A SURVEY OF DAIRY HERDS IN THE FRASER VALLEY OF BRITISH COLUMBIA TO DETERMINE POSSIBLE CAUSES OF UNSATISFACTORY REPRODUCTIVE PERFORMANCE

In a preliminary study of reproductive performance of 261 dairy herds in the Lower Fraser Valley of British Columbia for the period 1966 through 1970, mean non-return rate was 4.7% less in 1970 than in the previous 4 yr. In February 1972, factors associated with the reproductive performance of 68 herds in the same region were studied in greater detail. Herd non-return rates for 1971 were estimated from artificial insemination (AI) unit records. Feed samples, soil samples, feed intakes, and herd production levels were obtained for each period. The results indicated that differences in mineral nutrition between herds were associated with reproductive performance. The Cu/Mo ratio in silage was the most important factor, with increases in Cu relative to Mo being associated with low herd non-return rates. Other minerals found to be important included the Cu/Mo ratio in hay and grain, Cu in hay, Mo and Se in grain, Ca and P in silage and the variability of soil Mg levels. The type of forage fed was also important, with herds receiving diverse rations having higher conception rates than those restricted to one type of silage and/or hay.