A study was conducted to analyze reproductive data gathered over a ten-year period at the Utah State University Dairy Farm. The study utilized 289 complete first lactations of Holstein cows, including 150 daughters of 10 sires in Trial I and 139 daughters of 8 sires in Trial II. One sire was used in both trials; this was sire 4 in Trial I and sire 18 in Trial II. The study measured ration, season, and sire effects and their interactions on the reproductive performances of dairy cows.
Reproductive traits analyzed were: days from calving to first estrus, days from calving to first breeding, days from first breeding to pregnancy, days open, number of services per pregnancy, pregnancy rate, calving interval, number of estrous cycles to first breeding, and number of estrous cycles to pregnancy.
Sire effect examined the effect of predicted difference for milk (PDM) of sires on reproductive performances of their daughters. There was 1352- kg PDM difference between lowest and highest sire. There was no sire effect among North American sires, but daughters of one sire from New Zealand had significantly lower reproductive performance. Reproductive performance of daughters was not related to PDM of sire.
Ration affected calving interval in the comparison of all four rations. But more data is needed to verify this because only one sire had daughters on all rations.
Effect of season of calving on days open and days from first breeding to pregnancy is also very questionable because of small numbers of daughters in some seasons. Ration by season interaction affected days open, services per pregnancy and pregnancy rate. The high energy ration enhanced reproduction in cold season and low energy was more beneficial in cows calving in hot season.
There was no sire by ration interaction effect.
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-5085 |
| Date | 01 May 1987 |
| Creators | Chen, Jen-Hon Justin |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact Andrew Wesolek (andrew.wesolek@usu.edu). |
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