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Use of long-chain saturated fatty acid supplements in lactating dairy cows
Long-chain saturated fatty acid (LCSFA) supplements are used to increase energy density of diets and milk fat yield or energy balance in dairy cows. However, production responses to LCSFA vary greatly, which could be from differences in fat type, diets, and physiological states of cows. Supplements of LCSFA are comprised primarily of stearic and (or) palmitic acids. In cows past peak lactation, palmitic acid (99% purity), compared with a control diet with no supplemental fat, increased yields of milk (46.0 vs. 44.9 kg/d, P=0.04), milk fat (1.53 vs. 1.45 g/d, P<0.01), and 3.5% fat-corrected milk (3.5% FCM; 44.6 vs. 42.9 kg/d, P<0.01) with a similar response for cows across a wide range in milk yield. In a similar experiment, stearic acid (98% purity) increased DMI (26.1 vs. 25.2 kg/d, P=0.01) and yields of milk (40.2 vs. 38.5 kg/d, P=0.02), milk fat (1.42 vs. 1.35 g/d, P<0.01), and 3.5% FCM (40.5 vs. 38.6 kg/d, P<0.01), with a greater response for high yielding cows (linear interaction P<0.10). However, recovery of additional fatty acids consumed as additional yield of milk fatty acids was only 11.7% for palmitic acid and 13.3% for stearic acid supplementation. Supplementation of LCSFA (>85% saturated, 46% stearic acid and 37% palmitic acid) increased DMI (23.6 vs. 22.2 kg/d, P=0.04) and tended to decrease milk yield (46.6 vs. 49.7 kg/d, P=0.10), improving energy balance (-12.0 vs. -17.3 Mcal/d, P=0.01) and BCS (3.0 vs. 2.7, P=0.02) when fed during the first 4 wk postpartum in 20% and 26% forage NDF diets. However, postpartum supplementation of LCSFA interacted (P<0.10) with forage NDF concentration for 3.5% FCM yield when cows were fed a common diet from 5 to 10 wk postpartum: LCSFA decreased 3.5% FCM yield in the 20% forage NDF diet (51.1 vs. 58.7 kg/d), but not in the 26% forage NDF diet (58.5 vs. 58.0 kg/d). Supplementation of LCSFA might benefit lactating dairy cows in some cases but results are dependent upon fat supplements fed, diet, stage of lactation, and milk yield of cows. Further work is needed to clarify these situations as well as the marginal economic return, if any, of specific LCSFA supplements under different situations.
Keywords: milk fat, prilled fat, saturated fatty acids