Effect of Gonadotropin-releasing hormone (GnRH) analogue on semen characteristics of three ecotypes of Tanzanian native chickens

Abstract

The effect of hormone treatment on semen quality characteristics and reproductive performance in male animals has been studied extensively. However, limited information is available on effect of Gonadotropin releasing hormone (GnRH) treatment on semen characteristics in galliform species. The aim of this study was therefore to examine the effect of synthetic GnRH on semen characteristics in three ecotypes of Tanzanian native chickens. A total of thirty-six mature cockerels (Ching’wekwe, Morogoro-medium and Kuchi ecotypes) were used in this study. Thirty cockerels (ten from each ecotype) were intramuscularly injected with 10 mcg (0.2 mL) of GnRH (Factrel®) once a week for five consecutive weeks. Six cockerels (two from each ecotype) were used for control purposes and they were given 0.2 mL of normal saline solution. Semen was manually collected at weekly interval by abdominal massage technique immediately after last GnRH injection for five consecutive weeks. Results showed that respective semen quality characteristics including semen volume, sperm motility, sperm concentration, proportion of morphologically normal and live spermatozoa increased significantly (p<0.05) in the treatment group (0.55±0.02 mL, 80.02±0.30%, 4.80±0.14 × 10⁹ sperm cells/mL, 91.25±0.3%, 91.65±0.31%) when compared to the control group (0.48±0.02 mL, 74.90±0.76%, 4.04±0.18 × 109 sperm cells/mL, 87.58±0.43%, 89.05±0.55%). Variations in semen pH between treated and control group was not significant. In conclusion this study indicates that semen quality characteristics can be improved by administration of GnRH to cockerels for increased semen quality characteristics and therefore increasing productivity in the poultry industry.