Grazing systems focus on high production per acre at reduced costs
Published in Dairy Star November 20, 2009
Feeding costs are a high proportion of the total production costs on dairy farms. Other production costs continue to increase while the price of milk has been in precipitous decline. With grain prices expected to increase in the future, dairy farms will feel pressure to increase the feeding of high quality but low cost forages. Pastures and perennial forages that can be preserved for winter feeding will be a good source of high quality forage on many farms. Cows that perform well on high forage diets will be valuable.
Grazing systems are characterized by lower production per cow than conventional confinement systems. Instead, the focus is on high production per acre at reduced costs. The main nutritional influences on high milk yield from pasture are the amount of high quality pasture forage grown per land unit, the amount of pasture allocated per cow, pasture management, and amount and quality of supplement that is provided. Questions and opinions abound concerning whether pasture management should emphasize high utilization of pasture forage or increased pasture allocation, which can lead to increased amounts of refused forage and lower forage quality in subsequent rotations.
Irish researchers at the Moorepark Research Center in County Cork, Ireland, studied the effect of forage mass and pasture allowance on the performance of dairy cows. High forage mass was defined by a 31-day interval between grazing with 35% more forage mass than low mass with a 21-day grazing interval. High pasture allowance was 44 lb of pasture forage per head and the low allowance was 35 lb per head. Actual consumption ranged from 87 to 97% of available forage. Milk yield per acre for the year was highest for the low pasture allowance because more of the forage grown was utilized and was less mature when it was grazed. As the season progressed, forage quantity and quality began to favor the more closely grazed pastures. There was little difference in production per cow. Rainfall in Cork is greater than rainfall in Minnesota, where our pasture management in drought conditions must emphasize avoiding overgrazing in order to maintain a healthy forage stand.
Scientists in Ireland, France and New Zealand have been studying the effect of number of hours of grazing that cows are allowed each day. The prevailing view until recently has been that cows should be allowed as many grazing hours as possible. But there may be seasonal foul weather (Minnesota in October 2009) that places pastures at risk or use of feedlot supplementation when pasture is limited, which reduces hours of grazing time.
The Moorepark scientists compared: a) 22 hours of grazing, b) a 9-hour grazing between milking, c) 4.5-hour grazing periods after each milking, and d) 3-hour grazing periods after milking with mid-lactation cows milking 50 lb per day. Pasture forage intake was essentially the same for all of the treatments except a slight reduction in the cows that were restricted to a single 9-hour grazing period. There was no difference in milk production per cow. Cows that were allowed less grazing time ate more aggressively when they were allowed on pasture.
The French study compared: a) unrestricted access to pasture between milking, b) a 9-hour grazing period between two of the milkings, and c) 2.75 hours of grazing following each milking with unsupplemented cows. Each grazing period treatment was allotted to 30 lb or 50 lb of pasture supply. None of the cows with restricted time of grazing maintained the intake or production of the cows with unrestricted grazing time. Increased pasture allowance was most beneficial for cows with unrestricted hours of access to pasture.
The New Zealand study focused on behavioral adaptation of cows early in grazing bouts, with restricted access to pasture. Moderate restriction of available grazing time had no effect on daily intake when cows could adapt their behavior. Total grazing time was slightly less than 1 hour for each group, but cows with reduced time on pasture spent less time ruminating or being idle. They increased their bite size and bite rate.
International interest in identifying strains of cattle adapted to high or low input systems remains strong. Here in Minnesota, we are developing cross bred strains for different environments. There has been growing concern about decline in fertility and vigor in pure breeds. Scandinavians have emphasized health and fertility for 40 years with positive results. Ireland utilizes an economic breeding index in use since 2001 with weights for milk production (42%), fertility (37%), beef production (9%), calving performance (8%), and health (5%). High index Holstein bulls from North America or New Zealand demonstrate improved profitability over low index bulls. Index selection, as well as crossbreeding, offers opportunity to improve health and fertility, with a modest decrease in emphasis on yield.