Grassland Quality Can Impact Rebreeding Success in Beef Cattle

Cattle producers often eagerly anticipate this time of year with pasture turnout and a new breeding season in the near future; however, this time of year also presents challenges as producers plan grazing and reproductive management strategies.

A successful breeding season starts long before bulls get turned out, and a large part of that success relies on providing proper nutrition to beef females. The expectations are high for a postpartum cow, says Lacey Quail, North Dakota State University Extension livestock management specialist at the North Central Research Extension Center.

A cow must first start cycling again after calving, then become pregnant within 80 to 85 days after calving to maintain a yearly calving interval, all while lactating to raise the calf she just birthed.

The first 90 days after calving are the most nutritionally demanding, says Quail. Because lactation takes priority over reproducing for next year, cows will devote nutrients to milk production first and require additional nutrients to successfully rebreed. This can be difficult considering peak milk production overlaps with when cows need to be recycling to prepare for the following breeding season. This places a huge nutrient demand on beef females. More specifically, a beef cow that calved two months ago (peak lactation) may require 1.5 times the protein and energy that she required in late gestion — just three months before calving. Therefore, it is not uncommon to see cows losing body condition during this time if their diet is not meeting their protein and energy requirements.

Cattle that lose body condition after calving and enter the breeding season in thin condition have lower conception rates. More specifically, research has reported that cattle entering the breeding season with three to five ribs and a slight spinal outline visible (body condition score 4) had a 58% pregnancy rate, even after an extended breeding season.