Deworming Calves Affects Summer Weight Gain

May 17, 2009 07:00 PM

Glenn Selk, Oklahoma State University Extension Cattle Reproduction Specialist looked at previous research trials that looked at deworming impacts on weight gain to help cattle producers.


He says that five deworming trials were conducted at the Eastern Research Station located at Haskell, Okla., during 1992 through 1996. Crossbred cows and their Charolais sired calves were blocked by sex of calf, calf age and cow age then randomly allotted to three treatments:

  1. non-de-wormed control,
  2. deworm calf only;
  3. deworm cow only; and
  4. deworm cow and calf.

Two or three treatments were applied each year including one control group. Each treatment was applied two or three years. Cows and calves were individually identified and weighed in early June. Treated animals received label-recommended dosages of an ivermectin pour-on. Pairs grazed in rotation seven bermudagrass pastures overseeded with clover at a stocking rate of 2 acres per cow-calf pair during the 144 to 181-day trials. Initial studies indicated that a low worm infection rate was present in the first two years. At that time fecal egg counts ranged from 0 to 28 eggs per 3 gram sample of feces. Deworming cows in late spring had no significant effect on cow summer weight gains up until calf weaning time. All cows in this study were in excellent body condition and rebreeding performance was quite high in both treated and non-treated cows.

Treating cows, but not their calves, resulted in a small advantage in average daily calf weight gains (0.1 pound/day) which resulted in a 15 lb. advantage at weaning time. When the spring-born calves were treated while nursing non-treated cows, they had significantly greater daily weight gains (0.14 lb./day) and a 21 lb. advantage at weaning time.

In other words, just deworming the calves resulted in a 21 lb. weaning weight advantage over non-treated controls, explains Selk. Treated calves nursing treated cows had significantly greater average daily weight gains (0.17 lb./day) than the untreated calves nursing untreated cows. Over the approximate 150 day period this weight gain advantage would total about 25 lb. additional weaning weight to calves in this treatment group OR just 4 lb. advantage over d-worming the calf only. The most profitable economic return for the de-worming expense in this study was noted when the calves only were dewormed.

A different response may be found in other situations where cow condition is poorer, stocking rates differ, or pasture worm-loads vary, he says. Consult your veterinarian to help determine efficient deworming strategies for your operation.

For questions or comments, e-mail Beef Today.
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