Research has debunked the theory that calves don't have a sufficiently high level of parasitism to warrant treatment until weaning, or after.
Spring-born calves from Florida were utilized to conduct a nursing-calf deworming experiment. At least two breed types were available at each location, including Angus, Brangus, Brahman and Romosinuano, as well as some graded combinations of these breeds (composites).
Across all locations, dewormed calves gained 8.7 lbs. more total body weight during the summer, and their average daily gain was 0.1 lbs./day greater than their unwormed counterparts.
Deworming cost about $1.57/head, and such calves returned $9.57/head more net revenue (total weight gain in pounds times $1.28/lb. minus $1.57/head deworming cost). Not included is labor cost, which should be considered because of the potential extra working of the cattle in early to mid summer.
If calculated at $2/head, labor costs could consume nearly 20% of the extra revenue. These data indicate both an animal performance advantage and a positive return on investment. The cost:benefit ratio may not be as significant for the average producer, especially if it means putting the herd through the chute an additional time.
Of course, this equation has various components that affect the outcome directly — calf prices, calf quality, animal performance as affected by rainfall and/or forage availability, labor and processing, etc. Some economists, however, may advise serious consideration of any procedure that adds as little as $1 to the bottom line of any enterprise.
Jeff Carter is an assistant professor in the University of Florida's North Florida Research and Education Center in Marianna.
Effects of age on calving interval, birth weight and weaning weight are independent of body condition score (BCS).
Researchers at the University of California-Davis measured pregnancy rate, calving interval, birth weight, weaning weight and quarterly BCS for five consecutive years on 454 fall-calving multiparous British crossbred cattle (3 to 10 years of age). Body weight and BCS were collected precalving, prebreeding, at weaning, and midway through the second trimester of pregnancy (August). They found:
Three-year-old cows had the lowest body weight and BCS at calving, breeding and in August; eight-year-old cows had the greatest; 10-year-old cows had the highest body weight and BCS at weaning.
Females up to nine years of age had a pregnancy rate of 80%, but it decreased to 57% in 10-year-old cows.
The relationship of pregnancy rate with age appears to be correlated with the BCS decrease at breeding in the older cows, supported by the fact that inclusion of BCS at breeding in the statistical model eliminated the effect of age on pregnancy rate.
Calving interval was longer in three-year-old cows compared to four- to nine-year-old cows, with little change in older cattle.
Birth weight reached a maximum in eight-year-old cows and minimum in three-year-old cows. Birth weights of calves born to both three- and four-year-old cows were lower than for those born to five-, six-, seven-, or eight-year-old cows.
Ten-year-old cows weaned lighter calves than younger dams. Three-year-old cows weaned calves 9 +/- 2.1 and 14 +/- 2.4 kg lighter than four- and five-year-old cows, respectively.
B.J. Renquiest, et al, Journal of Animal Science, 2006, 84:1890