Effects of Variations in Grass Protein Fractions and Degradation Rates on Metabolizable Protein Allowable Milk Production

Abstract

Jonker, J.S., Fox, D.G., Chase, L.E. and Cherney, D.J.R. 2001 Effects of variations in grass protein fractions and degradation rates on metabolizable protein allowable milk production. J. Appl. Anim. Res., 20: 189–196.

Effects of variation of grass forage protein fractions (soluble intake protein, acid detergent fibre insoluble protein and neutral detergent fibre insoluble protein), as measured from producer submitted, samples over a 12 month period and protein degradation rates (B1, B2 and B3) on metabolizable protein allowable milk production were estimated with the Cornell. Net Carbohydrate and Protein System Model (CNCPS). A one standard deviation increase from the average soluble intake protein, for grass forage resulted, in a 5–13 per cent decrease in metabolizable protein allowable milk. A 10 per cent decrease in metabolizable protein allowable milk was predicted with a one standard deviation increase from the average acid, detergent fibre insoluble protein for the grass forage. Up to a 20 per cent increase in metabolizable protein allowable milk was predicted with a one standard deviation increase from the average neutral detergent fibre insoluble protein for grass forage. Metabolizable protein allowable milk was relatively insensitive to changes in protein, degradation rates compared to changes in protein fractions. Accurate forage protein, fraction values are needed to effectively utilize the CNCPS model.

Keywords:

• Net carbohydrate and protein system
• forage quality
• grass