New research shows that cows fed a fat supplement during the last three weeks of the dry period showed enhanced reproductive performance during the next lactation.

According to a Cornell University study, cows fed the supplemental fat spent 31 fewer days open and were 1.9 times more likely to become pregnant than cows that did not receive supplementation. It is the first study to show supplemental fat in a transition-cow diet boosts reproductive performance.

During the study, the supplemented cows were fed 0.5 pounds of a prilled fatty-acid supplement for 21 days prior to calving. The cows did not receive the supplemental fat after calving, says Ron Butler, one of the study’s authors.

The study’s results show 86 percent of the supplemented cows became pregnant during the following lactation compared to only 58 percent of the unsupplemented cows. The supplemented cows also averaged 110 days open compared to 141 days open for the unsupplemented cows.

Researchers don’t completely know how supplemental fat during the transition period improves reproduction during the next lactation. However, Butler suspects the fat may target the ovary, or even the egg itself, and that it may exhibit some sort of carryover effect during lactation.

Although the results are exciting, this is only the first study to show supplemental fat fed three weeks prior to calving improves reproduction in dairy cattle. However, more work is underway at Cornell to try and duplicate the positive results seen during this study, and to find out exactly which reproductive tissues the supplemental fat targets.

The results were reported at the joint dairy and animal science meetings held earlier this summer.