NATURE AND RATE OF GROWTH IN LAMBS DURING 
THE FIRST YEAR 
By E. G. Ritzman, 1 
Animal Husbandman , New Hampshire Agricultural Experiment Station 
THE PROBLEM 
The data presented herewith furnished material for an analysis of the 
nature and rate of the development of lambs during their first year of 
growth. 
The primary object in view in obtaining these data was the establish¬ 
ment of the normal rate of growth of definite somatic characters for 
specific periods during this first year of development. The data secured 
for this purpose, however, were used also in a study of correlation. 
In planning this experiment it was decided to take the first record at 
2 weeks of age after the lambs had straightened out somewhat, the 
second at 4 weeks, thereafter monthly up to 3 months of age, and from 
this time on quarterly up to a year of age. Consequently each lamb was 
weighed and measured on the dates when it attained these respective 
periods of age for the first three periods. After the third record was taken, 
which was at 8 weeks of age, it was found impractical to proceed on this 
basis, because of the time required to attend to each individual lamb on 
the date it would attain the age for measurement, so they were divided 
into groups each of which contained lambs which were within a week 
of the same age. By taking records of a whole group at one time con¬ 
siderable time was saved. The fourth period covers only 3 weeks instead 
of 4, as it was found necessary to turn the flock out on pasture at this 
time when the oldest group of lambs reached the age of 11 weeks. This 
record was therefore taken before going to pasture, which was one week 
ahead of the intended schedule because the first week on pasture might 
result in a temporary reaction to growth owing to the ewes' adjustment to 
change of feed. The growth periods for which measurements were taken 
beginning with the second week as shown in Table II are: 
xst period 
2d period. 
3d period. 
2 weeks 
4 weeks 
.3 weeks 
4th period 
5 th period 
7th period 
13 weeks 
16 weeks 
12 weeks 
1 Acknowledgment for courteous cooperation is due to members of the Station for Experimental Evolution 
of the Carnegie Institute, notably to Dr. C. B. Davenport for valuable suggestions and criticism in the 
preparation of the manuscript and to Dr. J. A. Harris for recalculating and checking the tables of data. 
(607) 
Journal of Agriculture Research, 
Washington, D. C. 
kz 
Vol. XI, No. 11 
Dec. 10,1917 
Key No. N.H.—4 
