Advances in gossypol toxicity and processing effects of whole cottonseed in dairy cows feeding

摘要

Whole cottonseed (WCS) is a byproduct of the cotton-fiber industry. There are Upland and Pima two main varieties of cottonseed (CS), and Pima CS is considered nutritionally superior to Upland CS because of its higher fat and protein content. Pima CS contains more gossypol and a higher proportion of the (-) isomer than Upland CS. Monogastric animals are particularly sensitive to the toxic effects of gossypol, whereas ruminants are somewhat more resistant, especially for female. Concentrations of plasma gossypol (PG) and its negative isomer were directly proportional to free gossypol (FG) intake in dairy cows. The sign of gossypol toxicity observed was an increase in erythrocyte fragility (EF) for cows receiving high dietary FG. Pre- and postpartum consumption of FG might impair some aspects of calf skeletal development and vitamin metabolism, but long-term performance of cows and calves was not affected. The possible effect of WCS fat on reducing microbial activity and potential gossypol toxicity may limit the amount of WCS that can be supplemented to high-yielding dairy cows. The current recommendation is to include WCS at up to 150 g/kg of the diet. WCS processing, especially heat treatment, may aid in providing more unchanged WCS fat and CP to the small intestine, and decreasing ruminal CP degradability and increasing post ruminal digestibility. Heat treatment may also be a useful tool in reducing FG in WCS. Thus, heat treatment may enable an increase in the supplementation rate of WCS for dairy cattle rations. DM intake of dairy cattle is not altered when WCS is included at up to 25% of the diet. The DM intake response to the inclusion of WCS in the diet is a function of both climatic and dietary factors. However, DM intake decreased linearly with increasing levels of iron sulfate in the diet, and substitution of cracked Pima CS for Upland CS increased DM intake..