Thirty-one newborn lambs were allocated to four treatments involving subcutaneous or slowly administered intravenous injections of noradrenaline (a natural predominantly a-agonist) or isoprenaline (a synthetic pure ($-agonist). The thermogenic effect of these treatments, attributed to brown adipose tissue, was assessed by changes in metabolic rate and rectal temperature. The objective was to define the optimum treatment for studying genetic variation between lambs in the thermogenic activity of brown adipose tissue. After all treatments, metabolic rate increased significantly by about 7 W/kg to a peak averaging 2·3 times the resting metabolic rate. Rectal temperature increased significantly by about 1°C. Both drugs administered at 150 [ig/kg were similar in potency with noradrenaline producing slightly, but not significantly, greater responses; subcutaneous injections gave significantly larger and more prolonged responses than intravenous injections. Subcutaneous isoprenaline produced the longest sustained response with peak metabolism difficult to define. Subcutaneous noradrenaline injections provided the simplest satisfactory treatment for large scale experiments.

Four groups each of 14 sheep aged 11 to 13 months comprising outbred (O) and inbred (I, inbreeding coefficient 0·37 or 0·5) sheep reared on either a low plane (L, maintenance) or on a high plane (H, ad libitum) of nutrition from the age of 6 months were exposed first to acute cold and 1 week later to heat. Exposures in climate chambers ended for each sheep when rectal temperature decreased to 36°C (in the cold) or increased to 42·5°C (in the heat) subject to a limit of 8 h. Throughout the experiment, sheep were kept in matched quartets comprising one sheep of each type.

The average cold resistance times (min) were 161, 267, 348 and 381 for the LI, LO, HI and HO groups respectively, showing a significant effect of both inbreeding and plane of nutrition (P < 0·01). Five sheep in the HO group lasted the full 8 h in the cold chamber with little or no reduction in rectal temperature. Skin temperature at the mid side was significantly higher in L than in H sheep throughout cold exposure, but there was no effect of inbreeding.

Respiration rates were much higher before and during cold exposure in the H sheep, but there was no effect of inbreeding.

The residual correlation of cold resistance with live weight was 0·58, but differences in live weight do not explain all the differences in cold resistance and particularly do not explain the rapid decrease in rectal temperature of the LI sheep. It was concluded that under cold exposure a high level of nutrition was able to compensate partly for the disadvantages of inbreeding, and that outbreeding was able to compensate partly for the adverse effects of poor nutrition.

With heat exposure, there were no significant differences among the four groups in heat tolerance time, but within the 1st h, H sheep had slightly higher rectal temperatures and much higher respiration rates than L sheep. Inbreeding affected only the time taken to reach a respiration rate > 200 per min, which was longer in I (131 min) than in O sheep (113 min) and longer in L (149 min) than in H animals (96 min).

From each of 159 litters, between one and three pigs were fed ad libitum and between one and four pigs were fed at several restricted feeding levels from about 27 to 107 kg live weight. Effects of litter by feeding regimen (ad libitumv. restricted feeding) interactions (L × F) and sex by feeding regimen interactions (S × F) on production traits were investigated. In experimental groups where restrictedly fed animals received an amount of food based on their estimated voluntary food intake capacity (FIC), interactions were non-significant. In groups where restricted feeding was independent of FIC, significant L × F or S × F interactions were found for daily food intake (FI), daily gain, lean tissue growth rate and fatty tissue growth rate, but not for body composition and food conversion traits.

Because of between-animal variation in FIC, restricted feeding according to a fixed scale restricted intake of some animals to a higher degree than others and degree of food intake restriction (DFR) was calculated from actual FI and FIC for animals fed at a restricted level. After correction of FI and production traits of restrictedly fed animals for differences in DFR, L × F and S × F interactions were not significant.

It was concluded that the poor relationships often found between test-station results of boars and results of their progeny in practical environments may be caused, to an important extent, by differences in DFR in each environment. To overcome these genotype by environment interactions it is recommended that animals be fed ad libitum in both test and commercial environments.

We hypothesised that (i) increased feeding motivation will cause sheep to move further apart as a result of individuals trying to find food and (ii) in conditions of high food availability, sheep will move less and show greater social attraction. The effects of both feeding motivation and food availability on spatial distribution was examined in eight groups of food-deprived (high feeding motivation) and satiated (low feeding motivation) sheep in good or poor food resource plots in a 2 × 2 design. Distance travelled was assessed using Global Positioning System collars, grazing time using scan sampling and social cohesion using proximity collars that record the number and duration of encounters within 4 m. Food-deprived sheep in the good-resource plots grazed the most, whereas satiated sheep in the poor-resource plots grazed the least (P = 0.004). Food deprivation had no significant effect on the number or duration of encounters and feeding motivation appeared to have little effect on spatial distribution. Contrary to expectation, sheep had more encounters (P = 0.04) of a longer total duration (P = 0.02) in poor-resource plots than in good-resource plots, indicating that sheep were showing more social cohesion if food was scarce. Our findings suggest that when food is scarce, animals may come together in an attempt to share information on food availability. However, when a highly preferred food is abundant and well dispersed, they may move apart in order to maximise the intake. It is concluded that the particular details of our experiment, namely the even distribution or absence of a highly preferred food, affected spatial distribution patterns as sheep tried to find this food and maximise the intake.

Changes in progesterone levels in milk and in milk fat were measured by radioimmunoassay in nine crossbred cows for 40 days after insemination. On average, progesterone in milk was minimal: 1·10μg/l at the morning milking (M) and 1·63μg/l at the evening milking (E) on the day of oestrus; this increased to 15·72 μg/l at M and 22·8 μg/1 at E on day 13 after insemination, and thereafter declined to 0·99 μg/l at M and 1·12μg/l at E on the day that the next oestrous cycle commenced in non-pregnant cows. In pregnant animals the level was maintained, and fluctuated from 1505 to 19·60μg/l at M and 18·09 to 23·01 μ/1 at E up to 40 days of pregnancy.

The average progesterone concentration in milk fat was 18·9μg/l at M and 24·1 μl at E on the day of oestrus, and rose to a peak of 141·7μ/l at M and 153·8μg/1 at E on day 13 after insemination. It continued to increase and fluctuated between 160·6 and 195·8μg/l at M, and 161·1 and 225·6μg/l at E, in pregnant animals, but dropped to 12·0μg/1 at M and 16·7 μg/l at E on the day of the succeeding oestrus in those animals which failed to conceive. Progesterone concentration in milk and in milk fat was significantly higher in evening samples than in morning samples (P<0·05).

Data from two selected lines of pigs in closed herds of a breeding company were collected over a 5-year period. The lines were selected for growth rate and leanness and were housed together in the same environment. Animals were performance tested from 35 kg for about 58 days, and were fed individually according to a scale determined by time on test; the boars were more liberally fed than the gilts. At the end of test, average daily gain (ADG) values were calculated and ultrasonic measures were taken of fat depths at the shoulder (SF), loin (LF) and last rib, 4·5 cm (CF) and 8 cm (KF) off the mid line.

Estimates of heritabilities, phenotypic and genetic correlations were obtained from paternal half-sib analyses. All heritability estimates were significantly different from zero and ranged from 0·18 to 0·42 for ADG and from 0·21 to 0·59 for fat depths. The genetic correlations between ADG and fat measurements in boars of the two lines were not significantly different from zero, averaging 0·08; in the gilts they were negative, averaging –0·39.

After long-term selection, appreciable genetic variation remained in the closed lines studied here for growth rate and fat depths. Although sex and feeding level were confounded, it is likely that the genetic correlation between growth rate and fat depth was influenced by the level of feeding and associated with partitioning of energy between lean and fat deposition.

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.

Lifetime productivity of 408 Aberdeen Angus cows from the Estacion Experimental Agropecuaria (EEA) of Balcarce, Argentina, was analysed during the 1972 to 1983 period according to their date of calving. Cows were allocated to two groups: one group of early first calving (Fl) when cows calved within the first 25 days of the calving period; the other, of late first calving (F2) when cows calved after that date. Independently using similar criteria, the effect of date of second calving on lifetime productivity was analysed in the same cows, groups SI and S2. Early first calving cows weaned more kg of calf when their first four calvings were considered than cows of late first calving (659 v. 628 kg). The same tendency was observed when cows were compared according to their second calving date (653 v. 634 kg). Differences in weaning weight between calves from early and late cows were only significant for the first calving (group Fl v. F2) and for first and second calving (group SI v. S2). This fact was a consequence of the shorter initial calving interval for late cows (F2 and S2) so that subsequent ages of their calves at weaning were similar to early cows (Fl and SI). Groups F2 and S2 cows had first and second calving intervals respectively of 351 and 356 days, while groups Fl and SI cows had intervals of 372 and 371 days. It is concluded that the date of the first calving and the high overall reproductive performance of the herd contributed to a high concentration of early calvings and a high productive efficiency.

The gestation lengths of cattle are considered in terms of variation due to the month in which calving occurs. The well-known summer decrease in gestation length is re-established but in addition there is a short-term decrease in April which appears to be related to the cattle being put out to grass at a late stage of pregnancy after they have been housed for the winter.

In this study, the economic values for production and functional traits of dairy sheep are estimated through the application of a profit function model using farm-level technical and economic data. The traits incorporated in the model were milk production, prolificacy, fertility, milking speed, longevity and mastitis occurrence. The economic values for these traits were derived as the approximate partial derivative of the specified profit function. A sensitivity analysis was also conducted in order to examine how potential changes in input and output prices would affect the breeding goal. The estimated economic values of the traits revealed their economic impact on the definition of the breeding goal for the specified production system. Milk production and fertility had the highest economic values (€40.30 and €20.28 per standard genetic deviation (SDa)), while, mastitis only had a low negative value of −0.57 €/SDa. Therefore, breeding for clinical mastitis will have a minor impact on farm profitability because it affects a small proportion of the flock and has low additive variance. The production traits, which include milk production, prolificacy and milking speed, contributed most to the breeding goal (70.0%), but functional traits still had a considerable share (30.0%). The results of this study highlight the importance of the knowledge of economic values of traits in the design of a breeding program. It is also suggested that the production and functional traits under consideration can be categorized as those which can be efficiently treated through genetic improvement (e.g. milk production and fertility) while others would be better dealt with through managerial interventions (e.g. mastitis occurrence). Also, sub-clinical mastitis that affects a higher proportion of flocks could have a higher contribution to breeding goals.

Alternative Norwegian sheep breeding schemes were evaluated by stochastic simulation of a breeding population with about 120 000 ewes, considering the gain for an aggregate genotype including nine traits and also the rate of inbreeding. The schemes were: a scheme where both young unproven rams (test rams) and proven rams (elite rams) are used in artificial insemination (AI scheme), a scheme with test rams in natural mating in ram circles and elite rams (from one and a half years of age) in AI across all flocks in the country (NMAI2 scheme), a scheme where, in addition to testing rams, the youngest elite rams (one and a half years of age) are also used in natural mating in ram circles, while older elite rams are used in AI (NMAI1 scheme), and a scheme, acting as a control, where both test and elite rams are used in natural mating (NM scheme). Within the NMAI- and AI-schemes, experimentation was performed for percent ewes inseminated to elite rams v. test rams (EM%), numbers of ewes inseminated per elite ram (EAIn), and numbers of ewes mated per test ram by natural service (TNMn) or by AI (TAIn), respectively. With a restriction on the rate of inbreeding (⩽0.8% per generation), the AI scheme gave similar gain to the NMAI2 scheme (and about 40% more than did the NM scheme). Less gain was generated by the NMAI1 scheme, but it was still considerably more than for the NM scheme (about 25%). In the AI scheme, relatively few ewes (200/300) should be inseminated to each test/elite ram, and a low EM% should be chosen (10%). In the NMAI schemes, TNMn should be relatively high (40 to 50), combined with average and somewhat larger than average EAIn (NMAI2: 700 ewes, NMAI1: 900 ewes), and EM% medium (30%).

Year, type of gestation (single or twin foetuses) and age of foetus all had highly significant independent effects on both foetal weight and length (P>0·01). Twin foetuses were both longer and heavier than single foetuses at 21 to 30 days post coitum. Continuous illumination, continuous darkness and intermittent light appeared to reduce foetal length and weight (P>0·05). Control foetuses were longer and heavier than those on other treatments. Neither feeding level (75 to 150% N.R.C. maintenance requirements) nor body weight of the dam had significant effects on foetal size within the age range studied.

Each of seven diets containing different proportions of separated milk and barley meal, supplemented with minerals and vitamins, was given to five groups of four pigs. The ratios of barley to milk solids were such that the crude protein of the dry matter given to pigs of 20 to 40 kg live weight ranged from approximately 15 to 21%. Within each treatment, the proportion of milk was gradually adjusted so that the crude protein level was reduced by 3% over the live-weight range 40 to 91 kg. Daily energy allowances of all pigs were governed by the same scale.

The total dry matter consumed by the pigs had mean total lysine levels of from 0·52 to 1·18% (approximately 0·1% lysine between successive treatments).

Pigs on the lowest level of milk grew more slowly and had poorer feed conversion than other animals.

Percentage dissectable lean in the trimmed side was highly correlated with lysine level. Within the range studied, each 0·1% increase in lysine increased lean by 0·69% and caused decreases in fat thickness. The performance of the milk-fed pigs was compared to controls given a standard all-meal diet.

Nitrogen metabolism trials were carried out on the milk diets. Beneficial responses in terms of nitrogen retention were found up to the highest level of milk given to pigs between 16 and 90 kg live weight.

An in vivo experiment was conducted to examine changes in fermentation end-products in the gastro-intestinal tract (GIT) of weaning piglets by the inclusion of fermentable carbohydrates in the diet. The experiment was repeated in three replicates of 36 piglets. Piglets were raised free of antibiotics and creep feeding prior to weaning at 4 weeks of age. Each replicate was conducted over a period of 10 days. The piglets were offered one of two dietary treatments: control diet (CON), and fermentable carbohydrate enriched diet (CHO); and were subjected to one of the two fasting treatments (i) fasting for 2 days in the beginning of the experimental period and (ii) non-fasting. Piglets were slaughtered on the 1st, 4th and 10th day of each period. Digesta samples were collected from: first half of small intestine, second half of small intestine, caecum, and colon. The dry matter, volatile fatty acid (VFA) profile, and ammonia concentrations were analysed. Food intake, growth and food conversion ratio were also recorded. There were no differences in production performances such as growth and food conversion ratio (FCR) between the treatment groups. Concentrations of VFA were significantly higher, while ammonia concentration was significantly lower in the CHO group compared to the CON group in different fermentation sites within the GIT (P<0·001), and on different slaughtering days (P<0·05). Fasting had no effect on fermentation end-products. This study concludes that the addition of fermentable carbohydrates of varying fermentabilities stimulated carbohydrate fermentation, with reduction in protein fermentation along the different parts of GIT studied, in weaning piglets.

Two experiments involving 213 finishing lambs were carried out to examine the responses in growth rate and carcass composition to the addition ofmetabolizable energy (ME) to a mixed diet in theform ofeither grass silage concentrate. In the second experiment the performance of lambs offered silage only was also compared at equal intake with the performance of lambs given mixed diets. On average the silages contained 224 g dry matter (DM) per kg; 148 g crude protein (CP) per kg DM; 86 g ammonia-nitrogen per kg total nitrogen and 723 g digestible organic matter per kg DM. Concentrates were based on barley and soya-bean meal and contained 181 g CP per DM. Responses in carcass weight gain when additional ME was added to mixed silagelconcentrate diets in theform ofgrass silage and concentrates were 9·2 and 10·2 (s.e. 0·90) gIM] respectively in experiment 1 and 9·8 and 10-(s.e. 0·33) g/MJ respectively in experiment 2, and responses in energy retention in experiment 2 were 0·34 and 0-(s.e. 0·012) MJ/M] respectively. However carcass gain and energy retention sustained by a silage only diet were only 0·67 and 0·70 respectively of those sustained by a high-concentrate diet at the same ME intake. The diet did not significantly affect body or carcass composition.

This investigation comprises three trials. Trial 1 consists of an in vitro comparison of three semen extenders: two egg yolk based (customized Tris-egg yolk-glycerol and Triladyl®), the third (AndroMed®) soybean lecithin based. With regard to post-thaw motility, the phytoextender AndroMed® proved to be superior (59±3% v. 53±2% and 53±2%, P<0.05). It had earlier been shown that addition of the commercial prostaglandin F2α preparation Dinolytic® before freezing compromises post-thaw motility; therefore, in Trial 2, Dinolytic® was added after thawing. Frozen-thawed spermatozoa tolerated addition of Dinolytic® at a concentration of 30% (v/v). In Trial 3, cows were inseminated using straws in which diluted semen and Dinolytic® were frozen in the same straw, separated by an air bubble, so intermingling could only take place in the course of insemination. Pregnancy rates at Dinolytic® dosages of 0%, 30% or 60% amounted to 44%, 41% and 56%, respectively (P>0.05), a result that encourages a large-scale field study, which is envisioned.

Thirty male piglets weaned at 20 days of age were fed on either a control diet with 20% crude protein containing 1·1 % lysine or one of two diets with 14·6 or 16·6% crude protein. Synthetic lysine was added to the latter two diets at the rate of 0·00, 0·18, 0·36 and 0·54% to provide four diets with 14·6% crude protein and 0·54, 0·72, 0·90 or 1·08% lysine and four diets with 16·6% crude protein and 0·72, 0·90, 1·08 or 1·26% lysine. All diets were offered ad libitum to piglets between 5·5 and 20·0 kg live weight.

Over the live-weight periods 5·5 to 20·0 and 12·0 to 20 kg, live-weight gains and food conversion improved with increasing total lysine to 1·08 % and 0·90 % respectively when pig performance was equal to that achieved on the control diet. The improvement in performance with an increasing level of total lysine during these two periods did not depend on the total protein content of the diet. During the live-weight period 5·5 to 12·0 kg, optimal performance was obtained when pigs were fed on the highest lysine level in the diets with 14·6 and 16·6% crude protein. However, only the diet of 16·6% crude protein promoted pig performance equal to that achieved on the control diet.

Carcass quality did not respond to lysine supplementation independently of protein level. With thedietof 14·6% crude protein, optimal carcass quality was obtained with 0·90 % lysine but was significantly poorer than that for the control. With the diet of 16·6% crude protein, carcass quality improved over the entire range of lysine supplementation and with 1·26% lysine was superior to that for the control.

Milk and butterfat production data from eight herds of dairy cows in Australia for the years 1963 and 1964 were analyzed for relationship with serum transferrin type. In the 932 lactations considered D2/D2 cows produced 521 ± 152 lb of milk more than A/A cows and lactated 15·3 ± 7·8 days longer after correction for season. There was no difference in fat percentage of the milk. The production of A/D2 cows was also significantly higher than A/A cows, but less than D2/D2 cows. Allowing for differences in lactation length still left a significant difference between D2/D2 and A/A cows in milk yield.

The best estimate of the effect of replacing a TfA by a TfD2 gene, allowing for season, was 170 lb more milk (P<0·01) and 6·5 days longer lactation (P<0·05), while TfD1 did not differ from TfA in either yield or lactation length.

A grower diet containing barley, wheat and soya-bean meal was expanded at 110°C and subsequently pelleted at 80°C. This processing was evaluated in laboratory tests as well as in digestibility experiments involving 12 barrows with an average initial live weight of 40 kg. The unprocessed control diet was offered as a meal. Each diet was offered ad libitum to six pigs during a 5-week period. The 1st week was an adaptation period and measurements were not carried out. Each pig was used in two 5-day digestibility trials which were performed in weeks 2 and 4. Neither food intake, weight gain nor food: gain ratio during the whole 4-week experimental period, nor apparent faecal digestibility and apparent retention of protein were significantly affected (P > 0·05) by expanding and pelleting the diet. Processing caused an increase in the in vitro protein solubility (P < 0·05) and reduced the dietary contents of free lysine and methionine (P < 0·05) while the contents of available lysine and free threonine and tryptophan were not significantly changed (P > 0·05). Apparent faecal digestibility of crude fibre increased substantially (P < 0·05) when the diet was processed, resulting in significantly lower production of faecal mass (P < 0·05) as well as lowerfaecal moisture content (P < 0·05). These phenomena were parallelled by a smaller water consumption (P < 0·05). Apparent digestibility and retention of phosphorus and calcium were diminished (P < 0·05) when the diet was expanded and pelleted.