338
ABSTRACTS
single dosing, although evidence leans in favour of the latter. The authors do not
consider the drug, at its present price and its high dose required for reduction of
worm count, as an economically satisfactory anthelmintic for prophylaxis. [S. K. S.]
The nutritive value of proteins for milk production. S. MORRIS AND
S. C. RAY (1939). J. Dairy Res. 10, 165-85
I N the present study are included the following investigations : (1) the effect of high
temperature treatment in the nutritive value of protein of young spring grass for milk
production, (2) the comparative biological value of proteins in dried autumn and spring
grasses for milk production, (3) the supplementary effect of the proteins in the mainte-
nance ration on that of production ration, (4) the effect of feeding high protein ration
on milk production. Studies on systematic nitrogen metabolism were also made through-
out the whole investigation in each case.
The investigations under head 1 and 2 were conducted on six Ayrshire cows, each ani-
mal having calved four to six weeks back. The weights of the animals varied from 950
to 1,100 lb. Throughout the experiment each cow received a maintenance ration of
straw, oats and beet pulp at the rate of 6 lb. S. E. (Starch equivalent) and 0.6 lb. P. E.
(Protein equivalent) per 1,000 lb. live weight. The production ration was fed at the
rate of 2.5 lb. of S. E. and 0.44 lb. P. E. per 10 lb. of milk. The concentrates under
investigation, were given in the production ration in quantities, which supplied equiva-
lent amounts of nitrogen to the ration, the rations being balanced with oats and maize.
To obtain the high-temperature dried grass, the drying temperature was increased
from 300°C. (the normal drying temperature) to 350°C. The results show that high-
temperature dried spring grass caused no fall in milk yield in comparison with low-tem-
perature dried spring grass. On the other hand, the grass cut in autumn, appeared to
reduce the milk yield. The nitrogen excretions in milk and urine led to a relatively
high wastage of nitrogen via urine when dried autumn grass was fed. A study of nitrogen
metabolism showed that high-temperature drying had no effect, whereas marked effects
were noticed with the autumn grass. The hippuric acid nitrogen output decreased
with high-temperature dried grass possibly due to the loss on drying of benzoic acid.
It also appeared that the high-temperature treatment had in some way affected the
nature of sulphur compounds in the grass, with a consequent diminution in the
retention.
The investigations under heads 3 and 4 were conducted on three Ayrshire cows, each
having a calf of four to six weeks. The weight of the cows varied from 930 lb. to 1,050 lb.
To study the supplementary effect of the maintenance protein on production protein,
the roughage was varied by using either hay or straw. While the nitrogen supply
remained the same, the amino-acid make up, especially the lysine content, was higher in
the ' hay ration ' than in the ' straw ration '. The production protein intake in both
cases was of poor biological value. In order to feed excess protein, the production
protein intake was increased from 0.44 lb. P. E. per 10 lb. of milk, to 0.60 lb. P. E. The
results show that when ' straw protein ' replaced ' hay protein ' the milk yield was below
the expected level. With an excess of protein in the ration, most of the excess nitrogen
was eliminated in the urine, and both the milk yield and the biological value of the food
protein fell considerably. Furthermore, the results of the high protein diet confirmed
those obtained in the previous experiments carried out by the authors, in which a poor
quality of protein fed at the end of lactation and the addition of more than sufficient
lysine did not maintain the milk production at the normal level. This failure was not
due to any inadequacy of the quantities of essential amino-acids of food protein for milk
production, but to the lack of definite proportions of these amino-acids for better utiliza-
tion. Nitrogen metabolism in high protein dietary showed an increased excretion of
ereatinine, though no extra creatinine was fed in the food. The purine metabolism varied
with the total nitrogen excretion, the allantoin increasing markedly in the high protein
period. [S. C. R.]