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University of Zululand (2015)

The characterisation of semen from Zulu Rams raised under extensive management conditions in KwaZulu-Natal

Chella, Lisa Coelleen

Titre : The characterisation of semen from Zulu Rams raised under extensive management conditions in KwaZulu-Natal

Auteur : Chella, Lisa Coelleen

Université de soutenance : University of Zululand

Grade : Master of Science (MS) in Agriculture (Animal Science) 2015

Résumé
The Zulu sheep is an Nguni breed indigenous to the KwaZulu-Natal (KZN) province in South Africa, and is reported to be under threat of extinction. Studies investigating the factors that may be the cause of the declining numbers are required for the strategic planning of conservation programmes. The study was designed to evaluate some of the factors viz. ram age, season and geographic location, that influence reproductive performance in Zulu sheep populations based on the viability of Zulu ram semen. Spermiogramic parameters used to assess quality were : scrotal circumference (cm) ; semen volume (ml) ; semen pH ; sperm concentration (x109), progressive and mass motility (%), and percentages of live and abnormal spermatozoa. Semen samples were collected via electro-ejaculation and analysed using a microscope while the scrotal circumference was measured using a flexible measuring tape. All data was analysed using the statistical software SPSS version 22. The average semen volume (ml) per ejaculate was 0.66, 1.11, 1.19, 0.82 and the sperm concentration 1.69, 2.79, 3.12, 3.07 (x109) for summer, autumn, winter and spring, respectively. The effects of age on all parameters were significant except for pH. There was a positive correlation between age and semen volume, concentration and semen colour. The values of volume, concentration, motility and live sperm increased linearly up to 3 years of age. Scrotal circumference and live spermatozoa were comparatively higher for rams at 3 years of age than at 4 years of age, while the values were the same at 1 and 2 years of age. The percentage of abnormal spermatozoa decreased down to 3 years of age, thereafter increasing from 4 years of age. The semen quality improved at 3 years of age and thereafter decreased. The effects of season on semen quality positively correlated in some of the geographic locations. For conservation purposes it would therefore be more efficient to select breeding sires from among the 3 year old rams for the autumn and winter breeding programme.

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