EVALUATION OF MEDIUM-CHAIN FATTY ACID SUPPLEMENTATION EFFECTS ON DAIRY COW PERFORMANCE AND RUMEN FERMENTATION
Creators: Burdick, Matthew 
Publisher: name: University of Alberta Library
Year: 2022

<p>Medium-chain fatty acids (MCFA) are fatty acids with chain lengths between 6-12 carbons and are primarily metabolized by the liver, however they may be absorbed and metabolized by intestinal mucosa. Medium-chain fatty acids provide the animal with available energy quicker as compared to other fatty acids. Additionally, MCFA have been shown to have strong antimicrobial properties due to the amphiphilic structure. The objective of this research was to evaluate effects of medium-chain fatty acid supplementation on productivity, plasma energy metabolite concentrations, apparent total tract nutrient digestibility, rumen fermentation, and rumen microbial profile of lactating dairy cows. Thirty (n = 8 primiparous, n = 22 multiparous) Holstein cows in mid-lactation (637 ± 68.5 kg of initial body weight, 98.5 ± 27.4 d in milk; mean ± standard deviation) were used in a crossover design with 28-d periods. The MCFA supplement, consisted of 25% MCFA (containing 32% C8:0, 21% C10:0, 47% C12:0 on DM basis) and 75% carrier ingredient, was fed at 0.25% of dietary DM, replacing dry ground corn in control (CON). Total inclusion of MCFA was 0.063% of dietary DM. No differences were observed in dry matter intake, apparent total tract nutrient digestibility and body weight change between MCFA and CON. However, there was a negative relationship between pretrial milk yield and animal response to MCFA treatment in body weight change; higher producing cows tended to increase body weight to a less extent when MCFA was supplemented. Milk and milk component yields did not differ between treatment groups. However, a negative relationship between pretrial milk yield and animal response to MCFA treatment in milk protein yield; higher producing cows decreased protein yield to a greater extent when MCFA was supplemented. The MCFA supplementation tended to have higher minimum rumen pH (5.66 vs. 5.54; P = 0.08), and decreased daily fluctuation range of rumen pH (1.17 vs. 1.40; P = 0.02) compared to CON. However, duration of acidosis (pH &lt; 5.8, min/d) did not differ between treatment groups and ruminal total volatile fatty acid concentration and its profile did not differ between treatment groups. For rumen microbiota, chao1 index of bacterial community tended to be lower (10.9 vs. 11.6; P = 0.07) whereas Shannon index did not differ in MCFA compared to CON, and both indices did not differ for archaeal and protozoan communities between treatment groups. The MCFA treatment increased relative abundance of an unidentified family of bacteria that belongs to the Mollicutes class (0.04 vs 0.01%; P = 0.02) and tended to increase relative abundance of an uncultured bacterium that belongs to the Bacteroidetes phylum (0.48 vs. 0.37%; P = 0.06). The relative abundance of Methanobrevibacter gottschalkii increased when supplemented with MCFA (5.14 vs. 4.92%; P = 0.03). These results suggest that supplementation of MCFA at 0.063% dietary DM may not affect overall animal performance or total tract nutrient digestibility, but stabilize rumen pH by affecting rumen microbiota.</p>