Plane of nutrition (PN) offered to ewe replacements during the rearing phase (8 to 17 months) and first pregnancy may affect reproductive and progeny performance when replacements are joined at ~19 months. The effects of PN offered to spring-born ewe replacements during their first winter (winter_1), second summer (summer_2) and subsequent winter (mid and late pregnancy; winter_2) were evaluated, over 3 consecutive years, using 287 ewe lambs of four genotypes: Charmoise×Scottish Blackface (C×SBF), Belclare×SBF (Bel×SBF), Belclare (Bel) and Belclare×SBF (heterozygous for a gene, either FecGH or FecXG mutations, that increases ovulation rate: BelMG×SBF). Ewe lambs were offered, daily, a deferred-grazed herbage allowance (HA) of either 0.75 or 1.75 kg dry matter during winter_1. During summer_2 the replacements were set-stocked to maintain sward heights of 4 or 6 cm. Ewes were housed during mid and late pregnancy (winter_2) and offered either medium or high-feed-value grass silage, thus yielding a 2×2×2 factorial design. Increasing HA during winter_1 and residual sward height during summer_2 increased ewe BW post joining (P<0.001) and at lambing (P<0.01), but had no effect (P>0.05) on number of lambs reared. Increasing HA during winter_1 increased lamb BW at birth (P<0.05) and reduced carcass fat score (P<0.05). There was a significant interaction between PN offered during winter_1 and summer_2 for average daily gain (ADG) from birth to 5 weeks (P<0.01) and from 5 to 10 weeks (P<0.05): progeny of replacements that experienced either a high or low PN throughout the rearing phase had lower ADG than lambs born to the replacements that experienced a low PN only during winter_1 or summer_2. Increasing PN during winter_2 increased ewe BW (P<0.001), lamb BW at birth (P<0.001) and weaning (P<0.05) and reduced the proportion of ewes that failed to lamb (P<0.01). Ewe genotype had a significant (P<0.001) effect on litter size (1.48 to 2.45), number of lambs reared, lamb BW at birth and weaning, lamb ADG and age at slaughter. It is concluded that, among the nutrition treatments examined, increasing PN during mid and late pregnancy had the greatest effect on ewe and progeny performance. Although increasing PN offered during winter_1 increased lamb birth BW, PN offered during summer_2 had no effect on lamb performance. There were no significant interactions between PN and ewe genotype.

The mobilization of fatty acids during food deprivation is a selective process studied in different species (humans, rodents, birds, viverrids). The aim of this work was to study the effect of fasting on selective mobilization in commercial pigs. A total of 16 barrows (Large White×Landrace (167 kg±12.5 kg live weight) were subdivided into two homogeneous groups, one subjected to 12 h and the other to 60 h of fasting (fasting time) before slaughtering. For each pig inner and outer backfat layer were sampled at slaughter and at ham trimming 24 h later (sampling time). Increasing the fasting time and the sampling time after slaughter caused an increase in the amount of free fatty acids in both layers. Therefore it can be argued that during fasting lipolysis is stimulated and remains active also after slaughtering. The factors that stimulate lipolysis determine a greater mobilization of unsaturated fatty acids than saturated ones. Thus fasting time may influence the suitability of pork for processing and conservation, since free fatty acids are more suitable for oxidation than the esterified ones.

Seventy-two entire male pigs (initially 28 kg body weight) were used to study the effects of by-product (pollard, rapeseed meal, peas and copra meal combined) inclusion level with or without expander processing, on growth performance and nutrient digestibility in a 3 ✕ 2 factorial arrangement of treatments. Productive performance and nutrient digestibility coefficients (no. = 6) were determined in individually fed pigs offered pelleted diets ad libitum containing a low by-product diet (350 g/kg), medium by-product diet (520 g/kg) and high by-product diet (752 g/ kg). The expanded diets were processed at 105ºC for 5 s at 35 bar pressure having been previously conditioned at 85ºC for 5 s. All diets were formulated using standard values for ingredients to have similar concentrations of digestible energy (DE) and ideal protein. Starch contents of 437, 401 and 314 g/kg and crude fibre contents of 48, 58 and 74 g/kg were recorded for the low, medium and high by-product diets respectively. No by-product level ✕ expander processing interactions (P > 0·05) were observed in growth criteria, carcass characteristics or nutrient digestibility. Expander processing decreased (P < 0·05) the apparent organic matter (OM), ash and energy digestibility of the diets, as well as the digestible energy content of the diets. The level of by-product in the diet had no statistically significant effect on the OM, protein and energy digestibility or the DE content of the diets. The increase in by-product inclusion levels decreased (P < 0·05) average daily gain (ADG) (0·899 v. 0·888 v. 0·854 (s.e. 0·014) kg/day) from 28 kg to slaughter and food intake (1·62 v 1·48 v 1·48 (s.e. 0·028) kg/day) in the 28 to 55 kg weight range. Expander processing had no effect on ADG, food intake or food conversion ratio. The increase in byproduct level decreased (P < 0·01) killing-out proportion (723 v 705 v 710 (s.e. 3·94) g/kg) and carcass ADG (0·684 v 0·651 v. 0·635 (s.e. 0·012) kg/day) (P < 0·05). Expander processing decreased (P < 0·05) killing out proportion (707 v. 718 (s.e. 3·22) g/kg). In conclusion, increasing the by-product content of the diet decreased ADG while expander processing had no effect on growth performance.

Half carcasses of 18 Pietrain and 18 Large White female pigs were dissected into 10 bone units. An allometric analysis of the weights of these units relative to total bone revealed increasing craniocaudal and distoproximal growth gradients. No differences in bone distribution were observed between the two breeds. Because of a difference in muscle distribution, the muscle: bone ratio in the femoral region of the Pietrain was greater than that of the Large White breed.

An experiment was carried out in Egypt using Giza White rabbits to investigate their lactational performance and to estimate the repeatabilities of milk yield and other litter traits. Data on 325 litters from 115 does fathered by 40 sires were used. Lactation traits involved milk yields during the first 7 days, 21 days and 35 days. Litter traits included litter size and weight at birth, number born alive, litter weight and gain at 21 days, litter size and weight at weaning and pre-weaning litter gain. Linear mixed models were used for analysing such data.

Phenotypic variation in milk yield was relatively high during the first 7 days, and decreased thereafter with advance of lactation stage. Year-season effects were significant for most litter traits, while month of kindling affected litter weight and gain at 21 days and milk yield during the first 7 days (P < 0·05 or P < 0·001). Litters kindled during winter had the highest milk yield compared with litters kindled in the other seasons. Milk production, litter size and weight and litter gain had curvilinear relationship with parity (P < 0·05 or P < 0·001). Sire of doe had no significant effects on litter traits studied. Repeatabilities of all traits were low and ranged from 0·001 to 0·134. Litter size and weight at birth were residually correlated with milk yield. Litter weight and gain at 21 days were significantly correlated with the lactational performance of the doe (P < 0·001).

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

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

A total of 120 Iberian pigs of the Lampiña line that grew under outdoor conditions were used to study the effect of the age at the beginning of Montanera period (AM) on meat characteristics and fatty acid (FA) profile of subcutaneous fat. AM period is a free-range fattening phase from November to February in which pigs ate mainly acorns and grass. There were two treatments with two AM (20 pigs per treatment); 18 (P18) and 12 months (P12). Barrows and gilts were in the same proportion within each treatment. All the animals were slaughtered at the same time (at the end of Montanera period) reaching an average 160 kg of body weight. Meat from P18 had less protein and was more red (a*) (P < 0.05), but tended to show higher intramuscular fat content (P < 0.10) than meat from P12. Loin from P18 had lower thawing (P < 0.001) and cooking losses (P < 0.10) than loin from P12. The fat from P18 had higher monounsaturated FA content than fat from P12 pigs (P < 0.01) due to the higher level of C18:1 (P < 0.01) and C20:1 (P < 0.001). However, fat from P12 had higher polyunsaturated FA content than fat from P18 pigs (P < 0.01) because of the higher level of C18:2 (P < 0.001). It is concluded that both 12 and 18 months are adequate AM for purebred Iberian pigs from the commercial point of view. However, if the aim is to produce high-quality dry-cured Iberian products, the P18 pigs would be more advisable because had better meat and fat characteristics than the P12 pigs.

Cattle breeds indigenous to Africa (Sanga) compare favourably to Bos indicus breeds with regard to adaptation to harsh environments. This study compared the meat quality of three Sanga breeds (Nguni, Tuli and Drakensberger), a Sanga-related breed (Bonsmara) and a B. indicus breed (Brahman) and supported these results with biochemical and histological measurements on the M. longissimus lumborum. Twelve young grain-fed steers of each breed were slaughtered and carcasses were electrically stimulated. All Sanga (and related) breeds, with the exception of the Tuli, had lower Warner–Bratzler shear force (SF) values at 2 and 21 days post mortem compared with the BR (P < 0.05). Measurements related to the calcium-dependent protease system and myofibrillar fragmentation explained the bulk of the variation among breeds, whereas variation in fibre type, sarcomere length and connective tissue properties gave less convincing support. With the exception of the Tuli, Sanga and Sanga-related breeds produced more tender (according to SF) meat than BR, mainly due to favourable calpain-to-calpastatin ratios. Small differences in colour, drip loss and cooking properties were found among breeds (P < 0.05).

The postpartum period is crucial in dairy cows and is marked by major physiological and metabolic changes that affect milk production, immune response and fertility. Nutrition remains the most important lever for limiting the negative energy balance and its consequences on general health status in highly selected dairy cows. In order to analyze the effect of a commercial micronutrient on intrinsic parameters, performances and the epigenome of dairy cows, 2 groups of 12 Holstein cows were used: 1 fed a standard diet (mainly composed of corn silage, soybean meal and non-mineral supplement) and the other 1 fed the same diet supplemented with the commercial micronutrient (µ-nutrient supplementation) for 4 weeks before calving and 8 weeks thereafter. Milk production and composition, BW, body condition score (BCS), DM intake (DMI) and health (calving score, metritis and mastitis) were recorded over the study period. Milk samples were collected on D15 and D60 post-calving for analyses of casein, Na+ and K+ contents and metalloprotease activity. Milk leukocytes and milk mammary epithelial cells (mMECs) were purified and counted. The viability of mMECs was assessed, together with their activity, through an analysis of gene expression. At the same time points, peripheral blood mononuclear cells (PBMCs) were purified and counted. Using genomic DNA extracted from PBMCs, mMECs and milk leukocytes, we assessed global DNA methylation (Me-CCGG) to evaluate the epigenetic imprinting associated with the µ-nutrient-supplemented diet. The µ-nutrient supplementation increased BCS and BW without modifying DMI or milk yield and composition. It also improved calving condition, reducing the time interval between calving and first service. Each easily collectable cell type displayed a specific pattern of Me-CCGG with only subtle changes associated with lactation stages in PBMCs. In conclusion, the response to the µ-nutrient supplementation improved the body condition without alteration of global epigenetic status in dairy cows.

Correlated responses in physiological traits to divergent selection on components of efficient lean growth identified physiological traits for use as predictors of genetic merit and provided a biological explanation for the between-selection line differences in protein and lipid deposition. Responses (differences between high (H) and low (L) selection lines) in protein metabolism during ad-libitum feeding were associated with divergent selection for daily food intake (DFI) (reduced serum creatinine concentration (H = 1·30 v. L = 1·56, s.e.d. 0·08 mg/dl)) and for lean growth rate on an ad-libitum feeding regime (LGA) (increased serum urea (H = 48 v. L = 36, s.e.d. 4 mg/dl) and creatinine (H = 1·74 v. L = 1·45 mg/dl)) concentrations, but not with selection for lean growth on a restricted feeding regime (LGS). Following 24-h fasting, responses in lipid metabolism, in the form of higher serum non-esterified fatty acid concentrations, were detected with divergent selection for both LGA (399 v. 248, s.e.d. 66 µmol/l) and LGS (H = 361 v. L = 107 µmol/l). The high LGS line appeared to ‘preserve’ protein to a greater extent than the high LGA line and similarly there was greater maintenance of lipid depots by the low LGS line compared with the low LGA line. A tentative ranking of the two pairs of lean growth selection lines on the basis of ‘importance’ of protein deposition would be high LGS, high LGA, low LGA and low LGS.

Coheritabilities for serum creatinine concentration with predicted lysine balance and lysine required for protein deposition (-0·17 and 0·17, s.e. 0·08) indicated that serum creatinine concentration may usefully be included in breeding value prediction for lysine requirement and protein deposition to increase the accuracy of predicted genetic merit.

Fasting did not increase the coheritabilities for serum creatinine concentration, so inclusion of serum creatinine concentration in a selection criterion for dietary lysine requirement or protein deposition does not require withdrawal of food before blood sampling animals.

Two isonitrogenous, isocaloric and isofibrous diets for finishing beef cattle differing only in their roughage constituents were compared in a feeding trial with Limousin bulls. A control maize silage (chop length = 9 mm) and wheat straw were the roughage sources of the former diet representing 0·23 and 0·09 of the dietary dry matter (DM) respectively. These roughage sources were fully replaced in the latter by the inclusion of a coarsely chopped maize silage (19 mm) at a level of 0·45 of the total dietary DM. Two balanced groups of 20 Limousin bulls (425·8 ± 20·3 kg live weight) each allotted in four pens were given the two diets ad libitum for a finishing period of 138 days. The different dietary roughages did not affect either bull growth performance (average daily gain = 1·39 ± 0·25 kg/day) or food conversion ratio. However, the diet containing the coarse silage significantly (P < 0·05) reduced the intake of both DM (8·30 v. 9·02 kg/day) and neutral-detergent fibre (NDF) (2·64 v. 2·92 kg/day). Although total ruminating time was similar for both diets, bulls given the coarse maize silage diet spent more time ruminating 1 kg of DM or NDF, probably due to the higher percentage of dietary forage NDF. No food selection activity towards specific chemical constituents was observed in either diet. Slaughter measurements and meat quality were satisfactory and unaffected by the type of dietary roughage. Based on cattle growth performance, feeding behaviour, and meat quality, the use of coarse maize silage as a dietary source of roughage can be considered a feasible alternative in beef cattle finishing.

The study was carried out to provide information on uniformity of commercial pigs on some of the most important traits determining pork quality: carcass, loin, ham and shoulder weights, fatness, drip loss, pH and colour. Three batches of pigs raised at the same farm and slaughtered at four different dates in the same commercial abattoir were considered. Batches included halothane-free females and castrated males, Duroc and Pietrain sire lines and two slaughter weights, but a common maternal line. The first batch was obtained using commercial Duroc sire boars, and included a total of 112 animals (56 castrated males and 56 females). The second batch used Duroc and Pietrain sire boars with the target to achieve two different final weights (105 and 115 kg live weight); 128 animals were controlled (64 castrated males and 64 females), 16 for each combination of sire boar, sex and final weight. The last batch used only Pietrain sire boars with 96 controlled pigs (48 castrated males and 48 females). The uniformity was measured by the coefficient of variation (CV) and the coefficient of dispersion (CD) for all data available, and for groups of common sex, sire breed and slaughter weight. Differences in uniformity were tested among traits and groups by using confidence intervals (CIs) at 95% confidence level (CI95%) for the CV and CD. Results showed a significantly lower uniformity for drip loss (CV = 40.4%, CI95% 36.9% to 44.7%; CD = 32.1%, CI95% 28.7% to 35.4%) and backfat (CV = 22.8%, CI95% 21.1% to 24.8%; CD = 18.3%, CI95% 17.1% to 20.2%) the pH being the most uniform trait (CV = 3.2%, CI95% 3.0% to 3.5%; CD = 2.6%, CI95% 2.4% to 2.9%). When comparing different ‘sire breed–sex–slaughter weight’ groups, no consistent sex and slaughter weight differences in uniformity were found, but animals from Pietrain sire breed showed a tendency to be less uniform for carcass traits than animals from Duroc sire breed. Nevertheless, variability within those groups was very high and often similar to that observed when considering all the animals from all the groups. Small differences were found comparing uniformity when using the CV or the CD. CIs of these coefficients have proved to be a simple and useful tool for testing differences in uniformity.

A field trial was conducted at 13 centres to investigate the effect of increasing feed intake on the day of mating on litter size of sows. From weaning to mating, control animals received 1·8, 2·3 or 2·7 kg food/day depending on the managemental procedure of the centre. Flushed animals were fed in the same way except on the day of mating when their feed allocation was doubled. Flushing did not significantly affect litter size when the overall results of all centres were considered (447 sows). Results for individual centres were also examined. A significant response to ‘flushing’ was obtained at only one of the 13 centres, where increasing feed intake from 2·7 to 5·4 kg on the day of mating significantly (P < 0·05) increased litter size by 1·3 ±0·52 pigs born.

1. Young adult and adult lactating British Friesian female cattle (heifers and cows) were individually fed ad libitum on perennial ryegrass silage (F) made with an additive of formic acid (3·41 of 85% acid/t fresh grass) or on a silage (FF) made from the same crop with an additive of 9·01/t of a mixture of equal volumes of formic acid and formalin (35% w/w solution of formaldehyde). Silage F was supplemented with a concentrate containing 50% dried grass and 50% barley at a low (L) or high (H) level of feeding; silage FF was supplemented with the same concentrate at the lower level only, either with urea at 2·0% of the silage DM (FFLU) or without urea (FFL).

2. Silage F had a lower pH (P< 0·001) and contained more lactic, acetic and total fermentation acids (P><0·001). The DOMD in vivo of the diet was lower (by up to 3 units) for treatment FFL than for the other treatments (P<0·05 in weeks 17 and 18).

3. Over weeks 4 to 18 of lactation the mean dry-matter intakes (DMI) of silage on treatments FL and FFL were similar, but silage DMI was 12 to 13% greater on treatment FFLU than on FL or FFL (P<0·05). Digestible OM intake was greater with FFLU than with FFL (P<0·01) and with FL (P<0·05).

4. Milk yields did not differ significantly between treatments and metabolic blood profiles were normal.

The aim of this study was to determine the effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and resumption of postpartum ovulation. For this study, 31 late-pregnant Holstein heifers were used. The heifers were assigned randomly into two treatments: (1) 500 mg sc injections of somatotropin (somatotropin treatment, n = 15) at −35 and −21 days, and, if pertinent, at −7 days from expected calving date and (2) no treatment (control group, n = 16). Blood samples were collected weekly from −5 to 7 weeks after calving. Heifers with progesterone concentrations in plasma above 1 ng/ml in two consecutive postpartum samples were considered as having resumed ovarian activity. A higher proportion (P = 0.04) of heifers treated with somatotropin resumed ovarian activity in the first 7 weeks post partum (73.3%; 11/15) compared with the control group (37.5%; 6/16). A higher number (P = 0.02) of heifers in the somatotropin treatment group also ovulated during the first postpartum follicular wave (53.3%; 8/15) compared with the control group (12.5%; 2/16), as indicated by the number of heifers ovulating in the first 3 weeks post partum. Pregnancy rate was not affected by treatments (P > 0.10) and averaged 40.0% (6/15) in somatotropin-treated and 25.0% (4/16) in control heifers when evaluated up to 150 days in milk. Somatotropin treatment increased the average daily milk production by 2.8 kg/cow per day (P < 0.0001) and reduced the somatic cell count (P = 0.009). Plasma IGF-I was higher (P < 0.05) for somatotropin-treated heifers in the prepartum period. Insulin and body condition score were higher (P < 0.05) and non-esterified fatty acids were lower (P < 0.05) for somatotropin-treated cows in the early postpartum period. In conclusion, somatotropin injection during the prepartum period in late-pregnant Holstein heifers was able to increase the proportion of heifers resuming ovarian activity early post partum, inspite of higher milk production.

A stochastic risk model was developed to estimate the time elapsed before overcrowding (TOC) or feed interruption (TFI) emerged on the swine premises under movement restrictions during a classical swine fever (CSF) outbreak in Indiana, USA. Nursery (19 to 65 days of age) and grow-to-finish (40 to 165 days of age) pork production operations were modelled separately. Overcrowding was defined as the total weight of pigs on premises exceeding 100% to 115% of the maximum capacity of the premises, which was computed as the total weight of the pigs at harvest/transition age. Algorithms were developed to estimate age-specific weight of the pigs on premises and to compare the daily total weight of the pigs with the threshold weight defining overcrowding to flag the time when the total weight exceeded the threshold (i.e. when overcrowding occurred). To estimate TFI, an algorithm was constructed to model a swine producer’s decision to discontinue feed supply by incorporating the assumptions that a longer estimated epidemic duration, a longer time interval between the age of pigs at the onset of the outbreak and the harvest/transition age, or a longer progression of an ongoing outbreak would increase the probability of a producer’s decision to discontinue the feed supply. Adverse animal welfare conditions were modelled to emerge shortly after an interruption of feed supply. Simulations were run with 100 000 iterations each for a 365-day period. Overcrowding occurred in all simulated iterations, and feed interruption occurred in 30% of the iterations. The median (5th and 95th percentiles) TOC was 24 days (10, 43) in nursery operations and 78 days (26, 134) in grow-to-finish operations. Most feed interruptions, if they emerged, occurred within 15 days of an outbreak. The median (5th and 95th percentiles) time at which either overcrowding or feed interruption emerged was 19 days (4, 42) in nursery and 57 days (4, 130) in grow-to-finish operations. The study findings suggest that overcrowding and feed interruption could emerge early during a CSF outbreak among swine premises under movement restrictions. The outputs derived from the risk model could be used to estimate and evaluate associated mitigation strategies for alleviating adverse animal welfare conditions resulting from movement restrictions.

1. Experiments were carried out during two winters on the effects of exposure, partial outdoor shelter and complete indoor shelter on individually penned pregnant Welsh Mountain ewes at an altitude of approximately 275 m. A single pelleted diet was given at several levels of intake.

2. In Experiment 1 ewes fed at an approximately maintenance level indoors had post partum live weights 0·9 and 1·4 kg greater than those fed at the same level in the partially sheltered and exposed pens.

3. The daily voluntary feed intake of ewes fed to appetite was 20% greater in the exposed and partially sheltered pens than in the indoor pens. But there were no consequent differences between post partum live weights, which were all higher than for ewes kept at maintenance intake.

4. In Experiment 2, when the weather was milder, the effects of exposure and shelter on ewes fed at the maintenance level were smaller and not statistically significant. Raising intake by 5 or 10% caused only small and not statistically significant increases in post partum weight.

5. Neither changes in food intake nor in environment affected lamb birth weights.

6. Ewes fed to appetite had a significantly greater wool production than those at the maintenance level. Environment had no effect on the weight of clean wool produced but penning indoors increased the weight of suint.

The behaviour of six pure red deer and six hybrid 3/4 red deer × 1/4 Pere David's deer calves born to pure red deer hinds, was observed from 1 to 24 days of age. Young calves (1 to 8 days of age) spent most time hiding, with neither genotype regularly observed in open view (red deer 11 (s.e. 2·0) % and hybrids 14 (s.e. 2·0) %). However, between 9 and 16 days the hybrid calves were in open view more than twice as often as the red deer calves (38 (s.e. 3·2) % v. 18 (s.e. 2·6) %, respectively; P < 0·01). Both genotypes spent over half (both 54 (s.e. 3·5) %) of their time in open view from 17 to 24 days of age. As they grew older, the hybrid calves also spent significantly less time prone and more time standing, compared with the red deer calves.

These results indicate that the behaviour of the hybrids, is somewhat precocious compared with pure red deer calves, and furthermore provide evidence that a component of neonatal behaviour in deer may be inherited.

Twenty-eight inbred (I, inbreeding coefficient 0-375 and 0-5) and 28 matching outbred (O) sheep, aged 26 weeks, were housed and allocated in equal number to two planes of nutrition, a high plane (H), involving ad libitum feeding on a pelleted diet, the other a low plane (L), restricted to an amount of the same diet which would maintain live weight. Food consumption, live weight, linear body dimensions and wool growth were recorded for 19 weeks, and for 4 weeks later in the experiment when L as well H animals received ad libitum feeding. Observations were also made for a final 9 weeks when the sheep were at grass.

The I sheep were substantially smaller in weight and body dimensions than the O sheep throughout the experiment. On ad libitum feeding, the I and O lambs grew in parallel and by the same amount per unit of food consumed. There was also no difference between I and O sheep in the amount of food per kg metabolic live weight (M0·73) required to maintain the live weight of the sheep on the restricted intake. The two types of sheep were therefore similar in efficiency.

During the 4-week period when L sheep were fed ad libitum they showed some compensatory growth relative to the H group, but I and O groups behaved similarly. At grass, a tendency for slightly faster growth continued for the O group formerly on a low plane, but there were no significant interactions between plane of nutrition (as originally allocated) and inbreeding.

Wool growth mirrored the results on body growth, with substantial effects of plane of nutrition, but wool growth per unit area of skin did not differ between I and O groups.

Seven daily doses of 60 or 120 mg cortisol administered to mature sheep given a maintenance ration depressed wool fibre diameter by approximately 10%. Similar treatment with 120 mg cortisol for 14 days produced a more severe and prolonged effect, though fibre diameter was unaffected by a series of seven injections of 40 IU ACTH given every second day.

Fourteen days at 10% of maintenance and 14 days' cortisol treatment were applied to mature sheep fed either continually at 150% maintenance, or at 75% followed by 150% maintenance. Cortisol treatment was associated with a significant reduction in fibre diameter only in the animals fed at 150% maintenance. Restriction to 10% maintenance for 14 days had no such effect. Approximately 20% of fibres were shed following cortisol treatment in both nutritional groups, but a marked ‘break’ in the fleece occurred only in the 75% maintenance group.

A low plane of nutrition is confirmed as a major factor predisposing to ‘tenderness’ and ‘break’, and short-term adrenocortical stimulation is shown to be sufficient to produce the reduction in fibre diameter and increased fibre shedding associated with these faults. However, semi-starvation (represented by restriction to 10% of maintenance) appears to have played a relatively minor role in their development.