The inheritance of the time taken to react to halothane anaesthesia was examined as a possible quantitative measure of penetrance, which might allow the advantage of the halothane gene in lean content to be separated from its disadvantage of stress susceptibility. Restricted maximum-likelihood analyses were conducted on a total of 2207 pigs from 118 sire families in British Landrace and Pietrain-Hampshire lines selected for a high frequency of positive halothane reaction over 6 years. Reaction time averaged 94 s with a CV of 0·53, and was significantly influenced by line, season and live weight, but not sex. Estimated heritabilities averaged 0·07 (s.e. 0·06) and 0·16 (s.e. 0·12) in the two lines respectively, giving a pooled estimate of 0·09 (s.e. 0·05). Due to the high CV, family selection with a heritability of around 0-1 could be expected to give a rapid genetic change in reaction time. It is therefore concluded that selection for slower reaction to halothane could provide a means for reducing the incidence of stress susceptibility while retaining the advantage of the gene in lean content. However, further evidence is required on the correlation of reaction time with stress susceptibility and lean content.

The relationships between body fat depots and body condition score (BCS) were determined in 52 adult Rasa Aragonesa ewes aged 10 (s.d. 2) years and ranging in BCS from 1·5 to 4·5. BCS of each ewe was assessed by three people, the repeatability within individuals being 90% and between individuals 80%. The ewes were weighed before slaughter. After slaughter the omental, mesenteric, kidney and pelvic fat were separated and weighed. The fat of the left side of the carcass was separated into subcutaneous and intermuscular depots. The relationship between live weight and BCS was semilogarithmic and those between fat depots and BCS were logarithmic. Regression analysis was also used to describe the relationships between the various fat depots and BCS or live weight. Of the variation in total fat weight, proportionately 0·90 was accounted for by variations in BCS, while 0·84 was accounted for by variations in live weight. For individual fat depots proportionately 0·86 to 0·90 of the variation was accounted for by variation in BCS and 0·69 to 0·79 by variation in live weight. BCS was a better predictor than live weight of the weight of both total body fat and the individual fat depots.

A curvilinear regression between BCS and live weight showed that the increases in live weight for a unit change in BCS was 7, 10, 12 and 16 kg for each one point increase in BCS from 1 to 5 respectively.

The tail fat depot (tail fatness score) was assessed in the same ewes by score on a three-point scale. Of the variation in the weight of individual fat depots, proportionately 0·79 to 0·86 was accounted for by variation in tail fatness score. Thus the tail fatness score could be used as an additional method of assessing body condition in the Aragonesa breed.

Purebred lambs from three breeds (East Friesland, Oxford and Texel) were fed to appetite and treated with recombinant DNA-derived bovine somatotropin (BST) at 0·05, 0·10 or 0·20 mg/kg per day or a placebo between 19 and 27 weeks of age.

BST maintained growth over the later stages of treatment but did not affect average daily live-weight gain over the whole treatment period. Food intake was decreased and food conversion efficiency was improved by BST treatment. However, carcass weight and killing-out proportion were decreased by BST treatment in all breeds. Consistent breed differences were observed. Oxford lambs had higher live weights and carcass weights than the other breeds but no breed × treatment interactions were apparent. Ultrasonic backfat depth (mean of measurements at 13th rib and 3rd lumbar vertebra) was reduced by BST treatment in the Oxford (the fattest) and Texel lambs but not in the East Frieslands (the leanest). Ultrasonic muscle depth was not affected by BST; East Friesland lambs had considerably smaller muscle depth than the other breeds.

In the loin joint, BST decreased fat cover and subcutaneous fat proportion and increased longissimus dorsi proportion. There were also marked breed differences with Oxfords fatter than the other breeds. BST treatment did not affect any of the meat quality indicators but some differences between breeds were apparent in ultimate pH and colour of the muscle. Fatty acid composition of the subcutaneous fat was affected by breed but not by BST. East Friesland lambs had higher concentrations of unsaturated and branched chain fatty acids than the other breeds.

A mammogenic response (increased mammary development and some secretory activity) to BST was observed in some female East Friesland and Texel lambs but not in Oxford lambs.

Phenotypic and genetic analyses of the litter traits total number born, number born alive and total birth weight were conducted on data from two lines of pigs, line A, a synthetic largely of Landrace origin, and line B, derived from the Large White breed. The data were collected from closed herds of the Cotswold Pig Development Company Limited and comprised 1018 litters in line A and 863 litters in line B. Estimates of heritability and repeatability were low for all traits and consistent with other estimates in the literature, for number born alive being respectively, 0·07 (s.e. 0·04) and 0·15 (s.e. 0·04) in line A and 0·12 (s.e. 0·04) and 0·14 (s.e. 0·04) in line B. There was no evidence of an effect of the size of litter into which a female was born on her subsequent reproductive performance.

An experiment was conducted to evaluate the effects of diet on fur colour and quality of bromocriptineand melatonin-induced winter pelage in mink. At weaning, 90 standard dark female kit mink were assigned randomly to one of two dietary regimens. Diet 1 (no. = 30) was a basal ranch mink diet, and diet 2 (no. = 60) was the basal diet, supplemented with liver and eggs. On 26 June 1986, mink given each diet were assigned to treatment (no. = 15) and control groups (no. = 15). Animals receiving diet 1 were treated with 120 mg melatonin implants (silastic) while those given diet 2 were treated with 120 mg melatonin implants, 60 mg bromocriptine pellets, or 60 mg bromocriptine pellets plus 18·6 mg melatonin implants (silastic). Control groups on each diet received no implants. Subsequently, fur growth was measured at biweekly intervals. Mink treated with 120 mg melatonin, 60 mg bromocriptine, and 60 mg bromocriptine plus 18·6 mg melatonin all moulted 1 month earlier than controls and exhibited significantly greater fur growth during the months of August and September (P < 0·05). Mink implanted with 120 mg melatonin, and bromocriptine plus melatonin were considered to be in fully prime pelage by mid October and were pelted by October 23. Mink receiving bromocriptine alone were not considered to be in prime pelage in October and were pelted in December with controls. Neither diet supplementation with liver and eggs, nor treatment to induce early fur growth had an effect on fur colour or quality. It was also concluded that treatment of mink with bromocriptine may not completely mimic the effect of exogenous melatonin on winter fur growth.

The effect of routine induction of parturition on some reproductive and productive parameters during a year-long trial in 50 California doe rabbits allocated in two groups of 25 animals (treated and control), was studied. Intramuscular injections of 50 ug of the synthetic analogue of prostaglandin F2ct (Etiproston), were given at 10.00 h on day 29 of pregnancy. Control animals were untreated. When compared with the controls, treated does showed a significant reduction in the individual weight of pups at birth (49·7 (s.e. 0·41) and 52·2 (s.e. 0·53) g), number born dead per litter (0·42 (s.e. 0·11) and 0·81 (s.e. 0·16)), and parturition interval (42·9 (s.e. 1·5) and 53·5 (s.e. 1·7) days), and an increase in both sexual receptivity on days 6 to 9 post partum (70·4% and 43·0%), and in the conception rate to remating on days 6 to 7 post partum (82·2% and 66·6%), respectively. Litter size at birth, overall conception rate, mortality from birth to weaning, litter weight at 21 days, litter size at weaning, milk production, and mortality of does were not affected by the prostaglandin treatment.

Ninety-nine indigenous Greek goats (Capra prisca) on natural pasture were used to study reproductive performance as affected by method of breeding. At the beginning of the breeding season oestrus was induced with 45 mg fluorogestone acetate-impregnated vaginal sponges and 300 to 500 i.u. PMSG, given on day 15. The animals were separated into groups of 33 for mating: (i) by natural service (natural mating); (2) by artificial insemination with fresh semen (AI fresh); and (3) by insemination with frozen semen (AI frozen). Alpine bucks and Alpine semen were used for natural mating and AI of does.

No effect of method of breeding was found on gestation length and sex ratio. Reproductive performance was significantly affected by method of breeding; at 21 days after insemination, fertility of does bred with fresh semen (69·7%) was comparable with that obtained with natural mating (72·7%) but the fertility of does bred with frozen semen (48·5%) was much lower. This difference was statistically significant at kidding (P < 0·05). Litter size was 2·14 and 1·86 (P < 0·05) for the AI fresh and AI frozen groups, respectively, and was 1·96 for the natural mating group. More multiple litters were obtained with the AI fresh group (P < 0·05). It is concluded that, induction and synchronization of oestrus and ovulation at the beginning of the breeding season gave reproductive performance with fresh semen comparable to that obtained with natural service, but use of frozen semen gave unsatisfactory results.

Three-week old piglets were subjected to two levels of moderate, chronic cold stress immediately post-weaning and inoculated orally or by aerosol with an enterotoxigenic strain of Escherichia coli. Oral challenge, as well as both piglet-produced and artificial aerosols of E. coli were capable of inducing infection. In infected animals, live-weight gain and food conversion efficiency were significantly worse at 15°C than at 20° or 30°C. The incidence and severity of diarrhoea was greatest at 15°C and least at 30°C, but only in those piglets fed ad libitum. Piglets fed at a restricted level kept at 15°C did not become infected or suffer a check in growth after inoculation.

In the absence of other risk factors, piglets kept at thermoneutrality are unlikely to suffer post-weaning diarrhoea even in the presence of an enterotoxigenic strain of E. coli. Diarrhoeic piglets did not exhibit the normal rise in food intake at temperatures below their thermoneutral zone. Traditionally, the design specification and control of the thermal environment in a piggery has been based on the performance of predominantly healthy pigs but the results of this study imply that the additional criterion of health can now be used.

Rumen microbial attachment to food particles had a significant negative correlation with cell wall contents, cellulose and acid-detergent fibre (ADF) (P < 0·01) and a non-significant correlation with lignin, total phenolic content, condensed tannins and protein precipitation capacity. Microbial colonization was significantly positively correlated with in sacco dry-matter loss (DML) at 48 h of rumen incubation (P < 0·01). The cell wall contents and ADF were good predictors of DML. The relationship of DML (Y) with cell wall contents (X) and ADF (X') were Y = 1·012 – 0·0011Z, r = –0·89 (P < 0·01, no. = 10) and Y = 0·977 – 0·0014X', r = –0·88 (P < 0·01, no. = 10), respectively.

Three replicates of three group sizes (six, 18 and 36) of grower pigs were housed with the same space allocation (0·66 m2 per pig), feeding and drinking space per animal. The animals were mixed and kept together for a period of 22 days. They were given food ad libitum, were weighed weekly and a record kept of the group food intake for the 22-day period. Weight at mixing had a significant effect on weight gains during the 1st week. There was a significant interaction between group size and replicates for weight gains; generally weight gains were lowest in the group size of 36 animals during the first 2 weeks, but in the 3rd week there was no difference between the group sizes. Sex had no effect on weight gains. The variation in weights between group members were significantly greater in the group size of 36 than in the group sizes of six and 18 at the start of the trial, but at the end of the trial there was no difference in the variances of weights in the three group sizes. There was no difference between the group sizes in the variances of the weight gains. There was a significant positive correlation (r = +0·36) between weight at mixing and weight gain for the group size of 18. Group size had no effect on food intake, but the food conversion efficiency of the animals in the group size of 36 was significantly poorer than in the group sizes of six and 18.

Methods of inducing ovulation 3 weeks prior to the onset of the breeding season were evaluated in lactating adult red deer. Following 11 days of intravaginal progesterone pre treatment, hinds were either untreated (control), or given 300 i.u. PMSG i.m. or 500 mglh GnRH s.c. by osmotic pump. All hinds were laparoscoped 7 days after progesterone withdrawal to record the presence or absence of a corpus luteum on the ovaries, Laparoscopy showed 0113 control, 11113 PMSG and 8/13 GnRH-treated hinds ovulated indicating that during lactation, both methods of inducing ovulation are similarly effective, However, although these treatments induced ovulation, fertility as assessed from calving records, was poor.

Sixty crossbred gilts, comprising 15 groups of four littermates from large litters (> 12 pigs) were used. The experiment was designed as a 2 × 2 factorial, with two initial live weights (light (L) or heavy (H)) and either a low (lp) or high (hp) plane of feeding during the rearing period and post mating within each litter group. The hp gilts were significantly heavier (P < 0·001) and had thicker backfat (P < 0·001) than the lp gilts at first oestrus. The Hhp gilts reached puberty 26·4 days earlier than the Hip gilts (P < 0·05). Level of food intake significantly influenced ovulation rates and total embryo numbers, the hp gilts shedding on average 2·4 more ova and having 1·9 more embryos than the lp gilts 28 to 35 days post mating (P < 0·05). However, due to somewhat higher embryonic mortality in the hp gilts, the mean number of live embryos was not significantly higher than for the lp gilts (P < 0·05).

Litters of piglets were given ad libitum access to a sow-milk replacer (SMR) during lactation (200 g SMR per I) and the 1st week after weaning (100 g SMR per I). Weaning was at 3 and 4 weeks of age in the first and second studies respectively. SMR was readily consumed but was associated with a high incidence of scouring, reduced intakes of creep food, and (in one study) increased mortality. There was a trend towards increased litter weight in the 4-week weaning study only.

The effects of the halothane gene on growth and performance were estimated from British Landrace positive and negative selection lines and crosses between the lines. A total of 214 full-sib pairs were performance tested from 25 to 85 kg live weight on either ad libitum or scale (0·69 g/g ad libitum food intake) feeding. Half-sides of 45 carcasses were fully dissected.

In the crosses, growth and performance did not depend on whether the sire or the dam was from the positive line. Carcass length, conformation score, eye muscle area and incidence of pale, soft, exudative meat (PSE) were all intermediate in the crosses. Given food ad libitum, the crosses had increased appetite and growth rates which resulted in increased backfat depths. However, in the fully dissected carcasses, the crosses were intermediate for lean proportion. Although the crosses gave a net economic advantage, the incidence of PSE may be unacceptably high for commercial exploitation.

The effects of mixing on agonistic behaviour and performance were studied in 90 individually fed pigs, grouped at a mean live weight of 23 kg by one of the following three methods: (1) six unmixed littermates; (2) three pigs from each of two litters; and (3) one pig from each of six litters. Unmixed animals (treatment 1) did not fight and the mode of fighting differed between treatment 2 and 3. Mixing decreased daily weight gain in the period 23 to 100 kg for barrows, but not for gilts. For gilts, food conversion efficiency was negatively correlated with the number of received attacks in the observation period (80 min after mixing), and for the barrows to fighting injury scores.

This experiment was designed to study the effects of stocking density in transit and the use of electric goads on pig welfare and subsequent meat quality. Sixty-four pens, totalling 1400 commercial crossbred hybrid pigs, were transported from a farm to a large commercial abattoir at either high (0·3 m2 per pig) or low (>0·4 m2 per pig) stocking densities. The lorry drivers loaded and unloaded the pens of pigs at either end of their journey with, or without, an electric goad. Similarly, lairage men moved groups of pigs from their lairage pens to the stunning and slaughter area with, or without, goads. Consequently, eight possible treatment combinations arose from this 2 × 2 × 2 factorial experiment. About 20 h after slaughter, the fibre optic probe (FOP) value of the longissimus dorsi muscle was recorded and carcasses were scored for the extent of skin blemish. Pigs in high stocking density groups (HSD) had lower FOP values than those on low stocking density groups (LSD) (P < 0·05) and more severe skin blemish (P < 0·001). The effect of goading in transport or in the lairage, had no significant effect on the FOP values. However, the skin blemish data showed a significant interaction between the use of goads during transport and the stocking density treatment (P < 0·05). This interaction implied that the use of goads when loading pigs at a HSD was associated with a reduction in skin blemish. Conversely, the lowest skin blemish frequency was observed in the LSD treatment group handled without the aid of goads. Pigs in the HSD groups were visibly more skin damaged and exhibited evidence of rectal prolapse which was absent in pigs transported at LSD. Lower stocking densities are to be recommended as carcass, meat quality and pig welfare are probably improved. The use of goads is associated with a higher degree of carcass damage unless pigs are to be densely packed during transport.

Live-weight growth was studied for 64 female, 64 castrated male and 64 intact male indigenous Nigerian pigs at 16 ages from birth to 672 days. The weights obtained were fitted into four different growth functions to derive prediction equations for the models used. The quadratic (W = a + bt + ct2) and the Schmalhausen functions (W = at) described live-weight growth better than the simple linear function fW = a + bt). Estimating live-weight growth using Brody's function (Y = aebt) gave the least exact predictive ability. Linear growth in indigenous Nigerian pigs occurred between 112 and 336 days. Castrated male pigs exhibited higher live-weight growth rates than either the female or intact male pigs. Differences in the prediction of live weights using the four growth functions and the actual live weights are presented and discussed.

Fourteen adult ewes from each of three breeds, Karagouniko (K), Serres (S) and Chios (C), were maintained, barren, as a single flock at Diavata (latitude 40·5°N) for 2 years. Oestrus was checked twice daily by vasectomized rams for 17 months from April 1979. For K, S and C ewes, respectively, the mean dates of onset were 7 August (s.e. 6·5), 31 July (s.e. 8·2) and 28 July (s.e. 7·3) (P < 0-05) and the spread of first oestrus extended to 100, 94 and 95 days, respectively. Over all breeds, the dates of first oestrus ranged from 23 May to 19 September. Mean dates of last oestrus were 16 April (s.e. 8·5), 5 April (s.e. 9·5) and 20 May (s.e. 7·0) (P > 0·01) and the mean durations of the breeding period were 253 (s.e. 11·0), 247 (s.e. 12·2) and 301 (s.e. 10·2) days, respectively (P > 0·01). In the second season, the mean dates of first oestrus were 4 September (s.e. 2·4), 28 August (s.e. 5·1) and 25 July (s.e. 6·2), respectively (P < 0·01).

The potential of using low glucosinolate full-fat rapeseed meal (FFR) in the diets of early-weaned piglets was investigated in this experiment. FFR (containing 17 (xmol total glucosinolates and 2·8 mg erucic acid per g of whole seed) was used on an isonitrogenous basis at either 200 g<kg or 400 g<kg to replace full-fat soya-bean meal. Four replicates of three contemporary pen groups of 10 piglets weaned between 3 and 4 weeks of age were randomly allocated at a mean initial weight of 8·41 (s.e. 1·105) kg to the three dietary treatments. The experimental diets were given for 3 weeks. Inclusion of FFR significantly depressed food intake, daily live-weight gain and food conversion. There were no significant differences between the performance of piglets given either 200 or 400 g FFR per kg. Intakes of the diets containing FFR per unit of metabolic body weight as a proportion of the control diet decreased from about 0·85 to 0·75 from the 1st to the last week of the feeding period. This suggested that the acceptability of diets containing FFR decreased with time, possibly due to the presence of unpalatable and perhaps antinutritive factors which may include glucosinolates although present at relatively low concentrations. It was concluded that the feeding value of FFR would need to be improved by development of oilseed rape varieties with much lower levels of glucosinolates.

Mixing pigs from different social groups is known to cause turmoil which often results in skin lacerations as well as dark, firm and dry meat. Nine hundred and sixty commercial crossbred pigs were used for this experiment, divided into eight consignments. Within each consignment the pigs were divided into groups of about 15. The pigs in each group had coexisted for at least 6 weeks prior to slaughter. Thirty min before loading for slaughter, groups of pigs were either mixed with unfamiliar pigs or not mixed. Similarly, on arrival at the abattoir, groups of pigs were either mixed or not mixed. Hence there were four possible treatment combinations: pigs mixed with unfamiliar animals at loading, mixed at unloading, mixed at both points, or pigs which had remained in their social groups for at least 6 weeks prior to slaughter. Carcasses were dressed according to normal practice. After 20 h in the chiller room carcasses were assessed for skin blemish and fibre optic probe (FOP) values were measured in the longissimus dorsi muscle. Mixing pigs at either loading or unloading, or at both points, had no significant effect on the FOP value, but it did have a significant effect on the frequency of skin blemish values. Skin blemish values increased due to mixing at the farm (+0·36, Meat and Livestock Commission scale) however mixing at both places did not have an additive effect. The results indicate that the ideal movement system might be to keep pigs in their farm pen social groups until the point of slaughter.