Seasonal effects on semen quality in Black Baladi and White New Zealand rabbit bucks.

Abstract

A total of 32 sexually mature rabbit bucks (at 6th month of age) were used in this experiment to study the effects of breed (Black Baladi -BB- vs. White New Zealand -WNZ-) and season (summer vs. winter) on libido and seminal parameters. The experimental design was completely random with four groups arranged factorially (two breeds and two seasons) with eight rabbits in each group and three months per season. The results obtained from this study indicated that, libido (14.5 vs. 21.9 sec) and physical semen characteristics represented by the volume of semen per ejaculate without gel fractions (0.70 vs. 0.49 mL), sperm-cell concentration (703 vs. 597×106/mL), total sperm output (513 vs. 293×106/ejaculate), sperm abnormalities (11.6 vs. 14.0%), acrosomal damages (8.6 vs. 11.5%), dead spermatozoa (13.9 vs. 16.0%), and advanced sperm motility (63.2 vs. 57.1%) were signifi cantly (P<0.01) better on BB rabbit bucks than on WNZ breed. In addition, these parameters proved to be signifi cantly (P<0.01) better in winter season (15.8 sec, 0.68 mL, 702×106/mL, 487×106/ejaculate, 10.7%, 8.4%, 12.7%, and 65.6%, respectively) than in summer (20.6 sec, 0.52 mL, 598×106/mL, 319×106/ejaculate, 15.0%, 11.7%, 17.3%, and 54.7%, respectively). Following the hypo-osmotic swelling test (HOST) at 75 mOsmol/L during incubation at 37oC for 20 min, the percentages of sperm motility, swollen spermatozoa, and spermatozoa with coiled tails were higher for BB bucks (16.98, 44.08, and 39.13) than for the WNZ breed (7.2, 32.3, and 26.0). This was also the case in the winter season (14.4, 42.7, and 38.5) when compared to summer (9.8, 33.7, and 26.6), respectively. We concluded that, under Egyptian conditions, both libido and semen quality in BB bucks seems to be better than those displayed by the WNZ bucks. Nevertheless, overall semen characteristics were better in winter than in the summer season.