Effect of Days Open on Lactation Production

<p>Accurate evaluation of dairy production records is essential if dairymen are to establish and maintain profitable dairy herds and efficient culling programs. Improper record evaluation may result in. saving breeding stock that otherwise might be eliminated. Many factors may influence the validity of individual production records. Adjustment factors, currently in use by the United States Department of Agriculture (USDA) for sire and cow evaluations, are generally accepted as removing the majority of these influences. Consequently, these factors are invaluable to practical dairymen. The adjustment factors, suggested by McDaniel, et al. (24) in 1967, take into account the geographical location, season of calving, breed, age at calving, and milking frequency for both milk and fat, independently of one another. These factors are regarded as being adequate in removing variation arising between herdmates. Reproductive efficiency is of economic importance to dairymen. The necessity for regular calving is vital in an efficient dairy operation in order to maintain longevity and maximize lifetime net returns. Calving interval and days open prior to conception are related measures of reproductive efficiency which may assist in production record evaluation. Days open prior to conception actually determine the carving interval, assuming a constant gestation length; consequently, examination of days open would appear more applicable in evaluation of reproductive influences on production. It must be realized that certain environmental factors, such as careful and skillful observation of animals, type of housing system, and nutritional practices, may enter into relationships between production and reproductive efficiency and therefore, these factors must be accounted for in the analysis of data. This study was undertaken to determine the relationships which exist between days open prior to conception and lactation production in South Dakota Holstein herds. The specific objectives of the study were as follows: 1. To determine the influence of days open on 305 day production. 2. To develop adjustment factors for days open, if warranted.3. To determine phenotypic correlations between days open and production.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Dairy Science

Year dc:date.available

1970

Author dc:creator

• Ripley, Roger L

• Dairy Science

Statement dc:rights

• <p>In Copyright - Non-Commercial Use Permitted<br /><a href="http://rightsstatements.org/vocab/InC-NC/1.0/">http://rightsstatements.org/vocab/InC-NC/1.0/</a></p>

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/1271

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-2273