An investigation was conducted into the effects of increasing plasma prolactin concentration with long photoperiod or suppressing it with bromocryptine on the fertility of ewe lambs. One hundred and twenty dim Forest ewe lambs were divided into three groups: group C was kept as a control; group L was exposed to a long photoperiod (16 h light: 8 h dark) and group B was given daily injections of 1 mg bromocryptine from 12 days before until 21 days after mating. All three groups were mated in late November, 30 days after housing, following progestagen/PMSG treatment. Post-mating prolactin concentrations were significantly higher in group L and lower in group B compared with group C (P > 0·05). There was a tendency for pregnancy rate and the number of corpora lutea to be represented by viable foetuses to be lower in group L than in group C (P < 0·05). Furthermore, post-mating progesterone concentration was higher in this group compared with those in group C (P > 0·05). In a second experiment, 100 Welsh Χ Texel ewe lambs were given treatment C or L. Embryo survival tended to be lower and crown rump length, embryo weight and amniotic sac width were reduced at 25 days post mating in the animals given treatment L, compared with those given treatment C (P < 0·05). The combined results of the experiments indicated that fewer corpora lutea were represented by viable embryos or foetuses in group L than in group C (P < 0·05). These results suggest that embryo growth and survival is reduced in animals bred under a long photoperiod.

An experiment using twenty-five bulls aged between 1 and 1·5 years and weighing 117 to 209 kg was carried out to estimate voluntary dry-matter intake (DMI), digestible dry-matter intake (DDMI), dry-matter apparent digestibility (DMD) and growth rate when the bulls were given 18 foods available from smallholder dairy farms on the slopes of Mount Kilimanjaro, Tanzania. The animals were randomly allocated to five groups of five animals each. Foods were then randomly allocated to the five groups for four periods of 60 days each during which DMI was measured. A digestion trial was made at the completion of each measurement. Outflow rates of solids from the rumen were determined by giving the animals 200 g Cr-mordanted fibre of each food and grab faecal samples were obtained. Dry matter (DM) degradation characteristics of the foods were determined in sacco in the rumen of three Boran steers fed on guatemala grass and the water soluble fraction (A) was measured. DMI varied from 2·2 kg for banana pseudostem to 4·77 kg/day for urea-treated maize stover. DMD ranged from 549 for untreated maize stover to 767 g/kg DM for banana pseudostem and growth rate ranged from 72 for banana leaves to 275 glday for urea-treated maize stover. Potential degradability (defined by A + B) (where B is the insoluble fraction degradable with time) for the DM ranged from 617 g for banana leaves to 874 g/kg DM for banana pseudostem and the degradation rate (c) ranged from 0·0168 for banana leaves to 0·0440 per h for green maize stover. The separate use of degradation characteristics A, B and c in multiple regression to predict DMI, DDMI, and growth rates gave better results than when A + B or (A + B) + c were used. Multiple correlation coefficients between degradation characteristics and DMI, DDMI and group rate were r– 0·90, 0·93 and 0·93 respectively. The results indicate that DMI, DDMI and growth rates by cattle fed on crop residues and forages could be predicted well using the rumen degradation characteristics of the foods.

Adipocyte dimensions of subcutaneous fat, sampled by biopsy at the 13th rib, were measured in 20-week-old rams from lines of Texel-Oxford and Scottish Blackface sheep, both divergently selected for carcass lean content. A total of 163 animals were measured, with close to equal numbers per breed-line combination. In both breeds, the high (lean) selection line had significantly lower backfat depths (0·71 mm in the Texel-Oxford and 0·83 mm in the Scottish Blackface, s.e.d. = 0·14 and 0·13 mm, respectively), but body weight did not differ between the lines. The ultrasonic fat depth differences between the Texel-Oxford selected lines were accompanied by increases in adipocyte diameter, area, diameter standard deviation within each sample and implied cell number, calculated as the ratio of ultrasonic fat depth to average adipocyte diameter. In the Scottish Blackface sheep there were no selection line differences in adipocyte dimensions, but there was an increase in implied cell number in the line selected for increased fatness. Across breeds, ultrasonic fat depth was correlated with both adipocyte diameter and implied adipocyte number (r = 0·58 and 0·75, respectively), but these latter two measurements were uncorrelated with each other.

Ardacin is an antibacterial glycopeptide with ruminal activity. The objective of this study was to measure its effects on food intake and growth rate of growing and finishing steers. Two experiments were carried out simultaneously using the same foods and the same ardacin supplementation levels. In experiment 1, 72 growing steers (8 months old and 240 kg initial weight) in four treatment groups were individually offered a basal diet of grass silage ad libitum. In experiment 2, 44 finishing steers (19 months old and 463 kg initial weight), also in four treatment groups were individually offered a basal diet of grass silage ad libitum plus 3 kg (5 kg for the final 28 days) concentrates per head daily. The four treatments were 0, 50, 125 and 210 mg ardacin per head daily incorporated into 1 kg ground barley. This was offered in addition to the basal diet. The duration of the experimental period was 154 days after which 48 of the growing steers were put to pasture for a 196-day grazing season. The finishing steers were slaughtered following a withdrawal period of 7 days. Mean daily silage dry-matter intakes, and mean daily total metabolizable energy intakes for the treatments as listed above were 4·91, 5·15, 5·10 and 5·03 (s.e. 0·083) kg and 63, 66, 65 and 65 (s.e. 0·7) MJ (experiment 1), and 5·63, 5·62, 5·51 and 5·54 (s.e. 0·059) kg and 108, 108, 107 and 107 (s.e. 0·4) MJ (experiment 2), respectively. In the same order, mean daily live-weight gains during the treatment period were 612, 758, 784 and 798 (s.e. 25·2) g (experiment 1) and 911, 942, 851 and 860 (s.e. 40·0) g (experiment 2). In the growing steers proportionately 0·64 of the weight response to ardacin was retained to the end of the following grazing season. It is concluded that ardacin supplementation increased live-weight gain and improved the efficiency of conversion of food to live weight in growing steers but had no significant effect on finishing steers in this study.

Over 3 years, a flock of Scottish Blackface ewes was managed so that one-third of the ewes received a high level of nutrition during the last 100 days of pregnancy (P), one-third received a high level of nutrition during the first 100 days of lactation (L) and one-third received a low level of nutrition as derived from a hill grazing over the same two periods (C). From these ewes, 496 ewe lambs were retained at weaning (19 to 22 weeks of age), balanced for treatment, year and birth type. At 6 months of age half of the lambs, similarly balanced, were transferred to an upland grazing system (U) for three breeding years. The other half was retained on the same hill grazing as their mothers for the same period (H). At the end of the study, all ewes were fed to reduce the range in body condition at a synchronized mating and ovulation rates were determined at slaughter.

Differences in live weight of ewes due to treatment between groups P, L and C had disappeared by 18 months. There were no pre-mating differences between treatments in live weight or body condition score except that ewes in group P had higher live weights than those in group C at condition scores greater than 2·75. There was little effect of grazing system on the differences between treatments in live weight or body condition score at 30 and 42 months but H ewes were heavier and fatter at 18 months of age. Ewe mortality was consistently less in group L than in groups P and C and on system H than on system U, although the differences were not statistically significant. Group L had fewer barren ewes than groups P and C, and barrenness was significantly greater in the U than the H system. Group C had proportionally more single than multiple births than either groups P or L.

At the end of the study there were no differences between the treatments in the proportion of ewes successfully mated at the final mating nor in their ovulation rates in relation to pre-mating body condition.

It is concluded that nutrition during either the lactation period or late pregnancy period can influence subsequent lifetime reproductive performance and that this was expressed through an effect on embryo or foetal loss since there were neither residual differences apparent in live weight or condition score nor in ovulation rate potential.

A comparison was made between two different finishing systems with Belgian Blue bulls. Two groups of bulls were grazed during an initial 140-day period and then finished indoors with concentrates. There were two stocking rates during the grazing period: a medium at six bulls per ha (MGFI) and a high at eight bulls per ha (HGFI). A third group of bulls was finished indoors on a concentrate diet during the whole finishing period (FI). The experiment was repeated over 2 years consecutively. The pasture which was grazed at the medium stocking rate was characterized by a higher sward height (P < 0·01), more refusals (P < 0·001), less Lolium perenne (P < 0·05) and more Trifolium repens (P<0·05) than that grazed at eight bulls per ha. The live-weight gain was 1·15 kg/day during the grazing period for the MGFI bulls and 1·00 kg/day when they were taken indoors. The increase in stocking rate reduced the gain at grass (1·00 kg/day, P < 0·001) and improved the gain indoors (1·24 v. 1·01 kg/day, P < 0·001). In the groups which were initially grazed when compared with the indoor system, the fattening period was longer (236·0 and 241·0 v. 186·9 days, P<0·01) and the live-weight gain lower (1·11 and 1·10 v. 1·44 kg/day, P < 0·001 for MGFI, HGFI and Fl respectively). The dressing proportion was greater also (P < 0·05), and there were higher concentrations of muscles (P < 0·05) and bones (P < 0·05) in the carcass of the bulls which were grazed initially. With these bulls, the lean meat was darker (P<0·05) and lost more water although there were no effects on the myoglobin content or on shear force. The net profit was in favour of the groups which were grazed.

Friesian steer cahes were reared over winter on a silage (S) or on a silage plus concentrate (SC) diet to provide cattle of the same live weight, but of different ages for a comparison of grazing and feeding cut herbage indoors during the summer. A further group received fish meal (SF) as a supplement in an attempt to provide cattle of the same age as the S group, but of different body composition. Although supplementation improved the daily deposition of fat and protein, it did not lead to differences in body composition at the end of the winter period. The ratio of protein to fat deposition and the efficiencies of conversion were low for all groups, but they did improve as the level of supplementation increased.

There was no carry-over effect of winter treatment on summer performance. However, housed cattle deposited significantly more fat.

The trial demonstrated the inefficient use of nitrogen from silage with poor fermentation characteristics and the predisposition of cattle on such diets to low protein to energy retention. Whilst supplementation altered this balance, higher levels than given would be needed to have a marked effect. It was also concluded that the performance of housed cattle as an indicator of that of grazing cattle, is likely to be misleading because lower activity reduces maintenance requirement and leads to greater fat deposition.

The time spent under a shelter by eight grazing fattening bulls of the Belgian Blue breed in each of 3 years consecutively for a total of 48 days was recorded using a time-lapse recorder with infrared illumination.

During one grazing period, data were collected over 35 days (experiment 1). Observations were divided into 166 h with rain (20%) and 674 h without precipitation (80%). The average occupation rates were 15·4 (s.e. 29·1) % for the hours with rain and 4·5 (s.e. 14·8) % for the hours without precipitation (P < 0·001). The effect of intensity and duration of rain on the occupation rate was significant from 0·4 l/m2 or from 2 h.

Experiment 2 (13 days of observation) examined the influence of temperature and solar radiation on the use of shelter. The occupation rates were 21 (s.e. 23) % during the daylight hours (07.00 to 19.00 h), 6 (s.e. 8) % during the night (19.00 to 07.00 h) and 14 (s.e. 14) % during a 24-h period. The occupation rate between 07.00 and 19.00 h was significantly correlated to the mean daily temperature (r = 0·75), the maximum daily temperature (r — 0·86) and the direct solar radiation time (r 0·60). When the maximum daily temperature exceeded 20°C, the use of the shelter increased from 10 to 49% of the daylight hours.

There was no significant difference between the live-weight gains of animals from the observed group and those of other bulls on an adjacent pasture without shelter. Nevertheless, these observations suggest that a shelter may improve the welfare of grazing cattle.

A study was carried out to examine the effects of method of grass conservation on intake and apparent digestibility by sheep and rate of degradation in the rumen of cattle. Thirty-six hoggets were arranged in a three-period partial change-over design involving nine treatments. The treatments consisted of fresh herbage or herbage from the same pasture which was ensiled for 2, 4, 7, 10, 20 and 41 days in round bales or herbage from the same pasture conserved as hay or ensiled in a bunker silo for 51 days. In addition the rate of dry-matter disappearance in the rumen for each treatment was determined using three rumen fistulated steers. The fresh and ensiled treatments had been frozen prior to feeding. Results from the study showed that the dry-matter intakes, corrected for losses of volatile compounds, of material ensiled in round bales, was increasingly depressed with period of ensiling up to 20 days after ensiling. Intakes of digestible energy followed a similar trend. Regression analysis indicated that reductions in intake with ensiling were mainly due to increases in ammonia N and n-butyric acid concentration, while changes in pH, water-soluble carbohydrate and acetic acid concentration also influenced intake. The differences in intakes of dry matter and digestible energy between fresh herbage and herbage from the bunker silo were not significant. The ensiling of herbage in round bales had little effect on organic matter apparent digestibility but led to an increase in nitrogen apparent digestibility and effective degradability when calculated at rumen outflow rates of 0·05 per h and 0·08 per h. Conservation of grass as hay led to a reduction in the intake, apparent digestibility and effective degradability of dry matter.

The eating quality of lambs slaughtered at weaning or 8 to 9 weeks later off pastures of diploid grass (D), tetraploid grass (T) and tetraploid grass/white clover (TC) was studied. Samples of lean from grilled chops and roasted leg joints were assessed by members of a group of 36 sensory panellists for texture by rating juiciness and tenderness on an eight-point scale. Lamb and abnormal flavour were assessed in lean and fat samples. Lean from lambs slaughtered off the mother at weaning was significantly more tender than from lambs slaughtered 8 to 9 weeks later (5·8v. 5·0, s.e.d. 0·18; P < 0·001). There was a tendency for lambs slaughtered off TC to be more juicy and tender. Lean from chops was significantly more juicy and tender and of superior flavour to lean from leg and overall acceptability was higher for chops. Acceptability of lamb slaughtered at weaning was higher than of lamb slaughtered 8 to 9 weeks later (5·3v. 4·9, s.e.d. 0·14; P < 0·001).

In further studies a trained sensory panel of 12 judges formed a consensus flavour profile for 10 attributes of lean and five attributes of fat. Univariate analysis revealed only small differences between treatments. Multivariate statistical procedures however identified significant treatment effects that appeared favourable to the flavour of lamb slaughtered off the mother although only around a third of the variation was explained.

Analysis of weight loss on cooking showed less wastage when lambs were slaughtered off the mother (0·209 v. 0·225, s.e.d. 0·0043; P < 0·001) and when grazed on grass/clover (TC)v.grass (D, T) (0·206v. 0·222, 0·223; s.e.d. 0·0053;P < 0·01). Weight loss on cooking was negatively correlated with texture and overall acceptability.

The results obtained provide evidence for enhanced eating quality from production systems involving the sale of lambs off the mother. Incorporation of grazing of clover pastures into production systems showed some small benefits.

Two groups each of six lambs of the fat-tailed Naeimi breed, well adapted to a semi-arid climate, were housed under semi-controlled temperature (43·2 to 43·8°C) with low relative humidity (<0·8). After a 1-week adaptation period, the first group (control) was injected subcutaneously with 1 ml vehicle solution of 40% ethanol in saline, twice daily at 08.00 and 17.00 hfor the 11-day experimental period. In the other group, each lamb was injected daily for 6 days with 0·18 mg/kg per day of the prolactin inhibitor, 2 bromo-a-ergocryptine (CB154) dissolved in the vehicle solution. Treatment during the next 5 days was as for the control animals. Rectal temperature (RT), respiratory rate (RR), water and food intakes were recorded before injections. Daily average data were used in the statistical analysis, except those of the 1st day of bromocryptine injection. Lambs of the control group were able to maintain their RT (39·5 (s.e. 0·04) °C) during heat exposure, but those treated with the bromocryptine could not (40·3 (s.e. 0·07) °C). However, the latter group continued to respire more rapidly (P < 0·01) after cessation of the CB154 treatment, reducing their body temperature slightly (39·9 (s.e. 0·06) °C). This shows that, following prolactin suppression, heat-stressed lambs were unable to regulate their body temperature despite their RR. Water intake did not change during bromocryptine treatment, but the ratio of water to dry-matter intake did increase due to lower food consumption. These results suggest that prolactin might have an important role in thermoregulation of the fat-tailed male sheep during elevated ambient temperature.

A study urns conducted to determine the best method of preparation of silage and freshly cut forage samples for the estimation of rumen degradability by the nylon bag technique. Three types of forage were evaluated: a grass silage, a fresh grass (ryegrass) and a fresh legume (white clover). For each forage, six preparation methods were compared: chopping fresh (FRS); chopping and macerating fresh (FMC); chopping, freezing, thawing and macerating (FRZ); freeze-drying (FD); low-temperature oven-drying (45°C, 72 h) (OVD); high-temperature oven-drying (160°C, 90 min) (DHD). Dried samples were hammer-milled (2·5-mm screen). Chemical composition and rumen degradability were affected by the method of preparation. Protein fractions were sensitive to drying method, and oven-drying reduced nitrogen (N) solubility and degradability as the severity of the heating was increased. OVD and DHD gave lower estimates of N and dry matter (DM) solubility and degradability than FD. The effect of drying method on DM degradability was to reduce solubility and effective degradability, calculated for an outflow rate of 0·033 per h, but not potential degradability.

Silage DM degradability was less affected than that of fresh forages. Freshly prepared samples (FRS, FMC, FRZ) gave lower estimates of N and DM solubility and degradability than FD, the differences being least with silage and FRZ, which was the most effective at rupturing plant structures of the FRS, FMC and FRZ methods. Of the six preparation methods, freeze-drying was the most effective preparation method. FRZ and OVD were less effective, but similar to each other. The small particles (calculated) produced by grinding dried samples may result in an overestimation of zero time losses and hence the degradability of the sample. These undesirable effects might be minimized by coarser grinding (4-mm screen) and correction for particulate matter loss.

The effect of melatonin implants administered to cashmere goats in the winter, on plasma prolactin, triiodothyronine (T3) and thyroxine (T4) concentrations and the timing of the spring moult, was studied with the objective of identifying a method of manipulating the timing of the spring moult and increasing fibre harvesting efficiency. The effect of similar melatonin implants on prolactin concentration when administered in the increasing daylength of spring, was also measured.

In the first experiment, using 20 juvenile and 20 adult female cashmere goats, half the animals of each group received continuous release implants of melatonin (18 mg) on 11 December, 1 February and 1 April. In the adult goats the treatment significantly advanced by 7 weeks the time at which peak plasma prolactin concentrations were attained (P < 0·001) and advanced the onset (P < 0·001) of the peak. The treatment also resulted in an advance of the spring moult of cashmere in the adult goats (P < 0·01) and in an earlier initiation (P < 0·01) of the growth of both guard hair and cashmere as judged by histological examination of primary and secondary hair follicles. In the juvenile goats there were no significant effects of melatonin administration on plasma prolactin concentrations, the timing of the moult, or on any of the histological measurements compared with the controls. There were no significant effects on live weight or circulating concentrations of T3 and T4 in either age group. In the second experiment, the administration of one melatonin implant (18 mg) to three adult goats on 1 April caused a significant reduction in plasma prolactin concentrations (P < 0·05) over a period of 3 weeks compared with concentrations observed in four untreated goats.

It is concluded that treatment with melatonin implants is effective in modifying the timing of the seasonal cycle in prolactin secretion in adult cashmere goats and causing corresponding changes in hair follicle activity. However, since the treatment initiated in December caused an advance rather than a delay in the normal spring rise in plasma prolactin concentrations, it is evident that the repeated melatonin implant protocol used in this experiment cannot be used to delay the onset of the spring moult and thus facilitate the harvesting of cashmere.

The cover comb has been developed in New Zealand as a means of increasing residual fleece depth after shearing and so increasing the resistance of shorn sheep to cold stress.

The effects of shearing by cover comb and standard comb were studied over 2 days pre-shearing and 10 days post-shearing in eight pairs of non-pregnant, non-lactating 2-year-old ewes. Animals were housed and given a maintenance level of chaffed lucerne hay. One member of each pair was shorn with a cover comb, the other with a standard comb. Each pair was exposed to ‘cold plus wind’ (7°C ambient temperature, 7 km/h air movement) followed by ‘cold plus wind plus rain’ (10°C ambient temperature, 7km/h air movement, wetting at a rate equivalent to 25 mm/h rain from overhead sprinklers) in a calorimetry chamber on days S –3, S –2, SO (day of shearing), S2, S6 and S10. Heat production immediately after shearing (SO) was proportionately 0·22 greater in ewes shorn by the standard comb under conditions of ‘cold plus wind’ and 0·38 greater under conditions of ‘cold plus wind plus rain’ than in their cover comb-shorn cohorts. Circulating concentrations of non-esterifiedfatty acids were substantially elevated on the day of shearing and 2 days thereafter in ewes shorn by the standard comb, indicating increased rates of body fat mobilization to support heat production in these ewes compared with those shorn by the cover comb. This was reflected in a 1·4 kg weight loss in the standard comb-shorn ewes compared with a 0·4 kg live-weight gain in the cover comb-shorn group over the 10 days of the experiment. It was concluded that use of a cover comb will significantly reduce the risk of death from hypothermia in sheep shorn during winter and spring, and should facilitate an increase in the productivity of animals by allowing a greater proportion of food energy to be used for productive purposes.

The effect of erythrocyte glutathione status and breed on the susceptibility of adult female sheep to the haemolytic anaemia caused by the brassica anti-metabolite dimethyl disulphide (DMDS) was determined in a factorial experiment. Within each breed (Scottish Blackface or Finnish Landrace), six sheep of low glutathione status (<30 mg/100 ml red blood cells (RBC)) and six sheep of high glutathione status (>70 mg/100 ml RBC) were dosed twice daily with DMDS for 35 days (25 mmol per head per day). All sheep developed a classic haemolytic anaemia within 2 weeks of the start of DMDS dosing. Weekly haemoglobin concentrations and packed cell volume values were not affected by breed or glutathione status. Heinz body numbers rose to a higher maximum in low glutathione animals but were not affected by breed. The results call into question the relationship between total erythrocyte glutathione concentration and the resistance of erythrocytes to oxidative damage.

Six different breed groups (Yorkshire (Y), Pietrain (P), a Pietmin derivative breed Near Pietrain (NP), and crosses NP × P, P × NP and F2) were tested for breed, skeltal muscle ryrl genotype (hal gene), and sex effects on growth, performance and carcass traits. Within the C/C (homozygous normal for the hal gene) or T/T (homozygous recessive for the hal gene) ryrl genotypes there were significant differences among breed groups in a number of performance and carcass quality traits. In contrast, the performance and carcass quality traits of the C/T (heterozygous for the hal gene) ryrl genotype-containing breed groups were similar. In the four breeds containing C/T and T/T ryrl genotypes, the additional copy of the ryrl T allele had a significantly positive effect on all measures of amount of lean meat with a negative effect on all meat quality scores (P < 0·001). Notably, the C/C and T/T ryrl genotypes in the NP and F2 breed groups differed significantly in all measures of amount of fat and lean; the C/T genotype was intermediate to the C/C and T/T genotypes in all traits with the C allele exhibiting partial dominance for these measures. It is concluded that within breed groups of similar genetic background, the ryrl genotype has positive effects on all measures of the amount of fat and lean, with associated negative effects on meat quality. The availability of the DNA-based test to identify the ryrl genotype allows pig breeders to take advantage of the beneficial traits or to eliminate the deleterious traits associated with this gene from their populations.

A selection index for overall economic merit and five subindexes for maternal and lamb traits were constructed. For estimation of breeding values, two computer programs were developed. A multiple-trait animal model was programmed for the ewe traits including number of lambs born ofl-, 2- and 3-years-old ewes and ewe fleece weight of yearlings. In order to reduce the memory requirement, the lamb data (growth rate, carcass weight, carcass grade, fat% and lamb fleece iveight) were analysed by a reduced multiple-trait animal model including genetic maternal effect. Experiences with the computer programs in genetic evaluation of approximately 619 000 animals are presented. It is concluded that the models and computing strategy may be used for genetic evaluation in the national sheep breeding programme in Norway.

Relative economic values for all traits were derived from a profit equation on a 3-year-old ewe basis. The sensitivity towards changed economic values urns found to be low. Further, the genetic change in the ewe traits of the Norwegian breeds has been estimated, and a significant improvement was found, which was two to four times higher in the ram circles than outside. For breeding rams, the genetic change for number of lambs born was estimated to be approximately 0·01 lambs per ewe and year.

The present experiment was undertaken to investigate adaptations to insulin action on metabolism during lactation by using plasma concentrations of β hydroxybutyrate (β OH) free fatty acids (FFA) and lactate (L) as indicators. The study included three groups each of four goats. One group was used at 12 to 31 days post partum (early lactation), one group at 98 to 143 days post partum (mid lactation) and one group at 1 year post partum (dry period). For a given physiological state, each goat was examined four times to study the effect of insulin infused for 2·5 h at two rates, medium (0·36 nmol/min) followed by high (1·79 nmol/min) in two protocols: under normal aminoacidaemia in study 1 followed by hyperaminoacidaemia in study 2. Appropriate amino acid infusions were used to blunt insulin-induced hypoaminoacidaemia under eukaliaemic and euglycaemic clamp conditions or to create hyperaminoacidaemia and maintain this state under insulin treatment. In the basal state βOH (P < 0·05), mid lactation) and FFA (P < 0·05 early lactation) were higher during lactation than in the dry period. Plasma L was unmodified. Insulin infusion always resulted in a decrease in βOH levels (P < 0·05). In both studies, the change in βOH concentration as a function of changes in plasma insulin (an index of insulin sensitivity) was greater during early lactation than in the dry period (P < 0·05); this was also the case of mid lactation in study 1. Insulin infusion decreased plasma FFA during early lactation and in the dry period in study 1 (P < 0·05), and there was a trend for insulin sensitivity to be greater during early lactation. In both studies insulin infusion did not affect plasma L in lactating goats whereas plasma L was increased in dry animals (P < 0·05). The results demonstrate that during early lactation, compared with the dry period, there is an increased ability of insulin to lower βOH and FFA concentrations. These effects were not altered by increasing plasma amino acid concentrations during insulin infusion.

A crossbreeding trial extending over three generations was used to investigate the genetic components contributing to the prolificacy of the Meishan breed in comparison with the Large White breed. Information on the number of teats and on body weight and litter size in the first two parities was recorded on purebred Meishan and Large White females and on reciprocal F1 and backcross females. Ovulation rate was also recorded for all litters, allowing the estimation of per litter prenatal survival. Crossbreeding parameters for direct, maternal and grandmaternal effects were estimated using restricted maximum likelihood analysis. There was a consistent advantage of three to four piglets born alive to the Meishan female compared with the Large White female. This was controlled by the maternal genotype, with no effect of the genotype of the litter itself. Both additive and heterosis effects were important, the contribution of additive maternal effects to the breed difference being similar across parities (4·0 (s.e. 1·1) and 4·2(s.e. 1·1), in the two parities respectively) and the maternal heterosis increasing slightly across parities (2·2 (s.e. 0·8) and 2·9 (s.e. 0·8), in the two parities respectively). The number born alive to F 1 females was similar to, or greater than, the number born alive to Meishan females. Ovulation rate was significantly higher in Meishan than in Large White females and this was controlled by additive gene effects which had a similar effect across parities, the weighted average of their contribution to the breed difference being 5·7 (s.e. 0·8) ova. Differences between the breeds in prenatal survival were small, although there was significant maternal heterosis, however, the maternal additive effect became significant after the inclusion of ovulation rate as a covariate. After adjustment for ovulation rate, the weighted average estimates across parity of the maternal additive contribution to the breed difference and the maternal heterosis for the proportional prenatal survival loere 0-14 (s.e. 0·05) and 0·13 (s.e. 0·03), respectively. This suggests that a combination of a high ovulation rate and especially a high level of prenatal survival for that ovulation rate led to the prolificacy observed in this sample of Meishan pigs. The inclusion of ovulation rate as a covariate in the analysis of number born alive confirms this view, as the maternal additive effect on litter size was only reduced by about one third and the heterosis effect was largely unchanged. Both numbers stillborn and mummified were increased in litters born to Meishan sows due to maternal additive effects, but the effects seemed largely a consequence of the increased ovulation rate as they became non-significant after its inclusion as a covariate in the model.

Ovulation rate, embryo survival, lamb production, lamb survival and milk production of Awassi and BooroolaAwassi crossbred ewes, kept indoors, were compared. Awassi were non-carriers while Booroola × Awassi (F1) and about half of 3/4 Awassi-1/4 Booroola (BQ) ewes were heterozygous at the FecB gene. Mean ovulation rate increased by 1·5 to 1·6 corpora lutea per ewe ovulating and prolificacy by 0·7 lambs born per ewe lambing in Fj and BC1 (B+) ewes as compared with Awassi. Embryo survival rates in BC1 ewes with two, three and four ovulations were 0·83, 0·68 and 0·71, respectively. Lamb survival rates at 1 day of age were 0·93, 0·90 and 0·77 and average birth weight was 4·9, 4·0 and 3·0 kg for lambs born as singles, twins and triplets, respectively. Average milk production of the Awassi was 506 I per ewe per lactation. F1 and BC1 ewes produced respectively, proportionately 0·48 and 0·63 of the Awassi milk production and there was no significant difference in milk production between BC1,(B+) and BC1(++) ewes. The relatively low milk production of the Booroola Awassi crosses suggests that heterosis and recombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb production in the Awassi without affecting its milk production.