The rôle of various classes of nutrients (energy substrates, vitamins, minerals, amino acids) in the production of wool and hair from follicles, is considered for a variety of animal species. The wool and hair follicle have evolved a number of interesting features of carbohydrate metabolism including glutaminolysis, aerobic glycolysis, significant activity of the pentose phosphate pathway, and storage and mobilisation of glycogen. Presumably the necessity to continue to produce fibre despite fluctuations in the supply of oxygen and nutrients has resulted in some of these unique features, while others reflect the high level of DNA and protein synthesis occurring in the follicle. While it is considered that energy does not normally limit fibre growth, the relative contributions of aerobic and anerobic metabolism will greatly influence the amount of ATP available for follicle activity, such that energy availability may at times alter fibre growth. Alopecia and deficient fibre growth are consistent outcomes of deficiencies of biotin, riboflavin, pyridoxine, folate and pantothenic acid, but the precise rôles of these vitamins in follicle function await elucidation. Folate, in particular appears to play an important rôle in wool production, presumably reflecting its involvement in methionine metabolism. Cholecalciferol (vitamin D) significantly alters fibre growth in cultured follicles; vitamin D receptors are located in the outer root sheath, bulb, and dermal papilla of the follicle; and alopecia occurs in humans with defects in the vitamin D receptor. Retinol (vitamin A), too, appears to influence follicle function by altering keratinocyte proliferation and differentiation, with direct effects on the expression of keratin genes. The receptors for the retinoids are present in the keratogenous zone, the outer root sheath, the bulb, and the sebaceous glands. Vitamin A may also act indirectly on follicle function by influencing the activity of the insulin-like and epidermal growth factors and by altering vitamin D activity. At present there is little evidence implicating alpha-tocopherol (vitamin E) or phytylmenaquinone (vitamin K) in follicular events. Of the minerals, only copper and zinc have been shown to have direct effects on follicle function, independent of effects on food intake. Copper has direct effects on the activity of an unidentified enzyme on oxidation of thiol groups to form disulphide linkages. Wool produced by copper-deficient sheep lacks crimp, is weak and lustrous. Copper is also necessary for the activity of tyrosinase and the tyrosinase-related proteins involved in melanin synthesis. Zinc, like copper, is required for the normal keratinization of fibres but again, the precise rôle has yet to be elucidated. While the importance of amino acid supply for wool growth has long been established, there are still some unaswered questions such as; what are the effects of amino acids on fibre growth in animals other than sheep; what are the characteristics of the amino acid transport genes and proteins operating in the wool and hair follicle; and what are the specific rôles for amino acids in follicle function.

The objective of this study was to compare two methods for analysis of longevity in dairy cattle. The first method, currently used for routine genetic evaluation in the UK, uses a linear model to analyse lifespan, i.e. the number of lactations a cow has survived or is expected to survive. The second method was based on the concept of proportional hazard, i.e. modelling the conditional survival probability of a cow as a function of time. Comparisons were based on estimated heritabilities, ranking of estimated breeding values of sires, estimated effects of covariates used in the final models, and the distribution of residuals. The same data set, 21497 observations on the number of lactations cows had survived, was used for both analyses, even in the presence of censored observations. Cows in the data were progeny of 487 sires. Heritability estimates for lifespan or survival were approximately 0·06 for both methods, using the definition of heritability on a logarithmic scale for the proportional hazards model. Correlations between breeding values for sires were high, with absolute values ranging from 0·93 to 0·98, depending on the model fitted. It was concluded that it may be justified to use the standard Weibull model even for discrete time measures such as the number of completed lactations, but that more research is needed in the area of discrete time variates.

The genetic and economic consequences of introgression of either one or two genes that explain the complete between-breed difference for disease resistance between donor and recipient breeds were investigated. Four backcross strategies (0, 1, 3 or 7 generations of backcrossing) were compared for four initial breed differences (0·1, 1, 2·5 and 5 phenotypic s.d.) when female reproductive capacity was either high (10 offspring) or lower (four offspring). Selection in donor and recipient populations was for production using a selection index. Genetic comparison was based on production level between the hybrid population, after fixation of the disease resistance alleles, and the donor population. Tor a large initial breed difference and high female reproductive capacity, application of seven generations of backcrossing resulted in the largest genetic difference between donor and hybrid populations. Introgression of one or two genes made no difference to the genetic results. From an economic point of view, optimal number of generations depends on the number of genes involved in the introgression, on the female reproductive capacity and ön the initial breed difference. Seven generations of backcrossing in most cases are too many and none to three generations of backcrossing often is more optimal. Introgression of two genes is economically less attractive, especially in case of low female reproduction capacity.

Polymerase chain reaction (PCR) primers specific to exon 2 of the bovine lymphocyte antigen (BoLA)-DRB3 gene were used successfully to amplify the equivalent region in 34 Murrah and 36 Surti buffaloes selected at random. The 304 bp amplified product of the DRB3 gene was separately digested with BstγI, HaeIII and Rsal enzymes. Digestion with BstγI enzyme did not reveal any polymorphism and all animals showed a single restriction pattern, which corresponded exactly to the BstγI pattern ‘b’ previously described for cattle. Digestion with HaeIII enzyme resulted in five patterns, four of which corresponded to the Haelll patterns previously reported in cattle. The new HaeIII pattern was observed in both the breeds of buffaloes studied. The fragment analysis with RsaI revealed 13 different patterns. All of these RsaI patterns corresponded to the RsaI patterns previously described for cattle. The high degree of similarity in the restriction fragment length polymorphism (RFLP) patterns of cattle and buffalo observed in the present study provide evidence for the strong conservation amongst other bovine species, of restriction sites previously reported in cattle.

Risk factors and variance components of pre-weaning mortality were estimated using generalized linear mixed models. Data were from 12 727 piglets born alive from 1338 litters recorded at the pig breeding farm of the University of Kiel from 1989 to 1994. Deviances due to risk factors were estimated by generalized linear model and their odds-ratios by generalized linear mixed model both with binomial errors and a logistic link. Variance components of sire, dam and litter were estimated using a logit or probit link function as well as a linear model for which estimates were transformed to the underlying continuous scale. Highest increase in deviance, indicating the risk factor, which accounts for the greatest amount of unexplained variation of pre-weaning mortality was obtained after exclusion of individual birth weight (1206) from the model, followed by year-season (217), parity-farrowing age or interval (58), genotype of piglets (56), sex (39), total number of piglets born (18) and gestation length (16). Substitution of individual birth weight successively by average piglet birth weight per litter, litter birth weight and standard deviation of birth weight within litter resulted in models with substantially lower explained variation of pre-weaning mortality. Odds of pre-weaning mortality was 1·5 times higher for males than for females and 2·0 times higher in piglets from German Landrace dams than from Large White dams. Odds increased to the fifth parity by 2·2 times the odds of the first parity or increased for the age group of dams between 850 and 949 days by 2·3 times the odds of the age group with less than 350 days. When the continuous risk factors of individual birth weight, average piglet birth weight and litter birth weight decreased or standard deviation of birth weight within litter increased by one standard deviation from the mean, the odds ratios increased by 6·0, 1·6, 0·8 and 0·4, respectively. Piglets with individual birth weights of 1·8, 1·5, 1·2 and 1·0 kg showed a rapid increase in odds ratios of pre-weaning mortality of 1·4, 2·7, 7·0 and 16·1, respectively, relative to piglets with 2·1 kg. Estimates of direct heritability for pre-weaning mortality on the linear observed, transformed underlying, logit and probit scale were 0·02, 0·06, 0·07 and 0·07, respectively. Low estimates of heritability for pre-weaning mortality, even on the underlying continuous scale, suggested low potential for improvement by selection. Therefore, selection for individual birth weight phenotypically closely associated with pre-weaning mortality was recommended to improve survival of piglets during the nursing period.

Carcass traits of two indigenous African (Sanga) breeds (Afrikaner and Nguni), one indigenous African composite breed (Bonsmara), one foreign composite breed (Santa Gertrudis) and two continental European breeds (Brown Swiss and Pinzgauer) were compared. Treatment means were adjusted to the mean overall subcutaneous fat proportion (47 g/kg). Despite differences in maturity type, only the Afrikaner dressed out significantly (P < 0·05) lower than the foreign breeds. Both Sanga breeds and the Bonsmara had significantly higher muscle yields than the Santa Gertrudis and Pinzgauer, mainly due to the high intermuscular fat of the latter two breeds. When muscle yield was expressed per unit of bone, the Afrikaner and Bonsmara compared favourably with the larger breeds, due to their low bone and intermuscular fat yield, while the Nguni had a relatively high bone yield. The Santa Gertrudis had the lowest muscle yield due to its high bone and intermuscular fat yields, especially when compared with the smaller Bonsmara composite. Both Sanga breeds had significantly higher (P < 0·05) proportions of total weight, meat and bone (Afrikaner P > 0·05) in the high-priced cuts compared with the other breeds at the same subcutaneous fat level. Despite the statistical significance, differences were small in magnitude and probably of little commercial value. At the same time mean subcutaneous fat proportion, tissue yield and distribution patterns expected of late maturing breeds were observed for smaller indigenous breeds, suggesting that it was specific breed effects rather than maturity type effects, which were evident.

Forty-five Talaverana breed sucking lambs of both sexes were slaughtered at 10 and 12 kg live weight in order to study the effect of gender and slaughter weight on carcass, meat and fat traits. Carcass dressing proportions and fatness (by various measures) were higher in females and heavier lambs, which also showed better conformation. Lightness (L*) of the carcass fat was higher in males and heavier lambs. Females and heavier lambs also displayed a greater proportion of fat on dissection, primarily due to a higher percentage of subcutaneous fat tissue. Water-holding capacity was greater in males and in lower-weight lambs. Males presented higher total collagen and lower soluble collagen values than females. In general, a high percentage of short-chain (C12:0 and C14:0) fatty acids, as well as of palmitic acid (C16:0), was observed in the intramuscular fat of the longissimus dorsi muscle, corresponding with an exclusively milk diet.

Two experiments were conducted to determine the nutritive value of extruded or raw peas (Pisum sativum as an energy and protein supplement for pigs of 33 to 100 kg live weight. Experiment 1 determined the effects of extrusion on the nutrient apparent digestibility of peas when included at 200 g and 400 g/kg in the diet. In experiment 2, performance was determined in individually fed pigs (no. = 70) offered diets ad libitum including a control (no peas, T1), 200 g/kg raw peas (T2), 400 g/kg raw peas (T3), 200 g/kg extruded peas (T4), 400g/kg extruded peas (T5). The peas were extruded at 120°С for 30 s. All diets were formulated to have similar concentrations of digestible energy (DE) and total lysine. There was a significant interaction effect (P < 0·05) between level of peas and extrusion on the digestibility of the organic matter (OM), nitrogen (N), energy and the DE content of the peas. The inclusion of 400 g/kg raw peas led to a lower estimated digestibility of OM (P < 0·001), N (P < 0·001), gross energy (P < 0·05) and DE content (P < 0·05) of the peas compared with the 200 g/kg peas. However, there was no difference (P > 0·05) between the digestibility of the 200 and 400 g/kg peas when the peas were extruded. In experiment 2, there was a significant interaction (P < 0·05) between the level of peas in the diet and extrusion. As the level of raw peas increased from 200 to 400g/kg, growth rate decreased (P < 0·01) and food conversion ratio (FCR) increased (P < 0·01). However, as the level of extruded peas was increased from 200 to 400g/ kg, there was no difference in either growth rate or FCR. It is concluded that extrusion of peas improved the nutrient digestibility and improved overall gain and FCR of the pigs.

Three diets were formulated according to the nature of the fibrous components: a concentrate low fibre diet enriched in starch (diet S, neutral-detergent fibre (NDF) proportionately 0·078 of dry matter (DM)) and two high-fibre diets enriched in either sugar-beet pulp (diet BP, NDF = 0·219 of DM) or wheat bran (diet WB, NDF = 0·187 of DM). In a first experiment, the digestibility of nutrients in these diets were determined using dry sows. In a second experiment, 24 multiparous Large White sows were offered the experimental diets in a 3 x 3 Latin-square design during three 21-day periods over pregnancy in order to evaluate physiological and behavioural effects over the nycthemeral period. On the basis of the first experiment, the daily food supply was adjusted to 2·44, 2·74 and 2-90 kg/day for diets S, BP and WB, respectively, to provide the same amount of metabolizable energy to each treatment. In the hour prior to the meal, the diet effect was nil on plasma levels of glucose, insulin, glucagon and non-esterified fatty acid and limited on cortisol plasma level. After the food delivery, the peak responses of glucose and insulin to the meal were delayed in sows given the BP diet, while their level showed a higher increase for S than for WB and BP diets. Sows offered diet BP spent less time standing than sows offered diet S. The occurrence of non-feeding oral activities over the 45 min following food distribution was significantly reduced with fibrous diets. But no difference appeared during the 45-min period following the end of each meal. It was concluded that the incorporation of beet pulp in the diet was more effective than wheat bran in extending the feeding activity and the absorption of nutrients. The diet effect was limited to the 2 h after the food delivery for these sows given a restricted amount of food.

Two similar experiments (1 and 2) were conducted to measure the effects of a range of dietary threonine concentrations and environmental temperatures on the performance of pigs grown from 13 to 25 kg live weight. In both experiments 48 Large White x Landrace entire male pigs were assigned at 13 kg to one of six dietary threonine treatments (8·9 (T1), 7·6 (T2), 6·2 (T3), 4·9 (T4), 3·6 (T5) g/kg and T5 + supplemented threonine (T6)) and one of four temperature treatments (18, 22, 26 and 30°C). Animals were given ad libitum access to food until 25 kg live weight. There were significant interactions (P < 0·05) between temperature and threonine content on the rate of growth (ADG) with the highest gains on T1 and at 22°C. Similarly the response in food intake (FI) to dietary threonine was significantly (P < 0·01) modified by the ambient temperature. An increase in the supply of threonine in the diet resulted in significant increases (P < 0·001) in the gain per unit of food (FCE). A similar response to temperature occurred with the highest FCE recorded at 26°C and the lowest at 18°C. There was a 0·20 proportional reduction in body protein content at 25 kg live weight in pigs given T5 compared with those given T1 and similarly, excluding T6 because threonine may not have been the most limiting amino acid, the fat content was 1·37 higher for pigs on T5 versus T1, which had the lowest fat content. Similar trends occurred in protein and lipid growth rates with maximum protein deposition recorded on T1 (86 (s.e. 3·5) g/day) and maximum lipid deposition on T5 (108 (s.e. 5·8) g/day), over all temperatures. The response in total heat loss was similar to that observed in FI with the effect of decreasing threonine content being dependent on the environmental temperature. Linear regression of daily empty body threonine accretion on daily digestible threonine intake showed an average efficiency of threonine utilization for pigs between 12 kg and 25 kg live weight of 0·59 (s.e. 0·03). There were no differences in efficiency between temperatures. In conclusion, decreasing the threonine concentration below the requirement of the animal ‘resulted in a significant decrease in ADG, reduced FCE and fatter animals. Pigs given a diet deficient in threonine will attempt to maintain threonine intake as the concentration declines by increasing food intake but this compensation is dependent on the environmental temperature. Pigs are able to compensate better for a deficiency in threonine at 18°C and 22°C than at higher temperatures due to the animals being able to dissipate more heat at the lower temperatures.

Two experiments were conducted to measure the effects of a range of dietary lysine concentrations and environmental temperatures on the performance of pigs grown from 13 to 25 kg live weight. In both experiments 48 Large White x Landrace entire male pigs were assigned at 13 kg to one of six dietary lysine treatments (13·8 (L1), 11·8 (L2), 9·6 (L3), 7·6 (L4), 5·6 (L5) g/kg and L5 + supplemented lysine (L6)) and one of four temperature treatments (18, 22, 26 and 30°C). Animals were given ad libitum access to food until 25 kg live weight. There were significant differences in the rates of growth between dietary and temperature treatments with the highest gains on L2 (0·597 (s.e. 0·020) kg/day) and at 18°C (0·549 (s.e. 0·018) kg/day). Food intake (FI) increased significantly (P < 0·001) with decreasing lysine content, reached a maximum (L4) and then declined (L5). An increase in the supply of lysine in the diet resulted in significant increases (P < 0·001) in the gain per unit of food (FCE). There was an indication (P < 0·10) that the response in FCE to dietary lysine was dependent on the temperature, with maximum FCE being obtained at 22°C on LI (647 (s.e. 18·5) g gain per kg food). Dietary treatment had a significant effect (P < 0·001) on both the rate of protein (PR) and lipid deposition (LR) irrespective of the temperature. There was a 0·60 reduction in PR and a 1·36 increase in LR in pigs given L5 compared with those given L1. Similar trends occurred in the empty body protein and lipid contents at 25 kg live weight. Both temperature and dietary lysine levels had a significant (P < 0·05) effect on total heat loss (THL). The response in THL was similar to that observed in FI. The efficiency of lysine utilization at 22°C was significantly (P < 0·05) higher than at the remaining temperatures. The mean efficiency for pigs between 13 kg and 25 kg live weight was 0·64 (s.e. 0·05). In general, growth and food intake responses to dietary lysine level were independent of environmental temperature.

Two trials were conducted to examine the influence of dietary oil type and rate of inclusion on fatty acid profiles of adipose tissue and eating quality of griddled pork. Trial 1 was based on three sources high in specific fatty acids: palm oil (palmitic acid), tallow (stearic acid) and linseed oil (linolenic acid) each at three rates of inclusion (palm at 44·6, 88·7 and 133·3 g/kg; tallow at 44·1, 87·6 and 131·7g/kg; linseed oil at 40·1, 79·8 and 120·0g/kg into a synthetic fat-free diet. Trial 2 was based on systematic replacement of soya-bean oil (incorporated at a rate of 0, 34, 69 and 104 g/kg diet) with olive oil (rate of 62, 46, 29 and 13 g/kg diet) to alter dietary concentrations of oleic acid. Diets were offered to pigs over the live-weight range 55 to 90 kg. Samples of subcutaneous fat were analysed for fatty acid composition and samples of loin assessed for meat quality with taste panels. There were no significant effects (P > 0·05) of treatment on daily live-weight gain, food conversion ratio or gross carcass composition, with the exception of anterior loin fat for trial 1 (P < 0·05) although not in a manner that was consistent between treatments and, in trial 2, anterior loin fat, minimum loin fat and posterior loin fat (all P < 0·05) but, again, not consistently between treatments allowing no meaningful conclusions to be drawn. Fatty acid profiles of adipose tissue reflected dietary levels to a variable degree, the more so with oleic acid and the greatest for linoleic and linolenic acids. The quality of the pig meat as measured by sensory analysis was related to the fatty acid profile in the situation where the most extreme changes in fatty acid profile occurred, as was apparent for the diets based upon linseed oil. No other major influences on meat quality were obtained.

The effects of work stress and dietary supplementation on ovarian activity were determined in 16 multiparous Mashona cows in Sanyati Communal Area, which lies in a semi-arid environment of Zimbabwe. The cows were assigned to one of four treatments: supplemented working (SW), supplemented non-working (SNW), non-supplemented working (NSW) and non-supplemented non-working (NSNW) cows in a 2 × 2 factorial treatment arrangement with two dietary and two work levels. Cows in the SW and NSW groups pulled a cart with a 200-1 water drum for 18 km (9 km with drum empty, 9 km with drum full) every day for 5 days/week for a total of 12 weeks.

Rectal temperatures were recorded at specific points along the route to and from the river where the water was obtained. Blood samples were collected by jugular venipuncture once a week, before working, for the determination of plasma glucose and non-esterified fatty acids (NEFA). In addition, blood samples were collected once every 3 days for the determination of progesterone concentration. There were no differences (P > 0⋅05) in the rectal temperatures between SW and NSW cows. Cows in the NSW group had the highest decrease in glucose levels and also showed marked increases in NEFA concentrations. The incidence of ovarian activity was similar between SNW and SW cows (P > 0⋅05). The incidence of ovarian activity was least in NSW cows. We conclude that nutritional stress was more important in suppressing ovarian activity than work stress and that dietary supplementation can reduce the negative effects of draught on ovarian activity.

Two silages were made from a regrowth of perennial ryegr ass following a 24-h wilt using either 2·5 l/t (LF) or 5·5 l/t (HF) of Add Safe (an aqueous solution of ammonium tetraformate, Trouw Nutrition, Cheshire, UK). Composition of silages LF and HF respectively were for dry matter (DM, g/kg) 205, 217; crude protein (g/kg DM) 106, 104; digestible organic matter (g/kg DM) 665, 692, pH 3·8, 3·9; lactic acid (g/kg DM) 103, 84; neutralizing value (meq/kg DM) 1051, 892; acetic acid (g/kg DM) 18·4, 14·0. Experiment A measured the intakes of the two silages using 12 Scottish Blackface wether lambs (mean live weight 25 kg) using a cross-over design with periods of 21 days. Intakes (g DM per day) were significantly greater (P < 0·05) for silage HF (329) than for LF (268). Experiment B measured the voluntary intakes of dried silage residues following juice extraction using the same protocol as for experiment A, except that only six lambs were used. There were no significant differences in composition or intake (P > 0·05) of the dried residues from the two silages. Experiment C used a 5 × 5 Latin-square design to measure the effects on voluntary intake of adding juices from the two silages to unmolassed sugar-beet nuts (SBN) pre-feeding or administered directly into the rumen in two discrete doses per day. Sheep on treatments LED and HFD received juices added to SBN (1·5 l/kg) and water added into the rumen in equal volume to the juice consumed with the previous day’s SBN. Treatments LFR and HFR received water added to the SBN (1·5 l/kg) and juice into the rumen in equal volume to the water consumed with the previous day’s SBN. The control treatment (W) was water added both to the SBN and into the rumen. Total mean daily intakes (g/day) were 1930,1954,1296, 2034 and 1703 (s.e.d. 179) for treatments LED, HFD, LFR, HFR and W respectively. Treatment LFR gave significantly lower mean daily intakes (P < 0·05) than all other treatments. Values for pH, volatile fatty acids and ammonia in the rumen fluid were not significantly affected by treatment (P > 0·05). Differences in voluntary intake for the two silages made from the same crop using different ensilage methods were attributed to differences in the silage liquid and volatile phases and not to the non-volatile solid phase. The effects of juice composition on intake were greater when added directly to the rumen than when added to the diet suggesting that effects on taste or smell were relatively unimportant.

European (no. = 36) and hybrid (¼ Mesopotamian, ¾ European; no. = 36) fallow deer (Dama dama) were evaluated for weight gain and energy intake from 10 to 21 months of age. Twelve each of bucks, does and castrated males (haviers) were tested for each genotype, in both concentrate-fed and pasture-based feeding systems. Based on weekly weighing hybrids (H) in each of the sex classes grew more rapidly (5 g/day across all groups) than the European (E) fallow deer (P < 0·05). Haviers given concentrates grew significantly faster than pasture-fed haviers (P < 0·01), whilst does grown on pasture grew significantly faster than those given concentrates (P < 0·01). There was no significant difference in pattern of growth between bucks on pasture and those given concentrates (P > 0·05). Does grew significantly less (P < 0·01) than bucks and haviers in spring, summer and winter but environmental differences between years could not be accounted for in the analysis.

Animals of all sexes and genotypes experienced rapid growth from 10 to 12 months of age (spring) and this was associated with energy intakes according to metabolic body weight (M0·75) these ranging between 0·8 and 1·1 MJ metabolizable energy (ME) per kg M0·75 per day. There were significantly (P < 0·01) higher levels of energy consumed by H does and haviers in the summer, compared with their E counterparts but this was not associated with greater growth rates. However, H does had significantly higher (P < 0·01) dressing proportions at slaughter than E does. The energy intake on a metabolic body weight basis for most groups declined to between 0·7 and 0·8 MJ ME per kg M0·75 per day from 12 to 21 months of age, except for the does, which declined even further to between 0·5 and 0·6 MJ ME per kg M0·75 per day from 17 months of age.

There were no significant differences between E and H deer for energy intakes per M0·75, and H deer were slightly more energy efficient than their E counterparts in terms of growth rate in relation to annual gross energy intake. The food intake : weight gain ratio increased considerably for both genotypes after 14 months of age, indicating the desirability for slaughtering as soon as animals reach the target live weight. It was concluded that the crossbreeding system described is production efficient and produced offspring that reached slaughter weight sooner than E fallow deer and thereby produced carcasses with a greater wholesale value than their E counterparts of the same age.

Leptin is thought to act on the central nervous system as an important regulator of food intake and body weight in mice. To examine the actions of leptin in sheep, we injected recombinant mouse leptin into the lateral cerebral ventricle of ewes. Six ewes were intracerebroventricularly cannulated and given free access to forage and water. The ewes were injected with phosphate-buffered saline (PBS) as a vehicle for 5 days through the cannula and then with PBS + leptin for 7 days consecutively. Although food intake and body weight did not change during PBS injection, the administration of leptin decreased food intake and body weight. Plasma glucose levels decreased and plasma non-esterified fatty acid levels increased on the last few days of leptin administration. Approximately 2 weeks after normal food intake was recovered, the amount of diet was individually reduced in accordance with the recorded food intake during the leptin administration in each sheep. During food restriction, body weight and plasma metabolite concentrations were similarly changed as during the leptin-administration period. These results indicate that leptin decreases food intake in sheep. Moreover, it is likely that the changes in body weight and plasma metabolites were mainly induced by the suppression of food intake during leptin injection.

Seventy high genetic merit Holstein heifers were used in two experiments to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period and (2) the effects of plane of nutrition during the post-pubertal period on metabolic hormone concentrations, growth and milk production. In experiment 1, treatment 1 and 2 heifers were given food to achieve a live-weight gain of 0·70 and 0·95 kg/day from 3 to 10 months of age on a grass silage based diet, while treatment 3 heifers were given food to achieve 0·95 kg/day on a barley straw/concentrate diet. During the pre-pubertal period, heifers reared on treatment 1 had significantly higher growth hormone(GH) concentrations (ng/ml per 1 h) than heifers reared on treatment 2 (P < 0·01) and had significantly lower insulin concentrations than heifers reared on treatment 3 (P < 0·01). Heifers reared on treatment 1 had significantly lower insulin-like growth factor 1 (IGF-1) concentrations than those reared on treatment 3 (P < 0·01). At 10 months of age heifers reared on treatment 1 were of lower condition score (P < 0·01) than those on treatment 2 and had a smaller heart girth diameter (P < 0·01) than those on treatments 2 and 3. During the first lactation, milk yield and composition produced by the heifers was not significantly affected by treatment. In experiment 2, treatment A heifers were given, from 14 to 24 months of age, a low plane of nutrition to allow a live-weight gain of 0·65 kg/day on a grass silage and grass based diet during the winter and summer periods respectively. Treatment B heifers were kept on a high plane of nutrition to allow a live-weight gain of 0·90 kg/day on the same forage along with concentrate supplementation. During the rearing period, GH and IGF-1 concentrations were not significantly affected by treatment. Treatment A heifers weighed less before calving (P < 0·05), had a lower condition score (P < 0·01), and had a smaller heart girth diameter (P < 0·01) than those on treatment B. During the first 10 weeks of lactation, heifers on treatment A had a higher silage dry matter intake and lost less weight (P < 0·05) than those on treatment B, however, by 20 weeks of lactation these effects had disappeared. Milk yield and composition during the first lactation were not significantly affected by treatment. Overall, the findings of experiments 1 and 2 did not show any beneficial effects of higher weights at first calving in high genetic merit Holsteins and therefore indicate that accelerated growth in the pre- or post-pubertal period may not be required.

This study compared the effect on foetal growth of shearing ewes in very early pregnancy (day 50) with the effect of shearing later in pregnancy (day 70 or 100). One hundred and sixty ewes were allocated at day 49 of pregnancy to four ‘time of shearing’ treatments — pregnancy day 50 (P50), P70, P100 (no. = 45 ewes per treatment) and unshorn (shearing of this group occurred 43 days after weaning) (no. = 25); two methods of shearing (by standard comb and cover comb); and two levels (1 or 2) of pregnancy/rearing rank. All ewes had been mated over a 28-day period and grazed pasture throughout the trial. The mid point of lambing was 27 August 1996. Live weights of ewes (corrected for fleece weight) were not influenced by shearing time at any stage except at day 45 of lactation when ewes shorn at P50, P70 or P100 were about 3⋅0 kg lighter than unshorn ewes. Shearing method had no effect on ewe live weight. Time of shearing and shearing method had no effect on ewe greasy fleece production or wool tensile strength. Shearing significantly (P < 0⋅05) influenced the birth weight of single- (by 0⋅7 to 0⋅8 kg) but not twin-born lambs. Maternal plasma triiodothyronine concentration increased proportionately by 0⋅47 to 0⋅85 (P < 0⋅05) and lasted for at least 20 days in response to shearing irrespective of time of shearing. No difference in plasma insulin concentration was detected between shearing groups but plasma glucose concentration proportionately increased by 0⋅06 to 0⋅16 (P < 0⋅05) for 10 to 20 days after shearing. These results indicate that shearing between day 50 and 100 of pregnancy can increase lamb birth weights and that the response is associated with an increase in thyroid hormone concentrations in the maternal circulation.