Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)


Animal Sciences


David P. Marcinkowski

Second Committee Member

Rick J. Kersbergen

Third Committee Member

John M. Halloran


In the Northeast, winter-feed costs are the largest expense on organic dairy farms. This experiment evaluated the effects of forage and concentrate combinations on the nutrition, production and economics of winter-supplemented organic dairy cows in Maine. Two of three annual feeding trials have been conducted using two different organic forage systems, (all grass diet (GS) vs. grass/corn silage/summer annuals(AS)) and two concentrate supplementation strategies (commercial 20% protein grist (PG) vs. mix of commodities consisting of ground corn, roasted soybeans, soybean meal and triticale (CG)) analyzed in a 2-by-2 factorial system. Each ration was balanced using CPM-Dairy to equalize milk production and fed as a TMR to Holstein cows in early to mid lactation. The cost of the forages and concentrates used in each ration were based on current market value in Maine. The cost/cow/day of the rations ranged from $5.84 (AS/PG diet) to $6.89 (AS/CG diet) in Year I, and from $5.99 (GS/CG diet) to $7.03 (AS/PG diet) in Year II. Milk production and milk fat percentage were higher for the two rations balanced using CG (P< 0.05), but milk protein was unchanged in Year I. In Year II milk production, fat percentage and protein were not different between the four groups. In Year II MUN levels were lower for the AS groups (P<0.01), and lower for the AS/PG group (P<0.01). With regard to daily milk income over feed costs it was found that in Year I the GS/CG diet was the most profitable ($11.24), followed respectively by AS/CG ($10.78), AS/PG $10.32) and GS/PG ($10.20) diets. In Year II it was found that the GS/CG diet was the most profitable ($10.09), followed respectively by AS/PG ($9.93), AS/CG ($9.91) and GS/PG ($9.64) diets. Based on the results of the first two years, there appears to be an advantage to commodity grain based concentrate supplementation especially when utilizing a grass based forage diet over all other diets. While pellet grain concentrate supplementation with grass based forage diets appears to be the least efficient.