In September 2005 I carried out a mortality investigation involving 3 of 17 unweaned calves dying in the space of a week. The calves were feeding on mixed age Hereford cows which were homebred and these cows had been fed whole white cottonseed for some time with no additional calcium in the ration. The cows and calves were grazing on a 70 acre paddock, near Bundarra, and the paddock had short green feed only with a small amount of clover.
The owners reported that the calves appeared sleepy, depressed and there was a failure to suck and death soon followed after a short period of illness.
The well grown calf, selected for a PM,was in good body condition and there was a significant quantity of straw coloured pleural, pericardial and peritoneal fluid along with an enlarged firm liver with knobbly surface appearance. Additionally, there were adhesions from the myocardial apex to the pericardium, copious white froth in trachea and bronchi, and a reddened intestinal mucosa.
Samples were submitted to the Wollongbar RVL (WN05/xxxx) and histology revealed lung congestion, oedema and hepatic periacinar congestion: the conclusion was acute congestive heart failure.
The post-mortem, histology and history all suggest a diagnosis of gossypol poisoning. This is a relatively rare occurrence in this area in my experience. Soil tests were unavailable so chelating potential of the soil etc. was unable to be followed up at this stage. The fact that the owners had not added calcium to the whole cottonseed could have been a contributing factor and the fact that there was obviously well below the recommended available paddock roughage for cottonseed feeding may have also contributed to the syndrome.
Apparently the more recent solvent extraction techniques may result in higher levels of gossypol which would usually have been deactivated by heating. The owners began feeding whole cottonseed in raised troughs out of reach of calves until weaning. There were no further deaths. Unfortunately the gold standard test for gossypol poisoning is measuring gossypol content of the cottonseed / meal– at the time of writing this test was unavailable in Australia.