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The utilization of Pennisetum purpureum (Napier grass var Bana) based diets and the lactation performance of dairy cows in coastal lowland Kenya was studied in a series of five experiments. In experiments 1 and 2, the effects of 300g/day additional crude protein from locally available fishmeal, copra cake and Leucaena were compared using Jersey cows fed ad libitum Napier grass. Experiment 1 carried out in early lactation, showed that supplements (fishmeal or copra cake) could increase dry matter DM intake, reduce live-weight loss and increase (P< 0.05) milk output (7.8 v 6.4kg/day) with no differences between the supplements. Experiment 2 was carried out in mid lactation. Cows fed supplements (a mixture of copra cake/maize bran or Leucaena) consumed more (P< 0.01) DM with no effect on Napier grass intake and produced more (P< 0.05) milk no difference between supplements. No significant changes in live weight were observed. Ayrshire/Brown Swiss x Sahiwal cattle were used in experiments 3 to 5. In experiment 3, the effects of Napier grassharvesting height (1.0 v 1.5m) and level of Leucaena (0,4 and 8kgFW) were evaluated in early lactation. Feeding Napier grass harvested at 1.0m compared with 1.5m increased (P&60 0.01) Napier grass intake (9.3 v 6.8kg/day), reduced live-weight losses (0.16 v 0.49kg/day) and increased milk yield (8.6 v 6.9kg/day). Feeding Leucaena (0, 4 and 8kgFW; DM280g/kg) significantly (P< 0.01) increased total DM intake (7.8, 9.3 and 10.4kg/day), reduced live-weight loss (0.53, 0.23 and 0.17kg/day) and increased milk yield (7.3, 7.7 and 8.3kg/day).

There is evidence from a number of species that body condition or fatness plays a role in the regulation of energy balance, through a direct effect on voluntary food intake (VFI). However, since differences in body condition are frequently confounded with differences in previous nutrition, this study investigated the role of both factors in the control of VFI in sheep. In ewes grazing autumn pastures, there was a negative effect of body condition on VFI, but no independent effect of the previous level of nutrition. However, there was an interaction between the effects of body condition and herbage availability on intake, since VFIs of fat ewes differed with sward height while VFIs of thin ewes did not. The effect of early nutrition on VFI in growing lambs was studied in an experiment where ewes were given either a restricted or adequate level of nutrition in late pregnancy and early lactation. Mean live weight and gut development at weaning were reduced in lambs whose nutrition was restricted during both pregnancy and lactation, but subsequent VFI was not affected. Feeding behaviour was investigated in fat and thin sheep eating a pelleted diet. Thin ewes had higher intakes and spent more time feeding that fat ewes, but the number of meals and rate of ingestion during meals was the same. Both fat and thin ewes increased meal frequency and ingestion rate when food access time was reduced. Differences in VFI were found to persist longer than differences in body condition. Basal plasma insulin concentrations and those measured following an exogenous insulin challenge were both higher in sheep that had remained fat, than in sheep that had previously been thin. This is consistent with the hypothesis that insulin may provide a long-term negative feedback signal to the brain in fat animals, resulting in lower VFIs.

The aims of the present study were to evaluate the suitability of Colombian rice polishings (RP) as a feed supplement for ruminants and to study its effect on rumen fermentation. The quality of RP appeared to be uniform and independent of the period of the year when the RP were collected. The low content of particles greater than 2 mm2 separated on sieving, combined with the low ash content suggested that the RP used in the current studies contained little broken rice or rice hulls. The proximate analysis of RP suggested a by-product which represented a good source of carbohydrates (starch), protein and phosphorus, but contained a high fat concentration (254, 143, 12.7 and 180 g/kg DM respectively). Of the total fatty acids in the oil 0.77 were unsaturated. Full-fat RP were fermented in the in vitro Menke system less efficiently than other substrates containing medium quality hay, starch or cellulose, but were apparently more degradable when measured in sacco. However, for each diet at 4, 8, 24, and 48h incubation there was a significant correlation (r2=0.97) between the amount of DM degraded in sacco and the gas production measured in vitro (P<0.01)'. The evaluation of RP in the in vitro Rusitec system indicated that any adverse effects of high lipid concentration of RP, such as the potential for an inhibition in bacterial growth, appeared to be outweighed by a nonsignificant stimulation in microbial activity resulting from the inclusion of this rapidly degradable substrate in the diet. An in vivo study with adult sheep suggested that at the level tested RP, as an alternative to urea molasses did not increase the efficiency of rumen fermentation and were not as effective a supplement with urea as molasses for a low quality forage diet. Measurements of in vitro fermentation of sieved fractions suggested that the rate of degradation in the rumen fluid decreased as particle size increased in excess of 2 mm2, in vitro batch culture results suggested that RP crude protein is highly and rapidly degraded in the rumen. In the current study RP were a rapidly degradable substrate in the rumen, represented a source of RDP and the high ammonia concentration recorded may indicate an intraruminal n recycling possibly due to an enhanced Protozoal population.

In experiment 1, groups of wild (W) and farmed (F) weaned calves were maintained at either high (H) or low housing (L) density. W calves had lower antibody titres and lower lymphocyte responses to antigen than F calves (P<0.05). At the start of the study, W and H calves exhibited a greater plasma cortisol response to ACTH than F and L calves, respectively (P<0.05), but thereafter there were no significant differences. Wild calves were less active than F calves (P<0.01) and WH calves were the most aggressive (P<0.1). In experiment 2, individual wild yearlings were grouped with farmed yearlings. Groups were remixed every week, for 4 weeks. The incidence of agnostic behaviour was greater in mixed deer than in the control deer, maintained in the same groups throughout the study (P<0.001). At the end of the study, mixed yearlings had greater plasma cortisol responses to ACTH than control deer (P<0.05). Lymphocyte response to antigen was lower in mixed than controls (P<0.05), but there were no differences in antibody response. In experiment 3, groups of weaned calves were subjected to either aversive (AV) or non-aversive (NAV) handling treatments. Lymphocyte responses to antigen tended to be lower in AV than NAV calves (P<0.05). After three weeks, AV had greater plasma cortisol responses to ACTH than NAV calves (P<0.05), but treatment had no measurable effect on fearfulness. In experiment 4, weaned calves were housed either individually (ISO) or in groups (GP). ISO were less active (P<0.001) than GP calves. Antibody and lymphocyte responses to antigen were greater (P<0.05) in ISO than GP calves. Overall, stressors associated with group-housing consistently lowered lymphocyte response to antigen, but antibody responses were less consistent. Differences in immune responses corresponded to changes in behaviour, but not productivity or cortisol response. It is concluded that social stress had a greater impact on immune function than social isolation and aversive handling.