Comparison of whole short staple, whole Pima, cracked Pima and ground Pima cottonseed in diets for lactating dairy cows.

Abstract

Two lactation studies with accompanying digestion trials were conducted to compare the feeding value of Pima cottonseed, with differing degrees of processing, to short staple cottonseed for lactating dairy cows. Additional tests were conducted to examine physical and chemical characteristics of both Pima and short staple cottonseed and the effect of processing on storage characteristics of cottonseeds. Pima cottonseed is higher in CP and ether extract and lower in NDF and ADF than short staple seed. Pima seed has a greater bulk density, a greater proportion of the (-)-gossypol isomer and a lower proportion of the (+)-gossypol compared to short staple cottonseed. In the first lactation study, milk yield was similar across all treatments. Milk fat was higher (P < .05) for finely cracked Pima (x 3.0 mm) and whole Pima diets. Feed efficiency was greatest (P < .05) for the cracked Pima diet. Percentage whole seed passing into the feces of that consumed, was 11% for the whole Pima and 5.2% for the short staple. Total tract digestibility of ADF decreased and that of ether extract increased in cows fed cracked Pima compared to whole Pima or short staple. In the second lactation study, milk yield was higher (P < .05) for cows fed ground Pima (x 2.5 mm), than either whole Pima or coarsely cracked Pima (x 3.5 mm), with short staple intermediate. Feed efficiency (SCM/DMI) was greater for cows fed ground Pima and short staple diets (1.14) than for those fed cracked Pima or whole Pima. Stearic acid was lower, and linoleic and linolenic acids were higher in milk of cows fed ground Pima compared to short staple. Passage of whole seed was two-times greater for cows fed whole Pima compared to whole short staple (12.3% vs. 6.2%), and processing of Pima seed eliminated whole seeds passing in the feces. Ether extract digestibility was lower for the whole Pima compared to the other treatments. Storage of whole, cracked or ground seeds at 32°C and 30% relative humidity for up to 30 d did not cause rancidity or aflatoxin contamination. Storage of processed seeds in covered containers for nine months caused only slight increases in free fatty acid content, and no change in the whole seeds.