Maintaining cow productivity, while decreasing the proportion of concentrates may require cutting forages at an early stage of development with reduction in yield and persistence. Our objective was to use the whole-farm model N-CyCLES to assess the effect of 2 forage harvesting strategies on dairy farm profits, N and P balance, and greenhouse gas emissions, while optimizing the management practices required to achieve maximum profits. Three model Canadian dairy farms under contrasting climate (Maritimes, Central Canada, and Prairies) were built in the model. Adaptations made to the model included modification to crop rotations, adjustment in the optimization constraints, evaluation of crop production cost, evaluation of forage nutritive value and yield, and update in fertilization requirements. Two harvesting strategies of divergent intensity of alfalfa-based forages were compared within each region: HS1: frequent harvests at an early development stage producing highly digestible forages and HS2: less frequent harvests at the recommended development stage producing higher forage dry matter yields of medium digestibility. Highest dairy farm profits were achieved under HS2 for the 3 model farms. This is explained by the greater income arising from higher forage yields produced under HS2. Moreover, HS2 achieved better performance for most agro-environmental parameters when compared with HS1. These results suggested that harvesting forages at the usual maturity stage is more profitable and, allows for better agro-environmental performance than harvesting more frequently for higher nutritive value. Table 1. Effects of two different harvesting strategies on dairy farm net income, greenhouse gas emission, P and N balance

	Maritimes1			Central Canada2			Prairies3
	HS1	HS2		HS1	HS2		HS1	HS2
Profit ($/100 kg FPCM4)
Net income	10.3	12.2		20.4	22.2		22.1	24.0
Crop income	3.5	4.7		10.4	12.8		5.0	6.5
Greenhouse gas emission
Total kg CO2eq. FPCM (kg/yr)	1.4	1.4		1.3	1.4		1.3	1.3
Mineral balance g/kg FPCM
N	13.6	12.2		14.6	14.3		14.5	14.3
P	1.7	1.6		0.5	−0.1		1.0	1.3

¹63 cows; 513 584 kg/yr. ²71 cows; 613 841 kg/yr. ³144 cows; 1 212 875 kg/yr. ⁴Fat- and protein-corrected milk.