Influence of daughter-breeding methods on the breeding value of Ayrshire bulls in making within-herd assessment

Abstract

We carried out within- and inter-herd assessment of 24 Ayrshire bulls on 28 farms in ten regions of Russia, along with the calculation of their testing reliability depending on different factors. It is revealed that the highest number of bulls was tested in the Leningrad region and the Republic of Karelia (14 and 7 bulls, respectively), which daughters lactated on the greatest number of farms (8 and 4, respectively). It is established that the reliability of stud bull assessment depends on the number of their daughters which can lactate in one or several regions or on a large number of farms of the same region. Using the comparative analysis, we identified the methods for breeding and the productivity of 3077 daughters of bulls. The most commonly used breeding method is cross line, which is 83.1% of the total livestock, including cross combined with inbreeding - 81.2% livestock was bred using it. By applying the intra-linear method, they produced 16.9% of heifers (498 livestock units) of the total livestock. With both breeding methods, more than half of the daughters were produced using remote inbreeding (54.4 and 52.8%). In the group of bulls with positive breeding value, the moderate inbreeding heifers surpass their cross-line peers (+37 vs +16 kg of milk), and in case of intra-linear method, the remote inbreeding heifers enjoy superiority (+68 vs +25 kg of milk) while in the group with negative breeding value, the situation is reverse. To achieve the superiority over peers, we identified the preferred methods of breeding their daughters.