More than 425 nutritionists and dairy industry professionals gathered in Dubuque, Iowa, June 13 and 14 for the Four-State Dairy Nutrition and Management Conference. The program planning committee consisted of dairy extension faculty from Iowa, Indiana, Minnesota and Wisconsin, and the intention of the conference was to provide timely research information for dairy industry professionals.
Highlights of knowledge presented in the general sessions of the conference included:
Randy Shaver of the University of Wisconsin shared recent information about starch for dairy cows. Increased corn prices have created more interest in feeding reduced-starch diets.
Studies are showing that it is not beneficial for feed efficiency or IOFC (income over feed cost) to formulate reduced-starch diets by partially replacing corn grain with neutral detergent fiber from high-fiber byproducts or corn silage for high- producing cows in mid-lactation.
He said a larger range of high-moisture corn fermentation in the silo will increase starch digestibility. It is believed that this is due to the degradation of the starch-protein matrix as reflected by increased ammonia concentrations.
Shaver also stated that recent studies show adding Rumensin to a reduced-starch diet for dairy cows (adding 18 g Rumensin per ton TMR) showed no significant impact in dry matter intake, a “highly significant” impact on milk yield, no significant impact on milk fat and a negative impact on protein.
Starch’s total tract digestibility in dairy cows ranges between 70 and 100 percent, with particle size (fine ground vs. coarse rolled), grain processing (steam flaked vs. dry rolled), storage method (dry vs. high-moisture corn), moisture content and duration of silo fermentation for high-moisture corn and the type of corn endosperm.
Hypocalcemia is costing the average 1,000-head dairy operation upwards of $24,000 annually, and producers may not even realize they have a problem, said Gary Oetzel from the University of Wisconsin during his update on hypocalcemia on dairy farms.
“This is not just about the ration,” Oetzel said. “These are sick cows. It’s amazing how much milk is lost.” Many of the cows suffering from hypocalcemia are subclinical (without signs). A recent large multi-site study shows that hypocalcemia around calving time is strongly associated with reduced milk yield and increased risk for DAs.
He said nutritional management is key in preventing the ailment. He stated calcium chloride has the greatest ability to support blood calcium levels. Oetzel recommends 50 grams of elemental calcium in a small oral dose, and he discourages the uses of subcutaneous calcium treatments, as it can cause tissue necrosis, and liquid/gel calcium, as it is dangerous if aspirated.
Cows should be given oral calcium supplements at calving and a second dose the next day. Magnesium also has an important role, as it affects release of the hormone PTH and hydroxylation of vitamin D to its more active forms. He recommends total magnesium intake in pre-fresh and fresh cows of 40 to 50 grams a day.
Oetzel notes that the pH of the diet is more important than calcium intake. Alkaline diets tend to cause milk fever, while acidic diets tend to prevent milk fever. Acidification can affect dry matter intake and should only be implemented in herds that can withstand a reduction of DMI of up to 11 percent.
“You can’t feed the same diet to all cows and expect the same response,” said Mike Allen of Michigan State University during his presentation, “Adjusting Ration Starch Concentration and Digestibility through Lactation.” He strongly encouraged producers to group cows by physiological state (fresh, early to mid-lactation and maintenance phase) to correctly formulate diets for starch based on the cow’s needs.
This will better allow the ration to optimize health and production. As they progress though lactation, the rumen’s ability to ferment starch affects feed intake and energy partitioning differently. During the first two weeks after freshening, highly fermentable starch sources should be limited to further avoid depressing feed intake and decrease the risk of ruminal acidosis and DAs.
During early to mid-lactation, high-producing cows thrive on high-starch diets with highly fermentable starch sources. Starch concentration and fermentability should decrease as lactation progresses to maintain milk average and prevent overfeeding.
Allen also briefly spoke about how the liver is “hardwired” to the feeding centers in the brain via the vagus nerve. “Feeding behaviors are affected by the firing rate of the nerve,” he said. Firing rates are affected by the rate of oxidation of fuels (foods) in the body.
Higher oxidation results in decreased firing of the nerve and the decreased firing causes the animal to stop eating because she feels satisfied. Fuels oxidized in the liver in dairy cows include fatty acids, propionate, lactate and amino acids.
Tom Overton of Cornell University presented information on “Managing Energy Metabolism in Transition Dairy Cows.” Overton said new opportunities for enhancing transitional cows’ health and performance are coming from the increased understanding of how metabolic regulation serves as a foundation for the changes that occur in the cow’s energy metabolism during the transition period.
Overton said the information now available tentatively suggests that feeding higher-energy diets promotes higher energy intake and milk yield along with better metabolic status during the postpartum period. PD
Boylen is a freelance writer based in Calmar, Iowa.
