Association between age at first calving and lactation performance, lactation curve, calving interval, calf birth weight, and dystocia in Holstein dairy cows.

Hadi Atashi,Anise Asaadi,Miel Hostens,Angel Abuelo

doi:10.1371/journal.pone.0244825

Abstract

In the present study, records on 115,291 heifers distributed in 113 herds were used to investigate the association between age at the first calving (AFC) and lactation performance, lactation curve, the length of the first calving interval (CI), calf birth weight (CBW), and the incidence of dystocia in Holstein heifers in Iran. Based on the AFC, the heifers were classified into eight classes: AFC of 541 to 690 d, 691 to 720 d, 721 to 750 d, 751 to 780 d, 781 to 810 d, 811 to 840 d, 841 to 900 d, and 901 to 1200 d (AFC1 to AFC8, respectively). Multiple regression mixed models were used to investigate the association between AFC and lactation curve parameters, partial and 305-d lactation performance, 100- and 305-d SCS, and the length of the first calving (CI) interval. The mean (SD) and median AFC across all heifers was 760.2 (74.01) and 750 d, respectively. Of 115,291 heifers included, 28,192 and 7,602 heifers were, respectively, ≤ 720 and > 900 d when calving for the first time. More than 44% of the heifers were at 691 to 750 d (23 to 25 months) of age when calving for the first time. An increased AFC was associated with increased partial and 305-d lactation performance, 100- and 305-d SCS, initial milk yield, milk production at the peak of lactation, upward and downward slopes of the lactation curve. The 305-d fat percentage was associated with AFC; however, there was no association between AFC and 305-d protein percentage. An increased AFC was also associated with decreased milk production persistency, delayed peak time, longer CI, and higher calf birth weight. Compared to heifers calving for the first time between 691 to 780 d (23 to 26 months) of age, both increasing and decreasing AFC were associated with increased risk of dystocia. Controlling AFC is an important management factor in achieving a lower risk of dystocia, higher lactation performance, lower SCS, and shorter length of the calving interval.

Highlights

Of 115,291 heifers included in the study, 28,192 heifers (24.5%) calved for the first time at 720 d of age or younger, while 7,602 heifers (6.6%) were older than 900 d when calving for the first time
More than 44% of the heifers were at 690 to 750 d of age when calving for the first time (AFC2 and AFC3)
at the first calving (AFC) was associated with calf gender, while predicted mean AFC was longer in heifers delivering males compared to those delivering female calves (769.1 (SE = 1.3) vs. 766.3 (SE = 1.3) d)

Summary

Introduction

Cabrera [8] considering milk yield, milk components, services per conception, days open, and the length of the calving interval (CI), recommended AFC shorter than 700 d for Holstein dairy herds with suitable management. Decreasing AFC is associated with a shorter generation interval and subsequently higher genetic progress [10]; calving too early may be associated with an increased risk of dystocia, reduction in milk yield, milk components and reproductive performance [5, 9, 11]. Increasing AFC, on the other hand, has been reported to be associated with a higher milk, and protein yield, as well as a lower risk of dystocia in the first lactation [10, 12, 13]. The association of AFC and 100and 305-d somatic cell score, calf birth weight, risk of dystocia and the length of the first calving interval was investigated

Objectives

Methods

Results

Discussion

Conclusion