The aim of the current study were two fold; Firstly to establish the mechanism and timing of occurrence of fertility parameters associated with the onset of puberty and to investigate the effects, mechanisms and mode of action of restricted energy intake on growth rate, and age at puberty. Secondly, to study the effects of mating at different intervals post-partum on early fertility parameters and to identify the fertility parameters affected by early remating in three breeds of rabbits - the Local Cameroonian, the Californian and the New Zealand. The effects of two energy levels of intake on the onset of puberty were investigated. The results showed that restricted energy intake had no effect on mating behaviour but that, a critical level of oestradiol 17? was necessary to render the pituitary sensitive to GnRH following mating. It also revealed that the effects of nutrition on fertility parameters at puberty were mediated through the body weights achieved. Both a critical concentration of oestradiol 17? and another non-ovarian factor, probably of nutritional origin may be necessary for ovulation to occur. Experiment 2 provided data for pre- and post-implantation losses at different ages in does fed one of the two test diets. The results showed that after 19 weeks of age and above 1.8 kg body weight, growth rate had no effect on the proportion of does mating or ovulating and that, as does grew older there was an increase in metabolic resistance to restricted feed intake, whereby energy partitioning could have been altered giving preference to reproduction. Dietary energy intake had a negligible effect on corpus luteal function as reflected by progesterone profiles. The results also suggest that, most of the losses occurring prior to implantation were probably incurred during the very early period following mating (1-4 days), and were more likely to be related to fertilising ability than progesterone concentration. In experiment 3, the effect of altering the remating interval on early fertility parameters was investigated. Ninety-six does of the Local Cameroonian breed and 48 New Zealand white does were tested for mating 1, 7, 14, 21, 28 and 35 days post-partum one hour after blood samples had been collected to be analysed for oestradiol 17?. Does were slaughtered on the day of mating to assess the number of follicles of diameter > 1 mm and 2 days post-mating to assess ovulation response and rate. Receptivity increased with day of testing for mating post-partum with the highest response on day 1 and the lowest at 21 days post-partum. No correlation existed between follicles (> 1 mm) and day of mating post-partum. (r=0.03). Serum oestradiol 17? concentrations were not significantly different (p>0.05) on any day of mating, although the concentrations tended to be higher on day 1 post-partum. There was a te The overall results of this study reveal that besides the inherent reproductive characteristics of the doe rabbit, poor management practices as well as the high environmental temperatures characteristic of the tropics, could be responsible for the poor reproductive efficiency of the doe rabbit in Cameroon.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:593210 |
| Date | January 1997 |
| Creators | Ndoping, Beatrice |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU603185 |
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