COLONIZATION OF MICROORGANISMS IN THE RUMEN OF YOUNG CALVES

Sequential colonization by various kinds of microbial populations in the rumen of calves was investigated. Four calves were fed with colostrum for 3 days and thereafter fed with 4l of cow's milk daily until 4 weeks of age. They had access ad libitum to a good quality hay from 10 days of age and to a concentrate from 2 weeks of age. The rumen was rapidly colonized by microbes immediately after the birth of the animals. The first bacteria which developed most abundantly in the rumen were Escherichia coli and streptococci. The numbers of E. coli, which were high in 1-day-old calves, decreased gradually to reach a constant level within 6-8 weeks of age. The numbers of streptococci, which were high during 8 weeks after birth, decreased in a 10-week-old calf. The numbers of lactobacilli, which were high in a 1-day-old calf, increased in a 2-week-old calf, and thereafter remained constant. Amylolytic bacteria were present abundantly in 1-day-old calves. The numbers which increased in 3-day-old animals remained constant thereafter. The numbers of sulfate-reducers, lactate-utilizers, xylan-fermenters and pectin-fermenters which were low in 1-day-old calves, increased within 3 days after birth, and thereafter the levels remained constant. The cellulolytic bacteria which began to appear in animals 3-5 days of age, became abundant in calves 2-3 weeks old. The methanogenic bacteria which were present in calves 1-2 weeks of age became abundant when the animals were approximately 3 weeks old. The abundant appearance of sulfate-reducers, xylan-fermenters and pectin-fermenters in 3-day-old calves was new observation. The constitution of the anaerobic bacterial population in generic level in the rumen of a calf changed with age after birth. The constitution of predominant bacteria in the rumen of a calf at both 1 day old and 10 weeks old was similar to that of mature cattle. The composition of volatile fatty acids (VFA) in the rumen contents of calves changed with age after birth. The colonization by protozoa was observed in 8- to 10-week-old calves. Also, the importance of microbial interaction in the colonization by microorganisms in the rumen of calves is discussed in this report.