Abstract
Summary Plasma protein-bound iodine values (PBI) were determined at 60 days postpartum on 93 Holstein cows (139 lactations) and 34 Guernsey cows (57 lactations) over a 3-yr. period. This measure was correlated on “among lactations” and “among cows in lactation” bases, with certain concurrent measures of reproductive and lactational performance. Measures of reproductive performance included interval from parturition to conception, interval from parturition to first estrus, interval from first breeding to conception, and number of services per conception. Measures of lactational performance included 240-day 4% FCM production, maximum initial 4% FCM yield, persistency index, fat percentage, and solids-not-fat percentage. The Holstein data on “among lactations” basis gave significant coefficients of correlation between PBI and interval from first breeding to conception (-0.67*) and services per conception (-0.69*). On an “among cows in lactation” basis, the Holstein data also gave significant coefficients of correlation between PBI and interval from parturition to conception (-0.23**), interval from first breeding to conception (-0.25**), services per conception (-0.21*), and fat per cent (-0.18*). No other coefficients of correlation in either breed reached the level of statistical significance.
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