Antifertility Effects of Dithiocarbamates in Laying Hens

This report compares the antifertility activities in laying hens of various dithiocarbamates including the fungicides thiram, ziram, zineb, maneb and ferbam, and the alcohol deterrent antabuse. Ziram at 200 ppm in the diet or thiram at 125 ppm stopped egg production within 2 days and caused marked ovarian atrophy after 7 days. Ferbam at levels between 200 and 600 ppm and antabuse at levels between 125 and 500 ppm reduced but did not eliminate egg production and caused only slight ovarian regression. In contrast, zineb and maneb were without effect when tested at 600 ppm. The antifertility effects of thiram were fully reversible, since hens treated with 250 ppm for either 10 or 14 days resumed egg production after treatment, and within 5 weeks exceeded their rate of production prior to treatment. Additionally it was found that daily injections of porcine FSH could reverse the antigonadal effect of thiram, and a single injection of LHRH could overcome its anovulatory effect. Reversal by LHRH suggests that thiram might block fertility by an action within the central nervous system.