The effects of pre-calving nutrition on the performance of single and twin pregnant beef cows and their calves
Three experiments were carried out to assess the energy and protein requirments of single and twin-bearing beef cows during the last three months of pregnancy and also to observe the effects of pregnancy nutrition on the subsequent lactational performance of cows and calves. A wide range of energy level was applied to single and twin-bearing cows. As assessed from body weight change, calf birthweight, milk yield, calf growth rate and blood parameters, it was found that there was no benefit in giving high levels of dietary energy to cows during pregnancy. It was concluded that feeding 50 and 70 MJ ME/day to single and twin-bearing cows respectively together with a high proportion of UDP may be acceptable levels during the latter part of gestation, provided that the cows are in good body condition at the start of the last trimester of pregnancy and they are given adequate nutrition during early lactation. Another three experiments were conducted with pregnant ewes, wethers, pregnant heifers and steers to measure the digestibility and to determine the metabolisable energy value of two mixed diets which differed in rumen degradability of protein. Such diets were used in experiments with pregnant cows. A comparison was made between the digestive capacity in different species and sex of animals. Digestibility co-efficients of two diets, two sexes and two species did not differ significantly. Therefore, it was concluded that metabolisable energy value determined for mixed diets using sheep can be used for cattle. ME value of mixed diets was less than that calculated in these experiments but the extent of the decrease may be acceptable under farm conditions.