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Factors affecting reproductive effic...

Starbuck, Melanie J.

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Factors affecting reproductive efficiency of cattle.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Factors affecting reproductive efficiency of cattle./
作者:	Starbuck, Melanie J.
面頁冊數:	159 p.
附註:	Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6364.
Contained By:	Dissertation Abstracts International66-12B.
標題:	Biology, Animal Physiology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3201747
ISBN:	9780542468537

Factors affecting reproductive efficiency of cattle.
Starbuck, Melanie J.

Factors affecting reproductive efficiency of cattle. - 159 p.

Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6364.

Thesis (Ph.D.)--West Virginia University, 2005.

Four experiments were conducted to evaluate two measures of reproductive efficiency in cattle, conception rate and retention of pregnancy. In experiment I, the relationship between concentrations of progesterone and retention of pregnancy was examined. The corpus luteum (CL) was removed on day 29 of pregnancy in 40 suckled, beef cows, and pregnancy was supported with exogenous progesterone to day 53. Concentrations of progesterone (1.8 +/- 0.1 ng/mL between days 30 and 38), were below those normally recorded for pregnant cows. Retention of pregnancy (77%) was monitored frequently using ultrasonography until day 53 and was negatively associated with age of cow, but not directly related to concentrations of progesterone or estradiol, or body condition score. On day 53, a new CL was induced using hCG and exogenous progesterone support was withdrawn (experiment II). Pregnancy was maintained to term in all 20 cows that formed a new CL, including four in which the new CL was contralateral to the uterine horn of pregnancy. Effects of a single treatment with rbST at artificial insemination on conception rates and retention of pregnancy in dairy cows and heifers and beef cows were examined in experiment III. Conception rates were increased only in dairy cows, specifically those > 100 days in milk. Retention of pregnancy was not affected by treatment with rbST. In experiment IV, the relationship between the number of antral follicles that developed within a follicular wave and fertility was examined. Development of follicles ≥ 4 mm in diameter was monitored by ultrasonography on alternate days from day 6 of the cycle until ovulation or diagnosis of pregnancy in beef cows and heifers before and after insemination during two (Trial 1) or three (Trial 2) estrous cycles. Cows were artificially inseminated 12 h after second estrus (Trial 1) or third estrus (Trial 2). Numbers of follicles ≥ 4 mm in diameter differed with estrous cycle, follicular wave, and cow, but the average number of antral follicles per wave did not affect conception rates. Additional research is needed to determine the specific roles of age of cow and concentration of progesterone on reproductive efficiency.

ISBN: 9780542468537Subjects--Topical Terms:

1017835
Biology, Animal Physiology.

Factors affecting reproductive efficiency of cattle.
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