Inbreeding on litter size of German Spitz dogs

ABSTRACT The objective of the present study was to assess the association between the inbreeding coefficient (F) of German Spitz dogs (litter, sires, and dams) and number of live newborn dogs for this breed. Records of dams and sires of a breeding system were used to calculate the F of 105 litters and their sires and dams and the number of live newborn dogs. The analysis performed through the GLM procedure showed a negative influence of F of litter and mother on litter size. This influence was investigated through models that considered linear and quadratic influences. Although the model that considered quadratic effect of F of the litter achieved the best adjustment, only linear coefficients were significant in both analyses. According to these results, the studied sample of German Spitz dogs exhibits inbreeding depression for litter size, which is an important information for breeders and professionals that assist in dog breeding. In addition to all the known effects of inbreeding on canine health, the results indicate that monitoring inbreeding through F is important for the reproductive success of the breed.摘要 本研究旨在评估德国斯皮茨犬（German Spitz）的产仔窝、种公犬与种母犬的近交系数（inbreeding coefficient，记为F）与该品种活产幼犬数量之间的关联。本研究利用某繁育体系中种公犬与种母犬的繁育记录，计算了105个产仔窝及其对应种公、种母的近交系数F，并统计了各产仔窝的活产幼犬数量。通过广义线性模型（General Linear Model，简称GLM）开展的分析结果显示，产仔窝与种母犬的近交系数F对产仔数存在负向影响。本研究通过构建包含线性与二次效应的模型，对该影响展开了深入探究。尽管纳入产仔窝近交系数F二次效应的模型拟合效果最优，但两项分析中仅线性系数均具有统计学显著性。基于上述结果，本次研究的德国斯皮茨犬样本在产仔数性状上存在近交衰退现象，该结论对犬类繁育者及相关辅助从业人员具有重要参考价值。除已知的近交对犬类健康的各类影响外，本研究结果还表明，通过近交系数F开展近交监测，对该品种的繁育成功至关重要。