Effects of cadmium on reproduction, an epizootologic study

The Dutch part of Kempenland has been exposed to cadmium pollution since the last century. Experimental data suggest effects by cadmium on reproduction such as diminished fertility, decreased foetal growth, and specific malformations. Use was made of a historical cohort of dairy cows, ascertained from a surveillance program conducted by the regional Veterinary Health Service between 1976 and 1986. Ten dairy farms in the cadmium region were matched by size with 40 dairy farms from a reference area. Logistic models were used to calculate Odds (OR) and Rate Ratios (RR) and their 95% confidence interval. In total 4,039 exposed and 15,552 reference gestations were compared. The reasons for the slaughter of 574 exposed and of 2,824 reference cows were ascertained. A lower twinning rate [OR = 0.63 (0.47-0.84)] was found and more birth complications, for both calves [OR = 1.50 (1.25-1.80)] and cows [OR = 1.49 (1.24-1.79)]. More inseminations [OR = 1.20 (1.01-1.43)] were needed for conception in the exposed area. Deaths among twins [OR = 1.66 (0.90-3.07)] were not significantly higher. Perinatal death, premature death, age at, or reasons for, slaughter were not consistently different. These results are consistent with those of other observational and experimental studies. Extrapolation from these large domestic animals to humans is problematic, as is the more frequent extrapolation from rodents to humans. It can be concluded that longterm exposure to low levels of cadmium is associated with impaired reproduction in dairy cows.