Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Whole cottonseed extruded at temperatures ((DEGREES)C) and rates (kg/hour) of 131, 314; 135, 182; 146, 195; and 156, 286 was evaluated for protein solubility, in vitro ammonia production, and in situ disappearance to estimate bypass protein potential. Whole cottonseed, soybean meal, corn gluten meal, and soybean meal and whole cottonseed heated for 4 hours at 127, 138, and 149(DEGREES)C were also evaluated for comparison. Solubility was determined by three methods: hot water-refluxed 1 hour; cold water-mixed 30 minutes; and cold water-homogenized 5 seconds. Ammonia production was measured after 2, 4, and 6 hour incubations. Disappearance of crude protein and dry matter was determined by suspending nylon bags in the rumen for 1, 2, 4, 8, 12, and 24 hours. All solubility methods demonstrated that extrusion reduced (P < .05) whole cottonseed solubility. Ammonia production indicated that whole cottonseed was similar to extruded cottonseed. The in situ method distinguished the 146 and 156(DEGREES)C products as having the lowest (P < .05) disappearance of dry matter and crude protein, after 24 hours, compared to whole cottonseed and the other extruded products. Based on the results obtained from previous analyses, a product was extruded at 152(DEGREES)C and 436 kg/hour to determine its feeding value and bypass protein potential in a lactation trial. Twenty six, early lactation Holstein cows were randomly assigned to one of four experimental groups. Eleven cows, averaging 43 days postpartum, began the trial with remaining cows assigned 7 to 14 days postpartum. Complete diets based on corn silage and 16.4% (as fed) crude protein pelleted concentrate were fed twice daily. Groups consisted of a positive and negative control, and whole cottonseed and extruded cottonseed treatments. Positive control cows produced the most (P < .05) milk and 4% fat corrected milk; the negative control group was the lowest (P < .05). Treatments were intermediate to the controls. The greatest milk fat percentage was for the controls. Total solids and milk protein percentages were highest for the negative controls while the positive control and cottonseed treatment groups were similar.