Effects of abomasal infusions of fatty acids and one-carbon donors on apparent fatty acid digestibility and absorption in lactating cows.
J. E. Rico*1, W. A. Myers1, R. Gervais2, J. W. McFadden1. 1Cornell University Ithaca, NY, 2Universitï¿½ Laval Quï¿½bec City, QC, Canada.
Our objective was to determine the effects of abomasal infusion of 16- and 22-carbon fatty acids (FA) on apparent FA digestibility. Five rumen-cannulated Holstein cows (214 ï¿½ 4.9 DIM; 3.2 ï¿½ 1.1 parity) were enrolled in a 5 ï¿½ 5 Latin square experiment with each experimental period lasting 6 d and 8-d washouts. Abomasal infusates consisted of (1) palmitic acid (PA; 98% 16:0 of total fat), (2) PA + choline chloride (PA+C; 50 g/d choline chloride), (3) PA + l-serine (PA+S; 170 g/d l-serine), (4) behenic acid (BA; 92% 22:0 of total fat), and (5) docosahexaenoic acid algal oil (DHA, 47.5% DHA of total fat). Emulsions were formulated to provide 301 g/d of total FA and were balanced to provide a minimum of 40 and 19 g/d of 16:0 and glycerol, respectively. Cows were fed a corn silage-based diet at 115% of expected intake. Diet was sampled (d 4—6) and composited. Feces were collected every 8 h on d 6—7 and composited for analysis. Diet and feces were stored in sealed plastic bags at −20ï¿½C until dried. Indigestible NDF was used as an internal marker to estimate fecal output and apparent nutrient digestibility, and was estimated as NDF residue after 240 h in vitro fermentation. Fatty acids were analyzed by GC-FID and grouped by carbon chain length. Data were analyzed under a mixed model including the effects of period, cow and treatment. Fisher's LSD mean separation was performed when P-value in F-test <0.05. Intake of 22C FA was higher in BA and DHA relative to PA, PA+C, and PA+S, whereas 16C intake was higher in PA, PA+C, and PA+S, relative to BA and DHA (P < 0.05). Digestibility of DM was highest in PA and DHA and lowest in BA (P < 0.05). Digestibility of FA was highest in DHA, intermediate in PA, PA+C, and PA+S, and lowest in BA (P < 0.05). Digestibility of 16C was lowest in BA and highest in PA, whereas 18C digestibility was lowest in BA and highest in DHA (P < 0.05). As anticipated, 22C digestibility was highest in DHA, relative to BA (99% vs. 58%, respectively, P < 0.01). We conclude that FA chain length and degree of saturation affect FA availability for absorption.
Keywords: cow, digestibility, fatty acid.