EFFECTS OF SUPPLEMENTAL FLAXSEED ON SITE AND EXTENT OF DIGESTION IN BEEF HEIFERS GRAZING SUMMER NATIVE PASTURE IN THE NORTHERN GREAT PLAINS[1],[2]
E. J. Scholljegerdes[3] and S. L. Kronberg3
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 allotted randomly to one of three treatments being: no supplement (CON); a cracked corn-soybean meal supplement fed at 0.32% of BW once daily (CRN); or a ground flaxseed supplement fed at 0.18% of BW once daily (FLX). Supplements were formulated to be isonitrogenous and isocaloric. The three experimental periods were 28 d in length with 18 d for diet adaptation and 10 d for intensive sampling. Provision of supplement did not affect (P = 0.22) masticate in vitro organic matter digestibility, however, between supplemented treatments, cattle fed FLX tended (P = 0.08) to select masticate with lower in vitro organic matter digestibility 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 with intake being lowest during sampling period 2 than either sampling period 1 or 3. 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, with sampling period 2 being lower than sampling period 1 or 3. True ruminal N digestibility was not affected by supplementation (P = 0.16 to 0.26). Likewise, ruminal neutral detergent fiber digestibility also did not differ (P = 0.26) with supplementation and CRN was not different (P = 0.22) from FLX. Total ruminal volatile fatty acid decreased with supplementation (P = 0.04) and ruminal molar proportion of acetate was greater (P = 0.02) for FLX than CRN. Ground flaxseed appears to be a suitable energy supplement for cattle grazing summer rangelands.
Key Words: Beef cattle, Flaxseed, Grazing, Growth, Intake
[1] Flaxseed for this study was graciously donated by the North Dakota Oilseed Council
[2] Mention of a proprietary product does not constitute a guarantee or warranty of the product by USDA or the authors and does not imply its approval to the exclusion of other products that may also be suitable. USDA, ARS, Northern Plains Area, is an equal opportunity/ affirmative action employer. All agency services are available without discrimination.
[3] Northern Great Plains Research Laboratory, USDA-ARS, Mandan, ND, USA