Influence of calf genotype on dam lactation and calf growth in farmed red deer (Cervus elaphus)

Multiparous red deer (Cervus elaphus scoticus) hinds (n=17) were either mated to a red deer stag or artificially inseminated with semen from a wapiti bull (C.e. nelsoni) to produce red deer or F1 crossbred (C.e. scoticus × C.e. nelsoni) calves to test the hypotheses that (1) red deer hinds rearing crossbred calves will produce significantly more milk to support calf growth than hinds rearing red deer calves, and (2) hind live weight and body condition may suffer as a result. Hinds and calves were grazed on ryegrass and white clover pastures and supplemented with pasture silage and barley grain when pasture supply was inadequate. Calves were left with their mothers until 9-10 months of age when lactation had terminated naturally. Mean body condition score (BCS) loss was greater in hinds rearing F1 calves than in hinds rearing red calves in the period from late gestation to mid-lactation (September-March, P<0.05). F1 calves grew significantly faster than red deer calves and were heavier at all ages. From February onwards there was a consistent decline in milk intake, and by the latest measurement (22 July) milk production was negligible, and most hinds had ceased lactating. Milk intake by the F1 calves was significantly greater until day 114, after which the measured milk intake was not significantly different. Pasture intake of the F1 calves was significantly greater at day 114 but not at other times (P<0.05). The average hind pasture intake was also not significantly affected by calf genotype when adjusted for post calving hind live weight. The results support the hypothesis that a red deer hind rearing an F1 calf produces significantly more milk than a hind rearing a red deer calf, suggesting that the growth of a red deer calf is limited by its milk demand rather than milk supply by the hind. The study also supported the second hypothesis. Hinds rearing F1 calves exhibited greater losses of body condition score relative to the hinds rearing red deer calves, indicating that the hinds rearing F1 calves were in a greater negative energy balance that hinds rearing red deer calves. This highlights the additional energetic demands on a hind from feeding an F1 calf and in a farmed context the need to ensure that adequate nutrition is provided.