2011 Annual Report
1a.Objectives (from AD-416)
The objective of the proposed research is to determine the relative nutritional value of the protein in Pima cottonseed meals for lactating dairy cows.
1b.Approach (from AD-416)
This will be a 3x3 Latin square feeding trial using 24 high-producing lactating dairy cows, including 6 with ruminal cannulas, from the U.S. Dairy Forage Research Center herd. Three diets will be fed:.
1)all supplemental protein fed as solvent-extracted soybean meal,.
2)all supplemental protein fed as conventional cottonseed meal originating from up-land cottonseed, and.
3)all supplemental protein fed as Pima cottonseed meal prepared using the experimental expeller process. All diets will be based on alfalfa and corn silages plus high-moisture corn, formulated to contain 16.5% crude protein and will be fed as total mixed rations. Cows will be blocked into groups of 3 by days-in-milk and, within blocks, randomly assigned to treatment sequences; 2 blocks will be of ruminally cannulated cows. Periods will be 4 weeks long (total 12 weeks); the first 2 weeks will be for diet adaptation; data on milk yield, milk composition, milk component yield, milk urea concentration, body weight change, and feed intake will be collected over the last 2 weeks of each period. Feeding rates will be adjusted daily for ad libitum intake. Blood will be collected on day 28 of each period and analyzed for urea and glucose concentration. Spot urine and fecal samples will be taken on days 27-28. Urine will be analyzed for creatinine, urea, and total N. Data will be used to predict excretion of urea and total N using creatinine as marker. Feces will be analyzed for total N, dry matter, and indigestible acid detergent fiber. Apparent digestibility and fecal output of dry matter and N will be computed using indigestible acid detergent fiber as marker. On days 27-28 of each period, cannulated cows will be used for sampling to determine ruminal pH and concentrations of ammonia, total amino acids, and volatile fatty acids. Data will be analyzed as a replicated 3x3 Latin square using Proc mixed in SAS.
This project is related to the following objective and sub-objective of the parent project: Objective 1. Improve accuracy, reproducibility, and ease of measuring/estimating feed digestibility; sub-objective 1.B.: Develop and evaluate in vitro methods for assessment of ruminal degradability of dietary proteins. This project was initiated in March 2010. In September 2010, a feeding experiment was completed to assess the effects of substituting conventional and Pima cottonseed (as well as an extruded byproduct made from Pima cottonseed) for soybean meal, the major protein supplement added to dairy cow diets in the U.S. The acreage devoted to growing Pima has been increasing in recent years because of consumer demand for the longer fiber in Pima cotton. However, Pima cottonseed has much greater amounts of the toxic pigment, gossypol, than conventional cottonseed. This reduces the value of Pima cottonseed as a feed supplement. Moreover, cottonseed oil has considerable value for use in human cooking. The cooperator on this project developed an experimental extrusion process that squeezes the oil out of Pima cottonseed and, at the same time, generates sufficient heat to cause much of the free gossypol to react with protein in the seed. Replacing half of the supplemental soybean meal protein in the diet with an equal amount of protein from conventional Pima cottonseed or the extruded Pima cottonseed did not result in any loss of milk production or milk components. In addition, gossypol content in the blood of dairy cows eating the extruded Pima seed was lower than that of cows eating Pima and conventional cottonseed, indicating that this seed may indeed serve as a valuable dairy supplement. Monitoring of the activities related to this project by the cooperator was conducted via a number of telephone conferences and email messages. This project is scheduled to terminate in August 2011.