High dairy payouts have encouraged more use of maize and whole crop silages, to increase milk yields by balancing diets, filling feed gaps, maintaining pasture cover, extending lactations, and increasing condition on cows. Silages need to be made and conserved well, and used efficiently to generate increased profits for dairy farmers, as they are not cheap to grow, conserve and utilise. Costs for growing and harvesting maize silage have been calculated to be about $3-4,000 per hectare.
Harvesting at the 2/3 milk line and about 35% dry matter (DM) is generally considered as the appropriate stage of maturity. Lower yields and effluent losses may result from early harvesting, and dry crops are more difficult to compact, which may increase aerobic spoilage after opening. Harvesters should be fitted with grain crackers to ensure all grains are broken, to improve grain digestibility.
Stack dimensions are important to help preserve silage quality after opening. Long narrow stacks tend to be better than short wide ones, as silage faces need to move back at least 30cm per day, possibly faster in hot humid conditions, when there is an increased risk of Clostridia getting established.
Stacks need to be well compacted, so fingers cannot be pushed into the face beyond the first knuckle. This will reduce air penetration of exposed silage faces, reducing opportunities for growth of moulds or yeasts. It is important to fill stacks quickly, cover them adequately, and weight the covers, to seal out air to prevent mould growth along the top and shoulders. Ideally stacks should be fenced against stock, baited for rats and other vermin, and protected from bird damage.
Silage cutters or shear grabs at feeding out will keep stack faces tidy and help minimise air penetration. Mouldy silage should not be fed to milking or pregnant cows, as digestibility and feed intakes will be low, and mycotoxins may reduce fertility. Stack faces should not be covered while feeding out, as this encourages growth of yeasts and moulds.
Silage making and utilisation is an exercise in minimising losses, at each stage in the process. The faster silages ensile, then the less dry matter and nutrients are lost, as bacteria consume sugars to produce the acids that preserve ensiled crops. Trials throughout the world have demonstrated the benefits of high quality silage inoculants, in speeding up this process, producing more and better quality and palatable silages, giving a good return on investments.
The most commonly used silage inoculants are those supplying high levels of homofermenting bacteria, but more recently farms, with issues regarding silage face stability, have used inoculants containing L. buchneri bacteria which produce acetic acid, which helps reduce growth of yeasts. The FDA stipulated a minimum level of 400,000 cfu/g wet material for claims of improved aerobic stability.
As featured in NZ Dairy Farmer