Animal Science Abstract
Monthly variations in some reproductive parameters of Barki and Awassi rams throughout 1 year under subtropical conditions 1. Semen characteristics and hormonal levels
T. A. Taha1, E. I. Abdel-Gawad2 and M. A. Ayoub3
1Animal Production Department, Faculty of Agriculture, Alexandria University, Alexandria, Egypt2Animal Production Research Institute, Ministry of Agriculture, Cairo, Egypt
3Department of Animal Production, Faculty of Agricultural Sciences, UAE University, PO Box 17555, Al-Ain, United Arab Emirates
Abstract
Fifteen sexually mature rams, five each of Barki, Awassi (I, imported from Syria) and Awassi (LB, locally born in Egypt) were used in this study. Semen was collected monthly from rams for a period of 12 months to study semen characteristics. In addition, blood samples were collected from rams during the four seasons of the year to determine serum triiodothyronine (T3) and testosterone hormones. Results showed that Barki and Awassi (I and LB) rams are continuous breeders as they show sexual desire and produce semen all the year round. However, monthly variations in semen quality were detected. Relative testes volume, ejaculate volume, sperm concentration, total sperm output, sperm motility, percentage of live sperm and serum testosterone level were higher during summer months than at other months of the year. Serum T3 was significantly higher in winter and spring than that observed in summer and autumn. In addition, percentages of dead spermatozoa were higher in winter and early spring than in autumn and summer. Furthermore, summer months showed moderate percentages of abnormal spermatozoa and spermatozoa without intact acrosomes. These results indicate that ram semen quality in the subtropics may be better during summer months than during other months of the year.
Keywords: hormones, seasonal variation, semen characters, sheep
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