Lactational response of cows to different concentrations of calcium salts of canola oil fatty acids with or without bicarbonates.

Holstein cows (n = 24) averaging 39 d of lactation were used in a randomized complete block design during an 8-wk trial. From wk 1 to 4, diets contained 62% alfalfa silage and 38% concentrates (dry matter basis), and, from wk 5 to 8, diets contained 47% forage and 53% concentrates. The concentrates were increased for the second phase so that the effect of bicarbonates could be expressed more fully. Diets 1, 2, and 3 contained 2% of a blend of Na and K bicarbonates and 0, 2, or 4% of Ca salts of canola oil fatty acids (percentage of dry matter), respectively. Diet 4 contained the same percentage of Ca salts as did diet 3 but without bicarbonates. Dry matter intake decreased linearly (wk 4), and milk yield was altered quadratically (wk 4), as the percentage of Ca salts in the diet increased. Milk fat percentage (wk 8) and yield (wk 4 and 8), as well as milk protein percentage (wk 4 and 8) and yield (wk 4), decreased linearly as the percentage of Ca salts in the diet increased. Short- and medium-chain saturated fatty acids decreased linearly, and C18:0, trans-delta-11-C18:1, cis-delta-9-C18:1, cis-delta-11-C18:1, and C18:2 increased linearly, as Ca salts in the diet increased. Addition of Na and K bicarbonates to the diets that contained Ca salts increased milk and milk protein yields and increased the proportions of C18:2 in milk fat at wk 8. Dietary bicarbonates had no effect on the responses of other milk fatty acids to supplementation of 4% Ca salts of canola oil fatty acids.