Relationship Between Vitamin A and β-Carotene in Blood Plasma and Milk and Mastitis in Holsteins

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Abstract
Blood and milk were sampled and quarter California Mastitis Test scores were taken during four 2-wk periods from 45 lactating cows. Vitamin A and .beta.-carotene in plasma and milk were analyzed within 48 h after collection. Total vitamin A equivalent (2 .times. amount of .beta.-carotene plus amount of vitamin A) also was calculated. The total amount of vitamin A and .beta.-carotene excreted in milk was calculated from concentrations of vitamin A and .beta.-carotene in milk and milk weights recorded on sampling day. Independent effects of lactation number, period of collection, days in lactation and California Mastitis Test Scores (the highest test score of 4 quarters used in the analysis) were examined by least-squares procedures using each blood and milk measure as the dependent variable. Results showed a highly significant independent effect of California Mastitis Test Scores for concentrations of plasma vitamin A, .beta.-carotene and total vitamin A equivalent. Cows with lower plasma vitamin A, .beta.-carotene and total vitamin A equivalent had higher test scores than cows with higher vitamin A and .beta.-carotene. Similar comparisons for amount of milk vitamin A, .beta.-carotene, and total vitamin A equivalent and total amount of each component excreted in milk showed nonsignificant independent effects attributed to California Mastitis Test. Low concentrations of vitamin A and .beta.-carotene in plasma were associated with severity of mastitis in cows.
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