Seasonal and breed effects on reproductive parameters in bitches in the tropics: a retrospective study
2007
Chatdarong, K. | Tummaruk, P. | Sirivaidyapong, S. | Raksil, S.
To investigate the influence of season and breed on reproductive parameters in bitches raised under tropical climatic conditions. Over a seven year period, from 1998 to 2004, 310 oestrous periods of 53 bitches were observed. The dogs were of various breeds; dobermann (number of bitches/number of oestrous cycles) (n=2/19), German shepherd dog (n=35/211), Labrador retriever (n=14/68) and Rottweiler (n=2/12). In 250 of the 310 oestrous periods, natural matings took place on days 9 and 11 after the onset of pro-oestrus. The whelping rate was analysed for bitches of each breed. Variables, including breed and the whelping rate, by month of the year, were used for analysis of the inter-oestrus interval, gestation length, total number of pups born, number of live pups born and the weight of the pups at birth. A low frequency of oestrous activity was found during the summer. Breeding dogs in the summer resulted in a low whelping rate. No difference (P>0·05) was seen in the whelping rate of each breed: dobermann (70·5 per cent), German shepherd dog (61·5 per cent), Labrador retriever (67·9 per cent) and Rottweiler (100 per cent). The Labrador retriever had a longer inter-oestrus interval (252 [114] and 190 [61] days) (P<0·01) and a larger litter size (8·2 [1·8] and 6·6 [2·8]) (P<0·05) than the German shepherd dog. The environmental factors in summer tend to reduce oestrus incidence and fertility in the bitches. According to litter size, the Labrador retriever seems to have a more efficient reproductive performance than the German shepherd dog. The Labrador retriever had a longer inter-oestrus interval than the German shepherd dog.
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