School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemSupplementation during late pregnancy and early lactation in dairy goats( 1990)An experiment was conducted at Mt. Derrimut Field Station from February 1988 to October 1988, to study the effect of feed supplementation at different times during late pregnancy and early lactation on milk production and litterweight of dairy goats. The experiment compared milk production and composition, litterweight and nutrient intakes of two groups of goats. Group A were supplemented with urea molasses mainly during late pregnancy (6 weeks before parturition continued for 3 weeks in early lactation). Group B were supplemented with urea molasses, mainly in early lactation (2 weeks before parturition continued for 7 weeks in early lactation). The feed supplement comprised 3.5% (w/w) urea in molasses given at a rate of 20% (w/w) of intake of basal diet dry matter. Basal diet comprised of a 50:50 mixture of chopped lucerne hay and oaten chaff. The basal diet and feed supplement were offered at a level of 25% above the }intake and given three times a day. A Mineral vitamin supplement at rate of 2% of feed offered was included. The results showed that there were no significant differences (P > 0.05) in litterweight , milk production or nutrient intakes throughout the experiment. Litterweights were 6.7�8.1 kg (group A) and 8.2�1.4 kg (group B). Litter size was not significantly differed (P > 0.05) between group A and group B (1.8�0.8) vs (2.3�0.5), therefore, birthweight was also not significantly differed i.e. 3.6�0.7 kg vs 3.5�0.4 kg for group A and group B, respectively. Milk production was 2.5 kg/d for both groups. Intakes of dry matter were 1731�395 g/d (group A) and 1831�525 g/d (group B). Between physiological stages, however, there was a significant difference (P < 0.01) in intake of nutrients. In early lactation intake of nutrients was higher than during late pregnancy. It was concluded that different timings of provision of supplementation during late pregnancy and early lactation did not make any difference in milk production, since greater number of foetuses hampered intake of nutrients during late pregnancy resulted in poorer body condition at birth. A positive energy balance in early lactation was utilized to recover body losses during pregnancy, but not for milk production.
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ItemCytogenetic sex determination of embryos( 1990)The purpose of the research presented in this thesis was to establish a rapid method to allow the cytogenetic determination of sex in sheep embryos. A simplified air-drying technique to allow cytogenetic sex determination initially established in mouse embryos. These techniques were then applied to sheep embryos. The techniques involved treating embryos with three types of fixatives :- fixing solution, softening solution and drying solution. Methanol : glacial acetic acid
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ItemEffect of GnRH and production levels on reproduction in dairy cattle( 1990)At 11-13 days after insemination, 1028 dairy cows on 19 farms were treated with an intramuscular injection of 10 ?g of the GnRH analogue Buserelin. Reproductive performance was compared to 1022 control cows receiving a placebo. Cows treated with the GnRH analogue had a reduced number of short interoestrus intervals compared to control cows but there were no significant differences in pregnancy rates to the insemination preceding or following treatment. Calving-to -conception intervals and percent pregnant by the end of mating were also unaffected. There were no differences between treatments in herds of high, average or low pregnancy rates, within different age groups or within different calving to first service intervals. The evidence here suggests that the use of 10 ?g of the GnRH analogue, Buserelin, 11-13 days post-insemination cannot be recommended as a method of improving reproductive performance in dairy herds.