Effect of seasons on calving

Effect of seasons on calving

Why is calving seasonal?
Red deer and wapiti calve in early summer. Seasonal reproduction ensures that calves are born in weather conducive to survival.  In the northern continental regions, the calving period is also aligned with peak feed production, enabling the hinds to maximise milk production.  This gives the calves the best chance to grow to the body size needed to survive their first winter. Also, the dam needs plenty of high-quality forage to maintain body condition during lactation in order to successfully reproduce in the following year.

What are the benefits of seasonal calving?
In lowland systems, early summer calving can dovetail well with other livestock species, such as spring-lambing sheep. Total farm outputs may be increased by optimising pasture utilisation by the different livestock species over the entire spring-summer period.

What are the other effects of seasonal calving?
Pasture production on NZ lowland farms peaks well before calving due to the benign climate. This can cause a misalignment between feed availability in spring and peak energy demands of lactating hinds in summer. However, there is generally a good alignment between red deer calving and lactation periods and feed production in our high-country systems.

What can be done to minimise unwanted effects of seasonal calving?
It is possible through good nutritional management of the hind at mating to bring forward calving by one to two weeks (see Mating management of adults).

Recent research has found a modest amount of genetic variation in seasonality within red deer strains that will allow for gradual (but permanent) advances of the calving season. Achieving this would require deer breeders to systematically collect information on hind conception dates (using ultrasound scanning) (see Foetal Ageing), parentage of calves and the determination by genetics of stag breeding values for early conception (see DEERSelect).

Show me the science
Asher, G.W., Fisher, M.W., Fennessy, P.F. (1996) Environmental constraints on reproductive performance of farmed deer. Animal Reproduction Science 42: 35-44.