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Management strategies impact milk fatty acid production and its relationship with milk composition.

S. C. Allen




Management strategies impact milk fatty acid production and its relationship with milk composition.
S. C. Allen*1, D. M. Barbano2, D. H. Poole1, J. Odle1, M. A. Drake1, S. H. Ward1. 1North Carolina State University Raleigh, NC, 2Cornell University Ithaca, NY.

Ten herds (n = 6 Jersey, JE, n = 3 Holstein, HO, n = 1 mixed) were enrolled to determine the impact of management practices and breed on milk FA composition. Bulk tank samples were collected monthly (7 samples/mo) and analyzed for milk and FA composition (de novo, DNFA; mixed origin, MOFA; and preformed, PRFA). Data were analyzed using PROC CORR and REG of SAS. A positive relationship was observed between milk fat %, protein % and DNFA in JE herds (r = 0.7473 and 0.6474, R2 = 0.5571 and 0.6474, P < 0.0001). HO herds showed similar results for fat and protein % (r = 0.7476 and 0.7433, R2 = 0.8653, respectively, P < 0.0001). DNFA and milk protein (kg) were positively correlated in JE and HO herds (r = 0.8053; R2 = 0.6474, JE; r = 0.8628, R2 = 0.7433, HO; P < 0.001). A stronger relationship was observed between MOFA and milk protein % with HO herds than JE herds (r = 0.8341 and 0.4849, R2 = 0.2329 and 0.6944 and 0.2329, respectively, P < 0.001). Herd visits were conducted quarterly to collect body condition and locomotion scores, stocking rates, and ration composition and particle size. Herds were classified as high and low de novo (HDN, LDN), mixed origin (HMO, LMO), and preformed (HPF, LPF) at each visit. Data were analyzed using PROC GLIMMIX of SAS; herd classification was the fixed effect. Means were separated using Fisher's LSD, and significance was declared when P ≤ 0.05. Compared with LMO herds, HMO herds fed more NDF (20.87% and 42.10%, respectively) and ADF (17.82% and 38.32%, respectively, P < 0.05). HO herds classified as HMO produced more milk fat than LMO herds (3.90 v. 3.56%, respectively, P < 0.05). FA content was not affected by body condition, stocking rate, or lameness (P > 0.05). The relationship between FA content and milk fat varies with breed and nutrition. Milk FA, particularly DNFA and MOFA, could be used as predictors of disorders or stressors to the cow.

Keywords: de novo, milk fat.