The additive genetic response per generation and the genetic superiority of female genotype(s) selected for commercial cloning (clonal response) were maximized for a closed adult nucleus scheme, with 256 or 1024 test places, by varying the mating design (number of clones, full-sibs and half-sibs). Responses were corrected for effects of finite sample size and correlated index values on the selection intensity, and variance reduction due to selection. Additive genetic responses, which varied from 0·153 to 0·514 phenotypic standard deviations per generation, were 0·68 to 0·89 of corresponding uncorrected predictions. Reductions were largest when the intensity and accuracy of male selection were high. Clonal responses varied from 0·460 to 2·506 phenotypic standard deviations, increasing with the intra-clone correlation, the intensity of clonal selection and the test capacity. Reductions in clonal responses, which varied from proportionally 0·04 to 0·27, were smallest when dominance variance was high. Increasing the test capacity resulted in a proportionally 0·21 to 1·55 increase in genetic responses, while proportional increases in clonal responses varied from 0·09 to 0·36. With selection of only one male per full-sib family, designs which maximized genetic and clonal responses were different in all cases. Differences were largest when the heritability and the intra-clone correlation were low and the intensity of clonal selection was high. Without the restriction on male selection, optimal mating designs were different, unless dominance variance and intensity of clonal selection were both low.

The effects of milking on the overall productivity of N'Dama cattle kept under village conditions were studied using three groups of cows during a 27-month period. One group of 46 cows in 16 herds in Nioro Jattaba village was not milked for human consumption and their calves had access to all of their milk (group 1). Another group of 46 cows in the same herds was partially milked for human use once a day while the calves had access to the residual milk (group 2), the normal husbandry practice in this village. A third group of 70 cows in six herds, managed similarly in a similar production environment in the nearby village of Keneba, was milked twice daily with the residual milk for their calves, the normal husbandry in this village. A mean extraction of 296 (s.d. 110·7) kg milk per cow occurred in group 2 during a lactation period of 517 days while the figure for group 3 was 450 (s.d. 177·7) kg per cow over 430 days. At the end of the observation period, calf mortality to 12 months averaged 6% and was similar in all groups. Calf weights at 12 months in group 1 (98·1 kg) exceeded that of groups 2 and 3 by proportionately 0·26 and 0·38 (P < 0·001) respectively. Mean calving rate was 53% in groups 1 and 2, and 72% in group 3. Post-partum body-weight losses were most severe in group 1, followed in order by groups 2 and 3. A herd productivity index (incorporating calf weight, live weight equivalent of milk extracted for human use, cow and calf viability and calving rate) was 100·7 kg calf weight per 100 kg metabolic weight of cow per year for group 1, 110·2 for group 2 and 166·1 kg for group 3. These values suggest that recommendations to small-holder farmers for enhancing livestock productivity should include strategies to improve milk yields in general rather than advocating no milk extraction or changing the milking regime currently practised.

The consumption of grass silage by each individual cow in a group housed during two consecutive winter-feeding periods was continuously recorded. During the first winter, one of two concentrates, containing high starch or high fibre, were offered on a sliding scale and half the cows were injected with bovine somatotropin (bST). During the second winter, one of two concentrates, containing high or low rumen-undegradable protein were offered at a flat rate ivith two-thirds of the cows receiving bST. The cows injected with bST had significantly greater yields of milk but their consumption of silage was similar to that of cows not treated with bST. The type of concentrate offered had no significant effect on silage consumption. Although there were significant variations in the consumption of silage from day to day, there were highly significant variations in consumption attributable to individual cows. This individuality of intake persisted in a consistent manner throughout a feeding period and could not be explained on the basis of milk production, body weight, age or parity. In 24 of the cows which were used in both years, their individual intakes for the two periods were significantly correlated. The possibility that this individuality may be of economic importance is discussed.

Body composition was studied in 20 mature, non-pregnant, non-lactating cows from five breeds (Hereford, Aberdeen Angus, Dexter, British Friesian and Jersey) kept on four feeding levels until they attained equilibrium body weights that were proportionately 0·7,0·9,1·1 or 1·3 of their normal adult body weight.

Significant breed differences were found in the proportions of body tissues and organs and these were associated with breed differences in lactability (i.e. genetic milking potential adjusted for body size). As a proportion of body weight, intra-abdominal fat, liver, spleen and uterus increased significantly with lactability and hide decreased significantly. Empty gut and gut fill also increased with lactability but not significantly. Liver proportion in dairy breeds was 1·26 times the proportion in beef breeds. Corresponding values for intra-abdominal fat and hide were 1·43 and 0·83.

The most dramatic increases with feeding level were in the proportions of subcutaneous fat, both intra-abdominal fat depots, and the udder. All fat depots were completely depleted when body weight decreased to about 0·6 of its normal adult value. Strong decreases occurred in the proportion of muscle, carcass bone and offal. The proportion of empty gut decreased significantly with increased feeding level. Liver, tail, thymus and possibly gut fill were the only traits entirely unaffected by feeding level.

The near-constancy of liver proportion at equilibrium implies that the rapid response of the liver to a change in feeding level is eventually matched in magnitude by the slower responses in other tissues and organs, so that the original proportionality of about 1 kg body tissue for each 10 g liver is eventually restored.

Twenty Friesian (group 1) and 20 buffalo (group 2) calves and 14 of each of lactating Friesians (group 3) and lactating buffaloes (group 4) were maintained in middle of winter conditions of Egypt for 2 months. The calves (groups 1 and 2) were of similar age (6 to 7 months) and average body weight (120 kg). The lactating animals were in the fifth season of lactation, non-pregnant, in mid lactation and yielded 12 to 14 kg milk on average daily. Similar groups of animals of the same types (groups 5, 6, 7 and 8, respectively), numbers, live body weights and physiological status were maintained under hot summer conditions for 2 months. The effect of hyperthermia during summer season on Friesians and buffaloes compared with winter was also studied.

The results showed that buffaloes were more tolerant than Friesians to the environmental conditions of Egypt. In winter, buffalo calves had poorer (P < 0·05) food efficiencies (kg gain per MJ net energy), higher dry matter intakes (DMI, P < 0·05) and total lipids in the plasma (P < 0·01) than Friesians, while the contrary occurred in total proteins, albumin, phospholipids and cholesterol (P < 0·05). In summer, growth rate and the concentrations of total lipids, phospholipids and cholesterol in the plasma were higher (P < 0·01), and total proteins and albumin were lower (P< 0·01) in buffalo than in Friesian calves. In summer, in Friesians, both DMI and growth rate decreased (P < 0·05) and food efficiency as kg weight gain per MJ net energy was poorer (P < 0·05). In the plasma total proteins and albumin increased (P < 0·01) but haematocrit %, phospholipids and cholesterol decreased (P < 0·05). In buffalo calves, only total proteins and albumin increased (P < 0·01) due to heat stress.

In lactating buffaloes, food efficiency was poorer (P < 0·01) and DMI and plasma haematocrit % were significantly higher, while the concentrations of total proteins, globulin, phospholipids and cholesterol in the plasma, and milk yield were significantly lower than in lactating Friesians in the winter season. Lactating buffaloes were poorer (P < 0·01) in food efficiency and had lower concentrations of total proteins, globulin and cholesterol than lactating Friesians in the summer (P < 0·01).

The objective of the experiment was to determine the effects of different, sustained levels of undernutrition on the reproductive performance of Brahman heifers, and on their subsequent growth to adulthood, when reared exclusively on a low-quality tropical pasture.

Irrespective of the live-weight gains realized between weaning and the target weight of 270 kg, heifers on all treatments conceived at a similar mean weight of 290 kg. Nevertheless, heifers on the low weight-gain treatment had a significantly different relationship of cumulative conceptions to weight, which was confirmed when Cox's proportional hazard model was fitted to the data, using a dummy variable to represent treatment effect.

A Gompertz growth model was fitted to the live weight of each individual animal. A significantly larger mean asymptotic weight was observed for the low weight-gain treatment, which was unrelated to the number of calvings or weanings, or to the total weight of calves weaned per animal. Asymptotic weights were positively correlated with first conception weight and age, both within and across treatments.

The implications of drastic post-weaning undernutrition and continued suboptimal feeding are discussed briefly.

The effects of recombinantly derived growth hormone (GH), oestradiol-17β plus trenbolone acetate, clofibrate, melatonin and fasting on basal plasma triglycerides (TG) and TG entry rate were determined in wether lambs given lucerene/barley pellets ad libitum. Clofibrate was administered at 2 × 0·5 g capsules orally, GH (0·25 mg/kg live weight) was injected subcutaneously daily whilst oestradiol-17β, oestradiol-17β plus trenbolone acetate and melatonin were slow release implants (either 4 or 4·8 mg, 4 nig and 20 nig and 18 mg respectively) placed subcutaneously in the ear. Both fasting and oestradiol treatments raised basal TG levels without influencing TG entry rates, defined as the maximum rate of change of plasma TG 3 to 6h following a dose of Triton WR1339 of at least 0·2 g/kg live weight. Entry rates were similar to those previously reported for goats but were higher than those reported for sheep. Triton WR1339 used to determine entry rates was found to reduce food intake at all levels in some sheep despite reports to the contrary. Among the various treatments, only oestradiol-17β and trenbolone acetate influenced body composition as determined by chemical analysis of minced carcasses, resulting in an increased gain of carcass protein and decreased gain of carcass fat. Clofibrate, melatonin and Triton, if allowance is made for Triton-induced loss in food intake, had no clear effects on body fatness. Overall the effects of hormones on plasma TG appeared to be small and it seems improbable that plasma TG are involved in effects of hormones on fatness.

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.

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.

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 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.

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.

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.

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.

Worm meal obtained from worms (Eisenia fetida) raised on waste materials was evaluated for Rainbow trout as a replacement for fish meal at dietary concentrations of 250, 500 and 1 000 g replaced per kg. During the study period none of the diets was detrimental to fish health. The dietary concentrations of 250 and 500 g/kg replacement gave higher growth rates than that of the control group (0 g/kg replacement), the former having consumed less food. The biological parameters of food conversion efficiency and protein efficiency ratio, for these replacement levels, also showed values better than the control diet. Liver somatic index and the chemical composition of fish fillets showed no significant differences between diets, except for a significant decrease in lipid content with increasing worm meal inclusion.

Changes in plasma cholecystokinin (CCK) levels after feeding were investigated in dairy cows. Three HolsteinFriesian lactating cows given concentrates at 06.00 and 13.00 h and hay at 16.30 h were used. Blood samples were taken from the jugular vein from 0 (before feeding, 13.00 h) to 6 h at 1-h intervals. The immunoreactivity of CCK was expressed in terms of the CCK-8 equivalent. The plasma concentration of CCK was not changed over the experimental period. This result might be reflected by the continuous flow of digesta from the rumen.