Deer mate in autumn. If calves are weaned before mating, at three to four months old, there are only a few weeks for hinds to recover some of the body weight lost during lactation before they mate again. This may affect their conception rate – hinds with a body condition score (BCS) of less than 3 will conceive about five days later than hinds with a BCS over 4. The earlier hinds mate the better, so they should be fed well before mating. After mating, pregnant hinds can be fed to just maintain body weight – and then given supplementary feed just before giving birth.
Effect of day length
As with food intake, the reproductive cycle in deer is extremely seasonal and governed by day length. Shorter days after Christmas are the cue to stags and hinds that the breeding season is approaching. Hinds start ovulation each year towards the end of March and most conception occurs in the first half of April. Groups of 40–60 hinds are grazed together and mated with a single stag. For proven mature red stags, the ratio may be 100 hinds to one stag. Stags should be removed by 10 May to avoid the birth of late fawns (calves). Pregnancy can now be diagnosed by ultrasound scanning.
Fawn losses from birth to weaning can be high for intensively farmed deer. Often 6–10% of calves born to adult hinds and 12% born to yearling hinds are lost. The most common causes are starvation, misadventure and dystocia (large calves causing a difficult birth).
To minimise calf loss, farmers should have calf-proof fences to keep the newborn animals in the paddocks where they were born. They should also provide space and shelter for the calving hinds, keeping them away from any possible disturbance.
Imported European red deer are much larger than New Zealand red deer. If the two are crossbred it results in faster growing progeny, and larger crossbred breeding hinds. It is common to use a wapiti/red deer bull to mate with the farmed red hinds. The crossbred progeny are ready for slaughter earlier, so the meat often commands a high price in the northern-hemisphere autumn market. On the other hand, crossbreds are more costly to rear – they need almost three times as much pasture as red deer to maximise weight gain.