engleski

Influence of season and herd size on the age at first calving in Busha cattle breed

The range of the age at the first calving of this late-maturing breed is wide. The estimation of the optimal age at the first calving is of great importance for the growth and development of calves as well as for the later reproductive performance of the autochthonous breed. The aim of the study was to determine the effect of the calving season (CS) and herd size (HS) on the age at the first calving (AFC) for the Busha cattle. Data set for 1, 376 primiparous cows was taken from the central database of the Ministry of Agriculture for the period from January 2003 to February 2019. Primiparous cows were grouped into three classes according to AFC (months) as follows: the first group between 19 and 26, the second group between 27 and 32, and the third group between 33 and 40 months of age. The data within each AFC group were analysed using the least square method and GLM procedure in the SAS software package. The effect of CS as the year-season interaction (four calving seasons were defined according to the year period) and HS with three levels (1–3, 4–10, and more than 10 animals per herd) were included in the model for each AFC group. The highest number of calvings according to AFC (n = 825) was recorded in the first group, with the average AFC of 23.1 months. Both effects were significant (p < 0.01) and accounted for 15.7% of AFC variability. In the second calving group (n = 273), the average AFC was 29.3 months and only CS (p < 0.01) affected AFC and accounted for 31.3% of the variability. The lowest number of calvings (n = 178) was recorded in the third group, with the average AFC of 35.8 months. Both effects, CS and HS were significant (p < 0.01) and accounted for a certain proportion (27.9%) of AFC variability. AFC, calving season and herd size could contribute to a high variability in the management of reproduction as a result of difficulties in the planned breeding of native breeds. An assessment of the optimal management procedure with the use of phenotype data can contribute to improving breeding strategies within local cattle breeds.

cattle ; Busha ; reproductive performance

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