Provision of urea to cattle in a salt/urea/molasses block

Abstract

Six groups of four cattle were selected from 12 pairs of mixed identical and fraternal twins. There were two major age groups, one of mean 25.5 months and the other of mean 14.2 months at the commencement of the experiment. Four animals of each age were group-fed in bare yards on the following rations:-hay ad lib.; hay ad lib. + molasses; and hay ad lib. with free access to a salt/urea/molasses block.
The hay was made from native pasture and had a crude protein content of 3.5 per cent. on an air-dry basis. The salt/urea/molasses block contained 40 per cent. urea and 10 per cent. molasses.
From the 97th to the 103rd day all the younger animals receiving hay and bay treated with molasses were withdrawn from their treatments because of the inability of some to rise and the emaciated condition of the remainder. All the older animals remained in the experiment for the planned duration of 161 days and the younger animals receiving the block were continued for 217 days.
No significant response in either hay intake or body-weight was obtained by treating the hay with molasses.
Provision of the block significantly reduced body-weight loss in both age groups. Over the 161-day period body-weight loss in the older group receiving block was 60 lb less than that in the same age group receiving no supplement. The respective advantage in the younger animals was of the same order but was not significant.
Mean respective block intakes in the older and the younger animals were 6.9 oz and 4.2 oz per head daily over the 0-161-day period. When chromic oxide was added to the block, the faecal chromic oxide percentage in the younger group ranged from 82 to 109 per cent. of the group mean and in the older group from 67 to 113 per cent. of the group mean.
Net air-dry bay intakes were 29 and 45 per cent. greater in the groups receiving block than in the comparable groups with no supplement.
The behaviour of the animals was observed over several. 6-7-hr periods during the daylight hours. Calculations made from this data estimated a maximum urea intake per 'Visit to the block of 1.55 oz.