Analysis of economic and physical results of two grazing management alternatives and supplementation in a milk production system

The present study compared the productive and economic results of two grazing management alternatives (A1 and A2) in a dairy farming operation during the autumn-winter season. In A1 the diet provided, in theory, 17% of its dry matter (DM) as grazed herbage (Lolium multiflorum), and 83% as a combined supplement (maize silage, maize grain, cottonseed and commercial concentrate) and grazing occurred daily from 8:30 to 14:30 h; , in A2 the corresponding percentages were 48 and 52 and grazing was from 11:00 to 17:00 h. Eighty first-lactation Argentine Holstein cows (500 ± 30 kg liveweight), grazed in two groups in different paddocks. Chemical composition of the herbage on offer was determined, as was animal behavior at pasture and herbage intake. Milk production and composition and economic returns above feed costs were evaluated. Relative to A1, A2 herbage showed higher percentage content of soluble carbohydrate (CHS; 14.5 ± 3.4 vs 22.1 ± 6.9) and lower crude protein (CP; 22.2 ± 1.9 vs 20.9 ± 1.0), thus a lower CP/CHS ratio (1.6 ± 0.4 vs 1.0 ± 0.2). Cows managed under A2 consumed less supplement and total DM, but slightly more estimated metabolizable energy by virtue of greater daily herbage intake (4.4 ± 0.8 vs 8.7 ± 1.0 kg MS). This group also dedicated a greater proportion of time to grazing than A1 cows and achieved higher daily milk yield (23.7 vs 26.4 L). Also in A2 the economic return was 26% and 11.5% higher per cow and per litre of milk, respectively. The results favor A2 over A1 and suggest that milk yield could be increased and feed costs reduced in the autumn-winter season by use of this alternative.