PSVIII-A-6 - Effects of feeding ground whole flaxseed, defatted flaxseed meal and organic flaxseed meal on production performance, rumen fermentation, and total-tract nutrient digestibility in dairy cows

Abstract: This study aimed to determine the effects of feeding ground whole flaxseed and two types of mechanically-extracted flaxseed meals on dry matter intake (DMI), milk production and composition, ruminal fermentation characteristics, and total-tract nutrient digestibility in dairy cows. Twelve multiparous Holstein cows (122 ± 20 DIM at the start of the study) were used in a replicated 4 × 4 Latin square design with 4 dietary treatments. One square had 4 ruminally-cannulated cows that were used to determine dietary effects on ruminal fermentation characteristics and total tract nutrient digestibility. The 4 dietary treatments tested were a barley silage-based diet with canola meal (CM; 21.1% of diet DM) as the main protein source (designated CON), and diets containing ground whole flaxseed (designated GWF; 4.92% of diet DM), defatted flaxseed meal (designated DFM; 19.7% of diet DM), or organic flaxseed meal (designated OFM; 20.2% of diet DM) as partial replacements for CM. The crude fat contents of CM, GWF, DFM, and OFM were 3.20, 37.7, 9.9, and 12.9% (DM basis), respectively, and experimental diets were balanced for crude fat content (4.51%; DM basis). Experimental periods consisted of 18 d of dietary adaptation and 10 d of data and sample collection. Orthogonal contrasts were used to test for the following treatment differences: CON vs. GWF; CON vs. [DFM + OFM]; and GWF vs. [DFM + OFM]. Dry matter intake was lower (P < 0.01) for cows fed CON compared to those fed GWF and [DFM + OFM]. Milk yield tended to be greater (P = 0.06) for cows fed CON compared to those fed GWF (P = 0.06) and [DFM + OFM] (P = 0.06). Milk fat content and yield were unaffected by diet; however, milk protein content was lower for cows fed CON compared to those fed GWF (P = 0.001) and [DFM + OFM] (P < 0.001). Milk urea-N (MUN) concentration was greater (P ≤ 0.001) in cows fed CON compared to those GWF and [DFM + OFM]. Also, MUN concentration was lower for cows fed GWF compared to those fed [DFM + OFM]. Ruminal NH₃-N concentration was lower (P ≤ 0.04) in cows fed CON compared to those fed GWF and [DFM + OFM], but ruminal pH and short-chain fatty acid concentrations were unaffected by diet. Fecal N excretion (g/d) was greater (P < 0.01) for cows fed CON compared to those fed GWF and [DFM + OFM] and, therefore, total-tract CP digestibility was lower (P < 0.001) in cows fed CON compared to those fed GWF and [DFM + OFM]. In conclusion, partial replacement of CM with GWF or [DFM + OFM] increased DMI; however, it tended to reduce milk yield.