STOCKING RATE AFFECTS PRODUCTION AND PROFITABILITY IN A ROTATIONALLY GRAZED PASTURE SYSTEM

Stocking rate is a key management variable in determining productivity and profitability of grazing systems, but it has not been adequately researched in the USA with high producing dairy cows. A replicated far mlet study was conducted to investigate the potential for improving da iry profitability through increasing stocking rates without influencin g milk yield per cow. The study was conducted at the Pennsylvania Stat e University Dairy Research and Education Center in University Park, o n pasture dominated by orchardgrass (Dactylis glomerata L.) and Kentuc ky bluegrass (Poa pratensis L.). Forty-eight high-producing Holstein c ows (Bos taurus) were rotationally grazed at seasonal stocking rates o f 1.0 (low, LSR), 1.3 (medium, MSR), and 1.6 (high, HSR) cows/acre, an d were fed grain at the rate of approximately 1 lb grain DM to 4 lb mi lk production during a 2 yr study. Stocking rate had a positive effect on pasture nutritional quality, particularly when growth was more vig orous, and had a negative relationship with the percentage of the past ure rejected by cows. Seasonal milk yield per cow (approximately 10 00 0 lb) and milk composition were not affected by treatments in either y ear. Consequently, milk production per acre was directly related to st ocking rate. An economic analysis of costs and returns indicated that profits per unit area of land increase with stocking rate-a $481/acre advantage was shown for the HSR over the LSR. In contrast, profits per cow decrease with stocking rate-the LSR showed a $36/cow advantage ov er the HSR. The optimal stocking rate for a given farm therefore will depend on individual farm resources (e.g., land, buildings, cows, etc. ), and can be adjusted to meet the constraints of those resources with out fear of significant adverse economic impact.