Negative effects of a high level of nutrient intake on mammary gland development of prepubertal goats

Ten French Alpine kids were used to determine whether mammary development was altered by level of nutrient intake during the prepubertal period. At 6 wk of age, kids were paired on the basis of BW and assigned to an ad libitum or restricted diet of milk from Jersey cows. Kids on the restricted diet were fed 70% of their pair mate's milk intake for 4 wk and then 50% for 9 wk. Low quality grass hay was available for all kids. The ADG was greater for kids fed for ad libitum intake. Kids fed for ad libitum intake had larger mammary glands and increased adipose deposition. Measurement of hydroxyproline indicated that connective tissue increased with gland size. Kids on the restricted diet had more DNA and protein per gram of mammary gland, indicating greater secretory development. Goats can be used as a model to study the effect of level of nutrient intake on hormones and growth factors that regulate mammary gland development.

Distribution of plasminogen activator forms in fractions of goat milk

Distribution of plasminogen activator forms in fractions of goat milk was examined. Raw milk was centrifuged to separate skim milk, cream, and a somatic cell pellet. Somatic cell extracts were obtained by sonication. Skim milk was centrifuged to separate milk serum and casein micelles. Activity of plasminogen activator was detected in casein, serum fractions, and in association with somatic cells. Plasminogen activator forms in milk casein had approximate molecular weights of 75,000, 50,000, and 30,000. The predominant forms of plasminogen activator in milk serum and in association with milk somatic cells had molecular weights of 30,000 and 50,000. Based on fibrin dependency and inhibition of activity in the presence of amiloride, the forms at 30,000 and 50,000 represent urokinase-plasminogen activator, and the form at 75,000 represents tissue-plasminogen activator.