Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2008
Publication Date: 5/9/2008
Citation: Scholljegerdes, E.J., Kronberg, S.L. 2008. Influence of supplemental whole flaxseed level on forage intake and site and extent of digestion in beef heifers consuming native grass hay. J. Anim. Sci. 86:2310-2320. doi:10.2527/jas.2008-0864. Interpretive Summary: Feeding beef cattle diets high in n-3 fatty acids is warranted for livestock producers interested in enhancing the human healthfulness of meat products. Feeding flaxseed, which is high in linolenic acid (56% 18:3n-3), is a viable option for bolstering n-3 fatty acid concentrations in livestock diets and subsequent n-3 fatty acid concentration in ruminant products. In the current trial, 9 ruminally and intestinally cannulated animals were used to evaluate site and extent of digestion in beef heifers fed either 0.91 or 1.82 kg/d of whole flaxseed and consuming native grass hay. Feeding flaxseed reduced forage intake 0.687 kg/ kg of flaxseed fed. Flaxseed appears to be a fat source that will not hinder diet digestibility and will increase tissue supply of unsaturated fatty acids when fed under conditions described herein. However, more work is needed in this area to truly elucidate the efficacy of flaxseed for improving growth performance, tissue fatty acid composition, and reproductive success in forage-based production systems.
Technical Abstract: The objectives of this study were to evaluate the influence of supplemental whole flaxseed level on intake and site and extent of digestion in beef cattle consuming native grass hay. Nine Angus heifers (avg. BW 303 ± 6.7 kg) fitted with ruminal and duodenal cannulas were used in a triplicated 3 × 3 Latin square. Cattle were fed ad libitum chopped native grass hay (8.7% CP and 70.0% NDF, DM basis). All animals were randomly allotted to one of three experimental treatments being either no supplement (Control); 0.91 kg whole flaxseed; or 1.82 kg whole flaxseed on a DM basis. Supplemental flaxseed tended to decrease (linear, P = 0.06) forage OM intake. However, total OM intake did not differ (P = 0.29) with increasing levels of flaxseed. Total duodenal OM flow increased (linear, P = 0.05) with additional flaxseed in the diet and no differences (P = 0.29) were observed for microbial OM flow. True ruminal OM disappearance was not affected (P = 0.14) by supplemental flaxseed. Apparent lower tract OM digestibility increased (linear, P = 0.01) with level of whole flaxseed. Apparent total tract OM digestibility was not different (P = 0.41) among treatments. Nitrogen intake increased (linear, P < 0.001) with supplemental flaxseed. In addition, total duodenal N flow tended (P = 0.08) to increase with additional dietary flaxseed. However, true ruminal N digestibility did not differ (P = 0.11) across treatment. Supplemental whole flaxseed did not influence ruminal (P = 0.13) or total tract (P = 0.23) NDF digestibility. Ruminal molar proportion of propionate was increased (quadratic, P < 0.001). An increase in the duodenal supply of 18:3n-3 (P < 0.001), total unsaturated fatty acids (P < 0.001) and total fatty acids (P < 0.001) was observed with additional dietary whole flaxseed. Apparent postruminal 18:3n-3 disappearance tended to decrease (P = 0.07) as intake of flaxseed increased. Overall, the inclusion of 1.82 kg of flaxseed does not appear to negatively influence nutrient digestibility of a forage-based diet and therefore can be used as an effective supplement to increase intestinal supply of key fatty acids important to human health.