Abstract
dc:description.abstractObserving cows in estrus and inseminating them at the optimal time are necessary steps for effective reproductive management of a dairy herd. However, increasing herd sizes can lead to reproductive inefficiency resulting in decreased profits on dairy herds. Synchronization of estrus, through pharmacological control, has been used to improve reproductive efficiency. Systematic breeding programs provide an organized approach for administering artificial insemination (AI) at first service. Moreover, reproductive management is based on a methodical approach for the entire herd rather than for the individual cow. Seven-hundred and thirty four Holstein cows from 16 commercial dairy herds were used to conduct this study evaluating three systematic breeding protocols; 14-d PGF2a, timed AI (TAI), and GnRH-PGF2α, in comparison with an untreated control group. Eight herds relied on visual observation as their primary method for detection of estrus, and 8 herds utilized the HeatWatch® (DDx, Inc., Denver, CO) electronic estrus detection system. The average days to first postpartum AI were longer for untreated control cows when compared to the other breeding protocols. First AI conception rates did not differ among control, 14-d PGF2a, or GnRH-PGF2a protocols, but were higher than the TAI protocol. However, first AI pregnancy rates were higher for untreated controls versus hormonally treated cows. Estrus characteristics associated with each protocol were also evaluated and no difference was detected across treatments. An economic analysis determining cost per pregnancy for each protocol when considering drug costs, and pregnancy rates, resulted in the highest cost per pregnancy for TAI followed by GnRH-PGF2a and 14-d PGF2a. These programs should be considered as tools for convenience and efficiency of estrus detection; however, reduced labor costs from less time spent on estrus detection may be offset by the cost of the drug protocols. Cost effectiveness must be calculated on an individual herd basis when deciding whether a systematic breeding program is the appropriate choice.
Degree
thesis:*- Name thesis:degree_name
- Master of Science
- Level thesis:degree_level
- masters
- Discipline thesis:degree_discipline
- Dairy Science
- Department dc:contributor.department
- Dairy Science
- Grantor dc:publisher
- Virginia Tech
- Year dc:date.issued
- 1998
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Jobst, Shelly Marie
- Chair dc:contributor.committeechair
-
- Nebel, Raymond L.
- Committee members dc:contributor.committeemember
-
- Vinson, William E.
- Pelzer, Kevin D.
- McGilliard, Michael L.
Subjects
dc:subject × 3Rights
dc:rights- Statement dc:rights
-
- In Copyright
- Licence dc:rights.uri
Identifiers
dc:identifier.*- Dc Identifier Other
- etd-101998-125820
- OAI identifier oai:identifier
- oai:vtechworks.lib.vt.edu:10919/35439