No description available.

No description available.

Performance and progeny tests were carried out between 1975-1977 to obtain estimates of genetic variation in the growth rate of artificially reared Suffolk ram lambs both between and within flocks. It was found that there was individual variation in rams' breeding value and moderate heritability estimates of growth rate were obtained. Two further experiments were designed to investigate a problem arising from the performance test of 1975, when 24% of the sires failed to mate with ewes when they were introduced to them for the first time. The objectives of the first experiment were to investigate the effects of method of rearing and female company on the attainment of puberty. The second experiment was designed with the additional objectives of investigating whether early weaning of naturally reared ram lambs could provide an alternative to artificial rearing from birth. The effects of repeated pen libido and semen tests on sexual performance and semen traits were also investigated. The results obtained indicated that lambs which were either artificially reared, or naturally reared, but early-weaned at two months of age, attained puberty at an earlier age than those reared naturally with their dams to six months of age. It was also found that repeated libido testing significantly improved sexual performance in terms of number of mounts and number of ejaculations achieved within the 20-minute test period.

Two sheep group breeding schemes were considered in this study to examine the genetic progress made over a 20 year period and the success of running such schemes in practice. The data were records of lamb weaning weight in the CAMDA scheme (Welsh Mountain breed) and the Lleyn scheme (Lleyn breed), collected between 1976 and 1996. After the edits, a total of 31,161 records for the CAMDA and 29,090 records for the Lleyn scheme were available for the analyses. The estimates of the heritability of weaning weight for individual flocks were low to moderate. In the CAMDA scheme, the estimates of the direct and maternal heritability values ranged from 0.04 to 0.43, and 0.03 to 0.11, respectively. The ratio of temporary environmental variance over the total variance ranged between 0.13 to 0.35. The estimates of total heritability values in flocks of 12 and 18 weeks of age were in the range of 0.23-0.45 and 0.07-0.18, respectively. In the Lleyn scheme, the estimates of the ratio of temporary environmental variance over the total variance, and the direct and maternal heritability values ranged from 0.15 to 0.39, 0.03 to 0.31, and 0.04 and 0.23, respectively. The estimates of the total heritability values in individual flocks of the scheme ranged from 0.07 to 0.33. The differences in heritability values between the flocks, reflected the differences in the model of analysis fitted, and size and structure of the data available for individual flocks of the scheme. It is concluded that group breeding schemes are a viable means of improving the production of traits of a breed, but that more attention should be paid in the setting up of the schemes, to a scoring system which will accurately reflect the market value of the stock. The application of group breeding schemes in Iran would require taking account of the differences in the social and climatic environments. Much greater attention would be needed to determine the selection objectives and these would need to be properly included in the selection index.

The phenomenon of seasonability of reproduction restricts the ewe to only one lambing around the same time every year, which in turn prevents an even supply of lamb meat to the market. The long term objective of the current study was to develop two systems of early and summer lambing using alternative techniques for the manipulation of sheep production in an attempt to produce high quality lamb throughout the year. In recent years, major advances in our knowledge of seasonality of reproduction have been the recognition of the integral role of the pineal gland and its indoleamine melatonin in the timing of reproductive activity and the use of the pattern of reproductive behaviour in sheep in the manipulation of reproductive processes. Therefore, the current study aimed at examining the use of melatonin and/or the 'ram effect' in early and summer lambing systems in order to report on their effectiveness in advancing the breeding season and/or enhancing fecundity. Also, the concern over the seasonal variation in libido and semen quality in the ram made it necessary to examine ways of eliminating the seasonal depression in the mating performance and capcity of the ram. Experiments 1, 2 and 3 examined the effectiveness of the intraruminal device of melatonin administration and/or the 'ram effect' in advancing the breeding season of the ewes. Also the effects of duration and methods of 'teasing' were assessed.

No description available.

This work describes, by means of evidence from the literature, the problem of pre-weaning piglet mortality and shows that the major cause of loss is malnutrition. It is proposed that by housing the piglets from soon after birth in a near optimal environment and providing adequate nutrition then a high proportion of losses could be reduced. From evidence presented in the literature, the requirements of the piglet for nutrition, protection against infection and environmental factors were determined. A 2 stage system of artificial rearing was developed to meet these requirements. In Stage 1, the piglets were individually housed from 6 hours of age in pens with a heated floored lying area, a mesh floored mucking area and a feeding bowl protected by a mechanical gate. Automated feeding equipment delivered hourly to each piglet a measured amount of liquid diet based upon cow colostrum and whole milk powder; after each feed the entire system was cleansed. At 3 kg liveweight, the pigs were housed in Stage 2 in tiered cages in pens of 5 and fed on commercially available dry diets based upon milk pellets until 8 kg liveweight when a gradual change to cereal based pellets followed. At 12 kg liveweight, the pigs were transferred to the normal farm accommodation. The successful preliminary trials led to the development of more accurate and reliable liquid feeding equipment, which was used in controlled experiments to determine which combination of dietary components and environmental temperatures best suited the system. Improved Stage 2 cages were developed which incorporated heated floors and these were compared with the tiered cages. The components found suitable were combined into a system and these were tested under controlled conditions to determine if piglet mortality could be reduced in the sow herd. The successful results were evaluated and a system suitable for commercial application described.

The aim of the work was to study whether the stimuli of osmotic pressure (OP), or volatile fatty acid (VFA), or pH to the omasum would affect feed intake (DMI) and the passage of digesta from the reticulo-rumen. The technique adapted was to infuse solutions of different OP, VFA concentrations or pH into the omasum or abomasum via permanent catheters. Rumen digesta outflow was measured by means of markers pulse dosed through and sampled from a rumen cannula. A total of eight experiments were carried out. In the first series (1-3) one sheep and in the second series (4-8) three or four sheep were used. Latin square or change over designs with one days measurement at three or four day intervals were used. The main measurements taken were of daily and two hourly feed intake, ruminal solid and liquid outflow rates and volumes (solid, Cr-mordanted hay; and liquid, Co-EDTA or PEG) and water intake. Diet digestibility, serum OP, urine and faeces output and rumen OP, VFA and pH were also measured. Ruminal samples were collected at 2h intervals for 24h. Feed intake, solid and liquid outflow rates from the reticulo-rumen were (not always significantly) reduced by increasing the OP of the infusate in the range 400 to 2000 mOsmol/kg which gave calculated omasal OPs up to 480 mOsmol/kg (perfect mixing of digesta assumed). Feed intake and fractional ruminal liquid outflow rate were significantly increased with VFA concentration of infusate in the range 50 to 250 mMol/l (calculated omasal VFA up to 150 mMol/l) with suggested decreases above this range. pH in the range 5.0 to 7.0 was without effect. Serum OP was not affected by any infusate. Faeces output on the day of infusion decreased in some cases. There was no or only a weak response to abomasal infusion compared with omasal infusion when the same infusate was used. The study demonstrated that the omasum responds to changes in the composition of digesta. Increasing OP reduced DMI and reduced digesta outflow from the reticulo-rumen. Increasing VFA concentration increased DMI and liquid outflow rate and decreased DMI and liquid outflow rate with high VFA concentration. It is concluded that the omasum has a role in the control of digesta outflow from the rumen.

This study was designed to assess the effects of amino acid supply and growth hormone (GH) treatment on IGF-I gene expression of ovine hepatocytes and to determine the possible mechanism(s) involved. Using a riboprobe that detect both type 1 and type 2 mRNA transcripts, GH and amino acid were shown to have separate and interactive effects on the regulation of IGF-I gene expression and these effects were similar for both transcripts. The stimulatory effects of GH and amino acid supply were shown to depend at least in part on transcriptional control, since transcription blockade resulted in the abolition of both the GH and amino acid dependent responses. The effect of amino acid supply could not be attributed to any single amino acid (so far studied). However, partial effects of methionine and the branched chain amino acid limitation on GH dependent IGF-I mRNA expression were observed. Also methionine limitation caused the abolition of GH dependent IGF-I peptide secretion. The observed effects of amino acid supply on IGF-I gene expression were not dependent on the mTOR, PI3 kinase or MAP kinase pathways. However, GH dependent IGF-I peptide secretion was apparently PI3 kinase and MAP kinase sensitive. In conclusion, IGF-I gene expression is highly sensitive to GH and amino acid supply. The mechanism by which amino acid supply regulates IGF-I gene expression is mTOR independent. GH appears to regulate IGF-I production at the gene expression level, and also possibly at a translational/post-translational level through a PI3 kinase and MAP kinase dependent mechanism which may be methionine sensitive.

No description available.