Grass silage has been unfairly treated: it is often excluded from the ration for a too high fiber content and low digestibility that can reduce feed intake and milk production. Yet, this poor reputation is largely undeserved. Grasses are an inexpensive and market-independent diet ingredient that, if managed properly, provide a good source of protein. They are suited to a wide range of soils and climates, and have the added benefit of being frost resistant. Compared to alfalfa, grasses are less sensitive to pests and dry faster than alfalfa. They often need just 24 hours for wilting, and even less in hot summer months. They also provide an additional option for applying manure. Table 1 lists the benefits of properly ensilaged grasses for cows, including high palatability, better gut health, improved milk composition and lower incidence of acidosis and metabolic disorders. The shift in rumen fermentation from non-fiber carbohydrate (NFC) to neutral detergent fiber (NDF) is particularly advantageous when mixed with high energy ingredients.
Table 1. Benefits of properly ensilaged grasses for cows.
Feed costs account for 55% to 70% of dairy operation expenses. By replacing purchased grain with forage produced in-house, the cost of the operation can be brought down significantly without compromising intake, passage rate and milk production. This is not wishful thinking. A number of farms across the world base their feed on 60% to 75% forage while maintaining high milk production of 35 to 45 l/day with optimum 25% to 35% neutral detergent fiber in the ration (Table 2). These farms are just as likely to use corn or grass silages.
Table 2. Ration from 16 farms with high forage percentage.
A ration perspective
In the ration, grasses provide higher fiber content and have good interaction with corn silage, which is lower in fiber and higher in non-fiber carbohydrates (in the grain portion). Grasses also have a higher proportion of digestible fiber compared to corn silage or alfalfa alone. They are a high-energy forage, making them a good alternative to the widely used straw. The fact that grasses slow the passage rate of feed through the cow is beneficial for those with lower nutrient demands, such as late-lactation cows, dry cows and heifers. Another reason to consider late-harvest grasses in rations for late lactation and dry cows is the lower potassium content of mature grass.