The present study was undertaken to assist conservation and improvement schemes in the Sahiwal breed of cattle in Pakistan. A data set, consisting of records of 244 pure Sahiwal breeding bulls and 5247 cows, the latter representing about 80% of all recorded Sahiwal cows in Pakistan born during a period covering about 20 years, was analysed with regard to inbreeding, additive relationships, effective population size and generation intervals. Average inbreeding coefficients of 1224 cows and 49 bulls, for which at least the grandparents and great-grandsires were known, were 0·043 and 0·046, respectively. About two-thirds of the inbreeding was due to matings between animals with parents or grandparents in common. The mean additive relationship among the cows was 0·062, with within-herd averages ranging from 0·087 to 0·358. The average population size in a subdata set of recorded Sahiwal cattle from 1980 to 1984 was 1612, whereas the most likely estimate of the effective population size was about 30 animals for the same active breeding population. The study indicated the immediate need for an active conservation programme whereby the Sahiwal subpopulations of India and Kenya also should be involved.

The study determined the effects of partial removal of alkaloids (detoxification) in crushed lupin seed (CLS) on voluntary food intake, and yield and composition of milk from dairy cattle. Twenty multiparous Friesian dairy cows (first 90 days of lactation) were assigned, according to a randomized complete-block design, to five diets. The diets were formulated to be isonitrogenous (25·6 g N per kg of diet dry matter (DM)) and contained napier grass, lucerne hay, maize bran and urea. The control diet (CON) contained sunflower meal; two diets contained intact CLS at 150 (LUI-15) or 300 g (LUl-30) per kg diet DM. The other two diets contained detoxified CLS at 150 (LUD-15) or 300 g (LUD-30) per kg diet DM. Lupin seeds were detoxified by treatment with boiling water, followed by steeping in cold water. The diets were analysed by gas chromatography for the alkaloids, lupanine and 13-hydroxylupanine. The total alkaloid content of LUI-15 and LUl-30 was 3·8 and 8·0 g/kg diet DM, respectively; by contrast that of LUD-15 and LUD-30 was 2·1 and 5·2 g/kg diet DM respectively. Increasing the level of intact CLS in the diet led to a decrease in voluntary food intake. Cows given LUl-30 had a lower milk yield (11·1 kg/day) than those given LUI-15 (13·8 kg/day; P < 0·01) but there was no difference in either milk protein yield or content. Detoxification of lupin removed proportionately about 0·40 of the total alkaloids from intact CLS and increased food intake, and the yield of milk and milk protein (P < 0·05) but reduced milk fat content. Detoxification of CLS also reduced the rumen degradability of lupin protein (P< 0·05). It is concluded that the reduction in organic matter intake and milk yield of cows given diets containing intact CLS was due to the presence of lupanine and 13-hydroxylupanine. To maximize its usage in diets for dairy cattle, lupin should be detoxified; it can then be included at levels up to 300 g/kg diet DM.

In a prospective 2-year study, milk progesterone and oestrone sulphate determinations were used to monitor and assess pregnancy in lactating cows. The testing was done centrally at a government regional veterinary establishment which was responsible for providing semen to the farms of the area and also had available specialist expertise in animal reproduction. Sample collection and dissemination of test results were achieved through the network of the artificial insemination service. This approach was preferred because it was considered ergonomic, cost-effective and reliable. Comparison of oestrus behavioural signs and progesterone on the day of insemination revealed that 7·8% (89/1133) of the animals tested had high progesterone levels. Single progesterone testing on day 21 post insemination was not satisfactory for pregnancy diagnosis as the positive predictive value was 83·0% (147/177). The combination of low progesterone on day 0 and high progesterone on day 21 improved the positive predictive value to 87·4% (235/269). Results from 400 samples taken 110 to 130 days post insemination from 53 animals revealed that cows with oestrone sulphate concentrations greater than 0·1 μg/l actually calved. This assay appears to be particularly suitable as a pregnancy confirmation test. A pilot field study implementing a programme of testing on days 0, 21 and 42 for progesterone and between days 110 to 130 for oestrone sulphate not only achieved almost absolute pregnancy predictive values but careful result analysis strongly indicated that the approach of systematic testing can also reveal the fertility profile of a given herd and help to identify potential causes of pregnancy failure from the period of the reproduction cycle in which they occur.

Heritabilities (h2) and genetic correlations (rc) involving body weights, measures of testes size and ewe lamb reproduction were calculated using 953 spring-born lambs produced during formation of a three-breed composite population containing 0·50 Dorset, 0·25 Rambouillet and 0·25 Finnish Landrace breeding. The h2 of body weight ranged from 0·2 to 0·3 between 45 and 150 days of age, but increased to 0·41 at the start of breeding of ewe lambs at about 6 months of age. Additive maternal effects were not important, perhaps because intensive housing encouraged cross-suckling. Testes size was measured as scrotal circumference (SC), SC with linear adjustment for weight (SCW) and SC divided by the one-third power of body weight (RSC). The h2 of SC traits was highest at 90 days (0·52 for SC, 0·62 for RSC and 0·57 for SCW), and h2 for age at maximum SC growth rate (i.e. TI, the inflexion point of a logistic SC growth curve) was 0·49. The h2 of ewe lamb fertility in autumn was 0·09 but the h2 for frequency of remating the following spring was 0·41. The h2 for ewe lamb litter size in these data was zero. At 90 days, rc between alternative measures of testes size exceeded 0·86; rG with body weight were 0·67 for SC, 0·53 for RSC and –0·74 for TI. The rG with ewe lamb fertility for 90-day weight, SC, RSC and SCW and for TI were –0·25, 0·20, 0·25, 0·38 and –0·32, respectively. The rc for these traits with spring remating were 0·34, 0·34, 0·26, 0·10 and –0·48, respectively.

The commercial value of animal carcasses depends not only on their weight but also on their composition and shape (termed conformation). This is usually assessed subjectively by a skilled inspector. In this paper an attempt is described to assess the saleable meat yield of sheep carcasses by automatic digital image analysis. A low-cost system based on a still video camera and a personal computer was used. The results indicate that better prediction of saleable meat yield can be obtained using objective measures of carcass shape than from subjective conformation scores. Information from the intensities of colour components was not found to be useful, possibly due to difficulties with lighting and image quality. Recommendations are made for implementing a practical system.

The effect of bromocryptine on milk production was investigated in 32 crossbred ewes (Flemish Milksheep х Suffolk) with one sucking lamb, during lactation and during drying off. After weaning the lambs, all ewes were hand milked twice daily for 3 days. From day 4 onwards, the ewes were divided into four groups with equal mean daily milk production. Ewes of groups A and B were hand milked twice daily during the following 9 days. Ewes of groups C and D were dried off by reducing the milking frequency. They were milked on days 5, 8 and 12. In groups B and D, bromocryptin (1 ml of 1 g/l ethanol 50%) was injected intramuscularly twice daily while control ewes (groups A and C) received 1 ml ethanol 50%. Blood samples were taken by venipuncture prior to each injection and were assayed for prolactin, growth hormone, thyrotropin and cortisol.

Bromocryptine decreased plasma prolactin levels but did not alter growth hormone or cortisol concentrations during lactation or drying off. Thyrotropin levels were elevated by bromocryptine during drying off but were unaffected during galactopoiesis.

During lactation the daily milk production remained unchanged in control ewes while in bromocryptine-treated ewes a proportional decrease of 0·5 was observed. In all ewes the decrease in milk production occurring at drying off could not be accelerated or stimulated by bromocryptine.

It is concluded that prolactin plays an important role in galactopoiesis in ewes but its role is comparatively unimportant compared with other factors during mammary involution.

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.

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.

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.

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.

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.

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 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.

Growth and survival from birth to weaning were monitored during three generations of crossbreeding between British Large White (LW) and Chinese Meishan (MS) pigs. The design allowed comparisons between sow genotypes ranging from zero to all MS genes, which were mated toLWor MS boars, to produce progeny with proportions of 0·0 to 0·5 or 0·5 to 1·0 MS genes, respectively. Crossbreeding parameters of both maternal and direct piglet performance were estimated for the first two parities using restricted maximum likelihood (REML) methods for litter traits (litter weight at birth, litter mean and within litter standard deviation of piglet weight at birth, proportion surviving to weaning, litter size and weight at weaning and litter mean piglet weight at weaning) and for traits of the piglet (birth weight, probability of survival and weaning weight). For litter traits, the estimated contribution of the additive maternal effect to the breed differences (MS-LW) was significant for litter mean piglet birth weight (–0·46 (s.e. 0·04) kg), survival to weaning (0·15 (s.e. 0·02)), litter size at weaning (1·6 (s.e. 0·16) piglets), litter weaning weight (–11·2 (s.e. 3·8) kg) and litter mean piglet weaning weight (2·54 (s.e. 0·24) kg). Adding litter size and litter mean piglet birth weight to the model removed the additive maternal contribution to the breed differences in survival, and litter size and reduced that for litter mean piglet weaning weight. The contribution of the direct additive effect to the breed difference (MS-LW) was significant for the within litter standard deviation in birth weight (0·018 (s.e. 0·006)), survival to weaning (0·12 (s.e. 0·02)) and litter size (1·12 (s.e. 0·64)) and weight (11·6 (s.e. 4·0) kg) at weaning, but not for piglet weight at birth or weaning. Fitting litter size and litter mean birth weight had comparatively little impact on the direct additive effects. There were significant maternal heterosis effects for litter weight at birth and litter size and weight at weaning, the estimated deviation of the F1 from the midpoint of the two purebreds 3·22 (s.e. 0·55) kg, 2·20 (s.e. 0·47) piglets, and 20·1 (s.e. 3·3) kg respectively, but none for survival or piglet weights. There were direct heterosis effects for litter weight and litter mean piglet weights, the estimated deviation of the Fjfrom the mid point of the two purebreds being 1·16 (s.e. 0·41) kg and 0·14 (s.e. 0·02) kg, for survival to weaning (0·04 (s.e. 0·02)) and for litter weight (11·2 (s.e. 2·5) kg) and litter mean piglet weight (0·96 (s.e. 0·17) kg) at weaning. Fitting litter size and litter mean piglet birth weight removed or reduced both maternal and direct heterosis effects. Individual piglet analyses gave similar results to analyses of the equivalent sow trait. It was concluded that in litters born to MS cows, the lower piglet survival and lower weaning weights were related to the larger litter sizes and lower piglet birth weights. For their birth weight, however, MS piglets have a greater ability to survive and thrive. The large direct and maternal heterosis effects observed for litter and mean piglet weight at weaning werepartly associated with the heavier birth weight of the crossbred piglet.

Correlated responses in reproductive performance to five generations of divergent selection for daily food intake (DFI), lean food conversion (LFC), lean growth rate on ad–libitum feeding (LGA), and lean growth rate on scale feeding (LGS) were studied. Litter traits were measured on 1220 Large White gilts. Mean litter weights at birth and weaning were 12·9 kg and 63·5 kg, with average litter sizes of 10·3 and 7·9. Responses to selection in the high and low lines for litter size in the DFI and LFC selection groups were 1·9 and –1·5 (s.e.d. VI) at birth and 0·9 and –1·8 (s.e.d. 1·2) at weaning. Responses in litter birth weights were respectively positive and negative for DFI and LFC (3·0 and –2·8 (s.e.d. 1·4) kg) and the response in LGS (3 kg) was greater than in LGA (–0·1 kg). Selection line differences in litter weaning weight followed a similar pattern to birth weight for DFI and LFC (17·5 and –17·3 (s.e.d. 10·1) kg). Responses in litter weights were a result of selection line differences in both litter sizes and piglet weights. The relationships between litter size, litter weights and piglet weights at birth and weaning were essentially linear. An extra piglet at birth and weaning corresponded to an increase of 1·0 (s.e. 0·02) kg and 6·9 (s.e. 0·1) kg in litter weights. Piglet birth and weaning weights were decreased by 0·03 (s.e. 0·003) kg and 0·19 (s.e. 0·02) kg. A uterine constraint on piglet growth was implied, but there was no evidence for a limit to uterine capacity. Heritabilities for litter size, weight and piglet weight at birth of 0·06, 0·11 (s.e. 0·04) and 0·16 (s.e. 0·02) respectively were similar to those at weaning. Common environmental effects on piglet weights at birth and weaning were substantially higher than the heritabilities (0·38 and 0·45, s.e. 0·01). The study indicated that selection for lean growth on either an ad–libitum or restricted feeding regime did not significantly affect reproductive performance, but the high lean food conversion ratio and low daily food intake selection lines had impaired reproductive performance.

Intact male pigs from two nucleus breeding herds (one predominantly Duroc, DM; the other purebred Large Wliite, LM) together with intact male (RM), castrated male (RC) and female (RF) commercial hybrid pigs were given one of two diets, with the same balanced protein (180 or 240 g/kg) at three daily rates, the highest being ‘to appetite‘. Six replicates of 30 pigs were allocated to these regimes at 40 kg: one replicate was slaughtered immediately to determine initial carcass composition; the remaining pigs were slaughtered at 85 kg when carcass fat and specific gravity (SG) were measured. For two replicates this was followed by dissection and chemical analysis: daily gains of carcass lipid and protein were estimated directly for these two replicates and predicted from carcass weight and SG for the other three. Fed ‘to appetite’, castrated males and females ate more than males; LM pigs ate least. All males grew faster than females or castrated males, the DM pigs the fastest, these rankings being relatively insensitive to feeding level. However, both in daily weight gain and daily protein accretion only the males responded to additional dietary protein. Daily body protein accretion of DM pigs increased linearly with intake on both diets whereas LM pigs showed little response to the highest level of feeding. At the same daily protein intake all pigs had higher rates of body protein accretion on the low protein diet, showing that they were sensitive to additional dietary energy. Results indicate that an animal's superiority may result from a greater efficiency of protein utilization or a higher lean growth potential but that these two characteristics are not simply related.

Two experiments were conducted to examine the effects of dietary inclusion of an ephedrine (Eph)/caffeine (Caf) mixture on finishing (55 to 100 kg live weight) castrated male pigs. The first experiment was conducted as a dose-response study and showed that the mixture had an optimal effect on performance and carcass composition at a dietary inclusion level of approximately 56/560 mg/kg of Eph and Caf, respectively. In the second experiment, interactions between the compounds were studied by dietary inclusion of Eph (56 mg/kg) and Caf (560 mg/kg) separately or as a mixture (56/560 mg/kg). The mixture reduced food intake by 0·12 and improved the food: gain ratio by 0·08. Muscle protein deposition rate was increased proportionately by 0·25, lipid accretion rate was decreased proportionately by 0·27, and gross energetic efficiency of energy deposition decreased proportionately by 0·09. This resulted in a changed proportional carcass composition towards more muscle (0·08) and less fat (0·21) after treatment with the mixture. The reduction in food intake was sustained due to an interaction over the first 3 weeks of treatment changing to additive effects by the compounds. The increased muscle protein deposition rate after feeding the mixture was entirely due to Eph, while the decreased gross energetic efficiency of energy deposition was caused by Caf. On the other hand, both compounds contributed almost equally to the decrease in lipid accretion rate. These results show that an Eph/Caf mixture markedly improves performance and body composition in finishing castrated pigs.

The feeding patterns of sows using electronic feeders were monitored automatically (via a computer interface) over a period of 15 months. This paper reports on the variability in the size of the first meal of the day in relation to total daily food intake. The results demonstrated a pattern that bears some similarity to that observed by other workers, namely that sows tend to take all their daily food allocation in a single meal. In general, sows (79%) ate most of their daily allowance in a single visit to the feeders. However, on a significant minority of occasions (21%) this was not the case. The results also showed that there was a considerable number of sows (87% of the herd) that fed in a variable pattern, i.e. considerable variation in the proportion of their daily allowance taken in a single visit. This unpredictability was found throughout the sow herd. Some, but not all of this variability could be attributed to differences between parities (P < 0·001) and also there was some evidence that some sows, when newly introduced into the herd, were more variable in behaviour than more established sows. However, a large amount of variation remains unexplained. The need to provide flexible sow management to accommodate individual behaviour is discussed. Additionally, appropriate sampling periods of considerable duration are shown to be important in describing feeding patterns of group-housed sows.

Variance components for litter size (total number of piglets born) were estimated from Danish purebred Landrace and Yorkshire litters by restricting maximum likelihood. The data were collected from the national Danish breeding programme and consisted of 19 666 litters in Danish Landrace and 29 336 litters in Danish Yorkshire. Four different analyses for litter size were conducted within breed. In the first two, genetic groups were included in the model in order to account for the importation of animals from other countries; in the other two, genetic groups were removed from the model. Within each case, herd-year-type of insemination effects were fitted as fixed (H-fixed models), or herd-year-season-type of insemination effects were fitted as random (H-random models). Estimates of heritability ranged from about 0·11 to 0·14 in Landrace and from 0·10 to 0·11 in Yorkshire. Variance due to herd-year-season-type of insemination ranged from 0·029 to 0·041 of total variance, values somewhat lower than those obtained for non-genetic permanent effects. In order to compare the four models, data were divided into different subsets, and records from one subset were predicted using parameters estimated from the other subset. Both the correlation between observed and predicted values, and the mean squared error of prediction indicated that predictive ability was higher in the case of H-random models. There was no evidence that genetic groups improved the predictive ability for litter size. However, group effects affected inferences about genetic trend, particularly in Landrace, where genetic group composition changed consistently over the years.

In a factorial design, animal fat was added incrementally (0, 35, 70 and 105 g/kg) to maize starch (M) or to two sources of fermentable carbohydrates (260 g purified cellulose (C) per kg or 270 g soya-bean hulls (S) per kg). The 12 experimental diets were formulated by replacing maize starch in the control diet with fat, cellulose and soya-bean hulls of equivalent estimated net energy. Ninety-six castrated males were given these diets according to net energy. Apparent digestibilities of crude protein, crude lipid, crude fibre and nitrogen-free extract were measured and were compared with those expected from the separate ingredients. Net energy conversion ratio (nECR) was also measured. Results showed that in the C and the S diets prediction of the apparent digestibility of nutrients was worse than in the M diets (significant effect of source of carbohydrate). Prediction of apparent digestibility of crude protein and crude lipid improved as the added fat increased (significant effect of amount of fat), except in the C and S diets where for digestible crude lipid the 70 g added fat per kg gave the worst prediction (significant effect of the interaction). The net energy calculated from the experimental data on apparent digestibility was proportionately between 0·83 and 0·98 of that calculated from the expected data. The pigs on the C and S treatments showed a significant lower nECR when calculated from the expected apparent digestibility coefficients, but not when calculated from those which were measured. At the highest fat addition, the nECR was poorest. It is concluded that the amounts of digestible components in compound foods cannot always be obtained from those in the separate ingredients.