Submitted to: American Society of Animal Science Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2008
Publication Date: July 7, 2008
Citation: Scholljegerdes, E.J., Kronberg, S.L. 2008. Effects of supplemental flaxseed or corn on site and extent of digestion in beef heifers grazing summer rangelands in the northern Great Plains. American Society of Animal Science Proceedings. J. Anim. Sci. Vol. 86, E-Suppl. 2, p. 330. Technical Abstract: Six Angus heifers (367 ± 8.0 kg) fitted with ruminal and duodenal cannulas were used in a split-plot designed experiment to determine the effects of ground flaxseed or corn and advancing season on site and extent of digestion when beef heifers grazed summer range in the northern Great Plains. Starting on June 9, 2006 heifers were rotationally grazed on three 12 ha native pastures and were randomly allotted to one of three treatments being: no supplement (CON); a cracked corn-soybean meal supplement fed at 0.35% of BW once daily (CRN); or a ground flaxseed supplement fed at 0.2% of BW once daily (FLX). Supplements were formulated to be isonitrogenous and isocaloric on a TDN basis. There were three experimental periods that were 28 days in length with 18 d for diet adaptation and 10 d for diet sampling. Provision of supplement did not affect (P = 0.22) masticate IVOMD, however, between supplemented treatments, cattle fed FLX tended (P = 0.08) to select a lower quality masticate than CRN. Forage OM intake was not affected (P = 0.12) by supplementation nor was there a difference (P = 0.49) between CRN and FLX. A quadratic (P = 0.001) response was observed for forage OM intake as the grazing season advanced. Duodenal and fecal OM flow was not different (P = 0.39) across treatments. Therefore, true ruminal and total tract OM digestibility (% of intake) did not differ (P = 0.37 to 0.56) between CON and supplemented treatments and total tract digestibility was greater (P = 0.01) for CRN than FLX. Total duodenal N flow did not differ (P = 0.16) across treatments but responded quadratically (P = 0.03) with advancing season. True ruminal N digestibility was not affected by supplementation (P = 0.16 to 0.26). Likewise, ruminal NDF digestibility also did not differ (P = 0.26) with supplementation and CRN was not different (P = 0.22) from FLX. Total ruminal VFA decreased with supplementation (P = 0.04) and ruminal molar proportion of acetate was greater (P = 0.02) for FLX than CRN. Therefore, ground flaxseed appears to be a suitable energy supplement for cattle grazing summer rangelands.