Voluntary food intake of pregnant and non-pregnant red deer hinds

Efficient farmed venison production under New Zealand lowland conditions requires early calving to better align lactation with pasture availability. However, hinds that conceive early in the breeding season have a longer gestation length than those conceiving later, negating some of the gains achieved by early conception. This variation in gestation length may relate to seasonal imbalances in hind nutrient uptake influencing foetal growth. However, little is known about food intake cycles of pregnant hinds and whether they exhibit the photoperiod-induced voluntary food intake (VFI) reduction over winter seen in younger age classes and adult stags. This study investigated the effect of pregnancy status on VFI of red deer hinds. In addition, concentration of leptin and ghrelin circulating in the body was measured throughout the study to ascertain if these hormones are indicative of hind energy status. Seven pregnant (P) and seven non-pregnant (NP) hinds were housed indoors in individual pens from April to November where they were offered daily an ad libitum pelleted ration. On average, P hinds gained 75 g/day and NP hinds lost 27 g/day (P=0.02) in autumn. Mean live weight (LW) of both groups then steadily increased for the remainder of the study with no significant difference between groups. Mean body condition score (BCS) change of P and NP hinds was similar in autumn and winter, but whereas that of P hinds decreased in spring, that of NP hinds increased (P=0.02). Pregnancy status of the hinds had no significant effect on mean VFI throughout the trial except for the last 5 days before parturition when VFI of P hinds decreased dramatically (P=0.001). VFI of both groups of hinds was significantly higher in autumn (P=0.03) and spring (P=0.01) than in winter and for every 0.1 MJME/kg LW0.75/day increase in mean VFI during the study period, gestation length decreased by 6.4 days (r2=0.51; P=0.04). Pregnancy status had no significant effect on plasma concentration of either leptin or ghrelin at any of the sampling times and there was no significant association of either leptin or ghrelin with VFI. However, leptin plasma concentration was positively associated with BCS (r2=0.41; P=0.008). This study showed that VFI of pregnant hinds was depressed during winter and early spring, and was negatively associated with gestation length. A reduction in BCS of pregnant hinds indicated that they were in a moderate energy deficit during the final third of gestation.