Effects of Breed, Pregnancy, and Lactation on Weight of Organs and Tissues in Dairy Cattle

Abstract

Twenty-five Holsteins (15 lactating, and 10 nonpregnant nonlactating) and 23 Jerseys (7 lactating, 9 nonpregnant nonlactating, and 7 pregnant nonlactating) were slaughtered; carcass, liver, heart, kidneys, mammary gland, skin, lungs, spleen, adrenals, rumen, omasum, abomasum, small and large intestines, and visceral fat were weighed. Log-log regression analysis was used to compare tissue weights for common body weight and to develop equations for predicting tissue weights from body weights. Expressed on common weight: (1) skin (hide) and lungs were 27 and 21% larger for Holstein than Jerseys; (2) heart and mammary gland were 12 and 34% larger in pregnant Jerseys than in nonpregnant Jerseys; and (3) liver, heart, mammary gland, lungs, rumen, abomasum, intestines, spleen, and adrenals were 25, 22, 73, 22, 20, 35, 31, 20, and 19% larger, and carcass and skin were 8 and 5% smaller in Iactating compared to nonlactating cows. Changes in tissue weights may be related to differences in maintenance energy expenditures for lactating versus nonlactating cows.