Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2012
Publication Date: 2/25/2013
Publication URL: http://handle.nal.usda.gov/10113/56834
Citation: Broderick, G.A., Kerkman, T.M., Sullivan, H.M., Dowd, M.K., Funk, P.A. 2013. Effect of replacing soybean meal protein with protein from upland cottonseed, Pima cottonseed, or extruded Pima cottonseed on production of lactating dairy cows. Journal of Dairy Science. 96:2374-2386. Available: DOI 10.3168/jds.2012-5723. Interpretive Summary: Although still accounting for a only small proportion of total U.S. cotton production, increasing demand for “natural fibers” has increased the acreage devoted to growing Pima cotton. This has increased the supply of Pima cottonseed, a byproduct that so far has largely been fed to dairy cows as a source of dietary protein and energy. Pima cottonseed contains more protein and oil than regular upland cottonseed. However, Pima cottonseed also contains more gossypol, a toxic pigment produced by the cotton plant. The dairy cow is a ruminant and, as such, has a large population of microbes living in its rumen, the first compartment of the stomach. These microbes break down some of the gossypol so it is less toxic to the cow than it is to nonruminants such as pigs or chickens. However, the high levels of gossypol make it necessary to put a lower limit on feeding Pima versus regular cottonseed; this makes dairy farmers afraid to feed Pima cottonseed and depresses its price. Heating is known to promote gossypol reaction with protein, reducing gossypol absorption and toxicity. A new extrusion method was developed that removes much of the oil from cottonseed for bio-diesel production that, in the process, heat-treats the by-product cottonseed cake. The objective of this study was to compare the nutritional value for dairy cattle of regular upland cottonseed to Pima cottonseed and Pima cottonseed that was subjected to this newly developed extrusion process. This research indicates that milk production on diets where cottonseed replaces half of the soybean meal protein (the main protein supplement fed to dairy cows in the U.S.) is at least as good as on diets where all protein supplement comes from soybean meal. This research also indicates that the newly developed extrusion process effectively removes 70-75% of cottonseed oil for bio-diesel production, and that the byproduct feed has increased value because of lower gossypol and better protein utilization. Dairy farmers will benefit because the extrusion process will render Pima cottonseed a safer feed for their dairy cows that is a more effective protein source than regular cottonseed or unprocessed Pima cottonseed.
Technical Abstract: Pima cotton production is increasing in the U.S., but Pima cottonseed contains higher concentrations of the toxic pigment gossypol than conventional upland cottonseed. Heating promotes gossypol reaction with protein, reducing gossypol absorption and toxicity. The objective of this study was to assess the nutritional value for dairy cattle of upland cottonseed (UCS) versus Pima cottonseed (PCS) and Pima cottonseed cake (PCSC) that was heated and oil partly removed by an experimental extrusion process. The PCS had greater crude protein (CP) and ether extract, less neutral detergent fiber (NDF) and ADF, similar total gossypol, but higher (-)-isomer of gossypol compared to UCS; extrusion reduced lipid content by 73%, increased concentration of CP, NDF and ADF, and reduced total gossypol and both (-)- and (+)-isomers of gossypol in PCSC versus PCS. Forty lactating Holsteins (8 with ruminal cannulae) were blocked by days-in-milk into 5 squares in a replicated, incomplete 8 x 8 Latin square and fed diets containing (dry matter [DM] basis) 30% alfalfa silage, 31% corn silage, 21-25% high-moisture corn and about 15% CP. Diets were fed as TMR for ad libitum intake. Supplemental CP was from: 1) solvent soybean meal (SSBM) only or 50% from SSBM plus 50% from 2) UCS, 3) PCS, 4) PCSC, 5) UCS plus PCS, and 6) UCS plus PCSC, or 7) 50% from expeller soybean meal (ESBM) plus 50% from PCS, and 8) 50% from ESBM plus 50% from PCSC. Periods were 4 weeks long (total: 16 weeks). Production data were collected over the last 2 weeks, and blood plasma and ruminal samples were taken on day 28. Data were analyzed using Proc Mixed in SAS. Diet affected dry matter intake with greatest intake on diets 4, 6, and 8, and lowest intake on diets 1 and 3. Milk urea was lowest on diets 3, 7, and 8. No other production trait was affected, and yields of milk, fat, and protein averaged 44.4, 1.71, and 1.26 kg/d, respectively. Milk fat ranged from 3.69 to 3.98% and was unaffected by diet, indicating cottonseed oil did not depress milk fat synthesis. Ruminal concentrations of branched-chain volatile fatty acids were lower or tended to be lower when PCSC replaced either UCS or PCS in the diet, suggesting reduced degradation of PCSC protein. Total gossypol and both (-)- and (+)-isomers of gossypol were higher in blood plasma on PCS and lower on PCSC than on corresponding diets containing UCS. This indicated that the extrusion process reduced gossypol absorption. In this trial, production on diets supplemented with UCS, PCS, or PCSC was comparable to that on diets containing soybean meal.