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Title: Incremental amounts of ground flaxseed decreases milk production but increases n-3 fatty acids and conjugated linoleic acids in dairy cows fed high-forage diets

Author
item RESENDE, TALES - Universidade Federal De Minas Gerais
item KRAFT, JANA - University Of Vermont
item Soder, Kathy
item PEREIRA, ANDRE - University Of New Hampshire
item WOITSCHACH, DIEGO - Universidade Federal De Vicosa
item REIS, RONALDO - Universidade Federal De Minas Gerais
item BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2015
Publication Date: 10/1/2015
Citation: Resende, T.L., Kraft, J., Soder, K.J., Pereira, A.B., Woitschach, D.E., Reis, R.B., Brito, A.F. 2015. Incremental amounts of ground flaxseed decreases milk production but increases n-3 fatty acids and conjugated linoleic acids in dairy cows fed high-forage diets. Journal of Dairy Science. 98:4785-4799.

Interpretive Summary: Improving the fatty acid profile of milk may have human health benefits. We looked at the effect of feeding increasing amounts of flaxseed to organic dairy cows on milk fatty acid profile and milk yield. Increasing flaxseed supplementation increased beneficial fatty acids such as omega-3 and conjugated linoleic acid, but also decreased the daily amount of milk produced, which would result in decreased farm income unless a substantial premium was paid by milk processors for these increased fatty acids in milk.

Technical Abstract: The objective of this study was to investigate the effect of incremental amounts of ground flaxseed (GFLAX) on milk yield and fatty acids (FA) profile, ruminal metabolism, and nutrient digestibility in dairy cows fed high-forage diets. Twelve multiparous Jersey cows averaging (mean ± SD) 112 ± 68 days in milk and 441 ± 21 kg of body weight and 8 primiparous Jersey cows averaging 98 ± 43 days in milk and 401 ± 43 kg of body weight were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Treatments were fed as a total mixed ration (63:37 forage-to-concentrate ratio) with corn meal and soybean meal replaced by incremental levels (i.e., 0, 5, 10, or 15% diet dry matter) of GFLAX. Orthogonal polynomial contrasts were used to test responses (linear and quadratic) from incremental levels of GFLAX. Milk yield decreased linearly in cows fed increasing amounts of GFLAX, which is explained by the linear reduction in dry matter intake. Except for milk protein concentration, which decreased linearly with GFLAX supplementation, no other changes in the concentration of milk components were observed. However, yield of milk protein and fat decreased linearly with GFLAX supplementation. The concentration of milk urea nitrogen also decreased linearly, which is possibly explained by the linear decrease in crude protein intake. No treatment effects were observed for plasma urea N and nonesterified fatty acids, serum cortisol, and body weight change. Milk odd-and branched-chain FA and saturated FA decreased linearly with GFLAX supplementation. Milk trans-11 18:1, a-linolenic acid, cis-9, trans-11 18:2, and the sum of n-3 FA all increased linearly and quadratically with GFLAX supplementation. Milk proportion of n-6 FA as well as the n-6-to-n-3 ratio decreased linearly in cows fed GFLAX. The ruminal molar proportion of acetate and butyrate decreased linearly with GFLAX supplementation, whereas that of propionate increased linearly resulting in decreased acetate-to-propionate ratio. Apparent total tract digestibility of nutrients either decreased or tended to decrease linearly in cows fed GFLAX. Overall, compared with the control diet (0% GFLAX), the diet with 15% GFLAX supplementation resulted in the lowest milk yield (–6.3%), but highest milk proportion of cis-9, trans-11 18:2 (+46.1%) and n-3 FA (+48.4%).