A cow herd's greatest nutrient requirements occur immediately after calving and continue through peak milk production.
During this period, a cow uses the majority of the nutrients it consumes to produce milk to sustain a hungry, growing calf. After that, the cow uses the nutrients to regain body condition, and as a last priority, to repair its reproductive system.
"Cows in poor body condition at the time of calving likely will have difficulty rebreeding," cautions Carl Dahlen, North Dakota State University Extension Service beef cattle specialist. "Cows often lose some body condition in the months after calving, and the goal of a solid nutrition program should be to minimize this loss in condition."
Feeding lactating cows to their increased nutrient requirements is the best way to minimize loss of body condition. Every herd has cattle at a variety of ages and body conditions, and every herd has its limitations in the way it can group cows before and after calving.
Minimizing the competition in the feeding area is one way to help ensure cows have access to feed. Thin cows, cows that had difficult births and first-calf heifers may be pushed away from feed by older cows or cows in better condition.
If facilities are available to feed different groups of cows, heifers and thin cows should be fed separately from mature cows, Dahlen advises.
The importance of these increasing nutrient needs is even greater in heifers calving for the first time. In addition to the increased demands of lactation, this class of cattle has more difficulty calving and still is growing. These factors add up to the heifers needing a greater amount of time to start having estrous cycles after calving.
Delayed estrous cycles after calving result in delayed breeding, This is the basis for a common recommendation to calve heifers two weeks prior to other cows in the herd. Being the first to calve means the heifers get more attention, producers can dedicate more time to heifers having problems, and the heifers have more time for uterine repair and resumption of estrous cycles.
Reproductive performance and performance of calves is reduced in thin cows.
However, gaining body condition in thin cows after calving is expensive in terms of feed energy and finances and should be approached with caution, Dahlen says.
Improving body condition is much easier before calving and typically cheaper while the cows are on pasture.
While difficult to accomplish, thin cows may gain body condition after calving.