Effects of ground flaxseed on milk production, milk composition, and methane emissions in organically-managed Jersey cows during the grazing season

Abstract Text:

Our previous research feeding incremental levels of ground flaxseed (GFLAX) (0, 5, 10, or 15% of diet DM) to organically-managed Jersey cows linearly reduced yields of milk and milk components, DMI, and enteric CH₄ emissions. While milk yield did not differ significantly between 0% and 10%, 10% GFLAX significantly increased n-3 fatty acids and conjugated linoleic acid. Flaxseed is rich in n-3 fatty acids and energy; energy is a limiting factor to milk production in pasture-based diets. This study evaluated impacts of supplementing pasture with 10% of diet DM as GFLAX to Jersey cows on milk production and composition, and enteric CH₄ emissions. Twenty multiparous lactating organically-managed Jersey cows averaging 408 kg BW and 112 DIM were blocked by milk production and DIM and randomly assigned to 1 of 2 treatments: 1) control (soybean meal and ground corn grain mix as 10% of total DMI) or 2) ground flaxseed as 10% of total DMI. Treatments were top-dressed onto a 25% mixed grass-legume baleage, 23% grain meal, and 2% liquid molasses TMR (% of diet DM); pasture composed the remaining 40% DMI. The study extended from June 8 to September 27, 2013 with 4, 28-d periods with the last 7 d used for data and sample collection. Data were analyzed using the MIXED procedure of SAS with repeated measures over time; no treatment × period interaction was observed. Cows had access to mixed grass-legume pastures for about 16 h daily in a rotational strip grazing system. Cows were milked twice daily with milk production recorded each time. Milk samples were collected for 2 consecutive days and analyzed for fat and protein. A portable automated head chamber system was used for assessing CH₄ fluxes. Milk production did not differ significantly in cows supplemented (17.6 kg/d) or not (18.2 kg/d) with GFLAX. Similarly, concentration and yield of milk components did not differ significantly, averaging 4.20% and 0.76 kg/d for milk fat and 3.45% and 0.61 kg/d for milk protein. Intake of TMR was lower (P < 0.01) in cows with (10.5 kg/d) or without (10.8 kg/d) GFLAX supplementation. Methane emissions did not differ significantly, averaging 299 g/cow/d (control diet) and 295 g/cow/d (GFLAX diet). Feeding 10% of total DMI as GFLAX to grazing dairy cows had no negative impact on milk production and composition, but did not mitigate CH₄emissions under conditions of the current experiment.   

 Keywords: pasture, ground flaxseed, methane