by Sandy Johnson, extension beef specialist, Colby
Winter has been long and difficult. Cold and wet weather increased energy demands. Cows could be thinner than normal after calving and winter conditions could have negatively influenced bull fertility as well. Hopefully, weather will support good forage growth this spring but that remains an unknown for now. Monitoring breeding activity and use of timely pregnancy detection are risk management tools that should be used routinely but are especially important given the recent weather challenges.
How soon cows resume normal estrus cycles this spring will depend on their body condition at calving, any calving difficulty, age and their access to enough energy in their diet to exceed peak lactation requirements, resulting in a positive energy balance. Green grass can do wonders for thin cows but there has to be enough growth (quantity) to get the benefit. Young and very thin cows still may have extended postpartum intervals to rebreeding.
If all cows in a group are cycling, there should be roughly 5% in heat per day. While cows are still shedding winter coats, noting the number of rubbed or hairless tail heads can give you a good indication of how many have resumed cycling. Heat detection aids (i.e. self-adhesive patches) used for AI programs could be considered for more accurate assessment. Non-cycling cows that are close to resuming normal cycles can be induced to cycle with a CIDR insert (contains progesterone) or 48-hour calf removal. These tools can both be used with natural service. In one study, CIDR-treated cows conceived earlier than control cows, but overall pregnancy rates were not increased. The breeding season began relatively early (fewer days since calving) early in this study by design, and cows were in good body condition. Regardless of method, these efforts require time and handling. As you evaluate these options, consider that getting one cow to conceive one week earlier is worth about $21 per week in the value of her calf next year (7 days x 2 lbs/day x $1.50/cwt). It may be possible to target this type of approach to subgroups of cows with greatest need.
Bulls should be in a body condition of five at the start of the breeding season and have had a breeding soundness exam each year prior to turnout. This year in particular it will important to ensure there was no frostbite damage to the scrotum from this year’s wind chills. Once the breeding season begins, monitor breeding activity to ensure bulls remain healthy and that bull’s work is decreasing during the season. Spend some time observing heat once or twice a week, early in the morning or later in the evening to confirm. Remember that an injured dominant bull can prevent fertile bulls from mating.
If cows are thin and the risk of poor reproductive response is high, leaving bulls out for a longer breeding season may increase pregnancy rate. Combine this with pregnancy diagnosis less than 120 days after bull turnout so pregnancies can be accurately staged and this information can be used to do further planning. The earlier this information is available, the more time for study of the best economic approach if pregnancy rates are abnormally low or shifted to late in the season. If you leave bulls out until the early pregnancy check, that information can be used to decide if bull exposure should continue or not. Granted, some cows will need to be rechecked because short-term pregnancies can’t be differentiated from opens. Determination of stage of pregnancy is much more accurate on pregnancies of 100 to 120 days or less. Avoid letting a long breeding period become a long calving period. An extended calving period results in greater expense of over and under feeding cows unless cows can be sorted and fed by stage of gestation. Strive to market those cows that do not conceive in 60 to 90 days. A long calving period with a number of late calving cows depresses weaning weight and often lowers pregnancy rate over time, robbing profit from the enterprise.
The weather presented a number of challenges this past winter that could easily have carry over effects to the breeding season. Individual circumstances will affect the best management options to cope with less than ideal breeding conditions. Contact me to discuss specific options to fit your operation and goals.