A review of recent trends in animal science is used to provide a flavour of how, from a purely technical viewpoint, evolving biotechnology may influence animal production systems in the foreseeable future. The areas considered are: the nutritive value of foods and forages, animal health and welfare, the temporary alteration of production traits to meet an immediate goal, and the permanent alteration of traits to meet an immediate goal, and the permanent alteration of traits by genetic selection or by the production of transgenic animals. In improving the nutritive value of foods, modern biotechnology has produced food grade enzymes and amino acid supplements. Genetically engineered cereals, grasses and legumes, rich in essential amino acids, are on the horizon. In disease prevention, genetically engineered vaccines may be preferable to conventional ones in that they have a defined composition, with a degree of control during manufacture which allows amino acid substitution within the peptide to confer specificity to a particular serotype.

Modern techniques with the potential to promote a transitory alteration in a production trait involve either immunization against an inhibitory biochemical pathway or active promotion of a stimulatory pathway by the administration of recombinant-derived hormones and proteins. Strategies for permanent alteration of traits by gene transfer, initially directed to enhancing growth, are now shifting in emphasis towards the transfer of genes for enhanced nutrient digestion, disease resistance, and improved product quality. The role of recombinant DNA technology in the development of diagnostic probes for use in genetic selection programmes and in the monitoring of disease is also expanding rapidly.

In all areas of animal science, molecular biology is promoting a better understanding of the underlying mechanisms that control production. By so doing it should ensure that science fulfils its primary rôle of providing animal production industries with a range of options from which to choose the most acceptable way forward.

Predicted rate of genetic response for multiple trait breeding objectives from multivariate analyses is compared with that from univariate analyses for a range of breeding schemes, A selection index that approximates a multipl trait best linear unbiased prediction (BLUP) animal model is utilized. Changes in genetic parameters due to linkage disequilibrium generated by selection are accounted for. This study shows that asymptotic response in the aggregate breeding value, and its component traits, to selection on multivariate predictions, can easily be calculated from first generation responses, which use ancestral information. For two-path breeding schemes with equal accuracy for males and females, proportional reductions in responses depend only on selection intensity. In general, benefit from multivariate over univariate analyses is slightly smaller at the asymptote than in the first generation. Multivariate analyses give substantially more response than univariate analyses on untransformed data, when correlations between traits are high and when genetic and phenotypic correlations have opposite signs. The advantage of multivariate analyses decreases with increasing family size. When three random factors (additive genetic, common and individual environmental effects) are included in the model, the benefit of multivariate analysis is negligible if univariate analyses are performed on canonical traits. In this case, the advantage of multivariate analyses is never higher than 1% for all cases studied. These results are of particular relevance to the design of genetic evaluation programmes.

An animal model and an approximative method for calculating repeatabilities of estimated breeding values are used in Finnish dairy cow evaluation. Changes in estimated breeding values over time as daughters accumulate were studied. Special emphasis was given to the accuracy and potential bias in the pedigree indices of young sires. The data set used was the same as in the national evaluation and the traits investigated were protein yield and somatic cell count. The average repeatability in evaluation of bulls without daughters was 0·37. The empirical repeatability defined as a squared correlation between the pedigree index and the final sire proof was only 0·15. The reduction in the repeatability was attributed to the selection on pedigree index. The upward bias observed in pedigree indices was 5 kg (approx. 0·3 of genetic standard deviation). The bias was caused by the overestimation of bull dams' breeding value. Also the proofs of bull sires increased after the second crop of daughters. The correlation between the evaluations of the same sire calculated from two separate equal size daughter groups was 0·91 when the bull had 10 to 50 daughters and 0·87 with over 100 daughters. This illustrates how the relative weight of the pedigree decreases while more progeny information is accumulated in the evaluation.

An experiment was conducted to examine the effects of dietary fibre and starch levels on the response to condition score at calving. Fifty-two cows were used over two winter feeding periods, with 24 and 28 different cows in each. Twelve weeks before their expected calving date, cows were paired and the level of feeding adjusted to attain mean condition scores at calving of 2·0 (T) and 3·5 (F) within pairs. At calving, pairs of cows were allocated to treatment HF or LF, giving four groups in total. Each day for the first 16 weeks of lactation, all cows were offered 10 kg dairy concentrate containing either high-fibre/low-starch (FHF and THF), or low-fibre/high-starch (FLF and TLF), 2 kg sugar-beet pulp and hay ad libitum. Two cows from each group were used to determine apparent digestibility of the whole diet each year, using chromium III oxide as a faecal marker. Eight steers were used to determine the degradabilities of dry matter, nitrogen and fibre in the two concentrates and to provide rumen fluid samples for volatile fatty acid determination.

In each of two experiments, 36 3 to 5-day-old dairy calves (male and female), were allotted to one of three groups: warm housing, milk feeding in teat-buckets twice a day (group 1); warm housing and computer-controlled milk feeding (group 2); and cold housing and computer-controlled milk feeding (group 3). The experiments were conducted from September until February. The daily gain in the first 4 weeks was lower for the calves in group 3 in both experiments and for calves in group 2 in experiment 2 because of lower food intake in this period. This was compensated for by an increased gain later. In spite of the different method of milk feeding, the activity rhythm was nearly equal among groups, but at week 6 and 10 the calves in group 1 spent more time with the head over the feeding table than the calves in the two other groups. The number of unrewarded visits per calf to the milk feeding station decreased from over 30 at week 4 to around 20 shortly before weaning. The frequency of sucking/licking pen-mates was almost negligible in all groups. In order to reduce the heat loss, the frequency of calves lying with body contact clearly increased by decreasing ambient temperature in cold housing.

The paper explores a scheme for the ethical evaluation of animal biotechnologies, exemplified by animal transgenesis. It begins with an overview of prominent ethical theories (deontological and consequentialist) and proceeds to apply them to four ethical principles, viz. autonomy, justice, non-maleficence and beneficence, in relation to the interests of the treated animals and of different groups of people affected by the technology. Evaluation is facilitated by use of a schematic device — an ‘ethical grid’. The importance of public education and attitudes to biotechnology is illustrated by reference to recent public opinion surveys in the European Community. The paper concludes with a discussion of the impact of future trends in global population, food resources and environmental change, which emphasizes the need for a reappraisal of priorities in animal production systems. It is suggested that attempts to eradicate hunger, to improve animal welfare and to devise sustainable agricultural systems will be facilitated by greater investment in the emerging academic field of agricultural bioethics.

Brackish well water (BW) containing 3574 mg total dissolved solids (TDS) per I was compared with desalinated water (FW, 449 mg TDS per I) as a source of drinking water for dairy cows in the hot arid conditions of Kuwait. Friesian-Holstein cows in early lactation were given daily, 12 kg cereal-based concentrate, 12 kg fresh lucerne and 4 kg senescent date palm leaves for 196 days with the experimental treatments being either BW or FW (four cows per water type). Dry matter and water intakes were not affected by water type (P > 0·05). Cows offered BW gained slightly more weight (P > 0·05) than cows consuming FW. Although overall milk yield and composition was unaffected by water type, the decline in milk yield as the experiment progressed was significantly (P < 0·05) less for cows offered BW. Cows offered BW tended to have higher concentrations of minerals and thyroid hormones in plasma than cows offered FW. It can be concluded that water containing 3574 mg TDS per I was an acceptable source of water for dairy cows.

This experiment examined the effects of sustained levels of undernutrition applied to grazing Brahman heifers on subsequent lifetime reproductive performance. Weaned heifers were raised to a target weight of 270 kg at three different stocking rates to obtain contrasting weight gains (0·097 kglday, L = low; 0·215 kg/day, M = medium; 0·259 kg/day, H = high). They were then subjected to common grazing in a low-quality Brachiaria humidicola pasture, where mean weight changes ranged between -0.100 and +0·300 kg/day depending upon season and physiological condition. Differences in age at first calving between L and the other treatments (200 days) were maintained in subsequent calvings. Calf weaning weights were higher in L and M than in H. The mean weight of calf weaned per cow per year was higher in M than in either L of H. Cow weight at conception increased with parity, and was higher in L than in the other treatments. Similar trends were observed for the dam's weight preand post calving, and at weaning. This trend was associated with higher weight loss during lactation in I..

We conclude that in tropical grazing systems that allow only low growth rates, differences established early in reproductive life may become perpetuated for the lifetime of the animal. Management implications in the context of extensive tropical grazing systems are discussed.

Forty pregnant F1 crossbred cows (20 Holstein-Friesian × Boran and 20 Simmental × Boran) were assigned to a 2 × 2 (work × diet) factorial experiment as follows: supplemented-non-working (SNW), supplemented-working (SW), non-supplemented-non-working (NSNW) and non-supplemented-working (NSW). Working cows pulled sledges 100 days/year (pull = 350 to 450 N, 4 h/day, 4 days/week). Conception and oestrus at fixed times (200 and 365 days post partum) were analysed using linear logistic models. Proportional hazard models were used for analysing ‘failure’ time data such as time to first oestrus or time to conception. Diet supplementation significantly decreased days to first oestrus and days to conception in non-working and working cows. SW cows had similar reproductive performance to NSNW cows. In supplemented cows, work significantly delayed days to conception. However, by 365 days post partum, conception rate was similar for SNW and SW cows. Body condition at calving significantly affected post-partum reproductive ability of non-working and working cows. Natural grass hay alone could not support potential reproductive ability of crossbred cows. Work output of supplemented cows may be associated with longer calving intervals. The economic trade-offs between longer calving intervals and work output should be examined in detail.

A study urns conducted to examine herd structures and cattle disposal patterns of Bunaji herds kept under traditional management at four locations in the subhumid zone of Nigeria. Sale for meat was the single most important disposal reason, accounting for proportionately 0·55 of all disposals. Mean age of cattle sold for meat was 8 years but the age range was wide: animals as old as 17·4 years were involved in such sales. Male animals were sold at a younger age (6·2 years) than females (9·3 years). Sale of calves was an important exit avenue for rural herds with less access to milk market. Calves were sold at a mean age of 1·1 years and male calves accounted for a larger proportion (0·62) of such sales. Animal sales were highest in the early dry season and lowest in the early wet season. The predominantly arable farming location, Ganawuri, had the highest frequency of animal sales and lowest frequency of exits for ‘social functions’ (exchanges, transfers and gifts). Animal transfers, gifts and exchanges were important disposal routes in the traditionally pastoral communities, especially in locations with good grazing (e.g. Abet). Exits involving exchanges, transfers and gifts were more frequent during the dry season and least frequent in the wet season. An average herd had 77 head of cattle composed proportionately of 0·54 adult females (>3 years), 0·13 adult males (>3 years), 0·08 young bulls (1 to 3 years), 0·13 heifers (1 to 3 years) and 0·11 calves (0 to 1 year). There was a tendency toward smaller herds in later years (97 in 1980 to 51 in 1989) and a decrease in the ratio of adult females to males (from 6:1 in 1980 to 3:1 in 1989). Substantial between-location differences existed in herd size ami herd structure, ranging from the ‘beef orientation’ of the arable Ganawuri with a high proportion of immatures and calves, to the pastoral situation in Abet and Kurmin Biri with high proportion of adult animals. The proportions of adults were lowest in the early dry season, reflecting seasonal pattern in disposal and calving. The pattern in disposal reasons over time indicated a decrease in the proportion of animals exiting herds through exchanges, transfers and gifts and signified a possible shift from tradition, probably a response to population pressures and emergence of cash economies.

A dispersed hybrid MOET nucleus project was implemented in the Canadian dairy industry. Embryo yield, pregnancy rate, and effects of management and selection practices are reported. Repeatability of viable embryo yield was 0.31. Average viable embryo yield was 6.85 (s.e. 5.35) embryos per collection, with average pregnancy rates of 0.58, 0.46 and 0.51 for grade 1 fresh, frozen, and split embryos, respectively. Of the donors selected, 80% produced enough embryos to form a family of at least 15 offspring. Based on observed results, expectations of family size and structure and generation intervals were calculated. Only 10% of completed families are expected to result in less than three milking daughters. Generation interval for sib-tested sires was 58 months of age under practical field conditions, which was shorter by a factor of 0.19 than a traditional progeny test but longer than original theoretical estimates by a factor of 0.32. Realized selection intensities for a total merit index were 2.22 for sires and 3.77 for dams of embryos. Accuracies of selection for sires and dams were 0.93 and 0.73 respectively. To improve the scheme, use of more fresh embryos, embryo splitting and less delay in transferring frozen embryos are recommended.

A total of 1088 females of 14 breed groups (Angus and Hereford purebreds, and 12 first-cross groups) were evaluated over two locations for lifetime survival, numbers of calvings, numbers of calves weaned and cow lifetime records of calf survival. These traits are known to be related to a cow's lifetime productivity. The animals were part of the Ruakura Beef Breed Evaluation, designed to compare the growth and carcasses of steers, and the reproductive and maternal performance of females of different breed groups. Data were from 4 birth years of females and 11 breed-groups at location 1, and from 5 and 10 respectively at location 2, with seven breed-groups common to both locations. Females were first mated as yearlings. Culling at ages 2·5 to 4·5 years was based mainly on females that were non-pregnant on two occasions, whereas in subsequent years any non-pregnant female was culled. At location 1, there was a maximum possible number of mating years of 22 for females in the 1st birth year, declining to a maximum of 9 for those in the 4th birth year; for each age group at location 2 there was a maximum of 9 mating years. The average cow survival (number of mating years) was 7·26 (s.d. 3·02) at location 1 and 5·81 (s.d. 2·31) at location 2, with a coefficient of variation similar at both locations and averaging 0·41. The performances from the poorest to the best breed groups had a 1·5-fold range for number of mating years and a 1·8-fold range for number of calvings and number of calves weaned. The heritability of number of mating years (no. = 150 sire groups) was 0·13 (s.e. 0·08), number ofcalvings 0·11 (s.e. 0·08), number of calves weaned 0·15 (s.e. 0·08), and calf survival as a cow trait 0·027 (s.e. 0·018). This last heritability increased to 0·093 if adjustment was made to the underlying liability scale. There was no significant effect of breed of cow on number of mating years, nor on number of calves weaned per 100 calvings at either location, whilst the effect was significant for number ofcalvings and for number of calves weaned per cow (P < 0·10). The wide breed variation pointed to opportunities for selection among breeds, whilst the low heritabilities suggested that within-breed selection will be slow unless early indicator traits can be found.

Estimates of covariance components due to direct and maternal effects among birth, weaning, yearling and final weight for Australian Polled Herefords were obtained by restricted maximum likelihood fitting an animal model. Data were obtained from commercial herds participating in the National Beef Recording Scheme and an across-herd genetic evaluation service. Analyses were carried out considering nine subsets of data, each comprising at least 3000 weaning, 1000 yearling and 500 final weight records which yielded a total of 30 506,17 105 and 9486 records for the three weights, respectively. Estimates of variances and genetic parameters varied considerably between data sets. Both genetic and permanent environmental effects were found to affect all traits except final weights significantly, with maternal environmental effects explaining proportionately more than 0·20 of the total variation in weaning weight. Estimates of the direct-maternal genetic correlation were consistently negative and moderate to strong, ranging from -0·34 to -0·82 for weaning weight. Maternal correlations between weaning and yearling weights were close to unity. Estimates of the direct genetic correlations among the three later weights were 0·8 or larger. Problems with this kind of analysis are discussed.

The objective of this work was to investigate phenotypic sources of variation in the sites of storage of milk within the udder. Ten primiparous and 10 multiparous dairy cows were studied over two successive lactations in order to investigate the effects of age, parity and stage of lactation. Cistern and alveolar milk volumes were estimated at a standard 8 h after a normal morning milking by catheter drainage and machine milking with oxytocin respectively. Measurements were made at approximately 9, 20, 30 and 42 weeks of the initial lactation and weeks 1, 4, 7, 10, 20 and 34 of the subsequent lactation. In the initial lactation, there was a significant difference between primiparous and multiparous animals in the rate of decline of total daily milk yield (P < 0·001). Cistern milk yield (kg/8 h) from multiparous animals declined over the lactation whilst that for primiparous animals was maintained. The effect was shown as a significant interaction effect (P < 0·05). For both multiparous and primiparous animals cistern proportion (cistern yield divided by total milk yield at 8h after a normal milking), increased over the lactation (P < 0·001). This was largely a consequence of the reduced total milk yield. Eleven animals were studied through the subsequent lactation. Cistern yield followed a lactation curve of similar form to that for total yield. The decline in cistern yield over this lactation was much greater than the decline with multiparous animals in the previous year. This may, in part, reflect a faster decline in total daily yield. Stage of lactation and parity must be taken into account if a standardized evaluation of cistern characteristics is to be obtained.

An on-farm study was conducted over a 12-year period (1979 through 1990) at four locations in the subhumid zone of Nigeria to estimate levels of performance of Bunaji cattle and to examine factors affecting productivity in these production systems. Average weight at birth, at 9 months and at 12 months were 19·6 kg, 76·2 kg and 93·1 kg, respectively. Average daily gain between birth and 9 months was 211 g/day. The corresponding figure between 9 months and 12 months was 176 g/day. Cumulative calf mortality at 9 months and at 12 months were proportionately 0·14 and 0·15, respectively. Mean age at first calving was 62·5 months while interval between consecutive calvings averaged 22·5 months. Mean daily milk offtake was 510 ml. Mean length of offtake period varied substantially between locations ranging from 339 days in Kurmin Biri to 425 days in Madauchi. Lactation milk offtake was estimated at between 200 and 260 I. Peri-urban Madauchi had the highest daily milk offtake, the longest milk extraction period but the poorest calf growth and survival rates. Locations with low milk offtake had superior calf performance both in terms of growth and survival. Calves born in late wet and early dry seasons had superior growth and survival rates. Most calvings occurred in the dry season mainly because of the effect of season on conception rates. There was a tendency towards improved productivity on a per-animal basis over the years. This ivas so for age at first calving, calving interval, calf survival and milk offtake. Improved reproductive performance provided opportunity for higher offtakes. However, growth between 9 months and 12 months and weight at 12 months declined during the study period.

The objective of the experiment was to test whether maintenance energy requirements of non-lactating, non-pregnant beef cows increased with body fatness. Twelve Charolais cows were initially fed to attain either lean or fat body condition. Subsequently, over a period of 66 days food allowances were regularly adjusted for zero live-weight change. For the following 76 days, lean and fat cows received either 400 or 553 kJ metabolizable energy (ME) per kg initial live weight 0·75 per day, respectively. Fat cows maintained their body weight and composition whereas lean cows lost 296 g body weight, 221 g lipid and 65 g protein daily. Calculated maintenance energy requirements averaged 516 and 536kJ ME per kg live weight 0·75 per day for lean and fat cows respectively but were not significantly affected by body fatness. Diet dry matter, organic matter, crude protein and energy apparent digestibilities but not acid-detergent fibre digestibility were significantly higher in fat animals.

Fasciolosis is a serious economic disease of cattle and sheep with a worldwide distribution. In the annual control of the disease, it is vital that the issue of specific veterinary advice on the strategic use of control measures should be based on precise estimates of the levels of risk of the occurrence of the disease. This paper describes the construction of a mathematical model to forecast the level of risk of the disease in cattle in any year. The model has been developed in Northern Ireland using a computerized information database retrieval system for abattoir condemnation data. The information recorded by the system details the specific cause and location of all condemnations in cattle, sheep and pigs for all abattoirs in Northern Ireland. Analysis of a subset of these data (1976 to 1991) for cattle resulted in a univariate time series model for the recorded prevalence of condemnations due to fasciolosis in cattle livers. The overall mathematical forecasting model was constructed by regressing the residual terms of the univariate time series model with the corresponding time series of all the key meteorological variables. The best model (R2 =0·8) was obtained using the mean air temperature for the period fune to August inclusive. The model could be adopted for use in any region of the world where relevant abattoir condemnation and meteorological data are available.

Calving date (CD) records of 68 896 polled Hereford dams of 120 682 calves were coded within herd-year-season with date 1 being the date the first calf was born. Factors affecting CD and its relationship with production traits were investigated. Early calving was found to be associated with high performance, conceivably because dams calving early were able to utilize the season-dependent range pastures to their advantage thus providing adequate milk supply to their calves. Weight and age of dam, weight of calf, initial CD, index of milk production potential, and previous CD were found to have significant influence on current CD. Extremely small cows at previous weaning had a tendency to calve late. Cows calving in the spring produced calves with higher overall weight per day of age than did cows calving in other seasons. Initial CD was found to affect CD in subsequent parities. Repeatability of CD was estimated at 0·23. Heritability was estimated at 0·16 (s.e. 0·05) and indicated that additive genetic variance constitutes a moderate proportion of the variation in CD. Genetic correlation of CD with birth weight (−0·30, s.e. 0·10), post-weaning rate of gain (·0·64, s.e. 0·19) and yearling weight (−0·60, s.e. 0·11) indicated that ‘plus’ additive genes for CD influenced these traits favourably. However, the corresponding correlations with pre-weaning rate of gain (−0·03, s.e. 0·08) and weaning weight (−0·05, s.e. 0·03) were not significant.

Four groups of 20 Simmental cross heifers were actively immunized against human serum albumin (control, (C), androstenedione (A), a 30 amino acid synthetic fragment of porcine inhibin alpha (I) or A and I in combination (AI). At the time of the third and final antigen injection and again 2 weeks later, all animals were injected with synthetic prostaglandin F2α (PG) to synchronize oestrus. Concentrations of LH, FSH, insulin-like growth factor-1 (IGF-1) and inhibin (C and A heifers only) in serum samples collected twice daily during 3 days before the second PG injection and at 15-min intervals from 24 to 32 h after PG injection were determined. Two weeks later, all heifers were administered PG and ovariectomized 24 h later. Ovarian follicles were dissected from the stroma, measured and cultured in medium 199 for 2h at 37°C. Numbers of small (3·0 to 7·9 mm diameter) and large (>8·0 mm diameter) follicles were not significantly altered by any of the immunization treatments. Intrafollicular concentrations and secretion rates of oestradiol, testosterone, progesterone and inhibin, determined in vitro, were not affected by immunization. Intrafollicular IGF-1 concentrations were not affected; this hormone was not detectable in the culture medium. Intrafollicular concentrations of oestrogen and testosterone and secretion rates of all three steroids were greater (P < 0·05) in animals which had regressing corpora lutea at the time of ovariectomy. Of the animals that had dominant follicles, one of 17, one of 13, four of 19 and six of 15 in the C, A, I and AI groups, respectively, had two or more. Only the difference between AI and C cows in the incidence of dominant follicles was statistically significant (P < 0·05). Mean circulating concentrations of LH, and inhibin (C and A groups only) and mean LH pulse frequency and pulse amplitude were unaffected by treatment but FSH concentrations were higher in A (P < 0·001) and lower in AI and I heifers (P < 0·001) compared with C animals while IGF-1 concentrations were lower in A heifers (P < 0·001) and higher in AI heifers (P < 0·05) compared with C heifers. It is concluded that immunization against inhibin, either alone or in combination with immunization against androstenedione increased the incidence of multiple dominant follicles in heifers but did not increase their ovulation rate.

Two experiments, experiment 1 with six steers in a 3 × 3 Latin-square design and experiment 2 with four wether sheep in a cross-over design, were conducted to study the effect of species and ammonia treatment on intake and utilization of the energy of untreated wheat straw. Treatments were: (1) untreated wheat straw offered ad libitum on top of a basal diet (B) consisting of hay (0·25) and grass pellets (0·75) (UWS), (2) ammoniated wheat straw offered ad libitum plus B (AWS) and (3) ammoniated wheat straw offered at a restricted level plus B (AWS-). B was offered as a maintenance diet for both species and AWS- was only studied in steers. Voluntary intake of AWS zvas higher than that of UWS. No significant differences emerged between whole rations UWS and AWS with regard to energy digestion (ED), energy metabolizability (ρ = metabolizable energy (ME) I gross energy (GE)) and losses of digestible energy (DE) in urine and methane (average 187 J/KJ DE), but the efficiency of utilization of ME for growth (kg) was significantly higher for AWS than for UWS. ED and ρ of the straw part of the ration was significantly higher for AWS than for UWS. AWS- and AWS did not differ significantly with regard to ED, ρ and DE losses in methane and urine. Steers had a higher intake per kg0·75 per day than wether sheep. Across species, digestible energy intake (DEI) of the whole ad libitum fed diets was related to live weight (M)0·946 (s.e. of exponent 0·0152). ED and ρ of the straw part of the rations did not differ significantly between species, but steers had a significantly higher ED and ρ of β than wether sheep. Steers excreted a significantly lower proportion of DE in urine and a significantly higher proportion of DE in methane than did wethers. Total energy losses in urine and methane, however, did not differ between species.