The effect of nutritional stress on sperm motion characteristics and sexual behaviour of rams in a semi-arid tropical environment

Abstract

A major problem in sheep rearing is scarcity of feed during the summer and winter in semi-arid tropics. A study was conducted to assess the sperm motion characteristics and sexual behaviour of Garole x Malpura x Malpura (GMM) rams subjected to nutritional stress. Eighteen adult GMM rams were randomly allocated into three groups of six animals each: G1 (control; fed maintenance requirement), G2 (fed 20% less than maintenance) and G3 (fed 30% less than maintenance). The animals were stall-fed with a diet consisting of 70% roughage and 30% concentrate. The study was conducted for eight weeks during the spring. Semen collection was done weekly at 08:00. Semen was evaluated by a computer-assisted sperm analysis technique. Sexual behaviours were also recorded at the time of semen collections. The proportion of rapid, medium and slow motile sperm, and average path velocity varied significantly (P < 0.05) among the groups. The time for seeking females significantly (P < 0.05) decreased in G3, while the refractory period significantly (P < 0.05) increased in G2. The testosterone concentration was significantly (P < 0.05) lower in G2 and G3 as compared with G1. The results indicate that GMM rams compromised their reproductive performance under nutritional stress imposed by 30% feed restriction of their maintenance diet during a feed scarcity period.