Forty Landrace × (Landrace × Large White) gilts were randomly assigned at 70 days of age to each of two rearing treatments. The two treatments were: (1) gilts reared with gilts but kept in complete isolation from other pigs, and (2) gilts reared with visual, aural, olfactory and limited tactile contact with a mature boar. At 160 days of age, all gilts were subjected to a pen change and housed adjacent to either a mature boar for the first time, or to a different mature boar from that with which they had contact during the rearing phase. In addition, gilts were exposed to a mature, vasectomized boar for 30 min each day. They were served twice at second oestrus and the reproductive tracts were examined at slaughter 21 days later to determine ovulation rate and embryo survival. The presence of a mature male during the rearing phase had no effect on the attainment of puberty. There were no significant differences between treatments 1 and 2 for age at puberty (168·1 and 166·9 days respectively), weight at puberty (74·0 and 75·7 kg respectively) and the interval from movement and boar introduction to puberty (8·3 and 7·4 days respectively). The rearing treatments also had no effect on ovulation rate or embryo survival.

Carcass composition and quality and eating quality of the m. longissimus dorsi (LD) were compared in 15 entire male (ram) and 15 female (ewe) pure bred Dorset Down lambs (carcass weight range 12 to 23 kg).

Rams grew 28 g/day faster than ewes, taking on average 2 weeks less to achieve 35 kg live weight. At the mean carcass weight of 16-8 kg, ram carcasses contained more lean (42 g/kg carcass weight) and bone (19 g/kg) and less fat (subcutaneous, 33 g/kg; intermuscular, 28 g/kg; perirenal-retroperitoneal, 14 g/kg) than ewe carcasses.

At the same level of fat cover in the commercially prepared side, ewe carcasses required more trimming of subcutaneous fat than rams. However, there was more intermuscular fat (which is not removed by conventional cutting) in the ewes; consequently their saleable meat contained 51 g/kg more fat and 37 g/kg less lean than that from rams.

The roast LD was invariably tender and the eating quality of LD from rams was as desirable as that from ewes, while overall eating quality compared favourably with that of animals studied previously. There was no evidence of an undesirable sexual odour or flavour in ram meat.

With early maturing breeds, which can be finished off grass, non-castration of entire males offers the opportunity of improving the efficiency of lean meat production whilst retaining good carcass and eating quality.

In two separate experiments pigs were weaned at 14 or 28 days and heat production was determined in an open-circuit respiration chamber at temperatures above and below the lower critical temperature (Tcl) at intervals during the post-weaning period.

With 14-day weaned pigs the mean 24 h heat production above Tc1 averaged 267, 328, 474 and 554 kJ/h per m2 at 3, 9, 15 and 21 days post weaning respectively. The mean thermal conductance (H/AT, kJ/h per m2 per °ΔT, where H is total heat production, m2 is the surface area calculated as 0·097 M kg0·633 and °Δ is the difference between rectal temperature, taken at 39°, and air temperature) below TC1 was calculated as 20·5, 20·1, 23·1 and 24·2 at 17, 23, 29 and 35 days of age respectively and the corresponding values for Tc1 were 25·9, 23·0, 18·4 and 16·0°C.

With 28-day weaned pigs the mean 24 h heat production above Tc1 averaged 280, 361 and 445 kJ/h per m2 at 3, 9 and 15 days post weaning. The calculated values for H/ΔT were 19·7, 20·8 and 21·6 and the corresponding values of Tcl were 24·8, 21·7, and 18·8°C at 31, 37 and 43 days of age respectively.

The results are discussed in relation to previous studies on 10-day and 28-day weaned pigs and in relation to the practical implications for pigs weaned into controlled-environment accommodation.

Five experiments, involving the hand milking of 53 farrowing sows, examined aspects of colostrum yield during and soon after farrowing. The initial and abundant yield of colostrum from a teat (averaging 6 to 10 g/min) declined after several minutes of continuous milking. Thereafter, most colostrum was released in discrete ejections, possibly caused by discrete releases of oxytocin. Colostrum ejections varied greatly in their yield and duration, and were sometimes associated with the birth of a piglet, sounds of other sows nursing, or other factors.

Teats varied greatly in their yield. During the initial minutes of milking, the most anterior teats gave, on average, 3 to 5 times more colostrum than the most posterior teats, with a nearly monotonic decline from front to rear. However, the difference between anterior and posterior teats disappeared after several minutes of continuous milking. Stimulation of the anterior teats appeared to cause the release of more colostrum than did either the stimulation of the posterior teats or no stimulation of the udder at all. A strong sucking stimulus, applied to several teats by a milking machine, elicited a large, prolonged release of colostrum.

The results suggest that (1) much of the colostrum received by newborn piglets is obtained in discrete ejections rather than in a continuous manner; (2) appropriate stimulation of the udder by the piglets may be important to elicit maximum colostrum yield; and (3) a high initial yield from anterior teats, coupled with a higher yield when anterior teats are stimulated, may help to explain the piglets' preference for anterior positions on the udder.

A total of 219 lambs of the Welsh Mountain (W) and Scottish Blackface (B) breeds, and six types of crossbred with varying proportions of the two breeds from a cyclical crossbreeding experiment, were slaughtered in six groups at fortnightly intervals from 6 to 8 months of age. Each group had balanced numbers of each genotype and each sex. Genotype differences and effects of heterosis were estimated. Fat grades were assessed by farm staff before slaughter and Meat and Livestock Commission fat and conformation scores and external linear hindquarter measurements of each carcass were recorded.

At the same age, W carcasses were lighter (W: B = 0·86, W = 11·7 kg, B = 13·4 kg) but were more mature and had more kidney fat (W: B = 1·73) and higher fat and conformation scores especially in the loin region, but relatively shorter, thinner legs. At the same degree of maturity (carcass weight/estimated mature carcass weight), the Welsh carcasses had more kidney fat but the difference in leg measurements was reduced, and the differences for fat and conformation scores disappeared. When compared at the same grade, the Welsh lambs were 2 kg lighter and had higher conformation scores suggesting comparative undergrading, especially by the farm assessors. Results for crossbred lambs were as predicted from their breed composition and there was no evidence of heterosis.

The results suggest that at the same estimated carcass fatness, the Blackface has the potential to produce a heavier carcass but is later maturing, taking approx. 12 days longer to reach this degree of fatness.

In two experiments, the first with 96 pigs from 5 weeks of age and the second with 384 pigs from 3 weeks of age, high nutrient dense diets (HND) or conventional diets (CONV) were given with (50 g/kg diet) or without fish meal, up to slaughter at 90 kg live weight. Diets were unmedicated. In both experiments pigs were given food according to scales which equalized digestible energy intakes for the HND and the CONV diets. In experiment 1 pigs were individually fed; in experiment 2 group feeding was practised with pens of 16 pigs either floor or trough fed.

There was no mortality in experiment 1, but the mortality was high in experiment 2, particularly amongst those pigs receiving the CONV diet without fish meal. In experiment 1, in the first 56 days, inclusion of fish meal in the CONV and HND diets significantly improved growth rate but food conversion efficiency was significantly improved in the CONV diet only. Overall, up to slaughter, growth rate and food conversion efficiency were significantly poorer in pigs given the CONV diet without fish meal (cf. the three other diets) but the HND diets were significantly better than the CONV diet with fish meal. In experiment 2, overall there were no significant differences in performance between floor- and trough- feeding methods, CONV diets without fish meal gave significantly poorer growth rates in the first 56 days and overall than the other three diets, between which there were no significant differences. In both periods, for food conversion efficiency, fish meal inclusion was without significant effect in the HND diets but significantly improved the CONV diets, both of which were significantly inferior to the HND diets.

Nitrogen balance was measured in a series of experiments to determine the optimum balance between lysine, threonine and methionine plus cystine by successive additions of the free amino acids to a basal diet of barley, soya bean meal and tallow. The basal diet had a calculated digestible energy (DE) value of 14·5 MJ/kg and a crude protein content of 146 g/kg. The ranges of total lysine; threonine and methionine plus cystine tested were (g/kg) 6·6 to 11·8, 4·9 to 6·9 and 4·3 to 71, respectively. Latin-square designs were used involving a total of 33 pigs. Nitrogen utilization was optimized in pigs of 3 to 9 weeks of age when each kg of diet contained 10·5 g lysine, 6·4 g threonine and 5·0 g methionine plus cystine, corresponding to a ratio of 100: 61: 48. Thereafter, five diets were formulated in which the same ratio was maintained, but at different protein levels (129 to 192 g/kg). Again the diets were based on barley, soya bean meal and tallow supplemented with free amino acids. These diets were compared, in both nitrogen balance and performance experiments, with a conventional early-weaning diet with a protein content of 240 g/kg. All six diets had the same calculated DE value (14·5 MJ/kg). The N balance experiment was of Latin-square design and involved 18 pigs, and the performance experiment used 36 pigs fed individually from 3 to 9 weeks of age. A diet containing 0·99 g lysine per MJ DE (14·4 g lysine and 192 g balanced protein per kg) was considered to be adequate on the basis of the growth rate and food conversion efficiency results obtained.

1. Forty entire male pigs between 7 and 28 days of age and forty entire male pigs between 28 and 56 days of age were fed ad libitum basal diets of wheat and lupins containing 2·4 and 1·9 g of methionine per kg respectively. These were supplemented with 0, 0·3, 0·6, 0·9 and 1·2 g of synthetic methionine per kg of diet.

2. The methionine required for maximum performance and nitrogen retention was 3·0 g/kg of dry matter between 7 and 28 days of age and 2·5 g/kg between 28 and 56 days of age. These values were equivalent to 1·14 and 1·19g/100g of dietary crude protein at the two ages. The cystine contents of the diets were 3·7 and 3·1 g/kg respectively.

3. The concentration of methionine in the blood plasma did not give a clear indication of methionine requirement.

Forty multiparous Large White × Landrace sows were randomly allocated to five treatment groups: (1) control (C) — no partial weaning, movement or boar contact, (2) partial weaning (PW) only — sow and litter separated for 12 h/day, (3) PW + boar contact (B) in the sow's pen (1 h/day), (4) PW + sow moved (M) to empty pen (1 h/day), (5) PW + sow moved to occupied boar pen (1 h/day). Treatments were imposed from day 10 post partum until weaning at day 35 (s.e. 1). All sows were generously fed throughout lactation (7 kg/day) and in the post-weaning period (3 kg/day). One sow (treatment 5) exhibited lactational oestrus and was mated on day 33 of lactation, while the remaining sows on treatments 2 to 5 had significantly reduced (P < 0·05) weaning to remating intervals relative to control sows (4·84 v. 6·63 days, respectively). Litter creep food intakes tended to be higher in PW litters than controls (512 v. 376 g/day; P > 0·05), whereas sow live-weight gains during lactation were significantly increased when PW was employed (+0·43 kg/day v. −0·13 kg/day for control sows; P < 0·001). Partial weaning significantly (P < 0·001) reduced litter weaning weights (74·8 v. 87·0 kg for controls). However, there were no significant treatment effects on individual piglet weaning weights, subsequent growth performance of the weaned litters, or the size of litter subsequently produced by the sows.

Effects of the period of pre-slaughter lairage and diet on responses to post-mortem electrical stimulation (ES) were observed in 113 bulls and 18 cows. The efficiency of ES was assessed by the rate of the decrease of muscle pH. Stimulation was made at 80 V for 45 s. ES significantly decreased pH values at 1 h after slaughter. The effect was greater for animals on a normal diet than for those on a reduced diet. ES was also more effective for animals killed within 2 h after transportation to the meat processing plant than for animals slaughtered 24 h after transportation. There were no significant differences in the effect of ES between sexes. The basic requirement for effective ES is a good condition of animals at slaughter.

Eight diets based on barley and soya bean meal were formulated. Two basal diets, one of which included fish meal, were formulated to conform to the recommendations of the Agricultural Research Council (1981) for all amino acids except lysine. Four further diets were made by adding L-lysine to these diets, in two increments; the highest concentrations of lysine were also supplied in two further diets by the inclusion of a higher proportion of soya bean meal. Each diet was given ad libitum to 10 growing pigs, five castrated males and five females, which were housed and fed individually.

Measurements of performance were made over the weight range 22 to 55 kg. Carcasses were appraised after slaughter at a mean weight of 75 kg.

Addition of lysine, but not of soya bean meal, significantly increased daily food intake and carcass fatness. Daily growth and food conversion efficiency were not significantly affected. Because of the high food intake the daily lysine intakes on the basal diets greatly exceeded the suggested daily requirement and the results indicate that in such circumstances the response to the amino acid supplementation of an apparently inadequate protein may be negligible.

Mature Angus (A), Hereford (H) and Simmental (S) cows (16 each) that had been randomly assigned and fed a maize silage-based diet at different levels of intake during lactation were selected.

Lean and fat A, H and S cows were fed the maize silage-based diet individually to provide metabolizable energy (ME) intakes of 542, 506; 476, 437; and 624, 597 kj/kg0.75 per day respectively for 84 days. Daily weight gains of lean cows were greater than those of fat cows (0·40 v. 0·11 kg/day) even though daily ME intakes were less (55·2 v. 62·4 MJ/day). Theoretical estimates of ME requirements for maintenance were less for lean than for fat cows, and maintenance of A and H cows tended to be less than those of S cows.

These results suggest that cow maintenance requirements increased in association with fatness that resulted from the previously imposed nutritional regimes and tended to differ among cow breeds.

Data for 15 487 pigs taken from the first 8 years (1973–81) of the Meat and Livestock Commission's Commercial Pig Evaluation were used to examine the effects of sex, feeding regimen, slaughter weight and day of slaughter on muscle quality characteristics in 20 populations (pigs from different commercial breeding companies and control populations). The characteristics examined included pH measurements both at 45 min post mortem (pH,) and after overnight cooling (pH2), in the m. longissimus and m. semimembranosus. Visual assessments of m. longissimus colour and condition were also made.

The overall mean for pH, in the m. longissimus was 6·34; 0·12 of pH, values were less than 6·0. The proportion of carcasses visually assessed as either pale or wet was 0·116, and 0·027 were assessed as both pale and wet.

The populations were compared separately within each of three time periods (covering the full 8 years) since significant population × time period interactions were recorded for several characteristics. Within each period the populations differed significantly for all characteristics examined (P < 0·05); but with the exception of two extreme populations, the differences were relatively unimportant.

The effects of sex, feeding regimen and slaughter weight were negligible but the effect of day of slaughter was very important: the s.d. of pH1 was reduced by 0·15 when calculated within day but by only 0·01 when adjusted for all other factors.

Muscle quality characteristics were poorly correlated with carcass characteristics: the highest correlation within day of slaughter was −0·23, recorded between pH, and ham conformation score.

In heifers, plasma progesterone levels were low (<0·3μg/l) from the 59th to about the 15th day before puberty (defined as the day when oestrus was first detectable by the fern pattern of dried cervical mucus). Plasma oestradiol-17β levels varied randomly within the range 1 to 4 ng/l over the same period, but then showed three peaks of about 6, 9 and 4 ng/l, respectively 8 days before puberty, on the day of puberty and 4 days later. The pre-pubertal oestradiol-17p peak was followed by a short period of elevated progesterone levels. Whether this oestradiol-17β peak induced ovulation is uncertain; it is however clear that a corpus luteum of normal life-span was not formed. The oestradiol-17β peaks on the day of puberty and 4 days later, when progesterone levels were rising rapidly, were typical both in magnitude and duration of those occurring before and after ovulation in post-pubertal oestrous cycles.

Four groups of does (16 per group) were remated either 1, 7, 14 or 21 days after parturition over a 1-year production cycle. Doe mortality rate was independent of treatment and overall was 0·27. The remating interval after parturition had no effect on conception rate, which was high on all treatments (0·86 to 0·93). The high overall conception rate resulted in more litters being born as the parturition to remating interval decreased. Expressed on a common 365-day experimental period the number of litters per doe was 8·9, 8·5, 7·8 and 6·7 (average s.e. of difference 0·33) for treatments 1, 7, 14 and 21 respectively. Litter size was not significantly affected by treatment and consequently the number of pups born per doe per year increased as remating interval decreased: 75·0, 73·4, 67·4 and 591 respectively. Pup mortality rate at birth and subsequently was high (0·42) on all treatments and the number of pups weaned per doe per year for treatments 1, 7, 14 and 21 was 48·3, 43·5, 40·0 and 33·3 respectively. Pup birth weight, 21-day litter weight and weaning (25-day) weight were all unaffected by treatment, as was doe body-weight change.

The proportion of Holstein blood for each of 725 bulls progeny tested by the Milk Marketing Board, was obtained from a three generation pedigree. The bulls were grouped according to the proportion of Holstein blood and the means and standard deviations for their progeny tests for Beef Shape Score calculated. Only bulls with Beef Shape Scores based on an effective number of daughters of at least 20 were included. The mean Beef Shape Score decreased from 99·6 in pure Friesian bulls to 88·5 in pure Holsteins. Only four bulls within the pure or three-quarter (0·75) Holstein groups had a Beef Shape Score above the overall mean of 98·6 with the maximum being 102. The range of Beef Shape Scores for all bulls was 76 to 116.

The product moment correlations between Beef Shape Score and milk, fat and protein yields were −0·36, −0·35 and −0·32 respectively. These values were significantly different from zero (P < 0·01).

The occurrence of melanin pigmented wool fibres in the skirted white fleece wool from 1-year-old Corriedale ewes, having either least (group 1), most (group 3) or an intermediate level (group 2) of black nose skin pigmentation, was investigated. Thirteen of the 87 fleeces analysed had the equivalent of 10 to 389 isolated pigmented fibres per 100 g of scoured wool. The mean diameter of the pigmented fibres was similar to that of the fleece specimens analysed and they occurred singly or in small groups within individual staples. Large numbers of isolated pigmented fibres in fleeces were widely distributed, and constitute a serious problem of identification by visual inspection. Fibre darkness and the number of fleeces found with pigmented wool fibres were two measurements which showed a significant association (P < 0·001 and P < 0·05, respectively) with nose skin pigment group. With one exception from group 2 the results support the suggestion that the usual selection for dark nose skin in this breed may be antagonistic to selection for a white fleece. The pigmented lengths of fibres were found to be independent of nose skin pigment group.

Problems of making selection decisions among animals from several environmental groups with heterogeneous variance are discussed. Unless correction for heterogeneity of variance is made, animals will tend to be selected from the more variable groups, especially if selection is intense. This is an accurate and fair procedure only when the heterogeneity reflects real differences in heritability. It is shown that, if observations are expressed as deviations relative to the estimate of standard deviation from the group, the accuracy is high unless groups are very small.

Sixty-three Large White ♂ × (Landrace ♂ × Large White ♀) ♀ gilts were allocated to one of three treatments as follows: (i) boar contact for 20 h/day; (ii) boar influence through a mesh pen division for 20 h/day; and (iii) control, which had no boar exposure.

The experiment started when gilts averaged 156 days of age, and continued until either puberty was detected or the age of 210 days was reached. Analysis revealed significant differences between groups for proportion of gilts reaching puberty (0·76, 0·38 and 0·19), the interval from stimulation to-puberty (10·4, 34·1 and 36·7 days) and age at puberty (167·9, 192·2 and 191·2 days) respectively.