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1950-1979

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Browsing 1950-1979 by Subject "Cattle -- Physiology"

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    Weight change, body condition and beef-cow reproduction
    (Colorado State University. Libraries, 1975) Whitman, Richard Warren, author; Wiltbank, James N., advisor; Remmenga, Elmer E., committee member; Taylor, Robert E., committee member; Carroll, Edward J., committee member
    I. Data compiled on 686 Angus and Hereford cows 2 to 11 years old fed different levels of energy before and after calving were analyzed by the method of least squares to determine the effect of individual weight change and body condition on (1) likelihood of estrus (LOE) 30 to 90 days postpartum and (2) likelihood of pregnancy (LOP) at first breeding. Cows were designated to weight-change groups according to weight gain (G) or loss (L) 120 days before and 90 to 140 days after calving (GG, GL, LG, or LL) and from calving to first breeding (G or L). Cows were also designated to body condition groups (thin, moderate, or good) at calving and first breeding according to visual appraisal and palpated fat cover over the back and ribs. Weight change pre- and post-calving significantly (P < .01) affected LOE 40 and 50 days postpartum. Cows gaining weight before calving had a greater LOE 50 day postpartum than cows losing weight before calving (P < .05). Likelihood of estrus 60 to 90 days postpartum was significantly affected (P < .01) by body condition at calving. For each 10- day interval 60 to 90 days postpartum, LOE increased (P < .05) as body condition at calving improved from thin to moderate to good. Neither weight change before breeding nor body condition at first breeding affected LOP (P > .05). II. Studies were conducted to: (1) determine the repeatability of a cow-height measurement and (2) determine the relation of weight-to-height ratio to measurable backfat. Height at the hips was measured to the nearest .1 cm using a steel caliper, which swung over the cow and extended downward from a pre-set height to the lumbar vertebrae midway between the tuber coxae. Backfat measurements were taken over the 12th and 13th ribs using an ultrasonic scanner. In three separate studies involving a total of 927 height measurements on 250 cows, repeatability estimates obtained were .86, .81 and .91. In two separate studies involving height and backfat measurements on a total of 120 cows, correlations between weight-to-height ratio and measurable backfat were .50 and .71. III. Five hundred sixty Angus and Angus x Hereford cows 6 to 13 years of age were used to determine the relation of pre- and post-calving weight-to-height ratio to likelihood of estrus (LOE) 30 to 90 days postpartum and likelihood of pregnancy (LOP) at first breeding. All cows calved each of the previous three years and were pregnant to Simmental, Simmental x Hereford or Charolais sires. Height of each cow at the hips was measured to the nearest .5 cm and individual weights were taken approximately 120, 90, 60 and 30 days before calving, at first postpartum estrus and at first breeding. Of the pre-calving measurements, weight-to-height ratio (WHR) 60 days before calving most consistently accounted for significant portions (P < .05) of variation in LOE 60 to 90 days postpartum. Cows with a higher WHR 60 days before calving had a greater LOE (P < .05) at each 10-day interval 60 to 90 days postpartum. Weight-to-height ratio at first estrus accounted for a significant portion (P < .01) of the variation in interval from calving to first estrus. Of cows exhibiting estrus by 90 days postpartum (78%), those with a higher WHR at first estrus had a shorter interval from calving to first estrus. Weight-to-height ratio at first breeding was not related to likelihood of pregnancy (P > .05).