management
Importance of Forage Analysis; Making Sure Nutrient Requirements are Met Heather Smith Thomas
Winter forages may need supplementation with protein or minerals. Jeremy Martin, PhD (ruminant nutritionist and reproduction manager, Great Plains Livestock Consulting) says it’s important to sample and test forages, especially after unusual weather patterns that may affect growing conditions. “We always recommend testing, even on lower-quality cheaper ingredients of cattle diets. Cost of tests, relative to potential savings, is so small there’s no way to justify not doing it.” It can be costly if you oversupplement or under-supplement, so you need to know the nutrient values of your feeds. “Ideally, you’d test forages or silages. Any small grains hay should be tested, because nitrates are potentially an issue with them,” says Martin. Warren Rusche, SDSU Extension Beef Feedlot Management Associate, says weather conditions in some regions made it more difficult to put up hay or harvest crops. “One of the things we’re concerned about is people relying on book values in terms of nutrient content. You need to know what the nutrient values of your specific feeds actually are,” he says. Janna Block, North Dakota State University Livestock Systems Specialist, says hay samples after harvest, or before purchase, gives you a chance to evaluate hay and determine which group of cattle to feed which hay. “For protein, cattle need a bare minimum of 7% in the diet. Below that level, microbial efficiency in the rumen declines,” she says. There won’t be enough protein to “feed” the microbes that ferment
and digest forage. Digestion slows and a cow can’t get adequate nutrients from what she’s eating, and also can’t eat enough to sustain herself, so she loses weight. Forage that’s only 7% protein (and 50% TDN (total digestible nutrients)) might work for the mid-gestation dry cow, but is inadequate for cows in late gestation. “They need forages that are at least 55 to 58% TDN and 8 to 9% protein, to support fetal growth. This will also depend on condition of the cow. If you are trying to feed a thin cow to pick up in body condition she’ll need more nutrient-dense feed,” says Block. “Cows in late gestation/ early lactation have the highest requirements—about 60% TDN and about 11% protein. This is a rule-of-thumb way to evaluate your forages and match them with various production groups. First-calf heifers have high requirements for growth as well as supporting a fetus,” she says. It’s hard to create a ration for beef cattle without a forage analysis since nutrient values can vary so much, even within the same type of plants. Brome grass hay could be 6% protein or as high as 12% depending on stage of maturity and weather conditions while growing and during harvest. “When feeding grass hay we need to know the protein level,” says Rusche. “If it’s 9 to 9.5% protein, we won’t need additional supplement, but if it’s only 7% that’s a different story. The rule of thumb I was taught is that cattle need something that’s at least 8%. If it’s below 8% and we supplement with protein we see improved digestibility and increased feed intake.” Make sure cattle are eating enough, especially in cold weather. “If they don’t eat enough, and the forage is not very digestible, we’ve created an energy deficit in those pregnant cows,
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Charolais Connection • March 2021
and set ourselves up for poorer calf health, poor colostrum quality, and poor rebreeding—so we didn’t save money by not purchasing protein,” says Rusche. After calving, the cow needs even more protein for lactation. An investment in protein supplement when it’s needed will always pay off, but you don’t know if you need it unless you test your feeds. Block recommends sampling each batch of hay, based on number of bales in each lot, and a lot consists of all the hay (same species) harvested off the same field under the same conditions (within a 48-hour period). “Some people might just sample what they think is their worst hay, to know what the bottom level is, but we can’t put together a nutrition program without a total feed analyses, to be able to target when you’d want to feed certain forages or might need a supplement,” she says. “Any feed test we do is only as good as the sample we send off, so we want to make sure the sample actually represents the feeds we will be using,” Rusche explains. A sample should be taken from each field, and each cutting of hay, because these cuttings may be different in their stage of maturity. “If it’s grass hay, we may have started harvest at boot stage and ended up with some fields that were already headed out by the time we finish harvest, and those will be very different in quality. There may also be species differences, or soil differences in certain fields. One field may have had more manure on it, or caught more rain,” says Rusche. “Then we must make sure we’re sampling that particular lot of hay uniformly and not just pulling cores off the bales we can get to the easiest. We need to take about 20 cores throughout that batch of hay to get a
