Although calving season management is the primary concern for most spring-calving herds, that is only half the battle, explained Warren Rusche, SDSU Extension Cow/Calf Field Specialist.
"The cows still need to get re-bred (and early) if the ranch is going to be a sustainable business long-term," Rusche said.
Nutrition after calving, Rusche said, plays a major role in affecting the success or failure of that process.
He explained that to maintain a 365-day calving interval, re-breeding has to occur within 82 days after calving. A cow needs to recover from calving and start cycling again during that time period, while at the same time providing enough milk for her growing calf.
"All of those demands impose a significantly higher nutrient requirement on cows after calving," Rusche said. "A major obstacle to insure that she will re-breed early is the cow's biological priority for nutrients."
Maintenance needs top the list of nutrient priorities Rusche explained, next, in the case of 2- and 3-year old cows, would be their requirements for growth. Providing milk for her calf is the third priority, and finally, if her nutrient intake is high enough, Rusche said she will increase body reserves, resume cycling and re-breed. "All four priorities need to be satisfied or there will be no calf to sell next year," he said.
Depending on her potential for milk production, a cow could require as much as 40 to 50 percent more energy and protein compared to the two months ahead of calving.
Her needs for nutrients, such as Vitamin A, calcium and phosphorus, are much greater as well. To meet these needs, Rusche said cows will need either better quality forage, additional supplementation or a combination of the two.
"A big part of the reason why the standard recommendation has been to have cows in a body condition score of a 5 is that it is very difficult to add condition to cows after calving," he said. "Supplying more nutrients will increase milk production up to her maximum genetic potential before she adds body condition."
It is important to recognize that in many herds the genetic potential for milk production is much higher now due to selection pressure for more milk; the cost of that increased production, Rusche said, is higher nutritional requirements.
So how do ranchers meet the needs of cows in the most cost-effective manner? The answer, Rusche said depends somewhat on when calving season begins. "If the start of calving season is timed so that peak grass production coincides with when cows are in early lactation, then forage resources might very well be sufficient to meet her needs without relying on a great deal of harvested feedstuffs," he said. "Feed cost savings is one of the greatest advantages for adjusting the start of calving to match grass production in a given environment."
If a ranch's system involves calving earlier in the year, then, Rusche said the nutritional plan needs to take into account the cow's increased nutritional requirements during early lactation. "Ideally the feedstuffs have been tested so that the highest quality forages are saved for after calving and then the proper supplements provided if needed," he said.
Some possible early lactation diets are shown in Table 1.
Keep in mind that nutrient composition of feedstuffs can vary tremendously. Producers need to have their own feeds tested and those values used in formulating diets for the most accurate results.
Source: SDSU Extension