Genetic evaluation for persistency of lactation in primiparous crossbred Holstein-Friesian dairy cattle using random regression model | การประเมินพันธุกรรมความคงทนของการให้นํ้านมในโคนมลูกผสมโฮลสไตน์-ฟรีเชียนที่ให้ลูกครั้งแรกโดยใช้โมเดลรีเกรซชันสุ่ม
2011
Phakphume Saowaphak | Monchai Duangjinda | Pongchan Na-Lampang | Pakanit Kuppitayanant | Choak Bulakul
Objectives of this study were to 1) determine the appropriate Covariance Function Coefficient (CFC) number of Modified Normalized Legendre Polynomial (MNLP) using in Random Regression Models (RRLP) and 2) mathematical equation for calculate Persistency of Lactation (PL) value. All 9 RRLPs with different 3 to 5 CFC number nested within additive genetics and permanent environmental random effects were used to analyze total 25,845 test-day milk yield records of primiparous crossbred Holstein-Friesian dairy cattle from Chokchai farm. Variance components were estimated by average information-restricted maximum likelihood algorithm and predicted random effects with best linear unbiased prediction method. The results found that RRLP using 3 and 4 CFC numbers nested within additive genetics and permanent environmental random effects (RRLP(3,4)), respectively, was the most appropriate for genetic evaluation of PL. RRLP(3,4) had less number of CFC number, no over-estimation of heritability at the beginning and peak of lactation, and no negative genetic correlation along days in milk. In addition, the estimated breeding value from RRLP(3,4) were used to calculate the appropriate mathematical equation for PL (PL1, PL2, PL3, PL4). The result showed that PL3 was the most appropriate equation to calculate PL in primiparous crossbred Holstein-Friesian dairy cattle of Chokchai farm because it used all days in milk information and thespearman’s rank correlation between 305 days estimated breeding value and PL3 equal to 0.04, which implied the selection on 305 days estimated breeding value was independent from PL.
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