Records on total of 1746 calvings of principally Milking Criollos and their crosses were collected between 1972 and 1990 at the experiment station of the Mexican Association of Animal Production on the Gulf Coast of Mexico. Traits of interest were 305-day milk yield, days in lactation, number of services per lactation (raised to power 1/2), age at first calving and lifetime milk yield. Data were analysed by restricted maximum likelihood (REML) under an individual animal model based on 584 animals of which 146 were female ancestors and 35 were male ancestors. Heritabilities of 305-day milk and age at first calving were 0·17 and 0·07, respectively, but heritabilities of other traits were close to zero. Genetic trend in the Milking Criollos for 305-day milk was small and not significant (0·76 (s.e. 2·38) kg/year). Of crosses with Criollo sires, those involving Holstein and Canadienne breeding had highest 305-day and lifetime milk yields and those involving Brown Swiss and native Mexican (mostly Oaxaca) had lowest yields. Jersey crosses were intermediate for 305-day yield. The F1 Criollo × Jersey cross had highest lifetime yield, but backcrosses involving Jersey breeding were poor for lifetime milk. Additive breed effects for Jersey and Canadienne, relative to Milking Criollo, were 88 (s.e. 91) and 227 (s.e. 74) kg 305-day milk, respectively. Heterosis was 144 (s.e. 55) kg (11·6%) for 305-day milk, 16–4 (s.e. 9·6) (5·0%) for days in milk, −0·107 (s.e. 0–042) (7·7%) for number of services per lactation raised to power 1/2, −25·6 (s.e. 41·4) days (2•3%) for age at first calving and 1789 (s.e. 664) kg (60·0%) for lifetime milk. A plan was designed to develop a nucleus breeding scheme utilizing multiple ovulation and embryo transfer technology (MOET) for the genetic improvement of the Milking Criollo breed in Mexico.

Forty-eight spring-calving, Holstein-Friesian cows were continuously stocked on perennial ryegrass-white clover swards maintained at compressed sward heights of 4, 6 or 8 cm and offered 0 (U) or 4 (S) kg concentrates. Milk yields and composition, live weights and intakes (estimated by the n-alkane technique) were recorded for periods 24 May to 27 June (P1) and 28 June to 8 August 1992 (P2) with 4 cm swards not used in P2. Milk and component yields were significantly lower at 4 cm than at 6 or 8 cm in P1 and significantly higher when supplements were offered in both periods with no significant interaction. Herbage intakes were reduced more by supplementation at lower sward heights. Live weight was significantly lower on the 4 cm sward. Fat concentrations were unaffected by height and supplementation in P1 but significantly increased by supplementation in P2. These results suggest that maintaining a sward height of 6 cm offers advantages in terms of individual animal output and output per ha compared with grazing at greater or lower sward heights.

Inbreeding leads to reduction of the additive variance, whereas inbreeding depression reduces the performance of milk producing cows in both the nucleus and the commercial population. In this study, the cumulative additive response to 30 years of selection corrected for variance reduction due to inbreeding and inbreeding depression in the commercial cow population (denoted as expected phenotypic level or P) was evaluated in a closed (1024 cows tested per year) dairy cattle nucleus scheme, assuming a large number of gametes available per female. No dominance effects were simulated nor estimated in the nucleus. Various hierarchical and factorial designs with fewer sires than dams, an equal number of sires and dams, or even a larger number of sires than dams were compared for P. The trait considered was overall economic merit for milk production with a heritability of the unselected base population of 0·30. Sires and dams were selected on their animal model estimated additive effect for the trait considered at either 15 or 27 months of age. All full-sibs were available for selection. In the absence of inbreeding depression, a complete factorial scheme with more sires than dams resulted in the highest P. With increasing inbreeding depression, the optimal number of sires increased relatively more than the optimal number of dams. Increasing the number of sires decreased inbreeding relatively more than increasing the number of dams, and resulted in a relatively higher P. This is due to the fact that correlations between estimated additive effects of male selection candidates are higher than between those of female selection candidates.

Twenty lactating dairy cows were used to investigate the relationship between the site of milk storage in the udder and the short-term response to thrice-daily milking. Cisternal and alveolar milk volumes were measured 8 h after an ordinary morning milking by catheter drainage and machine milking with oxytocin respectively. The response to thrice-daily milking was assessed using a half-udder technique and the relative milk yields quotient (RMYQ). Over the first 7 days, both halves were milked twice daily (8/16 h intervals) and milk yields over the final 4 days of this period were higher for left fore/right hind (LF/RH) (12·4 (s.e. 0·85) kg/day) than for RF/LH (10·5 (s.e. 0·63) kg/day) which was milked after LF/RH throughout the experiment. Over the following week, LF/RH quarters were milked an additional time (8/8/8 h intervals) and yields over the final 4 days were increased (15•7 (s.e. 0·95) kg/day) compared with control quarters (9·8 (s.e. 0·73) kg/day). In a final 4-day period, animals were milked twice daily and half udder yields were 13·1 (s.e. 0·89) kg/day and 10•6 (s.e. 0·77) kg/day respectively. Differences between yields from the two halves of the udders were highly significant in all 3 weeks of the experiment (P < 0·001). Cistern milk yield as a proportion of total milk yield at 8 h (cistern proportion) averaged 0·170 (s.e. = 0·0275; range 0·020 to 0·334) and tended to be greater for multiparous (0·215, s.e. 0·0279) than for primiparous animals (0·118, s.e. 0·0437; P = 0·076). During the periods of twice-daily milking, the proportion of milk yielded from LF/RH quarters was not significantly related to cistern proportion (P = 0·70 and 0·43 for weeks 1 and 3 respectively). However the response to thrice-daily milking, assessed as RMYQ, was significantly related to cistern proportion both when changing up to, and down from, thrice-daily milking (P < 0·01). Animals with low cistern proportions showed larger responses to thrice-daily milking. There was a significant relationship (P < 0·05) between the responses on changing up to, and down from, thrice-daily milking. Primiparous animals tended to exhibit smaller declines on returning to twice-daily milking than multiparous animals with equivalent responses to thrice-daily milking.

The accuracy of progeny testing for a continuous trait when the auxiliary information was based on ‘all-or-none’ type of traits with a multi-factorial threshold model was examined. The accuracy of the progeny test was found always to increase with the inclusion of the auxiliary trait. It followed the same pattern as in the case of continuous auxiliary trait. However, there was an additional feature in that the accuracy was also dependent on the probability of incidence of the discrete trait unless either the progeny group size was very large, and/or there was no genetic correlation or else the probability of incidence was itself extremely low. Compared with the case when the auxiliary trait was continuous, there was a loss in accuracy which can be looked upon in two ways. First, the continuous auxiliary trait is itself made ‘all-or-none’ type by a threshold and the accuracies compared in the two cases. The loss increases symmetrically in either direction with increase in positive or negative directions of the difference in genotypic and phenotypic correlations. Secondly, a comparison can be made of the accuracy when the auxiliary trait is normally distributed with that when it is binomially distributed but with the same amount of genetic information on the observed scale as given by the heritabilities and genetic correlations. No loss now occurs if the two classes of the binomial trait are equally likely and the loss in accuracy increases with the decrease in the standard deviation of the binomial distribution for given values of other parameters. It was found also that the use of binomial auxiliary trait reduced the number of progeny required to attain a pre-assigned level of accuracy, resulting in a decreased cost of the programme compared with that when no binomial auxiliary trait was used.

An experiment was conducted to examine the response of three genotypes of beef cows to contrasting levels of nutrition supplied from grazed pasture. Twenty-two Hereford × Friesian (HF), 20 Aberdeen Angus × Friesian (AF) and 24 Welsh Black (WB) spring-calving beef cows with their Charolais-cross calves were used in 4 years consecutively. During the summer grazing period they grazed permanent pasture maintained at either 4 to 5 cm (short) or 7 to 8 cm (tall) sward surface height. Sward height treatment significantly (P < 0·001) affected cow and calf live-weight gain (0·498 v. 0·041 (s.e.d. 0·0405) kg/day and 1·12 v. 0·90 (s.e.d. 0·021) kg/day for cow and calf live-weight gain on the tall and short swards respectively). The live-weight gains of the HF and WB cows were similar, but the AF cows gained less weight on the tall sward and lost weight on the short sward. Calf live-weight gain reflected cow milk yield, with the calves from HF and AF cows having similar live weight gains (1·06 and 1·02 kg/day respectively) and those from WB cows having lower gains (0·95 kg/day; P < 0·001). The effect of sward height on calf live-weight gain was greatest in the WB-born calves because of the lower milk yield from WB cows. Body chemical composition changes of cows were predicted from live weight and body condition score, using prediction equations derived from separate groups of cows which were slaughtered at a range of body compositions for determination of chemical composition. Energy balances, calculated from changes in chemical composition, showed the AF cows to have the lowest energy balances with the WB cows the highest. Calculation of energetic efficiency and land use efficiency of weaned calf production taking account of annual food requirements indicated that the HF cows were most efficient, and the WB cows least efficient. The effect of increasing nutritional environment (as represented by sward height treatment) was such as to increase energetic efficiency for all genotypes, but land use efficiency was increased for HF and AF cows, and decreased for WB cows. These results indicate the factors such as size of cows, milk yield potential and pattern of nutrient partitioning can influence energetic land use efficiency of weaned calf production, and that important interactions between genotype and nutritional environment can occur in different measures of efficiency.

A 3-year experiment was carried out to compare systems of bull beef production involving continuous housing or pasture grazing from 5 to 10 months of age and to examine the effects of herbage allowance and concentrate supplementation on lifetime performance and carcass quality. Animals were either set-stocked at pasture to maintain nominal sward heights of 7, 9 and 11 cm or were offered grass silage (700 g digestible organic matter per kg dry matter (DM)) supplemented with 1·5 and 3·0 kg barley-based concentrates (183 g crude protein per kg DM) per head daily. Half of the animals grazed at each sward height were given 1·5 kg concentrates per head daily while the remainder received no supplement. A total of 160 continental X Friesian and 48 Friesian calves which were initially 197 kg live weight were used. From 10 months of age until slaughter at about 17 months all animals were given grass silage ad libitum and supplemented with 3·0 (year 1) or 3·75 (years 2 and 3) kg cereal-based concentrates per head daily.

Animals which grazed the 9- and 11-cm swards produced carcasses of similar weight to those given silage and 3·0 kg concentrates per day, while those grazing the 6·7-cm swards produced carcasses of similar weight to those given silage supplemented with 1·5 kg concentrates. Reducing sward surface height from 11·0 to 9·3 cm did not affect performance but further reductions to 7·9 (year 1) and 6·7 (years 2 and 3) cm reduced live-weight gain by 0·13 and 0·32 kg/day respectively. Concentrate supplementation did not affect the performance of animals grazing swards which were 7·9 cm or taller but increased live-weight gain by 93 and 193 g/kg concentrates for those grazing the 6·7 cm swards and those receiving silage respectively. Differences in live weight at 10 months of age due to the feeding treatments imposed from 5 to 10 months of age were largely retained until slaughter at 17 months as there was little compensatory growth during the residual period. The treatments did not affect carcass composition when the data were adjusted to a constant carcass weight, or meat quality which was satisfactory for all treatments.

Three wilted silages (dry matter concentration of approximately 300 g/kg) were prepared from early-bloom lucerne which received no additive (MG-0), or was treated with a mixture of carboxylic salts (Maxgrass) at either 4 (MG-4) or 8 (MG-8) l/t fresh crop. Silages were stored in tower silos. Resulting silages were offered ad libitum to growing Holstein steers without supplementation. Untreated silage (MG-0) exhibited an extensive, predominantly lactic acid fermentation. The nitrogen (N) fraction was highly soluble, relative to the crop at ensiling. Silage fermentation and protein solublization were restricted by Maxgrass application. Maxgrass application reduced aerobic stability of silage removed from the upper third of silos but not of silage from the lower portion of silos. Apparent digestibility showed a quadratic response to level of Maxgrass application (P < 0·05). Voluntary intake was not affected by Maxgrass addition (P > 0·005) but intake of all silages was high (30 g/kg live weight (LW)). There was a positive linear response (P < 0·05) in LW gain to Maxgrass application with gains of 0·74, 0·86 and 0·87 kg/day being achieved in steers given MG-0, MG-4 and MG-8 silages, respectively. Degradability of silage N determined in nylon bags in situ was unaffected by Maxgrass application. However, the immediately degradable N fraction was reduced by Maxgrass application (linear effect, P < 0·001; quadratic effect, P < 0·05). Benefits in animal performance due to Maxgrass application were attributed to improved N composition while restricted carbohydrate fermentation during ensiling was considered to be of secondary importance.

To examine the effects of body condition and previous nutrition on the herbage intake of ewes grazing swards of different heights in autumn, 96 Scottish Blackface X Border Leicester ewes with a wide range of body condition (score 1·75 to 3·50), were initially housed and given 50 g dry matter (DM) per kg metabolic live weight (M)0·75 per day (treatment L) or 95 g DM per kg M0·75 per day (treatment H) of a pelleted dried grass diet (11·6 MJ metabolizable energy per kg DM) for 6 weeks after weaning in July. The H ewes gained more live weight (9·0 v. 2·7 kg) and body condition score (0·39 v. 0·17) than the L ewes. Half the animals from each treatment were then allocated to each of two ryegrass pastures with a sward height of 5 cm (LS) or 10 cm (HS) for a further 6-week grazing period. During the grazing period there was no significant effect of indoor feeding level on herbage intake, but the L ewes gained more live weight (6·4 v. 5·0 kg) than the H ewes. On the HS, compared with the LS sward, mean herbage intakes were higher (70·0 v. 60·5 g DM per kg M0·75) as were gains in live weight and condition score (7·9 v. 3·4 kg; 0·18 v. 0·0). There were no interactions between the effects of sward height and previous feeding level on herbage intake. Ewes in low body condition (< 2·5) at the start of the grazing period ingested the same amount of herbage on both swards (70·3 g DM per kg M0·75) whereas ewes in high body condition (> 2·5) ingested more (67·0 v. 51·6 g DM per kg M0·75) on the HS compared with the LS sward. The responses of ewes in low and high body condition to different sward heights are discussed in relation to appetite drive and aspects of grazing behaviour.

Fatty acid synthetase and lipoprotein lipase activities, lipid content of adipose tissue and the fatty acid composition of subcutaneous fat, sampled by biopsy at the 13th rib, were measured in 20-week-old rams from lines of Texel-Oxford (TO) and Scottish Blackface (SB) sheep, both divergently selected for carcass lean content. A total of 150 animals were measured, with close to equal numbers of animals per selection line-breed combination.

In both breeds, the high (lean) selection lines had significantly lower backfat depths (TO : 0·5 mm and SB : 0·6 mm, s.e.d. 0·2) than the low (fat) lines. The lipid content of subcutaneous fat was 65 mg lipid per g fat tissue wet weight (s.e.d. 24) greater in TO rams than in SB rams. The TO low line had a higher lipid content than the high selection line (426 v. 448 (s.e.d. 36)) and although the SB selection lines did not differ, the selection line with breed interaction was not significant. SB rams had higher fatty acid synthetase activity (3·1 v. 2·6 (s.e.d. 0·3) on a log scale) but there were no differences between selection lines. Lipoprotein lipase activities were similar between breeds and selection lines. The lower concentration of myristic acid (C14:0) of TO rams compared with SB rams (0·9 (s.e.d. 0·3)) was the only breed or selection line difference which was statistically significant for fatty acid composition of subcutaneous fat.

Lipid content of subcutaneous fat and lipoprotein lipase activity were highly correlated and both were positively correlated with performance test traits, especially with backfat depth. The correlation between backfat depth and fatty acid synthetase activity was not different from zero. Performance test traits, lipid content of subcutaneous fat and lipoprotein lipase activity were positively correlated with the unsaturated fatty acids, with the exception of C18 :1 when correlations were negative.

An investigation was conducted to determine the effects of treatment with the GnRH agonist buserelin on day 12 post mating on the reproductive performance of ewes. There was a non-significant (P > 0·05) increase in nonreturn rate (control 0·76 v. buserelin 0·83) and litter size (control 1·51 v. buserelin 1·77) in three flocks. However, there was a significant (P < 0·05) increase in the number of twin lambs born (control 20 v. buserelin 40) and litter size (control 1·44 v. buserelin 1·68) in the yearling flock. There was no effect of buserelin on oestrous cycle length, although there was a tendency for treated animals to have a longer gestation length and heavier lambs. In a ewe lamb flock there was no effect of buserelin on non-return rate or litter size assessed post slaughter on day 31 of pregnancy. However, ovulation rate tended to be greater in the treated animals, which suggests that buserelin may have induced the formation of accessory corpora lutea. These results indicate that buserelin treatment improves embryo survival and that this effect is particularly evident in yearling ewes.

The influence of food allowance or level of food excess on diet selectivity and intake by sheep given pearl millet stover leaves, and the potential feeding value of the food leftovers (not eaten) (L) were studied. Animals were given food at four levels of L (100, 300, 500 and 700 g dry matter (DM) per day). All sheep received different food allowances (A, g DM per day) and had different L/A and A/M (g DM per kg M) ratios. An additional treatment consisted of feeding the leftovers from the two highest levels of food excess to six rams to have 300 g DM of L per day. A diet supplement was given to provide sufficient rumen degradable protein and sulphur to sustain microbial activity. Variances of organic matter (OM) digestibility (OMD, g/kg) and intake (g/kg M0·75) of both DM (DMI) and digestible OM (DOMI) of the original millet leaves were analysed using L, L/A, A/M and A/M0·75 as independent variables. Variation accounted for was highest when OMD was analysed as a function of L/A (R2 = 0·34) and when DMI was analysed as a function of A/M (R2 = 0·79) or A/M0·75 (R2 = 0·80). The response in OMD to varying L/A was best described by the equation OMD = 457 (s.e. 16) + 157 (s.e. 48) L/A. As L/A or A/M increased, L had a lower concentration of acid-detergent fibre and a higher in sacco OM disappearance. As A/M increased, DOMI and L/A increased following a diminishing return pattern. However, when A/M fell below 31·1 (s.e. 0·9) g DM per kg M, DOMI decreased linearly. No differences (P > 0·33) were observed for OMD between the original food (505 (s.e. 8) g/kg) and the re-fed leftovers (489 (s.e. 15) g/kg), but DOMI was lower with the latter (22•4 (s.e. 0·4) v. 20·3 (s.e. 0·8) g/kg M0˙75, P < 0·03). Results suggest that DOMI of millet stover should be determined at L/A much higher than the traditionally recommended (0·15), and support the hypothesis that farmers could benefit from feeding millet stover at high allowances to animals of high economic value and give the leftovers to less valuable or less selective stock.

The morphological development of the sheep and the goat is different and this difference is manifested from early post-natal life. The main characteristic of kid goat carcasses is their low adipose tissue, and this is considered detrimental to quality. In an attempt to determine the nutritional causes of this, a study was performed with kid goats of the Granadina breed and lambs of the Segureña breed. Six kid goats and six lambs were slaughtered at birth, while a further eight kids and eight lambs were fed a milk replacer to satiety until the 60th day of life and slaughtered on the 61st day. Dry matter (DM) and metabolizable energy (ME) intakes and apparent digestibility of energy were determined in four balance periods between 8 and 60 days of life. From the intakes of ME and comparative slaughter data it was possible to calculate energy retention (ER), heat loss (HL) and energy retained as protein (ERp) and as fat (ERf) for kids and lambs. Kid goats showed a similar apparent digestibility of energy to lambs but had lower DM and ME intakes per kg metabolic body weight (M0·75) than lambs. For kids and lambs respectively these values were: 0·93 and 0·94; 45·4 and 50·1 g/kg M0·75 per day; 937 and 1033 kJ/kg M0·75 per day. Mean values for ER, HL, ERp and ERf rates were: 263, 674, 131 and 132 kJ/kg M0·75 per day for kid goats and, 343, 690, 132 and 211 kJ/kg M0·75 per day for lambs. Together with the different intake, kid goats showed a lower rate of ER and overall, a lower rate of ERf than lambs.

Many pig growth models assume that there is no effect of energy intake and of body weight on the ratio of lipid to protein deposition rate in pigs below their maximal protein deposition rate. An experiment was performed to check whether an effect of body weight and of amount of energy intake on this partitioning of energy is indeed absent when protein deposition is limited by energy intake. Two constant amounts of energy were given above maintenance requirement (12·6 and 16·3 MJ digestible energy (DE) per day for production, treatment L and H, respectively). A total of 52 entire male pigs were slaughtered at 25,45, 65, 85 or 105 kg live weight. Results showed that, for both levels of intake, the ratio of lipid to protein deposition rate increased with increasing body weight. At the L energy intake, the ratio of lipid to protein deposition rate increased from 0·74 at 25 kg to 0·99 at 105 kg body weight. In animals receiving the H treatment, the ratio of lipid to protein deposition rate increased from 0·82 to 1·35 in that weight range. This change in nutrient partition was also reflected in daily gain. Daily gain declined with increasing live weight, a decrease of 150 g/day over the weight range 25 to 105 kg. The 3·7 MJ DE difference in energy intake between treatment H and L resulted in an average overall difference of 105 g daily gain. A control group fed ad libitum showed that protein deposition capacity was above 200 g/day, thus the pigs at the L and H treatment were below their protein deposition capacity. It was concluded that both live weight and energy intake influence the ratio of lipid to protein deposition rate. The mechanism of partitioning between lipid and protein deposition below maximal protein deposition capacity needs further specification in order to improve the predictions of growth models which use the linear-plateau concept.

A 2 X 3 factorial experiment was designed to study the consequences of feeding strategy during rearing and pregnancy over eight parities on sow growth and body condition. Two hundred and fifty-four gilts were group-fed on a restricted scale rising to either 2·25 (L) or 2·70 (H) kg/day (12·5 MJ/kg digestible energy (DE), 193 g/kg crude protein (CP) diet) from 70 to 175 days of age. A total of 156 of the L and H gilts were then given either 1·8 (l), 2·1 (m) or 2·4 (h) kg/day during subsequent pregnancies (12·9 MJ/kg DE; 177 g/kg CP diet). The same diet was offered to a standard scale during lactation. Sows were group-housed in pregnancy and given straw bedding. Losses of sows in rearing and each parity were not associated with treatment. After rearing, data have been presented only for those sows which completed eight parities. At 175 days of age, H gilts had grown faster (P < 0·001). From 175 days to service all gilts were given the same feeding regime but L gilts put on significantly more weight than H gilts, exhibiting more efficient utilization of food. There were no statistically significant differences in weights between L and H sows after the third pregnancy but L sows gained more weight than H sows in most pregnancies. The sows grew in each parity, indicating mature body size was not achieved. The pregnancy regimes had a significant (P < 0·05) effect on live weight, P2 backfat measurement, body length, neck circumference and condition score. Pregnancy treatment h produced the heavier and fatter animals but not all treatment l sows maintained adequate backfat levels for six parities. When housed in groups and given a generous supply of straw, the nutritional requirements of sows to sustain growth and body condition suitable for a long life may be less than has been previously identified for sows housed on concrete and slats without bedding.

Experiments were carried out to establish the suitability of full fat neem seed meal (FFNSM) in broiler and growing rabbit diets. In the broiler experiment, 200-day-old (Babcock) broiler chicks were used in a 10-week trial, with the FFNSM fixed at 0 (control), 25, 50, 75 and 100 g/kg diet. In the rabbit experiment 24 rabbits of three different breeds were used in an 8-week trial, with the FFNSM fixed at 0 (control), 100, 200 and 300 g/kg diet. The criteria of response were food intake, weight gain, food conversion and protein efficiency ratio and mortality. There was a significant (P < 0·05) negative correlation between the dietary inclusion of FFNSM, weight gain and food conversion efficiency of the birds in the starter phase. In the finisher phase from 5 to 10 weeks, food intake, weight gain, food conversion and protein efficiency ratio did not differ significantly (P > 0·05) between the birds on the control diet and diets containing up to 75 g FFNSM per kg. For all the measurements, rabbits on the diet with 100 g FFNSM per kg gave better results than the control. Food intake, weight gain, food conversion efficiency and protein efficiency ratio did not differ significantly (P > 0·05) between rabbits on control diet and the diet containing 200 g FFNSM per kg. Performance on the diet with 300 g FFNSM per kg was poorest.

In a study of the growth of various body parts of the ostrich, only the growth of the head could be described with the Gompertz function. The growth of the ostrich head (y in g) with time (x in months) is described by the Gompertz function y = 613 exp[−ln (613/133) exp(−0·26x)]. This information could be used in the design of carcass classification systems.

The present study was carried out on the pure Bauscat (Bau), pure New Zealand (NZW) and pure Californian (Cal) strains of rabbit. Overall reproductive performance for overdue does of the three breeds was determined and compared with that of does delivering at the normal time. Overdue does of the Bau and NZW breeds had a significantly (P < 0·05) higher annual mean number of pups weaned than overdue Cal does. There was a high incidence of pup mortality in post-mature litters, and the causes of this high mortality were crushing of the skull followed by subsequent stillborn-birth difficulties and intra-uterine death in all three breeds. Obliteration of the anterior fontanelle of pups from post-mature litters occurred in 71%, 75% and 69 % of the deaths diagnosed at birth in the Bau, NZW and Cal breeds, respectively. Induction of parturition with either PGF2α or oxytocin reduced pup mortality in overdue does. The birth-to-remating interval was significantly (P < 0·01) lower in overdue does in which parturition was induced with PGF2∞ but significantly longer when parturition was induced with oxytocin.

Pigs with inbreeding coefficients, ranging from 0·125 to 0·375 were analysed for effect of inbreeding on daily carcass gain, body length and meat proportion in the carcass. The foundation animals were back crosses of a Landrace boar of his daughters which were Yorkshire Landrace hybrids. The statistical model included effect of sex and slaughter weight in addition to the effect of inbreeding. A statistically significant effect of inbreeding on daily carcass gain was found with a linear decline of 1·6 g for 0·1 increase in inbreeding coefficient. There was no effect of inbreeding on body length and meat proportion. Carcass weight had a highly significant effect on body length and daily carcass gain. Effect of sex was statistically significant for meat proportion only.