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DBweekly 11 When feeding pre-calving energy levels LESS CAN BE MORE Research by University of Illinois scientists is challenging accepted wisdom that a cow needs a higher energy intake before calving. Students in animal sciences professor James Drackley’s group compared cows fed before calving with diets containing the recommended energy levels to cows fed reduced energy diets. U of I FALL DAIRY CLASSES The University of Illinois will offer three dairy classes in the fall semester. • A new one-credit dairy class titled “Ration Balancing and Building” will use the Spartan III dairy model. The five-week class begins in September. To enroll, click here. • A one-day, hands-on training class at Hoard’s farm, near Fort Atkinson, Wis., will be held on Oct. 3 (during World Dairy Expo week). Class size is limited to 20. For more details, click here. • Dr. Dick Wallace will offer his 10-week, two-credit “Advanced Dairy Reproduction” class, September through November. To enroll, click here. They found cows fed the reduced energy diets performed better after calving. Animal sciences researcher Phil Cardoso, intrigued by those results, wondered if diet might also be linked to reproductive performance. Using data from seven experiments completed at the U of I from 1993 to 2010, he constructed a database of 408 cows, containing data on prepartum diet and physiological status. He also looked at days to next pregnancy (DTP) after calving. On average, cows fed the controlled energy (CE) diets (80% of the recommended amount) became pregnant about 10 days sooner than cows fed high-energy (HE) diets, an average of 157 vs. 167 days. Cows on the CE also lost less in body condition score (BCS) and had a lower disease incidence because they were eating more. Cardoso said that the shorter time to conception for cows fed the CE diet is due to the fact that they eat more after calving than the cows fed the HE diet. “Just after calving, the cows have a negative energy balance (NEB),” he explained, because they cannot consume enough energy to compensate for milk production. NEB, measured by looking at metabolites in the blood, causes them to lose weight, lowering their BCS. High levels of the metabolites just before calving or one to two weeks after calving are associated with metabolic disorders and certain diseases, which cause them to eat less. These in turn affect reproductive performance. Both groups of cows showed reduced energy consumption around calving, but the drop was about four times higher in the HE cows. Cows fed the CE diet were able to start eating right after calving. The researchers also noticed that cows fed the CE diet showed less prepartum vs. postpartum variation in how much they ate. By contrast, the cows fed the high energy diet were eating more than they needed before calving. In a follow-up study that has not yet been published, the researchers tried strategies to make the cows eat less. One was to give them just 80% of what they needed; the other was to increase fiber so the diet would be lower in energy and the cows could eat more. Results for the two strategies were similar. There are indications a CE diet has other benefits. It may keep food in the rumen longer, which is beneficial to the cow if she is stressed. Long intervals between calvings also costs money. Research has shown that every day after 90 days in milk that the cow does not get pregnant represents a cost of $2 to $3. In short, Cardoso advised, just give the cow what she needs and she will perform better metabolically and reproductively. “Prepartum Dietary Energy and Reproduction” by F.C. Cardoso, S.J. LeBlanc, M.R. Murphy, and J.K. Drackley, has recently been published in Journal of Dairy Science. This article was originally written by Susan Jongeneel.
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