The beef cow is the heart and economic engine of the beef industry. Millions of acres of grass would go to waste if these unique eating machines didn’t turn cellulose into protein while successfully generating a calf at foot.
While the foundation of profitable beef production, cows are too often taken for granted, like the dedicated effort needed to better engineer our industry’s most important link in the production chain.
In the words of Dr. Rick Funston, reproductive physiologist University of Nebraska’s West Central Research and Extension Centre, management of reproduction remains the single most important challenge.
Few can disengage reproductive efficiency with calves born every year, longevity of brood cows in the breeding herd, and the maximum kilograms of weaned calf going into top markets every fall. When all is said and done, reproduction efficiency has a significant role in determining the quality of beef on store shelves — factors that go beyond genetics.
Despite the importance of reproduction and breeding programs, 55 per cent of beef herds still have no defined breeding season. Without a sharply defined breeding season, uniformity of the calf crop naturally suffers. The lack of a defined breeding season also complicates nutritional management of the herd and identification of reproductive problems should they arise.
Heifer development lies at the heart of creating better cows. In his address to the Western Canadian Association of Bovine Practitioners in January, Funston talked about programmed heifer development as a means of identifying the adaptability of females early. The adaptability of heifers has allowed herds he has been involved with to shorten breeding seasons, breed heifers at lighter weights and reduce the mature weight of breeding females. To do this successfully, heifers must continue to grow through to calving.
Estrous synchronization is another of the tools industry should adapt. Synchronization programs (following bull turn-in) used in well-managed herds have achieved 85 per cent pregnancy rates over a 35-day breeding season. A 45-day breeding season potentially increases weaning age by 13 days (7.6 per cent), weaning weight by 9.6 per cent, and an extra $35-$40 per calf at market. Calving times also have a measureable effect on feedlot performance. Increased carcass values of $90 or more (based on ADG, carcass size and yield grade) are commonly associated with calves born during the first 21 days of calving season compared to cohorts born later.
As well, calving times contribute to extended improvement in performance of heifer progeny. Heifers retained as herd replacements from groups born the first 21 days of calving season showed a 12 per cent higher pregnancy rate and 15 per cent more calves born during the first 21 days of their first calving season. Overall lifetime production of the breeding herd can be enhanced. A cow that consistently calves in the first 21 days of her eight- or nine-year stay in a herd will produce the weaning weight equivalent of an additional 1-1/2 to two calves in her lifetime compared to a cow that starts late and stays late. Sixty-one per cent of cows in high-production herds calve in the first 21 days of the calving period with 85 and 94 per cent of calves born by day 42 and 63 days respectively.
Sire selection accounts for more than 85 per cent of the improvement in herd performance. Heterosis (cross-breeding), alone, enhances cow longevity, pounds of calf weaned and net profit gained per cow of approximately $70 per cow exposed.
Producers should consider implant programs, a tool representing the difference between profit and loss in many herds.
Optimal nutrition through the calendar year governs the success of heifer development and the benefits that get carried forward into their years as brood cows. Body condition scores (BCS) are correlated with reproductive events like postpartum interval, services per conception, calving interval, milk production, weaning weight, and calf survival. The most important factor influencing pregnancy rate and resumption of recycling in beef cattle is body energy reserves during late pregnancy.
The science behind fetal programming and the influence it has on heifer development is just starting to be understood. We know performance transcends simple genetics and that stimuli experienced during fetal development impacts postnatal growth and physiology. Management of maternal diet during early gestation is linked to placental programming and adequate nutrient transfer to the fetus. Maternal nutrition later in gestation has been reported to influence fetal organ development, muscle development, postnatal calf performance carcass characteristics and reproduction. Proper nutrient intake during critical points of gestation appears to be linked to long-term heifer performance and health, especially fertility. While more study is needed to better understand how far reaching the effects of fetal programming might be, Funston believes producers need to rethink nutrition management strategies beyond the cow. In one study, 77 per cent of heifers born from cows receiving protein supplementation during gestation subsequently calved during the first 21 days of their first calving season compared to 49 per cent of heifers from cows not receiving protein supplementation. The overall pregnancy rate was 93 per cent for daughters of supplemented dams, compared to 80 per cent for heifers whose mothers received no supplement.
The take-home messages of Funston’s presentation to bovine practitioners included:
- Focus on high percentage of early pregnancies
- Begin the journey of building a better cow with heifer development
- Consider synchronization
- Optimal nutrition and BCS are critical
- Sound herd health programs are integral to success
- Match genetics to the environment
- Heterosis is too important to ignore
— Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).