Date of Award

Winter 2014

Project Type

Thesis

Program or Major

Animal Sciences

Degree Name

Master of Science

First Advisor

André F Brito

Second Advisor

Peter S Erickson

Third Advisor

Michal Lunak

Abstract

The objective of this thesis was to evaluate the effects of supplementing a pasture-based diet with ground flaxseed (GFLAX) on milk production and composition, blood parameters, digestibility, ruminal characteristics, nitrogen excretion, methane (CH4) and carbon dioxide (CO2) production, and income over feed cost (IOFC). Twenty organically-certified lactating Jerseys were blocked by milk production and days in milk (DIM) and randomly assigned to 1 of 2 treatments: 1) control (soybean meal and ground corn grain as 10% of total diet dry matter (DM) or 2) GFLAX as 10% of total diet DM. Treatments were top-dressed onto a 25% mixed grass-legume baleage, 23% grain meal, and 2% liquid molasses total mixed ration (TMR) (% of diet DM); pasture composed the remaining 40% diet DM. The study extended from June 8 to September 27, 2013 with 4, 28-d periods with the last 7 d used for data and sample collection. Dry matter intake, milk production, and milk component yields and concentrations were not affected by GFLAX supplementation. Feed efficiencies, energy corrected milk, and 4% fat corrected milk did not differ between treatments. Body weight, body condition score, plasma nonesterified fatty acids, and serum cortisol showed no difference due to GFLAX supplementation. Apparent total tract DM digestibility was lower (P = 0.04) in cows on the 10% GFLAX treatment. Dietary treatment did not affect ruminal pH, individual or total volatile fatty acid concentrations. Cows receiving the 10% GFLAX diet had (P < 0.01) higher proportions of propionic acid in collected ruminal fluid. However, enteric CH4 and CO2 production did not differ between diets. Nitrogen intake (P = 0.01) and urinary urea N excretion (P = 0.03) were higher in cows on the 10% GFLAX diet due to higher crude protein concentrations of GFLAX. Milk fatty acid composition was altered by dietary flaxseed supplementation. Increases in concentrations of monounsaturated fatty acids (P < 0.0001) and n-3 fatty acids (P < 0.0001) with decreases in n-6 fatty acids (P < 0.0001) were detected in cows consuming 10% GFLAX creating a nutritionally enriched fatty acid profile in regards to human health. A lower IOFC was noted when GFLAX was included in the diet compared to the control ($4.61 vs. $5.53/cow/d, respectively), if premiums for nutritionally enriched milk are offered in the future, it may help offset the price differential.

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