Drought feeding studies with cattle 6. Sorghum silage, with and without urea, as a drought fodder for cattle in late pregnancy and early lactation

Abstract

Three groups, each of 10 pregnant Hereford heifers, were confined in bare yards when their mean stage of gestation was 17 5 days. All groups received a basal ration of sorghum silage ad lib. One group received no supplement, while the other two groups were fed a supplement of 1.5 oz and 2.5 oz of urea per head per day respectively. The experiment terminated after 24 weeks, when the mean stage of lactation of animals suckling calves was 62 days.
Heifers receiving no supplement lost an average of 150 lb body-weight prior to calving. This body-weight loss was significantly higher than those of 79 lb and 42 lb in the two groups receiving 1.5 oz and 2.5 oz of urea per head per day respectively. The average bodyweight loss for those animals suckling calves at the conclusion of the experiment was 385 lb in the group receiving no supplement. The body-weight losses for comparable animals in the groups receiving 1.5 oz and 2.5 oz of urea per head per day were 286 lb and 236 lb respectively.
Urea supplementation increased silage consumption. The mean daily consumption of dry matter per head in each group was: no supplement, 6.3 lb; 1.5 oz urea, 9.0 lb; 2.5 oz urea, 10.2 lb.
The average birth weight of the calves born to heifers in the group rece1vmg no urea was 48.4 lb and was significantly lower than that of 55.6 lb in the calves born to heifers in the group receiving the higher level of urea.
Deaths of 4 calves in the non-supplemented group were attribute to the experimental treatment. No calves died in the group receiving 1.5 oz of urea, while there was one death in the group supplemented with 2.5 oz of urea.
The average body-weight gain in calves from birth to 28 days of age was 9.4 lb in the non-supplemented group and 23.3 lb and 16.4 lb in the groups supplemented with 1.5 oz and 2.5 oz of urea respectively.
Milk production was obtained over a 24-hr period at the conclusion of the experiment by hand-milking the animals after oxytocin injections. The yield was significantly higher in the two groups receiving urea than in the non-supplemented group.
The overall incidence of both dystokla and retained placenta was 15 per cent. There were no significant differences between groups.
At the conclusion of the experiment, there were no significant differences among group means in serum total protein, albumin and globulin; plasma chloride, sodium and potassium; and blood haemoglobin and packed cell volume. After 24 weeks on silage the values in all groups for serum total protein and plasma sodium were significantly lower than initial values.