The effect of growth rate on reproductive outcomes in replacement dairy heifers in seasonally calving, pasture-based systems

Files in This Item:
Access to this item has been restricted by the copyright holder until:2020-04-17
File Description SizeFormat 
The effect of growth rate on reproductive outcomes in replacement dairy heifers in seasonally calving, pasture-based systems - JDS 2019.pdf597.29 kBAdobe PDFDownload    Request a copy
Title: The effect of growth rate on reproductive outcomes in replacement dairy heifers in seasonally calving, pasture-based systems
Authors: Hayes, Ciara J.
McAloon, Conor G.
Carty, Catherine I.
Ryan, Eoin Gerard
Mee, John F.
O'Grady, Luke
Permanent link: http://hdl.handle.net/10197/10334
Date: 17-Apr-2019
Online since: 2019-05-08T08:20:18Z
Abstract: The effect of average daily gain (ADG) on reproductive outcomes in replacement dairy heifers was investigated. All heifers were managed in the typical Irish spring calving, pasture-based system, where the herd calves in 1 block between January and April and the majority of the diet comprises grazed grass. Heifer calves (n = 399) from 7 herds were weighed at birth and at the beginning of the breeding season, and ADG was calculated. Service dates and pregnancy diagnosis results were recorded, and conception dates were calculated. Days open (DO) was defined as the number of days between the beginning of the breeding season and conception. Genetic data were retrieved from the Irish Cattle Breeding Federation database. A Cox proportional hazard model was constructed to identify variables with a significant effect on DO. An accelerated failure time model was used to predict survival curves and median survival times for different combinations of the significant variables. The ADG ranged from 0.41 to 0.91 kg/d, with a median of 0.70 kg/d. Frailty effect of farm within year, maintenance subindex of the economic breeding index, and ADG had a significant effect on DO. Derived from the final accelerated failure time model, the predicted median DO for a heifer with an ADG of 0.40, 0.70, or 0.90 kg/d aged 443 d at the beginning of the breeding season and with a maintenance subindex in the second tercile were 27, 16, and 11 d, respectively.
Type of material: Journal Article
Publisher: American Dairy Science Association
Journal: Journal of Dairy Science
Copyright (published version): 2019 American Dairy Science Association
Keywords: Average daily gainDairy heiferReproductionAge at first calvingSeasonal system
DOI: 10.3168/jds.2018-16079
Language: en
Status of Item: Peer reviewed
Appears in Collections:Veterinary Medicine Research Collection

Show full item record

Google ScholarTM

Check

Altmetric


This item is available under the Attribution-NonCommercial-NoDerivs 3.0 Ireland. No item may be reproduced for commercial purposes. For other possible restrictions on use please refer to the publisher's URL where this is made available, or to notes contained in the item itself. Other terms may apply.