Predicting the energy and protein requirements of the pregnant grasscutter (Thryonomys swinderianus, Temminck) using the changes in weight and composition of the foetus and associated tissues of pregnancy.

Eighteen (18) gravid uteri collected from hunters' kills during February and March 2008 were used to investigate growth and accretion of energy and protein in the gravid uterus during pregnancy in the grasscutter. Each gravid uterus was separated into foetal, placental, empty uterus and foetal fluids (amniotic and allantoic fluids combined) components. Individual tissues were weighed and analyzed for dry matter (DM), ash, crude protein (CP) and crude fat. Regression equations were fitted to the weights of each component to describe the effects of gestational age. The DM, protein and energy contents of individual uterine tissues, with the exception of the DM of the foetal fluids, increased significantly with advancing gestation age so that the DM of the gravid uterus increased ~20-fold from days 45 to 152 (3.85 v. 76.24 g). However, the average elemental N in the foetus was 8.3 g N/100 g. Percentage DM did not change with advancing gestation age. Fat content of the foetal grasscutter was 2.79 %. Changes in foetal protein and energy fitted a multi-phasic regression that consisted of two linear equations. Similarly, changes in foetal fat and water contents fitted a multi-phasic regression that consisted of two linear equations, indicating that protein and energy growth accelerated after days 95 and 97 of gestation, respectively, with increases in fat and water accelerating after days 127 and 96 of gestation, respectively. Foetal protein and energy accretions were 0.04 g day(-1) and 0.001 MJ day(-1) before days 95 and 97 of gestation, respectively, and increased to 0.31 g day(-1) and 0.009 MJ day(-1) after days 95 and 97 of gestation, respectively. Fat and water accretions were also 0.012 g day(-1) and 0.15 ml day(-1) before days 127 and 96 of gestation, respectively, and increased to 0.104 g day(-1) and 1.29 ml day(-1) after the respective days of gestation. Protein needs for tissue protein gain increased ~8-fold after day 95 of gestation. Results of this study indicate that the growth of the foetus and foetal tissues occur at different rates during gestation and points to a two-phase feeding strategy before and after day 95 of gestation for pregnant grasscutters.