Characteristics of Ayrshire cows with high rates of productive longevity

Le résumé fourni par la source

The study was conducted to substantiate a strategy for increasing the productive longevity of Ayrshire cattle by examining their potential, determining heritability, and identifying the influence of hereditary and non-hereditary factors on the expression of this trait. The study was performed on retired Ayrshire cows born between 2005 and 2015 (n = 2,584) that had at least their first completed lactation. The sample was divided into five groups based on lifetime milk yield (LY) and standard deviation (σ). The groups were formed in increments of 1 σ, starting with cows in group 2 ( ±0,5σ). Lifetime milk yield increased from group 1 (LY up to 18,403 kg) to group 5 (LY from 60,949 kg). Animals with high indicators of productive longevity were characterised by better fertility, increased milk productivity, a more stable lactation curve, and high milk yields throughout all lactations. In cows surviving to the sixth lactation, peak productivity occurred in the fourth to sixth lactation, with milk yields ranging from 8,926 to 9,061 kg; in cows surviving to the ninth lactation, peak productivity occurred in the eighth and ninth lactations, with milk yields ranging from 9,249 to 9,401 kg. Of the hereditary and non-hereditary factors studied, the "sire bull" factor had the greatest influence on the productive longevity of cows. Its influence ranged from 3.8% to 6.2%. The heritability coefficient for productive longevity traits was low – h 2 = 0.038 – 0.062, with p < 0.001 in all cases. Ayrshire cows are characterised by a high potential for productive longevity; however, low heritability complicates direct selection. An effective selection method is the selection of sires.

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