Production, milk and plasma fatty acid profile, and nutrient utilization in Jersey cows fed flaxseed oil and corn grain with different particle size

Abstract

We aimed to compare the effects of ground (GC) or cracked corn (CC), with or without flaxseed oil (FSO), on milk yield, milk and plasma fatty acid (FA) profile, and nutrient digestibility in Jersey cows fed diets formulated to contain similar starch concentrations. Twelve multiparous organic-certified Jersey cows averaging (mean standard deviation) 455 41.9 kg of body weight and 152 34 d in milk and 4 primiparous organic-certified Jersey cows averaging (mean standard deviation) 356 2.41 kg of body weight and 174 30 d in milk in the beginning of the experiment were used. Cows were randomly assigned to treatment sequences in a replicated 4 4 Latin square design with a 2 2 factorial arrangement of treatments. Each period lasted 24 d with 18 d for diet adaptation and 6 d for data and sample collection. Treatments were fed as total mixed rations consisting of (dry matter basis): (1) 0% FSO + 27.1% GC, (2) 0% FSO + 28.3% CC, (3) 3% FSO + 27.1% GC, and (4) 3% FSO + 28.3% CC. All cows were offered 55% of the total diet dry matter as mixed grasslegume baleage and treatments averaged 20% starch. Significant FSO corn grain particle size interactions were observed for some variables including milk concentration of lactose and proportions of cis-9,cis-12,cis-15 18:3 in milk and plasma. The proportion of cis-9,cis-12,cis-15 18:3 in milk and plasma decreased slightly when comparing GC versus CC in 0% FSO cows, but a larger reduction was observed in 3% FSO cows. Dry matter intake did not differ and averaged 16.1 kg/d across diets. Feeding 3% FSO increased yields of milk and milk fat and lactose and feed and milk N efficiencies, but decreased fat, true protein, and MUN concentrations and apparent total-tract digestibility of fiber. The branched-chain, <16C, 16C, and n-6 FA decreased, whereas 18C, cis-18:1, and trans-18:1 FA increased in 3% versus 0% FSO cows. No effect of corn particle size was observed for production and milk components. However, the apparent total-tract digestibility of starch was greater in GC than CC cows. Compared with CC, GC increased branched-chain, <16C, 16C, n-6 FA, and decreased 18C and cis-18:1 FA in milk fat. Overall, results of this study are more directly applicable to dairy cows fed low starch, mixed grass-legume baleage-based diets.