Effects of trypanosome inferction and postpartum liveweight change on resumption of reproduction activity in N'Dama cows

Data on reproduction, liveweight and trypanosome infection of N'Dama cattle raised under traditional husbandry systems in The Gambia were analyzed to quantify the relative effects of postpartum liveweight change and infection with pathogenic trypanosomes on 2 parameters of reproductive efficiency: the ability to calve within 21 months after the initial parturition and the length of the calving interval. Information for the study was obtained from a database on an epidemiological survey begun in 1985 in The Gambia. Calving records (n=294) from 3 locations were classified on the basis of body weight change and prevalence of trypanosome infection between 1 and 4 months postpartum. Least-squares analyses adjusted for effects of location, season of calving, viability of calf, and parity showed that the proportion of cows that calved within 21 months was 50% for cows which maintained or lost less than 5% of the initial postpartum weight and 31% for cows which lost a higher percentage of weight. Corresponding mean calving intervals were 567 and 666 days, respectively (P<0.05). With regard to trypanosome infection, 49% of uninfected cows and 32% of infected cows (P<0.05) calved again within 21 months, with calving intervals of 581 and 651 days, respectively (P<0.05). The interaction between liveweight change and trypanosome infection status was not significant. Furthermore, the findings suggest that while postpartum body weight loss impairs reproductive performance, trypanosome infection does likewise, and these effects may act independently of each other.