Reproductive wastage is a significant economic burden on the New Zealand deer farming industry. However, the extent of wastage among breeding herds is often clouded by inappropriate terminology and misuse of statistics. This leads to confusion about the true sources and causes of wastage. For example, while many producers refer to ‘calving rate’ as their ultimate measure of hind output, they are often actually referring to ‘weaning rate’. The former refers to calves born per capita of hinds present (at mating or calving) while the latter refers to surviving calves weaned per capita of hinds present.
Why do we need accurate benchmarking?
There is often the assumption that ‘dry’ hinds failed to conceive when they may have actually lost calves at or after birth. This is further complicated when management strategies include the culling of non-pregnant hinds at or shortly after ultrasound scanning, thus skewing the stated ‘calving rate’ of the remaining herd relative to the base herd present at mating.
Thus we have a scenario where there is a lack of interpretable or directly comparable data and confusion about true sources of reproductive wastage across our farmed deer herds.
How can we improve reproductive benchmarking?
The adoption of standardised terms and definitions will go a long way in reducing confusion.
We suggest use of the following definitions when recording breeding hind performance.
- Early pregnancy rate: Percentage of all joined (i.e. put with stag) hinds scanned pregnant by rectal ultrasonography within the first trimester (third) of pregnancy (i.e. May-July).
- Late pregnancy rate: Percentage of all joined hinds scanned pregnant by flank ultrasonography within the third trimester of pregnancy (i.e. September-October).
- Foetal wastage rate: Difference between ‘Early pregnancy rate’ and ‘Late pregnancy rate’ (provides an estimate of foetal mortality (e.g. through abortion or resorption)).
- Calving rate: Percentage of all joined hinds delivering calves (whether calves survive or not).
- Calf mortality rate: Percentage of all calves born that die within 3 months of birth (i.e. March; pre-rut weaning).
- Weaning rate: Percentage of all joined hinds presenting live calves pre-rut (March).