Annual ruminant nutrition conference held in Arlington

By JULIET BRISKIN | Central Texas Edition

Dr. Mary Beth Hall of the University of Florida discusses non-NDF carbohydrates and the value of manure evaluation. According to Hall the cows are always right. The cows cannot be trusted to balance their own rations but the signs they show will be correct. -Staff photo by Briskin

May 2, 2002 -- The Mid-South Ruminant Nutrition Conference once again brought dairy specialists from across the country to Texas to share information on the dairy industry and the animals that support it. The conference was held in Arlington April 24-25, and featured speakers from the USDA, Texas A&M University and the University of Florida.

Dr. Mary Beth Hall of the University of Florida addressed the conference on the importance of non-NDF (neutral detergent fiber) carbohydrates in the rations of high producing cows. In recent studies "the starchy diet always gave a higher protein percent and a higher number of grams of protein yield," explained Hall. "Starch in particular has been associated with the potential for high production but also with problems related to ruminal acidosis."

According to Hall a study that came out of the University of Florida showed that "if you look at starch as being 100 percent, being the standard, and you look at the microbial yield per gram of organic matter the sucrose (sugar) and the pectin (soluble fiber) gave a lower maximum microbial yield than did the starch." Hall went on to state that the NDF, which is "very slowly fermented, gave the lowest yield of all."

Hall stated that when studies looked at sucrose versus starch, the data showed that sucrose may increase butterfat yield. "There is some indication that sometime it (sucrose) may increase the rate of passage which changes the amount of nutrient the animal gets," explained Hall. "With an increased rate of passage you may squeek more microbes out of the rumen, but you may get less digestion in the rumen to make the microbes."

In the past, according to Hall, sugar has been thought of as "fast starch" but it is not. "The ruminal pH over time, post-feeding, was higher with molasses than for any other treatment," said Hall. "That flies in the face of the idea that sugars are a fast starch."

According to Hall one result found in feed studies is that sugars often reduced NDF digestion. "I can see corn doing that if it lowered the pH," said Hall, "but with molasses not lowering the pH the reason it might be doing this is competition for nitrogen."

Hall also discussed a study on increased forage in the cow's diet. "What was found was that as forage increases in the diet, starch increases, sugar decreases and soluble fiber stays about even," stated Hall. "Some of this change is probably due to the feeds that were available at the location of the study."

According to Hall, the cows are always right. "You can't trust them (cows) to balance their own rations," she said, "but the signs they show you will be correct and it is up to you to interpret them."

Deciphering the condition and contents of manure is one of the best ways to interpret how a cow is digesting her feed, according to Hall. "If you have manure that is very foamy, that is indicative of a heftier hind-gut fermentation," she said. "Manure that looks like shaving cream is not acceptable. It means things are being fermented in the wrong spot."

Hall stated that one of the options for getting diarrhea other than disease states "is if you have a lot of organic acid in the hind-gut. A lot of folks think this is normal, but it is not."

Fecal particle size and appearance evaluation is qualitative not quantitative according to Hall. "If I go in to a group of cows I try to take samples that reflect the variation of the feeding group," she said. "That might be three to five samples, but it is not indicative of how much feces was produced. It only shows the quality of the feces."

According to Hall when sampling manure it is important to look for particle size and undigested feed. "You need to look for things that look out of place," she said. "Different feeds will provide different appearances in particles, but the particles themselves should still be relatively small if things are working properly."