Summer Depression of Litter Performance in New Zealand White Rabbits (1)

Ming-Che Wu (2), Chiung-Tzy Huang (3), Shyh-Chang Lee (4)

and Hsiu-Luan Chang (4)

Abstract

New Zealand White rabbit is a major breed for meat production and medically experimental animals. Taiwan locates at the subtropical region, which has high temperature and relative humidity during the summer season. Therefore, the summer influence on litter performance of rabbit does was investigated. New Zealand White rabbits were raised in Hsinhua county of Tainan for purebred production from January of 1985 to December of 1996. Litter records with at least one pup born were used and there were 7375 litters in total. Litter traits including litter size at birth, number born alive, litter size at 4-week weaning, and survival rates at birth and at weaning were measured. In the population, litter size at birth averaged 6.71 with 6.35 born alive and with 4.80 weaned pups. In records, doe 893422 had 29 litters, so named as the highest one. She produced 178 pups in total and 147 pups weaned. She had a mean of gestation interval of 56 days and 6.75 litters per year. Doe 924499 had 203 pups in her 23 litters and so named as the largest number progeny produud in the herd along with 150 weaned pups also in the highest rank. Pup survival rate at weaning ranged from 50.5 to 56.3% when their primiparous dams giving birth in summer (June to September), but survival rate were 74.3 to 77.9% in winter (January to Feberary). Year mean survival rate at weaning was 69.9%. Lowest survival rates at weaning were observed in those does give birth in July and August mostly, it indicated the summer condition affected pup growth during the nursing period. When litter data grouped into both groups of parity 1 to 5 and parity 6 to 10 for determining the summer effect, we found that percentages of litters with zero pup at weaning were greater than 20% due to farrowing in summer. But there were only 4.29 to 9.68% of litters having zero pup at weaning when they gave birth in winter. Prolific does were designated as those does having greater than eight pups alive at weaning. Hence, the percentage of prolific does to does gave birth in winter was 26% to 34%, but they ranged only 5 to 11% in summer. In summary, the summer in Taiwan resulted in a depression effect on reproductive efficiency in New Zealand White rabbit does which mainly due to the occurrence of litters with zero weanling pup.

(Key Words: Rabbit, Season, Litter size, Survival rate, Gestation interval).


(1) Contribution No. 818 From Taiwan Livestock Research Institute (TLRI).
(2) Department of Animal Physiology, TLRI; Corresponding author.
(3) Animal Farm, TLRI.
(4) Department of Animal Breeding, TLRI.