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This Article Full Text (PDF) All Versions of this Article: jas.2007-0178v1 87/2/658    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Owens, D. Articles by O’Kiely, P. Search for Related Content PubMed PubMed Citation Articles by Owens, D. Articles by O’Kiely, P.

Rumen fermentation, microbial protein synthesis, and nutrient flow to the omasum in cattle offered corn silage, grass silage, or whole-crop wheat

D. Owens^*,, M. McGee^*, T. Boland and P. O’Kiely^*

^* Teagasc, Grange Beef Research Centre, Dunsany, County Meath, Ireland UCD School of Agriculture, Food Science and Veterinary Medicine, Belfield, Dublin 4, Ireland

mark.mcgee{at}teagasc.ie

Abstract

Objectives were to determine the relative effect of feeding corn silage (CS), fermented whole-crop wheat (FWCW), and urea-treated processed whole-crop wheat (UPWCW) compared to grass silage (GS), each supplemented with concentrates, on forage intake, ruminal fermentation, microbial protein synthesis, some plasma metabolites, and ruminal and total tract digestibility in cattle. Four ruminally fistulated steers with a mean BW 509 (SD 6.3) kg were used in a 4 x 4 Latin Square designed experiment with each period lasting 21 d. The omasal sampling technique in combination with a triple marker method was used to measure nutrient flows to the omasum with Co-EDTA, Yb-acetate, and indigestible NDF (INDF) as liquid, small particle, and large particle phase markers, respectively. Microbial N flow was assessed from purine base concentrations. Steers fed CS, FWCW, and UPWCW consumed 2.7, 2.4, and 2.6 kg/d more (P < 0.05) forage and total DMI, respectively, than those fed GS-based diets. Rumen pH (P = 0.07) and lactic acid (P = 0.11) concentration did not differ between the forages. Rumen concentration of ammonia N was highest for UPWCW and lowest for CS (P < 0.001). Total VFA concentrations were higher (P < 0.05) for CS than GS and UPWCW, with FWCW being intermediate. Acetate to propionate ratio (P < 0.05) was higher (P < 0.05) for UPWCW than the other forages, which did not differ. Apparent ruminal digestion of OM (P < 0.05) was lower for CS, FWCW, and UPWCW than GS. Ruminal NDF digestibility was higher (P < 0.01) for GS than the other forages, which did not differ (P 0.06). Total tract NDF digestibility was lower (P < 0.05) for UPWCW than the other forages with GS highest and CS and FWCW being intermediate. Starch intake was lower (P < 0.001) for GS than the other forages, but there was no effect of forage on omasal starch flow (P = 0.23) or ruminal digestibility (P = 0.88). Flow of non-ammonia N and microbial N was higher (P < 0.05) for CS, FWCW, and UPWCW than GS. Efficiency of microbial N synthesis was higher (P < 0.05) for FWCW than GS and CS with UPWCW being intermediate. Plasma beta-hydroxybutyrate concentrations were highest with CS and lowest for GS (P < 0.001), whereas concentrations of plasma urea were lowest for CS and highest for UPWCW (P < 0.001). In conclusion, feeding alternative forages to GS can significantly increase feed DMI and alter rumen fermentation and site of nutrient digestion when offered to cattle supplemented with 3 kg concentrate daily.

Key Words: cattle • corn silage • grass silage • nutrient flow • whole-crop wheat