Analysis of fertility in canine populations in respect to genetic and environmental influences

Introduction Reproduction is a multifactorial trait. The final litter size in multiparous species depends on ovulation rate, ova success, uterine capacity and embryonic survival. Ribero et al.(1997) studied littersize in mice as a model animal in respect to the base components. They compared simulation data with experimental results. Uterine capacity was an important source of variation but ovulation rate was the more limiting component. Response to experimental selection (heritability) was 0.15 for litter size. Satoh et al. (1997) report about 15 generation selection in golden hamsters as a model animal for pigs. They got 2.2 pups more in the selection line. Heritability was found to be 0.10 for litter size. In these cases, as usual, litter size was treated as phenotypic realisation of the mother. A male effect can come from embryonic survival and from semen quality. This was mainly investigated in context with semen trading and insemination programs in pigs. Smital et al.( 2005) found high heritabilities for semen quality criteria (Volume 0.58, sperm concentration 0.34, progressive motion 0.38), but the heritability of the target trait, litter size, was only 0.05. The male genetic effect on conception was 0.29. Similar investigations were presented by Grandjot (1996). He analysed the data from a pig hybrid program over 6 years with 36628 matings. He found like Smital et al., under the given semen confection, no influence of the semen parameters. The influence of the boars on conception and litter size was so low that selection based on their own fertility results did not promise acceptable success. Heritability for the male influence was 0.010 and for the female 0.084. The genetic influence on conception was 0.003 from the male and 0.033 from the female part.