Two experiments were carried out with growing-fattening bulls, offered a fattening diet based on concentrate and supplemented with soya oil or steam-flaked linseed. Soya oil (200 g/kg) was mixed with middlings (800 g/kg). Linseed (500 g/kg) and whole barley (500 g/kg) were steam flaked. The fat incorporation resulted in an increase of the ether extract content from 26·5 g/kg dry matter to about 45 g/kg. The incorporation of soya oil increased the average daily gain (P > 0·05). The saturated: unsaturated fatty acid ratio was reduced in perirenal fat due to an increase of oleic acid and a reduction of stearic acid. The inclusion of steam-treated linseed resulted in a lower slaughter weight (P < 0·05) and a shorter fattening period (P > 0·05). The fatty acid composition of perirenal fat was affected significantly: the concentrations of oleic, linoleic and linolenic acid were increased and the concentrations of myristic, palmitic and stearic acids were reduced. This resulted in a reduced saturated: unsaturated fatty acid ratio.

In a third experiment, samples of the two fat concentrates were incubated in nylon bags in the rumen. The ether extract disappearance was high with both concentrates. Furthermore, the fatty acid composition was altered to a large extent for soya oil while large proportions of unsaturated fatty acids were still present with steam-flaked linseed.

One hundred and thirty-six multiparous cows, 63 goats and 71 sheep were measured in breeding flocks and herds in Nigeria. The humped cattle breeds, and the large-bodied, humpless Kuri, are narrow-bodied and tall in relation to their length when compared with British breeds. Pelvic dimensions are small. The sheep and goats native to the coastal and middle belts (the West African Dwarf breeds) are miniature versions of those found in the north. Neither appears to be achondroplasic but dwarfing seems to have proceeded differently in the two species in that the adult West African Dwarf goat is similar in its relative body proportions to the adult northern goat, implying a proportional miniaturization. The West African Dwarf sheep appears to be a neotenous form with body proportions similar to those of an immature sheep.

Ninety-six Border Leicester × Scottish Blackface ewes, aged 2 to 6 years, grazed perennial ryegrass pastures during lactation. The state of their incisor teeth was assessed at parturition on a scale from score 1 (sound teeth) to score 4 (poor teeth). Their live weights and condition scores during lactation were then related to incisor score and age by regression analysis. Lamb growth was similarly analysed. Herbage intakes and milk production were measured in a subset of 24 ewes.

Ewe live weights were significantly lower, per unit incisor score, by 2·2, 2·5 and 2·1 kg at days 22, 50 and 96 of lactation respectively. In ewes with twin lambs, the equivalent reductions were 1·6, 2·8 and 2·1 kg respectively. Reductions in condition score, whilst still significant, were less marked. After adjusting for the effects of incisor dentition, there was no effect of age on ewe live weight or condition score.

Incisor dentition did not markedly affect herbage intake or milk production, except in measurements at day 53 of lactation, where higher incisor scores resulted in significant reductions in the production of milk and its components. Effects on lamb performance were confined to twins, where live-weight gain to day 50 was reduced by 12·2 g/day, per unit increase in ewe incisor score. This resulted in reductions of 0·7 kg (day 50) and 0·9 kg (weaning) in the live weight of twin lambs.

A 2 × 2 × 2 factorial experiment was conducted with 128 growing-finishing steer calves to examine the effects of feeding whole v. rolled barley in diets containing either a constant proportion of concentrate (0·67) or proportionately 0·33 concentrate for 56 days followed by 0·90 concentrate for 83 days, with the concentrate being given at either 08.00 or 15.30 h. Steers given hay at 08.00 h and concentrate at 15.50 h grew proportionately 0·05 faster (P < 0-05) and had better dry matter (DM): gain ratios (P < 0·05) during the first 56 days than those given concentrate at 08.00 h and hay at 09.00 h. By the end of the trial steers fed at 15.50 h had similar daily gains to steers fed at 08.00 h but required proportionately 0·02 less DM: gain (P <0·05). No significant difference in gain was detected between steers given whole (1·30 kg/day) or rolled (1·38 kg/day) barley, but those given whole barley ate proportionately 0-08 more DM daily and had a proportionately 0-15 poorer DM: gain ratio (P < 0-05). The digestibility of diets containing whole grain was reduced (P < 0-05). Thirty-six steers given whole barley bloated compared with nine given rolled barley (P < 0·05). No significant differences were found either in DM intake or in final proportion of concentrate in the diet between steers given the diet containing proportionately 0·67 concentrate throughout the feeding period and those given the variable concentrate diets. There was a trend for DM: gain ratios to be poorer for steers given the constant proportion of concentrate (6·89 v. 6·65).

Milk yields and blood metabolite and hormone profiles of a total of 40 Greyface ewes lambing in January or April and suckling single (S) or twin (T) lambs were determined. Ewes were given a fixed level of feeding throughout the first 10 weeks of lactation. Milk yields were measured weekly. Pooled blood samples (six samples; 20-min intervals), collected at weekly intervals for the first 10 weeks of lactation, were assayed for glucose, non-esterified fatty acids (NEVA), 3β-hydroxybutyrate, urea, albumin, total protein, insulin, growth hormone (GH), cortisol, prolactin, thyroxine (T4) and triiodothyronine (T3). At weeks 2, 4 and 10 of lactation samples were collected at 20-min intervals for 8 h and assayed individually for insulin, GH, cortisol and prolactin. Mean daily milk yield was lower in S than in T ewes in January (1·93 v. 2·33 kg/day; P < 0·05) and April-lambing ewes (1·95 v. 2·28 kg/day; P > 0·05). Profiles of NEFA and 3β-hydroxybutyrate indicated that T ewes were mobilizing adipose tissue at a greater rate than S ewes. The higher milk yield and rate of fat mobilization in T ewes compared with S ewes was associated with lower overall mean insulin concentrations (3·37 v. 5·04 mil per I; P < 0·002) and higher GH (6·29 v. 2·77 μg/l; P < 0·001) and cortisol (7·04 v. 3·64 μg/l; P < 0·001) concentrations in the weekly samples. Differences between rearing groups in mean concentrations of T4 and T3 were generally small and not significant. Mean prolactin concentrations were much lower in the January- than in the April-lambing ewes (73·7 v. 270·2 μ/l; P < 0·001) but this difference was not associated with a difference in milk yield. Substantial increases in insulin and GH concentrations generally followed feeding but the post-prandial profiles were dependent on stage of lactation; while GH concentrations increased following feeding at weeks 2 and 4 of lactation, there was generally a decline in post-prandial concentrations at week 10. It is concluded that the patterns of insulin and GH secretion during the hours following feeding may be an important determinant of the rate of tissue mobilization and milk yield in ewes subject to differences in demand for milk created by differences in litter sizes.

The effect of insulated (IN) and uninsulated (UN) buildings on food intake, performance and body temperature of sheep was studied over 4 years. The lowest average monthly temperature was -13·1°C. In the UN the temperature was on average 6-6°C higher than outside but the temperature in the IN remained fairly constant and was close to 10°C. Summarized for all 4 years the roughage intake was proportionately 0·02 higher in the UN than in IN (P > 0·05). There was no effect of treatment on weight gain, but the weight of the fleece was higher in IN than in UN (1·74 kg v. 1·66 kg per sheep). The mean age at first oestrus was 222 days. There was no difference in the length of pregnancy and lambing percentage was 185% in both treatments. The average birth weight was higher for lambs born in UN than IN (5·10 v. 4·95 kg), but the weight at weaning was the same. On only one occasion was the rectal temperature lower for ewes in UN than IN before shearing (38·7°C v. 39·2°C). After shearing no effect of treatment was found except for the 1st year, but in year 2 there was an interaction between plane of nutrition and housing. Results clearly indicated that uninsulated buildings are well suited for sheep.

Thirty-four mature ewes (17 rearing twins and 17 rearing singles) were used to examine the effect of litter size on herbage intake at pasture by ewes over the course of lactation; intake by their lambs during weeks 13 to 15 of lactation was also evaluated. Daily organic matter intake (OMI) was estimated using the n-alkane technique. Ewes and lambs rotationally grazed 19 × 0·15-ha paddocks during the experimental period which extended from week 2 of lactation to weaning at week 15 of lactation. Sward conditions were maintained steady throughout with daily OM allowance per ewe varying between 4·6 and 5·7 kg and dry matter digestibility between 763 and 858 g/kg DM.

Throughout lactation OMI and OMI per kg body weight were higher for twin-rearing ewes (P < 0·05) than for ewes rearing singles: 2·50 and 2·26 kg/day, and 38 and 32 g/kg per day, respectively. Intake reached a maximum on weeks 6 to 7 of lactation. From weeks 13 to 15 of lactation, OMI and OMI per kg body weight for single- and twin-reared lambs were 1·09 and 1·14 kg/day, and 31 and 36 g/kg per day, respectively.

The combined food intake per dam-offspring unit for weeks 13 to 14 of lactation for a ewe plus her single lamb was 2·8 kg OM per day compared with 4·3 kg OM per day for a ewe plus her two lambs. The repeatability of average weekly intake by ewes was 0·39 over the course of lactation and 0·40 for lambs over the 13 to 15 week period. Repeatability estimates for ewes increased slightly when data from weeks 3 to 7 and weeks 13 to 14 was analysed separately (0·42 and 0·53, respectively).

Muscle to bone weight relationships within anatomical regions (proximal-distal division into pelvic, thigh and lower leg groups) and subregions (division within regions into gluteal, intrinsic pelvic, cranial, caudal and medial thigh, and cranial and caudal lower leg groups) of the hind limb and also of its most important muscles (no. = 11) were compared between goats and sheep using the method of multivariate analysis of the centred data. In this comparison, a total of 39 animals was considered: 13 male kids of the Alpine breed (K) and a sample of 26 male lambs derived from different breeds or crossbreeds representing, in equal numbers, lambs having good conformation (LGC) and poor conformation (LPC). Lambs were chosen on the basis of the hindlimb length the means of which were 22·9 (s.e. 1·5), 29·3 (s.e. 1·8) and 29·1 (s.e. 2·5) cm for LGC, LPC, and K, respectively. Corresponding cold carcass weights were 19·71 (s.e. 347), 17·28 (s.e. 1·77) and 10·84 (s.e. 0·56) kg.

In both comparisons (K-LGC and K-LPC) the two species were systematically distinguished by the size of the following ratios: (pelvic muscles/os coxae + leg muscles /tibia) relative to thigh muscles/femur (for regions), which was lower in lambs than in kids; intrinsic pelvic muscles/os coxae relative to caudal thigh muscles/femur (for subregions), which was higher in kids than in lambs. For individual muscles, they were distinguished by the size of the following ratios: rectus (emoris/femur relative to semimembranosus/femur (or gluteus medius/os coxae) in the comparison K-LGC, which was higher in lambs than in kids, and vastus lateralis/femur relative to sum of pectineus + gracilis/femur (or gastrocemius/tibia) in the comparison K-LPC, which was lower in kids than in lambs. The results show that the muscle-bone ratios of the anatomical regions, subregions and the most commercially important muscles in the hindlimb can be used as discriminant characteristics of species.

The production responses of crossbred lambs [Poll Dorset (♂ × (Border Leicester ♂ × Merino ♀)] immunized against somatostatin (sornatotropin release inhibiting factor; SRIF) and whose mothers were also given anti-somatostatin vaccination was investigated in this study. There were no significant differences between immunized and control lambs in term of live-weight gain, food intake, food conversion efficiency, digestibility, eating pattern, wool growth and carcass composition. The concentration of growth hormone in plasma of immune lambs was not significantly elevated, even though the lambs had a generally increasing anti-SRIF antibody titre during the experiment. The findings suggest that although the lambs were successfully immunized against SRIF, homeorhetic mechanisms maintained growth hormone and productivity traits within normal levels.

Genetic and non-genetic factors affecting survival during the post-weaning period from 3 to 12 months of age were assessed in 823 kids (217 Black Bengal, 410 Jamunapari × Black Bengal and 196 Beetal × Black Bengal) born during 1981-86. The overall survival rates during 3 to 6 and 6 to 12 months of age were 79·22 (s.e. 4·06) and 82·02 (s.e. 5·49)% respectively. Variation in survival rate during 3 to 6 months of age was significant due to season of their birth (P < 0·01) and birth weight (P < 0·05). Survival rate during 6 to 12 months of age varied due to genetic group (P < 0·01), sex (P < 0·05) and birth weight (P < 0·05). Type of birth (litter size), dam's weight at kidding and filial generation had no significant effect on survival rate during the post-weaning period. Birth weight of kids had a positive linear relationship with their survivability during post-weaning period. Summer-born kids had significantly lower survival rates from 3 to 6 months of age compared with those born in the winter and monsoon periods. Heritability estimates for survival rates during the post-weaning period were not significantly different from zero.

The field application of a laparoscopic technique to permit intra-uterine insemination of ewes with frozen-thawed semen was examined in two trials, conducted over successive years, to (i) determine the optimum time of insemination relative to sponge removal/pregnant mares's serum gonadotropin (PMSG) injection and (ii) establish the relationship between semen dose and conception rate. Pooled semen was used in both trials, and each involved > 900 ewes in a number of commercial flocks.

Maximum conception rates were achieved when insemination was conducted between 54 h and 60 h after sponge removal/ PMSG injection. However, there was no significant difference in conception rate when motile sperm numbers were reduced from 52·2 × 106to 13·0 × 106 motile sperm per uterine horn.

The overall conception rates (pooled over flocks and treatment groups) were 56% and 58% for the two trials, with a wide degree of variation between flocks in both cases (45% to 79% for trial 1 and 45% to 69% for trial 2). However, there was evidence for consistent differences in conception rates between the six flocks involved in both years of the trials.

Sixty-four mature ewes (equal numbers of Bluefaced Leicester ♂ × Swaledale ♀ and Suffolk ♂ × (Bluefaced Leicester ♂ × Swaledale ♀) which had lambed in March were separated from their lambs on 1 fune. They were randomly allocated from breed and live-weight blocks to one of four treatments arranged in a 2 × 2 factorial design. All received vaginal implants, with or without melatonin, on 1 June. The implants were removed, all ewes given 20 mg progesterone in oil intramuscularly and equal numbers isolated or introduced to rams on 12 July. Ovarian activity was monitored by progesterone concentrations in blood taken three times weekly from the jugular vein. Four ewes receiving melatonin and four control ewes were bled for 24 h on 6 July to determine plasma melatonin concentrations.

Melatonin treatment increased plasma melatonin concentrations during the day. All ewes were anovular prior to 12 July. There were no differences between the two ewe types in their response to treatment. The number of ewes ovulating before 27 August was: control 1; melatonin 6; ram 16; melatonin + ram 16. The mean date of emulation for both the ram and melatonin + ram groups was 21 July. The number of ewes showing oestrous behaviour was 16 and 15 for the ram and melatonin + ram treatments respectively. The proportion of ewes responding to ram introduction was judged as unusually high, possibly as a result of the favourable male:female ratio. Pregnancy rate was in excess of 80% for both treatments, with resulting litter sizes of 14 for the ram and 1·8 for the melatonin + ram treatments respectively (P > 0·05).

Commercial carcass grading measurements and sample joint dissection were evaluated as predictors of carcass lean concentration using a data set of 1320 pig carcasses from four breeding companies. Entire males, castrated males and gilts from White-type and Meat-type populations were reared on ad libitum or restricted feeding regimens and slaughtered to achieve a carcass weight of either 52·5 kg or 72·5 kg. A model was fitted which examined the accuracy and stability of regression equations for different populations, sexes and feeding regimens, and different values of P2 and carcass weight. The regression slope of lean concentration on P2 differed by sex and population. Lean concentration decreased faster with increases in P2 among gilts than among entire or castrated males. At the same level of P2 and carcass weight, pigs fed ad libitum contained 5 g/kg less lean in the carcass than pigs fed at a restricted level. Biases among populations, sexes and feeding regimens were also found when carcass lean concentration was predicted from additional measurements: muscle depth at P2, fat thickness and muscle depth at 3/4 last ribs, and eye-muscle area. The regression slope of lean concentration on sample joints showed little evidence of variation among populations (except for the hand joint), sexes or feeding regimens. There were important differences in the intercept for different populations. The ham was the most accurate (residual s.d. = 11 g/kg) and least biased joint.

By a combination of complete and incomplete dissections a considerable increase of precision or reduction of expense may be obtained in the construction of a prediction formula for the proportion of lean meat of a carcass from objective carcass measurements. This approach, referred to as double-regression, is demonstrated on data involving dissection of pig carcasses in The Netherlands. Advantages of double-regression relative to ordinary regression with respect to precision and experimental cost are discussed. Expressions for optimal sample sizes at fixed total cost are derived.

Pre-pubertal ewe lambs were introduced to rams on 17 August (Tl), 12 September (T2) or 10 October (T3) or isolated from rams until 21 December (Tc) (no. = 13). Blood was taken for progesterone assay three times weekly (no. = 13) from 16 July. Blood was taken for LH assay at 15-min intervals for 8 h (no. = 8) at the time of the introduction of rams and subsequently at the time of further ram introductions. Blood was taken from Tc lambs at each ram introduction. Tl, T2 and T3 lambs ovulated for the first time 16 (s.e. 2·2) days earlier than Tc lambs but only T3 lambs ovulated after and apparently in response to the introduction of the rams. The mean baseline LH levels were higher in Tl, T2 and T3 lambs in comparison with Tc lambs at all sampling periods. The mean pulse frequency of LH secretion was significantly increased by the introduction of rams in T2 and T3 lambs in comparison with Tc lambs. The mean pulse frequency of LH secretion was greater in Tl, T2 and T3 lambs at the October sampling period in comparison to Tc lambs.

A total of 96 Large White weaner pigs, comprising equal numbers of entire males and females, and of controls and eighth generation index-selected genotypes, were fed ad libitum until 40 kg live weight. From 40 kg until slaughter at 85 kg live weight pigs within genotype and sex groups were fed either ad libitum or 2·2 times maintenance. The left sides of the carcasses were divided into shoulder, middle and ham portions and the middles further divided into eye, wedge and belly dorso-ventral portions. Tissue dissection was performed on all portions separately.

Selected pigs yielded proportionately 0·15 less fat, 0·08 more muscle, a smaller muscle: bone ratio and 4·05 mm less P2 backfat depth than the controls. When the data were adjusted to the same mean P2 fat depth, the carcasses of selected pigs had 0·07 less fat and 0·03 more muscle. There were no appreciable differences between the genotypes in cranio-caudal tissue distribution. However, there were differences in dorso-ventral tissue distribution since the middles of selected pigs had proportionately and absolutely more of each tissue in the belly. There was no evidence that selection against fat at the P2 site had caused any increase in fat lateral to the m. longissimus.

Food restriction increased carcass muscle by 0·10 and decreased fat by 0·17, but had no effect on muscle: bone ratio or cranio-caudal or dorso-ventral tissue distribution. At the same carcass side weight and P2 fat depth, restricted feeding decreased fat by 0·10 and increased muscle by 0·06 in the carcass side.

It is concluded that carcasses of the selected pigs would be undervalued relative to the controls due to less fat and more muscle at the same weight and P2 fat depth. Also, restriction on food intake can cause carcasses to be undervalued relative to feeding ad libitum.

A batch offish meal was (a) untreated, (b) heated to 130°C and (c) heated to 160°C under controlled conditions.

In trial 1, these materials were incorporated into a diet based on barley meal (278·7 g/kg), wheat starch (412·5 g/kg), maize meal (245·3 g/kg) and tallow (33·5 g/kg) at a rate of inclusion of 100 g/kg. Diets contained a vitamin/mineral pre-mix together with the inert marker titanium dioxide and were given to four pigs fitted with simple T-piece Heal cannulas over four time periods each of which lasted for 6 days and which allowed the determination of faecal and Heal apparent digestibilities of nitrogen and amino acids. The results indicated that over-heating fish meal results in a reduction in both Heal and faecal apparent digestibility although, as there was no effect of treatment on the quantity of nitrogen absorbed from the large intestine, the two measurements were directly related. Heal and faecal apparent digestibilities for individual amino acids were not the same as data for nitrogen and, accordingly, the latter cannot be used to predict the two former.

In trial 2, the three fish meal samples were included in diets formulated on the basis of total, faecal and Heal apparent digestible amino acids. The nine diets were given to pigs over the live-weight range 27·5 to 52·5 kg. Giving diets formulated on the basis of both faecal and Heal apparent digestible amino acids resulted in improved performance compared with giving diets based on total amino acids when the diets containing fish meal heated to 160°C, but performance achieved with diets containing untreated fish meal was still higher.

Heal apparent digestible amino acids from heat-treated fish meal are not completely available to the pig, and it is suggested that care needs to be taken in equating digestibility with subsequent availability. There appears to be no advantage of using Heal rather than faecal, apparent digestible amino acid values in texms of accuracy of diet formulation.

Six boars weighing about 65 kg were penned individually in preliminary observations to investigate their response to increasing levels of faeces in a concentrate diet fed as a gruel. During an introductory 5-day period pigs were restricted to 1·5 kg concentrates plus 100 g fresh faeces daily. The daily concentrate allowance was then increased to 2·2 kg and faeces increased by 50 g/day providing the ration was consumed completely. Two animals showed diarrhoea at intakes of 1 kg faeces per day while the remaining four animals showed no signs of ill health at the maximum allowance of 1·4 kg faeces per day.

In the main experiment littermate pairs of the same sex (16 boars plus 16 gilts in total) were allocated to control (concentrates only) or treated (concentrates plus fresh faeces) groups. Animals were housed in metabolism crates from about 55 kg live weight and the diet allowances were increased gradually up to 2·5 kg concentrates with or without 500 g fresh faeces per day. This was achieved on day 17 and continued to slaughter some 40 days later when pigs weighed around 85 kg live weight. Levels of skatole and indole were significantly higher in the caecal contents of treated pigs at slaughter but similar in faeces compared with controls. There was no effect of dietary treatment on skatole or indole levels in subcutaneous fat.

It seems unlikely that natural coprophagy would contribute significantly to skatole and indole levels in carcass tissues.

Effects of creep food presentation on feeding behaviour and intake were studied with eight litters of eight to 10 Yorkshire × Landrace piglets in the 3rd and 4th weeks after birth, before weaning at 4 weeks of age. In each week, four treatments were applied, each for 24 h: a single two-space feeder unchanged from the previous day; a clean feeder with fresh food supplied at 09.00 h; a clean feeder with fresh food supplied at three times during the day; and three feeders (six feeding spaces) providing increased access to food throughout the day. There were no significant differences between the first three treatments in time spent at the feeder (recorded by video over 24 h) or food intake of piglets. However, the fourth treatment increased average intake in week 3 to 2·1 times the average of the other treatments, and in week four to 1·4 times. In week 3, most piglets spent more time at the feeder when access was increased, while in week 4 the effect was restricted to piglets which ate very little. This suggested that imitative learning was important in the initiation of feeding. Analysis of both litter means and within-Utter variation showed that piglets which ate more solid food before weaning gained more weight in the 2 weeks after weaning. However, this correlation was confounded by correlations of both measures with birth weight and other variables. Causal links between creep feeding and post-weaning weight gain remain to be demonstrated.

Voluntary food intake, milk production and blood characteristics were measured in mares between the 3rd month before foaling and the first 5 weeks of lactation. The effect of breed during pregnancy was determined using 15 light mares and eight heavy mares (522 and 763 kg live weight (LW) after foaling respectively). The effect of parity was studied on light mares (seven were primiparous and eight were multiparous). In lactation, only four primiparous and four multiparous light mares were retained. Diet consisted of 900 g hay and 100 g concentrates per kg and was offered ad libitum. Voluntary food intake in pregnancy was higher for heavy mares than for light mares: 15·2 v. 10·3 kg dry matter (DM) daily. This difference was explained by differences in LW, since DM intake was the same when expressed as a fraction of LW or metabolic weight (M). Energy and nitrogen supply exceeded requirements, in the same way for light and heavy mares. No significant variations in blood measurements were observed between light and heavy mares, except for glucose. Primiparous mares ate less DM than multiparous mares in pregnancy: 9·7 v. 10·8 kg DM (P > 0·05), significantly so relative to LW and M. DM intake per kg LW or M depended on the parity. This difference had no effect on blood measurements, except for acetate. During lactation, no other differences in voluntary food intake were observed with regard to parity, whatever the week of lactation. Milk yield was higher for multiparous mares than for primiparous mares (16·6 v. 14·6 kg daily). Gross energy of milk varied according to a similar pattern, principally because of variations in fat concentration (20·2 v. 16·5 g/kg for multiparous and primiparous mares respectively). Energy balance was significantly more positive for multiparous than for primiparous mares.