Doctoral Dissertations

John Hodges

Date of Award

3-1975

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

J. B. McLaren

Committee Members

R. R. Shrode, R. L. Murphree, G. M. Merriman, S. L. Hansard, R. S. Dotson

Abstract

Data were collected from 435 Hereford and Angus cows at the University of Tennessee Blount and Alcoa farms during 1972 through 1974 to examine the effects of flushing during the early part of the breeding season on their productivity. All cows were allotted to single-sire breeding groups and grazed grass-legume pastures during the spring-summer pasture season. Grain flushed cows received 6 lb of concentrate per cow per day, in addition to pasture, during the first 21 days of the breeding season (mid-April to early July). Grain flushing had no significant (P>0.05) effect on calving percent in either comparison. There was a significant interaction between year-location and treatment. In addition there were significant differ-ences among groups within treatment in each of the three comparisons. Grain flushed cows weaned more lb of calf per cow exposed than did those on pasture alone. Calves nursing grain-flushed cows during the respective breeding seasons and those born to grain-fed cows the subsequent year gained faster (P<0.05) than calves of cows on pasture alone. Blood serum progesterone level during the first estrous cycle during the breeding season was similar in both groups; however, the progesterone level of grain-fed cows peaked at 6.42 nanograms per ml on the sixteenth day of the cycle compared to 5.03 nanograms in cows on pasture alone. Data collected from 360 Hereford cows during nine years (1966 through 1974) at the University of Tennessee Highland Rim Experiment Station were used to evaluate the effects of weight change during selected periods of the pasture and breeding season on cows reproductive performance and calf growth performance. Conception rate ranged from 72% for three-year-old cows to 91% for nine-year-old cows. There was a trend for conception rate to increase with cow age; however, the increase was not linear. Cow age did not significantly (P>0.05) affect the interval from parturition to conception. Change in body weight of cow during the early part of the breeding season and during the entire breeding season significantly affected (P<0.05) apparent conception date. Cow gains between May and October significantly (P<0.01) affected calf average daily gain during the corresponding period. Each 0.1 lb increase in average daily gain by cows between July and October indicated that a one-day reduction in the interval from parturition to conception had occurred.

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