Chemical processing of wheat straw and cotton by-products for fattening cattle. 1. Performance of animals receiving the wet material shortly after treatment

Abstract

SUMMARYTwo fibrous roughages, wheat straw and cotton hulls, were treated with 0, 40 and 80 g sodium hydroxide (NaOH)/kg roughage, applied in amounts of water calculated to bring the roughages to moisture contents of 30 and 60%. The effects of these factors on the nutritive values of the two roughages were examined using a 2 × 3 × 2 factorial design.Digestibility trials,in vitroandin vivo, and a 9-mo feeding trial were carried out with the roughages soon after treatment. Concentrates were limited to 6 kg/head per day throughout the animal experiments and roughages were offeredad libitum.Neutral detergent fibre decreased by 7·8 and 13·5% with the 40 and 80 g application rates of NaOH respectively.The treatment of both roughages with NaOH increased considerably theirin vitrodry matter digestibility and total solubles after enzyme treatment, the increases being related to the rate of application of NaOH. Digestibilityin vivowas improved only by the 40 g NaOH treatment.Treatment with NaOH reduced the voluntary intake of both roughages. Only the 80 g/kg treatment had a positive effect on rate of live- and carcass-weight gain. On the other hand, NaOH improved very significantly the efficiency of conversion of metabolizable energy into live and carcass weight and increased significantly the degree of fatness of the animals. These results indicate a marked improvement in the nutritional value of both roughages due to NaOH treatment. The reason for the small response in rate of gain may be explained by a shortage of protein owing to a possible reduction in its digestibility. Cotton hulls excelled wheat straw in almost every respect. Animals on NaOH-treated cotton hulls bloated chronically unless some long straw was given. Moisture level had practically no effect on performance.The effects of the treatments on rumen or blood constituents were small.