Lactation in deer can last for longer than 300 days with natural weaning of calves occurring in the third trimester of the following pregnancy therefore mid-lactation coincides with mating. Lactation is a period of high nutritional demand for the animal as it maintains both its calf growth and prepares for reproduction. The management of feed supply (quantity and quality) available to the hinds at this time of year can therefore impact on both the incidence and timing of conception.
Research has shown that the body condition (BCS) of hinds during lactation has an influence on subsequent reproductive performance.
- Hinds with a BCS < 2.5 are less likely to conceive than those with BCS > 3 and this could result in up to a 10% difference in pregnancy rate.
- Hinds in very good condition (BCS = 4 to 5) will conceive up to 5 days earlier than those in poor condition.
- Pre rut weaning also increases the chance of early conception, most likely due to the cessation of lactation allowing hinds to improve body condition.
Farm management systems need to target hind performance over lactation to ensure high productivity levels. On farm, during lactation, summer pasture quantity and quality are both declining. For farmers the decision is a compromise that has to be made between better calf performance and hind condition during mating. Where high quality pasture is not available calves may do better when post-rut weaning is used, but, for the hind this may result in later calving and possibly lower conception rates.
Feeding targets during lactation
- Allow 4 to 5 kg DM/day/hind of high quality feed for hinds with red calves at foot. Hinds with Wapiti calves should be allowed an additional 1-1.5 kg DM.
- Pasture covers need to be 1800+ kg DM for lactating hinds to ensure they can access enough feed to avoid live weight loss in late summer.
- If possible consider utilising highly palatable species (e.g. forage herbs, etc) in late lactation (February) when pasture quality is low. This will encourage calves to increase intake (and hence growth rates), and assist in development of rumen function which will minimise setbacks at weaning.
- Introduce hinds and calves to new feeds before weaning so that calves will make the most of it after weaning.
- Pasture quality is generally highest in spring (ME 12) and of greatest variability in summer (ME 7-10) as pastures go to seed and lose quality rapidly (reproductive and dead material increases).
Young calf growth rates are most influenced by the hind lactation and therefore how well hinds are fed. Live weight gain in un-weaned calves ranged from 220 to 700 g/day in Jan/Feb (reported from farm trials, Deer Master, Lincoln and AgResearch Invermay trials). For further reading on growing calves faster.
In order to achieve calf growth rates of 400g/day+ both the hinds and the calves need:
- High quality feed > 10.5 MJ ME/kg
- Pasture offered > 2500kgDM/ha, to ensure high intakes
- More green leaf (> 60%) and legume/chicory (>15%)
Late lactation is a critical period to maximise calf live weight gain on farm by improving the quality of the feed on offer potentially through the use of specialist pastures or crops. On most properties quality of pasture on fawning paddocks is the limiting factor to live weight gain.