Effects of duodenal infusion of α-linolenic acid on nutrient digestion and production performance in dairy cows

The purpose of this study was to determine the effects of duodenal infusion of a high content of C18∶3 free fatty acid mixture on nutrient digestion,milk production,and milk composition in dairy cows.Four multiparous Chinese Holstein cows fitted with duodenal cannulas were administered with aqueous mixtures of α-linolenic acid(LNA;82.4% cis-9,cis-12,cis-15 18∶3;14.7% cis-9,cis-12 18∶2;2.8% cis-9 18∶1)or only the emulsifying ingredients in a crossover design,each period lasted 5 wk.Two of these cows received continuous increased LNA(0,30,60,90 and 120 g/d)for 1 wk for each amount,and the other 2 cows received only the carrier infusate.Measurements were made during the last 3 d of each infusion amount.The results showed that the dry matter intake and total tract apparent digestibilities of DM,OM,CP and ADF were not affected by LNA infusions.Milk production tended to decrease(18.54,17.17,16.94,15.9 and 16.28 kg/d for 0,30,60,90 and 120 g/d infusion amount,respectively;P=0.08)as LNA infusion increased but production of 4% FCM was not changed.Milk fat content tended to increase linearly with LNA infusion(4.01,4.12,3.96,4.32 and 4.41 g/100g;P=0.09),however,milk fat yield was not changed.Milk protein content was not changed by LNA infusion,whereas milk lactose content(4.56,4.60,4.68,4.59 and 4.57 g/100 g)and milk lactose yield(0.85,0.79,0.79,0.73 and 0.74 kg/d)were quadratically affected with the increase of LNA infusion(P0.05).The results indicated that increasing the amount of LNA supplied to the small intestine(120 g/d)of dairy cows had no effect on DMI and nutrient digestibility.Infusion of LNA did not affect milk protein or fat yield,but decreased milk lactose content and yield.