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Title: Milk yield and somatic cell score of northeastern United States organic dairy farms during the grazing and non-grazing seasons

Author
item GALVAO, JOSE - Instituto Federal De Educação Ciência E Tecnologia
item BRITO, ANDRE - University Of New Hampshire
item RANGEL, ADRIANO - Universidade Federal Do Rio Grande Do Norte
item SILVA, JEAN - Consultant
item BENSON, FAY - Cornell University
item DARBY, HEATHER - University Of Vermont
item HAFLA, AIMEE - Agri-King, Inc
item Soder, Kathy
item KERSBERGEN, RICHARD - University Of Maine

Submitted to: American Dairy Science Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2017
Publication Date: 7/15/2017
Citation: Galvao, J., Brito, A., Rangel, A., Silva, J., Benson, F., Darby, H., Hafla, A., Soder, K.J., Kersbergen, R. 2017. Milk yield and somatic cell score of northeastern United States organic dairy farms during the grazing and non-grazing seasons. American Dairy Science Association Proceedings.100(2):292.

Interpretive Summary: No Interpretive Summary is required for this Abstract. JLB.

Technical Abstract: The objective of this study was to evaluate milk yield and composition of organically-certified dairy herds during grazing season (GS) and non-grazing season (NGS) in the Northeast region of the United States. Dairy Herd Improvement records of Holstein, Jersey, and Holstein-Jersey crossbred cows from May 2012 to June 2015 were obtained monthly from 14 herds in the states of New Hampshire (n = 3), Vermont (n = 3), Maine (n = 3), New York (n = 2), and Pennsylvania (n = 3). The length of GS averaged 160 d (May to November). A total of 14,246 observations including milk yield, 4% fat-corrected milk (FCM), concentrations of milk fat and true protein, and somatic cell score (SCS) were obtained. Seasonal effects (GS vs. NGS) were compared using the PROC GLM procedure of SAS. Herds averaged (mean ± SD) 38 ± 18 lactating cows, 148 ± 87 days in milk, 21.3 ± 8.04 kg/d of milk, 21.7 ± 7.52 kg/d of FCM, 4.26 ± 0.98% milk fat, 3.28 ± 0.45% milk true protein, and 2.54 ± 1.80 SCS (73 ± 44 × 10³ SCC/mL). All milk variables (mean ± SEM) analyzed herein were affected by season, except SCS (2.50 ± 0.04 vs. 2.52 ± 0.03 for the GS and NGS, respectively). Milk yield (22.0 ± 0.15 kg/d vs. 20.8 ± 0.12 kg/d), FCM (22.1 ± 0.14 kg/d vs. 21.4 ± 0.12 kg/d), and concentration of milk true protein (3.32 ± 0.01% vs. 3.29 ± 0.01%) were greater during the GS than NGS, which may be explained by improved forage nutritional value when comparing pasture with conserved feeds. Milk fat concentration was greater in the NGS (4.35 ± 0.01%) vs. GS (4.17 ± 0.02%). This increased milk fat concentration may have been caused by replacing pasture for conserved feeds with greater fiber content, or by a dilution effect caused by decreased milk volume (-1.20 kg of milk/d) during the NGS. Herd SCs suggest adequate year-round milking procedures and preventative mastitis protocols. However, farmers should adopt better supplementation strategies or implement forage-crop practices that improve conserved feed nutritional value to mitigate milk yield losses during the NGS.