The Important Of Assigning Quality Forages

US - Weather delayed the 2009 silage season for dairy producers, but the time to choose hybrids for next season has come.
calendar icon 21 December 2009
clock icon 3 minute read
University of South Dakota

South Dakota Cooperative Extension Dairy Specialist Alvaro Garcia said that high corn prices could lead producers to consider replacing those portions of their dairy diet with highly digestible forages, but he reminds producers that matching the right ration to the right cows is also important.

“Hybrids like brown midrib (BMR) have less concentration of lignin, and that results in improved fibre digestibility,” Mr Garcia said. “A recent research trial evaluated a medium-tall, forage-quality hybrid and a BMR variety, and the BMR was ensiled in both processed and unprocessed forms. The forage-quality hybrid was ensiled processed. The theoretical length of cut was similar for both silages and set at 19 millimeters, with a roller clearance of two millimeters for the processed silages.”

Mr Garcia said the trial found that the BMR had less lignin than the forage quality hybrid.

“The starch was slightly higher in the forage-quality hybrid, 32 per cent, and the pH was lower,” said Mr Garcia. “More intact kernels remained in the unprocessed BMR when compared to the processed silages, and the processed and unprocessed BMR silages were 30 per cent more digestible than the forage quality hybrid.”

Greater digestibility means less nutrients are excreted in the manure that will eventually have a negative environmental effect.

The greater digestibility can offset the reduction in yield of the BMR, provided the cows are able to respond with production, Mr Garcia said. The trial had feedstuffs incorporated in the dairy ration at the following percentages:

  • Corn silage - 42 per cent;
  • Concentrate - 40 per cent
  • Alfalfa silage - 10 per cent
  • Alfalfa hay - 8 per cent

    Cows fed the ration with BMR ate more dry matter, 5.5 pounds, and produced more milk, 6.4 pounds, than those fed the forage-quality hybrid.

    “This response in milk production has been attributed to the fact that cows fed the forages with higher digestibility are able to eat more,” Mr Garcia said. “In spite of the higher intake, an additional 40 cents in feed almost doubled the milk dollars returned. Therefore, it's important to note that corn silage hybrids have to be selected based on the cow response.”

    Producers should evaluate these corn silage hybrids by their tonnage yield, but more importantly, by how much additional milk they help to produce. A milk-per-acre index can aid in this evaluation.

    Mr Garcia said the milk-per-acre selection index from the University of Wisconsin combines yield and quality into a single term allowing an easier ranking of forages and hybrid selection. Using this information, the milk-per-ton of corn silage is estimated, and then multiplied by the silage yield to calculate the amount of milk produced per acre of corn silage.

    The research of Roth and coworkers from Penn State University and the W.H. Miner Agricultural Research Institute suggest that response to improved plant digestibility can compensate for dry matter yield losses of BMR varieties.

    “This can happen if the cows are able to respond with production,” Mr Garcia said. “In low-producing herds, or in groups within the herd with low production, but still adequate genetic potential for milk production, economic responses to improved corn silage digestibility were greater than those observed with the high producing herds or groups that were already milking to their potential.”

    Granted, even if adequately, fed high producing cows do not respond to the substitution with forages of higher digestibility, their inclusion reduces the need for high-energy supplements and the overall daily feed cost per cow.

    Mr Garcia said this underscores the economic importance of assigning the right forage to the right animal category regardless of the corn silage hybrid selected.

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