Forage DM intake (kg/day)
PHOTO: KOOS GROENEWOLD
GRAZING ▶▶▶
How does zero grazing measure up?
Climatic conditions, whether too wet or too dry, are often the deciding factors that persuade dairy farmers to use zero grazing as a management tool.
BY CHRIS MCCULLOUGH, FREELANCE JOURNALIST I
f the country is too hot, cows might be affected by heat stress. Zero grazing is a possible solution. Likewise, if the climate is too wet in a region, grazing cows could do a lot of damage, leaving zero grazing as the only option. That is
part of the dilemma many farmers face when deciding which feeding method is best suited to the conditions of their farms. As the term suggests, zero grazing is where grass is harvested in the field and transported to farmyards to be fed fresh to housed cattle each day.
Reasons for zero grazing There are a number of other reasons for carrying out zero grazing on a dairy farm. For example, farms may have blocks of grazing land in different areas, making it difficult to walk cows long distances to get to them. Another reason is that there could be too many cows in the herd to walk them all at once to fields. Fresh grass can also boost milk quantity and quality when fed to housed cows during summer. As grass is the cheapest form of feed for a dairy herd, zero
Figure 1 - Average weekly forage dry matter intake of cows offered zero grazed grass or grass silage produced from the same sward.
19 17 15 13 11 9 7 5
Date of harvest Zero-grazed grass 16 Grass silage
grazing could be a better option when other feed costs in- crease – depending on the cost of harvesting and hauling the grass to the cows, of course.
Advantages • Higher dry matter (DM) intakes with fresh grass • Utilisation of grass more efficiently and extension of the grazing season
• Better use of fields that are too far to walk cows to • Relative cheapness of grass means that using more of it reduces feed costs
• Freeing up of land to grow other feed on
Disadvantages • Can require extra labour and machinery costs to harvest and haul
• If weather is bad, harvesting can be difficult • Grass cut in the afternoon will have higher sugars and lower free nitrogen and fibre.
Whatever the reason, zero grazing is becoming very popular on many dairy farms across the world, but could feeding si- lage instead be a better option? Recent research by Agri-Food and Biosciences Institute (AFBI) in Northern Ireland has shown improved performance from cows offered zero-grazed grass compared to grass silage.
Silage study As it may be difficult to maintain a sward at the optimum quality for zero grazing throughout the season, AFBI asked how cows would perform if offered silage produced from a sward at the same stage of growth as is normally harvested for zero grazing. Offering very high quality silage, instead of zero grazing, could have a number of possible advantages, includ- ing reducing the need for harvesting to approximately once every four weeks compared to daily for zero grazing systems. Silage production is more weather dependent, and ensiling young leafy herbage can be challenging, especially later in the season. The study was conducted over 12 weeks between June and September in 2020. Fresh grass for zero grazing was cut daily and offered to a group of 18 mid-lactation dairy cows. Grass for silage production was cut once per week, from the same sward where zero grazing took place. Weather permitting, grass was tedded to facilitate wilting,
▶ DAIRY GLOBAL | Volume 9, No. 3, 2022
18 June 25 June 2 July 8 July 16 July 21 July 29 July
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