Construction of the Karakoram Highway (KKH) has led to more rapid socio-economic change in areas close to highway than in more remote areas such as the Gilgit Ghizer Region (GGR) in Northern Pakistan. In the present study the aim was to compare the livestock enterprise in the developed region (i.e KKH) with the less developed area (i.e. GGR). A 2 x 3 factorial design was used with two geographical transects and three cropping zones and one village being studied within each cell. Nutritional inputs to, and productive outputs from, the livestock system, together with their interaction were investigated. Wheat straw (48%), lucerne (24%) and maize stover (13%) were the dominant feeds. Cereal crop residues and lucerne were main sources of energy and protein respectively. The main livestock species kept were cattle (51%), goats (31%), sheep (10%) and donkeys (8%). Overall, 65% of the herd was made up of non-productive animals. Feed sufficiency was 33% greater in the KKH transect (P < 0.05) and feed offered was 33% higher per unit liveweight in the KKH transect (P < 0.05). Stored feeds and herd weight per household were higher in the GGR transect (P < 0.05). Daily milk yield and calving rate were higher (P < 0.05) in the KKH (2.9 l/d and 0.82) compared with the GGR transect (2.3 l/d and 0.52). However proportions of fodder and cattle sold were higher (P < 0.05) in the GGR transect (16.5 % and 8%) than in the KKH transect (8.5% and <1). Overall, performance was higher in the KKH transect and this was related to herd size being better matched with feed resources. Larger herds in the GGR transect reduced animal performance but detrimental effects appeared to be partly masked by differences in the quality of summer pasture resources between transects.

The aim of the four studies reported in this thesis was to evaluate the effects of the inclusion of lupins in the diets for broiler chicks, and to evaluate any effect of enzyme supplementation on performance of birds fed lupin-based diets.  Five types of lupin were used in the studies.  Two determinate cultivars of <i>Lupinus albus, </i>Lucyane and Ludet, and two dwarf cultivars of <i>Lupinus albus, </i>Luniverse and Lucille.  One cultivar of <i>L. luteus </i>cv. Wodjil was also used.  The nutritive value of the lupins was determined by two precision feeding studies.  The value of including the lupins in diets for broilers was evaluated using two growth trails.  One trial was conducted using birds grown from 7-28 days and the other using birds grown from 0-13 days.  The use of sialic acid as a measure of endogenous losses was also investigated.  Effects of the diets on microflora in the birds gastro-intestinal tract were determined using GC profiling of the caecal contents. The five lupin types used in the study had protein levels that were similar to soyabean meal. Results of all studies indicated that the different cultivars of lupin behaved very differently, and therefore need to be considered separately in terms of which enzyme to use and levels of supplementation.  It cannot be assumed that all lupins will respond in the same way to enzyme supplementation.  The results of both growth studies showed that the two types of lupin cultivar, determinate and dwarf, respond differently to enzyme supplementation.  This is possibly due to the different routes of plant breeding. It was clear from the study that the effects of lupin inclusion, enzyme supplementation and the interactions between the two are very complex.  Further investigations of the mechanisms behind the effects are recommended.

The effects on production of milking grazed crossbred cattle (32, 53 and 74 cow and heifer dams in experiments 1, 2 and 3 in 1986, 1987 and 1988 respectively) with or without a dietary supplement (2kg dairy meal daily for 3 to 4 months post-partum) were studied in a semi-arid area of Kenya. During the second and third trials, half the calves from the milked and also the unmilked groups were creep fed for 4 months commencing approximately 1 month from birth. Herbage dry matter intake was determined four times during the wet and dry seasons between November 1988 and May 1989, and the deterministic model and computer program of the bioenergetic system of lactating and pregnant cattle of Bruce <i>et al</i> (1984) used to examine the performance of the crossbred cows, and to evaluate its potential applicability. The respective mean extracted milk yields over a six month lactation were 670.6, 414.4 and 371.2 kg for the milked and supplemented (MS) groups, and 563.4, 398.4 and 331.1 kg for the unsupplemented (MNS) groups during experiments 1, 2 and 3 (P> 0.05). Mean daily calf growth rates were affected by milk offtake (P< 0.05). They were respectively, 0.52, 0.48, 0.79 and 0.71 kg during experiment 1; 0.64, 0.61, 0.72 and 0.72 kg during experiment 2; and 0.59, 0.57, 0.66 and 0.66 kg during experiment 3 for the milked (MS and MNS) and the control groups (not milked and supplemented, NMS and the not milked and not supplemented, NMNS). Overall, post-partum supplementation improved dam liveweight gain (P< 0.05) but milk extraction tended to reduce it (P> 0.05). Similarly, calving indices were improved by supplementation while the effect of milking was inconsistent. Both creep feeding of the calves and beef genotypes of the dams were not significant (P> 0.05) factors affecting performance. Similarly, body condition scores (1 to 9 score scale) ranged between condition score 4 and 5 for all treatments. The respective mean daily dry matter intakes were 8.5 and 8.2 during the wet, and 8.6 and 8.2 kg during the dry periods; and the corresponding dry matter digestibilities were 0.72 and 0.74 in the wet, and 0.67 and 0.62 during the dry periods. The discrepancies between observed and predicted values of milk (energy), though not for liveweight, were small, consequently, with a few refinements the bioenergetic model may find a useful role in cattle production systems in the semi-arid tropics. It was concluded that the offtake of milk from suitable crossbred cattle in the semi-arid areas may be increased without significantly reducing offtake of slaughter animals.

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Tissue protein synthesis requires a simultaneous supply of energy and amino acids. The effect of altering diet and frequency of feeding on patterns of amino acid and acetate supply to peripheral tissues and the consequent effects on growth and carcass composition was investigated in growing lambs. A rumen 'asynchronous' diet with respect to the ratio of the rate of release of organic matter (OM) and nitrogen (N) was fed once daily (AD) or hourly (AR) and a more 'synchronous' diet was fed once daily (SD) to individually penned growing lambs (n=30) for 16 weeks. Plasma concentrations of acetate, amino acids and insulin were more constant throughout the day in animals fed AH compared to those fed AD. Those fed SD or AD had similar, large pulses in plasma acetate concentration following feeding. Animals fed AH had increased growth rates and greater amounts of carcass crude protein compared to those fed AD (P<O.OO1). Animals fed SD had faster growth rates with a higher amount of carcass crude protein and fat deposition than those fed AD (P>O.1). Synchronous diets formulated to have either slow (SS) or fast (FP) release of OM and N into the rumen were fed hourly (SSH or FFH) or once daily (SSD or FFD) to individually penned growing lambs (n=28) for 10 weeks. Plasma concentrations of acetate and insulin in groups fed once daily, increased after feeding, remaining elevated for longer in animals fed SSD. Amino acid concentrations decreased following feeding. Once daily fed animals tended to have greater amounts of crude protein in the carcass and generally heavier muscles than those fed hourly, particularly those fed SS. Animals fed AH had significantly higher feed intakes in the first experiment compared to those fed the diets once daily (P<O.OO1) which may be why these animals grew better and deposited more carcass protein than those fed once daily. It was thought that a pulse in acetate following feeding may contribute to an enhanced growth and carcass protein in ruminants. When sodium acetate was infused into growing lambs, intravenously, to raise the concentrations of plasma acetate similar to the pulse in acetate concentrations observed in the plasma of sheep following once daily feeding, no increase in whole-body protein synthesis was observed. The effect of temporal changes in the peripheral nutrient supply on protein synthesis in the ruminant requires further investigation.

In piglets, the post-weaning growth check is commonly associated with the weaning process that occurs within the European Union at approximately 3-4 weeks of age. The aims of the studies reported here were to investigate the contribution and importance of nutritional influences on the complex and multi-factorial problem of the post-weaning growth check in the piglet. Multi-disciplinary investigations focussed upon the relationship between post-weaning nutrition and the gut ecosystem with specific emphasis on gut physiology, immunity and microflora. The influence of dietary acid binding-capacity (ABC) on gut morphology characteristics was investigated in 20 newly-weaned piglets up to 14 days post-weaning. Piglets offered the low ABC diet displayed more rapid recovery of villus height (after a degree of villus atrophy) than control animals (P<0.001). Prior to the initial villus atrophy, villus height increased significantly throughout the experimental period for both dietary treatment groups (P<0.001; <0.001 (L); <0.001 (Q)). In control animals, villus width was greater (P=0.006) compared with treatment animals, and villus width increased over time for both groups (P<0.001; <0.001 (L); 0.014 (Q)). Crypt depth also increased temporally (P<0.001; <0.001 (L)) for both dietary groups, with treatment animals exhibiting the greatest overall dietary mean (P=0.009). No significant differences between ileal digesta pH and feed intake levels were determined. Despite the improvements in intestinal structure post-weaning, these effects were not manifested in increased performance, i.e. DLWG. The improvements in intestinal structure may not have been of significant magnitude to influence performance parameters. Dietary zinc oxide (ZnO) and avilamycin supplementation was found to exert a beneficial (although non-significant: P>0.05) effect on gut morphology; villus atrophy occurred over the initial 2 days post-weaning for animals fed ZnO, avilamycin or ZnO plus avilamycin (diets 2-4 respectively), compared to 4 days for control animals. No significant differences between intestinal coliform and lactobacilli load were established with respect to dietary treatment. Any differences observed in microflora load are most likely to be age-dependent. A positive relationship was established between dietary treatment (ZnO, avilamycin and ZnO plus avilamycin) on daily live weight gain post-weaning (P<0.001). Although not significant (P>0.05), a positive influence of dietary ZnO supplementation on feed intake levels was apparent, which may account, in part, for the enhanced growth performance. This finding was not however manifested through modifications of intestinal morphology or the lactobacilli and coliform populations studied. This further suggests that dietary ZnO may exert an effect either luminally or systemically. Further research is required to determine the mechanism responsible for the enhanced feed intake and DLWG response. The effects of feeding a yeast-based nucleotide source pre- and post-weaning revealed no significant differences with respect to villus height and width. Crypt depth was significantly greater in animals fed the treatment diet post-weaning (P<0.001). Post-weaning nucleotide-supplemented diets were found to significantly reduce intestinal coliform load (P=0.033). Such an effect was not evident in animals fed the diets pre-weaning, suggesting that the gut microflora may have adapted to the dietary regimen throughout the pre-weaning period. Lymphocyte blastogenesis assays revealed that piglets fed a yeast-based nucleotide source post-weaning might be immunosuppressed at the time weaning. Conversely, when the same diets (in terms of composition) were fed from 14 days pre-weaning (study 4), no indication of immunosuppression was evident. Since no dietary effects were apparent in either study, it is postulated that this could be a general effect of the diet per se and not the actual dietary composition. It is however also possible that the animals involved in study 4 were experiencing hypersensitivity reactions to the pre-weaning dietary antigens. These animals were also combating an E. coli infection. Additional studies are however required to identify conclusively a cause and effect relationship, and elucidate the complicated interactions between nutrition or feed intake and immunobiology in the post-weaned piglet. Implementation of dietary nucleotide-supplementation from 7 days pre-weaning through to 25 days post-weaning within a commercial environment was found to enhance significantly DLWG (P<0.001). In summary, the current work extends current knowledge and offers a greater understanding of the factors and complex process that influence the gut ecosystem and physiology in the post-weaned piglet. This thesis confirms the crucial role feed intake or, more specifically luminal nutrition, in post-weaned piglets and has highlighted key areas for future investigation.

20 Large White x Landrace sows were kept throughout 4 parities on 1 of 2 exercise treatments, free (F) or restricted (R), imposed at 2 stages of the production cycle (namely gestation and farrowing/lactation), thus giving 4 treatments: FF, FR, RF and RR. During gestation, the sows were housed in cubicles - group a being tethered while group F were allowed unrestricted movement within the cubicle and dunging area. From day 110 of gestation to weaning, all sows were kept in the same farrowing house, group R in conventional crates, group F in strawed pens. Management of the sows was otherwise identical. All farrowings were monitored with regard to the duration of parturition and stillbirth rate, while various behavioural and physiological measurements were recorded as indicators of piglet viability. Observations were also made of now behaviour at various stages of the production cycle. There were significant (P< 0.001) behavioural differences in gestation with groups R and F spending 45% v. 25% of the time lying and 27% v. 42% in manipulating straw. There were also significant (P<0.001) differences in amount and type of locomotor activity with the restricted sows making more minor movements while the free sows made more pace movements. At farrowing, all sows showed increased restlessness but group a made more leg movements and exhibited significantly (P<0.01) more straining and quivering (both pre- and intrapartum) than group F, although the latter stood and nested more frequently during the farrowing process (P< 0.001). There were no significant differences between treatments during lactation. In terms of reproductive performance, the differences between treatments were non significant, but sows in pens (group F) farrowed more quickly (a mean birth interval of 21 v. 39 minutes), produced more live pigs (11.3 v. 10.5) and fewer stillborn pigs (0.5 v. 0.8) per litter, than sows in crates (group a). Group F sows also produced piglets which had been subjected to less hypoxia as evidenced by their lower (P <0-05) serum lactic acid levels at birth (140 v. 158 m.I.U./ml) although there were no significant differences between piglets of groups F and R in times taken to breathe following birth or (53 v. 45 seconds), to suckle (36 v. 32 minutes) or in plasma immunoglobulin levels at 36 hours post partum (41.5 v. 41.7 mg/ml). Neither were there any significant treatment effects on piglet growth rate and pre-weaning mortality.