Effect of Wheat Silage Maturity on in situ Degradation of Organic Matter, Crude Protein, Starch and Fibre

Abstract

Südekum, K.-H., Thordsen, J.P. and Stangassinger, M. 1996. Effect of wheat silage maturity on in situ degradation of organic matter, crude protein, starch and fibre. J. Appl. Anim. Res., 10: 1–14.

Winter wheat (Triticum aestivum L.), harvested at late milk (LM), early dough (ED) and hard dough (HD) stages of maturity was ensiled. Rate and extent of degradation of feed fractions contained in wheat silages were determined. Polyester bags filled with 3 g silage dry matter were incubated in the rumen of six fistulated steers for 9 different times (0, 2, 4, 6, 8, 12, 24, 48 and 288 h) in a repeated 3 x 3 Latin square design. Starch contents of the silages increased markedly and fibre contents decreased with maturity. Zero time (0 h) disappearance of crude protein (CP) was<85% across maturities and mainly in the form of water-soluble CP assumed to be instantaneously degradable. 0 h values for starch were<89% across maturities, mainly in the form of water-insoluble small particles. After 12 h of ruminal incubation, ≥ 98% of starch of all silages had disappeared from the bags. The extent of organic matter (OM) degradation increased with advancing maturity, whereas, the rate of OM degradation decreased. Effective degradabilities of the OM were greater for the ED and HD silages than for the LM silage at all the three assumed ruminal passage rates (2, 5 and 8% per h). Stage of silage maturity had no consistent effect on degradation kinetics of cell-wall constituents. Extent and direction of silage maturity effects varied with fibre fraction and maturity stage. In conclusion, increased content of rapidly degradable starch with maturity and overall lack of negative effects of maturity on fibre degradation parameters resulted in favourable ruminal degradation characteristics of the ED and HD silages compared with the LM silage. This observation is consistent with findings on the same silages that voluntary intake of the ED and HD silages was greater than consumption of the LM silage, although OM digestibilities were not affected by stage of maturity.

Key words:

• Wheat silage
• rumen
• cattle
• in situ digestibility