Forty Hampshire Down × Mule (Blue-faced Leicester cf × Swaledale 2) ewe lambs, obtained within a week of birth, were reared on milk replacer and from 6 weeks of age on a complete pelleted diet. Food intake of individual lambs was controlled to produce periods of high (H: ca. 210 g/day) and low (L: ca. 110 g/day) rates of live-weight gain from 4 to 20 and 20 to 36 weeks of age. Groups of eight lambs were slaughtered and dissected at 20 weeks having followed either growth paths H or L, and at 36 weeks having followed growth paths LL, HL or LH.

Growth path had little effect on the lean or bone content of the carcass, but had a significant effect on carcass fat content and distribution. At the same carcass weight, the ratio of intermuscular to subcutaneous fat was higher in leaner carcasses. When compared at the same weight (ca. 35 kg) but different ages (H, 20 weeks; LL 36 weeks), the slower growing LL lambs contained 1·22 kg more fat than the H lambs, primarily in the intermuscular and subcutaneous depots but also in the internal omental depot. At the same age and weight (ca. 36 weeks and 48 kg), lambs which had followed the growth path LH contained 2·5 kg more fat than lambs which had followed the HL path. These differences in fatness are thought to have come about through changes in the effective protein:energy ratio of the diet, induced by the manipulation of food intake.

Carcasses of HL lambs would be of more value to the meat trade compared with LH, since they would require less fat trimming before retail sale.

The paper describes the results of the analysis of over 3000 records of Cambridge sheep kept on 11 farms over a 12-year period. The heritability of the number of lambs born per ewe increased from a low value for the 1-year-old ewes to a high value for the 3-year-old ewes; the multiple age value for 2-, 3- and 4-year-old ewes was 0·33 (s.e. 0-121). Heritability estimates for number of lambs surviving were lower, but showed the same trend of increasing values with increasing ewe age. This trend in heritability was also evident for the mean 50-day lamb weight, as a trait of the ewe, which had a multiple age value of 0·20 (s.e. 0·151). The estimates of heritability of various measures of early lamb mortality were relatively low. Date of first oestrus showed a variable heritability although the multiple age value was 0·42 (s.e. 0·149).

Prolificacy was strongly correlated with various measures of early lamb mortality although the correlation with the final number of lambs weaned was positive. Prolificacy was positively correlated with the ewe's mature weight and the ewe's date of first oestrus and the genetic correlation with mean 50-day lamb weight was slightly positive.

The effect of increases in prolificacy on numbers of lambs weaned was markedly curvilinear with maximum numbers of lambs weaned at an intermediate level of prolificacy.

The effect of cereal straw supplement on turnip diets has been studied in Romanov × Rasa Aragonesa ewes in early lactation. Measurements were made of level of intake, blood characteristics and performance under pen-fed and grazing conditions. Barley straw supplementation resulted in a proportional increase of 0·1 in turnip intake to give daily intakes of 82 and 94 g organic matter per kg M0·75 for pen-fed and grazing ewes respectively.

Ewes fed on turnips showed a significant decrease in red blood cell numbers, haemoglobin and packed cell volumes though remaining within the range considered as normal for this species. Heinz bodies were present in proportionately up to 0·25 of erythrocytes and no clinical symptoms were observed.

The average weight gain of lambs reared by the grazing ewes was 173 g/day. However, growth rates of lambs and weight losses of ewes on turnip diets were lower than expected from the performance of animals on a control diet based on barley, lucerne and straw.

The response of 35-kg store lambs to diets containing increasing rumen-undegradable nitrogen (UDN) concentrations was measured by live-weight gain and nitrogen (N) balance. A range of UDN concentrations from 2·4 to 7·2 g/kg dietary dry matter was achieved by supplementing a basal diet of NaOH-treated barley straw, tapioca, extracted rapeseed meal and minerals with both formaldehyde-treated rapeseed meal and fish meal. Sufficient diet to provide maintenance and a growth rate of 150 g/day was given to the lambs, according to live weight. Increasing levels of UDN promoted a linear increase in live-weight gain and N retention. However, the response to fish meal was greater than that for formaldehyde-treated rapeseed meal. The true digestibility of N of formaldehyde-treated rapeseed meal determined in chickens by ileal analysis was low in comparison to that of untreated rapeseed meal.

Embryo transfer following multiple ovulation could allow faster rates of genetic change in sheep, by increasing the effective female reproductive rate. The gains would come from lower generation intervals or increased selection among females, or both. They require good embryo transfer rates at 6 to 8 months of age. These are not adequate at present and need to be improved by research and development, justified by the extra genetic gains shown here to be possible. If high rates of embryo transfer (10 progeny per donor) could be achieved, then, with appropriate selection schemes, the rates of genetic change could be doubled compared with efficient schemes using normal reproduction. This applies to most traits, to those measured before reproductive age (growth traits and carcass traits estimated in the live animal), to female reproductive traits and to wool traits measured at 14 to 16 months of age. With moderate rates of embryo transfer (5 progeny per donor), gains of 50 to 70% in genetic response could be obtained. To limit the rate of inbreeding to moderate levels in a closed selection flock, some 100 to 200 females (1000 progeny) would be required. Application of the methods may be difficult with current breeding structures, and the development of special nucleus selection stocks i s proposed.

Twenty-four indigenous goats suckling either single (male or female) or twin kids were traditionally reared during a 32-week lactation period. During the suckling period of 12 weeks, milk production was estimated at 7-day intervals. During the milking period the goats were hand-milked twice daily and their milk production was measured at 4-week intervals. Milk samples were analysed for fat, protein, lactose, ash and dry matter concentration and solids-not-fat and energy concentration were calculated. During lactation, the goats were weighed at regular intervals and their body-condition score assessed at each weighing.

Goats with twins produced more milk than did those with singles during the suckling period but not after weaning. Peak yield occurred between the 10th and 11th week of lactation. Yield declined rapidly after weaning at 12 weeks and then decreased gradually from 16 to 32 weeks. The sex of the single kids had no effect on lactation yield. Milk composition was not affected by the number or sex of the kids suckled. Fat, protein and ash concentration fell during the 1st month of lactation and thereafter showed a gradual rise. Lactose concentration fell gradually after the 2nd month. Both live weight and body condition of the goats increased continuously throughout lactation.

Fourteen red deer, three hinds and 11 stags, ranging from birth (8·8 kg) to 10 years of age (143·4 kg), were slaughtered and the carcasses dissected into individual muscles and bones.

Regression equations relating the actual weight of each component or group of components to independent variables such as age, live weight, carcass weight, total muscle weight or total bone weight were fitted to the data, the majority of which satisfactorily conformed to simple allometric relationships. Twenty of the muscles and one muscle group exhibited a pattern of growth which was better described by the inclusion of a quadratic function. The description of the data using an additional term in the allometric equation was considered to be more biologically sound than the often-used practice of fitting different coefficients to the logarithmic form of the allometric equation for each stage of growth. The group of muscles surrounding the thoracic and lumbar vertebrae and those of the abdominal wall were the fastest growing, both having a growth coefficient of 1·08 with standard errors (s.e.) of 0·013 and 0·017 respectively. The slowest growth was found in the distal forelimb group of muscles (growth coefficient = 0·84, s.e. 0015), no individual muscle in this group having a growth coefficient greater than 0·9.

The bones of the axial' skeleton increased in weight faster than those of the appendicular skeleton. The growth coefficients were, axial 1·13, forelimb 0·93 and hindlimb 0·92 (s.e. 0·025, 0013 and 0·015, respectively).

The muscles of the proximal hindlimb were slightly heavier in the hind, and those of the dorsal neck and shoulder heavier in the stag.

Only one minor anatomical variation was found which was related to the insertion of the m. rhomb oideus.

Data are provided from four Kenya ranches relating to seasonality of breeding, age at first parturition, parturition interval, sex ratio, gestation period and the early survival of young in one-humped camels. A total of 799 births was recorded. Births occurred throughout the year with no marked peak, there being no significant correlation of conception with rainfall. Age at first parturition (no. = 37) was 54·3 months. Parturition interval (no. = 460) was 20·2 months and was significantly affected by the random effects of the dam as well as by the fixed effects of the herd and the survival of the previous young. The sex ratio at birth was 1·06 males to 1·00 female. Gestation period was 377·1 days, and was not significantly affected by any of herd, month of conception, sex of young or age of animal. Abortions amounted to 11·6% of all births with the total of pre-weaning losses (including abortions) being 25·7%. Improving familiarity of the owners with the animals and better management could lead to considerable increases in performance.

Three experiments measured intake and assessed quality of roughage refused by individually-fed castrated Saanen goats and Suffolk × Mule wethers, aged 21 months.

In experiment 1, in which long, lucerne hay was offered (10 animals per species; 14 days) goats ate more than sheep (33·2 v. 28·3 g dry matter (DM) per kg M daily; P < 0·05). In experiment 2, in which long, ammonia-treated barley straw was offered (eight animals per species; 21 days) consumption was also higher for goats (21·6 v. 16·4 g DM per kg M daily; P < 0·01). Freshly cut, chopped stinging nettle (Urtica dioica L.) was offered with treated straw in experiment 3 (eight animals per species). Over the 10 days, intake of nettle increased linearly and that of straw decreased, but nettle consumption was consistently higher for goats than sheep.

In each experiment, food refusals (0·2 of food offered) were of lower nutritive value (lower nitrogen, higher acid detergent fibre, lower digestibility in vitro) than food offered. Throughout, food refusals by goats were of slightly higher nutritive value than food refusals by sheep.

It is concluded that both sheep and goats are selective feeders under stall-feeding conditions, but the greater intake of roughage by goats cannot be attributed to their selection of more nutritive components.

In response to tethering, many sows develop seemingly non-functional repetitive behaviour (stereotypies), which may be performed for several hours in a day.

The quality and quantity of activity performed by sows with different degrees of adaptation to tethering was studied in relation to energy expenditure. Three groups of five sows were recognized: (1) High, sows which showed a high incidence of stereotyped activity after prolonged tethering; (2) T/Low, sows with limited experience of tethers; and (3) G/Low, the same sows as in group 2 after regrouping.

High sows were about three times more active than T/Low sows: the proportions of time involved in 24 h were 0·35 and 0·13 respectively. Most of the former sows' activity was in the form of sterotypies. The activity level of the G/Low sows was between that of the two tether treatments (proportionately 0·17 of 24 h). Both tethered treatments spent proportionately about 0·05 of 24 h in using drinkers compared with proportionately less than 0·02 of the time for the G/Low sows.

High sows produced proportionately 0·36 more heat than T/Low sows during the 12-h light period in each day. During this period, proportionately 0·40 and 0·20 of heat production from High and T/Low sows was associated with activity. The diurnal activity of the G/Low sows was associated with proportionately 0·24 of heat production.

Stereotypies and excessive drinker use accounted for proportionately 0·86, 0·52 and 0·24 of the activity of High, T/Low and G/Low sows. The proportions of metabolizable energy intake required for these activities were 0·23, 0·07 and 0·04 respectively for the three treatments. The study concludes that tethering is stressful when sows develop, and then indulge in frequent coping behavioural patterns which increase metabolic rate.

Models are described which utilize goal programming to maximize hay intake in the formulation of rations for ewes in the last 6 weeks of pregnancy. By treating the energy or protein allowances (or both) as goals rather than restrictions, rations in addition to the linear programming (LP) optimal solution are generated. The approach offers a flexible alternative to the standard LP approach by providing additional rations with known deviations from the allowances. A set of guidelines is given to determine which of these rations could be tolerated when the nutritional requirements cannot be satisfied.

Two prototype two-tiered pens were constructed for fattening pigs. The pens consisted of a solid or porous upper floor located 0-8 m above a slatted lower floor, with a short ramp joining the two levels. Food was available only on the upper level and water only on the lower. Eleven groups, each of 15 to 18 pigs were housed in the two-tiered pens for 8 weeks, starting at 10 weeks of age, while matched control groups were housed in a conventional pen offering the same amount of total floor space. During the 1st week, some pigs were slow to adapt to the two-tiered system and average weight gain was lower than in the control pen. Over the 8 weeks, however, weight gain and food conversion ratios were very similar in the two pen types. The animals made effective use of the two levels, and kept the upper level free from dung. Physical condition of pigs in the two-tiered pen was as good as, or better than, that of the controls. The two-tiered design offers several potential advantages in terms of animal production and behavioural problems.

The adhesion of Escherichia (E.) coli K88ac to epithelial cells of the small intestine was studied after slaughter in 564 crossbred pigs (Swedish Landrace x Swedish Yorkshire). E.coli K88ac adhered to epithelial cells obtained from different parts of the small intestine in 40·8% of the pigs studied. Performance data indicated that presence of the receptor resulted in poorer daily gain during the 1st weeks of life, but that it had a beneficial influence on daily lean growth during the fattening period (24 to 100 kg live weight).

Reaction to the muscle relaxant succinylcholine was investigated as a possible method of distinguishing the heterozygote from the normal homozygote at the halothane locus. Totals of 54 assumed heterozygotes and 67 assumed homozygotes received intravenous succinylcholine during halothane anaesthesia at 6 to 10 weeks of age. Three separate measures of the duration and severity of the muscular reaction to succinylcholine were all significantly increased in heterozygotes compared with homozygotes. The genotypic difference for one of the three reaction traits was significantly influenced by the day of testing. Due to overlapping distributions for the two genotypes, succinylcholine reactions did not offer a precise method of identifying individual heterozygotes. Although test mating to recessive homozygotes would still be required to be certain of eliminating the halothane gene, the gene frequency among prosepective parents for test mating could be substantially reduced by succinylcholine screening. Due to the expertise and time required, succinylcholine testing would probably only be worthwhile for the production of specialized homozygous lines at nucleus level.

In two experiments, straw diets were supplemented with a concentrate mixture containing either untreated or formaldehyde-treated soya-bean meal. In experiment 1, adult wether sheep were given straw/concentrate mixtures in a 3:1 ratio (air-dry basis) in restricted amounts. In experiment 2, these proportions were adjusted to 3:2 and the growing lambs were offered straw at proportionately 0·05 to 0·1 greater than that eaten daily.

In experiment 1, formaldehyde treatment of soya-bean meal depressed apparent nitrogen (N) digestibility (P < 0·001) although diet organic-matter digestibility was not affected. Formaldehyde treatment also tended to reduce N retention in experiment 1, whereas with growing lambs in experiment 2, it led to improved N retention. Plasma urea concentrations were reduced as a result of formaldehyde treatment of soya-bean meal. Digested N was more efficiently utilized by sheep given the treated soya-bean meal diet in experiment 2 but not in experiment 1. Lambs given the treated soya-bean meal diet tended to gain more live weight with marginally superior food conversion ratios while consuming similar amounts of dry matter as those given the untreated soya-bean meal-supplemented diet.

Four diets were formulated from cereals, animal and vegetable protein supplements and tallow, to contain digestible energy (DE) concentrations of 14·1 or 17·1 MJ/kg and crude protein concentrations of 12·7 or 17·0 g/MJ DE in a 2 X 2 factorial design. In each of two experiments, pigs were weaned and allocated to dietary treatments when 21 days old and were fed twice daily to appetite. In experiment 1, six replicates of four male littermates were used. They were individually fed in metabolism cages and continuous energy and nitrogen (N) balances were made from 28 to 63 days of age. In experiment 2, three male and three female pigs were slaughtered at weaning to determine initial body composition, and three replicates of four littermates of each sex were allocated to the dietary treatments. The latter were fed in treatment groups in flat-deck pens and slaughtered at 63 days of age.

In experiment 1, increased energy concentration reduced food intake only slightly and improved liveweight gain and food: gain ratio; higher protein concentration increased gains only at lower energy concentration. Daily N balance improved with increased energy and protein concentration but the response to protein was greater with the low energy diet. Dietary energy was efficiently utilized even with 163 g tallow per kg diet. From 63 days of age until slaughter at 60 kg all pigs were given the same grower diet to appetite. Performance was not affected by previous treatments.

In experiment 2, food intakes were higher than in experiment 1 and tended to be reduced to a greater extent with the higher energy concentration; live-weight gains were similar for all treatments and food: gain ratio tended to improve in response to higher energy and protein concentrations. Dietary energy level had no effect on carcass fat content but the higher protein level reduced fat deposition. N retention tended to be lower for the low energy, low protein diet compared with the other three diets. Dietary effects on the amino-acid composition of the carcass were small. Carcass amino-acid ratios at 3 and 9 weeks were similar to published values and there was a tendency for higher amino-acid concentrations (g/16 g N) at 9 weeks than at 3 weeks.

Two experiments were performed to examine the efficacy of a synthetic prostaglandin analogue, cloprostenol (‘Planate’, ICI) to induce parturition in the rabbit. In experiment 1, does were injected intramuscularly on day 28 of pregnancy with either saline or with 4·38 μg, 8·75 μg, or 17·5 ug cloprostenol; a fifth group comprised untreated controls. Experiment 2 included only the groups treated with 4·38 μg and 17·5μg cloprostenol and untreated controls. In both experiments, cloprostenol injection significantly reduced the length of pregnancy when compared with saline-injected and untreated controls. Of the does treated with cloprostenol, 25 out of 26 kindled between 30 and 60 h after injection, whereas the variation in birth time in untreated and saline-treated groups was much greater (range 26 to 140 h). Litter birth weights tended to be lower in cloprostenol-treated does because of their precocious delivery but this did not appear to reduce pup viability. In both experiments, the proportion of pups dead at birth tended to be higher for does which did not receive cloprostenol (0·22 v. 0·10). Deaths between birth and weaning were similar on all treatments. Conception rate following mating 1 day after parturition appeared to be unaffected by cloprostenol treatment, as was milk yield during the 1st week of lactation.

The voluntary intake and digestibility of four hays were measured with eight sheep using two 4 × 4 Latin squares. Measurements were made during the last 8 days of each 3-week period. The degradation characteristics of the hays were measured by incubating samples (in nylon bags) for 12, 24, 48 or 72 h in the rumen of four sheep fitted with rumen cannulae and given a good hay. The exponential p = a + b(1 − e−α) where p = degradation loss, t = time, and a, b and c are constants, was fitted. The potential degradability (defined as a + b) of the dry matter (DM) of the four hays was 0·76, 0·66, 0·54 and 0·46 with corresponding voluntary intakes of 71, 62, 52 and 45 ± 2·9 g DM per kg M075 per day. The in vivo digestibilities were 0·61, 0·59, 0·46 and 0·45 (s.e. 0·013) respectively and corresponded to 23-, 25-, 31- and 67-h degradation. Voluntary intake was better related to potential degradability (and degradability at 12, 24, 48 and 72 h) than to in vivo digestibility. It is concluded that the degradation characteristics of forages may have useful application in predicting voluntary intakes, and that potential degradability could be used to define the rumen (jegradable nitrogen content necessary with any particular forage.

Female reproductive performance over four parities was studied for lines of mice selected for one three criteria: appetite (A), total lean mass (P), or proportion of fat (F). Female mice were first bred 8 weeks of age, and thereafter at intervals of about 7 weeks until fourth parity when they were dissected in late pregnancy to measure components of litter size.

The high A lines had higher litter sizes at the first three parities and higher ovulation rates, numbers of implantation sites and live foetuses at the fourth parity than the low A lines. The high P lines were also higher than the low P lines for each of these traits. In contrast, litter sizes and ovulation rates differed little between the high and low F lines. Fitting body weight as a covariate removed the high-low differences in ovulation rate and litter size between the P lines, but not all the differences between the A lines.

Pre-implantation survival at the fourth parity was slightly lower in the high than in low A and in high than in low P lines. Differences in post-implantation survival were very small. No component of prenatal survival differed substantially at fourth parity between the high and low F lines.

Differences in fertility at each parity and the percentages of females surviving to the end of the study were small. At each litter, dams of the high A lines produced heavier total weights of litters at 12 and 21 days than dams of the low A lines and the corresponding high-low differences in the P lines were larger. There were only small differences in these traits between the F lines. When litter size, fertility and survival were summed over parities, the average total number of young produced per female was substantially higher in the high than in the low A lines (5·0 young born alive or dead) and the P lines (7·2), but the high-low difference was small in the F lines (2-0). For all lines, litter size at first parity gave a reliable indication of reproductive rate during a major portion of the reproductive lifespan.

Seventy-two animals were used in an experiment to study the response of first-litter sows to graded increases in daily food intake during a 28-day lactation. Six food intakes, ranging from 1·5 to 4·8 kg/day were compared. The results showed that both live-weight loss and backfat loss during lactation increased linearly as food intake decreased (P < 0·01).

Subsequent ovulation rate was unaffected by food intake but both weaning to mating interval (Y,, days) and the proportion of sows exhibiting oestrus within 8 days of weaning (Y2)improve d linearly with increase in daily food intake during lactation (X, kg) (P < 0·01); the respective linear regressions being Y, = 39·0 - 6·26 and Y2 = 0·198A - 0·15. A sub-group of 24 gilts which were older at first conception (340·5 v. 213·5 days; P < 0·01) exhibited oestrus sooner after their first litters were weaned (12·8 v. 22·1 days; P < 0·05) than the remaining 48 younger animals.

Nitrogen balance increased linearly with food intake (P < 0·01) but even at the highest food intake, nitrogen balance remained negative (−15·5 g N per day). Food intake had no effect on the growth rate of piglets to 3 weeks of age but in the 4th week of lactation there was a quadratic increase in piglet growth rate as sow food intake increased (P < 0·01).