Browsing by Author "Langeveldt, Juanita"
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- ItemA comparison of Merino and Dormer rams in terms of mating dexterity and sperm subpopulations characteristics(Stellenbosch : Stellenbosch University, 2016-12) Langeveldt, Juanita; Lambrechts, Helet; Cloete, Schalk W. P.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.ENGLISH ABSTRACT: Assisted reproductive techniques (ART’s) play an increasingly important role in sheep farming systems to ensure the viability and cost-efficiency of production. Sperm quality is a major determinant of the successful application of ART’s, and therefore it is important to understand the factors that affect the viability and fertilizing ability of sperm. This study aimed to determine the influence of breed and genetic selection for reproduction potential on mating dexterity, sperm morphometric subpopulation characteristics and fertilizing ability. The technique used to collect semen samples can influence the quality of the sample, with the artificial vagina (AV) method yielding better samples than those collected by means of electro-ejaculation (EE). The use of the AV method requires the prior training of rams, and to date no standard operational procedure (SOP) has been formulated for the training of rams to use the AV. During the training of rams to use the AV, both inexperienced and experienced Dormer rams found mature Dormer ewes more attractive than yearling Dormers ewes, and in the training sessions the Dormer rams did not discriminate between Dormer and Merino ewes (in oestrus), that were used as teaser ewes to stimulate a sexual response in the rams. In contrast, Merino rams in this study were less discriminatory in their choice for either mature or yearling Merino ewes, with experienced Merino rams exhibiting a definite preference for a Merino teaser ewe. There was no conclusive evidence of a breed preference in inexperienced Merino rams. Breed and degree of sexual experience did not influence ease of habituation of a ram to the presence of the semen collector and/or assisting staff. Rams could be habituated within approximately 4 weeks and during a minimum of 8 training sessions when trained by experienced personnel. A higher frequency of training, i.e. 18 training sessions during this 4-week period will result in a more established baseline behaviour that will indicate whether a ram could be successfully trained to use the AV. There was no conclusive evidence that experienced Merino or Dormer rams ejaculated into the AV more readily, when compared to the Dormer and Merino inexperienced rams. It has to be noted that only 50% of the experienced Dormer rams could be successfully trained to use the AV, compared to 90% of the experienced Merino rams. Of the inexperienced rams only 40% of both the Merino and Dormer breeds could be trained to use the AV. Four distinct sperm morphometric subpopulations were identified in semen samples obtained from Dormer and Merino [High reproduction potential line (HL) and Low reproduction potential line (LL)] rams in this study. No significant differences were reported between the breeds in terms of ejaculate sperm subpopulation structure. The sperm subpopulation analysis of the HL and LL ejaculates indicated minor but non-significant differences between certain subpopulations. Breed or genetic selection had no influence on most post-thaw sperm parameters, except for post-thaw sperm viability that differed between HL and LL rams. A significant difference was observed between the sperm binding capacity of Dormer and Merino sperm. Sperm obtained from HL rams tended to have a better binding capacity than sperm obtained from the LL rams. No conclusive evidence of a correlation between sperm binding capacity and any sperm morphometric subpopulation was obtained. In conclusion, the factors contributing to the difficulty of training experienced Dormer rams, as well as inexperienced Dormer and Merino rams, to use the AV warrants further investigation. Future studies should further investigate the influence of breed and genetic selection on sperm subpopulation traits. Additional research to clarify the relationship between sperm subpopulations traits and the potential role of sperm competition in the determining the fertilizing potential of sperm, is warranted.