Myogenesis is facilitated by four myogenic regulatory factors and is significantly inhibited by myostatin. The objective of the current study was to examine embryonic gene regulation of myostatin/myogenic regulatory factors, and subsequent manipulations of protein synthesis, in broiler embryos under induced hyperammonemia. Broiler eggs were injected with ammonium acetate solution four times over 48 h beginning on either embryonic day (ED) 15 or 17. Serum ammonia concentration was significantly higher (P<0.05) in ammonium acetate injected embryos for both ED17 and ED19 collected samples when compared with sham-injected controls. Expression of mRNA, extracted from pectoralis major of experimental and control embryos, was measured using real-time quantitative PCR for myostatin, myogenic regulatory factors myogenic factor 5, myogenic determination factor 1, myogenin, myogenic regulatory factor 4 and paired box 7. A significantly lower (P<0.01) myostatin expression was accompanied by a higher serum ammonia concentration in both ED17 and ED19 collected samples. Myogenic factor 5 expression was higher (P<0.05) in ED17 collected samples administered ammonium acetate. In both ED17 and ED19 collected samples, myogenic regulatory factor 4 was lower (P⩽0.05) in ammonium acetate injected embryos. No significant difference was seen in myogenic determination factor 1, myogenin or paired box 7 expression between treatment groups for either age of sample collection. In addition, there was no significant difference in BrdU staining of histological samples taken from treated and control embryos. Myostatin protein levels were evaluated by Western blot analysis, and also showed lower myostatin expression (P<0.05). Overall, it appears possible to inhibit myostatin expression through hyperammonemia, which is expected to have a positive effect on embryonic myogenesis and postnatal muscle growth.

Ninety-six lamb carcasses drawn from six batches of lambs commercially consigned to an abattoir were analysed for characteristics which may affect their economic value. From each batch carcasses were selected in equal numbers into two classes of ‘good’ or ‘poor’ conformation according to traditional standards. Carcasses selected for ‘good’ conformation were heavier (P<0·05) and fatter (P<0·05), slightly shorter in carcass length and hind leg length (P<0·05), greater in circumference (P<0·001) and width (P<0·001) of the hind leg, slightly greater in muscle weight (P<0·05) but no greater in bone weight than those of poor conformation. The yield of prime retail joints was similar in the two conformation classes but the ‘good’ conformation class had a higher proportion of loin and rib joints and lower proportion of hind leg joint (P < 0·01) although these differences were not considered to be of commercial importance. There was a lower proportion of the carcass fatty tissue in the hind leg joint of the ‘good’ conformation class (P < 0·05). Muscle-to-bone ratio and area of ‘eye muscle’ (M. longissimus thoracis) appeared to be little affected by selecting for conformation differences. Depth of fleshing as indicated by the weight of muscle in the hind leg per 10 cm length, was 40 g (6%) heavier in the carcasses of the ‘good’ conformation class. This contrasted with the much greater differences, between batches, of 290 g (40 to 50%). Between batches there were significant differences for all the measures taken except the yield of preferred retail cuts. In the main the batch differences were greater and commercially more important than the conformation class differences.

Sixteen pork carcasses were purchased from those exhibited in Class 146 at the Royal Smithfield Show 1978 (i.e. pork carcasses of 48 to 61kg dead weight, age <5 months). Eight had thinner backfat than the average for the class (‘very lean’ group with 6 mm fat over m. longissimus at the last rib and estimated lean content in side of 63%), while eight had thicker backfat than the average (‘lean’ group with 12 mm fat over m. longissimus at the last rib and estimated lean content in side of 57%). Both groups were leaner than the national average. The carcasses were returned to the Meat Research Institute for eating quality assessments. Muscle quality was similar in both groups. Toughness (assessed instrumentally), tenderness and flavour (assessed by taste panellists) were also similar. Juiciness was lower in the ‘very lean’ group but was not matched by higher cooking losses and the difference was considered to be relatively unimportant. In conclusion, the eating quality of pork is maintained at very low values of carcass fatness.

Two experiments examined the effects of including sodium bicarbonate in the diet of dairy cows in early lactation for two different feeding systems. In experiment 1, 28 Friesian cows were allocated to two groups according to parity, calving date and their milk yield in days 5 to 14. Cows were given either a standard home-mixed concentrate or a similar concentrate with sodium bicarbonate included at 25 kg/t. Concentrates were given to individual cows twice daily at a flat rate determined by their 5- to 14-day yield, and hay was group-fed to appetite. Milk yield in days 15 to 100 post-calving did not differ significantly between treatments, but cows given concentrate containing bicarbonate ate more hay and had a higher milk fat concentration (36·0 v. 32·5 g/kg, P < 0·01). In experiment 2, 80 cows were allocated to two treatments according to parity, calving date and previous lactation yield. There were two replicates of each treatment. All groups were given silage and concentrates as a complete diet for 8 weeks from calving, and 20 g sodium bicarbonate per kg total dry matter was included in the diet of half the animals. Cows given the diet containing bicarbonate had higher food intakes (14·9 v. 13·9 kg dry matter per head per day) and lower live-weight losses (13 v. 44 kg, P < 0·001). Milk yield and milk quality did not differ between treatments. Conception tended to be better in cows given the bicarbonate diet.

In two cattle head deboning plants, a total of 8879 cattle skulls were investigated for number and precision of shots. Deviation from the ideal position on the forehead and the direction of the shot were measured, results were then attributed to three classes of precision. In all, 64.7% of the skulls in plant 1 and 65.3% in plant 2 were shot from the ideal position and in the ideal direction. A medium precision was observed in 31.3% and 31.5% of cases, 4.0% and 3.1%, respectively, of the skulls indicated a poor precision. In both plants, skulls with more than one shot hole were observed. Shot holes may indicate the precision of a shot, and thus the risk of suffering during the sensitive time of stunning. In addition to observations at the time of stunning, the observation of shot holes on skulls at random or in total after a day's slaughter can reflect the shooting precision.

The effect of long-term treatment of goats with methylthiouracil on the timing, amount and quality of secondary fibre (cashmere) growth and timing of cashmere moult in goats was investigated. From early June, groups of 10 Icelandic × Scottish feral goats were dosed orally each day, for a 15-month period, with 5 mg methylthiouracil per kg live weight in 30 ml water (treated; T) or with water only (control; C). Treatment with methylthiouracil resulted in a significant reduction (P < 0·05) in the proportion of active secondary hair follicles present during March. This was associated with a delayed onset of moult of cashmere in T compared with C goats at both the head (11 March v. 23 February; s.e. 3·33 days; P< 0·05) and mid side (27 March v. 26 February; s.e. 3·58 days; P < 0·001). There was no effect on the time of onset (C, 19 July; T, 19 July; s.e. 5·84 days) or cessation of cashmere fibre growth (C, 9 December; T, 8 December; s.e. 1·69 days) or the mean growth rate (C, 0·473 mm/day; T, 0·451 mm/day; s.e. 0·025) and fibre diameter (C, 16·9 μm; T, 15·4 jim; s.e. 0·266). Wlien present in the fleece, the mean weight and proportion of cashmere was higher in C than in T goats (P < 0·05). It is concluded that methylthiouracil treatment altered secondary follicle activity and the time of onset of the moult of cashmere and that these changes may be a result of reduced triiodothyronine production from thyroxine and associated secondary changes in profiles of insulin and IGF-1.

This study aimed at investigating risk factors for new intramammary infections (IMI) during the dry period in untreated cows from herds using selective dry cow antibiotic therapy (DCT). A total of 980 uninfected quarters in 347 untreated cows from 28 herds using selective DCT were included in a prospective survey. A herd-level questionnaire and an individual cow-level recording sheet were implemented to collect data on putative risk factors. Quarter milk samples were taken at drying-off and on day 3 after calving to assess the occurrence of new IMI during the dry period. A multivariate model including a herd effect as random and a cow effect as repeated was run at the quarter level. Interactions between risk factors and the cow infection status at drying-off (cow infected in at least one quarter v. uninfected) were checked. Three risk factors were found significantly associated with the risk for new IMI without interaction (P < 0.05): cows infected in at least one quarter at drying-off (v. uninfected cows) (relative risks (RR) = 1.58); long preceding lactation (>355 days v. shorter length) (RR = 1.62); long dry period (>65 days v. shorter length) (RR = 1.46). One risk factor acted only in interaction with the cow infection status at drying-off: in cows uninfected at drying-off, the risk for new IMI was significantly higher in cows with short teats (RR = 1.21) when compared with cows with long or normal teats, while the reverse relationship was observed in cows infected at drying-off. Risk factors can be translated in recommendations, for instance to have dry periods not longer than 2 months. Moreover, as suggested by our results, the efficacy of selective DCT towards the prevention of new IMI would be improved if all infected cows were detected and treated. Criteria to accurately identify these infected cows should be therefore further investigated.

Effects on cow reproductive performance, of cow age, parous state, body weight and body-weight change over the breeding season were examined using 6490 annual records from indigenous cows in Botswana.

Calving percentage rose from 69% at 2·5 yr of age to a maximum of 82% at 6 to 7 yr and declined in cows over 8 yr of age. Heifers and previously non-parous cows had a calving percentage of 85%; 8, 18 and 30% higher respectively than parous cows that had calved at the beginning, middle and end of the previous calving season. Cows weighing less than 300 kg at the beginning of the mating season achieved a 50% calving. This rose steadily to 85% as body weight increased to 430 kg.

Cows that lost weight over the mating period achieved a 67% calving, while gains of 20 kg raised this to 76%. Increased weight gains thereafter had little effect on calving percentage. In all cases, as percentages increased, days to conception decreased in a similar manner.

Under these range conditions in Botswana, animals least likely to achieve high calving percentages were young cows; cows which calved previously at the end or middle of the calving season; cows less than 310 kg in weight; and cows gaining less than 20 kg body weight during the mating season.

Two experiments were conducted using British Friesian bull calves to determine the effects on growth, food intake and rumen volume of including 0, 150, 200 or 250 g ammonia-treated (35 g/kg dry matter (DM)) or untreated barley straw per kg pelleted concentrate based on cereal. All calves received once daily 440 g milk replacer powder reconstituted in 3 1 warm water, were weaned at 56 days of age and given one of the seven pelleted diets to appetite from 14 days of age. In experiment 1, the seven diets were allocated at random to 70 calves. Food intake was increased by the inclusion of straw but there was no effect on intake of the increased concentration of straw; daily DM intake from 14 to 77 days of age was 1·36 and 1·77 kg/day respectively for diets with or without straw. From 14 to 56 days of age intake of concentrate was increased by the addition of straw but was negatively correlated with the concentration of straw in the diet. After weaning inclusion of straw, whilst increasing total intake, tended to depress intake of cereal. Treatment with ammonia increased the nitrogen concentration in the straw but had no effect on the digestibility or amount of diet consumed. After adjustment was made for gut fill, the increases in weight between 4 and 84 days of age of calves given 150, 200 or 250 g straw per kg food were 6·6, 1·2 and 1·0 kg respectively greater than those that occurred when there was no straw in the diet. DM digestibility of all diets was above 0·67 but the mean digestibility of acid detergent fibre was low (0·19). The pH and ammonia concentration of rumen liquor were low and below the optimum for cellulose digestion. In experiment 2, rumen volume was measured in vivo in a group of 24 calves given the same diets as in experiment 1. Rumen volume was increased two fold at 42 days of age by the addition of straw to the diet (5·6 v. 2·6 1, P < 0·001), by 87 days of age the difference was increased to 7·11, (19·0 v. 11·9 1, P < 0·01). When all calves were given the same diet from 91 days of age, there was no effect of previous treatment on intake or rumen volume at 147 days of age.

Understanding what determines feeding behaviour in herbivores is essential to optimise the use of forages in breeding systems. Herbivores can evaluate foods by associative learning of their pre-ingestive characteristics (taste, odour, etc.) and their post-ingestive consequences. Post-ingestive consequences are acknowledged as influencing intake and food choices, but the role of pre-ingestive characteristics is still being debated. Our experiment was designed to test their separate effects on daily dry matter intake (DMI), intake patterns and short-term choices in sheep by crossing the nature of the hay orally consumed (o) ad libitum, lucerne (L) or grass (G), with the nature of the hay introduced into the rumen (r), L or G, at a rate of half the total amount of hay received the day before. We applied four treatments, Go/Gr, Go/Lr, Lo/Gr and Lo/Lr, to test the effects of (i) post-ingestive consequences with similar pre-ingestive characteristics (Go/Gr v. Go/Lr; Lo/Gr v. Lo/Lr) and (ii) pre-ingestive characteristics with similar post-ingestive consequences at the end of the feeding period (Go/Lr v. Lo/Gr). Six rumen-fistulated sheep underwent all the treatments over 11-day periods in a latin square design. Eating time was restricted to 6 h/day, intraruminal introductions were performed just before food offer and choice tests were conducted after food removal. For similar pre-ingestive characteristics, DMI increased when L hay was introduced into the rumen rather than G (P < 0.05), possibly owing to a lower fill effect of L due to its lower NDF content and higher rumen degradability. The increased DMI resulted from longer eating time when G was orally consumed (149 v. 192 min, P < 0.05), whereas it resulted from higher intake rate with L (4.8 v. 6.1 g/min, P < 0.05). For similar post-ingestive consequences at the end of the feeding period (Go/Lr and Lo/Gr), DMI were similar (P > 0.05). Pre-ingestive characteristics or palatability per se did not therefore influence daily intake, although they influenced eating patterns. Pre-ingestive characteristics also greatly influenced short-term choices in favour of the hay that was not previously consumed, independently of any post-ingestive influence. This study confirms the effects of post-ingestive consequences on daily intake, but demonstrates that these variations are obtained by different behavioural adjustments under the influence of pre-ingestive characteristics. Preference for novelty, regardless of post-ingestive consequences, thus suggests that sheep may seek a diverse diet more for pleasure than for functional purposes, with implications for animal welfare.

The aim of this study was to assess the effect of carvacrol supplement as a dietary additive to rumen fermentors, fed a barley seed:alfalfa hay (70:30) ration and to compare its effect with monensin supplementation. The material was incubated with goat ruminal fluid and four different treatments were included: no additive (C), 7.5 mg/l monensin (M), 250 mg/l carvacrol (C250) and 500 mg/l carvacrol (C500). The addition of carvacrol reduced in vitro dry matter (DM), crude protein (CP) and neutral-detergent fibre (NDF) digestion. The effects induced by C250 on DM digestion at 72 h of incubation were comparable with those of M, whereas a greater reduction was obtained when carvacrol was supplemented at 500 mg/l concentration (68.9, 68.5 and 53.0 v. 76.1% for M, C250 and C500 v. C, respectively). The reduced CP potential degradability by supplements (51.2, 53.9 and 51.5 v. 72.8% for M, C250 and C500 v. C, respectively) was mainly caused by a reduction of the slowly degradable fraction. Volatile fatty acid (VFA) profiles determined after 48 h of incubation showed C250 increased butyrate and decreased acetate proportions, whereas M mainly stimulated propionate proportions, suggesting that the mechanism of action of carvacrol and M differs. C500 significantly reduced total VFA production. Carvacrol could be of great interest for its usage as a potential modulator of ruminal fermentation. Future research, including in vivo studies, in order to understand the factors that contribute to its antimicrobial activity and the selection of the optimal dose is required.

A flock of 117, 10-month-old Egyptian geese consisting of 90 females and 27 males were utilized in this investigation. Birds were randomly divided into three equal groups, each made up of three replicates of 10 females and 3 males each. The first group was kept under a pasture system (PS) and allowed to swim in water ducts during the daytime (PS) and kept inside the house during the night. The second group of birds were kept in confinement in a house and fed ad libitum on a commercial feed (intensive system (IS)). Birds in the third group (semi-intensive system (SIS)) were released from the house for 6 h a day and given access to the pasture and water ducts. Each group was housed in three pens (replicates) in the SIS. They were given ad libitum access to the commercial feed when in the house. Each pen measured (2 × 3 m2). Natural mating was practiced during the period from November to the end of May. BW of geese under ISS was significantly (P ⩽ 0.05) higher than those under PS and SIS. Egg number, weight and mass of geese in the SIS system were significantly (P ⩽ 0.05) greater than those of geese in the PS and IS systems. Fertility and hatchability percentages were significantly (P ⩽ 0.05) greater in the PS (84.2% and 88.6%) than in the IS (77.5% and 82.8%) and SIS systems (80.7% and 85.5%). Shell weight and thickness were significantly (P ⩽ 0.05) better in the IS and SIS systems than in the PS system. Geese in the PS and SIS systems exhibited significantly higher plasma estradiol-17 and progesterone than those in the IS. Testosterone was significantly higher in IS than in the other systems. Semen quality factor was significantly higher in the PS and SIS systems than in the IS system. Carcass weight was significantly greater in IS and SIS geese than in PS geese, but the PS system resulted in a decreased percentage skin, abdominal fat and liver. Total amount of meat produced per geese was significantly greater in the SIS than in the IS system and greater in the IS than in the PS system.

Dietary protein restriction is one of the effective ways to reduce post-weaning diarrhoea and intestinal fermentation in piglets, but it may also reduce growth performance. The compensatory growth induced by subsequent protein realimentation may solve the issue. However, little research has been done on the impact of protein realimentation on the gut. In this study, the effects of protein restriction and realimentation on ileal morphology, ileal microbial composition and metabolites in weaned piglets were investigated. Thirty-six 28-day-old weaned piglets with an average body weight of 6.47 ± 0.04 kg were randomly divided into a control group and a treatment group. The CP level in the diet of the control group was 18.83% for the entire experimental period. The piglets in the treatment group were fed 13.05% CP between days 0 and 14 and restored to a diet of 18.83% CP for days 14 to 28. On day 14 and 28, six pigs from each group were sacrificed and sampled. It was found that the abundance of Lactobacillus and Salmonella in the ileal digesta was significantly lower in the treatment group than the control group on day 14, whereas the abundance of Clostridium sensu stricto 1, Streptococcus, Halomonas and Pseudomonas significantly increased in the ileal digesta of the treatment group on day 14 compared with the control group. In addition, reduced concentrations of lactic acid, total short-chain fatty acids (total SCFAs), total branched chain fatty acids, ammonia and impaired ileal morphology and mucosal barrier were observed in the treatment group on day 14. However, diarrhoea levels decreased in the treatment group throughout the experiment. During the succedent protein realimentation stage, the treatment group demonstrated compensatory growth. Compared with the control group, the treatment group showed increased abundance of Lactobacillus and reduced abundance of Salmonella, Halomonas and Pseudomonas in the ileum on day 28. The concentrations of lactic acid and total SCFAs increased significantly, whereas the concentration of ammonia remained at a lower level in the treatment group on day 28 compared with the control group. Overall, protein realimentation could improve ileal morphology and barrier functions and promote ileal digestive and absorptive functions. In conclusion, ileal microbial composition and metabolites could change according to dietary protein restriction and realimentation and eventually influence ileal morphology and barrier functions.

Dietary supplementation with the organic chromium (Cr) has been shown to positively affect the immune function of poultry. However, to our knowledge, no experiment has been done to directly compare the impacts of Cr chloride and chromium picolinate (CrPic) on the immune responses of broilers vaccinated with Avian Influenza (AI) virus vaccine. Therefore, the present experiment was conducted to investigate the effects of supplemental Cr sources (Cr chloride and CrPic) and levels on the growth performance and immune responses of broilers vaccinated with AI virus vaccine so as to provide an effective nutritional strategy for improving immune function of broilers. A total of 432 1-day (d)-old male broiler chicks were used in a 1 plus 2×4 design. Chickens were given either a diet without Cr supplementation (control) or diets supplemented with 0.4, 0.8, 1.6, or 3.2 mg Cr/kg as either Cr chloride or CrPic for 42 d. Compared to the control, dietary Cr supplementation had no effect (P>0.05) on average daily gain, average daily feed intake and gain : feed of broilers during the starter and grower phases, but increased (P<0.05) the relative weights of bursa of fabricius on d 21 and thymus, spleen, or bursa of fabricius on d 42, serum antibody titers against AI virus on d 21, 28, 35 and 42, blood T-lymphocyte transformation rate on d 28 and 42, blood T-lymphocyte percentage on d 42, and serum interleukin-2 contents on d 28. Broilers fed the diets supplemented with the inorganic Cr chloride had higher (P<0.05) weights of thymus, spleen and bursa of fabricius than those fed the diets supplemented with the CrPic on d 42. In addition, broilers fed the diets supplemented with the CrPic had higher (P<0.05) antibody titers against AI virus than those fed the diets supplemented with the inorganic Cr chloride on d 21 and 35. These results indicate that dietary Cr supplementation improved immune responses of broilers vaccinated with AI virus, and the inorganic Cr chloride was more effective than the CrPic in increasing the relative weights of lymphoid organs, however, the CrPic was more effective than the inorganic Cr chloride in enhancing the serum antibody titer against AI virus.

Mastitis is a costly disease and in many areas of the world, these costs have been quantified to support farmers in their decision making with regard to prevention of mastitis. Although for subsaharan circumstances estimates have been made for the costs of subclinical mastitis (SCM), farm-specific cost estimations comprising both clinical mastitis (CM) and SCM are lacking. In this paper, we quantified failure costs of both CM and SCM on 150 Ethiopian market-oriented dairy farms keeping Holstein Friesian × Zebu breed cows. Data about CM were collected by face-to-face interviews and the prevalence of SCM was estimated for each farm using the California mastitis test. All other relevant information needed to calculate the failure costs, such as the consequences of mastitis and price levels, was collected during the farm visits, except for the parameter for milk production losses due to SCM, which was based on literature estimates and subjected to sensitivity analyses. The average total failure costs of mastitis was estimated to be 4 765 Ethiopian Birr (ETB) (1 ETB = 0.0449 USD) per farm per year of which SCM contributed 54% of the costs. The average total failure costs per lactating cow per farm per year were 1 961 ETB, with a large variation between farms (range 0 to 35 084 ETB). This large variation in failure costs between farms was mainly driven by variation in incidence of CM and prevalence of SCM. Milk production losses made the largest contribution (80%), whereas culling contributed 13% to 17% to the total failure costs. In our estimates, costs of veterinary services, drugs, discarded milk and labour made a minor contribution to the total failure costs of mastitis. Relative to the income of dairy farmers in North Western Ethiopia; the total failure costs of mastitis are high. In general, Ethiopian farmers are aware of the negative consequences of CM, but creating awareness of the high costs of SCM and showing large variation between farmers may be instrumental in motivating farmers to also take preventive measures for SCM.

A study has been made of the performance of crosses and backcrosses of Bos taurus and Bos indicus cattle using records covering a period of 15 years from the Experimental Station, Tanga. The gene combinations found in ½-bred animals were the most productive in this environment, and ¼-bred Bos taurus animals gave higher average daily yields of milk between calvings than those with ¾ taurus blood.

An experiment was conducted on 13 commercial barley beef units in Scotland, using a total of 301 early-weaned Friesian male calves. On each unit the trial batch of calves was divided into two groups, which were then allocated to a control diet (85% barley + 15% protein supplement) or the same diet supplemented with 20 mg. chlortetracycline per kg. of feed. The experiment was conducted over the live-weight range 115 to 360 kg.

The chlortetracycline significantly (P<0·01) improved live-weight gain ( + 4·9%) and feed utilisation ( + 4·8%). This overall effect was largely due to a high response during the first 12 weeks. From 13 to 28 weeks the chlortetracycline had only a marginal effect, which was not significant. There was no significant difference in the feed intakes of the two groups. There was a significant (P<0·01) negative correlation between the effect of the chlortetracycline on live-weight gain at each unit and the growth rate of the control animals at that unit; the response was greatest on farms with poor hygiene. The animals given chlortetracycline showed a significantly (P<0·05) lower incidence of liver abscesses (11·8%) than the controls (28·2%). Macroscopic examination of the rumens showed that rumenitis is common among intensively fed cattle, but no correlation could be found between incidence of liver abscesses and rumen lesions.

The aim of this study was to estimate genetic parameters for feed intake recorded as farmers’ perception of young sows’ appetite for the first 3 weeks of lactation (APP) and feed intake recorded for one day in the 3rd week of lactation (FEED), litter weight (LW) at 3 weeks, sow body condition at weaning (BC) and the following five reproduction traits: weaning-to-service interval of 1 to 7 days (WSI7), weaning-to-service interval of 1 to 50 days (WSI50), delayed service or not (DELAYED), pregnant on first service or not (PREGNANT) and litter size in 2nd parity (NBT2). The analyses included data on 4606 Norwegian Landrace 1st-parity sows and their litters. The Gibbs sampling method was used. The traits DELAYED and PREGNANT were analysed as threshold traits and APP, FEED, LW, BC, WSI7, WSI50 and NBT2 were analysed as linear traits. The heritability estimates for APP and FEED were low (<0.1), whereas the estimates for DELAYED and PREGNANT were rather high (0.4 and 0.3). The heritability estimate for BC was 0.2. The genetic correlations confirmed the complexity of breeding for sow performance; selection for heavy 1st litters may lead to lower body condition at weaning, which in turn leads to lower reproductive performance and smaller litters in 2nd parity. Selection for higher sow feed intake would improve body condition, but the simple way of measuring feed intake tested in this study (APP and FEED) cannot be recommended because of the low heritability obtained for these traits.

A flock of Polled Dorset Horn ewes joined with three Polled Dorset Horn rams were observed during the hours of daylight, for 17 days, when all the ewes were known to be showing oestrus regularly. The number of approaches, mounts and serves made by the rams and the identities of the ewes involved were recorded.

The mean and SE for the number of services per ewe in oestrus was 4·2 ± 0·3. There were no significant differences in sexual performance between the rams apart from the number of mounts and the mount to service ratio. The number of ewes served per ram and the number of services per ewe in oestrus declined significantly over the 17-day period. Ram performance was significantly related to the number of ewes in oestrus and to the time that the rams had been joined with the same group of stimulative animals (e.g. multiple regression of number of services x with time y and number of ewes in oestrus z is: x = −0·72y + 1·3z + 8·8).

The rôle of various classes of nutrients (energy substrates, vitamins, minerals, amino acids) in the production of wool and hair from follicles, is considered for a variety of animal species. The wool and hair follicle have evolved a number of interesting features of carbohydrate metabolism including glutaminolysis, aerobic glycolysis, significant activity of the pentose phosphate pathway, and storage and mobilisation of glycogen. Presumably the necessity to continue to produce fibre despite fluctuations in the supply of oxygen and nutrients has resulted in some of these unique features, while others reflect the high level of DNA and protein synthesis occurring in the follicle. While it is considered that energy does not normally limit fibre growth, the relative contributions of aerobic and anerobic metabolism will greatly influence the amount of ATP available for follicle activity, such that energy availability may at times alter fibre growth. Alopecia and deficient fibre growth are consistent outcomes of deficiencies of biotin, riboflavin, pyridoxine, folate and pantothenic acid, but the precise rôles of these vitamins in follicle function await elucidation. Folate, in particular appears to play an important rôle in wool production, presumably reflecting its involvement in methionine metabolism. Cholecalciferol (vitamin D) significantly alters fibre growth in cultured follicles; vitamin D receptors are located in the outer root sheath, bulb, and dermal papilla of the follicle; and alopecia occurs in humans with defects in the vitamin D receptor. Retinol (vitamin A), too, appears to influence follicle function by altering keratinocyte proliferation and differentiation, with direct effects on the expression of keratin genes. The receptors for the retinoids are present in the keratogenous zone, the outer root sheath, the bulb, and the sebaceous glands. Vitamin A may also act indirectly on follicle function by influencing the activity of the insulin-like and epidermal growth factors and by altering vitamin D activity. At present there is little evidence implicating alpha-tocopherol (vitamin E) or phytylmenaquinone (vitamin K) in follicular events. Of the minerals, only copper and zinc have been shown to have direct effects on follicle function, independent of effects on food intake. Copper has direct effects on the activity of an unidentified enzyme on oxidation of thiol groups to form disulphide linkages. Wool produced by copper-deficient sheep lacks crimp, is weak and lustrous. Copper is also necessary for the activity of tyrosinase and the tyrosinase-related proteins involved in melanin synthesis. Zinc, like copper, is required for the normal keratinization of fibres but again, the precise rôle has yet to be elucidated. While the importance of amino acid supply for wool growth has long been established, there are still some unaswered questions such as; what are the effects of amino acids on fibre growth in animals other than sheep; what are the characteristics of the amino acid transport genes and proteins operating in the wool and hair follicle; and what are the specific rôles for amino acids in follicle function.