Production, milk fatty acid profile, and nutrient utilization in grazing dairy cows supplemented with ground flaxseed

Authors: ISENBERG, BRIANNA - University Of New Hampshire; Soder, Kathy; PEREIRA, ANDRE - University Of New Hampshire; STANDISH, REBECCA - University Of New Hampshire; BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2018
Publication Date: 12/24/2019
Citation: Isenberg, B.J., Soder, K.J., Pereira, A., Standish, R., Brito, A. 2019. Production, milk fatty acid profile, and nutrient utilization in grazing dairy cows supplemented with ground flaxseed. Journal of Dairy Science.102(2):1294-1311. https://doi.org/10.3168/jds.2018-15376.
DOI: https://doi.org/10.3168/jds.2018-15376

Interpretive Summary: Feeding flaxseed to dairy cows may alter fatty acid profiles that have human health benefits. However, there is limited information regarding supplementation of flaxseed to grazing dairy cows. We evaluated the effect of feeding flaxseed to grazing dairy cows on milk fatty acid profiles, milk production, and nutrient utilization. Beneficial fatty acids such as omega-3 increased with feeding flaxseed without affecting yields of milk and milk components. However, nutrient digestibility decreased slightly when flaxseed was fed. Increased milk price would be necessary to compensate farmers for increased feed costs and potential decreases in nutrient utilization associated with flaxseed supplementation compared with other supplements.

Technical Abstract: Twenty multiparous, organically-certified Jersey cows averaging (mean ± standard deviation) 111 ± 49 days in milk in the beginning of the study were used in a randomized complete block design to investigate the effects of supplementation of an herbage diet with ground corn-soybean meal (GRC-SBM) mix or ground flaxseed (GFLX) on animal production, milk fatty acids (FA), ruminal metabolism, and nutrient utilization. The study was conducted from June to September 2013, with data and sample collection taking place on weeks 4, 8, 12, and 16. Data were analyzed using the MIXED procedure of SAS with repeated measures over time. Cows were fed a diet formulated to yield a 60:40 forage-to-concentrate ratio consisting of [dry matter (DM) basis]: 40% cool-season perennial herbage, 50% partial total mixed ration, and 10% of GRC-SBM mix or 10% GFLX. Significant treatment by week interactions were observed for supplement DM intake, milk and blood urea N, and several milk FA (e.g., trans-10 18:1, S branched-chain FA). Overall, these responses are consistent with increased intake of FA from GFLX, supplement DM intake interaction, and potential depressive effects of GFLX oil on growth of certain population of ruminal microorganisms. No significant differences between treatments were observed for herbage and total DM intake, milk yield, feed efficiency, concentrations and yields of milk components, and urinary excretion of purine derivatives. Apparent total-tract digestibility of organic matter decreased, whereas that of neutral detergent fiber increased with feeding GFLX versus GRC-SBM mix. No treatment effects were observed for ruminal pH, ruminal concentrations of total volatile FA and NH3-N, and ruminal proportions of acetate and propionate. Ruminal butyrate tended to decrease, and the acetate-to-propionate ratio decreased in cows offered GFLX. Most saturated and unsaturated FA in milk fat were changed. Specifically, milk proportion of cis-9, cis-12, cis-15 18:3, S n-3 FA, and S 18C FA increased, while that of cis-9, cis-12 18:2, S n-6 FA, S odd-chain FA, S <16C FA, and S 16C FA decreased with feeding GFLX versus GRC-SBM mix. In conclusion, feeding GFLX did not change yields of milk and milk components, but increased milk n-3 FA. However, costs and industry adoption of premiums for n-3-enriched milk will determine supplementation of GFLX in pasture-based dairy farms.