During the mid 1990s a potentially serious, chronic syndrome was reported in well-managed beef and
dairy herds from unrelated parts of South Africa. Farmers reported that it manifested as various combinations
of decreased production, decreased weaning masses, apparent immune breakdown in previously
immunocompetent animals, increased reproductive disorders, various mineral imbalances in
non-deficient areas and goitre, noticeable as enlarged thyroid glands. The farmers associated this
syndrome with certain batches of sugar cane molasses and molasses-based products. The syndrome
was reminiscent of an “endocrine disruptive syndrome”.
The objective of this study was to evaluate the suspected endocrine disruptive effect of molasses included
in cattle feed. Using existing in vitro assays, four batches of molasses syrup were screened for
possible inclusion in a calf feeding trial. Two batches were selected for the trial. Thirty-two, 4- to
6-week-old, weaned Holstein bull calves were included in the single phase, three treatment, parallel
design experiment. In two of the groups of calves, two different batches of molasses were included in
their rations respectively. The control group was fed a ration to which no molasses was added, but
which was balanced for energy and mineral content. The mass gain of the calves was recorded over
the 6-month study period. The calves were clinically examined every week and clinical pathology
parameters, immune responses and endocrine effects were regularly evaluated.
Even though endocrine disrupting effects were detected with the in vitro screening assays, these
could not be reproduced in the calves in the experiment. The two batches of molasses utilized in the
calf feeding trial did not induce major differences in any of the parameters measured, with the exception
of a lower mass gain in one of the molasses-fed groups (Group 1), which tended towards significance.
The results of the study indicate that the two batches of molasses had no endocrine disruptive or immunosuppressive
effects in calves.