ESCHERICHIA-COLI ENDOTOXIN-INDUCED MASTITIS IN DAIRY-COWS - CHANGES AND IMPORTANCE OF INSULIN-LIKE GROWTH FACTOR-I AND OXYTOCIN

Four cows were injected E. coli endotoxin (ECE) into the left front qu arter and 5 wk later into the right front quarter. 9 h after the injec tion of ECE and daily on the following 6 d, insulin-like growth factor I (IGF-I) was injected into the inflamed or into the untreated front quarter. After ECE administration, milk IGF-I concentration increased within 3 h, and rectal temperature and somatic cell counts within 5 h increased in the inflamed quarter, whereas milk lactose and fat concen trations decreased. Milk yield was decreased in all quarters. Reductio n of milk yield was maximal 24 h after ECE administration and was espe cially marked in the inflamed quarter. Plasma concentrations of oxytoc in remained basal during the d after ECE and increased in a normal man ner in response to teat stimulation and milking. Plasma concentrations of IGF-I and growth hormone did not significantly change in response to ECE administration, whereas plasma glucose concentration increased after ECE injection. The recovery of somatic cell counts, milk yield a nd concentrations of milk components was not influenced by the daily i .mam. administration of IGF-I. After ECE injection there is an increas e of i.mam. secretion of IGF-I, whose biological effect, if any, is no t clear because i.mam. injection of IGF-I had no effect on the recover y from ECE induced injection. As oxytocin release was normal during mi lking after ECE injection, the reduction of milk yield is most likely due to reduced milk synthesis and secretion.