Assessment of selenium supplementation on the attainment of puberty in Merino ram lambs
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Date
2023
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Abstract
In small ruminants, the attainment of puberty is influenced by different factors, such as season of birth, photoperiod, nutrition, breed type, management, genetics, endocrine regulation, body weight and the development of the reproductive system. This study was conducted to evaluate the effect of selenium (Se) supplementation on the attainment of puberty in South African Merino ram lambs. Forty South African Merino ram lambs were divided into two groups, Se-supplemented (n = 20) and control (n = 20). The treatment group received a dosage of 0.34 mg Se per kg in the form of sodium selenite at two-week intervals for an experimental period of 130 days. The phenotypic parameters were evaluated weekly. Semen was collected each week using an electroejaculator and was analysed for volume, pH, appearance, motility, viability, morphology and concentration. Blood samples were collected bi-weekly to determine the concentration of glutathione peroxidase (GSH-Px), cortisol and reproductive hormones. Collected data were analysed using analysis of variance, and the means were separated through the Student’s t-test. At 6 months, motile spermatozoa were collected from 80% of the supplemented group compared to 60% of the control. The Se treated group showed significantly higher semen quality in the form of improved spermatozoa motility, concentration, increased percentage of live spermatozoa, decreased percentage of dead spermatozoa and fewer spermatozoa abnormalities compared to the control group. Supplementation with Se had no effect (P > 0.05) on body weight and scrotum circumference. Selenium supplementation significantly (P < 0.05) improved testicular measurements and decreased the age to attain puberty. Supplementation with Se also increased luteinising hormone and testosterone concentrations (P < 0.05). However, Se supplementation did not affect glutathione peroxidase and cortisol concentrations (P > 0.05). The control group attained puberty at 6.5 months based on ejaculated semen with viable spermatozoa. Therefore, it was concluded that Se supplementation hastened the attainment of South African Merino ram lambs’ puberty to 6 months. Treatment also improved testicular measurements, semen quality and reproductive hormones concentration of South African Merino ram lambs.
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A dissertation submitted in fulfillment of the academic requirements for the degree of Master of Science in the Department of Agriculture in the Faculty of Science, Agriculture and Engineering, University of Zululand, 2023