Peri-natal (around the time of birth) and post-natal (>24 hours after birth) mortality of calves is the single biggest source of reproductive wastage occurring on NZ deer farms, accounting for about 8% of calves born (see Reproductive Wastage). While it is recognised that there will always be losses around calving, there are ways to reduce overall calf mortality…often this just requires simple on-farm changes in management and calving environments.
Why do hinds need a good calving environment?
A significant proportion of calf losses occur because the calving environment is suboptimal for the needs of all individuals within the herd…this relates to the specific behaviour of hinds around the birthing process.
Hinds approaching birth seek isolation from their herd-mates and actively search for a suitable calving site. Such search behaviour is often seen as fence-line pacing starting 24-48 hours before birthing starts. Typically the hind will seek an elevated position with good ground cover as the preferred calving site (e.g. tussock slopes)…this affords good visualisation of the surrounding terrain as well as shelter for the calf.
When such calving environments are in short supply there can be considerable competition between hinds for prime sites, leading to conflicts in which the dominant hinds prevail…this is especially the case when several hinds are at the same pre-calving stage. Sub-ordinate hinds that fail to secure a good calving site often become stressed…and this can lead to a disrupted birthing process, three consequences of which are….
- The hind fails to adequately bond with its calf within the first few hours of birth, leading to calf abandonment. This results in the calf dying of starvation and dehydration 2-3 days later…typically wandering around the paddock crying out for mum.
- The actual birthing process is disrupted, forcing the agitated hind to move around while calving. This can lead to a difficult birthing process that causes fatal damage to the newborn (often stillborn) calf…termed ‘dystocia’. Typically affected calves are dead at birth or die within a few hours.
- In some cases the birthing goes to plan but the calf has insufficient cover in which to hide…especially if it is disturbed (e.g. by other hinds seeking a good birthing site). Such calves tend to wander in search of suitable cover, and can become the victims of misadventure…especially getting lost outside the birth paddock or getting entangled in fences.
What is the ideal calving environment?
Consideration to providing hinds better calving paddocks can pay big dividends by improving calf survival. Key points are as follows:
- Keep hind stocking rates reasonably low (<8 per ha) over calving to minimise competition over the birthing period. If the hinds are likely to have a highly synchronised calving (e.g. from artificial insemination programmes) it is important to further reduce the stocking rate to <4 hinds per ha until the birthing period is finished.
- Design calving paddocks around the provision of suitable cover particularly provision of shade for calving, calf security and protection from the weather. Sometimes these may seem to be the ‘roughest’ paddocks due to the presence of shrubs, tussock, rocks, gulleys, etc, but actually contain ideal birthing sites. However, there is also a need to provide lactating hinds with high-quality pasture to optimise calf growth…if this is compromised by the use of low-productivity ‘rough’ land for calving, a strategy is required to give hinds access to better pastures after birth (e.g. as simple as opening the gate to a better paddock next door).
- If ‘rough’ calving paddocks are not available (e.g. on intensive lowland farms) it may be necessary to create calving sites and calf hide-out sites. For example, leaving un-mown or un-grazed strips of long grass in the middle of the intended calving paddocks can provide a better calving environment. However, it is recommended that such strips should be sited away from fence-lines to reduce the temptation for calves to go through fences.
- Minimise outside disturbance during and immediately after calving (e.g. no dogs in the calving paddock). Such disturbances can be particularly devastating when hinds are birthing...if they prematurely leave the newborn calf there is a danger that the maternal bonding process will be disrupted.
For more details around causes of calf mortality see Reproductive wastage.