Effect of heat stress on nonreturn rate of Italian Holstein cows
Author(s)
Date Issued
2016
Type
article
Volume
99
Issue
99
Start Page
5837
End Page
5843
ISSN
220302
Journal
Abstract
The data set consisted of 1,016,856 inseminations of 191,012 first, second, and third parity Holstein cows from 484 farms. Data were collected from year 2001 through 2007 and included meteorological data from 35 weather stations. Nonreturn rate at 56 d after first insemination (NR56) was considered. A logit model was used to estimate the effect of temperature-humidity index (THI) on reproduction across parities. Then, least squares means were used to detect the THI breakpoints using a 2-phase linear regression procedure. Finally, a
multiple-trait threshold model was used to estimate variance components for NR56 in first and second parity cows. A dummy regression variable (t) was used to estimate NR56 decline due to heat stress. The NR56, both for first and second parity cows, was significantly
(unfavorable) affected by THI from 4 d before 5 d after the insemination date. Additive genetic variances for NR56 increased from first to second parity both for general and heat stress effect. Genetic correlations between general and heat stress effects were −0.31 for
first parity and −0.45 for second parity cows.
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Name
JDS_NR56_R2.pdf
Description
Accepted version
Size
391.03 KB
Format
Adobe PDF
Checksum (MD5)
7776c0abef32dccf8d898dc2d6a96ea7
Conference(s)
JOURNAL OF DAIRY SCIENCE