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Dairy-heifer management in the Netherlands
Preventive Veterinary Medicine 46 (2000) 197±208
Dairy-heifer management in the Netherlands M.C.M. Mouritsa,*, H.J. Van der Fels-Klerxa, R.B.M. Huirnea, M.W.C. Huybenb a
Department of Economics and Management, Farm Management Group, Wageningen University, Hollandseweg 1, 6706 KN Wageningen, The Netherlands b Animal Health Service, PO Box 9, 7400 AA Deventer, The Netherlands Received 14 July 1999; accepted 3 May 2000
Abstract The objective of this study was to describe the Dutch rearing performance of dairy heifers by the evaluation of performance indices at weaning, breeding and calving. The second objective was to determine the extent to which dairy farmers use pre-set rearing targets and data monitoring for the evaluation of their rearing results. A questionnaire was sent to 3000 randomly chosen dairy cattle farmers to survey their heifer-rearing practices. Almost a third of the farmers (n959) completed and returned the questionnaire. Of the farms responding, 29% realised an age at first calving of 24 months, 51% from 25 to 27 months, and 20% of 27 months. The farmers indicated that the average body weight after calving was within the range 525±550 kg. Average wither height class was 141±145 cm. Most farmers estimated the body-condition score of their heifers at calving to be 3±3.5. In 29% of the cases, weaning occurred at an age of 8 weeks, 35% at 9±10 weeks of age and 36% at 11 weeks of age. Most farmers (81%) commenced breeding at an age of 15 months. Intermediate evaluation of the rearing policy by means of performance goals and measurements was limited, and many of the reported performance indices on age and body weight were outside the range of the recommended target values. These results indicated that the common Dutch heiferrearing management system could be improved considerably. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Dairy cattle-management; Rearing practices; Questionnaire
1. Introduction In the Netherlands, an average of 25±35% of the dairy herd is culled each year (Dutch Cattle Syndicate, 1998) and has to be replaced. This makes replacement rearing an essential part of dairy farm management. *
Corresponding author. Tel.: 31-317-484065; fax: 31-317-482745. E-mail address: [email protected] (M.C.M. Mourits) 0167-5877/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 8 7 7 ( 0 0 ) 0 0 1 4 6 - X
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A dairy farmer controls his or her rearing unit by the determination of a nutritional plan of growth and a breeding schedule. The ultimate goal of replacement rearing is to reach first-calving age at a predetermined time with an optimal growth rate (Quigley III et al., 1996b; Mourits et al., 1997). To guide optimal development and to identify deviations from pre-set rearing targets at an early stage, heifers must be monitored throughout the rearing period. Essential tools in the management of replacement heifer rearing are, therefore, record keeping, data monitoring and evaluation (Quigley III et al., 1996b). Unfortunately, as a component of the management system, rearing of dairy replacements is often overlooked (Mourits et al., 1997). Many dairy farmers consider the rearing period as a non-productive period which requires little attention. A better understanding of the most-limiting areas in heifer management might enhance the efforts of farm advisors in providing practical recommendations. The costs of raising dairy replacements depend to a large extent on the age at first calving. Reducing the age at first calving offers advantages such as lower overhead costs, decreased feed costs, decreased overcrowding and increased production per day of herd life (Hoffman and Funk, 1992; Mourits et al., 1997). In the Netherlands, average age at first calving is 26 months (Dutch Cattle Syndicate, 1998), despite the general recommendation of a calving age of 24 months (Hoffman and Funk, 1992; Mourits et al., 1997). However, the economic efficiency of a rearing strategy cannot be measured solely by the age at first calving (Mourits et al., 1997). Performance indices (such as body weight (BW), average daily gain, and body-condition score (BCS)) are also needed to evaluate the physiological development of the heifer. However, insight into these performance indices is lacking. The objective of this study was to describe the dairy heifer-rearing practices in the Netherlands by means of a large field survey. In particular, performance indices at weaning, breeding and calving were used to reflect the Dutch rearing performances. The second objective was to determine the extent to which dairy farmers evaluate their own rearing policies by means of pre-set rearing targets and data monitoring. 2. Materials and methods A self-administered questionnaire (Appendix A) was designed to collect the information on the Dutch heifer-rearing practices. The areas of importance were derived from an extensive literature review on heifer rearing and covered rearing goals, feeding, housing, health, reproductive management, and calving practices. The questionnaire also contained questions related to characteristics of the farm. A draft questionnaire was pretested on 10 dairy farms. Results and feedback received from this pre-test were used to fine-tune the questionnaire. The final version consisted of eight parts with 61 questions. The type of questions were open-ended (n19), semi-closed (n25) as well as closed (n17). Three thousand dairy farmers (approximately 10% of the dairy farmers in the Netherlands; Silvis and Van Bruchem, 1998) were approached with the questionnaire by mail. The farmers were selected at random (lottery mechanism) from the mailing list of
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the Dutch Animal Health Service. This mailing list covers all dairy farmers in the Netherlands. The questionnaires were sent to the farmers in November 1998. Each survey was accompanied by a cover letter explaining the purpose and scope of the study and asking for participation. To encourage participation, the cover letter pointed out that the results would help the Animal Health Service to provide high-quality advice on dairy-heifer rearing. It was stressed that all information collected would be kept strictly confidential, and that only summary results, without any personal identification, would be published. The farmers were asked to respond within 5 weeks. Three weeks after the first mailing, a reminder was sent to encourage the participation of farmers who had not responded until that time. Data transformations, descriptive analyses and hypothesis tests were performed using the statistical program SPSS 7.5 (Norusis, 1993). The Kruskal±Wallis test was used to test for differences among breeds. The Mann±Whitney test and Kolgomorov±Smirnov test were used to test whether farmers who considered target values for calving age or calving weight realised, respectively, lower calving ages (continuous variable) or heavier calving weights (categorical variable), than farmers who did not considered pre-set target values. In this paper, the emphasis is on the general aspects of dairy replacement management, depicted by weaning, breeding and calving characteristics. Aspects concerning housing and health management will be discussed in a separate paper. 3. Results 3.1. General herd characteristics Within the defined response period of 5 weeks, 959 farmers (32%) completed and returned the questionnaire. Table 1 shows the average farm characteristics of the respondents along with the average farm characteristics of the total population of Dutch dairy farms. Table 2 shows the relative distribution of the main characteristics of both, the farms within the survey and the total population. The distribution of surveyed herd sizes was comparable with the distribution of herd size within the complete population (Table 2). The distributions on farm intensity demonstrated that intensive farms were rather under-represented within the survey. The distributions of milk production on the surveyed farms and on the farms in the complete population were comparable, although in the survey the percentage of farms with extremely low or high production values was lower than in the total population of dairy farms (Table 2). Based on the correspondence in the average values of the general farm characteristics (Table 1) and the relative distributions of three main characteristics (Table 2), we consider the farms within the survey to be representative for the total population. Relative distribution of respondents per region corresponded with the relative distribution of dairy farms per region. The ranges within the characteristics of the surveyed farms demonstrate the large variation among dairy farms. Among the respondents there were two farmers who were specialised in heifer rearing (explaining the zero within the range of dairy herd size and
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Table 1 Farm characteristics of the Dutch dairy farm population (N30 400) and the dairy farms surveyed (n959) in 1998 Farm characteristic
Dutch population mean
Survey Minimum
Herd size Dairy cows Young stock>1 year Young stock1 year
52a 24b 17b
Grass and arable land (ha)
32.0a ÿ1
Intensity (livestock unit ha )
2.1
305-Day milk production (kg)
d
c
Maximum
0 0 0
56 22 22
301 160 255
2
33.4
164
0.6
7733
Mean
3300
2.2 7769
7.4 10973
a
Silvis and Van Bruchem (1998). Statistics Netherlands (1997). c Derived from Silvis and Van Bruchem (1998) and Statistics Netherlands (1997). d Dutch Cattle Syndicate (1998). b
Table 2 Relative distribution of the Dutch dairy farm population (N30 400) and the dairy farms surveyed (n959) on dairy herd size, intensity and average milk production per lactation, 1998 Farm characteristic
Level
Population (%)a
Survey (%)
Dairy herd size
20 21±40 41±60 61±80 81±100 101±150 151
7.6 26.7 34.9 18.7 7.2 4.2 0.8
6.9 22.7 35.7 21.2 8.7 4.1 0.7
Intensity (livestock unit haÿ1)
<1 1±2 2±3 3±4 4±5 5±6 6
0.8 30.9 46.3 11.2 4.6 2.5 3.7
0.8 38.0 53.7 6.3 0.8 0.3 0.1
Milk production (kg)
<5800 5800±6600 6600±7400 7400±8200 8200±9000 9000±9800 9000
4.5 9.2 17.8 24.8 23.5 13.5 6.6
3.5 8.3 20.5 33.9 22.1 9.6 2.1
a
Based on Statistics Netherlands (1997) and Dutch Cattle Syndicate (1998).
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Table 3 Distribution of average milk production and calving age by breed based on results of a survey among 959 Dutch dairy farms, 1998 Breed
Holstein MRYb Red Holstein Friesian Holstein Otherc
na
627 141 105 33 12
305-day milk production (kg) percentiles
Calving age (month) percentiles
a
n
25th
50th
75th
na
25th
50th
75th
610 120 102 28 9
7500 6000 7120 6525 5385
8000 6860 7500 7535 6100
8600 7330 8000 8030 7800
603 129 99 27 12
24 25 25 24 24
25 26 26 26 25
26 28 27 26 28
a
Completeness of questionnaire differed per subject. Meuse Rhine and Yssel. c Other breeds: Blister Head, Jersey, Monte Beliarde, Brown Swiss. b
the large numbers within the range of number of young stock). Furthermore, there were six farms without any young stock younger than 1 year and five farms without any young stock older than 1 year (Table 1). The primary breed of dairy cattle (Table 3) was Holstein. The median 305-day herd production differed significantly among breeds (Kruskal±Wallis, w2187.5, d.f.4, P<0.01). 3.2. First calving In general, the distribution of calving age is skewed toward older heifers. To prevent an indistinct definition of the average first-calving age, the farmers were explicitly asked for the age at which the plurality of the heifers gave birth (mode). Of the farms surveyed, 29% had a mode value for first-calving age of 24 months, 51% from 25 to 27 months, and 20% of >27 months (Fig. 1). Eighty percent of the farmers (n768) indicated that they aimed for a specified target age at first calving. Of these farmers, more than 50% strove for the recommended target
Fig. 1. Distribution of herd-specific first-calving age on 959 Dutch dairy farms based on the realised calving age of most of the dairy heifers (realised), and the farmer-indicated target values of age at first calving (target) (1998).
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Fig. 2. Distribution of herd-specific postcalving weight classes on 959 Dutch dairy farms based on the most frequently observed weight classes after calving (realised), and the farmer-indicated target values of BW after calving (target) (1998).
age of 24 months, while 24% aimed for a calving age of 26 months or more (Fig. 1). The farmers who considered a target calving age realised a lower calving age (median25 months), than the farmers who did not consider a pre-set target age (median26 months). This inequality between the two subsets of farmers was significant (Mann±Whitney, U49 631, P<0.01). Subdividing age at first calving by breed (Table 3) showed a tendency towards a lower calving age for the typical dairy breeds Holstein and Friesian Holstein and a higher calving age for the so-called ``double purpose'' breed (MRY) (Kruskal±Wallis, w235.0, d.f.4, P<0.01). Only 1.4% of the farmers actually weighed the heifers after calving; most farmers gave an estimation of BW after calving (Fig. 2). The small interest in calving weight is also revealed in that 57% of the farmers did not aim for a pre-set target value. Within the subset of farmers that considered a target value, 50.3% indicated a target value for BW after calving of >550 kg (Fig. 2). Farmers who considered pre-set target values for calving weight realised heavier calving weights than farmers who did not (Kolmogorov± Smirnov, D0.083, P<0.05). A small majority (55.8%) of the surveyed farmers measured the wither height of the heifers after calving. Of these farmers, 55.5% reported an average wither height within the range 141±145 cm. Prior to calving, 72% of the farmers kept an eye on the BCS of the heifer; however, only 1% actually monitored BCS. On an annual basis, 31.6% of the dairy cows were replaced by heifers. However, 18.6% of these dairy replacements were replaced again during their first lactation. The main reasons of this early replacement were fertility problems (32% of the cases), insufficient milk production (29%), udder problems (17%), sale (10%) and foot problems (5%). 3.3. Weaning period Of the heifer calves born, 77.7% were retained to be reared as replacements. After the colostral period, mastitic or antibiotic milk (37.1%), milk replacer (34.3%) and whole milk (28.6%) were the types of liquids most often fed. Free water intake is essential for
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Table 4 Decision criteria for weaning and first breeding of dairy heifers (959 Dutch dairy farms, 1998)
Weaning Age at weaning (weeks) Concentrates intake at weaning (kg per day) BW at weaning (kg) Other First breeding Age at first breeding (month) Wither height at first breeding (cm) BW at first breeding (kg) Season Other
Decisive factor percentage of total respondentsa
Values percentile
89.3 33.4
na
25th
50th
75th
75 121
8 1
10 1
12 2
16.8 3.5
88 ±
65 ±
78 ±
99 ±
94.6 26.6 17.4 22.0 2.2
774 30 47 ± ±
15 125 325 ± ±
15 130 350 ± ±
16 135 387 ± ±
a The number of farmers that indicated to consider a specific factor in the decision to wean or to breed (indicated by % of total respondents) was generally higher than the number of farmers that could really provide information on the value (n) of that factor.
functioning of the rumen and should therefore be given at an early age (i.e. within the first week of life; Quigley III et al., 1996b). In our survey, 17.8% of the farmers provided water in the first week of life. Nevertheless, 26.7% waited until the calves had reached an age of 4 weeks. Intake of solid feed stimulates the development of the rumen. Most farmers offered concentrates and roughages early; within the first 2 weeks of life, 59.8% of the farmers fed concentrates and 69.4% roughages. Most of the farmers weaned their calves much later than the recommended weaning age of 8±9 weeks (Boxem et al., 1991) as indicated by the median value of age at weaning of 10 weeks (Table 4). In 29% of the cases weaning occurred at an age of 8 weeks, 35% at 9±10 weeks of age and 36% at 11 weeks of age. Most farmers (89%) indicated that age determined their decision to wean calves (Table 4). Only a small proportion of the farmers considered factors such as the amount of concentrates intake (33%) and BW (17%) in their decision to wean the calves. 3.4. Breeding moment Most farmers (81%) started to breed their heifers at an age of 15 months (Table 4); breeding time was largely determined by age (95%). Factors indicating the physiological development of the animal were considered to be of lesser concern; only 27 and 17% of the farmers responded that, respectively, wither height and BW influenced their decision to breed (Table 4). However, the number of farmers who could provide information on the actual wither height and BW at first breeding was quite low (Table 4). Season (22%) had a striking large influence on the time of first insemination. Preference existed for heifers calving during the autumn months due to less labour-intensive inseminations during the grazing season and the higher milk prices in autumn and winter.
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Fig. 3. Distribution of 906 Dutch dairy farms based on the estimated rearing costs per full-grown heifer, 1988.
Despite potential problems, 17.6% of the farms had one or more bulls to lessen the inconvenience involved with heifer breeding. For those using artificial insemination, 56.0% attained a pregnancy percentage of 70% after first insemination. Only 2.7% of the farmers achieved a pregnancy percentage of <50%. 3.5. General management practices Only 14.7% of the farmers indicated that they followed some predefined growth strategy. Furthermore, only 9.5% of the farmers monitored the growth of their young stock by BW measurements. Most of these measurements were of chest circumference (96.8%). The median value of mortality risk during rearing was 5.6% which conforms with the advised norm of <10% (Quigley III et al., 1996a). However, this mortality risk varied enormously among farms (25th percentile 0%, 75th percentile 14%). To get some insight into the extent to which farmers estimate their own rearing costs, the farmers were asked to indicate the costs of raising a full-grown dairy heifer (labour costs excluded). More than 36% of the responding farmers estimated the costs to be
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Table 5 Advised performance indices of large dairy breeda in comparison with the observed median values resulting from the survey on 959 Dutch dairy farms, 1998
Age at calving (months) BW postcalving (kg) Wither height postcalving (cm) BCS at calving Mortality total rearing period (%) a
Advised target value large dairy breed
Observed median values within survey
24 570 142 3±3.5 <10
25 525±550 141±145 3±3.5 5.6
Based on Quigley III et al. (1996b), Heinrichs and Hargrove (1987) and Van Amburgh and Galton (1994).
these values is expected to be high. Validation of these values by comparison with the official statistics from the Dutch Cattle Syndicate was, however, not possible because the questionnaires were returned anonymously. The surveyed farmers indicated that the median BW after calving was within the range of 525±550 kg, which is below the advised target value for large dairy breeds (Table 5). The 50th percentile values of wither-height class and BCS corresponded with recommendations (Table 5). Most farmers had to estimate the values on BW, witherheight and BCS through lack of actual data. The reported values on these characteristics might, therefore, reflect the farmer's performance targets or the general recommendations rather than the actual situation. To test for a discrepancy between stated and actual results, direct observations of the farms would be a necessity. Chronological age is defined in months, while physiological age is reflected by variables as BW, wither height and BCS. In replacement rearing, the rearing strategy should be determined and evaluated related to physiological age rather than chronological age (Hoffman and Funk, 1992; Heinrichs, 1993; Mourits et al., 1997). However, most of the farmers related their rearing performances primarily to chronological target values (Table 4). When intermediate evaluations of weight and stature goals and measurements are used, problems during the rearing period can be identified and appropriate corrections can be made in time. However, the use of such intermediate values was limited (Table 4). In general, most farmers change their rearing policy when age at calving is determined to be too old or when the heifers at calving are determined to be too heavy or too small. However, the intervention point during heifer rearing is not the parturition but the breeding. In practice, simple schemes of heart girth (BW measurement) and BCS measurements at breeding and at calving (or at a single time for all replacements onhand) are very useful in fine tuning the rearing strategy. The small quantity of actual data on performance indices as BW, wither height and BCS along with the fact that most farmers only consider a target value for calving age demonstrate that, in general, the data monitoring aspect is not implemented in the heifer rearing management. Monitoring is a critical function of effective management and data records are a necessity if this function is to be carried out. Unfortunately, recording and managing data is a tedious and time-consuming task that often seems to have no immediate value. When it comes to rearing heifers, this belief is enhanced because pre-
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calving heifers do not provide any income. The fact that raising dairy replacements represent the second largest expenditure on a farm (Stelwagen and Grieve, 1992) is often not understood. This lack of insight was also observed in this survey. In the Netherlands, practical advisors estimate the heifer rearing costs (without the costs of labour) at Dfl 2200±2600 per full-grown heifer (Boxem et al., 1991; Dienst Landbouw Voorlichting, 1998, personal communication). As depicted by Fig. 3, more than 36% of the responding farmers estimated the rearing costs of a full-grown heifer (labour excluded) under Dfl 1500, indicating an underestimation of more than 30%. 5. Conclusion Based on the results of this survey on 959 dairy farms, we concluded that the rearing of dairy heifers in the Netherlands is an area where management practices need improvement. Many of the reported performance indices on age and BW were outside the range of the recommended target values. Moreover, the surveyed dairy farmers were not accustomed to applying such essential tools as record keeping and data monitoring. Acknowledgements Appreciation is extended to J.W. Reijs and K.J. van Calker who participated in the processing of the data and to the dairy farmers for their time in participating in the survey. Appendix A. Design of questionnaire on heifer-rearing practices. (The questionnaire (in Dutch) is available on request from the author.) Subject
No. of
Characterisation of surveyed aspects
Questions
Categoriesa
11
11
Location; breed; number of milking cows, heifers and calves; milk production; labour capacity
Characteristics of calving 10 heifers
14
Age, BW, wither height and BCS at calving; market value; rearing costs; production value; replacement percentage; reasons for replacement
1
Frequency and amount of colostrum fed
General farm description
Feed management Colostral period
1
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Milking period
5
9
Post-weaning period
6
11
Growth rate strategy
8
10
Housing
3
4
Type of housing
Calving practices
2
4
Number of calvings; number of difficult calvings
Health General
4
6
Heifer calves (<1 year)
5
5
Heifers (1 year)
4
4
Occurrence of diseases; mortality risks Prevention measurements; number of treatments per disease Prevention measurements; number of treatments per disease; reasons for culling
2
2
General remarks
Type and amount of liquid feed and solid feed; weaning age; factors determining weaning moment Ration formulation; use of pasture; period of grazing Target values of age, BW, BCS at breeding and calving; factors determining breeding moment; age, BW and wither height at breeding; pregnancy percentage
Opinion on relevance of practical advises; opinion on survey
a
Some questions included a number of subquestions, depicted by the total number of surveyed categories. References Boxem, T., Oudenampsen, H.J.J., Zimmer, G.G., 1991. Rearing dairy heifers. Practice-series Animal Husbandry. Misset, Doetinchem, 56 pp (in Dutch). Dutch Cattle Syndicate, 1998. Annual-statistics. NRS, Arnhem, 62 pp (in Dutch). Heinrichs, A.J., 1993. Raising dairy replacements to meet the need of the 21st century. J. Dairy Sci. 76, 3179± 3187. Heinrichs, A.J., Hargrove, G.L., 1987. Standards of weight and height for Holstein heifers. J. Dairy Sci. 70, 653± 660. Hoffman, P.C., Funk, A., 1992. Applied dynamics of dairy replacement growth and management. J. Dairy Sci. 75, 2504±2516. Mourits, M.C.M., Dijkhuizen, A.A., Huirne, R.B.M., Galligan, D.T., 1997. Technical and economic models to support heifer management decisions: basic concepts. J. Dairy Sci. 80, 1406±1415. Norusis, M.J., 1993. SPSS for Windows; Base System User's Guide, Release 6.0. SPSS Inc., Chicago, IL, 868 pp. Quigley III, J.D., Brand, A., Benedictus, G., Kloosterman, B., 1996a. Monitoring replacement rearing: execution, decision making and follow-up. In: Brand, A., Noordhuizen, J.P.T.M., Schukken, Y.H. (Eds.),
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Herd Health and Production Management in Dairy Practice. Wageningen Press, Wageningen, pp. 103± 142. Quigley III, J.D., Nyabadza, C.S.T., Benedictus, G., Brand, A., 1996b. Monitoring replacement rearing: objectives and materials and methods. In: Brand, A., Noordhuizen, J.P.T.M., Schukken, Y.H. (Eds.), Herd Health and Production Management in Dairy Practice. Wageningen Press, Wageningen, pp. 75±102. Van Amburgh, M.E., Galton, D.M., 1994. Accelerated growth of Holstein heifers-effects on lactation. In: Proceedings of the 1994 Cornell Nutritional Conference for Feed Manufacturers, Rochester, NY. Department of Animal Science and Division of Nutritional Science, Cornell University, Ithaca, NY, pp. 147±154. Silvis, H.J., Van Bruchem, C., 1998. Agricultural-Economic Report 1998. Periodical 1-98. LandbouwEconomisch Instituut (LEI-DLO), Den Haag, 195 pp (in Dutch). Statistics Netherlands, 1997. CBS-agricultural Counting 1997. Misset, Doetinchem, 145 pp (in Dutch). Stelwagen, K., Grieve, D.G., 1992. Effects of plane of nutrition between 6 and 16 months of age on body composition, plasma hormone concentrations and first milk production in Holstein heifers. Can. J. Anim. Sci. 72, 337±346.
Dairy-heifer management in the Netherlands M.C.M. Mouritsa,*, H.J. Van der Fels-Klerxa, R.B.M. Huirnea, M.W.C. Huybenb a
Department of Economics and Management, Farm Management Group, Wageningen University, Hollandseweg 1, 6706 KN Wageningen, The Netherlands b Animal Health Service, PO Box 9, 7400 AA Deventer, The Netherlands Received 14 July 1999; accepted 3 May 2000
Abstract The objective of this study was to describe the Dutch rearing performance of dairy heifers by the evaluation of performance indices at weaning, breeding and calving. The second objective was to determine the extent to which dairy farmers use pre-set rearing targets and data monitoring for the evaluation of their rearing results. A questionnaire was sent to 3000 randomly chosen dairy cattle farmers to survey their heifer-rearing practices. Almost a third of the farmers (n959) completed and returned the questionnaire. Of the farms responding, 29% realised an age at first calving of 24 months, 51% from 25 to 27 months, and 20% of 27 months. The farmers indicated that the average body weight after calving was within the range 525±550 kg. Average wither height class was 141±145 cm. Most farmers estimated the body-condition score of their heifers at calving to be 3±3.5. In 29% of the cases, weaning occurred at an age of 8 weeks, 35% at 9±10 weeks of age and 36% at 11 weeks of age. Most farmers (81%) commenced breeding at an age of 15 months. Intermediate evaluation of the rearing policy by means of performance goals and measurements was limited, and many of the reported performance indices on age and body weight were outside the range of the recommended target values. These results indicated that the common Dutch heiferrearing management system could be improved considerably. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Dairy cattle-management; Rearing practices; Questionnaire
1. Introduction In the Netherlands, an average of 25±35% of the dairy herd is culled each year (Dutch Cattle Syndicate, 1998) and has to be replaced. This makes replacement rearing an essential part of dairy farm management. *
Corresponding author. Tel.: 31-317-484065; fax: 31-317-482745. E-mail address: [email protected] (M.C.M. Mourits) 0167-5877/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 8 7 7 ( 0 0 ) 0 0 1 4 6 - X
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A dairy farmer controls his or her rearing unit by the determination of a nutritional plan of growth and a breeding schedule. The ultimate goal of replacement rearing is to reach first-calving age at a predetermined time with an optimal growth rate (Quigley III et al., 1996b; Mourits et al., 1997). To guide optimal development and to identify deviations from pre-set rearing targets at an early stage, heifers must be monitored throughout the rearing period. Essential tools in the management of replacement heifer rearing are, therefore, record keeping, data monitoring and evaluation (Quigley III et al., 1996b). Unfortunately, as a component of the management system, rearing of dairy replacements is often overlooked (Mourits et al., 1997). Many dairy farmers consider the rearing period as a non-productive period which requires little attention. A better understanding of the most-limiting areas in heifer management might enhance the efforts of farm advisors in providing practical recommendations. The costs of raising dairy replacements depend to a large extent on the age at first calving. Reducing the age at first calving offers advantages such as lower overhead costs, decreased feed costs, decreased overcrowding and increased production per day of herd life (Hoffman and Funk, 1992; Mourits et al., 1997). In the Netherlands, average age at first calving is 26 months (Dutch Cattle Syndicate, 1998), despite the general recommendation of a calving age of 24 months (Hoffman and Funk, 1992; Mourits et al., 1997). However, the economic efficiency of a rearing strategy cannot be measured solely by the age at first calving (Mourits et al., 1997). Performance indices (such as body weight (BW), average daily gain, and body-condition score (BCS)) are also needed to evaluate the physiological development of the heifer. However, insight into these performance indices is lacking. The objective of this study was to describe the dairy heifer-rearing practices in the Netherlands by means of a large field survey. In particular, performance indices at weaning, breeding and calving were used to reflect the Dutch rearing performances. The second objective was to determine the extent to which dairy farmers evaluate their own rearing policies by means of pre-set rearing targets and data monitoring. 2. Materials and methods A self-administered questionnaire (Appendix A) was designed to collect the information on the Dutch heifer-rearing practices. The areas of importance were derived from an extensive literature review on heifer rearing and covered rearing goals, feeding, housing, health, reproductive management, and calving practices. The questionnaire also contained questions related to characteristics of the farm. A draft questionnaire was pretested on 10 dairy farms. Results and feedback received from this pre-test were used to fine-tune the questionnaire. The final version consisted of eight parts with 61 questions. The type of questions were open-ended (n19), semi-closed (n25) as well as closed (n17). Three thousand dairy farmers (approximately 10% of the dairy farmers in the Netherlands; Silvis and Van Bruchem, 1998) were approached with the questionnaire by mail. The farmers were selected at random (lottery mechanism) from the mailing list of
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the Dutch Animal Health Service. This mailing list covers all dairy farmers in the Netherlands. The questionnaires were sent to the farmers in November 1998. Each survey was accompanied by a cover letter explaining the purpose and scope of the study and asking for participation. To encourage participation, the cover letter pointed out that the results would help the Animal Health Service to provide high-quality advice on dairy-heifer rearing. It was stressed that all information collected would be kept strictly confidential, and that only summary results, without any personal identification, would be published. The farmers were asked to respond within 5 weeks. Three weeks after the first mailing, a reminder was sent to encourage the participation of farmers who had not responded until that time. Data transformations, descriptive analyses and hypothesis tests were performed using the statistical program SPSS 7.5 (Norusis, 1993). The Kruskal±Wallis test was used to test for differences among breeds. The Mann±Whitney test and Kolgomorov±Smirnov test were used to test whether farmers who considered target values for calving age or calving weight realised, respectively, lower calving ages (continuous variable) or heavier calving weights (categorical variable), than farmers who did not considered pre-set target values. In this paper, the emphasis is on the general aspects of dairy replacement management, depicted by weaning, breeding and calving characteristics. Aspects concerning housing and health management will be discussed in a separate paper. 3. Results 3.1. General herd characteristics Within the defined response period of 5 weeks, 959 farmers (32%) completed and returned the questionnaire. Table 1 shows the average farm characteristics of the respondents along with the average farm characteristics of the total population of Dutch dairy farms. Table 2 shows the relative distribution of the main characteristics of both, the farms within the survey and the total population. The distribution of surveyed herd sizes was comparable with the distribution of herd size within the complete population (Table 2). The distributions on farm intensity demonstrated that intensive farms were rather under-represented within the survey. The distributions of milk production on the surveyed farms and on the farms in the complete population were comparable, although in the survey the percentage of farms with extremely low or high production values was lower than in the total population of dairy farms (Table 2). Based on the correspondence in the average values of the general farm characteristics (Table 1) and the relative distributions of three main characteristics (Table 2), we consider the farms within the survey to be representative for the total population. Relative distribution of respondents per region corresponded with the relative distribution of dairy farms per region. The ranges within the characteristics of the surveyed farms demonstrate the large variation among dairy farms. Among the respondents there were two farmers who were specialised in heifer rearing (explaining the zero within the range of dairy herd size and
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Table 1 Farm characteristics of the Dutch dairy farm population (N30 400) and the dairy farms surveyed (n959) in 1998 Farm characteristic
Dutch population mean
Survey Minimum
Herd size Dairy cows Young stock>1 year Young stock1 year
52a 24b 17b
Grass and arable land (ha)
32.0a ÿ1
Intensity (livestock unit ha )
2.1
305-Day milk production (kg)
d
c
Maximum
0 0 0
56 22 22
301 160 255
2
33.4
164
0.6
7733
Mean
3300
2.2 7769
7.4 10973
a
Silvis and Van Bruchem (1998). Statistics Netherlands (1997). c Derived from Silvis and Van Bruchem (1998) and Statistics Netherlands (1997). d Dutch Cattle Syndicate (1998). b
Table 2 Relative distribution of the Dutch dairy farm population (N30 400) and the dairy farms surveyed (n959) on dairy herd size, intensity and average milk production per lactation, 1998 Farm characteristic
Level
Population (%)a
Survey (%)
Dairy herd size
20 21±40 41±60 61±80 81±100 101±150 151
7.6 26.7 34.9 18.7 7.2 4.2 0.8
6.9 22.7 35.7 21.2 8.7 4.1 0.7
Intensity (livestock unit haÿ1)
<1 1±2 2±3 3±4 4±5 5±6 6
0.8 30.9 46.3 11.2 4.6 2.5 3.7
0.8 38.0 53.7 6.3 0.8 0.3 0.1
Milk production (kg)
<5800 5800±6600 6600±7400 7400±8200 8200±9000 9000±9800 9000
4.5 9.2 17.8 24.8 23.5 13.5 6.6
3.5 8.3 20.5 33.9 22.1 9.6 2.1
a
Based on Statistics Netherlands (1997) and Dutch Cattle Syndicate (1998).
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Table 3 Distribution of average milk production and calving age by breed based on results of a survey among 959 Dutch dairy farms, 1998 Breed
Holstein MRYb Red Holstein Friesian Holstein Otherc
na
627 141 105 33 12
305-day milk production (kg) percentiles
Calving age (month) percentiles
a
n
25th
50th
75th
na
25th
50th
75th
610 120 102 28 9
7500 6000 7120 6525 5385
8000 6860 7500 7535 6100
8600 7330 8000 8030 7800
603 129 99 27 12
24 25 25 24 24
25 26 26 26 25
26 28 27 26 28
a
Completeness of questionnaire differed per subject. Meuse Rhine and Yssel. c Other breeds: Blister Head, Jersey, Monte Beliarde, Brown Swiss. b
the large numbers within the range of number of young stock). Furthermore, there were six farms without any young stock younger than 1 year and five farms without any young stock older than 1 year (Table 1). The primary breed of dairy cattle (Table 3) was Holstein. The median 305-day herd production differed significantly among breeds (Kruskal±Wallis, w2187.5, d.f.4, P<0.01). 3.2. First calving In general, the distribution of calving age is skewed toward older heifers. To prevent an indistinct definition of the average first-calving age, the farmers were explicitly asked for the age at which the plurality of the heifers gave birth (mode). Of the farms surveyed, 29% had a mode value for first-calving age of 24 months, 51% from 25 to 27 months, and 20% of >27 months (Fig. 1). Eighty percent of the farmers (n768) indicated that they aimed for a specified target age at first calving. Of these farmers, more than 50% strove for the recommended target
Fig. 1. Distribution of herd-specific first-calving age on 959 Dutch dairy farms based on the realised calving age of most of the dairy heifers (realised), and the farmer-indicated target values of age at first calving (target) (1998).
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Fig. 2. Distribution of herd-specific postcalving weight classes on 959 Dutch dairy farms based on the most frequently observed weight classes after calving (realised), and the farmer-indicated target values of BW after calving (target) (1998).
age of 24 months, while 24% aimed for a calving age of 26 months or more (Fig. 1). The farmers who considered a target calving age realised a lower calving age (median25 months), than the farmers who did not consider a pre-set target age (median26 months). This inequality between the two subsets of farmers was significant (Mann±Whitney, U49 631, P<0.01). Subdividing age at first calving by breed (Table 3) showed a tendency towards a lower calving age for the typical dairy breeds Holstein and Friesian Holstein and a higher calving age for the so-called ``double purpose'' breed (MRY) (Kruskal±Wallis, w235.0, d.f.4, P<0.01). Only 1.4% of the farmers actually weighed the heifers after calving; most farmers gave an estimation of BW after calving (Fig. 2). The small interest in calving weight is also revealed in that 57% of the farmers did not aim for a pre-set target value. Within the subset of farmers that considered a target value, 50.3% indicated a target value for BW after calving of >550 kg (Fig. 2). Farmers who considered pre-set target values for calving weight realised heavier calving weights than farmers who did not (Kolmogorov± Smirnov, D0.083, P<0.05). A small majority (55.8%) of the surveyed farmers measured the wither height of the heifers after calving. Of these farmers, 55.5% reported an average wither height within the range 141±145 cm. Prior to calving, 72% of the farmers kept an eye on the BCS of the heifer; however, only 1% actually monitored BCS. On an annual basis, 31.6% of the dairy cows were replaced by heifers. However, 18.6% of these dairy replacements were replaced again during their first lactation. The main reasons of this early replacement were fertility problems (32% of the cases), insufficient milk production (29%), udder problems (17%), sale (10%) and foot problems (5%). 3.3. Weaning period Of the heifer calves born, 77.7% were retained to be reared as replacements. After the colostral period, mastitic or antibiotic milk (37.1%), milk replacer (34.3%) and whole milk (28.6%) were the types of liquids most often fed. Free water intake is essential for
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Table 4 Decision criteria for weaning and first breeding of dairy heifers (959 Dutch dairy farms, 1998)
Weaning Age at weaning (weeks) Concentrates intake at weaning (kg per day) BW at weaning (kg) Other First breeding Age at first breeding (month) Wither height at first breeding (cm) BW at first breeding (kg) Season Other
Decisive factor percentage of total respondentsa
Values percentile
89.3 33.4
na
25th
50th
75th
75 121
8 1
10 1
12 2
16.8 3.5
88 ±
65 ±
78 ±
99 ±
94.6 26.6 17.4 22.0 2.2
774 30 47 ± ±
15 125 325 ± ±
15 130 350 ± ±
16 135 387 ± ±
a The number of farmers that indicated to consider a specific factor in the decision to wean or to breed (indicated by % of total respondents) was generally higher than the number of farmers that could really provide information on the value (n) of that factor.
functioning of the rumen and should therefore be given at an early age (i.e. within the first week of life; Quigley III et al., 1996b). In our survey, 17.8% of the farmers provided water in the first week of life. Nevertheless, 26.7% waited until the calves had reached an age of 4 weeks. Intake of solid feed stimulates the development of the rumen. Most farmers offered concentrates and roughages early; within the first 2 weeks of life, 59.8% of the farmers fed concentrates and 69.4% roughages. Most of the farmers weaned their calves much later than the recommended weaning age of 8±9 weeks (Boxem et al., 1991) as indicated by the median value of age at weaning of 10 weeks (Table 4). In 29% of the cases weaning occurred at an age of 8 weeks, 35% at 9±10 weeks of age and 36% at 11 weeks of age. Most farmers (89%) indicated that age determined their decision to wean calves (Table 4). Only a small proportion of the farmers considered factors such as the amount of concentrates intake (33%) and BW (17%) in their decision to wean the calves. 3.4. Breeding moment Most farmers (81%) started to breed their heifers at an age of 15 months (Table 4); breeding time was largely determined by age (95%). Factors indicating the physiological development of the animal were considered to be of lesser concern; only 27 and 17% of the farmers responded that, respectively, wither height and BW influenced their decision to breed (Table 4). However, the number of farmers who could provide information on the actual wither height and BW at first breeding was quite low (Table 4). Season (22%) had a striking large influence on the time of first insemination. Preference existed for heifers calving during the autumn months due to less labour-intensive inseminations during the grazing season and the higher milk prices in autumn and winter.
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Fig. 3. Distribution of 906 Dutch dairy farms based on the estimated rearing costs per full-grown heifer, 1988.
Despite potential problems, 17.6% of the farms had one or more bulls to lessen the inconvenience involved with heifer breeding. For those using artificial insemination, 56.0% attained a pregnancy percentage of 70% after first insemination. Only 2.7% of the farmers achieved a pregnancy percentage of <50%. 3.5. General management practices Only 14.7% of the farmers indicated that they followed some predefined growth strategy. Furthermore, only 9.5% of the farmers monitored the growth of their young stock by BW measurements. Most of these measurements were of chest circumference (96.8%). The median value of mortality risk during rearing was 5.6% which conforms with the advised norm of <10% (Quigley III et al., 1996a). However, this mortality risk varied enormously among farms (25th percentile 0%, 75th percentile 14%). To get some insight into the extent to which farmers estimate their own rearing costs, the farmers were asked to indicate the costs of raising a full-grown dairy heifer (labour costs excluded). More than 36% of the responding farmers estimated the costs to be
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Table 5 Advised performance indices of large dairy breeda in comparison with the observed median values resulting from the survey on 959 Dutch dairy farms, 1998
Age at calving (months) BW postcalving (kg) Wither height postcalving (cm) BCS at calving Mortality total rearing period (%) a
Advised target value large dairy breed
Observed median values within survey
24 570 142 3±3.5 <10
25 525±550 141±145 3±3.5 5.6
Based on Quigley III et al. (1996b), Heinrichs and Hargrove (1987) and Van Amburgh and Galton (1994).
these values is expected to be high. Validation of these values by comparison with the official statistics from the Dutch Cattle Syndicate was, however, not possible because the questionnaires were returned anonymously. The surveyed farmers indicated that the median BW after calving was within the range of 525±550 kg, which is below the advised target value for large dairy breeds (Table 5). The 50th percentile values of wither-height class and BCS corresponded with recommendations (Table 5). Most farmers had to estimate the values on BW, witherheight and BCS through lack of actual data. The reported values on these characteristics might, therefore, reflect the farmer's performance targets or the general recommendations rather than the actual situation. To test for a discrepancy between stated and actual results, direct observations of the farms would be a necessity. Chronological age is defined in months, while physiological age is reflected by variables as BW, wither height and BCS. In replacement rearing, the rearing strategy should be determined and evaluated related to physiological age rather than chronological age (Hoffman and Funk, 1992; Heinrichs, 1993; Mourits et al., 1997). However, most of the farmers related their rearing performances primarily to chronological target values (Table 4). When intermediate evaluations of weight and stature goals and measurements are used, problems during the rearing period can be identified and appropriate corrections can be made in time. However, the use of such intermediate values was limited (Table 4). In general, most farmers change their rearing policy when age at calving is determined to be too old or when the heifers at calving are determined to be too heavy or too small. However, the intervention point during heifer rearing is not the parturition but the breeding. In practice, simple schemes of heart girth (BW measurement) and BCS measurements at breeding and at calving (or at a single time for all replacements onhand) are very useful in fine tuning the rearing strategy. The small quantity of actual data on performance indices as BW, wither height and BCS along with the fact that most farmers only consider a target value for calving age demonstrate that, in general, the data monitoring aspect is not implemented in the heifer rearing management. Monitoring is a critical function of effective management and data records are a necessity if this function is to be carried out. Unfortunately, recording and managing data is a tedious and time-consuming task that often seems to have no immediate value. When it comes to rearing heifers, this belief is enhanced because pre-
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calving heifers do not provide any income. The fact that raising dairy replacements represent the second largest expenditure on a farm (Stelwagen and Grieve, 1992) is often not understood. This lack of insight was also observed in this survey. In the Netherlands, practical advisors estimate the heifer rearing costs (without the costs of labour) at Dfl 2200±2600 per full-grown heifer (Boxem et al., 1991; Dienst Landbouw Voorlichting, 1998, personal communication). As depicted by Fig. 3, more than 36% of the responding farmers estimated the rearing costs of a full-grown heifer (labour excluded) under Dfl 1500, indicating an underestimation of more than 30%. 5. Conclusion Based on the results of this survey on 959 dairy farms, we concluded that the rearing of dairy heifers in the Netherlands is an area where management practices need improvement. Many of the reported performance indices on age and BW were outside the range of the recommended target values. Moreover, the surveyed dairy farmers were not accustomed to applying such essential tools as record keeping and data monitoring. Acknowledgements Appreciation is extended to J.W. Reijs and K.J. van Calker who participated in the processing of the data and to the dairy farmers for their time in participating in the survey. Appendix A. Design of questionnaire on heifer-rearing practices. (The questionnaire (in Dutch) is available on request from the author.) Subject
No. of
Characterisation of surveyed aspects
Questions
Categoriesa
11
11
Location; breed; number of milking cows, heifers and calves; milk production; labour capacity
Characteristics of calving 10 heifers
14
Age, BW, wither height and BCS at calving; market value; rearing costs; production value; replacement percentage; reasons for replacement
1
Frequency and amount of colostrum fed
General farm description
Feed management Colostral period
1
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Milking period
5
9
Post-weaning period
6
11
Growth rate strategy
8
10
Housing
3
4
Type of housing
Calving practices
2
4
Number of calvings; number of difficult calvings
Health General
4
6
Heifer calves (<1 year)
5
5
Heifers (1 year)
4
4
Occurrence of diseases; mortality risks Prevention measurements; number of treatments per disease Prevention measurements; number of treatments per disease; reasons for culling
2
2
General remarks
Type and amount of liquid feed and solid feed; weaning age; factors determining weaning moment Ration formulation; use of pasture; period of grazing Target values of age, BW, BCS at breeding and calving; factors determining breeding moment; age, BW and wither height at breeding; pregnancy percentage
Opinion on relevance of practical advises; opinion on survey
a
Some questions included a number of subquestions, depicted by the total number of surveyed categories. References Boxem, T., Oudenampsen, H.J.J., Zimmer, G.G., 1991. Rearing dairy heifers. Practice-series Animal Husbandry. Misset, Doetinchem, 56 pp (in Dutch). Dutch Cattle Syndicate, 1998. Annual-statistics. NRS, Arnhem, 62 pp (in Dutch). Heinrichs, A.J., 1993. Raising dairy replacements to meet the need of the 21st century. J. Dairy Sci. 76, 3179± 3187. Heinrichs, A.J., Hargrove, G.L., 1987. Standards of weight and height for Holstein heifers. J. Dairy Sci. 70, 653± 660. Hoffman, P.C., Funk, A., 1992. Applied dynamics of dairy replacement growth and management. J. Dairy Sci. 75, 2504±2516. Mourits, M.C.M., Dijkhuizen, A.A., Huirne, R.B.M., Galligan, D.T., 1997. Technical and economic models to support heifer management decisions: basic concepts. J. Dairy Sci. 80, 1406±1415. Norusis, M.J., 1993. SPSS for Windows; Base System User's Guide, Release 6.0. SPSS Inc., Chicago, IL, 868 pp. Quigley III, J.D., Brand, A., Benedictus, G., Kloosterman, B., 1996a. Monitoring replacement rearing: execution, decision making and follow-up. In: Brand, A., Noordhuizen, J.P.T.M., Schukken, Y.H. (Eds.),
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Herd Health and Production Management in Dairy Practice. Wageningen Press, Wageningen, pp. 103± 142. Quigley III, J.D., Nyabadza, C.S.T., Benedictus, G., Brand, A., 1996b. Monitoring replacement rearing: objectives and materials and methods. In: Brand, A., Noordhuizen, J.P.T.M., Schukken, Y.H. (Eds.), Herd Health and Production Management in Dairy Practice. Wageningen Press, Wageningen, pp. 75±102. Van Amburgh, M.E., Galton, D.M., 1994. Accelerated growth of Holstein heifers-effects on lactation. In: Proceedings of the 1994 Cornell Nutritional Conference for Feed Manufacturers, Rochester, NY. Department of Animal Science and Division of Nutritional Science, Cornell University, Ithaca, NY, pp. 147±154. Silvis, H.J., Van Bruchem, C., 1998. Agricultural-Economic Report 1998. Periodical 1-98. LandbouwEconomisch Instituut (LEI-DLO), Den Haag, 195 pp (in Dutch). Statistics Netherlands, 1997. CBS-agricultural Counting 1997. Misset, Doetinchem, 145 pp (in Dutch). Stelwagen, K., Grieve, D.G., 1992. Effects of plane of nutrition between 6 and 16 months of age on body composition, plasma hormone concentrations and first milk production in Holstein heifers. Can. J. Anim. Sci. 72, 337±346.