Title page for ETD etd-02192002-143551


Type of Document Master's Thesis
Author Billings, Angela Renea
Author's Email Address arbillin@vt.edu
URN etd-02192002-143551
Title Factors Influencing the Reproductive Efficiency of Dairy Herds in the Dominican Republic
Degree Master of Science
Department Veterinary Medical Sciences
Advisory Committee
Advisor Name Title
Whittier, William D. Committee Chair
Elvinger, Francois C. Committee Member
Hovingh, Ernest P. Committee Member
Madera, Leonardo Rafael Tineo Committee Member
McGilliard, Michael L. Committee Member
Keywords
  • Dominican Republic
  • heat stress
  • reproductive efficiency
  • reproductive outcomes
  • dairy
  • lameness
Date of Defense 2002-02-04
Availability unrestricted
Abstract
Despite an increase in domestic milk production, the dairy industry in the Dominican Republic

(D. R.) has not been able to adequately meet the demand of the ever-growing Dominican population, prompting the government and milk processing plants to sponsor programs which will increase the national production of milk and eventually lead to milk self-sufficiency.

One obstacle to this goal is a very low reproductive rate in cows and heifers due in part to the tropical setting. Year-round heat stress may result in abnormal follicular dynamics and decreased oocyte and sperm quality causing reproductive efficiency to decline drastically.

The specific purpose of this project was to examine and characterize the reproductive practices and outcomes of the Dominican dairy industry by region and to attempt to identify factors that influence dairy reproductive efficiency.

During the course of the study, 43 farms were visited over a 10-week period and evaluated. Farms were chosen throughout 4 of the 5 regions of the country and were selected based on their size (preferably 40 adult cows or more), availability of data, and demonstrated motivation by the owner in improving the herd. Individual herd evaluation was broken into four major components: owner interview, farm evaluation, collection of individual cow reproductive data, and adult cow evaluation.

Once observations had been made and catalogued, all data were summarized on the herd level and analyzed descriptively. In addition to descriptive analysis, multiple regression techniques were used to select independent variables which explain most of the variance for each of four reproductive outcomes: days to first service, services per pregnancy, projected calving interval, and service rate.

In general, reproductive management practices varied depending on region and farm size. Average lameness within the herd was the most important factor in explaining the variability within services per pregnancy and projected calving interval.

As average herd lameness increases by 1 point (based on a 1 to 4 scale), services per pregnancy and projected calving interval increase by 0.65 services per pregnancy and 61.1 days respectively according to the model formulated. Increase in the number of employees involved in estrus detection resulted in higher days to first service.

The Santo Domingo region had lower days to first service possibly due to widespread reproductive hormone use within the region. The percentage of Holsteins within the herd was associated with increased services per pregnancy and projected calving interval. Increases in service rate were most closely associated with the type of record category used, indicating that a larger sample population with thorough insemination records may be needed to adequately assess this outcome.

In part, reproductive efficiency in the Dominican Republic can be potentially improved by enhancing methods for estrus detection. Mechanical aids to estrus detection (tailhead chalk, K-marĂ’ patches, etc.) may help increase estrus detection efficiency in herds currently only relying on visual observation. Assigning 1-2 people primarily to estrus detection and increasing the frequency of hormone usage may also improve estrus detection efficiency.

The main emphasis for Dominican dairy producers, however, should be on preventing new lameness and culling chronically lame cows once it is economically feasible to do so. Reducing the incidence of lameness could, in itself, dramatically improve reproductive efficiency in the Dominican Republic.

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