Influence of diet on forestomach structure and occurrence of digital diseases in adult goats

SmallRuminant Research, 10 ( 1 9 9 3 ) 6 3 - 7 3

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© 1993 Elsevier Science Publishers B.V. All rights reserved. 0 9 2 1 - 4 4 8 8 / 9 3 / $ 0 6 . 0 0

Influence of diet on forestomach structure and occurrence of digital diseases in adult goats M.N. Mgasa and J. Arnbjerg Institute of Clinical Studies, Department of Veterinary Radiology, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark (Accepted 6 May 1992 )

ABSTRACT Mgasa, M.N. and Arnbjerg, J., 1993. Influence of diet on forestomach structure and occurrence of digital diseases in adult goats. Small Rumin. Res., 10: 63-73. Twenty adult female Tanzanian goats (Small East African breed) of unknown ages weighing between 15-20 kg were divided into two groups, A and B. The groups were grazed together in the same pastures. Group A was supplemented with limited concentrates in prepartum period. After parturition, they were offered ad libitum concentrates without any roughage for 1 week. Group B was grazed throughout without any supplementation. Lameness was observed to occur during the postpartum period with one goat having white line disease in group A and two goats, one with foot abscess and the other with white line disease in group B. Occurrence of digital diseases was not associated with diet as there was no significant difference between the groups ( P > 0.05 ). Forestomach structure did not differ significantly between the groups ( P > 0.05). Although rumen acidosis (rumen pH < 5.4) was recorded in some goats exposed to ad libitum concentrates in the postpartum period, no clinical signs of acidosis or laminitis were observed. The study showed that adult goats have a stable rumen structure and are resistant to laminitis even when exposed to high amounts of concentrates. Goats also proved to be a bad model for studying laminitis in ruminants due to the difficulty of inducing the condition. However, there is a great improvement potential in meat and milk production from goats which can be achieved through supplementation with concentrates without fear of laminitis. Key words: Diet; Forestomach; Digital disease; Tanzania; Lameness; Acidosis; Goat

INTRODUCTION

The demand for goat meat in tropical Africa is high and exceeds supplies. This is because production depends on traditional management systems which basically rely on natural pastures whose nutritive value is greatly influenced by season (Butterworth, 1967; Karue, 1978; Kyomo, 1978; Devendra and Burns, 1983 ). Free range type of management dominating the traditional sysCorrespondence to and present address: M.N. Mgasa, Faculty of Veterinary Medicine, Sokoine University o f Agriculture, P.O. Box 3020, Morogoro, Tanzania.

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terns has the advantage of low cost and fair utilization of non-arable land (Reynold, 1986). However, its usefulness is offset by poor productivity (Omeke, 1988). Improvement in management of goats could make a substantial contribution to Tanzanian livestock industry. Energy intake has been reported to be a major limiting factor for growth of ruminants in semi-arid grasslands (Madsen et al., 1990). Shortage of animal protein in semi-arid tropics calls for improved management which includes intensification of management and supplementation of goats with concentrates to maximize their potential as meat or milk producers. However, feeding ruminants high energy concentrates has been associated with laminitis (Mortensen and Hesselholt, 1982; Liversey and Fleming, 1984; Peterse, 1985; Mgasa, 1989; Greenough and Vermunt, 1991 ) and occurrence of forestomach lesions (McGavin and Morril, 1976a; Dirksen et al., 1985; Liebich, et al., 1987). Experimental studies have shown that young goats have a higher resistance to laminitis and occurrence of lesions in the forestomach when fed on concentrates compared to cattle (Mgasa and Mbassa, 1988 ). This indicates that goats can tolerate high amounts of concentrates without side effects. Effects of concentrate feeding on the forestomach and digits in adult goats has not been adequately studied. The influence of low or high plane of diet on the structure of forestomach and digits of adult Tanzanian goats is reported. MATERIALS AND METHODS

Twenty adult female Tanzanian goats (Small East African breed) of unknown ages weighing between 15-20 kg were bought from a local market in Morogoro. All goats had at least one kidding and were not pregnant. Goats were introduced into the experiment after confinement indoors for 2 weeks as preliminary adaptation. During this time, blood smears were made to screen for trypanosomiasis and tick borne diseases. Faecal samples were also collected and examined for helminthiasis. Mass treatment with multivitamin injection and deworming by drenching with 2 to 3 ml of 10% Panacur R (Fenbendazole) was done. They were also given Isometamidium (Samorin R) at dose of 0.5 mg/kg intramuscularly for therapy and prophylaxis against trypanosomiasis. Tetanus toxoid was also given. They were treated against ectoparasites by acaricide (toxaphene) spraying. Hoof trimming was done at the beginning of the experiment. During the third week, goats were bred after synchronization of oestrus using prostaglandin PGF2 (Dinolytic VetR) at a total dose of 15 mg intramuscularly. Natural service was by introduction of males of the Norwegian dairy goat breed to the females 48 h after prostaglandin injection. Males were left to run with the females for 1 week and thereafter withdrawn. With the protocol of a single dose used in this study, some goats did not respond because they were not in the luteal phase at the time of injection. This was shown by

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the failure of some goats to conceive despite the synchronization. A repeat dose at 11 days was not necessary because non-pregnant animals were to be used as controls in each group. Two groups, A and B, were randomly chosen with ten animals in each group and kept in separate cubicles under different feeding regimes. They were housed on concrete floored cubicles with wood shaving as bedding, which was changed every 2 days, and pens were kept clean and dry. Fresh and clean water was provided ad libitum everyday in plastic buckets placed in the pens. All animals grazed together in the University farm paddocks from 8:00 a.m. until 12:00 noon. In the afternoon (from 14:00 to 16:00 p.m.) only group B was let out to pastures, while group A remained indoors and was provided ad libitum concentrates. The daily consumption was calculated at 450 g per animal. However, the total a m o u n t of feed for all the goats each day was placed in a c o m m o n feeding trough where all the animals had free access and the exact a m o u n t consumed by each animal was not controlled. Acaricide spraying to control ectoparasite was carried out twice a week, while deworming with Fenbendazole was later observed to be ineffective and, therefore, deworming was switched over to Levamisole at 4 m g / k g subcutaneously once every month. A 5% formalin footbath was used twice a week to control infectious foot problems. The pasture was mainly composed of grass and shrubs, on some occasions crop residues after harvesting such as maize and millet were present. The nutrient composition of pasture was no determined as the goats were grazing widely. The concentrate provided was composed of coarsely ground maize, maize bran, small a m o u n t of cotton seed cake, minerals and vitamins. The feed composition analysis of the concentrate (%) was: Dry matter ( D M ) = 9 1 . 1 ; crude p r o t e i n / D M = 1 3 . 9 ; f a t / D M = 1 0 . 9 ; crude fibre/ DM = 9.3; a s h / D M = 7.1; and nitrogen-free extract = 58.8. At paturition or incidental abortion, does were immediately transferred to kidding pens, together with their live kids, and confined throughout the day for 1 week. During this postpartum confinement period goats from group A were provided concentrates ad libitum without any roughage. The calculated consumption per day was about 800 g per animal. While those from group B were fed on grass and shrubs brought to the pen. Water was provided ad libit u m to all groups. After this period goats were let out to graze in their respective groups as before parturition. However, those from group A were provided concentrates ad libitum after the morning grazing. The kids were left to suckle their does uncontrolled. Goats which never became pregnant remained under the same management and feeding in their respective groups. A clinical examination with particular emphasis on lameness, forestomach function and general body condition was carried out every day in the morning when the goats were let out for pasturing. Radiographs of the limb bones were taken at the beginning of the experiment, after 3 months and at any time of

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TABLE 1 Criteria employed for macroscopic scoring of rumen papillae and forestomach pathology Score

Structure of papillae

Colour of mucosa

Pathological changes

0 1

NA light grey

no changes slight

2 3 4

NA short slender, pointed short and leaflike long and leaf like long and thread like

grey dark grey dark

pronounced very pronounced severe changes with complications

5

long tongue shaped

incidental lameness or death. The right front and right hind legs were taken on routine. Dorsopalmar and lateromedial views were taken using normal film (Fuji RX universal) and standard intensifying screen in cassettes at a focus film distance of 1 meter. Exposures of 60 kV and 20 mAs were taken using a movable X-ray machine (Siemens). Postpartum animals were slaughtered 2 months after parturition, while all those which did not become pregnant were slaughtered after 9 months in the experiment. Immediately after slaughter or death, a complete postmortem was performed. Special attention was taken on the forestomach and digits. The reticulorumen was dissected according to McGavin and Morril ( 1976b ). Immediately after opening the rumen, rumen liquor was collected and pH was determined using a digital pH meter. The reticulorumen was emptied and washed. The omasum was separated from the abomasum, opened along the minor curvature, the abomasum was opened along the major curvature and the duodenum intermesenterically. Organs were washed with running water after the contents had been emptied. Structure and morphology of rumen papillae, reticulum and omasum was evaluated macroscopically. Different scores were given according to appearance of structure, colour and pathological status using the criteria in Table 1. Feet were examined after cleaning and trimming and lesions recorded. Data were analyzed by comparing the relative risk ratios and chi-square test for significance of association was used in accordance with Martin et al. ( 1987 ). The Student's t-test was also used. RESULTS

Five goats died within the first month of the experiment, with three from group B dying of haemonchosis and two from group A dying from a mixed chronic fascioliasis and haemonchosis infestation. Goats were heavily infected from the beginning of the experiment as high faecal egg counts were

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67

recorded in these animals. They were, therefore, not considered in the results presented here. After death of these animals faecal samples taken from all the remaining animals still revealed high egg counts despite deworming with Fenbendazole. This indicated that panacur was not effective against haemonchus worms. According to Ngomuo et al. (1990) and Bjorn et al. (1991) some strains ofHaemonchus contortus present at the University farm in Morogoro have been proved to be resistant to benzimidazoles (Fenbendazole) even at higher than the recommended dosage. Due to these observations, deworming was switched over to Levamisole subcutaneous injection. With a monthly deworming program there was no more deaths, faecal egg counts reduced to insignificant levels and the disease was under control throughout the experiment. Triclabendazole was also given at 10 mg/kg orally for treatment of fascioliasis. In group A and B, four and five goats, respectively, were pregnant after synchronization with prostaglandin. However, four and two goats from group A and B, respectively, did not get pregnant and these were used as controls. During the course of the experiment five goats, two from group A and three from group B, aborted in the third trimester of pregnancy. There was no significant organism isolated from foetal fluids and vaginal swabs which could be considered as the primary cause of the abortion. Brucella test on blood plasma and milk samples were also negative. No complications occurred after abortion and the animals recovered without any treatment. These does were, TABLE2 Distribution of digital diseases, hoof overgrowth and lameness in each group Postpartum

Goat group A (concentrate supplemented ) Hoof overgrowth White line disease Foot abscess Lameness Goat group B (grazing without supplementation ) Hoof overgrowth White line disease Foot abscess Lameness

Non pregnant

Total

(%)

normal

aborted

(n=2)

(n=2)

(n=4)

(n=8)

0 0 0 0

0 1 0 1

0 0 0 0

0.0 12.5 0.0 12.5

(n=2)

(n=3)

(n=2)

(n=7)

1 0 0 0

1~ 1 1 2

0 0 0 0

28.6 14.5 14.5 28.6

n = Total number of animals in each category. ~Hoof overgrowth was not associated with lameness.

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Fig. 1. Radiograph of the right hind digit of the goat from group B with foot abscess. Middle phalanx = l; distal sesamoid bone = 2; distal phalanx = 3. The distal interphalangeal joint appears infected (arrows) and there is osteolysis of all the bones around the joint with marked soft tissue swelling on the digit.

therefore, considered to be normal and given a similar management to the other postpartum goats in their respective groups. Digital lameness was observed in one goat from group A and two others from group B (Table 2). White line disease was observed to affect one goat from each group in association with lameness. Lameness in the other goat from group B was due to foot abscess. H o o f overgrowth was observed in two goats from group B, but was not associated with lameness. In both groups, lameness occurred during the postpartum period after the confinement. All goats which were not pregnant and, therefore, not confined, had no lameness. White line disease was characterized by underrunning of the hoof wall abaxially forming a cavity and hollow wall which was observed to be impacted with dirty and constant wetness. On paring the digit, the lesion was observed to extend deep into the sensitive laminae with pus formation and pain. The animal with foot abscess from group B was noticed with acute unilateral lameness and swelling of the right hind outer digit 1 week after the postpart u m confinement period. In the initial stages, the digit was observed with a deep fissure axially in the bulb area which was wet and impacted with dirty and foul smelling pus oozed out on applying pressure. The excess horn was

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TABLE 3 Macroscopic scores of the papillae structure, colour of mucosa, forestomach pathology and rumen pH Postpartum normal

Non pregnant aborted

Goat group A (supplemented with concentrates ) Goat number 93 97 Weeks in experiment 34 43 Rumen pH 5.2 5.7 Pathological changes 0 0 Structure of papillae 5 3 Colour of mucosa 3 2

79 39 5.3 0 4 3

96 30 5.4 0 5 3

Goat group B (grazing without supplementation ) Goat number 95 99 Weeks in experiment 39 43 Rumen pH 5.4 6.7 Pathological changes 0 0 Structure of papillae 4 4 Colour of mucosa 1 3

89 39 5.4 0 5 3

91 41 6.8 0 4 1

98 39 6.5 0 4 3

80 43 6.7 0 3 3

81 43 6.4 0 3 3

84 43 6.2 0 4 1

76 43 6.5 0 4 1

83 43 6.8 0 4 1

85 43 5.8 0 3 3

t r i m m e d and no other treatment was given apart from the routine formalin foot bathing. However, the animal did not improve, it became chronically lame and moved on three legs. Radiography revealed infection of the distal interphalangeal joint with osteolysis of the distal part of the middle phalanx, the proximal part of the distal phalanx and the distal sesamoid bone (Fig. 1 ). Periarticular soft tissue swelling was also observed. The feeding of concentrates was not associated with occurrence of lameness as no significant difference was observed between groups ( P > 0.05 ). Results from postmortem examination of the forestomach and rumen pH values are summarized in Table 3. All goats were observed to have a welldeveloped forestomach structure, and papillae structure in the rumen were also well developed. In both groups, papillae shapes varied between slender, leaf like or tongue shaped, but they were all long. Comparison of mean scores did not show any significant differences between groups ( P > 0.05). There were no pathological changes in any of the forestomach compartments. Mucosa colour in goats from both groups appeared to vary from light grey, grey to dark grey between individuals in each group. However, mean colour scores between groups did not show significant differences ( P > 0.05 ). Reticulum and o m a s u m had a colour similar to that observed in the rumen. R u m e n pH values varied between individual goats within each group. A comparison of mean pH values between groups did not show significant differences. How-

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ever, mean pH of postpartum goats in group A was lower than in non-pregnant goats within the same group ( P < 0.05 ). In addition, two of the postpartum goats in group A were observed with rumen acidosis, as pH values less than 5.4 were recorded, and one of these animals had previously developed diarrhoea 10 days following exposure to ad libitum concentrates. The animal recovered on the second day without any treatment but was later observed to be lame. DISCUSSION

Results show that white line disease and foot abscess were the only conditions observed as causes of lameness. The disease, which has been described as foot abscess in this study, appeared to be similar to that described in sheep (West, 1983 ). Foot abscess in sheep is considered to be a true mixed infection with Fusobacterium necrophorum and Corynebacterium pyogenes in which the bulbar soft tissue (Roberts et al., 1968 ) and distal interphalangeal joint (West, 1983 ) are invaded. Although no isolation of bacteria was done in this study, the characteristics of the disease observed were similar to those described by West (1983 ) which lead to the assumption that a bacterial infection may be involved. White line disease in the other two goats was an inflammatory reaction with pus formation in the abaxial wall of the digits. It is presumed that both these diseases were of bacterial origin. Furthermore, the occurrence of lameness after the postpartum confinement period suggests that it was a predisposing factor. This was because goats were indoors with bedding and cleaning not done for 2 days. Although pens were cleaned after every 2 days, the chances of having more wetness in the confined group, due to urine and faeces, was higher compared to the other pens which were left free to dry when animals were out grazing. Confinements have played a role in increasing the spread of infection particularly due to close contact with faeces and wet underfoot conditions. No other digital conditions or laminitis-like lesions were observed in goats fed ad libitum concentrates. Furthermore, goats in group B which had no exposure to concentrates were observed to be lame due to similar disease conditions as observed in group A. This indicates that concentrate feeding had no influence on the occurrence of lameness in goats. Similar observations have been reported in goats injected with lactic acid intraruminally or engorged with grains (Mgasa and Mbassa, 1988 ). R u m i n a n t s on a high nutritional plane have been reported to adapt to the diet morphologically and functionally by hyperplasia of the epithelial cells of the rumen (Fell and Weeks, 1975; Hoffman, 1989 ). Increase in papillae size and rumen hyperkeratosis or parakeratosis has been associated with altered composition of the rumen contents (Hinders and Owen, 1965; Tamata et al., 1978; Dirksen et al., 1985 ). The structure of the rumen in this study was not

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altered and no pathologic changes were observed despite the exposure to ad libitum concentrates. The appearance of the rumen papillae structure in both groups was nearly identical, indicating that differences in diet between the groups had no significant effect. The failure to observe differences could be attributed to the adaptive ability of goats to different diets. Goats have been classified as intermediate feeders due to their selective feeding habits (Hoffman, 1989 ) and are able to feed on a wide range of feedstuffs not normally eaten by other domestic ruminants (Devendra and Burns, 1983 ). This ability is reflected by the similarity of the rumen papillae structure in the two groups despite the exposure to different diets. Free ranging goats have been described to be highly selective in their diet (Lu, 1988; Hoffman, 1989), particularly when exposed to a large variety of feedstuffs. In this way the grazing goats may have picked up a diet which was highly fermentable or comparable to concentrates and, therefore, had undergone structural changes similar to the goats on concentrates. In addition, goats prefer to browse on young succulent leaves, buds, flowers and fruits from bushes which contain less fibre and more protein and are thus highly digestible nearly similar to concentrates. This indicates that the forestomach structure of adult goats may be well developed and highly adapted to changes in feeds without necessarily involving a significant change in structure when introduced to a new feed. These factors may be responsible for the tolerance of goats to rumen acidosis or laminitis following concentrate feeding. Sudden changes in diet particularly to highly fermentable carbohydrates to unadapted cattle and sheep have been reported to be associated with the occurrence of rumen acidosis (Morrow et al., 1973; Dougherty et al., 1975; Kazer and Church, 1979) and laminitis (Mortensen and Hesselholt, 1982; Liversey and Fleming, 1984; Mgasa, 1989; Greenough and Vermunt, 1991 ). Similarly some of the goats exposed to concentrates in this study were observed to have rumen acidosis (rumen pH less than 5.4) but did not show clinical signs of rumen acidosis, systemic acidosis or laminitis. Ruminal acidosis has been induced in fistulated goats after engorgement with wheat and diarrhoea occurred within the first 5 days and thereafter diarrhoea stopped and constipation developed (Tanwar and Mathur, 1983 ). Although diarrhoea developed in one goat exposed to concentrates at 10 days, the others in the same group did not develop the condition at any stage of the experiment. Furthermore, even the affected goat was apparently normal in the first 9 days. The absence of diarrhoea in other goats and failure to develop the condition within the first week after exposure to concentrates in all goats indicates that they tolerated the concentrates well. The occurrence of diarrhoea in one goat after 1 week, may be due to other causes and not related to the concentrates. The results also show that goats may not develop clinical signs of rumen acidosis on voluntary consumption of concentrates. These observations coupled with earlier reports indicate that the goat is a

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bad model for laminitis research since it is difficult to induce the condition. However, the ability of goats to consume concentrates is a great potential which can be exploited and utilized in improving meat and milk production. Other studies (Omeke, 1988) have shown that the feeding of concentrates to goats results in high economic returns. There is a great need, therefore, in the semi-arid areas to adopt supplementation of goats with concentrate feeds in order to increase their productivity. ACKNOWLEDGEMENTS

The authors are thankful to the Danish International Development Agency for financial support. Thanks are also due to Sokoine University of Agriculture for granting study leave in Denmark to the first author. Thanks to Drs. A. Basse and K. Mortensen, Institutes of Pathology and Anatomy, respectively, the Royal Veterinary and Agricultural University, Denmark for their invaluable advice and suggestions.

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