1. The digestible energy content of 14 meat meals and meat and bone meals produced from different regions in eastern Australia was determined using growing pigs. The relationship between digestible energy content and chemical constituents in the meals was investigated.

2. Digestible energy ranged from 9·4 to 13·9MJ/kg (air-dry basis). This variation in digestible energy was best described by the regression equation:

3. Simpler equations, with only gross energy or crude protein and ether extract were:

4. Digestibility of the energy and crude protein in the meals ranged from 0·63 to 0·77 and 0·73 to 0·91 respectively. These variations were not related to any of the major chemical constituents of the meals.

Twenty-four prenatal (15 female), and 15 postnatal female Romney sheep, comprising a weight range from 3g to 60 kg, were dissected into their major carcass tissues. Adipose tissue was not dissectable from foetuses aged less than 80 days. The growth rates of the dissected adipose tissues and their chemical components, deoxyribonucleic acid, protein, and total lipid subdivided into phospholipid, cholesterol and triglyceride, were compared relative to the growth of the total carcass wet weight. Total side (half-carcass) adipose tissue grew at a rate substantially greater than total carcass weight. The subcutaneous adipose tissue of the forequarter grew at the fastest rate while that from the shoulder, sternum and internal cavity of the forequarter grew slowest, at rates which were not significantly different from that of the carcass. Of the chemical components, triglyceride and cholesterol grew at the fastest rate, deoxyribonucleic acid grew at the slowest rate, and phospholipid and protein grew at intermediate rates; all grew faster than the carcass. Predictions were made of the distribution of triglyceride in the carcass of the sheep at different stages of growth.

The effects of different husbandry systems on production characters of 616 purebred and crossbred sheep are reported. The Cyprus Fat-tailed (L), Chios (C) and Awassi (A) breeds were evaluated under intensive, semi-intensive and extensive production systems. The performance of crossbred (C × L, A × L and A × C) Cyprus Fat-tailed and Awassi sheep was compared under extensive husbandry conditions. Ewes on the intensive systems produced more milk, fat and protein (P<0·01), but with somewhat lower fat and protein content than those on the extensive or semi-intensive systems. Chios and Awassi ewes were superior to Cyprus Fat-tailed ewes in nearly all traits (P<0·1), but inferior in terms of fat and protein content (P<0·1). Awassi × Chios crossbreds outyielded both purebred and crossbred sheep in terms of milk, fat and protein yield (P<0·1). Lactation number had a significant effect on milk traits. Maximum milk production was obtained at fourth lactation.

Four diets which varied in crude protein concentration from 140 to 240 g crude protein per kg dry matter were given to gilts in experiment 1, and two diets containing 140 and 200 g crude protein per kg dry matter were given t o boars and barrows in experiment 2. Two levels of feeding were offered in both experiments and energy and nitrogen balances were measured at 30 and 90 kg live weight in both experiments, and also at 50 kg in experiment 1. Nitrogen intake had a small negative influence on energy retention by pigs of all sexes, an effect which was independent of the large positive effect of metabolizable energy intake. The ratio of metabolizable energy concentration to digestible energy concentration decreased in association with increases in crude protein concentration of the diets. The results show that comparisons of feeds on the basis of their digestible energy concentrations would lead to overestimation of the energy values of those containing high protein concentrations. Live weight (or age) and metabolizable energy intake exerted positive influences on the amount of energy retained per kg live-weight gain, whereas nitrogen intake exerted a negative influence. Values for energy retained per kg live-weight gain predicted from multiple regression equations, together with calculated values for maintenance and net efficiency, were used to predict the energy retention and growth rate of pigs in various circumstances.

Nitrogen retention increased in association with increases in nitrogen intake for pigs of all sexes at 30 kg live weight; there was also a corresponding increase for boars at 90kg live weight, but not for gilts or barrows at this weight. Boars retained more nitrogen than did barrows at 30 and 90 kg live weight only if given the diet with the higher concentration of protein.

Metabolizable energy intake appeared to exert a small positive influence on the nitrogen retention by pigs of all sexes at 90kg live weight; however, it appeared to have no influence on nitrogen retention by pigs at 30kg live weight.

The diameter of adipocytes from subcutaneous, intermuscular and internal cavity fat depots of 5 pre- and 14 postnatal Romney female sheep was measured, the volume calculated, and the number per depot computed from the weight of triglyceride in the depots.

The rates of increase of adipocyte volume relative to the increase in weight of total side adipose tissue, and of the fat depots and their chemical components, were calculated using linear regression analyses of the natural logarithmic transformed data. These logarithmic regression equations were used to estimate the volume of adipocytes in sheep at different stages of development. The total numbers of adipocytes at each stage of growth were estimated using linear double logarithmic regressions of adipocyte number on carcass weight.

The growth of total adipose tissue and of each of the fat depots occurred mainly by an increase in the adipocyte volume, which increased over 70-fold from 120 days gestation to 5 years of age. The increase in adipocyte volume during growth occurred at similar rates in all of the fat depots and no significant differences between the volumes of adipocytes from the fat depots were found within sheep of similar carcass weight. During the same growth period the total number of adipocytes increased about 6-fold. Differences in the relative rates of growth of the fat depots were attributed to cellular multiplication rather than to cellular enlargement.

Sixty crossbred female and male castrate pigs were randomly allocated to five treatments in which 0, 20, 40, 60 and 80% of the ground maize in grower and finisher diets was replaced by triticale on an equal weight basis.

Pigs receiving the basal maize growing diet (0% tritcale) gained less than pigs fed the triticale diets (P<0·05). Pigs given the diets in which 20% of the maize was replaced by triticale gained significantly more than those given the other diets (P<0·05). Increasing replacement in the grower diets beyond 20% resulted in a linear decrease in consumption and weight gains (P<0·05). Feed conversion was similar for all diets which contained triticale.

The basal finisher diet, and the diet with 20% of the maize replaced, promoted better feed consumption and weight gain than the diets in which 40, 60 and 80% of the maize was replaced by triticale during the finishing phase and for the entire 109-day growing-finishing period. Carcass quality grade was higher for pigs fed the basal diet and the diet in which 20% of the maize was replaced by triticale (P<0·05 ) but there were no differences in the other parameters of carcass quality, nor in the composition, cooking quality and organoleptics,. of the longissimus muscle. Fatty acid profiles of the longissimus muscle indicated that palmitic and oleic acids were significantly higher (P<0·05 ) and linoleic and palmitoleic significantly lower (P<;0·05) in pigs given the basal and 20% replacement diets than in pigs given the other diets. The results show that triticale could replace maize partially (up to 20%) in diets for pigs.

Attainment of puberty and the ovulation rates for the first three oestrous cycles were studied in gilts reared to 160 days alongside contemporary castrate or entire males before introducing them to mature boars.

Gilts which were introduced to the boars at 160 days of age reached puberty at younger ages and lighter weights than isolated gilts. Rearing treatment did not affect the age of puberty. Gilts which were isolated from boars after 160 days of age reached puberty earlier if they had been reared with entire rather than castrate contemporary males. The interval from introduction of the boars to first oestrus was related to age and weight at the time of introduction.

Ovulation rate at the pubertal oestrus was the same in both isolated groups, and higher in both these groups than for gilts induced into early puberty by boars. Ovulation rate increased at the second and third oestrous cycle and groups differed only at the first oestrus. In a second experiment, the reproductive performance of gilts approximately 218 days of age experiencing either their first, second or third oestrus was studied. No differences were found among the groups and the conclusion is that in gilts of similar age and weight the oestrous cycle at which mating takes place does not affect reproductive performance.

One hundred and eight crossbred sows from nine different commercial sources were monitored over two parities for changes in live weight and fatness. All sows were given a common nutritional regime. Thirty sows were slaughtered and physically dissected. After weaning the second litter, mean carcass measurements ( ± s.d.) were: live weight, 139±9·5kg; lean mass, 26·6 ± 2·8kg; subcutaneous fat mass, 4·l ± l·7kg; ultrasonic P2 backfat depth (USP2), 11·3±2·8mm; total dissected fat (kg) = 0·63 ± 0·073 USP2 —1·1 ±0·85(r = 0·85). Between mating (parity 1) and weaning (parity 2) sows gained 22kg live weight and lost 6·8mm backfat. There were significant differences between sources with respect to fatness, despite standardized feeding. It is suggested that for breeding pigs such as these, starting their reproductive life with limited fat reserves (16·4 ± 3·0mm USP2 at 92 ± 6kg live weight), a conventional fat-exploiting feeding regime is unlikely to be appropriate.

Fifty-one ewes with single lambs and 87 ewes suckling twin lambs (mean ewe live weight, 67 kg) were given a basal diet of 1·0kg hay and 1·0kg whole oats, providing approximately 16·7MJ metabolizable energy and lOOg digestible crude protein per day. Three supplements (A, B and C), providing an additional 45 g digestible crude protein, were compared. Supplement A consisted of 40 g of a fully-soluble liquid product (LS) containing urea, (equivalent to 1090g crude protein per kg), minerals and vitamins; B was 16g urea with solid minerals and vitamins; and C was 125g soya bean meal given in substitution for the same amount of whole oats plus solid minerals and vitamins. The growth rate to 6 weeks for single lambs (11 kg) was unaffected by treatment. For twin lambs the growth rates were 7·5kg (LS), 7·1kg (crystalline urea), 7·8kg (soya) and 6·4k g (unsupplemented) (s.e. of mean = 0·31 kg). Ewes with twin lambs given crystalline urea or LS lost more live weight (approximately 1·04kg) than those given soya (6·6kg) over the first 6 weeks of lactation. The maintenance of normal concentrations of calcium and phosphorus in the blood of ewes suggested that the low total intakes of approximately 4·1 g calcium and 4·7 g phosphorus by the ewes were not inadequate.

The value of a selection index for 8-week litter weight as a trait of the ewe, combining information on the ewe and on five classes of female relatives, was considered. Adding records on the dam and on paternal half sibs to those of the ewe gives increases of 10 to 50% in the rates of genetic response. The index can be simplified with little loss in efficiency by weighting all records equally for relatives with 1, 2 or more records within each class of relative. In selecting breeding replacements, information on the parents of the sire of the individual being selected may increase the rates of response by a further 20 to 30 %.

The lipolytic activity of porcine lipid mobilizing factor, a pituitary peptide, was potentiated by porcine serum when measured in a rabbit fat-cell suspension. The potentiation caused by sera from 54 individual pigs which had been bred using backfat thickness and growth rate as selection criteria was examined. No significant correlation was found between the potentiation and either of these parameters.

The influence of the odoriferous androstene steroids upon the response and courtship behaviour of gilts has been studied. These steroids are normally present in the submaxillary salivary glands of the boar, and have been shown previously to be an aid in the artificial insemination of gilts. Glands were excised from young boars after weaning, and at 6 months of age the ability of the boars to elicit a standing response from oestrous gilts was compared with that of littermate controls. In addition, a detailed record was made of behavioural activities performed by both gilts and boars, under a standard test procedure.

Analysis of the data showed that the presence of the glands was essential for normal behavioural patterns in both the females and the males. When confronted with a treated boar, the gilts were affected in three ways: approaching oestrus, they did not respond as early as they did to the controls; the intensity of their response was reduced; and it was held for a shorter period. The demeanour of the treated males was passive and unconcerned, i n contrast to the easily-aroused aggressive nature of the controls. The characteristic viscous salivary secretion was absent, and the scrotal sac was less pronounced and supported closer to the body.

These results suggest that elimination of the white, frothy saliva normally containing and dispersing the androstene steroids not only reduces the boar's ability to command and elicit a full sexual response from oestrous gilts, but it also reduces his own libido. In conjunction with previous work, these studies provide evidence for the pheromonal properties of androstenone and androstenol.

Records were available for the progeny of Dorset Down, Oxford, Suffolk, Ile-de-France, Oldenburg and Texel sires out of Border Leicester × Blackface and Animal Breeding Research Organisation Dam Line × Blackface ewes. The data analysed were: (a) growth traits to 12 weeks for 2585 lambs, the progeny of 102 sires; (b) growth traits for slaughter at fixed weights of 35kg and 40kg for 1884 lambs (79 sires); and (c) half carcass dissection traits for 956 lambs (65 sires).

Oxford and Suffolk cross lambs were heaviest at all ages and thus youngest at slaughter. Texel cross lambs grew slowly to 12 weeks but were not significantly older than Dorset Down, Ile-de-France and Oldenburg cross lambs at slaughter. The Texel cross produced the leanest carcass with a high lean/bone ratio and eye-muscle area. Dorset Down and Ile-de-France cross lambs were fattest at slaughter but had high values for lean/bone ratio and eye-muscle area. Interactions between breed of sire and slaughter weight were non-significant for all traits (P>0·05).

Breed differences in carcass composition were also compared statistically as if at a constant percentage of subcutaneous fat. The differences were not so great as at constant live weight but the Texel cross would have had the leanest carcass. Side weights would be heaviest in the Texel and lowest in the Dorset Down and Ile-de-France. Oxford, Suffolk and Dorset Down cross lambs would be youngest at slaughter and Texel and Oldenburg crosses oldest.

The milk intake of two litters of suckling piglets was measured by the turnover of tritium-labelled body water. The estimated intakes of a litter of seven piglets agree with the current knowledge of milk yield from sows, which generally rises to a maximum at the 3rd week and then declines. With a litter of four, intake rose continuously from the 1st to the 6th week. Since piglets are often weaned at 3 weeks of age, this method has few disadvantages n i practical use. During the estimation of water turnover the total body water of individual piglets can also be obtained so that information on body composition (solids, protein, fat and ash) can be derived. The efficiency of conversion of milk by piglets can thus be calculated.

Seventy-two Large White × (Large White × Landrace) weaner pigs in each of three experiments were scale-fed diets containing 850 g barley per kg which had been processed by either cold rolling (R) or grinding through 1-56 mm (O) or 468 mm (T) screens. In experiments 1 and 2 barley (0-868 dry matter) was used and group feeding was practised for 55 and 100 days respectively. In experiment 3 barley (0-838 dry matter) was used and individual feeding was practised for 107 days. In experiment 1 gastric pH was recorded at slaughter. In all experiments the stomachs of all pigs were examined for gross and histological abnormalities.

In experiments 1 and 2 growth rates and efficiencies of feed conversion were not significantly different for pigs fed the R-, O- and T-based diets. In experiment 1 the pH in the pylorus, but not in the fundus, was significantly higher in pigs fed the O-diet compared with the T-diet, and on the T-diet compared with the R-diet. Growth rates and efficiencies of feed conversion in experiment 3 were significantly poorer in pigs fed the R-diet compared with the T-diet, and on the T-diet compared with the O-diet. In experiment 1 one pig from each of the three diets showed hyperplastic changes in the pars oesophagea of the stomach. In experiment 2 no gastric abnormalities were found, but bile staining was present in the pyloric zone of one pig fed each of the three diets. In experiment 3 hyperplastic lesions of the pars oesophagea (and bile staining) were present in 19 (14), 10 (7) and 4 (1) pigs fed diets O, T and R respectively.

Fat thickness and measurements of the m. longissimus (‘eye’ muscle) were taken at the last rib in 350 lambs' carcasses which were fully dissected. The lambs were from two ewe breeds, Clun and Colbred, and two ram breeds, Suffolk and Hampshire, and the carcass weight range was 15 to 21kg. Castrated males and females, and singles and twins, were evenly represented.

Rib fat thickness (J) was a slightly more precise predictor of the weights of lean, subcutaneous fat and subcutaneous plus intermuscular fat, when used in a multiple regression equation along with carcass weight, than fat thickness directly above the greatest depth of the ‘eye’ muscle (C). Both of these were more precise predictors than ‘eye’ muscle width and depth. Accounting for breed, either by allowing for different intercepts or completely different regression lines, did increase the proportion of variation in tissue weights explained by carcass weight and J or C, but to a small and, it was considered, commercially unimportant extent. This was despite differences in conformation between the breeds, reflected in this work by smaller ‘eye’ muscles in the ewe than the ram breeds and also in maturity, which might have been expected to influence tissue, including fat, distribution.

The results indicate that breed differences in partition and distribution within and between the carcass fat depots in sheep are smaller than those between the carcass and intra-abdominal fat depots.

A feeding trial was carried out, using 180 pigs, to assess the effect on performance when intact male and female pigs were housed together in the same pens from 20 to 90 kg live weight. There were no significant differences in daily feed intake, rate of growth or feed: gain ratio between pigs from mixed-sex pens and pigs from single-sex pens. Carcass measurements indicated slightly leaner carcasses for intact male pigs whether housed in separate pens or together with female pigs, while female pigs likewise had a significantly higher dressing percentage.

An adverse reaction in pigs to the anaesthetic halothane at approximately 8 weeks of age appears to be controlled by a single recessive gene affecting stress susceptibility, lean content and reproductive performance. In a survey of British nucleus herds, a total of 2998 pigs between 5 weeks of age and 28 kg live weight were given 3-min halothane tests during visits to 17 breeders or companies. There were no positive halothane reactions among 764 Large Whites from 7 herds. The frequency of positive reaction among 1538 Landrace from 14 herds averaged 11%, with a range from 0 to 23 % in individual herds. Frequencies in other pure breeds or synthetic lines varied from 0 to 88%. British and foreign breeds are compared, and the possibility of eliminating the halothane gene is discussed.

Thirty Large White × (Landrace × Large White) gilts were allocated to one of three treatments such that one gilt from each of 10 litters was on each treatment. The treatments were: (i) continuous boar exposure (CB); (ii) 30-min daily boar exposure (DB); and (iii) control, which had no boar exposure (NB). The experiment started at a gilt age of 165 days, and continued until either puberty was detected or a cut-off age of 250 days was reached.

The results indicate no significant difference in age at puberty between the CB and DB groups (194·6 v. 198·7 days), although both were significantly younger at puberty than the NB group (232·1 days, P<0·01). A possible ‘boar age’ effect is discussed.

Two groups of crossbred ewes, produced by crossing the Scottish Blackface with two prolific sheep breeds, the East Friesian and the Animal Breeding Research Organisation Dam Line, were compared in good lowland conditions over three ages (2 to 4 years) from 1976 to 1978. The East Friesian crossbred ewes were heavier, had larger, heavier litters and had heavier lambs at weaning. More of their lambs were slaughtered directly off their dams, at heavier weights and at earlier ages. The total weight of lamb sold per ewe was about 15% higher than for the Dam Line crossbred ewes.