No description available.

Work with sheep indicated that fractionation of whole crop barley (WCB) further than material other than grain (MOG) and grain was of no benefit. Feeding WCB to sheep demonstrated the effectiveness of NaOH (53g/kg DM), aqueous NH₃ and anhydrous NH₃ (both 42g/kg DM) as treatment chemicals for mature (800g DM /kg) WCB, OMD being increased by around 5 percentage units for all three treatments. A laboratory scale trial indicated that aerobic stability of WCB was improved by NH₃ treatment, the optimum level being 30 to 40g /kg DM. In the work which followed WCB of between 350 and 800g DM /kg was treated with anhydrous ammonia at a level of 35g /kg DM and fed to steers of 350 kg liveweight. In cattle of this weight faecal grain loss was significantly correlated with dry matter intake (g /kg^0.75 LW). Ammonia treatment increased intake by 25% while grain loss increased from a mean of 0.177 of ingested grain for diets of 670 and 770g DM /kg to 0.284 after NH₃ treatment. Rate and extent of DM loss from whole grains incubated in the rumen were increased by NH₃ treatment of the WCB. Distribution of anhydrous NH₃ in crops < 600g DM was uneven. The final trial used steers of liveweight 150, 250 and 350 kg to test the hypothesis that smaller cattle digest whole grain more fully than do large cattle. The influence of animal size on starch digestibility coefficient was found to be significant when a multiple regression analysis was performed on the data. However faecal grain loss was still high (digestibility coefficient of starch < 0.85) for all diets and animal categories. Urea effectively preserved WCB of 675g DM /kg, the resulting material being readily consumed. It is concluded that WCB harvesting with subsequent chemical treatment, and feeding to cattle cannot be justified because of the high faecal grain loss which occurs at productive levels of intake, but the possibility does exist for inclusion in complete diets for sheep.

No description available.

No description available.

A series of experiments was carried out to study the factors affecting faecal endogenous P excretion in sheep. Experiments 3.1, 3.2 and 3.3 involved intensive balance measurements and radio-isotope (<SUP>32</SUP>P) dilution measurements made on 6 mature sheep, to study the effect of changing salivary secretion on P metabolism. A hay diet (P intake 2.2 g/d) was fed in 3 different physical forms (finely ground, coarsely ground and chopped) in experiment 3.1 and a low-P oat husk based diet was given in coarse or finely ground form in experiment 3.2. The results of both the experiments indicated that there was no change in salivary P flow, faecal endogenous P excretion and P balance within each experiment. In experiment 3.3 sheep were fed different amounts of a low-P (P intake 1.2 g/d) oat husk based diet (0.8, 1.1 and 1.4 kg/d). There were no significant changes in salivary P flow or balance position. However, in this experiment there was an increase in faecal endogenous P excretion but the size of this increase with increase in dry matter intake was less than that reported by TCORN (1989). This increase was attributed to increased secretion of P in the intestinal secretions in response to an increase in dry matter flow through the intestine. Experiments described in Chapter 4 were performed to explore the possibility of using sheep maintained by total intra-gastric infusion to measure minimum endogenous excretion of P in faeces and urine. The results indicated that sheep given a near zero P intake excrete amounts of P that are comparable with the levels predicted by ARC (1980) as minimum endogenous P excretion. Chapter 5 describes experiments carried out to investigate factors affecting intestinal P absorption in the sheep. Experiment 5.1 was aimed at studying the effect of increasing demand for P, by intravenous infusion of CaCl<SUB>2</SUB>, on intestinal P absorption. The results of this experiment showed that while the amount of dietary P absorbed is mainly determined by P intake there is a component of this system that is sensitive to changes in P requirement. There was an increase in intestinal P absorption but no change in endogenous P secretion into the gut. Three sheep surgically prepared to isolate a one-metre section of proximal small intestine were used in experiments 5.2 and 5.3. In the Experiment 5.2 sheep were given a continuous intra-venous infusion of a buffered solution of P (Na<SUB>2</SUB>HPO<SUB>4</SUB>NaH<SUB>2</SUB>PO<SUB>4</SUB>, 3g of P/d) and the loops were perfused with a solution (pH 4.5, Tonicity 280 mOsmol/litre) containing 30 mmol/litre of P. The results showed that the amount absorbed was much less during intravenous P loading. Experiment 5.3 was performed to study the absorption of P from the intestinal loops when they were perfused with solutions containing a fixed quantity of P at varying P concentrations (20 mmol/litre and 30 mmol/litre). There were no significant differences seen either in the total amount or in the absorptive efficiency between treatments. A lactation study (described in Chapter 6) was carried out to investigate the effect of feeding a high protein diet on Ca and P metabolism. Measurements were made on two groups of six ewes with one group being restricted in protein supply while the other group was given supplementary protein in the form of blood meal. Balance measurements were made over 10-day periods separated by 10-day rest periods. <SUP>45</SUP>Ca and <SUP>32</SUP>P were used to measure faecal endogenous Ca and P losses. An extra balance experiment was carried out on the second set of ewes after they ceased producing milk. The results indicated that the loss of mineral from the skeleton in ewes in early lactation is proportional to milk production and is not directly dependent on dietary protein supply or N balance. The results also suggested that the rate of repair of bone matrix and its mineralization during the post lactation period is affected by protein supplementation. Two experiments (Experiments 7.1 and 7.2) were carried out to study the effects of high dietary Ca:P ratio on faecal endogenous faecal excretion in mature sheep which were given sufficient P to meet their maintenance requirement according to ARC (1980). The results obtained showed that faecal endogenous P excretion was not significantly affected by feeding diets high in Ca. All animals had a level of salivary P secretion that was more than adequate to meet rumen microbial requirements. Experiments 7.3 was a slaughter study carried out to investigate the effects of an increase in Ca intake on growth of the young lambs fed on diets supplying just sufficient P to meet their estimated requirements based on the revised TCORN (1989) growth model. A total of 40 lambs in four treatment groups were used in this study. The results of this trial showed that feeding high levels of Ca had no adverse effects on growth of the lambs when P was adequate . There was no beneficial effect of feeding excessive Ca and P but there was an increase in the incidence of urinary calculi. The amounts of Mg retained by the lambs were lower than the levels on which ARC (1980) based their estimates of requirements.

Low birth weight has detrimental consequences for postnatal well being and survival. Therefore greater understanding of the factors that govern birth weight are important. There are many extrinsic and intrinsic factors that ensure the adequate growth of an offspring; these include maternal nutrition, maternal health, placental size, surface area and placental transport capacity. This study has used the runt pig fetus as a naturally occurring model of low weight; to better understand intrinsic factors that may contribute to low birth weight. The lightest fetuses and a normal size fetus from Large while X Landrace pig were studied at day 45,65 and 100 of gestation (term being 112-115 days). Placental sodium transport was examined. In relation to sodium transport it was observed that the short circuit current across the pig placenta was predominantly carried by sodium in a fetal maternal direction and involved both the epithelial sodium channel (ENaC) and the sodium pump This thesis is the first to report the presence of ENaC in the pig placenta. However fetal growth depends not just on the ability of the placental to grow to an appropriate size and to transfer nutrients to the fetus, but fetal growth must be appropriate to nutrient supply if the fetus is to survive to term. Therefore by looking at fetal concentrations of hormones that regulate fetal grow and differentiation we may better understand what causes low birth weight in pigs. In this thesis it was observed that no relationship existed between fetal size and fetal plasma insulin, T3 and T4 concentrations at day 100 of gestation. However low weight pig fetuses were found to have lower plasma cortisol concentration on day 45 of gestation and higher plasma cortisol concentrations of day 100 of gestation compared to their normal size littermates. Elevated cortisol concentrations on day 100 of gestation were not related to changes in fetal plasma ACTH concentrations.

Two open-circuit indirect-calorimetry ventilated hoods were built for measuring the energy exchanges of cattle nourished wholly be continuous intragastric infusions of mixtures of volatile fatty acids and casein. In Expt. 1 the energy costs of eating and ruminating oat husks were measured. The energy costs of eating and rumination were estimated to be 11.4 J/kg live weight and 9.3 J/kg live weight per minute spent eating and ruminating respectively. The energy cost of standing above that of lying was calculated to be 6.6 kJ/kg live weight per day. In the subsequent four experiments, the effect of abomasal infusions of various amount of glucose on the heat production, nitrogen metabolism and blood metabolites of Friesian steers was investigated. In Expt. 2, the abomasal infusion of 350 g of glucose/d after a five day fast, decreased the urinary nitrogen excretion to the endogenous nitrogen loss values. In Expt. 3 the infusion of glucose at low rates (16, 25 or 50 kJ/kg W^0.75/d) had virtually no nitrogen-sparing effect. In Expts. 4 and 5 the response in heat production to abomasal infusions of glucose differed between steers. Two steers had consistent heat decrements whereas one steer showed mostly heat increments. Fasting urinary nitrogen excretion was gradually reduced by glucose infusion, demonstrating the nitrogen-sparing effect of glucose. Plasma insulin was decreased during the fast in Expt. 4, but it was not affected by glucose infusion in both Expts. 4 and 5, suggesting that nitrogen-sparing is not mediated by insulin. Plasma free fatty acids and β-hydroxybutyrate concentrations were increased several-fold during the fast and were decreased by the infusion of glucose. It is concluded that the increased loss of nitrogen in fasting cattle is unrelated to a specific requirement for glucose precursors during the fast.

This study investigated the hypothesis that cattle fed to produce a lean carcass during a winter restriction period will subsequently grow faster and remain leaner than fatter steers during the summer, exploiting cheap grazed grass. Three studies were carried out; in the first study steers were restricted at three levels of growth (300, 600 and 900 g/day) during winter and turned out to graze grass during summer. At each level of growth during winter steers were fed on one of two diets aimed at producing steers of either a lean or fat carcass composition. At the end of the winter restriction period differences in lean composition were observed at the 300 and 600 g/day growth rates. Steers were slaughtered when they attained the target slaughter weight at the end of summer; but there was no difference between treatments in meat quality characteristics or fat composition. Liveweight gain during the summer period was inversely correlated to winter liveweight gain. Two further studies were carried out to assess the effect of altering carcass composition during winter, fed to a predicted growth rate of 600g/day to investigate the underlying physiological and endocrinological mechanism regulating the growth characteristics. In the first study at the end of winter steers that were fatter had higher glucose and insulin concentrations. No differences between diet treatments were detected in muscle protein synthesis or breakdown. At the end of the winter in the second experiment there were no differences in carcass composition, metabolite or hormone profiles between treatments. For both studies, at the end of summer, steers on different dietary treatments had similar carcass compositions and metabolic parameters. It was concluded that by altering the diet of steers during a winter restriction period the composition of carcass gain can be manipulated. Since steers altered the deposition of carcass protein and fat during the subsequent summer period at grass resulting in similar body compositions at slaughter it was deduced the that composition of steers at the end of winter remains unimportant. Reductions in beef production costs may be attained by restricting the growth rates during winter when commercial feeds are expensive.

The nutritive value of seed meal from <i>Camelina sativa, Lunaria biennis, Pisum sativum, Lupinus albus</i> and <i>Lupinus luteus</i> was assessed with and without the addition of exogenous enzymes for growing broiler chickens. The nutritive value of seed meal from camelina and lunaria was found to be low with apparent metabolisable energy (AME) values of approximately 8 MJ kg^-1, which is lower than would be expected for other oilseeds such as rapeseed meal. The nutritive value of camelina meal was improved by the addition of phytase and protease but the improvements were not of sufficient magnitude to compete with soyabean meal or rapeseed meal. A poorer weight gain, feed conversion and nutrient digestibility was found when camelina meal was included in the diets of growing broiler chicks compared to birds fed a diet based on soyabean meal. The inclusion of camelina meal detrimentally altered the microbial flora in the caeca and increased the secretion of endogenous material compared to birds fed a wheat/soyabean meal ration. The poor metabolisability of camelina and lunaria is thought to be due to a relatively high concentration of glucosinolates, phytate and toxic fatty acids in the seed meals which impair nutrient retention and increase endogenous losses. The nutritional value of seed meal from <i>Lupinus albus</i> and <i>Lupinus luteus</i> was found to be higher than for camelina and lunaria but poorer than would be expected for soyabean meal. AME values for both lupins were around 10 MJ kg^-1 with seed meal from <i>Lupinus luteus</i> proving to have a marginally higher nutritional value than <i>Lupinus albus</i> for broilers. The addition of a cocktail of carbohydrase and protease enzymes did not improve the nutritive value of the seed meal for poultry, both in a precision feeding study and in a growth study where lupin seed meal was included in the diets of broilers at 300g kg^-1.

The objective of the research was to assess the effects of tannins in ruminant nutrition and the ameliorating effects of polymers.  It also aimed to investigate and propose an improved method for determining concentrations of condensed tannins using the Butanol/HCl assay (Porter et al., 1986). The study has found tannins to suppress microbial growth, carbohydrate degradation and fermentation of mixed rumen microbes and of fungus.