Influence of variety and storage for up to 22 days on nutrient composition and gossypol level of Pima cottonseed ( Gossypium spp.)

Abstract

Four varieties of Pima cottonseed ( Gossypium spp.; HTO, PHY 57, S-6 and S-7) were collected from 10 cotton gins located in the southwest USA during the fall of 1999 to determine the extent of varietal differences in nutritional components, as well as gossypol levels. In an associated study, the influence of storage for up to 22 days on nutrient composition, gossypol levels and indices of decomposition was assessed in 5 tonne piles of cracked Pima cottonseed at four cotton gins. The piles were on concrete in large roofed storage sheds with open sides. Samples from both studies were analyzed for dry matter (DM), crude protein (CP), acid detergent insoluble CP (ADICP), crude fat (CF), neutral detergent fiber (NDF), 30 h in vitro rumen degradable NDF (dNDF), acid detergent fiber (ADF), and gossypol content. In general, variation within variety exceeded variation among varieties and so there were few varietal differences in nutrient levels. These differences were restricted to organic matter, CP, Ca, K, Cl, Fe, and Zn. There were no varietal differences in total or free gossypol levels, although there were varietal differences in levels of the ‘+’ and ‘−’ isomers of total gossypol. Temperatures of the 5 tonne piles of cracked Pima cottonseed decreased ( P<0.01), free fatty acids increased modestly ( P<0.01) and analyzed levels of NDF and ADF increased ( P<0.01) with storage time. Mold counts, DM, CP, ADICP, dNDF, and gossypol levels were not influenced. Results of these studies indicate modest variation in nutrient and gossypol levels among four major varieties of Pima cottonseed grown in the southwest USA in 1999, and that cracked Pima cottonseed can be stored with little decomposition, or detrimental effects on nutritional value, for up to 22 days provided that it is protected from rain in a dry climate.