The results of two experiments designed to examine the effects of genetic and environmental factors on the liveweight growth and carcass composition of cross-bred lambs are reported. In the first experiment, data were available for the progeny of Dorset Down, lie de France, Oldenburg, Oxford, Suffolk and Texel sires out of Border Leicester * Scottish Blackface and ABRO Dam Line (5 strains) x Scottish Blackface ewes. Analyses were made for (a) growth traits to 12 weeks for 2585 lambs, the progeny of 102 sires; (b) growth traits to slaughter at fixed weights of 35 kg and 40 kg for 1884 lambs (79 sires); and (c) half carcass dissection traits for 956 lambs (65 sires. Sire breed, year, sex, rearing type, ewe age and other environ?mental factors significantly affected liveweight growth traits, percentage carcass composition and the distribution of dissectible lean tissue and subcutaneous fat between eight standard joints. Paternal half-sib estimates of the heritability of liveweight growth rates to slaughter were low (0.10 ? 0.06). Moderate heritability estimates were recorded for percentage lean in the carcass (0.41 ? 0.13), lean tissue and subcutaneous fat distribution. Estimates of the genetic and phenotypic correlations between traits are also presented. In the second experiment the range of sire breeds was extended/to include the Southdown and Cotswold. Data for 511 lambs, the progeny of 4 to 8 sires/breed and serially slaughtered at 13, 17, 21,25, 29, 33, 37, 41, 51 and approximately 63 weeks of age, were analysed using the allometric equation. Analyses of the growth of dissectible carcass' tissues relative to age, liveweight and side weight, of dissectible subcutaneous, intermuscular and kidney knob and channel fat relative to lean tissue weight, and of lean tissue relative to bone weight, are reported. In general, the effects of breed, year, ewe age, rearing type and sex upon differential growth patterns were not significant (P > 0.05). However, significant (P < 0.05) effects of sire breed and of environmental factors on intercepts are reported.

1. The literature review initially describes foetal and placental growth and development. The following two sections present the effects of nutrition before mating and in early pregnancy, concentrating mainly on the effect on ovulation and lambing rate, and identify the lack of information on the effect on foetal lamb growth and birth weight. 2. Aspects of nutrition, particularly during mid and late pregnancy are reviewed. The close relationship between energy and protein nutrition is recognised in relation to foetal growth. 3. Finally, an account of nutritional effects on lactation is given and again emphasising the role protein and energy have to play. Methods of assessing milk yield are also described. 4. The first experiment provided information on differences in maternal body composition, early foetal and placental growth and development brought about by high and low planes of feeding for ten weeks before mating and up till 90 days of gestation. The foetus weights were not different, but placenta and cotyledon weights were heavier ( p < 0.05) for better nourished ewes. Liveweights of ewes differed by 27 kg, but energy contents differed by 479 MJ, or poorly fed ewes had half the reserves of well fed ewes. 5. The second experiment provided information on changes in body composition as a result of high and low levels of nutrition before mating. Ewes received different amounts of protein and energy in late pregnancy. fiaternal body changes as well as thegrowth of foetuses and placentae were followed throughout this period. As in the first experiment the changes in energy were greater than would have been predicted from liveweight changes. Maternal composition was largely affected by treatment before mating. Lambs from ewes on high protein levels were approximately 1 kg heavier than lambs from ewes on low protein irrespective of energy level. Little effect was observed on the placenta as a result of treatment, but it increased in weight between 90 and 14-2 days of gestation. 6. The third experiment provided information on the effect of increasing increments of fishmeal inclusion in the concentrate ration on ewe weight, milk yield and lamb birth weight and growth rate. The milk yield and growth rate recording ceased after four weeks of lactation. There was a significant difference of about 2 kg in the weight of twin lambs from ewes receiving concentrates with 0.15 and 0.2 fishmeal compared with those receiving barley alone. By weaning, after grazing on pasture, no differences in lamb weight were evident. 7. The results are discussed, in the light of current research information and in relation to commercial practice.

Following reports that grazing lucerne and rape had produced flavour defects in lamb, the aim of this study was to determine if any of the fattening regimes for store lambs in the ESCA trials of 1977 produced unacceptable aroma or flavour in roasted gigots and loins. Careful studies of factors influencing meat flavour were made so that standardised procedures would ensure that feeding regime was the only variable in the trials. Hedonic rating scales were first used to determine optimal internal temperature for gigots and loins. Tasters at QMC and ESCA found difficulty in distinguishing samples cooked to different internal temperatures. Responses were inconsistent in duplicated trials. It was thus considered prudent to devise more precise assessment techniques for future studies. Triangle tests and paired comparison (preference) tests were subsequently used. In the first comparisons of grass and rape fed samples, there were no detectable differences in aroma or flavour. There was no consistent preference for either sample. Flavour profiles confirmed that neither feeding regime produced characteristic aroma or flavour. Tasters' performance was assessed. Results of these assessments indicated that the second series of comparisons of grass and rape and comparisons of the other forage crops could be carried out with greater confidence in both the experimental design and tasters' performance. None of the fattening regimes for store lambs produced detectable differences in aroma or flavour. There was no consistent preference for the flavour of lamb from any of the feeding regimes although there was some evidence that feeding cabbage produces flavour which is very well liked. There was no difference in the a b ility ofjudges to identify the odd sample in triangle tests when the aroma of raw and cooked samples was compared. This finding has considerable implications for future experiments. The contribution of fatty tissue to flavour was studied. Total and evaporative weight losses and raw and cooked pH values of gigots and loins were recorded. Statistically significant differences were established between the two cuts although pH changes in response to the cooking process did not differ. These findings emphasise the importance of comparing meats of standard anatomical location. An account of the basis on which the sensory tests used in the trials were selected is given together with details of statistical techniques used in the analysis of data.

Recent studies have established that abomasal and intestinal parasitic infections can reduce the growth and mineralisation of the skeleton of growing lambs. One possible cause for the skeletal effect is that the parasites induce a mineral deficiency by reducing the absorption of dietary Ca and P and/or increasing the endogenous loss of these two elements. The importance of these factors was investigated in this study, This was achieved by using growing lambs fitted with cannulae in the rumen, abomasum and ileum and infected daily with Trichostrongylus colubriformis larvae,Ostertagia circumcincta larvae or no larvae. The lambs were fed the complete diet Ruminant A and the flow rates were measured by reference to soluble and particulate radioactive markers. The endogenous fraction of Ca and P in faeces and digesta was measured by the method of isotope dilution involving a single intravenous dose of 32P and 45Ca. A preliminary investigation showed that the best method for calculating the fraction of Ca and p which is of endogenous origin was the area method using a two day delay and that the SR in plasma was more reliable than the SR in urine, 0. circumcincta infection was without effect on the absorption and secretion of Ca and p in the digestive tract, other than producing a small but significant increase in the endogenous faecal Ca excretion. There was, however, a striking increase in the flow of digesta at the abomasum,the DM and Ka content of which was consistent with an increased secretion from the mucus - type cells in the abomasal mucosa. The extra digesta was absorbed in the small intestine, T, colubriformis infections reduced the absorption of exogenous p by about 30% and increased losses of endogenous P due to the action of worms on the mucosa of the small intestine. The net effect of this v;as to induce a P deficiency in TC lambs leading to a reduced flow of salivary P and a reduction in the plasma concentrations of p. The effect of T, colubriformis on Ca metabolism was limited to an increase in endogenous faecal excretion.

The main aims of this study were 1) to describe the development of behavioural patterns in dairy heifers, 2) to investigate individual differences in behaviour and temperament, 3) to assess the temperament of each during milking and 4) to determine whether measures of early behaviour are related to temperament at a later age or to production measurements. Time based focal animal samples of twenty Friesian heifer calves over a period of two years recorded the activity of the calf and its nearest neighbour. A study of beef suckler calves reared with their dams was available for comparison of early development. The animals reactivity to being touched was tested approximately weekly and its temperament during milking was assessed. Data on liveweight measurements and daily milk yields were available. Development of the heifer's behavioural activities is shown graphically, either as proportion of time spent or frequency of occurrence. The development is considered in two ways 1)development in relation to chronological age, and ?_)development in relation to period of time within a particular rearing condition. However, the development was similar in both cases. Testing of the mean values of the activities for each separate rearing condition, normally experienced by dairy calves during their rearing, showed significant changes. Diagrams of significant sequential changes of activities show the development of the context of these behavioural actions. These results are compared with those obtained for field calves to indicate where environmental conditions may be affecting the development of the dairy calves behaviour patterns. The animals were then considered individually. Individual differences in the proportion of time spent in different activities was not consistent in each rearing period. The heifers social profile is represented by histograms of the frequency of expression of two categories of social behaviour, social licking and aggression. Associations between heifers, measured as the most time spent as its nearest neighbour, was only observed between a pair of twins. The reactivity of the heifers to being touched showed that most of the heifers were consistent in their reaction from an early age. Investigation of position within the herd and ease of entry to the parlour during the milking routine showed that heifers were recorded more often in the in the last third of milking group which was also associated with being pushed into the parlour by the dairyman. investigation of correlation between the behavioural measurements and between the behavioural and production measurements (i.e. growth rate of the heifers and the mean daily milk yield) is discussed. For the behavioural measurements, only the correlation between the frequency of initiating aggression and milking temperament was significant at p < 0.05 level. However, three other correlations approached significance i.e. correlation of proportion of time spent passively as a calf with frequency of initiating aggression, frequency of initiating social licking with proportion of times pushed into parlour and proportion of times pushed into parlour with milking temperament. This led to the hypothesis of a trend in the development of behaviour characteristics of dairy heifers. There appeared to be little relationship between the behavioural measures of the heifers and measures of their productivity with only the correlation between frequency of initiating social licking and mean daily milk yield reaching the p < 0.05 level of significance. Finally, a discussion of these findings in relation to theories of development(e.g. effect of environment, early experiences) and their implications for animal husbandry is presented.

Experiments were conducted to examine the impact of high milk yields on the behaviour and welfare of dairy cows. A preliminary study determined the social interactions existing within a group of 60 cows from which sub-samples of 20 high and 20 low yielding cows, that were not observed to interact with each other, were identified. These cows were used to examine the behavioural strategies employed by dairy cows coping with increased nutritional demands from milk production. Grazing time significantly increased with milk yield, consequently reducing lying time. A second study measured the appetite of high and low yielding cows for concentrates, using operant conditioning. The high yielding cows demonstrated no greater appetite for concentrates, but post-testing behavioural observations indicated greater appetite for forage, suggesting increased motivation to feed. Subsequent experiments investigated the behavioural effects of lying deprivation on dairy cattle welfare, further examining the feeding-lying conflict. Cows forced to stand had reduced milk yields and demonstrated behavioural signs of fatigue, frustration and stress, which were cumulative. When deprived of lying, a post-deprivation increase in this activity was achieved by reducing feeding time. When deprived of both lying and feeding, a feeding, not lying, post-deprivation increase was observed. However, lying was not reduced to extend feeding time. In conclusion, the motivation to feed was greater in high yielding dairy cows. This resulted in extended grazing and a reduced lying time. Lying can be regarded as an important and highly motivated behaviour and may compromise welfare if reduced. The legitimacy of using individual dairy cows as replicates in the statistical analysis of their behaviour was also investigated. There was no significant difference in the coefficients of variation between cows that were free to interact, and those that were not, for a range of behaviours. Therefore, those cows able to interact did not appear to influence each other's behaviour, supporting the use of individual dairy cows as replicates.

Methods of superovulation, embryo recovery and embryo transfer were adapted and developed for application to Welsh Black cattle in a Group Breeding scheme. Three methods of oestrus detection in early postpartum suckling beef cows were evaluated. None was entirely reliable although a probe for the measurement of the electrical resistance of vaginal mucus was the most effective and the least stressful. The postpartum interval to superovulation did not affect the responses to treatment. The effect of suckling on embryo quality from superovulated Welsh Black cows was investigated. Three groups of cows (one dry and two suckling) were superovulated and their embryos recovered in two seasons; summer and autumn. Significant effects of season (P=O.016) and suckling (P=O.015) on embryo quality were detected. Season significantly affected the number of viable embryos (P=O.004). There were no effects on ovarian responses or on the numbers of embryos recovered. Nutritional supplementation and the administration of heG failed to improve embryo quality. Examination of the data from three years of superovulation and embryo recovery revealed significant monthly variations in % viable embryos (P=O.006) and in the numbers of viable embryos (P=O.02) recovered. Embryo recovery was not affected by the catheter used or by the side of uterus being flushed. The number of pari ties of the donor affected the ovulation rate (P=O.009) and the numbers of embryos recovered (P=O.028) but not the embryo recovery rate (%). No differences were detected in the superovulatory responses of cows bred by 3 methods nor from the method of oestrus synchronisation. Embryo transfers were performed by surgical and nonsurgical methods. Fresh and frozen embryos were successfully transferred by the surgical technique but no embryos transferred nonsurgically continued development. A measurement of cervical diameter was successful in identifying animals which were unsuitable for non-surgical embryo transfer and recovery procedures. n-Alkanes as nutritional markers for intake estimation were applied'to cattl~ in a performance test and to cows at pasture. The results obtained indicate that the method may be useful in the future development of selection methodologies for beef cattle. The findings of both series of investigations are discussed in relation to beef cattle improvement through Group Breeding schemes.

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