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Positive energy balance needed for rebreeding

By SANDY JOHNSON

Special to The Hays Daily News

Northwest Kansas is still in the exceptional or extreme drought categories according to the July 2 drought monitor. A lucky few have received rain showers.

While many producers have made downward adjustments to stocking rates this year, they still might find the demand for forage exceeds the actual grass growth. This shortfall can be a problem for cows near the peak of milk production going into the breeding season.

After calving, it generally takes about 50 days for cows in adequate body condition to resume normal estrous cycles. For thin and young cows, the time period can be much longer. Animals must achieve a positive energy balance (energy intake greater than energy expenditure) before they will cycle and rebreed.

Body condition is a useful measure of nutrition; however, metabolic signals will be apparent to the animal before a visible change in body condition. Increased early embryonic loss has been noted when maintenance energy has been reduced by 20 percent, so concerns of insufficient dry matter for grazing cows continues into early pregnancy.

For our current conditions, producers should continue to monitor forage production and rainfall closely, especially during the breeding season. Feeding cows on pasture is rarely a first choice but might be more appealing than thin, open cows at the end of the breeding season, weaning, feeding in a dry lot or selling cows. If supplementation on pasture early in the season is warranted, then producers should supplement energy rather than protein. Ideal energy supplements would be low starch and high fiber feeds like soybean hulls, distillers grains, wheat midds, or moderate quality hay. Compare options on a cost per pound of TDN or energy on a dry basis. Many commercially available self-fed supplements are designed to supplement protein rather than energy. In addition to the expense, the excess protein, especially with limited energy, could be detrimental to reproduction.

Be sure to re-evaluate the mineral supplementation program when providing supplement on pasture to account for mineral content of the energy supplement. For example, the phosphorus provided from a few pounds of distillers grains greatly could reduce or eliminate expensive phosphorus in the mineral supplement.

Forage production and precipitation records from more than 36 years at the Agricultural Research Center in Hays have shown May and June precipitation to be the two-month period with the strongest relationship to the end of season forage production. This compares very well to a correlation of 0.61 for precipitation from October of one year through September of the next with forage production. Thus, we are halfway to a good estimate of this year's end of season forage production.

At the Agricultural Research Center in Hays, 2.16 inches of precipitation fell in May, and the May normal is 3.26 inches. June's total was 2.73 inches and normal rainfall is 2.84 inches. In 2012, actual total precipitation was 14.39 inches, while the normal is around 23inches.

If pastures are short and producers are still in the midst of the breeding season, reducing cow numbers further or providing some form of energy supplement are options. Weaning will decrease energy and water requirements significantly and previously non-cycling cows will resume cycling after weaning. Grass production is not normal this year, so don't expect your normal management approach to cows and grass to work.

Sandy Johnson is a beef specialist at K-State Research and Extension.

sandyj@ksu.edu.