Using corn wisely for replacement heifers
BROOKINGS — Current corn prices have many livestock producers moving to include as much corn as possible in their feed rations.
“Producers’ goals are to maximize returns and right now corn is a cheap and a high quality source of energy,” said Julie Walker, SDSU Extension Associate Professor & Beef Specialist.
Heifer development strategies
When it comes to replacement heifers, cattle producers need to ensure that rations do not have a negative impact on fertility.
Walker explained that the amount of corn included in a ration will be determined by the composition of feeds in the ration.
She said heifer development strategies fall into three categories:
1. Maintaining steady gain (Average Daily Gain or ADG) throughout the development phase;
2. Low ADG early followed by high ADG late in the development phase;
3. High ADG early and low ADG in the latter part of the development phase.
“Remember, within each of these development strategies, heifers need to reach the selected target by the start of the breeding season,” she said.
The amount of corn included in each ration for each of these strategies would differ.
Successful rations provide the nutrients required to support muscle development and growth, but not too much energy resulting in excessive fat deposition. “Research has shown that excessive body condition negatively affects reproductive efficiency,” Walker said.
She added that previous researchers have reported that overfeeding results in weak estrous expression, reduced conception rates, high embryonic mortality, decreased mammary gland development, and decreased milk production.
“Reduced conception rates and increased embryonic mortality will result in easily seen differences in the number of open (non-pregnant) replacement heifers,” she said.
However, impacts on mammary gland development and milk production are more difficult to assess but Walker said they are very important because those changes affect productivity throughout the cow’s entire life.
She referenced a study conducted by researchers at University of Minnesota in 2009, which developed replacement heifers to a body condition score (BCS) of 7 or 5, and then restricted nutrients until all heifers entered anestrous. They then increased the amount of feed until the heifers began cycling.
The result: Heifers that were developed to reach a BCS of 7 resumed cycling at a score of 6 compared to a score of 5.2 for the heifers developed to the lower score.
“In this study, initial BCS had no effect on days to recommencement of estrous cycles but did influence the degree of fatness required to resume estrous cycles,” she said.
With this in mind, Walker said producers should start with feed testing and setting the right performance targets in order to successfully use higher corn inclusion in replacement heifer diets. “The cost for providing either too much or too little energy can impact producers’ bottom-line due to losses in reproductive efficiencies,” she said.
For more information, contact Walker at Julie.firstname.lastname@example.org or 605-688-5458 or contact any SDSU Extension Cow/Calf Field Specialist or Beef Extension Specialist.