Mortality, efficiency of food utilization and carcass value of growing pigs were investigated in relation to engineering and control of the house environment. Data originated from contract farms and were made available by the Belgian Farmers' Association. The following parameters were investigated by means of analysis of variance and covariance: food conversion ratio, mortality, emergency slaughter rate and carcass values. Data were classified according to characteristics of the heating, air inlet and air outlet systems of the pig houses.

Within the limitations of our project, the expected favourable effect of heating on mortality and efficiency of food utilization of growing pigs depended on the construction and the functioning of the air inlet and outlet systems. Pigs fattened in houses with mechanical ventilation had a higher proportion of carcasses in the higher carcass grades. Seasonal effects were observed with respect to mortality rate, emergency slaughter rate and efficiency of food utilization. Differences between food conversion ratio with respect to heating and no-heating were comparable with those between summer and winter conditions. Hence the seasonal influence was not completely buffered by the housing conditions.

In the first of two experiments of 6 × 6 Latin-square design a diet of barley, soya bean meal and fish meal, known to give an adequate lysine intake (56 g/day) at the level of feeding adopted, was diluted with maize starch to give crude protein intakes ranging between 448 and 923 g/day but with the lysine intake held constant by using synthetic lysine in the diets. The diets were given to sows suckling ten piglets between days 12 and 30 of lactation. Dietary amino acid adequacy was assessed by changes in plasma urea, urinary urea, urinary nitrogen and plasma amino acid concentrations. The dietary amino acid supply became limiting with a protein intake of approximately 730 g/day. In the second experiment, a diet of similar composition was used with varying additions of synthetic threonine, methionine, isoleucine and tryptophan: the control diet contained all the synthetic amino acids added, the basal diet none and the other diets were formed by adding groups of three out of the four synthetic amino acids. On the basis of some of the variables studied, it was concluded that, for this diet, threonine was the limiting amino acid after lysine.

Four experiments were carried out, with a total of 98 Suffolk-cross lambs fed at a restricted level, to study the effects of skeletal long photoperiod (7 h light: 10 h dark: 1 h light: 6 h dark) compared with short photoperiod (8 h light: 16 h dark) on growth and blood levels of hormones. The experiments started when the lambs were from 2 to 10 months of age and continued for 9 to 14 weeks.

In the first experiment, the weight gains of both females and castrated males were significantly increased by skeletal long photoperiod. Plasma prolactin was increased and cortisol decreased by skeletal long photoperiod.

Experiment 2 included females and castrated males; prolactin was stimulated by skeletal long photoperiod and there was a significant positive correlation between live-weight gain and prolactin.

The weight gains and carcass characteristics of the female lambs used in the third experiment were not affected by photoperiod. Live-weight gain was negatively related to plasma cortisol.

In experiment 4, there were 12 intact males and 12 castrated males. The intact animals grew significantly faster; skeletal long photoperiod caused a depression in testosterone levels in plasma even though it tended to increase live-weight gain.

When the data from all four experiments were pooled, it was found that skeletal long photoperiod gave a significant increase in live-weight gain in animals whose pineal gland was intact (40 per photoperiod; 138 v. 113 g/day); there was no effect on gut fill at slaughter and the increase in carcass weight (0·5 kg) was not significant.

Thirty-three Landrace × Large White multiparous sows were allocated randomly to one of three treatment groups, and were weaned after a 10-day (treatment A), 21-day (treatment B) or 42-day lactation (treatment C). All sows were bled regularly from weaning through to day 24 post coitum, at which time the sows were slaughtered and their reproductive tracts recovered and dissected.

Ovulation rates were similar for all groups. Embryo survival for treatments A, B and C respectively was 0·638, 0·728 and 0·777 but this difference was not significant. Oestradiol 17-β concentrations were significantly higher in sows weaned after 10-day lactations throughout the whole period from weaning to day 10 post coitum compared with the other two treatment groups (P < 0·001).

Growing pigs were given diets based on barley (whole or milled), which was either untreated or sprayed with an aqueous solution of sodium hydroxide (270 g sodium hydroxide per kg water) to give 33·8 g sodium hydroxide per kg dry matter. The barley grain was treated with sodium hydroxide while in the whole state. A total of 48 pigs penned individually were given the diets on a restricted scale of feeding from an initial weight of 31·6 kg until slaughter at 81·7 kg live weight. In a metabolism study, eight boars were subjected to the same experimental treatments in two identical 4 × 4 balanced change-over experiments.

The diet containing untreated milled barley gave significantly faster live-weight gain and lower food conversion ratio than the other three diets (P < 0·001). Food conversion ratios were similar for untreated whole barley and sodium hydroxide-treated barley, whether this was whole or milled. Killingout proportion was similar for untreated and treated milled barley but was significantly lower when the diet contained untreated or treated whole barley.

Milling significantly increased the digestibility of energy and nitrogen. Treatment with sodium hydroxide improved the digestibility of energy in the diet with whole barley but not in the diet with milled barley. With both whole and milled barley, treatment with sodium hydroxide increased the digestibility of crude fibre (P < 0·05) but with ground barley the digestibility and retention of nitrogen were reduced considerably by treatment with sodium hydroxide.

It is concluded that treatment of barley with sodium hydroxide did not improve the nutritive value of either milled or whole grain, that it reduced the digestibility of nitrogen and that it severely depressed the utilization of digested energy for growth.

Age at first parturition in this environment occurs at approximately 18 months. The biggest cause of variation is flock with neither species nor any other source being significant. Parturition intervals for both species are approximatley 10·5 months: flock and season are significant on this variable and there is a decreasing, although non-significant, interval with advancing age. Litter size in goats is 1·25 and in sheep is 1·04, with parity and flock having significant effects for both species, while season also has an effect on goats. Annual reproduction rate is 1·42 kids and 1·19 lambs per breeding female per year.

The efficacy of a single injection of oestradiol benzoate, or a combination of pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG), for the induction of a fertile oestrus and ovulation in the prepubertal pig was investigated in two experiments.

In the first experiment, 1·2 mg of oestradiol benzoate induced 21/23 gilts to ovulate, and 22/23 gilts showed oestrus and were inseminated on day 4 or 5 after treatment. At 28 days after insemination, 12 gilts were pregnant and carrying a mean of 7·1 (s.d. 3·3) live embryos, giving an embryonic survival rate of 0·703. All the 22 gilts treated with 400 international units PMSG plus 200 international units HCG as a single injection ovulated but only 10 showed oestrus and were inseminated. At 28 days after insemination, six gilts were pregnant with a mean of 13·0 (s.d. 5·8) live embryos, giving an embryonic survival rate of 0·583.

In the second experiment, 9/11 oestradiol benzoate and 10/10 PMSG/HCG gilts ovulated in response to treatment. Oestrous detection and insemination were delayed until the expected time of the second oestrus, 20 to 30 days after treatment. Nine gilts (3 oestradiol benzoate, 6 PMSG/HCG) showed oestrus in this period and eight were inseminated. Five gilts were pregnant 28 days after insemination with a mean of 11·4 (s.d. 1·1) live embryos, giving an embryonic survival rate of 0·860.

Two groups of six sows and their litters were observed continuously the day before (day 19 post partum) and the 2 days following (days 20 and 21) movement from individual farrowing crates to multiaccommodation pens. Grouping was associated with a decline in the frequency of true nursing events, particularly in the 6-h period immediately following grouping, and with an increase in the number of false nursing events. There was a trend for a reduction in the duration of the milk let-down phase of the suckling sequence in four litters studied in detail and cross suckling was observed in all four litters. Lactational oestrus occurred in nine of the 12 sows. The study yielded little evidence for an association between nursing and suckling behaviour, and the occurrence of lactational oestrus.

Twenty-four 1-year-old boars of proven fertility were assigned randomly to one of two temperature-controlled trailers. A control group in each trial was held at 17 ± 0·5°C while the other group was exposed to a diurnal ambient temperature cycle. Cycles followed a sine-wave pattern with minimum and maximum temperatures occurring at 04.00 and 16.00 h respectively. Cycling temperature ranges were 17 to 33 ± 0·5°C (low-temperature stress), 19·5 to 35·5 ± 0·5°C (medium-temperature stress), and 22 to 38 ± 0·5°C (high-temperature stress). Semen samples were collected every 3 or 4 days over an experimental period of 42 days.

Low-temperature stress and medium-temperature stress boars were not affected significantly in the five parameters of semen quality observed. The difference between controls and high-temperature stress boars was highly significant for motility, abnormal spermatozoa, gel-free volume, and total spermatozoa per ejaculate. Concentration of spermatozoa was not affected by treatment. Significant time effects were observed for motility, abnormal spermatozoa and total spermotozoa per ejaculate. Significant differences began to appear after 2 or 3 weeks and changes still appeared to be occurring at 6 weeks.

The effect of age on incidence of susceptibility to halothane anaesthesia in pigs was studied on animals that were repeatedly exposed to the anaesthetic. In three trials, 232 Piétrain/Hampshire and 201 Landrace pigs were given three 3-min halothane tests, at 19, 35 and 54 days of age. In a fourth trial 253 Landrace pigs received four 5-min tests, at 21, 35, 49 and 63 days. All pigs were offspring of positive × positive matings. Maximum-likelihood estimates of the probability of positive reactions were 0·47, 0·73 and 0·88 at the three ages in Pietrain/Hampshire; 0·20, 0·63 and 0·60 in the first Landrance trial; and 0·64, 0·86, 0·84 and 0·90 in the second Landrace trial. Thus, in all trials, the incidence of halothane positive reactions increased with age. In both breeds and at all ages, the incidence was lower in males than in females.

Twenty-one pairs of litter sister gilts of similar live weight were selected at 150 days of age and one member of each pair was allocated randomly to the following treatments at approximately 170 days (80 kg live weight): 1. stimulation by mature boar; or 2. an intramuscular injection of oestradiol benzoate. The two groups were fed to appetite and slaughtered at approximately 180 days of age. Examination at slaughter indicated greater ovarian and uterine development in response to oestradiol relative to boar treatment (P < 0·01). The results indicate that oestradiol treatment of gilts followed by post-slaughter examination of the reproductive tract is a sensitive method for evaluating the effects of prior treatments on reproductive development. Significant family and pre-weaning growth effects on reproductive development were also evident on both evaluation methods.

Flemish Giant (FG) and New Zealand White (NZW) purebreds and terminal crossbreds (TX) (Flemish Giant sires × Florida White-New Zealand White dams) were evaluated during a 10-month period for maternal and litter pre-weaning and post-weaning performance. For the doe traits studied, teat number was greatest and litter interval was shortest, while body weight at breeding age (154 days), litter weight at 21 days and day 1 to 21 food intake were lowest for crossbred does. These traits were similar for pure doe groups, with the exception of body weight, for which FG does were heavier. For the preweaning litter traits examined (no. = 101 litters), litter size born was smallest in the TX group (the purebred groups being similar) and was largest at weaning (28 days) for NZW. Proportion of kits born alive was lowest in FG litters, while the NZW and TX groups were comparable. Litter and average birth and weaning weights, litter daily gain, and doe and litter food intake (1 to 28 days) were all highest in FG litters and lowest in TX litters. Repeatability estimates (t) were low (t < 0·05) for litter size and birth weight traits, and were moderate to high (0·18 < t < 0·58) for the remaining maternally influenced characters. For the post-weaning litter traits studied (no. = 86 litters), NZW litters were larger in number and heavier at market age (56 days), and consumed more food from 28 to 56 days than FG and TX litters. Purebred FG litters, however, had heavier average market weights per rabbit, while purebred NZW and TX litters were similar. Mortality due to respiratory disease was higher in FG litters than in NZW and TX litters. Total mortality incidence was lowest in the TX group.

Twelve pregnant sows, 35 to 52 days pregnant initially and 89 to 103 days pregnant at the end of the experiment, were used to study the effect of ambient temperature on metabolic rate. Six sows were group-housed in two groups of three sows per group in one calorimeter and six sows were tethered individually in another calorimeter. Temperatures were changed by 3°C every 3 days in a stepwise fashion from 20 to 8°C and from 8 to 20°C. Sows were given a constant amount of food, which gave 540 kJ metabolic energy per kg live weight0·75 per day and which covered estimated needs that were proportionately 0·20 above maintenance.

Average daily live-weight gain was 531 g for the group-housed sows and 402 g for those housed individually. Heat loss increased below 14°C in group-housed and below 20°C in individually-housed sows. Extra daily thermoregulatory demand was 7·5 kJ/°C in group- and 13·7 kJ/°C in individually-housed sows.

By studying the behaviour of the time series of the difference between the observed values of milk yield and the fitted lactation curve, a stochastic model for milk yield is derived. The model is used to improve the fit of the lactation curve, to forecast milk yield and to generate simulated values of milk yield.

Two experiments, involving 144 and 168 pigs weaned at 22 to 31 days, to investigate the response to inclusion of copper (CuSO4.5H2O), copper plus carbadox/sulphadimidine or copper plus avoparcin supplements in starter and grower diets were made. The carbadox and sulphadimidine levels were 50 and 100 mg/kg diet respectively in both diets. Avoparcin was included at 40 mg/kg in the starter diets and 20 mg/kg in the grower diets. In the first experiment the levels of copper were either 180 or 340 mg/kg in the starter diets and either 90 or 270 mg/kg in the grower diets. In the second experiment the levels were either 20 or 180 mg/kg in the starter diets and either 10 or 180 mg/kg in the grower diets.

In the starter period of the first experiment, supplementation with carbadox/sulphadimidine or avoparcin proportionately increased the rate of growth by 0·41 and 0·07 respectively in relation to supplementation with 340 mg copper per kg diet (P < 0·05). Neither supplement improved growth rate in the grower period. In the second experiment there were no significant differences in growth rate. However the rates of growth in both the starter and grower periods were higher in pigs receiving carbadox/sulphadimidine than in those receiving avoparcin, while these in turn grew slightly faster than those receiving copper only.

Taking into account the costs of the supplements the inclusion of the carbadox/sulphadimidine supplement produced an economic benefit compared with the other treatments.

Six sheep were used in a Latin-square experiment to investigate the effect of pre-harvest treatment of pasture with glyphosate (Roundup, a translocated herbicide) on the palatability of hay. Four hays were used: control (C), Roundup (R), quinine (Q, 100 mg/kg) and Roundup with quinine (QR). During each week one of the following choices was given to each animal: (a) C/C; (b) C/R; (c) R/R; (d) Q/C; (e) Q/R; and (f) C/QR. There were no significant effects of treatment on the proportion chosen or on total daily intake, mean meal size or rate of eating. It was concluded that neither pre-harvest treatment with Roundup nor post-harvest treatment with quinine affected the palatability of hay.

In pigs growing from 20 to 70 kg live weight, the addition of 40 g sodium bentonite to each kg diet was without significant effect on growth performance under ad libitum and restricted feeding regimes. Sodium bentonite appeared to be indigestible and inert, as dry-matter digestibilities were reduced from 0·87 to 0·85 and 0·83 by the addition of 20 and 40 g sodium bentonite per kg diet respectively.

Oestrous activity, ovulation rates and embryo survival rates were investigated in Border Leicester × Scottish Blackface (Greyface) ewes with condition scores of approximately 2·75 (moderately fat) or 3·5 (very fat) at mating. Four of a group of 20 very fat ewes failed to show oestrus at the expected time. Very fat ewes had a higher mean ovulation rate (3·36 v. 2·33; P < 0·05) but a slightly lower potential lambing rate (1·10 v. 1·42 lambs born per ewe put to ram) than the moderately fatewes.

A total of 142 pigs, born at four different times of the year, were slaughtered between 1 and 9 months of age to study the effects of season of birth and sex on heart weight and body weight in the equatorial climate of southern Nigeria.

Analysis of loge heart or body weight showed that season of birth influenced heart and body growth (P < 0·001). The differences occurred largely during the phase of rapid growth, with smaller differences at weaning and at 9 months. Pigs born during the high-rainfall period (May to September) showed stunted body and heart growth during the subsequent dry and warmer seasons. Those born during the dry seasons (November to March), but which passed their rapid-growth phase through the rainy, cooler seasons, were attaining market weights and adult heart weights earlier in life. However, all pigs with early growth reductions recovered, at least partially, later in life. The males had larger hearts at later ages than the females although the differences were not significant (P > 0·05). Allometric regression analyses for heart and body weight showed no seasonal effects but there was a small but significant sex effect (P < 0·001). The males had a smaller intercept and a larger slope when log, heart weight was fitted to log, body weight.

Pigs reared in this equatorial climate appeared to have higher heart weights relative to body weights than those reared in temperate regions. The highest recorded proportional value of 0·0032 is outside the range of 0·0023 to 00028 recorded in temperate regions. This suggests a probable physiological adaptation to increased work load on the heart under warm tropical conditions.

Twelve British Saanen female kids were exposed to male goats for 1 h daily on 29 July (Ml), 12 on 12 August (M2) and 12 on 27 October (M3), when the kids were, on average, (± s.d.) 136·4 (± 12·2), 150·2 (± 12·8) and 225·4 (± 3·5) days of age, respectively. Blood samples were collected to determine plasma progesterone concentrations from 17 July onwards. By 27 October, 11 and 12 kids from treatments Ml and M2 had attained puberty, compared with no kids from treatment M3. Ten kids from treatment M3 attained puberty after male introduction. The mean ages and dates at puberty for treatments Ml, M2 and M3, respectively, were as follows: 205·5, 215·3 and 233·0 days (P < 0·001); and 7 October, 17 October and 3 November (P < 0·001). The mean reaction interval to male introduction for treatments Ml, M2 and M3 was 69, 66 and 7 days (P < 0·001), respectively. The variances for the date of attainment of puberty showed differences in the degree of synchronization of the event between all three treatments.