Íslenskar landbúnaðarrannsóknir - 01.09.1974, Blaðsíða 8

6 ÍSLENSKAR LANDBÚNAÐARRANNSÓKNIR
600-
Thoosands of
ovocysts pr.g
faeces

500-
A Six lambs; faecal
• samples taken tvo
® ormoretimes.
□
400'
x Sixlombs; faecal
samples taken once.
300-
200-
A
100-
A
□
X . * n‘5 .
0 + m , noiýe-------------Br— ---—►
10 15 20 25 30 35 40 45
Age of lambs in days
Fig. 1. Eimeria ovocysts in faeces of young lambs
(Group X).
fell quickly. By the fortieth day the number
of ovocysts did not exceed 20 thousand in
any of these lambs.
The number of ovocysts in the faeces of
sheep of different ages was recorded weekly
except during the summer from November
1971 to December 1972. The results are pre-
sented in Fig. 2.
Ewes and rams showed no differences in
ovocyst numbers. Signs of coccidiosis were
not evident in any animal.
Ovocysts were found in all faecal samples
in the age group 4 months to l1/? year. All
seemed to follow the same general pattern
although there was considerable variation
between single countings.
Sheep older than two years could have as
many as five thousand ovocysts pr g faeces
but most often the number was much smaller
and sometimes nil. However, no adult sheep
were completely free of ovocysts throughout
the period of the study. No age-related varia-
tion in ovocyst number could be seen in
sheep older than 2 years.
Coccidiasis in lambs most likely reaches
maximum between the 15th and 20th day of
age, but after that time the lambs seem to
have developed considerable resistance to
Eimeria spp. The resistance, however, is not
fully developed until the sheep are over 2
years of age at least. The resistance is never
complete and adult sheep have ovocysts most
of the time but in small numbers.
There is a sharp increase in ovocyst num-
ber in late November or in the beginning of
December (Fig. 2), but this increase is much
smaller than in the spring when the lambs
are a few weeks old. The reasons for this
increase in the winter are uncertain although
Fig. 2. The mean number of Eimeria ovocysts in faeces of sheep of different ages.