Effects of Different Treatment on the Chemical Composition, Ruminal Degradation Kinetics and In Vitro Digestibility of Cottonseed.

Abstract

This study evaluated the effects of gamma ray (GR), electron-beam (EB) irradiation, microwave irradiation (MI) and roasting (R) on the chemical composition, ruminal degradability and in vitro digestibility of whole cottonseed (CS). Cottonseed samples were treated with gamma irradiation (20 and 40 kGy), electron beam (20 and 40 kGy), microwave irradiation (3 and 5 min), and roasting (at 140°C for 15 and 30 min). Chemical composition was analyzed by standard methods, whereas ruminal degradability of dry matter (DM) and crude protein (CP) was measured using the nylon bag technique with three fistulated cows. In vitro digestibility was determined with the Tilley and Terry method, and amino acid degradability was assessed across treatments. All processing methods decreased neutral detergent fiber (NDF) and acid detergent fiber (ADF) of CS compared to untreated CS (p < 0.05). Gamma and microwave irradiation decreased DM and CP degradability of CS at ruminal outflow rates of 0.02, 0.05 and 0.08 h^-1 (p < 0.05). All treatments decreased effective rumen degradability (ERD) of CS at ruminal out flow rates of 0.02, 0.05 and 0.08 h^-1 (p < 0.05). Roasting and microwave irradiation for 5 min decreased water soluble fraction and increased the slowly degradable fraction of CS compared to untreated CS (p < 0.05). In vitro digestibility of 40 kGy irradiated CS and roasted CS for 30 min was significantly higher than other treatments and untreated CS (p < 0.05). Ruminal disappearances of essential and non-essential amino acids after 16 h incubation in rumen were decreased by electron beam irradiation (p < 0.05). These results indicate that physical processing methods, especially electron beam and roasting, enhance nutritional value of CS for ruminants.