1843
Effects of lysolecithin on milk fat synthesis and milk fatty acid profile of cows fed diets differing in fiber and unsaturated fatty acid concentration
Thirteen multiparous Holstein cows (> 70 DIM) were used in a cross-over design that tested the effect of lysolecithin under diets differing in fermentability and polyunsaturated fatty acid (FA) concentration. Experimental periods were 20 d and included two 10 d phases. During phase 1, a standard fiber and low fat diet was fed (32% NDF, no added oil) and during phase 2 a lower NDF higher oil diet was fed (30.5% NDF and 2% oil from whole soybeans and soybean oil). A 14 d washout period between experimental periods allowed milk fat recovery. Treatments were control and lysolecithin (10 g/d/cow of LYSOFORTE™brand, Kemin Industries, Des Moines, IA) extended in a ground corn carrier. Milk was sampled on d 0, 5, and 10 of each phase for determination of fat and protein concentration and FA profile. There was no effect of treatment or treatment by time interaction for DMI or milk yield, however on d 5 of phase 2 lysolecithin tended to decrease DMI (P < 0.10). There was a treatment by time interaction for milk fat concentration and yield (P < 0.05). Milk fat concentration was higher in lysolecithin on d 5 of phase 1, but decreased progressively in both treatments during phase 2. Milk fat yield was not different among treatments during phase 1, but was lower in lysolecithin on d 5 and tended to be lower on d 10 of phase 2 (P < 0.10). There was no effect of treatment or treatment by time interactions for milk protein concentration or yield. No treatment by time interactions were detected for the concentrations of milk de novo (< 16 C) or preformed (> 16 C) FA. Concentrations of de novo FA decreased, but preformed FA increased during phase 2 ( P < 0.001) and no treatment differences were detected at any time point. There was an effect of time, but no treatment by time interactions for milk trans FA isomers (P < 0.05). Briefly, trans 11 C18:1 and cis-9, trans-11 conjugated linoleic acid (CLA) decreased progressively during phase 2 as trans 10 C18:1 and trans-10, cis-12 CLA increased progressively. Lysolecithin increased milk fat concentration when feeding a higher fiber and lower fat diet, but decreased milk fat yield when feeding a lower fiber and higher fat diet, although biohydrogenation pathways were not modified.
Keywords: dairy cows, lysolecithin, milk fat depression