Effect of L-carnitine supplementation to bulls on sperum motility maintenance under high environmental temperatures

L-carnitine plays a pivotal role for shuttling process of long chain fatty acid into mitochondrial matrix that eventually promoting lipid catabolism to produce ATP. This study aimed to evaluate some effects of L-carnitine supplementation to bull on its sperm motility under high environmental temperature. Prior to experimental feeding, a preliminary test of spermatozoa was conducted. Six Holstein bulls with the same sperm motility were divided into 2 groups; a control group and an experimental group supplemented with L-carnitine. Feedstuff and feed amounts for bulls in both groups were the same, however feedstuff for the experimental group was supplemented with 0.9g/d L-carnitine, with a final concentration of 50 ppm. Experimental feeding began on 1 August and ended on 30 September. Experimental semen collection was carried out twice on 5 and 30 September. In addition, motility of thawed sperm was observed in order to recognize the effect of L-carnitine supplementation on freezing. For the first semen collection, the mean value of sperm motility was ca.10% higher in the experimental group than that in the control group. For the second semen collection, the mean value of sperm motility was also ca.15% higher in the experimental group than that in the control group. Significant differences were not recognized in both data. Present results suggested that the supplementation of L-carnitine recovers a course of energy metabolism reduced by the high environmental temperature. L-carnitine supplementation halted the reduction of sperm motility due to heat stress. This tendency was especially noticeable in the results of sperm motility in frozen semen kept in liquid nitrogen. It appeared that the decrement in sperm motility observed in high environmental temperatures was due to the difference of sperm maturity. The ratio of abnormal sperm in the experimental group was less than that in the control group. L-carnitine supplementation to bulls plays a favorable role in the maturity of sperm while sperm motility is maintained at its usual level under high environmental temperatures.