Crossbred cows were evaluated for reproductive performance and live weight, and for pre-weaning growth and viability of progeny sired by seven unrelated breeds. They were also evaluated on overall productivity expressed as weight of weaned calf per cow mated per year, per 100 kg of cow per year and per 100 kg metabolic weight of cow per year. The cows comprised reciprocals of Africander with Mashona, Nkone, Brahman and Sussex, one-way crosses sired by Sussex out of Mashona, Nkone and Brahman dams, and by Charolais out of Africander, Mashona, Nkone, Brahman and Sussex dams. These represented sanga × sanga, sanga × zebu, Bos taurus × sanga, Bos taurus × zebu and Bos taurus × Bos taurus crossbred types. Bos taurus × zebu crosses were superior to other breed types for all the three productivity indices and for virtually all the individual components of these. There was little difference between the other four breed types in overall productivity of components of these. Differences between reciprocals were observed in sanga × sanga and sanga × zebu, cows with Africander dams being more productive than reciprocals with Mashona, Nkone and Brahman dams. The Bos taurus × Bos taurus cross was inferior in overall productivity primarily due to large cow weight and relatively low growth rate of progeny. Progeny sired by Friesian, Simmental and Brahman had higher weaning weights than those sired by Hereford, Aberdeen Angus, Africander and Tuli. Overall, heterosis was positive for all traits and averaged 0·15 for the three measures of cow productivity. Heterosis was three times higher in the Bos taurus × Bos indicus cross than in the Bos indicus crosses.

Rabbit lung is often used to study the pathophysiology of some congenital anomalies affecting the lung because its development is very comparable with that of human. Retinoids and the molecular transducers of the retinoic signal play a crucial role in mammalian lung development. In the rabbit, the molecular retinoic pathway has so far been poorly studied. As a first step in elucidating this process, we aimed to identify the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). We cloned a part of the nuclear receptors (RARs and RXRs), and we used reverse transcription - polymerase chain reaction (RT-PCR) and immunohistochemistry assays to demonstrate the presence of RAR (α,β) and RXR (α, β) at all stages of rabbit lung development. Our results initiate further analysis into the molecular and genetic functions of retinoids during normal and pathological rabbit lung development including the surgical model of congenital diaphragmatic hernia.

Ninety-six multiparous sows were allocated at random on the 1st day of mating at the post-weaning oestrus to three dietary treatments of: 1·84 kg control diet (C); 0·92 kg control diet plus 0·92 kg pelleted hay (R); or 1·84 kg pelleted hay per day (M) for the following 10-day period to determine if restriction of nutrient intake affected reproductive performance. Subsequent to the 10-day period of nutrient intake restriction, all sows were fed 1·84 kg control diet once daily. The treatments had no effect on pregnancy rate, number of piglets born, number born alive, number weaned, or on piglet weight at birth or at weaning. Sows on the M treatment from oestrus to day 10 lost more weight (8·6 kg) during the 10-day period of nutrient restriction than the sows on the R (3·4 kg) or. the C (0·7 kg) treatments. However, weight gain from oestrus to day 110 of gestation was similar for all three treatments (16·5, 17·8 and 17·1 kg, respectively). Thus, restriction of nutrient intake early in pregnancy is not a critical factor affecting litter size and weight at birth or weaning in the multiparous sow.

1. The effect of feeding a salt solution containing ammonium acetate on the yield and fatty acid composition of cows' milk fat has been studied.

2. The trials involved eighteen lactating Jersey cows. In the first trial one group of 5 cows was fed the treatment diet throughout an experimental period of 10 weeks and another group of 5 cows acted as controls. In the second trial which extended over four 28-day periods, two groups of 4 cows spent alternate periods on treatment or control diets. The overall results of the two trials were in agreement.

3. The outputs of C4-C14 acids and of palmitic acid per kg of milk yielded were greater than the intakes. The output of C18 acids was less than the intake per kg of milk yielded. These observations were noted on both treatment and control.

4. Treatment resulted in an increased secretion of C4-C14 acids and of palmitic acid and a decreased secretion of C18 acids per kg of milk yielded.

5. The results have been discussed in the light of present knowledge concerning the synthesis of fat in the mammary gland.

This work was designed to study the influence of parity (multiparous (MP, no. = 9) or primiparous (PP, no. = 10)) and feeding level (control diet (CD; 1·00) or restricted diet (RD; proportionately 0·70 of requirements) in a 2×2 factorial design on the utilization of exogenous glucose in the suckler anoestrous Charolais beef cow. Lack of ovarian activity was confirmed by low circulating progesterone concentrations measured in weekly blood samples taken after parturition. An injection of glucose (1·5 mmol/kg live weight) lasting 20 min was given 30 days and 50 days post partum. Blood samples were collected before and for 120 min after the start of the injection and plasma insulin, glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate and urea were measured. Although plasma glucose concentrations were not significantly different between treatment groups in the period immediately after the injection of glucose, CD PP animals had higher plasma insulin levels than CD MP animals (at 25 min: 596·4, 283·8, 435·1 and 309·6 pmol/l, P < 0·05 for groups PP CD, MP CD, PP RD and MP RD respectively). Plasma NEFA concentrations were initially higher in the RD groups compared with the CD groups but were reduced by the glucose injection (P < 0·001). However, the PP RD cows took longer to respond to the exogenous glucose compared with the MP RD cows (at 25 min: PP RD: 133·2 and MP RD: 57·5 eq/l, P < 0·05). In conclusion, suckler anoestrous PP cows appear to require higher plasma insulin levels than MP cows to metabolize exogenous glucose and underfed PP cows were slower to reduce plasma NEFA after glucose injection than underfed MP cows.

Two experiments were conducted to elucidate the effects of intra-muscular injection of oestradiol within 1 min of birth (experiment 1) or within 4h of birth (experiment 2) on piglet activity, growth and pre-weaning survival rate. In experiment 1, 248 piglets (25 litters) were alternately injected within litter at birth with either 1 ml peanut oil/saline solution or 0·1 mg oestradiol benzoate in this carrier solution. The subsequent behaviour, growth and survival of these piglets were recorded. Experiment 2 used 38 litters (385 piglets), these being treated by litter with either of the same two treatments as soon after birth as they were found (approx. range 0 to 4 h). Piglet survival data were collected from this field trial. Oestradiol treatment significantly reduced the intervals from birth to reaching the udder (596 v. 740 s, P < 0·05) and from birth to first sucking (1060 v. 1497 s, P < 0·01) relative to control piglets in experiment 1. Treatment had no significant effect on pre-weaning growth rate (experiment 1), but did tend to reduce early postnatal mortality rate in both experiment 1 (7·2 v. 2·4% for control and oestradiol-treated piglets respectively) and experiment 2 (13·0 v. 10·2% for control and oestradiol-treated piglets respectively). It is concluded that oestradiol treatment at, or soon after, birth induces short-term hyperactivity in piglets. This may subsequently be reflected in an improvement in pre-weaning survival rate of piglets, although further data are required to confirm this conclusion.

Data for 432 litters of pigs were collected from 1965 to 1975 inclusive, at the Fasola Stock Farm, near Oyo in the Western State of Nigeria. The breeds represented were Large White, Duroc and Hampshire, and their crosses. The main objective was to investigate the effects of certain identifiable environmental sources of variation on litter performance characteristics such as litter size, mortality and weight at birth, 3 weeks and 8 weeks of age. Breed and year effects were significant for the litter size traits, but parity of dam, season and breed × season effects were significant only for litter size at birth which increased up to the fifth parity and then declined steadily in subsequent parities. Postnatal pig mortality was affected significantly by breed, litter size at birth and breed × season interaction. It was found that the larger the size of litter at birth the higher the postnatal mortality. Average pig weight at birth was reduced by approximately 0·01 kg for each additional pig in the litter.

1. Experiments have been performed to determine the thermal effects, on pigs, of the ingestion of whey at various temperatures while housed at various air temperatures.

2. Measurements of carotid artery and rectal temperatures showed that a general cooling of deep-body tissues occurred after the ingestion of cool whey.

3. Measurements of rectal and skin temperatures, and observations of respiratory rate and shivering activity, indicated that thermo-regulatory responses were induced by the ingestion of cool whey; the nature of the responses was dependent on the air temperature.

4. The results indicate that the temperature of liquid food offered to animals is a significant parameter in their climatic environment.

Lambs from Perendale, Merino × Perendale, Romney, Merino × Romney and Coopworth ewes, and Southdown and Suffolk sires were assigned to three groups. Groups received no treatment, nine weekly doses of 175 mg iron (Fe) per kg body weight or nine weekly doses of 175 mg zinc (Zn) per kg body weight. They were slaughtered 1 week after the last dose. Samples of m. longissimus were analysed for Fe and Zn concentration.

Muscle Zn concentration was greater for Southdown-sired lambs (85·5 mg/kg dried muscle) than for Suffolk-sired lambs (77·6 mg/kg; P < 0·01). Dam genotypes and the interaction of sire breed and dam genotype were not significant for Zn concentration. Heritability of muscle Zn concentration was estimated to be 0·92 (s.e. 0·48). Muscle Fe concentration showed a significant interaction between sire breed and dam genotype (P < 0·05). Heritability of muscle Fe was estimated to be 0·21 (s.e. 0·38). No significant interactions of either sire breed or dam breed × treatment were found.

The twinning rate of Finn × Awassi ewes in a breeding management system which included three breeding periods a year, namely, June, September and December-January, was studied in animals mated at their natural or induced oestrus.

A similar number of lambs per ewe lambing was obtained from the ewes mated either at the induced oestrus in June or September, or at their natural oestrus in December. A significant decrease was found in the twinning rate of the ewes mated in January after hormone treatment. The conception rate was highest in the ewes mated in December-January.

At weaning at 3 months of age (week 1), 30 red deer hind calves were housed in six groups of five animals at a stocking density of 1·5 m2 per head and maintained in these groups for 4 weeks. At the start of week 5, all calves were immunized with ovalbumin (OVA). Fifteen calves, from three groups, selected at random, were transferred to individual pens which restricted visual and tactile contact with others (ISO) while the remaining animals were kept in their groups (GP). The behaviour, food intake, live-weight gain, antibody and lymphocyte responses in vitro to OVA and lymphocyte responses in vitro to the non-specific mitogen, concanavalin A (ConA), of all calves were assessed in each of weeks 5 to 9. Isolated calves had a lower mean live-weight gain than GP calves (P < 0·001), although there were no differences in food intake. Significantly more time was spent lying (P < 0·001) but less time feeding (P < 0·05) and self-grooming (P < 0·001) by ISO than by GP calves. There was no significant difference between ISO and GP calves in the cortisol response to an ACTH challenge test (10 i.u.) at week 11. Lymphocyte responses and antibody titres to OVA were lower in GP than in ISO calves at weeks 7 (P < 0·05) and 8 (P < 0·05), respectively. In contrast, GP calves had greater lymphocyte responses to the non-specific mitogen, ConA, in weeks 7 (P < 0·05) and 10 (P < 0·001) but not in week 9 compared with ISO calves. Differences in lymphocyte stimulation were attributed to the non-specific mitogenic nature of ConA. Factors such as agonistic interactions evident in group housing may have compromised the antibody and lymphocyte responses to OVA by GP calves but conversely the lack of social contact may have also suppressed behavioural activity in ISO calves.

Weaner Hampshire × Landrace × Large White (Hampshire cross) and Landrace × Landrace × Large White (Landrace cross) pigs were given combinations of three diets differing in crude protein content (high: H, low: Land very low: vl). Hampshire cross pigs at 90 kg, both under ad libitum and restricted feeding had greater rates of gain and eye muscle measurements and shorter carcasses than Landrace cross pigs, but were fatter after ad libitum feeding and more efficient food converters after restricted feeding. The HLL treatment led to improved gain and food conversion compared to the LLH or LLL treatment, whereas the LLH treatment led to larger eye muscle measurements. The LvlH treatment led to greater efficiency and eye-muscle area than treatment Lvlvl at 114 kg. An economic analysis was carried out to assess the relative profitability of slaughtering at a range of live weights. Curves were fitted to the data on food intake and live weight. Values were assumed for major costs, and a seven-day interval was allowed between batches of pigs. The calculations indicated that the H diet led to a slight increase in monetary return per pig per day when it was given in the post-weaning period to pigs fed to a scale. Although the Hampshire cross pigs showed a response to the H diet in the finishing period when slaughtered either at 90 or 114 kg, their calculated return was not increased. Ad libitum feeding led to a greater return for heavy but not, on average, for bacon pigs. Maximum return occurred at slaughter between 70 and 115 kg live weight and was only margin-ally greater for restricted baconers at 90 kg than for ad libitum heavy pigs at 110–115 kg. However, return as a percentage of working plus fixed capital was greater for baconers, but the ratio rose throughout the range of hypothetical slaughter weights in both groups. In-clusion of the cost of borrowing money had a negligible effect on the slaughter weight for maximum return with pigs managed in batches.

A feeding trial is described in which 32 individually-fed Large White pigs were used to investigate the effects of variations in the protein and energy status of the diet on growth, efficiency of food utilisation and carcass characteristics. The salient features of the finding were:

1. Over the weight interval 50–100 lb., it appeared that 1·0% was a more appropriate level of dietary lysine than one of the order of 0·75%; the former figure corresponded to a level of 5·8% of dietary protein.

2. In the ‘finishing phase’ of growth from 100–200 lb. the pig clearly tolerates wider energy : protein ratios than is the case in earlier life, with advantageous results in terms of growth performance but deleterious effects on carcass suitability.

3. An increase in dietary energy status in the ‘finishing phase’ yields growth responses only if protein level is appropriately adjusted.

4. It is suggested that Large White pigs require a level of 0·5–0·6% of dietary lysine in the ‘finishing’ period.

A study was made of the growth of Holstein Friesian females in an intensive production system in the Venezuelan tropics, using monthly weights from birth (no. = 922) up to 72 months of age (no. = 63). Birth weights were adjusted for age of dam, month and year of birth of heifer, whereas subsequent weights were adjusted for birth weight and month and year of birth. Despite lower weights at birth (mean = 35·9 kg), live weights were comparable to the Beltsville standard for the breed up to 12 months of age. However, at 24, 36, 48 and 72 months of age the weights observed only reached 0·84, 0·77, 0·75, 0·79 and 0·78, respectively, of the Beltsville standard. No effect was observed on birth weight of age of dam, month or year of birth, but birth weight affected subsequent weights (P < 0·001) and the effects of month and year of birth on live weight were significant at most ages. The poor quality of the forage consumed and stress due to high environmental temperatures and humidity appear to be the main reasons for the reduced growth rates. Von Bertalanffy's model gave a higher residual error than a polynomial model when fitted to the data, but resulted in a curve which agreed more closely with the conventional biological growth pattern.

An experiment was carried out in which equal amounts of concentrate were given to beef cattle once, twice or three times per day, with a basal hay diet. There were no significant differences between treatments in food and water intake, digestibility coefficients, nitrogen balance data or live-weight gain.

Data obtained from a detailed base from a commercial breeding company of Landrace and Large White purebred nucleus sows were used to estimate genetic parameters of piglet number born alive (NBA) following artificial insemination and natural service. Heritabilities were small but significantly different from zero, and similar to literature estimates. The genetic correlation (rG) of NBA after AI or natural service using pooled data was 0·71 and was significantly different from one (P<0·01) but not significantly different between breeds (P>0·1). It is concluded that mating type may result in a re-ranking of sow genetic merit for NBA.

Six experimental diets with similar contents of macronutrients (450, 300 and 70 g/kg dry matter of protein, carbohydrate and fat, respectively) and, therefore, total energy, hut differing in the composition of lipid component, were each given to three replicate groups of European eel. Different fat mixtures were used to formulate diets with different levels of fatty acids considered as essential for fish: linoleic (18: 2n6), linolenic (18: ЗпЗ) and highly unsaturated fatty acid (HUFA)n3, mainly EPA (20: 5n3) and DHA (22: 6n3). One tested diet contained low levels of all the three components, three diets had a high level of each one of these, the fifth diet contained high levels of both 18C fatty acids and, finally, a sixth diet incorporated simultaneously high amounts of 18: 2n6 and (HUFA)nЗ.

Dietary lipid composition did not significantly affect food intake or protein and fat apparent digestibility. However, growth and food efficiency were the best with the diet containing approximately 5 g/kg of both linoleic and linolenic acids. Although all groups increased their body fat content over the experiment, the fatty acid composition of total muscle lipids was rather insensitive to lipid dietary composition, perhaps due to the high body fat content of the eels prior to the experiment.

Maturing patterns are established for 26 body organs using data from 35 rams of two strains of Merinos of different mature size (97 and 120 kg).

The proportion of shorn full live weight represented by each structure at maturity was very similar for all organs except the head, hide and distal limbs which were relatively heavier in the small strain. and small intestine and blood which were relatively heavier in the large strain.

All organs were early maturing relative to shorn full live weight except the hide and the penis plus bladder, which matured at the same rate as live weight. The maturity coefficients differed between strains only for the head, thyroid and omasum.

Differences in the proportion of live weight comprised by each organ in the two strains were compared at the same shorn full live weight and at the same proportion of mature shorn full live weight. Differences in the various portions of the alimentary tract and other internal organs, with the exception of the kidneys, which were evident in comparisons at the same weight, were reduced when compared at the same proportion of maturity. The difference between strains for head, hide and distal limbs was greater at equal maturity than at equal weight suggesting a functional relationship to body weight rather than to ultimate mature body size.

It was concluded in genetic comparisons of animals of different mature size, the most appropriate basis of comparison of relative organ weight will be at the same proportion of mature live weight.

The native fat-tailed Awassi and the imported German Mutton Merino (GMM) sheep are well adapted to semi-arid conditions (Degen, 1977; Degen and Shkolnik, 1978). This enables these sheep to graze large areas of the Negev Desert in Israel that is marginal for farming. However, under extensive conditions both these sheep breeds yield low lamb crops producing fewer than 1·0 lamb per ewe per year.