Lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given diets containing 12 or 20 mg copper per kg dry matter for 13 weeks. Concentrations of liver copper and of copper and aspartate amino-transferase in the plasma were measured regularly, and the concentrations of copper in the kidney, mandible and cheek muscle were also measured terminally. Livers were examined for histological symptoms of copper toxicity.

Wide breed variation was apparent in liver copper concentration after 6 weeks and in plasma aspartate aminotransferase concentration after 9 weeks. At slaughter, total liver copper and kidney copper concentration showed significant breed variation. For all traits, the Texel-cross lambs had the highest concentrations, followed by the Suffolk crosses, and the Blackface had the lowest. The proportion of ingested copper retained in the liver of the Texel-cross lambs was twice that of the Blackface lambs (0·137 v. 0·056), with the other breed crosses intermediate.

There was a significant difference between diets for liver, kidney and mandible copper concentrations, plasma aspartate amino-transferase concentration, and for total liver copper but not for cheek muscle. Both diets produced elevated plasma aspartate amino-transferase concentration and histological symptoms of copper toxicity in the livers of some lambs.

The results show large breed differences in the susceptibility to copper poisoning, some breeds being at risk when given diets containing 12mg copper per kg dry matter for long periods. There was no suggestion that breeds differed in resistance to poisoning other than through different retentions of copper consumed

Measurements of the m. longissimus and overlying fat at the last rib were taken on 39 live entire male pigs using three ultrasonic machines of differing complexity: Sonatest (simple A-mode machine), Scanogram (modified linear scanner) and Danscanner (‘real time’ scanner). Each machine had a different operator and interpreter. The pigs were from two lines of Large White, one selected for efficiency of lean-tissue gain (20 pigs) and the other a genetic control line (19 pigs). They were measured in the week prior to slaughter at approximately 90 kg live weight (91·4 (s.e. 4·4) kg).

The analysis was pooled within line and the precision of carcass lean prediction at constant live weight examined for the three machines. Standard deviation of lean in carcass at equal live weight was 16·2 g/kg.

A single fat thickness measurement taken by the Sonatest gave the most precise prediction (residual s.d. = 12·9 g/kg). Marginally poorer relationships were recorded for a similar measurement taken by the Scanogram (13·5 g/kg) and Danscanner (13·3 g/kg). Precision was not improved from the use of additional fat thickness measurements or, in the case of the scanning machines, from the addition of fat area over the m. longissimus or the area of the muscle itself. The results confirm that the Scanogram and Danscanner do not offer significant advantages over the simpler and cheaper Sonatest in the circumstances considered.

Patterns of oestrous cycle activity in the first breeding season were studied in 30 Suffolk × Mule ewe lambs, Twenty-eight reached puberty and the mean date of first oestrus was 27 November (s.d. 13·6 days). Mean live weight at first oestrus was 37·7 (s.d. 3·63) kg. The mean number of oestrous cycles was 3·3 (s.d. 1·6), 0·92 (65) being normal length single cycles (14 to 19 days), 0·03 (2) long single cycles (20 to 26 days) and 0·05 (4) multiple cycles (> 26 days).

Plasma progesterone profiles before and after the breeding season were studied in 10 randomly selected animals. All showed profiles suggesting one or two silent ovulations preceding the first oestrus but none showed any indication of silent ovulations following the last oestrus.

Plasma progesterone profiles were also studied on the four animals showing multiple cycles and on the two animals that did not reach puberty. These suggested that, in all four animals showing multiple cycles, one or two silent ovulations had occurred between the two overt oestrous periods. Of the two animals that did not reach puberty, one showed three abnormal silent cycles and the other showed no change in progesterone concentration from a low basal level.

Sixty-six Landrace × (Landrace × Large White) gilts were allocated at 70 days of age to one of three rearing treatments of housing with gilts, contemporary castrated males or contemporary intact males. Half the experiment was completed in winter and half in spring. At 159 days of age all gilts were subjected to a change of pen and, from 160 days of age, daily exposure to mature vasectomized boars. The rearing treatments had a small but significant effect on the time interval from boar exposure to puberty, with gilts housed with gilts averaging 8·9 days to puberty compared with 7·1 days and 7·4 days for gilts housed with castrates and boars, respectively (p < 0·05). In addition, there was a seasonal effect on the time interval to puberty. Gilts receiving mature boar exposure during the winter months had a longer interval to puberty than gilts exposed to boars during the spring (8·8 days v. 6·9 days; P < 0·01). These results indicated no habituation effects of gilts housed with contemporary males but, rather, the possibility of a slightly earlier induction of puberty.

1. Four experiments were performed to study the effects on the growth of lambs of extending natural daylength to 20 h with dim artificial light, under management conditions similar to those on commercial farms.

2. Thirty-six female lambs aged 6 months were given a concentrate ration at a restricted level in groups of nine; there was significantly faster live-weight gain in the two groups that received extra light but no effect on carcass weight or linear measurements.

3. Forty-eight castrated male lambs were fed either ad libitum or at a restricted level on a concentrate diet; half were given additional light. Feeding ad libitum gave faster growth than restricted feeding but there were no significant effects of daylength.

4. One hundred and fourteen lambs of mixed sex were offered silage ad libitum plus one of three concentrate supplements at an average of 0·25 kg per head per day. Half were exposed to 20·h daylength from mid-October until slaughter in mid-January. There were no effects of light treatment on growth or carcass weights.

5. The fourth experiment was a repeat of the third and again there were no effects of extended daylength.

6. It is concluded that this method of controlling daylength is not appropriate for commercial use.

Forty-four single- and twin-born New Zealand Corriedale two-tooth ewes and rams aged 14 months were fed individually, in pens, a pelleted ration adjusted to maintain body weight after allowing for wool growth. The sheep were fed for a 3-month settling period, followed by a 3-month experimental period, during which wool growth, fibre diameter, fibre length and net efficiency of wool growth were measured.

Since the wool-growth cycles of the two sexes were found to be out of phase, a valid comparison of the sex data was not possible. Such phase differences may be important in some experimental designs. Significant sex by birth status interactions were identified for all wool production parameters except fibre length, confirming that care must be taken in assigning correction factors during selection of rams and ewes. The general trend was for single-born ewes to produce more and coarser wool more efficiently than twin-born ewes, while the differences between single- and twin-born rams were much smaller. Single-born animals were heavier than twin-born (P<0·01).

Individual values for wool growth and net efficiency varied by a factor of three within sex groups, indicating a considerable scope for selection

An experiment has been carried out at Bahia Blanca to estimate the trend in ovulation rate throughout the year shown by Corriedale ewes of similar live weight in the south-west district of the Argentinian pampa.

Five groups of 16 animals were each subjected to two 20-day observation periods and the 10 observation periods in the experiment were evenly spaced within a year.

The proportion of ewes showing oestrus and ovulation (OO), the frequency of twin ovulations (TO) and, hence, ovulation rate (OR) were estimated for each period by using vasectomized rams and performing laparatomies.

A significant and periodic relationship was found between each trait and the number of days elapsed from the longest day (×). In turn, changes in the values of ×, arising from the progress of the experiment, were to some extent associated with changes in nutrition and surgical interference. However, it was concluded that these factors could not have affected the similar and remarkable seasonality shown by each trait in this study, and that this seasonality was mainly associated with differences in the natural light regime to which the ewes were exposed before and during their corresponding observation periods.

The predicted maximum values for each parameter were reached 1 month before the shortest day. Prior to and after this date both OO and TO declined, so that the predicted OR values became zero for a period of approximately 2 months before the longest day

1. Three isocaloric diets containing 170, 210 or 231 g crude protein per kg were given at two levels, and offered ad libitum to entire and castrated male pigs growing from 20 to 70 kg live weight.

2. Between 20 and 45 kg, growth rate improved with each increase in level of feeding (P < 005) and, on the ad libitum treatment the food intake and growth performance of both entire and castrated pigs were similar. On the restricted feeding treatments the growth performance of entire, but not of castrated pigs, improved when dietary protein was raised from 170 to 210g/kg (P < 005).

3. During the live-weight periods 45 to 70 and 20 to 70kg, raising food intake improved growth rate (P < 005) but increased the food conversion ratio and carcass fat measurements at 70 kg (P < 0·05). However, food conversion ratio and the majority of carcass characteristics of entire pigs fed ad libitum were equivalent to those of castrated pigs fed at the lowest level.

4. Dietary protein level had no significant effect on growth performance from 20 to 70 kg or on carcass fat measurements at the latter weight. However, each increase in dietary protein in the live-weight period 45 to 70 kg depressed the performance of castrated pigs (P < 0·05) while that of entire pigs was reduced when the protein level of the diet was raised from 210 to 231 g/kg.

The lysine requirement of the lactating sow was examined in two Latin-square experiments using multiparous sows, in mid lactation, each of which suckled a litter of 10 piglets. The lysine requirement was examined by the addition of supplementary synthetic lysine to a basal diet deficient in lysine, to give dietary lysine levels of 6·4 to 17·2g/kg dry matter. The adequacy of the lysine supply was judged by the responses of plasma lysine, plasma and urea-nitrogen, urinary urea-nitrogen and milk composition. Intersecting linear regression lines were fitted to the treatment means. The responses of urinary urea-nitrogen, in the two experiments, indicated that the lactating sow required approximately 48·5 g dietary lysine per day while the response of plasma lysine indicated a requirement of approximately 51 g lysine per day. Plasma urea and milk composition were less useful as indicators of the nutritional adequacy than were urinary urea-nitrogen and plasma lysine.

1. Two diets, containing either 400 g oat husks (OH) or 300 g straw (ST) per kg, given ad libitum during a 7-week lactation, were compared with a conventional control diet (C) given in restricted amounts. Eight sows per treatment were used in a randomized-block experiment.

2. Mean daily intakes of dry matter during lactation were 4·87, 7·79 and 5·80 kg for the C, OH and ST diets respectively (P>0·001).

3. There were no significant differences between diets in number or weights of piglets per litter either at 21 days of age or at weaning.

4. Mean changes in live weight during lactation were –9·8, +5 1 and –16·8kg for sows on the C, OH and ST diets respectively (P<0·01). Sows that gained weight during lactation tended to lose more in the 7 days following weaning.

5. There were no significant differences in either milk yield or composition. However, the fat content of milk tended to be higher for sows given the two fibrous diets.

6. Mean apparent digestibility coefficients for dietary dry matter were 0·82, 0·63 and 0·59, and for nitrogen were 0·81, 0·75 and 0·63, in the C, OH and ST diets respectively. The rate of passage of the ST diet through the gut was significantly faster than that of the other two diets (P>0·001), which were similar.

Forty-two piglets were used to study the effects of heavy and light birth weight, and of four levels of feeding, ranging from 37 to 91 g dry matter per kg M0 75 per day, on growth between 5 days of age and 6·5kg live weight, and on body composition, and the cellularity of muscle and subcutaneous adipose tissue, at the latter weight. The effects of birth weight and level of feeding to 6·5 kg on performance between 6·5 and 11 -5 kg, and on body composition at 11·5 kg, were also investigated.

Light birth weight piglets grew more slowly to 6·5 kg than those of heavy birth weight (P < 0·05). However, birth weight had no effect on food conversion efficiency or on body composition.

Each increment in feeding level resulted in increases in growth rate (P < 0·01), body fat content (P < 0·01) and average fat-cell diameter (P < 0·01) at 6·5 kg, but in decreases in body protein and water (P < 0·01).

The weight of the m. semitendinosus at 6·5 kg was unaffected by either birth weight or level of feeding. However, the deoxyribonucleic acid content of the muscle at both 6·5 and 11·5 kg was less in light birth weight piglets fed at the lowest level prior to 6·5 kg (P < 0·05). These piglets also exhibited poorer growth performance subsequent to 6·5 kg than their heavier birth weight counterparts.

Nevertheless, piglets of both light and heavy birth weight, fed at the lowest level to 6·5 kg, grew faster and more effficiently between 6·5 and 11·5kg (P < 0·05), and were leaner at 11·5kg than those previously fed at the highest level (P < 0·01). Average fat-cell diameter at 11·5kg was also less in pigs fed at the lowest level prior to 6·5kg (P < 0·01). Total deoxyribonucleic acid in subcutaneous adipose tissue at 11·5kg was unaffected by either birth weight or level of feeding prior to 6·5 kg.

At the beginning of the autumn breeding season, six Rambouillet ewes were treated with intravaginal pessaries containing 20 mg flurogestone acetate on day 10 (oestrus = day 0) of an oestrous cycle. Sponges were removed after 12 days. Five additional ewes served as untreated controls. Vasectomized rams were used twice daily to detect oestrus and blood samples were collected daily from day 1 until 3 days following the post-treatment oestrus. Animals were slaughtered and reproductive tracts were recovered 3 days after the oestrus followingpessary removal. Epithelial, endometrial and glandular measurements were recorded from sections of oviduct, uterus and cervix using a refrigerated microtome. Serum progesterone was quantified by radioimmunoassay. Intravaginal progestagen treatment prevented ewes from exhibiting oestrus during the period in which pessaries were in place. Oestrus was observed, however, in all treated animals within 2 days of sponge removal, resulting in a mean cycle length (±.e.) of 23·2 (±0·2) days compared with 17·6 (±0·2) days (P<0·01) for controls. Serum progesterone profiles in treated and control animals indicated that corpora lutea regression progressed normally in ewes receiving the exogenous progestagen. Neither reproductive tract weight, ovarian weight, ovulation rate nor follicle number differed between groups (P>0·10). Oviductal, uterine, uterine glandular and cervical epithelial cell heights, as well as uterine glandular proliferation and endometrial thickness, were also similar in treated and control ewes (P>0·10). These data suggest that intravaginal flurogestone acetate does not appreciably alter histology of the reproductive tract during the time in which the fertilized ova would enter the uterus. Overt histological changes, therefore, are not likely to be a significant cause of reduced fertility at a synchronized oestrus.

The proportion of ewes lambing of those exposed to the ram, litter size and weight at lambing, and at weaning, pre-weaning lamb mortality and changes in ewe weight during suckling, were studied in 326 ewes (931 lambings) representing two pure breeds, Oxford and Suffolk, and four crossbreds, Oxford♂ × Suffolk♀, Suffolk♂ × Oxford♀, North Country Cheviot♂ × Oxford♀ and Cheviot♂ × Suffolk♀, mated to purebred and crossbred rams during 9 years. The proportional fertility in the Oxford and Suffolk ewes (0·82 and 0·85 respectively) was lower than that of Suffolk × Oxford (0·93), Oxford × Suffolk (0·94), Cheviot × Oxford (0·88) and Cheviot × Suffolk (0·88) ewes. Litter sizes of Suffolk ewes at birth and at weaning were 1·6 and 1·3 lambs, 0·3 (0·22) and 0·3 (0·27) lambs largeir than those of the Oxford ewes, respectively. The corresponding figures for litter weight were 1·29 kg (0·22) and 11·8 kg (0·36). Oxford ewes lost 0·10 of their weight during nursing compared with 0·14 for the Suffolk and the two reciprocal crosses. The estimates of heterosis in litter size and litter weight at birth were 0·085 and 0·082, and at weaning were 0·13 and 0·18 respectively.

The results showed that Oxford crosses were better in performance than the pure Oxford, whereas the Suffolk crosses were similar in performance to the pure Suffolk, except in the proportion of ewes lambing of those exposed and pre-weaning mortality, in which the crosses were 0·07 and 0·20 superior to the pure Suffolk, respectively.

Breed of sire had a significant effect on litter weight at birth and at weaning, whereas the interaction breed of sire × breed of dam was a significant source of variation on litter size and litter weight at birth and at weaning. Litter performance at birth was significantly lower in 2-year-old ewes and in ewes sired by 3-year-old or older rams than in other age groups

Four groups of 10 gilts were reared from an early age under four social conditions. The mating rate (the number of successful copulations as a proportion of oestruses) at the pubertal oestrus of gilts reared in isolation from boars was significantly lower than that of gilts reared near mature boars (P> 0·01). In addition, gilts isolated from boars during rearing had a significantly longer interval from the first mounting attempt by the boar until the display of the standing response (P<0·05) and a significantly higher proportion of these gilts were restless during copulation and terminated the copulation in comparison with gilts reared near mature boars (P<0·01). All gilts were ovariectomized after puberty or at 35 weeks of age and, following a standard oestrogen treatment, they were induced into a series of behavioural oestruses. There were no significant differences between the treatments in the mating rate at these oestruses. It is concluded that the social environment during rearing will influence the mating rate of the gilt at the pubertal oestrus.

Ten littermate pairs were used to study the effects of light and heavy birth weight on the development of muscle tissue, growth rate, body composition and the estimated milk consumption of piglets reared on the sow to 6·5 kg live weight.

Neither average daily gain to 6·5 kg nor body composition at the latter weight were significantly affected by birth weight. Birth weight also had no effect on the weight or deoxyribonucleic acid content of the semitendinosus musde at 6·5kg. However, pigs of hght birth weight -were lighter at 2\ days of age (P < 0·01) and older at 65 kg (P < 0·01) than those of heavy birth weight.

Pigs of heavy birth weight consumed more milk per suckle than their lighter birth weight littermates (P < 0·01). However, the relative milk consumption (g/kg live weight) of both groups was similar.

Sixty-four pigs were given diets containing lactose or starch as the major source of carbohydrate in two separate experiments conducted between 7 and 28 days of age.

In the first experiment, pigs were offered lactose, wheat starch, wheat or extruded wheat. Performance over the whole experimental period, of pigs given lactose or wheat, was similar, but greater than that of pigs given wheat starch. Apparent digestion of wheat diets was less than that of the other diets. In the second experiment, performance of pigs given lactose or wheat was also similar over the whole experiment. However, between 7 and 14 days of age in both experiments, weight gains and food conversion ratios of pigs given wheat were less than those of pigs given lactose.

The activity of maltase and amylase in the intestinal mucosa, and amylase in the pancreas, increased between 7 and 28 days of age. The maltase and amylase activity in the intestinal mucosa and pancreas of the pigs given wheat was greater than that of the pigs given lactose, while the activity of lactase in the intestinal mucosa was greater in the pigs given diets containing lactose than in those pigs given wheat.

In a third experiment, it was found that most of the hydrolysis and absorption of starch occurred in the duodenum and jejunum of the pigs, and had been completed before the ileum.

Thirty entire male piglets weaned at 21 days of age were used to study the effects of two levels of dietary protein (178 and 194g/kg), each in combination with five levels of supplemental lysine (0, 1·5, 3·0, 4·5 and 6·0g/kg), in diets given ad libitum and containing 14 MJ digestible energy per kg, on performance from 6 to 20 kg live weight.

Raising total lysine from 7·2 to 8·7 g/kg diet with 178 g crude protein per kg promoted significant increases in average daily gain, efficiency of food conversion and voluntary food intake, and raised all these parameters to levels exhibited by piglets receiving the basal diet containing 194 g crude protein per kg (8·7 g total lysine per kg).

Lysine supplementation of the diet containing 194g crude protein per kg had no effect on growth performance or food intake.

Carcass characteristics at 20 kg live weight were not significantly affected by either dietary crude protein or total lysine (P> 005).

Two studies were conducted at commercial farms on a total of 1117 sows to investigate the role of social environment on the weaning to mating interval of the sow. In one of the two studies, group housing and intense boar stimulation, achieved by daily introduction to a boar, were associated with significant reductions in the weaning to mating interval of the sow (P<0·05 and P<0·01, respectively): these two factors together produced increases of 0·18 and 0·22 in the proportion of sows mated within 10 and 28 days of weaning, respectively. In addition, parity and temperature during the week of weaning were significantly associated with the weaning to mating interval in both studies (P< 0·005 and P<005, respectively). It is concluded that the post-weaning social environment will influence the onset of oestrus in the sow.

1. An experiment was carried out to describe growth rate, efficiency and thermal balance of pigs accommodated in three different housing conditions during summer in southern Australia.

2. Housed pigs grew at a similar rate to those in an outside pen with a wallow and shelter (418g/day compared with 404g/day respectively; P > 0·05), and both groups utilized food with similar efficiency (food conversion ratios of 3·07 and 3·14 respectively; P > 005). A group accommodated in an outside pen with a wallow but no shelter grew at a significantly slower rate (347g/day; Z <001) with a lower efficiency of food conversion (3·35; P < 005) than either of the other two groups. At slaughter, pigs housed outside without shelter showed a significantly higher dressing proportion (0·749; P < 005) and had less backfat (11·6mm; P < 0·05) than the inside group (0·723 and 13·4mm respectively).

3. Estimated heat storages at 12.00 h of pigs housed inside and outside without shelter were respectively, and approximately, 50 and 18·5 × greater than in those pigs housed outside with shelter.

1. The objective was to determine to what extent pigs can make use of energy yielded by fermentation of cellulose in the hindgut.

2. Two groups of 12 pigs were grown from 20 to 80 kg live weight on diets based on barley and soya bean meal. In treatment 1 energy intakes were restricted to approximately 085 of that required for maximum growth rate but intakes of other nutrients were adequate. Treatment 2 provided the same intake of all nutrients as treatment 1, but cellulose (‘Solka-floc’) was given in addition at a level of 150 g/kg food intake.

3. There were no significant differences between treatments in average daily gain or carcass linear measurements but dressing proportion was lower with added cellulose.

4. At 35 and 65 kg live weight, apparent digestibility of fibre and energy was measured in 5-day periods on each pig. The weight of the fibre digested in treatment 2 was considerably higher than for treatment 1; the digestibility of added neutral-detergent fibre was 0·40. However, the quantity of energy apparently absorbed was the same for both treatments. In treatment 2, either none of the energy released from digestion of added cellulose was absorbed or, if any was absorbed, it was offset by reduced absorption of energy from other sources.