Livestock producers don’t choose to deal with inferior quality forage, but there are often no options when harvested forage is less than optimal.
“Many things can happen that are out of our control,” said Dr. Gabriel Ribeiro, assistant professor, Saskatchewan Beef Industry chair. “We need to find ways to deal with other alternatives.”
The definition of “low-quality forage” varies, but it’s essentially the low potential of a forage to promote gain or milk production along with palatability, digestibility and nutrient content. “Intake and digestibility are the key factors,” said Ribeiro. “Palatability affects intake.”
Forages such as late-maturity hay, stockpiled forage, corn stover and drought-stressed crops are potentially low in quality. Silage can also be poor quality despite being cut and stored properly. Forage analysis to determine nutrient content can help estimate forage quality, and if the forage proves to be adequate to meet nutritional requirements of the animals, there’s no need to supplement the diet.
Most low-quality forages are low in crude protein, usually lower than 7%. Low-quality forages are high in NDF (neutral detergent fiber), ADF (acid detergent fiber) and lignin. Such forages have low digestibility (below 50%), which means less available energy. Animals consuming a low-quality forage diet have lower dry matter intake, resulting in reduced gain.
Ribeiro said abomasal impaction is another negative impact of low-quality forage, especially in winter. “As we feed lower quality forages that are lower in digestibility and energy, it can promote impaction,” he said. “That’s most common in cold months because cattle start to eat more forage to produce heat and maintain body temperature. Because the feed is such low digestibility, it will impact and even cause death.”
An important factor in feeding low-quality forage is water availability. Expecting livestock to eat snow while on low-quality forage is unacceptable and presents an animal welfare issue. Water is also critical for maintenance of rumen microbes.
Ribeiro said it’s important to understand the digestive process when feeding low-quality forage.
“Low-quality forage is high in fiber,” he explained. “Fiber digestion happens in the rumen. Digestion in the rumen is not by enzymes from the animal but by the microbial population such as protozoa, bacteria and fungi that all work together to break down fiber. To break down fiber, microbes need to attach to the fiber, then the microbes produce enzymes to break down the fiber. This is a slow process, and that’s why it’s a problem.”
In the rumen microbiome, microbes work together to degrade fibrous substances and produce volatile fatty acids (VFAs) and microbial protein. The VFAs become the source of energy for the animal, while microbial protein provides protein.
“In low-quality forages, less than 50% is digested and is lost in feces,” said Ribeiro. “Don’t just think about animal requirements – also think about the rumen microbes’ requirements. Microbes that are breaking down fiber have requirements and they are the ones doing the hard work.”
Water must be available in the rumen to supply a medium for fermentation. Also required is nitrogen in the form of ammonia. A urea and molasses tub doesn’t do much to supplement low-quality forage because rumen microbes require more than non-protein nitrogen – they also need feed protein in the form of amino acids and peptides so microbes can proliferate and digest fiber.
For producers who must feed low-quality forage, Ribeiro has some tips to improve digestion. First, group animals according to nutritional requirements. “A younger animal cannot digest fiber as well as an older animal,” he said. “A dry cow has a lower requirement than a lactating cow or a cow in the last third of gestation. We can direct lower quality forages to animals that can deal with them better. We can save money and make better use of the feeds we have.”
Consider diet formulation as a strategy. Have feedstuffs analyzed and plan supplementation according to results. Post-harvest treatments can also help digestibility. Low-quality forages will likely require energy supplementation. Small amounts of starches/sugars can help rumen microbes digest fiber. However, large quantities of cereal grains (starches) can negatively impact rumen pH.
“The animal eats the grain very quickly,” said Ribeiro. “That can cause reduction in rumen pH because it ferments quickly, and that can reduce fiber digestion.” He suggested feeding large amounts of cereal grains in several smaller portions to avoid negative digestive impact.
Some supplemental energy feeds such as oilseed, oilseed cakes or screenings are high in fat and provide energy and protein. However, too much fat can reduce fiber digestion, so Ribeiro suggested diets with less than 6% fat in total diet dry matter.
Minerals and vitamins are essential, and Ribeiro urges cattlemen to avoid scrimping on these essentials. Free-choice intake should be monitored to ensure animals are consuming enough to meet requirements. Animals on low-quality forage crave salt, so it’s important to make free-choice salt available.
“By eating more salt, animals drink more water, which makes passage rate through the rumen faster,” said Ribeiro, “and that can increase the fermentation rate of microbes.”
Physical treatments such as chopping, grinding or pelleting can potentially aid in digestion.
“With chopping, we don’t see consistent improvement in animal performance,” said Ribeiro. “The advantage is reducing waste and sorting. Grinding can help increase feed intake, mostly for young animals. Grinding and pelleting is what can really improve feed intake, digestion, average daily gain and feed-to-gain ratio.”
Ribeiro said grinding/pelleting reduces digestibility due to faster rumen passage rate. Grinding and pelleting also destroys the structure of the fiber, which reduces its physical effectiveness. The forage then acts more like a concentrate than a forage and can’t effectively maintain rumen pH and prevent acidosis. It’s important to consider the cost of grinding/pelleting and compare those costs with the cost of supplements.
Alkali chemical treatments such as sodium hydroxide and calcium hydroxide are sometimes used to improve poor forage. “They can partially solubilize some of the fiber and disrupt the fiber structure,” said Ribeiro. “They also promote faster rate of hydration when the forage reaches the rumen.”
Ribeiro noted that commercial feed additives such as prebiotics, probiotics and enzymes can potentially help aid in digestion, but said there are inconsistent results among products. He urged cattlemen to carefully weigh products’ costs and benefits.
by Sally Colby
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