– Dr. Katie VanValin- Assistant Extension Professor- University of Kentucky.
Perhaps it was the full season worth of winter weather we got in one-week last month, or the above average temperatures that followed, but either way we are rounding the bend and spring will be here before we know it. One of the things I love most about spring is that along with the warmer temperatures and longer days, inevitably comes greener pastures. However, the growth we see out in our pastures during the early spring can often be deceiving from a nutrient standpoint.
The problem that we can run into is that there simply is not enough forage available, and the forage that is high in moisture. When we turn cows out to early, they can exert more energy searching for the next mouthful then they are consuming, since most of every mouthful is water. This is especially critical for spring-calving cows. At this time, cows have either or will be transitioning from late gestation to lactation which represents the time when a cow’s maintenance nutrient requirements are at their highest throughout the production cycle. This is not the time to let cows slip into an energy deficit and lose condition.
If cows lose condition during early lactation when their maintenance nutrient requirements are high, it is often difficult to recover that condition prior to breeding. It is a much better plan to ensure cows are in good body condition prior to calving and maintain adequate condition through breeding. Research has shown the reproductive performance is decreased when cows reach a BCS of 4, so it is critical to the performance and efficiency of the cow herd that cows maintain a BCS of 5-6.
For example, a cow in early lactation with a BCS of 4 consuming fresh cool-season forages would be able to consume enough forage to meet her maintenance requirements. If we tried to improve the BCS of this cow by ¾ of a BCS (approximately 75 lbs) now that fresh forage is only providing about 70% of her energy requirement. So, in this scenario even if available forage was not the limiting factor, supplementation would still be needed to improve body condition. It can also be helpful to manage older or thin cows separately from the rest of the herd, allowing them to receive the extra nutrition they require without overfeeding the rest of the herd.
Although it is tempting to turn cows out to grass early, remember that doing so may limit cow-performance. This can also cause undue stress on forages, ultimately hurting our stands, and creating opportunity for opportunistic weeds to encroach. Evaluate the forages in your pasture and let grass growth dictate when cows are turned out as opposed to a date on the calendar.
The bottom line here is don’t let spring fever set in early by turning cows out onto fresh grass that may not meet all the nutritional demands of the herd. Continue to evaluate BCS of the herd and allow this to guide nutrition and management decisions as mother nature transitions from winter to spring, and cows transition from gestation to lactation.