The potential feed intake of animals is determined by physiological state (e.g. pregnancy, lactation, sex) and genetics. The animals’ health and the feed offered determine whether the potential is reached.
Red deer exhibit strong seasonal responses to day length (photoperiod) meaning changes in food intake and subsequently live weight gain throughout the year. In general these are: low intake and low liveweight gain in winter (short daylength) and high intake and liveweight gain in summer (long daylength).
Figure 3 Predicted mean daily voluntary food intake of pregnant and non-pregnant hinds relative to day length (hours between sunrise and sunset) during indoor feeding.(Scott, I.C., Asher, G. W., Barrell, G.K., Juan, J.V. (2012).
Intake is also influenced by the amount of pasture offered to the animal. In all seasons, liveweight gain increases with increased pasture availability, up to 6-8 kg DM/hd day offered. This is about the same as a post-grazing residual of 1500-1600kgDM/ha or 8cm. The more that is offered, the more that can potentially be eaten, up to a maximum where increased available pasture dry matter has no more influence on intake and liveweight gain.
However, increasing pasture allowance does not compensate for the seasonal differences in intake and liveweight gain expressed by the animals. The feed intake and liveweight gain of red deer are also sensitive to pasture quality which is influenced by the time of year.