Escape Protein Supplementation of Yearling Steers Grazing Smooth Brome Pastures

Abstract

Two grazing trials utilizing individually supplemented yearling steers were conducted to study the effect of supplemental escape protein on steer performance during the active growth periods, spring and fall, of smooth brome (Bromus inermis). Graded levels (0, . 11, .23 and .34 kg.head-l.d-l) of an equal-proteinbasis mixture of bloodmeal and corn gluten meal were offered daily, replacing corn starch, which was used as the negative control. All steers received 582 g supplemental dry matter per day. Supplementation with escape protein improved daily performance in both spring (P<.01) and fall (P<.02). Analysis of pooled data from both trials indicated a linear (P<.01) and quadratic (P<.05) increase in steer performance with increasing level of escape protein in the diet. Analysis of grass samples collected throughout and composited over each trial demonstrated that grass protein was highly degraded in the rumen. Using a modified dacron bag technique, 12-h degradability was found to be 80 to 90% of the potentially digestible protein fraction. Rates of protein degradability were 14 and 11.7%/h. Assuming 5%/h rate of passage, escape protein was calculated to be 9.2 and 13.1% of total protein. As a result of the significant growth response observed above that of the energy-supplemented controls and the high ruminat protein degradabilities of the grass observed in the laboratory, it was concluded that growing ruminants grazing actively growing smooth brome pastures were deficient in metabolizable protein.

Relationships Between In Situ Protein Degradability and Grass Developmental Morphology

“…Warm season grasses tend to degrade more slowly in the rumen than do cool season grasses ( 2 ) . Anderson et al ( 3 ) reported that at least 80% of the digestible N of smooth bromegrass ( Bromus inermis Leyss.) was ruminally degradable.…”

Effects of supplemental protein sources during the grazing period on performance, ruminal characteristics and blood constituents in early weaned growing Wagyu steer calves

“…1988). Some studies have shown increased growth performance in calves supplemented with high RUP during the grazing period (Anderson et al . 1988; McCann et al .…”

“…Anderson et al . (1988) indicated that ruminants might still be deficient in metabolizable protein, in spite of high crude protein contents in actively growing grasses.…”

Ruminal degradation of switchgrass, big bluestem, and smooth bromegrass leaf proteins

“…These researchers suggested that the apparent increase in escape protein of warm-season grasses might have been due to protection of the RUBPcase protein molecule by the bundle sheath cell. Anderson et al (1988) and Blasi et al A compartmentalization of photosynthetic enzymes occurs in C4 species; greater than 98% of the PEPcase is located in the mesophyll cells and greater than 98% of the RUBPcase is restricted to the bundle sheath cells (Chen et al, 1973;Huber et al, 1976). Significant amounts of RUBPcase exist in both C3 and C4 species.…”

“…Animals grazing cool-season grasses supplemented with ruminally undegradable protein sources had increased weight gains (Anderson et al, 1988;Blasi et al, 1991). Likewise, lack of responses to supplementation of ruminally undegradable proteins by animals grazing warm-season grasses has been verified (Blasi et al, 1991;Hafley et al, 1993).…”