Maternal energy status of beef cattle during single and twin pregnancy.

A study was undertaken to determine the metabolizable energy (ME) intake and ME requirement for beef heifers and cows during twin pregnancy. Weekly feed consumption and body weights were recorded during the last trimester of twin pregnancy for 19 Hereford cows and 16 Hereford heifers. The same data were recorded for six Hereford cows and eight Hereford heifers that calved singles. ME intake per unit of metabolic body size was higher for heifers than cows (P less than .05), but was not affected by whether the dam was pregnant with a single or with twins. In general, ME intake decreased during the last trimester of pregnancy. During this time, heifers and cows with singles gained weight (pregnant weight minus weight of the conceptus), while dams with twins lost weight (P less than .01). The greatest weight loss for dams with twins was observed late in pregnancy. The ME requirement of pregnancy was greater for dams with twins than singles (P less than 0.01), and the difference in maintenance ME requirement approached significance (P less than .10). The high ME requirement for the twin pregnancy and the weight loss experienced by dams during the last trimester may have implications for management decisions pertaining to the prevention of complications that often occur with twin pregnancy in cattle.