Illini BeefNet Papers
Estimates of the extent of DM and CP degradation were determined for alfalfa, bromegrass, and endophyte-free tall fescue, and endophyte-infected in four stages of maturities across the first spring growth. Forages were collected form April 27 to June 6, 1994, chopped and incubated in two rumen cannulated Simmental x Angus steers.
Patterns of DM and CP degradation were fitted using a non linear model, and the extent of degradation (ED) was estimated using a rate of passage of 6.0%. The ED were regressed using days after May 12 for alfalfa, and days after April 27 for grasses, as the independent variable. The ED of DM (EDMD) and CP (ECPD) decreased in alfalfa at a rate of .69%/d and of .40%/d for EDMD and ECPD, respectively, from May 12. The estimated EDMD in early bud (5/20) and early flowering (5/26) were 69.6% and 67.5%, respectively. The EDMD and ECPD decreased in grasses at a rate of .75%/d and .39%/d, respectively from April 27. The estimated EDMD for tillering (4/27) and stem elongation (5/12) were 68.8% and 57.5%, respectively. The EDMD was always higher than ECPD. For the first spring growth, the grazing of grasses at their maximal EDMD (tillering) was 15 d before compared to the grazing of alfalfa at the early flowering stage, recommended for the grazing initiation. If grazing starts at grass tillering, alfalfa will be at early to mid vegetative stage. If grazing starts when alfalfa is at early flower, grasses will lose almost 10% of EDMD, and it will also not be possible to have a high efficiency of utilization of the standing forage during grazing.