At this time of year, a spring calving cow experiences two periods of increased nutritional need which are significant and must be accommodated or her performance for the rest of the year can be negatively affected. One of these periods, of course, is at calving.
The accompanying chart shows that in the first month of lactation, her protein and energy needs have increased by 0.7# and 2.3# respectively, compared to her last month of pregnancy. By the second month, as her level of milk production nears maximum, her protein and energy needs have increased 56% and 27% respectively.
She is not only producing milk but also trying to prepare her body to breed again very soon. Without an immediate, adequate increase in nutrition at calving, a dramatic loss of body condition is common as she uses body stores to meet these new needs. The most common effect of inadequate nutrition after calving is low conception rate during the breeding season.
Possibly the most often overlooked nutritional need for a spring-calving cow, however, comes during the last 50 to 60 days of pregnancy. In the first 7 months or so of gestation, building a calf does not require a lot of nutrients. In the last two months, however, the fetus makes 75% of its total growth. Additional protein, energy, and minerals are needed to build the calf and maintain the cow's increasing weight.
Look at the chart again. From month 6 to month 9, this cow's daily protein requirement increases by one-half pound, about 40%. Her energy needs go up 2#, or 20%. These increases aren't as significant as those at calving, but failure to attend to them can negatively effect performance just as much.
The same ration that maintains a cow through most of her pregnancy will result in weight loss during the last two months. The fact is that if a cow is dropping condition in late pregnancy, whether rapidly or imperceptibly, she will not cycle as quickly after calving.
These two periods are critical to prevent delayed estrous after calving and lower conception rates during the breeding season.