The influence of the degradability of concentrate protein in the rumen and of the lysine content of the concentrate on growth and feed efficiency in early-weaned calves.

In two feeding trials involving 96 rearing calves each and based on a 2 x 3 factorial design, a comparison was made between concentrates containing rapidly and slowly rumen-degradable protein and among concentrates with lysine 6, 7 and 8 g/kg or 7, 8 and 9 g/kg. In a third trial involving 84 animals, 2 feeds containing rapidly and slowly degradable protein were compared. Calves were weaned at 6 weeks and remained in the trial an additional 5 to 6 weeks. Concentrates were fed freely from 21 days old and in 2 trials after weaning the calves were fed according to a plan based on body weight. Hay or prewilted grass silage was given freely. Difference in protein degradability between feeds with rapidly degradable protein and those with slowly degradable protein was 28 and 36% in the second and third trials. Treatments involving concentrates with slowly degradable protein resulted in a higher daily weight gain. Feed efficiency was usually improved. Increase in lysine content of the concentrate from 6 to 8 g/kg or from 7 to 9 g/kg resulted in a significant linear rise in daily weight gain and a linear rise in feed efficiency. In 2 of the 3 trials intake of roughage (1 x prewilted grass silage, 1 x hay) was positively affected by presence in the concentrate of slowly degradable protein. Lysine content of the concentrate had no effect on roughage intake. (Abstract retrieved from CAB Abstracts by CABI’s permission