Restricted Selection Index to Relieve the Negative Repercussion in Reproductive Performance of Holstein Cows

Abstract

The aim of this investigation was to develop restricted selection index aiming to improve 305-day yields of milk (MY), fat (FY) and protein (PY), while keeping the deterioration in days open (DO), calving interval (CI) and number of services per conception (NSPC) at minimum levels in Holstein cows. The data represent 3682 records of 1122 cows, daughters of 95 sires and 712 dams. The data were analyzed by multi-trait animal model with repeated measures. Eight selection indexes (five unrestricted and three restricted) were derived using MY, FY, PY, CI, DO and NSPC in various combinations as sources of information in the indexes. However, the true breeding value included MY, FY and PY. The highest accuracy of selection (0.60) resulted from selection based on the full index. Milk yield and SPC appeared to be the most valuable traits in the full index. Combining the two traits into one index (the best reduced index) gave 0.57 accuracy of selection. The index based on MY alone (the most accurate single trait index) gave 0.53 accuracy. It seems possible to reduce the expected genetic deterioration in the reproductive traits by restricting the full index to result in zero genetic change in NSPC (rTI=0.48). This restriction will allow the breeder to mitigate the deterioration in DO and CI by 12 and 16 days respectively, by sacrificing with part of the expected genetic improvement in productive traits (29, 40 and 48% in MY, FY and PY, respectively).

Partial Restricted Selection Indexes to Fix the Length of Days Open in High – Yielding Dairy Cows

“…The present h 2 value of 0.03 obtained for DO fitted within the range of 0.03 to 0.14 found in the literature (Salem and Hammoud 2016b;Ben Zaabza et al 2016;Farrag et al 2020;Zahed et al 2020;Worku and Aylew 2021;Shemeis and Gouda 2021).…”

“…The present h 2 -estimate for FY (0.30) in Table 1 and that of 0.27 estimated by Lu et al (2022) were higher than the estimates 0.21 to 0.25 obtained with similar model (Carthy et al 2016;Frioni et al 2017;Shemeis and Gouda 2021;Jayawardana et al 2023) and the value of 0.11 to 0.22 estimated via the single trait animal model (Stanojević et al 2013;Albarrán-Portillo and Pollott 2013;Tohidi and Nazari 2023).…”

“…Protein yield was moderate heritable (0.23, Table 1; 0.21, Frioni et al 2017;Jayawardana et al 2023). Slightly higher values (0.28, 0.26 and 0.25) were estimated by Lu et al (2022), Shemeis and Gouda (2021) and Carthy et al (2016), respectively.…”

“…The main criticisms of modern high lactating Holstein cows are their lengthening of day's open, increasing number of services per conception, lengthy calving intervals, and consequently low calf-crop per cow. This occurs due to these traits have strong negative genetic correlations with fat, protein, and milk yields (Zavadilová and Zink 2013;Salem and Hammoud 2016a;Abosaq et al 2017;Frioni et al 2017;Habib et al 2020;Zahed et al 2020;Shemeis and Gouda 2021;Worku and Aylew 2021). Extending the breeding objective in Holstein cows to include reproductive performance traits beside the yield traits was introduced as a strategy to overcome this problem by several authors (Miglior et al 2005;Faid-allah 2015;Sanad 2016;Abosaq et al 2017).…”

“…Applying this strategy did not help so much due to the higher attention paid to the yield traits. Other authors (Ghiasi et al 2013;Gouda et al 2017;Shemeis and Gouda 2021) recommended applying restricted selection indexes to break the unfavourable genetic correlations causing this problem. This action also failed because imposing the complete restrictions resulted in zero genetic changes in reproductive traits, resulting in huge reduction in selection accuracy to unacceptable values.…”