Masters Theses

Date of Award

12-1977

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

R. L. Murphree

Committee Members

H.V. Shirley, D.O. Richardson

Abstract

This study involved 414 beef cows and heifers in three University of Tennessee experimental station herds, including the herd at the Tobacco Experiment Station (TES), at Greeneville, Tennessee, the Middle Tennessee Experimental Station (MTES) herd at Spring Hill, Tennessee, and the herd at Ames Plantation (AP), Grand Junction, Tennessee.

The objective of the study was to determine the feasibility of use of exogenous hormones to synchronize time of ovulation in beef cows and heifers so that females may be bred at an appointed time. The hormone treatment consisted of a subcutaneous ear implant of Hydron plastic containing 6 mg of norgestomet (a synthetic progestin) and subcutaneous injection of 2 ml of sesame oil containing 6 mg estradiol valerate and 3 mg norgestomet at the time of implantation. The implant W: 3 removed 9 days after placement. Lactating cows were separated from their calves for 48 hours following implant removal and were artificially inseminated 48-54 hours after implant removal or were turned with bulls for natural service. Control cows were either bred artificially or by bulls as the females exhibited estrus. The breeding season extended from March 6 to June 30. Females were examined via rectal palpation in late July and early August to determine pregnancy.

A total of 142 Hereford cows and heifers was used in the TES herd. The pregnancy rates for 69 control and 62 treated females were 88 and 85 percent, respectively. Only 4 of 11 cows which had calved within 30 days prior to treatment were pregnant.

Forty Angus and 40 Angus-Charolais crossbred heifers were used in a 2 X 2 factorial study involving the hormone treatment and feeding of iodine (as ethylenediaminediodide) in the MTES study. Iodine was fed one-half the heifers at the rate of 3 mg per kg body weight per hed daily. The pregnancy rates were 79 (27 of 34) and 74 (34 of 46) percent for the control and hormone treated groups, respectively. The pregnancy rates for the iodine-control and iodine-fed groups (no hormone treatment in either group) were 94 (16 of 17) and 16 (11 of 17) percent, respectively. The pregnancy rates for the hormone-treated and hormone-treated plus iodine were 96 (22 of 23) and 52 (12 of 23) percent, respectively (X2 =9.1; P2=13.53; PA total of 192 Angus cows and heifers was used in the AP herd. The pregnancy rates for control cows and implanted cows were 72 (51 of 77) and 76 (62 of 81) percent, respectively. The fertility of control and treated heifers was 89 (16 of 18) and 63 (10 of 16) percent, respectively.

Under the experimental conditions of these three studies, it is concluded that use of Sunchromate-B for estrus synchronization had no significant effect upon early conception in cows and heifers and was of negligible value in inducing early estrous cyclicity in prepuberal heifers. In addition, it is concluded that addition of high levels of iodine to beef heifer rations interferred with pregnancy.

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