Q: Do heifers need to be developed to 65 percent of their mature body weight at breeding for good conception rates?
A: Conventional wisdom holds that heifers should reach about 65 percent of mature weight by first breeding. Research has shown, though, that first-calf heifers can achieve acceptable conception rates at 55 percent of mature weight, provided they are gaining weight and condition at breeding. This concept allows lower-cost, forage-based inputs including winter crop residues or dormant grass. Access to green grass in the spring helps heifers gain condition prior to breeding.
University of Nebraska animal scientist Rick Funston, PhD., recently reported on trials comparing heifers developed in two systems, one group spent 193 days in a drylot while another spent 135 days grazing corn stalks through the winter, followed by a 59-day drylot period prior to breeding. The cornstalk heifers weighed an average of 110 pounds less than drylot heifers at breeding but outgained them during pre-breeding backgrounding and on grass through the period between breeding and calving. Final pregnancy rates were 89 percent for cornstalk heifers versus 92 percent for drylot heifers. By calving time, the cornstalk heifers averaged just 38 pounds lighter than the drylot heifers and the cornstalk heifers saved $70 per head or more in development costs.
Source: Dr. Rick Funston, Assoc. Professor, University of Nebraska West Central Research & Extension Center