Calving is a critical period for beef cattle producers, and proper nutrition is crucial to a successful outcome for the cow and calf, say Grant Dewell and Terry Engelken, Iowa State University veterinarians. Body Condition Scoring (BCS) can be used to assess the nutritional program of the beef herd.
Historically, there was some thought that protein and energy supplementation was responsible for dystocia problems. Actually many studies have shown that cattle fed low energy diets prior to calving have a higher percentage of dystocia than medium or high energy diets unless cows are overly conditioned with fat deposits in the birth canal. Calves from cows fed adequate energy and protein did have increased birth weights but decreased dystocia rates. Therefore it is important to remember that you cannot starve calving difficulty out of cows, they say.
One of the most important factors is the effect of dam nutrition on calves, according to Dewell and Engelken. "Proper energy and protein levels are vital for calf vigor after calving. Calves from energy or protein restricted dams during gestation have decreased calf vigor and ability to generate body heat. Weak calves will be less likely to intake adequate amounts of colostrum and are more prone to increased morbidity and mortality."
Cows and heifers that calve in a thin body condition will have longer return to estrus period and decreased conception rates compared to females that calve in good body condition. They point out that new research at the University of Nebraska has even shown that heifer calves born to cows receiving adequate protein nutrition have increased reproductive performance compared to heifer calves whose dams did not receive adequate protein nutrition.
Cows should calve at a BCS of 5 (heifers at BCS 6) at calving. Up to 80% of fetal growth occurs in the last 50 days of gestation. Females during this period of gestation need approximately 11 Mcal of energy and 1.7 lbs of crude protein per day.