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ABSTRACTS
cerned with the ' relationships of the excretion of carotene in the faeces of cows to carotene
intake and to the concentration of carotene in the blood serum'. An earlier study
showed that 0.086 per cent of the daily carotene intake of cows stall-fed green rye only
was deposited in the butter as carotene and 0.154 per cent as vitamin A ; another with
vitamin C showed excretion of body stores. Together they suggested this latter con-
dition may also be true in the case of carotene.
Six yearling heifers and 17 lactating cows were used. Experimental rations provided
from 0.0028 to 2.51 mg. carotene daily per kg. body weight. Winter supplemented rations
included atlas sorgo silage, dehydrated fresh green oats or a carotene concentrate. A
summer ration including green grass was suddenly changed to beet pulp and grain, an
almost carotene-free ration. Spectrophotometric determinations by a modified Guilbert
method were made on separate parts of each ration, 24-hour faeces samples and blood
taken daily from the juglar vein.
Large variations of faecal and blood carotene levels were typical. Averages for three-
successive days are used in every case. The amount of carotene excreted by heifers
that received cottonseed meal, straw sprinkled with molasses and silage was 3.2 times
as much as those getting all but the silage, although the intake was nearly five times as
much. When large quantities of the carotene concentrate were suddenly added the low
carotene intake group responded much better than the group getting silage. The blood -
carotene value of cows on the low protein intake was nearly twice as large as that of
heifers on the same ration. Alfalfa fed for 40 days preceding the shorter experimental
period in the case of the cows (six weeks for cows and five months for heifers) may have
had a residual effect that would have accounted for this. The response in blood
carotene to the addition of the carotene concentrate was of the same order in both cows
and heifers on low carotene ration. Feeding histories in carotene metabolism are, there-
fore, quite important.
Substitution of alfalfa, corn and bran for cottonseed meal, straw and molasses increased
the carotene intake three times, had little effect on the carotene output: input ratio
increased the blood-carotene level more than twice and improved milk flavour. On
further increasing the carotene intake by the addition of dehydrated oats, the carotene
utilization increased, but this effect gradually disappeared. The authors found that
even prolonged feeding of the highest carotene level of winter feeding would not increase
the blood-carotene level to that under pasture conditions ; they suggest that there may be
other factors in green grass responsible for the higher assimilation of carotene.
Animals on grass, yellow corn, bran, alfalfa and silage were suddenly changed to
linseed meal, molasses and beet pulp. Carotene output in the faeces dropped 98 per cent
and the blood-carotene 42 per cent the first week. After two weeks, however, the latter
value was still above that of animals on alfalfa and grain for six weeks. This is further
evidence of residual effect or the value of feeding histories in such studies.
Classification of lactating cows on the basis of ration usually classified them on the
basis of milk that would or would not produce oxidised flavour. With intakes of below
0.075 mg. carotene per kg. body weight the milk developed this defect. In such cases
excretion of carotene was usually over 130 per cent of intake. With intakes of above
0.300 mg. per kg. body weight the milk did not develop an oxidised flavour and the out-
put of carotene was 100 per cent or less of the intake.
The data indicate that at intake
levels of 0.306 and 0.266 mg. per kg. body weight the maintenance of high blood-carotene
level may compete with the production of milk of a good flavour. The fact, however,
that the five lowest carotene intakes were among cows producing good flavoured milk
suggests that other causes are also responsible for this flavour defect in milk. Some
animals may care for the needs of their own body first, or those with higher blood carotene
levels, producing at the same time off-flavoured milk, are less able to convert carotene
into vitamin A. [J. N. W.]
A consideration of the life-cycle of Fasciola in South Africa. F. G. CAWSTON.
(1940). S. A. Med. J. 14, 84.
T HE author has confirmed the observations of Dr Annie Porter that Lymnæa nata-
lensis harbours Cercaria pigmentosa which are the larval stages of Fasciola gigantica,
but he found that this infection is very rare in these molluscs. He did not, however,
succeed in infecting these molluscs with the miracidia of F. hepatica. Lymnæa trun-
Catula occurs in the Union of South Africa, but it is very rare. The author has found only