J. BEZDÍČEK1, L. STÁDNÍK2 and F. LOUDA3
1 Palacký University, Department of Zoology, Faculty of Science, 77147 Olomouc, Czech Republic
2 Czech Univesity of Life Sciences, Department of Animal Husbandry, Faculty of Agrobiology, Food and Natural Resources, 165 21 Prague 6 – Suchdol, Czech Republic
3 Agriresearch Rapotin Ltd., Department of Feed, Nutrition, Breeding and Reproduction, 78813 Vikyrovice, Czech Republic
BEZDÍČEK, J., L. STÁDNÍK and F. LOUDA, 2015. The influence of inbreeding depression on reproduction traits - age at first calving in dairy cows. Bulg. J. Agric. Sci., 21: 680–686
The aim of this study was to evaluate the effect of inbreeding depression on age at first calving in Holstein and Czech Fleckvieh cows. Only cows with a complete pedigree to the fifth generation were used. Data were collected from 34 farms in the Czech Republic. For proper comparison, each inbred cow (n=1046) was assigned to at least one noninbred equal (n=1046). Inbred and noninbred pairs were matched on characteristics such as identical father, first calving interval occurring at the same farm and calves born in the same year and month (± 2 months). The PROC GLM of SAS® with five fixed effects was applied to all data. Inbred Holstein and Czech Fleckvieh cows and their matched noninbred equals were then divided according to inbreeding coefficient into four (event. five) groups. For Holstein inbred groups: FX = 1.25; FX = 3.125; FX = 6.0-12.0; FX = 25.0; FX>25; respectively all animals, the following extension of age at first calving was found: +2.7; +6.9; +9.5; +18.5; +26.8; +9.6 days, respectively. While for Czech Fleckvieh inbred groups: FX = 1.25; FX = 3.125; FX = 6.0-12.0; FX = 25.0; respectively all animals, the prolongation of age at first calving was detected on the level +2.3; +3.9; +9.8; +21.3; +9.8 days, respectively. This study showed the negative effect of inbreeding on prolongation of age at first calving. Deterioration in this reproduction trait occurred even at low levels of the coefficient FX. At higher levels the differences between inbred and noninbred cows were significant (P<0.05-0.01).