Chemical processing of wheat straw and cotton by-products for fattening cattle 2. Performance of animals receiving material after drying and pelleting

Abstract

ABSTRACTTwo fibrous roughages, wheat straw (WS) and cotton hulls (CH), were either untreated or treated with 30 g/kg or 60 g/kg of sodium hydroxide (NaOH), the residual NaOH was either unneutralized or neutralized with sulphuric acid, and the materials were then pelleted. The effects of these treatments on the nutritive value of the two roughages were examined in an arrangement that differed from the factorial 2 × 3 × 2 = 12 in that only one control group was included for each roughage. Digestibility trials,in vitroandin vivo, and a 7-month feeding trial were carried out. Concentrates were limited in the feeding trial to 6 kg/head per day, and roughages were offeredad libitum.Dry matter digestibilityin vitrowas significantly higher on CH than on WS and was significantly increased by NaOH treatment. Level of NaOH and neutralization of residual alkali had no significant effect. Intake of WS was increased by treatment with 30 g NaOH/kg in the digestibility and feeding trials. Increasing the level of NaOH to 60 g/kg reduced intake of both roughages. Digestibility of organic matter of WS was increased by NaOH treatment at both levels, by 25 to 30%, while that of CH was improved significantly only by the higher level. Neutralization had no effect. The actual intake of roughages was 30 to 35% of the entire ration. The rate of gain of animals offered roughages treated with 30 g NaOH/kg was non-significantly increased, and that of animals offered roughages treated with 60 g NaOH/kg was reduced significantly in comparison with the control. Animals offered NaOH-treated roughages had a significantly higher dressing percentage, and those offered treated WS had a greater fat trim than the control animals. Efficiency of conversion of metabolizable energy into live or carcass weight for both roughages was improved only with the neutralized 30 g NaOH/kg treatment. Comparing the performance in this study with that of a former study of similar design in which the same roughages were offered wet, revealed no marked advantage from pelleting.