The effect of gossypol on blood and hormone profiles in beef heifers
Wehner, Brent Stafford
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Despite the widespread use of cottonseed and cottonseed meal as supplemental feed for beef and dairy cattle, there are many physiological problems associated with a toxic chemical located in the pigment glands throughout the cotton plant called gossypol. Few studies have looked at how feeding cottonseed or cottonseed meal can affect embryo implantation rates and other physiological factors in heifers and cows. This study examined the reproductive potential of the female by examining implantation rates, steroid hormone cascade, and the effects of gossypol on overall wellness of the animal as exhibited by blood physiology. Fifty Angus and Brangus crossbred heifers were used in this trial to evaluate these potential effects. Heifers were randomly assigned to one of two diets. Treatment (n=26) and control (n=24) heifers were in pen number one and two, respectively. The control and treatment diets were sorghum-silage based and balanced to be iso nitrogenous and iso caloric; the treatment diets contained 17% cracked Pima cottonseed. The diets were fed for 223 days. Pima cottonseed is known to have a greater percentage of gosypol and a higher ratio of the (-) isomer when compared to upland cottonseed (Sullivan et al., 1993). No differences were found between the treatment and control group for body weight. There were obvious differences in gossypol level (P < .0001) as the control group had a mean level of 0.00 ug/ml and the treatment group had a mean of 9.05 ug/ml from day 1 to 43. There were differences between the two groups for erythrocyte fragility (P < .0001). There were no differences found between the two groups for either estradiol-175 or for progesterone levels. No differences were found between the groups for implantation rates, but zero pregnancies were found via rectal ultrasound 47-days after embryo transfer. Data from this current study suggest that feeding cracked Pima cottonseed at a level of 17.5% in the diet increased erythrocyte fragility and plasma levels of gossypol, however, heifer body weight and hormone levels were not effected. Further research is needed to determine if gossypol affects embryo implantation rates in beef females.