic regression was applied, using marginal models and cow observations as repeated measures within each year. The risk of getting dirty on the rubber-slatted ¯oor was signi®cantly lower (odds ratio 0.12 for hind feet when short stall dividers were used, 0.39 for hind legs and 0.38 for thighs and udder), comparing with the solid stall ¯oor. The prevalence of foot diseases in hind feet at trimming was signi®cantly lower on the rubber slats (odds ratio 0.23 for dermatitis, 0.09 for heel horn erosion, and 0.34 for sole ulcer or sole or white line haemorrhage). # 2001 Elsevier Science B.V. All rights reserved. Keywords: Dairy cattle; Housing; Floor; Cleanliness; Digital dermatitis; Interdigital dermatitis; Heel horn erosion; Laminitis; Sole haemorrhage; Sole ulcer
1. Introduction Intensive milk production with high-yielding cows requires excellent housing, management and feeding to maintain proper hygiene and to avoid environmentally evoked diseases. Two of the most-common production diseases are foot and udder disorders. *
Corresponding author. Tel.: 46-511-67103; fax: 46-511-67134. E-mail address: [email protected] (J. Hultgren). 0167-5877/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 8 7 7 ( 0 1 ) 0 0 2 3 7 - 9
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With intensi®ed diets, larger herds and less labour spent on each cow, hygienic conditions are impaired and hygiene-related foot disorders are common during the housing season. Some of the most-prevalent contagious and hygiene-dependent foot diseases are interdigital and digital dermatitis, and heel horn erosion (Andersson and LundstroÈm, 1981; Murray et al., 1996; RodrõÂguez Lainz et al., 1996). In a recent study of Swedish dairy cows' hoof health, heel horn erosion was found in 67% and dermatitis in 30% of cows examined during the housing season (Manske, T., Swedish Univ. Agric. Sci., 2001, pers. commun.). Foot disorders are of great economical as well as animal welfare concern (Kossaibati and Esslemont, 1997; Noordhuizen, 1998; Broom, 1996). Dermatitis in the bovine foot may be caused by bacterial or viral infections, by parasitic infestations or by mechanical or chemical in¯uences. Both digital and interdigital dermatitis are in part due to poor ambient hygienic conditions (Walker et al., 1995; RodrõÂguez Lainz et al., 1996; Bergsten, 1997). Heel horn erosion is an irregular loss of bulb-horn tissue (Collick, 1997), which may be caused by poor ambient hygienic conditions. However, its principal cause is most likely dermatitis in the interdigital cleft or on the bulbs (Toussaint Raven et al., 1985). Laminitis is a non-infectious in¯ammation of the soft tissue of the claw, inside the horn capsule (Nilsson, 1963). Risk factors include a concentrated diet, trauma, overloading and infections (Ossent and Lischer, 1998). Previous cases of laminitis are seen at trimming as discolourations of the claw horn of the sole (Peterse, 1980). A sole ulcer is a defect in the sole horn, probably caused primarily by laminitis, poor horn quality and overloading of a limited area of the sole (Nilsson, 1963; Greenough, 1985; Ossent and Lischer, 1998). In Sweden, most cases of foot diseases are treated at routine hoof trimming, which is generally performed once or twice a year (Hultgren et al., 1998). Incidence estimates based on veterinary-treated cases alone probably depart greatly from true incidences. Based on observations of 2011 cows in 50 Swedish dairy herds at routine hoof trimming in the spring of 1996 and 1997, the prevalence of moderate or severe heel horn erosion was 46%, severe sole haemorrhage 15% and sole ulcer 14% (Bergsten et al., 1998), while the lactational incidence of veterinary-treated cases of all foot disorders during the same period was only 2.1% (Swedish Dairy Association, 1997). Because foot diseases generally last for most of the lactation or housing period (Andersson and LundstroÈm, 1981; Singh et al., 1993), prevalences at trimming should be fairly good estimates of the lactational (or yearly) incidences. In Sweden, dairy cows are housed except for 2±4 months of grazing from May to October, with approximately 80% of the animals kept tied in either short-stalls or longstalls. Loose housing has been recommended and tends to be used in newer dairy facilities Ð but in the near future, most Swedish dairy herds probably will remain tied. To keep short-stalls cleaner, feeding barriers have been developed that restrict the cow's space and thus increase the likelihood that she defecates in the gutter. An alternative way of improving hygienic conditions and animal comfort Ð without restricting the cows' movements Ð is to equip the stalls with a ¯ooring that drains faeces and urine. Mainly due to concerns about udder health and cow comfort, traditional concrete or wooden-slatted ¯oors have not been permitted for tied cows in Sweden. Rubber-coated slatted ¯ooring might, however, have less-adverse effects on animal health and comfort.
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Since the seventies, a type of rubber-slatted ¯ooring has been used in a Swedish beef herd of foster cows. It was a further development of that rubber-slat system that was tested in this study. Our objective was to evaluate the effects of a manure-draining rubber-slat system on hygiene and foot health in tied dairy cows. This was carried out as part of a pre-testing procedure for new housing equipment according to the Swedish statute on animal protection. Behavioural effects are reported elsewhere (Hultgren, 2001). 2. Material and methods 2.1. Animals and management system The study was carried out during two consecutive housing periods (1997±1999, years 1 and 2) in an experimental dairy herd of Swedish Red and White cows belonging to the Swedish University of Agricultural Sciences. The animals were tied in two rows of 21 long-stalls each, on either side of an aisle with mangers. Totally 82 cows were observed. Stall length was 2.20 m and mean stall width 1.19 m (range 1.11±1.23 m). The stall fronts had self-locking feeding barriers that were kept unlocked except during milking. Short (0.50 m) or long (0.85 m) stall dividers were placed between every second cow. In one of the rows (with 21 stalls), the rearmost 0.74 m of the solid ¯oor was replaced with a new type of slatted ¯ooring (Fritz Foderstyrning AB, NaÈssjoÈ, Sweden; Fig. 1). The slatted ¯oor had nine rubber-coated, 53 mm wide slats and the slots between them were 29 mm wide. The underlying manure gutter was cleaned with a similar scraping system to the rest of the building. During several housing periods preceding the study, all cows had been kept tied in ordinary solid-¯oored long-stalls with rubber mats. They were grazed from May to September. The cows calved in a separate maternity pen.
Fig. 1. Design of the rearmost part of the stall floor and manure gutter in stalls equipped with rubber-slatted flooring (mm).
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The anterior solid part of the stalls with rubber slats had ethyl-vinyl-acetate mats (Komfort, DeLaval AB, Tumba, Sweden) and each stall was bedded twice daily using approximately 1 kg of chopped straw (study week 1±17 during year 1) or 0.7 kg of wood shavings (the rest of the study) per day. The stalls with solid ¯oor had rubber mats (Gummimattan Marianne Larson AB, Gothemburg, Sweden) and received 3 kg of chopped straw per day given in the morning and afternoon. The herdsman was present in the building from 5:30 to 10 a.m. and from 1:30 to 5:30 p.m. The cows were fed concentrates individually ®ve times and silage four times daily from a computerised feeding wagon, according to production. All lactating cows were fed 2 kg hay manually twice daily; dry cows received additional straw. Water bowls were placed in the stalls between each cow. The cows were milked in their stalls twice daily. The herd average milk production during the 2-year period was 10,400 kg energy-corrected milk (ECM). The stall ¯oor was scraped clean of manure manually before and after milking and whenever the herdsman found it necessary. In November both years, all animals were sheared with an electric clipper on their hind parts, including the tails. Furthermore, all cows were groomed manually twice daily, after feeding and milking in the morning and before feeding and milking in the afternoon; the most contaminated body parts (hock, thigh, gaskin, and udder) were cleaned with an ordinary metal curry comb. The feet were not cleaned. In September (at the beginning of both housing periods), all cows were distributed between the two stall rows to achieve a strati®ed random allocation of treatments. This was done by listing the cows in order of parity and number of days in milk (or, in the case of heifers, days before expected calving). Every second cow on the list (random start by coin toss) was placed in a stall with rubber-slatted ¯oor. No cow changed group during the housing periods. Throughout the year, cows were culled and replaced by heifers in late pregnancy, all of which had been kept tied in long-stalls in another building. No culling was related directly to foot disorders. 2.2. Records of cleanliness Contamination of animals with manure was scored by the same person once a week during year 1 and once every second week in year 2. The observations were made in the morning, before grooming and milking, so the animals had been exposed to the different ¯oor types for at least 12 h without any cleaning measures. For practical reasons, the recordings were not blinded to ¯ooring. The extent of contamination with manure on the hind parts of the cows was assessed visually on a 4-level ordinal scale (Table 1). The recording system was developed by the authors for the speci®c purposes of this study, based on earlier experiences (Hultgren, 1999). Nine separate body divisions were rated: left and right hind foot (the dorsal part of the claws, the pastern and the dew claws), left and right hind leg (above the foot and including the hock area), left and right thigh (the gaskin, the thigh itself, the rump, and the areas around the ilial and ischial tuberosities), left and right side of the udder, and hind part of the udder (Fig. 2). Within each cow record, these scores were added in three groups, resulting in three sum scores, representing three principal body parts, referred to below as
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Table 1 Definition of different levels of scoring of cleanliness, dermatitis, heel horn erosion and sole lesions for dairy cows Trait
Score
Definition
Cleanliness
0 1
No or almost no contamination with manure One solitary large spot or several small spots of manure, together covering less than a fifth of the total area One solitary spot or several small spots of manure, together covering between one fifth and half of the total area More than half of the area covered by manure Skin of the foot intact Exudative or hyperkeratotic/proliferative dermatitis; erosions and(or) ulcerations Intact heel horn or superficial loss of heel horn (``pitting'') Marked fissures or craters No haemorrhage of the solar horn or only slight haemorrhagic discolouration of the horn (``paint brush'') Extensive and(or) distinct, more profound haemorrhage, not disappearing at slight trimming Intact sole horn Exposed corium on the solar surface
2 3 0 1
Dermatitis Heel horn erosion Sole/white line haemorrhage
0 1 0 1
Sole ulcer
0 1
foot, leg and body (thighs and udder). A total of 1781 cow-cleanliness records were obtained from 73 cows. 2.3. Records of claw measurements and foot diseases Claw measurements, hoof trimming and assessment of foot diseases were carried out in all animals at 3±4-month intervals; shortly after housing (September 26, year 1; October 22, year 2), half way into the housing period (January 22, year 1; February 17, year 2) and shortly before grazing (April 30, year 1; May 5, year 2). Claw measurements before
Fig. 2. Divisions of the hind part of the body for assessment of cleanliness.
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trimming included toe length (measured with vernier callipers) and lower toe angle (measured with a special angle meter at the distal 2 cm of the dorsal toe wall). Trimming and recording were carried out outside the cowshed, and the observer was not aware on which type of ¯ooring the examined cows were kept. In accordance with Bergsten (1995), severity of foot dermatitis heel horn erosion, haemorrhage of the sole, haemorrhage of the white line and sole ulcer were assessed in all hind feet on 2- or 4-level ordinal scales, which later were reduced to 2 levels (Table 1). The choice of cut-off points was based on a judgement of the clinical importance of the lesions. The presence of wart growth (papillomatous dermatitis), interdigital hyperplasia (®brous growth of the interdigital skin), white line separation (®ssure in the white line), double sole (two separate layers of sole horn), and abnormal claw shape (asymmetric or cork-screw claw) was noted. Similar recordings had been made during the housing period prior to the study (trimmings on February 7 and May 9, year 0). Three veterinary researchers were engaged in the recording, two of which recorded at only one occasion each (May of year 0 and 2). At each occasion, all recordings were made by the same veterinarian. Between trimmings, any of two veterinary researchers recorded all new cases of foot diseases. The intrarater reliability of the scoring system was assessed in a separate analysis using photographic slides and judged to be good, with averaged kappa coef®cients (for three raters) above 60% for heel horn erosion, haemorrhages of the sole and the white line, sole ulcer, dermatitis and white line separation (Manske, T., Swedish Univ. Agric. Sci., 2001, pers. commun.). A total of 330 cow foot health records were obtained from 82 cows. 2.4. Statistical analyses The effects of ¯ooring (FLOOR; 0: solid ¯oor; 1: rubber-slatted ¯oor) on cleanliness and foot health were analysed using the generalised estimating equations (GEE) approach (Liang and Zeger, 1986), the GENMOD procedure in SAS (SAS, 1997) and six logistic regression models, speci®ed further below. All models had the following general form: X g E Y a bm X m where g is the logit link function, E(Y) the expected values of the outcome variable Y, a the intercept and bm the regression coefficients for the included predictor variables Xm. Manure contamination on the three principal body parts was expressed by the binary outcome variables FOOT, LEG, and BODY. These were assigned a value of 1 for sum scores of at least 5, 4 and 6 (of maximum 6, 6 and 15), respectively, and a value of 0 for lower sum scores. The cut-off points were chosen before the analysis, based on the objective of the study and to achieve maximum relevance. Foot health was expressed by the three binary outcome variables DERM, HEEL, and SOLE. DERM and HEEL assumed a value of 1 for occurrence of dermatitis or heel horn erosion, respectively, in at least one of the hind feet. Similarly, SOLE received a value of 1 for occurrence of sole/white line haemorrhage or sole ulcer in at least one of the hind feet. For non-occurrence, the variables assumed a value of 0. All heifers (17 records) were excluded from the foot health data, to allow for a certain period of exposure before assessment of ¯oor effects.
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Study year was expressed by the class variable YEAR (1, 2). In the analysis of foot health, one additional level of YEAR (0) was introduced, representing the preceding housing period (1996±1997). Each record of a cow at a given occasion was regarded as an observation, resulting in repeated measures. The variable COW (eartag number), nested within YEAR, was included in the models as the subject effect (SAS, 1997). Thus, observations of a cow were assumed to be correlated only if they were from the same year (35 animals were present during only 1 year, 35 animals during 2 years and 12 animals during all 3 years). Recording occasion within YEAR was expressed by the class variable REP, entered into the models as the within-subject effect (SAS, 1997). In the case of cleanliness, REP contained the number of weeks since the beginning of housing 1; 2; 3; . . . ; 32, and in the analysis of foot health it represented trimming occasion (1, 2, 3). An exchangeable correlations structure was speci®ed (assuming all within-cow correlations between observations to be equal). The type of stall divider (on one side of each cow) was expressed by the dichotomous variable DIVIDER (0: short; 1: long). The type of bedding material was contained in the dichotomous variable LITTER (0: wood shavings; 1: straw). PARITY (1: ®rst parity; 2: second parity or older) was used to express age. The number of days in milk or, in heifers, the estimated number of days until calving (negative value) was expressed by the continuous variable DIM, which also was squared (SQ) to obtain DIMSQ. The individual milk yield was expressed by the continuous variable YIELD (kg ECM per day) and YIELDSQ. Yields on days of cleanliness and foot health recordings were calculated by interpolating between the yields at the two nearmost monthly routine milk recordings. For heifers and dry cows, YIELD was given a value of 0. In the analysis of foot health, the nominal variable VET (A, B, C) was used to identify the veterinary researcher who did the recording. The variation according to categorical explanatory variables in the cleanliness and foot health data is shown in Table 2. DIM median interquartile range for solid versus rubber-slatted ¯oors were 114 144 and 102 143 (cleanliness data), and 151 144 and 142 184 (foot health). YIELD median interquartile range for solid versus rubber-slatted ¯oors was 32:4 12:2 and 32:0 12:5 (cleanliness), and 34:0 12:0 and 34:3 10:7 (foot health). The correlation between independent variables was checked and the associations found were considered unlikely to cause any substantial multicollinearity r < 0:75. The models were formed by a manual backward stepwise procedure, starting with full models of main effects and excluding or re-entering one of them in each step. In the analysis of cleanliness, the independent variables FLOOR, YEAR, REP, DIVIDER, LITTER, PARITY, DIM, DIMSQ, YIELD and YIELDSQ were tested initially. In the analysis of foot health, the potential confounders YEAR, REP, VET, DIVIDER, LITTER, PARITY, DIM and YIELD were included with FLOOR in the full models. FLOOR was forced into all models and the criterion used for inclusion of other effects was a >15% change in the coef®cient estimate for FLOOR. Having selected main effects, ®rst-degree interaction terms with FLOOR were tested for inclusion, using a backward elimination procedure and a signi®cant likelihood-ratio test P 0:05 as the inclusion criterion. Odds ratios (OR) for FLOOR were calculated. In the analysis of cleanliness, all 1781 observations (101 cow-year clusters) were used. Interaction was found between FLOOR and DIVIDER. Therefore, the corresponding
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Table 2 Distribution of observations according to categorical explanatory variables in cows on solid and rubber slatted floor, in a study of cleanliness and foot health in 82 Swedish Red and White cows in 1997±1999 Variablea
Level
Cleanliness
Foot health
Solid floor n
%
Slatted floor
Solid floor
n
%
n
Slatted floor %
n
%
YEAR
0 1 2
± 605 292
± 67 33
± 594 290
± 67 33
79 63 63
39 31 31
0 62 63
0 50 50
DIVIDER
0 1
702 195
78 22
153 731
17 83
166 39
81 19
30 95
24 76
LITTER
0 1
0 897
0 100
613 271
69 31
0 330
0 100
83 42
66 34
PARITY
0 1 2
61 365 471
7 41 53
62 366 456
7 41 52
9 87 109
4 42 53
8 51 66
6 41 53
VET
A B C
± ± ±
± ± ±
± ± ±
± ± ±
144 40 21
70 20 10
104 0 21
83 0 17
a
For a detailed explanation of variables, see text.
model was constructed with FLOOR nested within DIVIDER. In the three models, 1349, 1091 and 837 observations, respectively, were cases response 1. The ®nal models were speci®ed as: FOOT FLOOR DIVIDER DIVIDER LITTER; LEG FLOOR DIVIDER LITTER; BODY FLOOR DIVIDER LITTER YIELD All autumn trimming records of foot health were omitted from the final analysis, because the foot status at these occasions was considered to reflect mainly the benefits of the grazing period. To check for differences between the two floor groups at the beginning of the housing period, FLOOR was replaced by a predictor with four levels REP 1 and FLOOR 0; REP 1 and FLOOR 1; REP > 1 and FLOOR 0; REP > 1 and FLOOR 1. There was no significant P > 0:15 difference between the two types of flooring at autumn trimming. Finally, FLOOR was used and the model selection procedure was repeated. In total, 240 observations (79 cows, 125 cow-year clusters) were used. In the three models, 49, 80 and 75 observations, respectively, were cases. The three final models were specified as follows: DERM FLOOR YEAR VET; HEEL FLOOR YEAR; SOLE FLOOR YEAR DIVIDER LITTER The associations between foot health at trimming (DERM, HEEL and SOLE) and cleanliness at all recordings since the previous trimming (means of FOOT, LEG and
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BODY) were assessed by a correlation analysis on all observations at the third trimming of years 1 and 2 (83 observations). To indicate stall cleanliness and support the interpretation of results regarding foot lesions, a piece of sole horn from 13 randomly selected cows, among which seven were kept on rubber slats, was analysed for dry-matter content at each of the three trimming occasions during year 1. The means for the two ¯oor groups were compared using Student's t-test. 3. Results 3.1. Cleanliness When compared to the solid ¯oor, the rubber-slatted ¯oor was associated with signi®cantly lower odds of manure contamination on foot when short stall dividers were used, and on leg and body with either type of stall divider (Table 3). With long stall dividers, there was only a tendency for reduced odds of manure contamination on foot. Generally, there were only small differences in cleanliness between recording. Based on the chosen cut-off points for response variables, the overall percentages of cows considered to be dirty on foot, leg and body on solid and rubber slatted ¯oors were 91 and 61, 80 and 43, and 59 and 35%, respectively. The cleanliness models ®t the data relatively well, as judged by the ratios of the deviances to their degrees of freedom (0.90, 1.15 and 1.25, respectively). A comparison between observed and expected percentages of cases in each stratum of discrete covariates (FLOOR, DIVIDER and LITTER) revealed only small-to-moderate differences. In the three models, the correlation between two observations of a given cow was estimated to be 0.23, 0.34 and 0.30, respectively. 3.2. Foot health Generally, foot disorders were much less common at the autumn trimming (shortly after the start of housing) than at the two trimmings in the spring, while the differences between Table 3 Effect of rubber-slatted versus solid flooring on contamination with manure on hind feet (FOOT), hind legs (LEG), and thighs and udder (BODY) in a study of 73 Swedish Red and White cows in 1997±1999; three logistic regression models using 1781 observations Outcomea
Effect in model
Stall divider
FOOT
FLOOR (DIVIDER) FLOOR (DIVIDER) FLOOR FLOOR
Shortb Longc ± ±
LEG BODY a
b 2.14 0.68 0.94 0.96
For a detailed explanation of traits and models, see text. Using long stall divider as base level. c Using short stall divider as base level. b
S.E. (b)
P
OR
95% CI for OR
0.53 0.53 0.43 0.39
<0.001 0.20 0.03 0.01
0.12 0.50 0.39 0.38
0.04, 0.18, 0.17, 0.18,
0.33 1.43 0.91 0.82
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Table 4 Mean prevalences (%) of recorded foot diseases at hoof trimming in January±February and April±May years 0, 1 and 2, in cows on solid and rubber slatted floora; Swedish Red and White cows 1997±1999 Disease
Dermatitis Heel horn erosion Sole or white line haemorrhage Sole ulcer White line separation Double sole Abnormal claw shape a
Year 0, solid floor n 79
Year 1
Year 2
Solid floor n 42
Slatted floor Solid floor n 41 n 42
Slatted floor n 42
29 59 33 8 13 0 0
36 38 36 2 12 0 0
7 0 49 0 15 0 2
7 10 12 0 12 2 5
17 33 17 7 21 2 0
For a detailed explanation of diseases and groups, see text.
the latter were smaller. Table 4 shows the mean prevalences of all recorded foot disorders at the two spring trimming occasions during years 0, 1 and 2 in the two ¯oor groups. The dynamics (year and repetition) of the prevalences of dermatitis, heel horn erosion and sole lesions in the two ¯oor groups is presented in Fig. 3. No cases of wart growth or interdigital hyperplasia were found. Table 5 shows the models of foot health. When compared to solid ¯oors, the rubber-slatted ¯ooring was associated with signi®cantly lowered odds of dermatitis and heel horn erosion. There was also some indication of a reduced risk of sole lesions. The foot-health models ®t the data relatively well (ratios of the deviances to its degrees of freedom were 0.91, 1.03 and 1.18, respectively). Comparing observed and expected percentages of cases in each stratum of discrete covariates (FLOOR, YEAR, VET, DIVIDER, and LITTER), only small to moderate differences were found. For the three outcomes, the correlation between two observations of a given cow was estimated to be 0.07, 0.16 and 0.05, respectively. In the group of cows on solid ¯oor, four incidents of lameness were recorded and treated between regular trimmings. These were diagnosed as one case of sole haemorrhage, one of sole ulcer and two of white line separation. Only one case of lameness due to sole haemorrhage was treated in the group of cows on rubber slats. The overall mean (and S.D.) of toe length and lower toe angle before trimming in cows on solid and rubber slatted ¯oor were 85 mm (6.7 mm), 82 mm (7.0 mm), 428 (6.08) and 408 (6.48), respectively. There were only small variations between trimming occasions. Dry-matter content of claw horn mean S:D: at the three trimmings year 1 was 71 4:9%; 72 4:7% and 69 4:9% on slatted ¯oor, and 67 2:2%; 68 5:2% and 62 3:2% on solid ¯oor t24 2:46; P 0:02. The correlation between foot health and cleanliness was low to moderate (Table 6). Signi®cant Pearson correlation coef®cients were found between HEEL and FOOT, HEEL and LEG, HEEL and BODY, and SOLE and FOOT. The three cleanliness outcomes were fairly strongly correlated with each other, and there was also correlation between DERM and HEEL.
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Fig. 3. Prevalences of dermatitis, heel horn erosion and sole lesions (haemorrhage or ulcer) in cows on solid (Ð) and rubber slatted (- - -) floor at hoof trimmings 1±3 of years 0±2 in a study of Swedish Red and White cows in 1997±1999; in each floor group, n 39 40 year 1 and n 17 21 years 2±3. Table 5 Effect of rubber-slatted versus solid flooring on foot dermatitis (DERM), heel horn erosion (HEEL), and sole lesions (SOLE) in 79 Swedish Red and White cows in 1997±1999; three logistic regression models using 240 observations Outcomea
Effect in model
DERM HEEL SOLE
FLOOR FLOOR FLOOR
a
b 1.48 2.41 1.09
S.E. (b)
P
OR
95% CI for OR
0.50 0.55 0.63
0.003 <0.001 0.08
0.23 0.09 0.34
0.08, 0.61 0.03, 0.27 0.10, 1.16
For a detailed explanation of traits and models, see text.
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Table 6 Correlation between outcomes for foot health at hoof trimming (April of year 1 and May of year 2) and mean cleanliness since previous trimminga in a study of Swedish Red and White cows in 1997±1999 (Pearson correlation coefficients at upper right and corresponding significance levels at lower left); n 83
DERM HEEL SOLE FOOT LEG BODY a
DERM
HEEL
SOLE
FOOT
LEG
± 0.05 0.13 0.09 0.11 0.68
0.22 ± 0.70 <0.001 <0.001 0.002
0.16 0.04 ± 0.001 0.86 0.82
0.19 0.38 0.36 ± <0.001 <0.001
0.18 0.42 0.02 0.64 ± <0.001
BODY 0.05 0.33 0.03 0.42 0.53 ±
For a detailed explanation of traits, see text.
4. Discussion The risk of getting dirty on the rubber-slatted ¯oor was lower, when compared to a solid stall ¯oor, and the prevalence of foot diseases in hind feet at trimming was lower on the slatted ¯oor. Health effects of manure-draining rubber slats as part of the tie-stall ¯oor have not been studied in full scale before. Nilsson and Walberg (1979) studied gratings with a surface of rubber instead of steel, and found no differences in the occurrence of leg injuries. Nilsson and Svennerstedt (2000) tested a rubber-slatted ¯oor system (similar to that we used); the ¯ooring did not seem to change the cows' resting behaviour. In loose-housing facilities, insuf®ciently drained and scraped alleys increase the risk of heel horn erosion and the need for veterinary treatment of other foot disorders, when compared to concrete-slatted ¯ooring (Coehen, 1980; Buchwald et al., 1982; Maton, 1987). On the other hand, badly designed concrete slats in loose-housing result in hoof and leg trauma (Kirchner and Boxberger, 1987). Good drainage promotes a dry ¯oor surface with a lower risk of slipping (Svennerstedt and Praks, 1997) Ð the slats must be wide enough to give suf®cient support for the hooves (Kirchner and Boxberger, 1987). Bedding material generally decreases the draining capacity (Nilsson and Svennerstedt, 2000). After the ®rst months of the present study, wood shavings were used instead of chopped straw (on both types of ¯ooring), because the straw clogged the slots. This in¯uenced cleanliness, too, and a variable indicating litter material was included as a confounder in the multivariable models. All recordings of cleanliness were carried out by the same person, which probably reduced variation. For practical reasons, the recording was not blinded. In the case of foot health, the recording was blinded to ¯ooring, but the data were not balanced with respect to two of the observers. A variable for ``recording veterinarian'' was, however, considered in the foot health models, and the risk of systematic differences in assessment of cleanliness or foot lesions between the two types of ¯ooring was considered small and of no practical importance. Cleanliness scoring systems for loose-housed cattle have been described by, e.g. Scott and Kelly (1989), but were not considered completely appropriate for tied dairy cows. The
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tails were not included in the study, since their cleanliness is mainly in¯uenced by the condition of the gutter, rather than the type of stall ¯oor. Both the cleanliness and foot health data were longitudinal, with repeated measures of individual cows over time resulting in correlated observations. By using the GEE approach, the covariance, standard error and signi®cance-level estimates were adjusted accordingly, and the correlation matrices were computed separately. The within-cow (and within-year) correlation was moderate in the cleanliness analysis, which indicates that some cows were more or less constantly clean Ð while others were constantly dirty (which we feel is a common experience among farmers). In the case of foot health, the within-cow correlation was lower. On foot, the effect of ¯ooring on cleanliness was clear only when short stall dividers were used. This may have been due to long dividers not allowing the cows to move much to the side Ð thus keeping the stalls cleaner and making the slatted ¯ooring less necessary. A variable for stall divider acted as a confounder in all three cleanliness models. However, no signi®cant interaction between ¯ooring type and stall divider type was found in the analyses of cleanliness on leg or body. There is no reason to believe that the two types of ¯ooring should differ with respect to claw horn growth or wear, because both had a rubber surface. The claw measurements did not differ much between the ¯oor groups. When compared to a bare concrete tie-stall ¯oor, rubber mats result in longer toes (Bergsten et al., 1998). We believe the improved foot health on the rubber-slatted ¯oor to be mainly, if not only, an indirect effect of the improved hygienic conditions on the rubber slats. The differences in prevalence of dermatitis and heel horn erosion between the two types of ¯ooring increased distinctly during the housing period, most clearly seen in year 1, in accordance with earlier studies (Andersson and LundstroÈm, 1981; Bergsten and Pettersson, 1992). No strong correlation was found between foot diseases at trimmings in April and May and preceding cleanliness, but the signi®cant relationships agree well with earlier ®ndings that heel horn erosion is associated with poor hygiene. In this study, there was a tendency for a reduced overall prevalence of sole lesions in cows on rubber slats, although both stall types were equipped with mats. It is possible that this reduction was secondary to lower prevalences of dermatitis and heel horn erosion (and thus, superior claw horn quality) Ð but it also might have been due to a slightly softer rubber on the slatted ¯oor. The models ®t the data well. However (as judged by the ratio of deviance to d.f.), there was overdispersion in the data on cleanliness on body. This might be explained by the fact that adjacent animals may become dirty (especially on the thighs and back) from contact with the manure of the neighbouring cow. Alternatively, correlated observations from different years may have caused some clustering at the cow level. Similarly, there was some indication of overdispersion in the data on sole lesions, possibly re¯ecting clustering due to production factors, e.g. milk yield or diet, or slightly correlated observations within cows and between years. The higher dry-matter content of the claw horn found in cows on rubber-slatted ¯oor, and the apparent increasing difference between the two ¯ooring types during the housing period, support cleanliness and foot health ®ndings. Bergsten and Pettersson (1992) were able to show a higher dry-matter content in claw horn from cleaner tie-stalls and
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furthermore a negative correlation between dry-matter content and the presence of heel horn erosion. In this experiment, the rubber-slat system was used in traditional Swedish long-stalls. We believe the effects on cleanliness and foot health would be similar in short-stalls. However, if the stalls are kept relatively clean by other means, the effect of the rubber slats would probably diminish (as was seen in the analysis of cleanliness on hind feet, where there was a signi®cant interaction between the type of stall divider and the ¯ooring). It is not possible to conclude from this study the optimum design of the rubber-slatted ¯ooring (width of slats and slots, percentage of the stall length covered by slats, etc.) or the effects on, e.g. udder health. Available data from the experimental herd, however, do not indicate any such effects (Hultgren, 1999). 5. Conclusions We conclude that the tested rubber-slat system substantially improved the cleanliness of the hind part of tied dairy cows, and reduced the prevalences of foot dermatitis, heel horn erosion and sole lesions (ulcer or haemorrhage) at routine hoof trimming. Acknowledgements The study was carried out with ®nancial support from the Swedish Board of Agriculture, È ST and the Foundation for technology transfer in Gothemburg. We also acknowlAGROVA edge Thomas Manske for foot health recordings, Rune Karlsson and Gunnar Fritz for creative co-operation, and Linda Keeling for assisting with the English. References Andersson, L., LundstroÈm, K., 1981. The influence of breed, age, body weight and season on digital diseases and hoof size in dairy cows. Zbl. Vet. Med. A 28, 141±151. Bergsten, C., 1995. Digital disorders in dairy cattle with special reference to laminitis and heel horn erosion: the influence of housing, management and nutrition. Dissertation. Swedish University of Agriculture Science, Skara, Sweden. Bergsten, C., 1997. Infectious diseases of the digits. In: Greenough, P.R. (Ed.), Lameness in Cattle, 3rd Edition. Saunders, Philadelphia, PA, pp. 89±100. Bergsten, C., Pettersson, B., 1992. The cleanliness of cows tied in stalls and the health of their hooves as influenced by the use of electric trainers. Prev. Vet. Med. 13, 229±238. Bergsten, C., Hultgren, J., Manske, T., 1998. Claw traits and foot lesions in Swedish dairy cows in relation to trimming interval and housing system. A preliminary report. In: Ossent, P., Lischer, C.J. (Eds.), Proceedings of the 10th International Symposium on Lameness Ruminants, Lucerne, Switzerland, September 7±10, 1998, pp. 46±48. Broom, D.M., 1996. Animal welfare defined in terms of attempts to cope with the environment. Acta Agric. Scand. A (Suppl. 27), 22±28. Buchwald, E., Blom, J.Y., Smedegaard, H.H., Thysen, I., 1982. Klovsundhedens afhñngighed af gulvtype og lejetype. In: éstergaard, V., Hindhede, J. (Eds.), 532 Beretning fra Statens Husdyrbrugsforsùg. Report. Copenhagen, pp. 109±119.
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Coehen, J., 1980. Mehr Augenmerk den Klauen schenken. DLG-Mitteilungen 95, 1270±1272. Collick, D.W., 1997. Heel horn erosion. In: Greenough, P.R. (Ed.), Lameness in Cattle, 3rd Edition. Saunders, Philadelphia, PA, pp. 116±118. Greenough, P.R., 1985. The subclinical laminitis syndrome. Bovine Pract. 20, 144±149. Hultgren, J., 1999. Gummispaltgolv foÈr bundna kor och ungdjur. Provning av ny teknik enligt DjurskyddsfoÈrordningen (Rubber-slatted flooring for tied cows and young cattle. Testing of new technical equipment according to the Swedish statute on animal protection). Special Report 9. Dept. Anim. Environ. Health, Swedish Univ. Agric. Sci., Skara, Sweden. Hultgren, J., 2001. Effects of two stall flooring systems on the behaviour of tied dairy cows. Appl. Anim. Behav. Sci. 73, 167±177. Hultgren, J., Bergsten, C., Manske, T., 1998. Claw trimming routines in relation to herd size and housing. A survey in Swedish dairy herds. In: Ossent, P., Lischer, C.J. (Eds.), Proceedings of the 10th International Symposium on Lameness Ruminants, Lucerne, Switzerland, September 7±10, 1998, pp. 26±27. Kirchner, M., Boxberger, J., 1987. Loading of the claws and the consequences for the design of slatted floor. In: Wierenga, H.K., Peterse, D.J. (Eds.), Cattle Housing Systems, Lameness and Behaviour. Martinus Nijhoff, Dordrecht, pp. 37±44. Kossaibati, M.A., Esslemont, R.J., 1997. The costs of production diseases in dairy herds in England. Vet. J. 154, 41±51. Liang, K.Y., Zeger, S.L., 1986. Longitudinal data analysis using generalized linear models. Biometrika 73, 13±22. Maton, A., 1987. The influence of the housing system on claw disorders with dairy cows. In: Wierenga, H.K., Peterse, D.J. (Eds.), Cattle Housing Systems, Lameness and Behaviour. Martinus Nijhoff, Dordrecht, pp. 151±159. Murray, R.D., Downham, D.Y., Clarkson, M.J., Faull, W.B., Hughes, J.W., Manson, F.J., Merritt, J.B., Russell, W.B., Sutherst, J.E., Ward, W.R., 1996. Epidemiology of lameness in dairy cattle: description and analysis of foot lesions. Vet. Rec. 138, 586±591. Nilsson, S.A., 1963. Clinical, morphological and experimental studies of laminitis in cattle. Dissertation. Acta Vet. Scand. 4 (Suppl. 1). Nilsson, C., Svennerstedt, B., 2000. DraÈnerande gummigolv foÈr noÈtkreatur Ð utformning, djurbeteende och draÈneringsfoÈrmaÊga (Draining rubber floors for cattle Ð design, animal behaviour and draining capacity). Special Report 234. Dept. Agric. Biosyst. Technol., Swedish Univ. Agric. Sci., Alnarp, Sweden. Nilsson, C., Walberg, K., 1979. Gummilister Ð ett alternativ till staÊlgaller oÈver goÈdselraÈnnan? Orienterande undersoÈkning av skador paÊ mjoÈlkkor. Special Report 85. Dept. Agric. Engin., Swedish Univ. Agric. Sci., Lund, Sweden. Noordhuizen, J.P., 1998. Production diseases in dairy cattle: the veterinarian's role in disease control in the new millennium. In: Wensing, Th. (Ed.), Proceedings of the 10th International Conference on Production Diseases in Farm Animals, Utrecht, the Netherlands, August 24±28, 1998, pp. 1±9. Ossent, P., Lischer, C.J., 1998. Bovine laminitis: the lesions and their pathogenesis. Practice 20, 415±427. Peterse, D.J., 1980. De beoordeling van de runderklauw op basis van het optreden van zoollaesies (Judgement of bovine claws by the occurrence of sole lesions). Dissertation. Rijksuniversiteit, Utrecht, the Netherlands. RodrõÂguez Lainz, A., Hird, D.W., Carpenter, T.E., Read, D.H., Lainz, A.R., 1996. Case-control study of papillomatous digital dermatitis in southern California dairy farms. Prev. Vet. Med. 28, 117±131. SAS, 1997. SAS/STAT Software: Changes and Enhancements through Release 6.12. SAS Institute, Cary, NC. Scott, G.B., Kelly, M., 1989. Cattle cleanliness in different housing systems. Farm Build. Prog. 95, 21±24. Singh, S.S., Ward, W.R., Lautenbach, K., Hughes, J.W., Murray, R.D., 1993. Behaviour of first lactation and adult dairy cows while housed and at pasture and its relationship with sole lesions. Vet. Rec. 133, 469±474. Svennerstedt, B., Praks, O., 1997. UndersoÈkning av draÈneringsfoÈrmaÊga och ammoniakemission fraÊn draÈnerande golvsystem. Report 112. Dept. Agric. Biosyst. Technol., Swedish Univ. Agric. Sci., Alnarp, Sweden. Swedish Dairy Association, 1997. DjurhaÈlsovaÊrd 1996/1997. RedogoÈrelse foÈr husdjursorganisationens djurhaÈlsovaÊrd. Report. Eskilstuna, Sweden. Toussaint Raven, E., Haalstra, R.T., Peterse, D.J., 1985. Cattle Footcare and Claw Trimming. Farming Press, Ipswich, UK. Walker, R.L., Read, D.H., Loretz, K.J., Nordhausen, R.W., 1995. Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis. Vet. Microbiol. 47, 343±355.