Conditioned taste aversion (CTA) is a useful tool to modify animal feed preferences, allowing the implementation of selective grazing to control weeds in tree orchards without damaging the trees or affecting fruit production. LiCl is commonly used for inducing CTA. However, studies investigating the long-term persistence of CTA by LiCl in small ruminants are scarce. With this aim, we evaluated the efficiency of two LiCl doses (AV1 and AV2, 175 and 200 mg/kg BW, respectively) and a control (C, 0 mg/kg BW) for averting non-lactating dairy goats (n=15) to olive tree leaves. Aversion induction was reinforced on day 9 in those goats that consumed >10 g of olive leaves. Mid-term aversion effectiveness was assessed by five double-choice feeding tests (days 16, 24, 31, 38 and 53) of 30 min each, where 100 g of olive leaves were offered side-by-side with 390 g of Italian rye-grass (as-fed). Long-term aversion effectiveness was assessed in C, AV1 and AV2 goats by grazing for 30 min in paddocks with a simulated olive tree (days 59, 90, 121, 182 and 420). Moreover, C and AV2 goats were compared under on-field conditions (days 143, 211 and 363) in a commercial olive grove also for 30 min. The CTA proved to be established with a single LiCl dose in all goats and persisted for 4 and 55 days in AV1 and AV2 goats, respectively (P<0.001). However, 80% AV1 and 20% AV2 goats needed to be reinforced at day 9. When grazing under simulated olive tree and commercial olive grove conditions, the CTA goats, especially AV2 group, avoided the contact with the olive trees and minimally used a bipedal stance to feed leaves, than control goats. On average, time proportion spent consuming olive leaves and sprouts was much greater (P<0.05) for C (50.7±9.1%) than for AV1 (14.4±3.9%) and AV2 (3.1±0.9%). In conclusion, the 200 mg LiCl/kg BW dose was more effective than the 175 mg LiCl/kg BW dose for inducing an effective long-term CTA to olive tree leaves in goats.

Theory that successfully explains the magnitude and range of estimates of protein retention (PR) efficiency from the cost of turnover of existing protein indicates that conventional curves for growth description are inappropriate for protein growth. A solution to this problem is found in the consideration that the rate-limiting steps for protein synthesis (PS) and breakdown are likely to be associated with the diffusion of metabolites in and between cells. The algebraic scaling of nuclear and cellular diffusion capacity with tissue or total body protein leads to a parameterization of the primal differential equation for PR (kg/day) based on two terms representing PS and breakdown, viz.where c is an arbitrary constant, Q is the proportion of nuclei active in cell growth or division in a tissue or the whole body, α is the limit mass for protein (P, kg) in a tissue or the whole body, the power X+Z represents the rate-limiting steps in protein breakdown and Y is the power of the relationship between cell volume and the amount of tissue protein. For the whole body, the contribution of the different tissues should be weighted in proportion to their PS rates with, on average, Y = 1/2. The constant 4/9 arises from the scaling of the specific diffusion rate of DNA activator precursors from nuclear dimensions and from the relationship between nuclear and cell volume. Experimental evidence on protein breakdown rate as well as protein and body mass points of inflection indicates that the range of theoretically possible numerical values of the rate-limiting powers X+Z = (i+ 3)/9 for i = 1, 2, … ,12 seems adequate for the description of the range of observed whole body protein and body mass growth patterns for mammals. Q = 1 represents maximal protein retention, and for 0 < Q < 1, experimental evidence exists in support of a theoretical relationship between Q and food ingestion. The conclusion follows that some knowledge of the protein limit mass (α) and of the point of inflection (related to X + Z) is the main requirement for the application of the theory for description and prediction in animal nutrition and breeding.

Previous reports have suggested the presence of a major gene influencing prolificacy in the Cambridge sheep breed. To estimate the effect of such a gene, high and low prolificacy groups were established in a Cambridge sheep flock between lambing years 1990 and 1993. In 1990-1991 ovulation rate (OR) was used as the basis for allocating ewes into groups but for 1992-1993 litter size was used also as a secondary selection criterion. In 1990 and 1991 small groups (each with one ram) of extreme phenotype were formed. In 1992 and 1993, six high and six low groups were formed using all available ewes, increasing the number of observations but with less selection pressure for high and low prolificacy. Results from the groups were interpreted on the basis of a major gene with additive effect resulting in three distinct genotypes (CC, Cc and cc). It was assumed, because of the selection method adopted, that CC ewes were exclusively in the high groups, heterozygotes (Cc) were distributed between the high and low groups and that cc ewes were exclusively in the low groups. In 1990-1991 there was a difference in OR of 4·0 between ewes allocated to the high and low groups. In 1992-1993 the difference was 1·9. Litter size differences between groups averaged 0·73. Whilst the high group progeny had higher OR, the differences between groups were less than differences observed between groups based on selected dam records, possibly a reflexion of the young age at which progeny records were collected. Differences between the high and low groups suggest a gene effect for adult ewes of approximately 2·0, with expected OR, above a basal level of 2·0, of 4·0 and 6·0 for heterozygous and homozygous carriers respectively. The effect of the gene in young ewes (predominantly 1 to 2 years) was approximately 0·8.

The effect of monensin supplementation on suckling male dairy calves was studied on a commercial farm. Twenty-eight calves were given monensin supplements from the age of 1 week and compared with a similar group not given monensin. During a 52-day suckling period, the supplemented calves gained 0·12 faster, with little difference in the conversion ratio of metabolizable energy into live weight. During the subsequent 42 days, there was no difference in daily gain, but the supplemented animals were 0·064 more efficient in the conversion of metabolizable energy into live weight.

The occurrence of melanin pigmented wool fibres in the skirted white fleece wool from 1-year-old Corriedale ewes, having either least (group 1), most (group 3) or an intermediate level (group 2) of black nose skin pigmentation, was investigated. Thirteen of the 87 fleeces analysed had the equivalent of 10 to 389 isolated pigmented fibres per 100 g of scoured wool. The mean diameter of the pigmented fibres was similar to that of the fleece specimens analysed and they occurred singly or in small groups within individual staples. Large numbers of isolated pigmented fibres in fleeces were widely distributed, and constitute a serious problem of identification by visual inspection. Fibre darkness and the number of fleeces found with pigmented wool fibres were two measurements which showed a significant association (P < 0·001 and P < 0·05, respectively) with nose skin pigment group. With one exception from group 2 the results support the suggestion that the usual selection for dark nose skin in this breed may be antagonistic to selection for a white fleece. The pigmented lengths of fibres were found to be independent of nose skin pigment group.

Eight wether lambs were used to determine effects of an oestradiol-17β (E2β) implant on metabolic responses to an epinephrine challenge. Blood was sampled before and after an epinephrine challenge, on days 0 and 22 of E2p implantation.Oestradiol-17 ft implants increased pre-injection (basal) serum insulin (INS), growth hormone and free fatty acids (FFA), and decreased basal serum urea nitrogen. After 21 days of E2Pimplantation, total concentrations of FFA decreased and INS increased in response to the epinephrine challenge compared with pre-implantation values. It is concluded that E2/3 implants alter metabolic responses to an epinephrine challenge in wether lambs.

There is evidence that the growth of female rats and sheep may be constrained by physiological concentrations of glucocorticoid hormones. This study was designed to examine the effects of trilostane, an inhibitor of adrenal steroidogenesis, on serum cortisol concentrations and growth in pigs.

First, trilostane was tested at three doses (250 mg, 500 mg and 1000 mg per pig) to examine its effect on serum cortisol concentrations. A reduction in serum cortisol concentration was observed 2 to 4 h after oral administration of trilostane (P < 0·05) and the adrenal response to a challenge dose of ACTH was reduced 4 to 6 h after administration (P < 0·05), at all doses tested. In a second experiment, trilostane (9·24 mg/kg body weight) was administered orally to 10 pigs twice daily for 35 days to examine its effects on growth rate. A further 10 pigs received a placebo. Trilostane did not affect weight gain or carcass composition, but caused a reduction in food intake (P < 0·05). Adrenal weight was increased by trilostane treatment and liver weight was reduced.

These results show that trilostane is effective at lowering serum cortisol concentrations acutely, but suggest that physiological concentrations of glucocorticoid hormones may not retard growth rate in barrows.

Dutch Friesian purebred and Holstein Friesian-Dutch Friesian crossbred veal calves were used to study effects of genotype and feeding level on carcass composition. Carcass analyses were carried out on a total of 56 calves of two genotypes. Calves were reared for 22 weeks and given food dependent on age. From 1 to 16 weeks calves were given the same amount of milk replacer. At week 16, calves were assigned to either a high or low feeding level. Total energy intakes for the two groups were 5062 MJ metabolizable energy (ME) and 5408 MJ ME, respectively. Carcass weight and carcass composition traits showed no significant interaction between genotype and feeding level. Dutch Friesians had higher lean: bone ratios than Holstein Friesian crossbreds (3·85 v. 3·67). Differences between the two genotypes for fat and lean proportions in the carcass were not significant. Average proportions for lean and fat were 653 and 134 g/kg.

Differences between the two feeding levels for carcass composition were significant. Calves on the low feeding level had 655 g lean and 131 g fat per kg, while calves on the high level had 645 g lean and 143 g fat per kg.

The influence of the dissection technique on the differences in lean and muscle proportion between groups was studied on 18 carcasses using a standardized butcher's method (the Institute of Animal Husbandry (IVO) standard method) and the European Economic Community (EEC) reference method for beef. Average proportion of lean was 640 g/kg by the IVO method and of muscle was 557 g/kg by the EEC method. The difference between the two genotypes for lean proportion was smaller by the' EEC method due to the more complete separation between muscle and fatty tissue. Dutch Friesians had more intermuscular fat than Holstein Friesian crossbreds. Results of the EEC reference method indicate differences between the two feeding levels for fat as well as for protein deposition.

A rabbit nesting box incorporating a low wattage heated floor was developed. In a preliminary study a floor surface temperature in the box of 27°C was found to be adequate to minimize chilling of young pups in the nest. A full scale trial followed using 44 crossbred does, 22 provided with a nestbox containing a heated floor and 22 with a control plywood nesting box. The experiment continued for six successive reproductive cycles over the period April 1981 to February 1982 in an unheated rabbitry. Throughout the year significantly more pups reached weaning age when does were provided with nestboxes containing heated floors. On average, 0·15 of all pups born to does with heated floors had died by 28 days post partum, the comparable figure for unheated floors being 0·56. This reduction in mortality in heated boxes was apparent both on the day of birth and in the subsequent weeks prior to weaning. Ambient temperature and the wetness of the nest had a strong influence on the survival of pups in control boxes with high mortality rates experienced in the cold winter months (0·79 in February 1982). Most of these deaths in the control boxes were attributable to chilling and/or starvation in the nest (0·53 of diagnosed deaths overall). The running costs of the heated nestbox system are discussed.

1. Forty-two piglets were used to study the effects of a low, medium or high level of energy intake (1·0, 1·4 and 1·9 MJ gross energy per kg W0·75 per day respectively) from 1·8 to 10 kg live weight and a low or high level of energy intake (1·4 and 1·8 MJ digestible energy per kg W075 per day respectively) subsequent to 10 kg live weight on growth performance, body composition and the cellularity of muscle and subcutaneous adipose tissue to 30 kg live weight. During both live-weight periods all pigs received the same daily intake of crude protein.

2. Raising energy intake in the period prior to 10 kg live weight increased (P < 0·-05) growth rate, body fat content and fat cell size but reduced food conversion efficiency, body protein and water (P < 0·05) and muscle deoxyribonucleic acid. These effects on body composition and muscle deoxyribonucleic acid at 10 kg live weight were still evident at 30 kg live weight.

3. Subsequent to 10 kg live weight, pigs previously given the lowest energy intake deposited protein and fat at a faster rate and exhibited more rapid and efficient growth (P < 0·05) than pigs previously given the high energy intake.

4. At 30 kg live weight pigs given the two higher levels of energy intake before 10 kg live weight contained less deoxyribonucleic acid (P < 0·05) in subcutaneous adipose tissue and had larger (P < 0·05) fat cells than those given the lowest energy intake before 10 kg live weight.

5. The effects of energy intake subsequent to 10 kg live weight on growth performance, body composition and the cellularity of muscle and adipose tissue were qualitatively the same as those for the period 1·8 to 10 kg live weight.

Diethylstilbestrol (DES) implants have consistently increased the weight gains and feed efficiency of 5 to 7 month old fattening lambs. The effects of DES on young sucking lambs is less well delineated. Twelve mg DES implants used by Perry, Andrews and Beeson (1951) and Clegg, Albaugh, Lucas and Weir (1955) and 3 mg DES implants used by Lewis, Hines and Mansfield (1966) resulted in significant increases in weight gains of 6-to 14-week-old lambs. Conversely Jordan and Dinusson (1950), Jordan (1953) and England (1959) using 3 mg implants reported no significant increase in weight gains of 2- to 4-month-old grazing sucking Iambs. Wilkinson, Carter and Copenhaver (1955) implanted 6 to 8 week old grazing, sucking lambs with 10 mg of oestradiol and 250 mg progesterone. No increase in weight gains resulted and 5 of 28 lambs treated were lost from prolapse of the rectum.

The true digestibility of protein from diets containing one of the protein-rich foodstuffs, sunflower oil cake, cottonseed oil cake, maize gluten meal and fish meal, was determined in chickens and in the small intestine of sheep. With the exception of maize gluten meal, a close correlation was found between digestibility in the two species (r = +0·98; P < 0·05) and in the sheep small intestine between the true digestibility of utilizable nitrogen and acid-detergent insoluble nitrogen content of the diet (r = -0·96; P < 0·05).

In a trial involving 231 pigs grown from 20 to 90 kg live weight, three methods of adjusting the feed allowance were compared, namely according to live weight and a scale with weekly adjustments, or according to age with fixed increments of feed, adjusted either weekly or every 3 weeks. Irrespective of the frequency of feed adjustment, rationing by age gave as satisfactory results in performance and carcass quality as rationing by live weight, and reduced labour requirements by eliminating the need for regular weighing of the pigs throughout the growing period.

Total follicle density, primary follicle density, secondary follicle density, secondary/primary ratio and incidence of medullated fibres were studied in skin specimens from 78 2-year-old Merilin rams representing nine parent studs in Uruguay. The limited data available suggest that the studs sampled may fall into various groups, although separation into distinct groups is not equally well defined for all variables measured. Consequently, a firm conclusion about the Merilin awaits further information on fleece weight, staple length and body weight.

This experiment studied the effects of body condition, long- and short-term levels of nutrition and trypanosomosis infection on the productivity of N’Dama cows using a 2 x 2 × 2 factorial cross-over design. Pre-partum, 23 cows received supplements for 6 months (H), the other group of 20 for 2 months (L). Both groups grazed native pastures. Two days post partum, half the cows from each group were placed on a basal (B) or supplemented (S) plane of nutrition. The diet of concentrate, groundnut hay and andropogon hay was the same, only the quantities differed. Four weeks post partum half the animals in each group were inoculated with T. congolense organisms (I), the others acted as controls (C). The trial continued for a further 6 weeks.

Pre-partum nutrition (H, L had no effect on dry-matter intake (DMI) but pre-partum feeding (H) improved post-partum productivity, evident by higher dam live weights (P < 0·05), body condition (P < 0·001), calf birth weight (P < 0·05) and calf live-weight gain (P < 0·01). Post-partum nutrition had no effect on productivity. Trypanosomosis infection caused a reduction (P < 0·05) in total DMI. The decline in groundnut hay and concentrate intake was proportionally (P < 0·001) greater in the S-I group than in the B-I group. A low plane of nutrition pre-partum depressed milk yield but increased fat concentration (P < 0·05). Infection significantly reduced milk offtake (P < 0·05). The reduction in milk offtake (P < 0·01) and calf live weight (P < 0·05) were proportionally larger in the B-I than in the S-I group. Infection caused a decline in milk protein concentration (P < 0·05) and protein yield (P < 0·01) which was independent of dietary effects. Infection reduced (P < 0·01) the packed-cell volume but there were no interactions with diet. None of the cows was pregnant 150 days post partum but seven were cycling, 3(5) in the H-S-I group, 2(7) in the H-B-I group, 1(5) in the L-B-I group and 1(5) in the L-S-C group. These results suggest that S-I cows attempted to maintain milk yield at the expense of live weight whereas the B-I cows had insufficient live-weight reserves that could be mobilized. This suggests the nutritional balance and changes in weight at the time of infection might be more important than historical planes of nutrition.

Available technology allows pig breeding companies to automate feed intake recording during performance test. This provides data on ‘average daily feed intake’ as recorded with more traditional manual systems. It also results in feed intake curves, i.e. the relationship between ‘days on test’ and ‘daily feed intake’. This information can be used in different ways. The feed intake curve may be described using sophisticated linear or non-linear models; these may describe the feed intake curve accurately, but model parameters cannot be used easily in genetic/economic evaluation in the context of a breeding programme. A simple method to describe feed intake curves is used in this paper, allowing for easy interpretation of the results. The objective is to study the impact of existing selection procedures on the feed intake curve and the utilisation of variation in its shape in pig breeding.

Performance test data of 1331 boars of a Large White based line, collected from November 1990 to March 1993 were analysed. Boars are tested over a 12 week period, starting at approximately 30 kg. Feed intake data are recorded with the Hunday FIRE system.

The incidence of human coronary heart disease has been correlated with the serum cholesterol level and a high consumption of saturated fat. Furthermore the cholesterol level can be raised by shorter chain fatty acids (Rose, 1990). It was therefore interesting to compare breeds extreme in terms of fatness. The adipose tissue proportion of the Belgian Blue double muscled type (BBDM) is low while that in Holstein is high, the Belgian Blue dual purpose (BBDP) type being intermediate. The present experiment was designed to investigate how large difference in degree of fatness can be associated with differences in fatty acid composition.

Four bulls of the 3 breeds were used in a fattening trial. Their initial weight was 340 kg. Biopsy samples were taken from the Longitimus Dorsi (LD) at weeks 5 and 16 of the fattening period. They were slaughtered after 145 days. The 7-8-9 ribs and perirenal fat (PR) were removed at slaughter. Intramuscular (M) and intermuscular (IM) fats of the LD were obtained after dissection of the 7-8-9 ribs.