Ruminant Nutrition: Carbohydrates and Lipids

摘要

We evaluated the effects of fatty acid (FA) supplements with different ratiosof palmitic (C16:0) and oleic (C18:1) acids in low and high fat basaldiets on production responses of dairy cows. Thirty-six multiparous Holsteincows (50.2 ± 5.8 kg milk/d; 160 ± 36 d DIM) were used in a splitplotLatin square design. Cows were blocked by milk yield and allocatedto a main plot receiving either a low fat (LF) basal diet (n = 18) containingcottonseed meal and cottonseed hulls or a high fat (HF) basal diet (n =18) containing whole cottonseed. Diets were balanced for similar NDF(30.0% DM), starch (28.5% DM), and CP (17.5% DM). Within each plot a3x3 Latin square arrangement of treatments was used with 3 21 d periods.Treatments were: 1) control (CON; no FA supplementation), 2) FA supplementcontaining 80% C16:0 + 10% C18:1 (PA), and 3) FA supplementcontaining 60% C16:0 + 30% C18:1 (PAOA). FA supplements were fedat 1.5% DM and replaced soyhulls in CON. The statistical model includedthe random effect of cow within basal diet, and the fixed effect of treatment,basal diet, period, and their interactions. Treatment by basal dietinteractions were observed with FA treatments increasing lactose yield (P= 0.01) and tending to increase milk yield (P = 0.14) in LF but not in HF.Basal diet had no effect on DMI (P = 0.66) or milk yield (P = 0.62). Comparedwith LF, HF increased 3.5% FCM (46.7 vs. 50.2 kg/d; P = 0.04) andmilk fat yield (1.65 vs. 1.83 kg/d; P = 0.02) and tended to increase ECM(47.1 vs. 50.0 kg/d; P = 0.07). Results for FA treatments are presented inthe following order: CON, PA, and PAOA. PAOA decreased DMI (33.0,33.1, 32.0 kg/d; P < 0.01). FA treatments increased 3.5% FCM (47.4, 48.9,49.0 kg/d; P < 0.01), ECM (47.8, 49.0, 48.9 kg/d; P < 0.01), and milk fatyield (1.69, 1.76, 1.76 kg/d; P < 0.01) compared with CON but there wasno difference between FA treatments. In conclusion, a high fat basal diethad positive production responses while the addition of fat supplementsincreased milk fat yield, 3.5% FCM, and ECM regardless of basal diet.