Factors affecting the nutritive value of fat for calves. II.—the system of feeding, and the mode of incorporation into meal mixtures

The effects of feeding meal mixtures suspended in water, as compared with dry feeding, and the merits of different methods of incorporation of fat into liquid‐fed meal mixtures were investigated in digestibility trials and nitrogen retention studies with Ayrshire bull calves. When calves were changed from filled‐milk diets to meal/hay diets, a markedly better utilisation of dietary protein was found if the meal part of the diet was fed as a suspension in water, for meal mixtures of both low and high fat content, than with the same meal mixtures fed dry. Evidence is presented which indicates that liquid feeding enabled the concentrate part of the diet to by‐pass the rumen and enter directly into the abomasum as is the case with milk‐fed calves. It is suggested that this led to a better utilisation of dietary energy which in turn permitted a more efficient utilisation of protein. With liquid feeding, the mean digestibility of the ether‐extractable material in a meal mixture containing 20% of red palm oil, added in the form of an homogenised milk powder, was 77.9 ± 3.9% compared with 72.7 ± 2.1% for that in a similar diet containing 19.3% of the palm oil and 0.7% of lecithin simply blended with the other components of the diet. The higher digestibility of the homogenised fat was accompanied by a slightly greater retention of nitrogen. The red palm oil of the homogenised milk powder had a mean digestibility of 89.5% when fed to the same calves earlier as part of an all‐milk diet. Further results suggest that the lower apparent digestibility of homogenised fat in liquid‐fed meal mixtures than in all‐milk diets is due partly to the higher daily intakes of calcium and magnesium on meal diets.