A note on the effect of variety, type of straw and ammonia treatment on digestibility and on growth rate in steers

Abstract

Forty Hereford cross steers of 350 kg live weight were allocated to 10 treatments in which straw was offered ad libitum. The straws comprised two varieties of winter barley (Gerbel (G) an Igri (I)), two varieties of spring barley (Corgi (C) and Golden Promise (GP)) and one variety of winter wheat (Norman (N)). Each straw was offered either untreated (with 20 g urea per kg added at feeding), or treated (with 30 g anhydrous ammonia). After 10 weeks the treatments were changed. The mean growth rates for steers receiving the untreated straws were 0·11, 0·13, 0·40, 0·20 and 0·27 kg/day and for treated straws were 0·36, 0·33, 0·61, 0·60 and 0·52 kg/day for G, I, C, GP and N respectively. The straw intakes for untreated straws were 3·4, 3·6, 5·2, 4·4 and 4·6 kg dry matter per day and for treated straws 4·7, 4·8, 5·9, 4·9 and 5·8 kg dry matter per day for G, I, C, GP and N respectively. Chemical and biological measurements were compared as predictors of voluntary intake of straw and growth rate in the steers. Biological measurements were very efficient in predicting performance of the steers while chemical measurements were much less valuable.