Prevent the challenging heifer cycle (part 1)

By Dr. Noah Litherland, Vita Plus dairy technical services
At some point, every dairy is likely to experience a challenging heifer cycle.  A challenging heifer cycle occurs when a portion of the heifer development phase does not go as planned and results in heifers that have lower-than-expected rates of growth, lung consolidation, or increased rate of non-completion of first lactation.  The net result is often a reduced return on investment from the heifer program.

Calves born during heat stress
When dry cows are challenged with periods of hot weather without heat abatement strategies in place (such as shade and fans), they tend to have shorter gestation lengths, resulting in calves with decreased birth bodyweight, decreased ability to absorb IgG from colostrum, and increased morbidity risk.

Calves reared in heat stress typically have slower rates of gain, lower starter grain intake, and increase difficulty in transitioning to grower.  Research at the University of Florida suggested in utero effect of heat stress on heifer calves.  Compared with heifers from non-heat-stressed dams, heifers born from heat-stressed dams had altered gene expression that decreased both milk yield and reproductive efficiency that can impact subsequent generations.  The changes in gene expression appear to be toward downregulation of performance due to experience of heat stress.  Heifers born in heat stress tend to calve in heat stress as two-year-olds, perpetuating the cycle and thus impacting whole cow families.

Mitigation strategies:

• Provide dry cows with sufficient cooling to avoid heat stress.
• Adjust the breeding program to minimize number of calvings during peak heat stress times.
• Consider both winter and summer ventilation systems for calf barns.
• Provide shade over hutches if rearing calves outdoors.

Introduction of novel pathogen or pathogen strain
Pathogens impacting heifers are not going away.  Novel pathogens or novel strains of pathogens can have a negative impact on nursery calves, decreasing rate of growth and increasing risk of lung consolidation.

Mitigation strategies:

• Implement biosecurity procedures on your farm to limit the risk of introducing new pathogens to your herd.
• Any visitors to your farm should – at minimum – sanitize their boots.  Virkon™ S is a good option as it is antiviral, antibacterial, antifungal and antiprotozoal.  Consider adding step-through boot washing stations at the entrances of the calf facility so both workers and visitors can routinely sanitize boots.
• Nuisance birds and flies can also carry pathogens to your farm, so proactively implement control strategies to reduce risk.
• Review your current vaccination plan with your attending veterinarian.

Challenging heifer cycles are real on every farm.  In part two of this series, we’ll explore more factors that can trigger a challenging heifer cycle.  It takes a team approach and a focus on the future to avoid challenging heifer cycles and mitigate risk and damage once a challenging heifer cycle has started.