I want to spend our time today talking about replacement heifer development, and the work UNL researchers have been doing to develop low cost heifer development systems. If you are interested in lowering your heifer development costs I suggest you go to beef.unl.edu and type low cost heifer development into the search box. You will find a growing body of information that suggests we can spend less on heifer development, without compromising ranch profitability.
I’ve talked before about the Profit Tips that are available at beef.unl.edu written by UNL Specialists on various topics related to improving ranch profitability. Dr. Funston wrote a Profit Tip on Low Cost Heifer Development Strategies that I want to highlight.
There was a lot of research behind the traditional guidelines of developing heifers to 60 to 65% of mature body weight at time of breeding. If you look back at of those old studies and compare them with new research, it appears that the associations among Body Weight, puberty and heifer pregnancy rate appears to be changing over time. In general, research reports published through the late 80s have shown much greater negative effects of limited post-weaning growth, where as more recent studies indicate less of a negative impact.
It appears that ranchers have made significant improvement in age of puberty over the last 30 years. In fact we often have more trouble with heifers reaching puberty before weaning, than we do with them not reaching puberty before breeding.
Another factor that seems to have changed is the association between timing of puberty and subsequent pregnancy rate. Early research indicated that the fertility of a heifers’ first estrous cycle was lower than subsequent cycles. However, several studies have not shown strong associations between nutritionally related changes in age of puberty and final pregnancy rates.
These changes in reproductive capacity, combined with the continued increase in cost of harvested feedstuffs have created the need for alternative development systems which allow heifers the opportunity to conceive early as yearlings at reduced cost.
Feeding replacement heifers to a traditional target weight increases development costs relative to more extensive heifer development systems. UNL researchers found that heifers developed to only 53% of mature weight could achieve similar initial pregnancy rates and retention compared to heifers developed to 58% of mature weight. Further research found pre-breeding weights as low as 51% of mature weight was more cost effective than development to 57% of mature weight when lighter heifers were allowed 60 d to become pregnant. Extending the breeding season by 15 d for lighter heifers resulted in first-calf conception rates being similar between systems. A better solution would be to keep more heifers and sell the ones that don’t get pregnant. Those open heifers can be profitable if developed cost effectively.
Post-weaning management of heifers to achieve traditional target weights, particularly by feeding high-energy diets, is not supported by available research. Heifers developed on forage, however, do generally require some protein supplementation in the range of 1/3 to ½ a pound a day of supplemental protein. Dr. Funston also emphasizes that heifers should be allowed to exhibit compensatory growth before the breeding season.
