Abstract #M211

# M211
Using milk somatic cell score to predict of milk yield losses of organic dairy farms in the northeast United States.
J. G. B. Galvão Jr.1, A. H. N. Rangel*2, A. F. Brito3, J. B. A. Silva4, A. F. Benson5, A. N. Hafla6, H. M. Darby7, K. J. Soder6, R. Kersbergen8, V. Brossillon9, 1Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte, Ipanguaçu, RN, Brazil, 2Universidade Federal do Rio Grande do Norte, Macaíba, RN, Brazil, 3University of New Hampshire, Durham, NH, 4Universidade Federal Rural do Semiárido, Mossoró, RN, Brazil, 5Cornell University Cooperative Extension, Cortland, NY, 6USDA-ARS, University Park, PA, 7University of Vermont, St. Albans,VT, 8University of Maine, Orono, ME, 9Ecole Supérieure d'Agricultures, Angers, France.

The objective of this study was to predict milk yield (MY) losses associated with milk SCS in organically certified dairy herds in the northeast region of the United States. Dairy Herd Improvement records of Holstein (HO), Jersey (JE), and Holstein-Jersey crossbred (HO×JE) cows were obtained monthly (May 2012 to June 2015) from 14 herds in New Hampshire (n = 3), Vermont (n = 3), Maine (n = 3), New York (n = 2), and Pennsylvania (n = 3). A total of 14,246 observations including MY (2 to 60 kg/d), DIM (5 to 320 d) and SCS (0 to 9) were obtained. Milk yield and SCS were analyzed using the PROC MEANS procedure of SAS. Milk yield averaged 21.3 kg/d across breeds, and 23.8, 17.7, and 22.3 kg/d for HO, JE, and HO×JE, respectively. As expected, primiparous cows had lower MY (18.9 kg/d) than multiparous cows (22.4 kg/d). The SCS for all herds averaged 2.54; it was greatest for HO (2.59), intermediate for JE (2.50), and lowest for HO×JE (2.46), and 2.20 and 2.68 for primiparous and multiparous, respectively. The following linear regression model was obtained using the PROC REG procedure of SAS: MY (kg/d) = 22.7 − 0.52 × SCS, with a confidential interval of 1.92 to 2.84 SCS. Based on this linear model, each unit increment in SCS over 1.92 would decrease MY by 0.52 kg. The maximum predicted MY losses corresponded to 0.48 kg/d, which is equivalent to 146 kg of milk in 305 d of lactation across all breeds. HO cows showed the greatest predicted MY losses on an absolute basis (0.32 kg/d), followed by HO×JE (0.28 kg/d) and JE (0.27 kg/d). However, when expressed as a proportion of 305-d MY, predicted MY losses corresponded to 2.83, 2.00, and 1.10% for JE, HO, and HO×JE, respectively. Predicted MY losses were lower in primiparous (0.17 kg/d) than multiparous (0.40 kg/d), corresponding to 1.27% and 2.59% of total lactation production, respectively. Overall, crossbred cows (HO×JE) resulted in less predicted MY losses during 305-d lactation, and multiparous cows require improved management to reduce SCS and MY losses.

Key Words: crossbred, losses, organic