Effect of duodenal infusion of trans10,cis12-CLA on milk performance and milk fatty acid profile in dairy goats fed high or low concentrate diet in combination with rolled canola seed

The effect of t10, c12- C18: 2 on milk production, and fatty acid ( FA) profile of milk fat was studied in 8 goats infused duodenally with t10, c12- C18: 2 ( 2 g . 10 h(-1)) during 3 days, followed by a 2- day infusion of skim milk ( SM). The goats were assigned to 4 diets in a factorial arrangement constituted by low ( L = 45%) or high ( H = 65% of the diet DM) percentage of concentrate without ( CS0) or with ( CS20) rolled canola seed ( 20% of the concentrate DM). Milk samples were collected before ( basal), and during the t10, c12- C18: 2 and SM infusions. The t10, c12- C18: 2 in milk fat increased from undetectable basal values to an average of 0.39% of total FA in the 3rd day of t10, c12-C18: 2 infusion. DMI, milk yield, and the contents and yield of milk fat, protein, and lactose were similar between basal and the t10, c12- C18: 2 infusion. The concentration of saturated FA with 4 to 16C did not change during the t10, c12- C18: 2 infusion, whereas C18: 0 increased, particularly in the milk fat of the CS20 group. The t10, c12- C18: 2 infusion increased the t10- and t11- C18: 1 ( except a reduction in t11- C18: 1 for the H- CS20 group), and it decreased the c9, t11- C18: 2 in milk fat, particularly for the H- CS20 group. The t10, c12- C18: 2 infusion reduced the c9, t11- C18: 2/ t11- C18: 1 ratio, particularly for the CS0 group. The results indicate that mammary lipogenesis in dairy goats was not decreased by t10, c12- C18: 2, however, the desaturation of long chain FA appeared to be equally affected as in dairy cows. This reduction in the desaturase index of milk fat could have been a direct effect of t10, c12- C18: 2, or mediated via an increase in t10- C18: 1.