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In addition, a scratch feed of 2 parts of fine cracked corn, 1 part of cracked wheat and 1 part of pinhead oats was fed separately from the second day through the third week. Thereafter the scratch grain was incorporated in the mash in the ratio of eight paris of mash to one of cracked grain. This change was made necessary by the preference of the chicks for mash to which supplements (as described below) had been added and their refusal to eat the scratch feed.
From the second through the sixth day after hatching, the chicks were fed sparingly with scratch grain, and had water before them at all times. Beginning on the seventh day, all were fed dry mash in small hoppers, the mash being fed five times a day for tifteen minutes at a time until they were fourteen days old, after which time it was kept before them at all times. As supplements, cod liver oil and yeast* were added to the mash. Beginning on the seventh day the four lots were fed as follows:
Lot 1-Control—Basic mash and grain only.
plus 2% cod liver oil. Lot 3
plus 42% yeast vitamine. Lot 4
plus 2% cod liver oil plus 12%
yeast vitamine. The amounts of cod liver oil and yeast to be added to the mash were calculated on the basis of total estimated food intake, assuming equal consumption of mash and scratch grain. For the first two weeks of differential feeding, more mash than grain was consumed, and since the mash only contained the supplements, slightly more than the intended proportions of cod liver oil and yeast were consumed. After the third week the proportions of supplements in the total food intake were as given above.
All chickens were weighed individually at the beginning of the experiment and weekly thereafter. The chicks in all lots were healthy and active and made normal growth until they were four weeks old. One chick each in Lot 1, (controls) and Lot 3 (yeast) died in the second week of the experiment, but apparently not from causes connected with feeding. After the fourth week, Lot 3 (yeast) began to fall behind the others in rate of gain in weight. Leg-weakness developed in this lot during the fourth and fifth weeks, and all chicks in this lot died, apparently from leg-weakness, during the fifth, sixth and seventh weeks. In Lot 1 (control), the rate of gain fell in the sixth week, symptoms of leg-weakness appeared and all except two chickens died before the end of the eighth week. The two survivors had leg-weakness in lesser degree than the others, but succumbed in the ninth week. There were no deaths in either of the lots which received cod liver oil. The gains made by the chicks in these lots, while not as great as might have been expected under good outdoor conditions, were satisfactory, the rate of gain for Lot 4 (cod liver oil and yeast) being somewhat greater than the rate for Lot 2 (cod liver oil)
*Yeast Vitamine Harris Powder.
TABLE 1. Average weights of chickens reared in the laboratory on diets' with and without cod liver oil and yeast.
1 36.7 2 49.5 3 78.0 4 113.1 5 153.8 6 199.3 7 193.6 8 224.3 9 all dead
36.0 46.9 69.2 102.6 144.6 203.0 230.2 283.4 348.5
10 10 10 10 10 10 10 10 10
38.7 54.5 82.2 109.5 125.0
38.0 53.3 84.8 126.8 167.3 226.8 287.2 351.4 424.6'
156.0 all dead
10 10 10 10 10
*Storrs ration of mixed grains plus supplements. 'In comparing weights of Lots 2 and 4 allowance should be made for
the fact that Lot 2 contained only four males (which are heavier at this age) while Lot 4 contained six males. When correction for sex is made, the difference between the lots is not as marked as
it appears. 'Lot 3 received somewhat less light than Lot 1 so that the growth of
the two lots is not strictly comparable.
(see Table 1.) The chickens in these lots at nine weeks of age were healthy and active, and appeared to be normal in all respects (see Fig. 2, 3, and 4.) except that they were pale. probably because of the small amount of yellow corn in the ration, and were somewhat less well fleshed than out-of-door chicks of the same age.
F.g. 2. Two lots of ten chickens each reared on the brooder table in
Fig. 1. In addition to a grain mixture and water the lot on the left received cod liver oil (2%) and the lot on the right cod liver oil (2%) and yeast vitamine (12%). Photographed at nine weeks
The results of this experiment show: (1) that chicks can be reared under strict confinement indoors, from hatching to nine weeks of age which is usually past the danger period of growth; (2) that a ration which will support growth out-ofdoors under natural conditions must, when fed indoors, be supplemented by the vitamines of cod liver oil or some similar supplement; (3) that the addition of yeast to the ration did not prevent leg-weakness, nor suffice for good growth or survival in the absence of cod liver oil; (4) that sufficient roughage for growth and survival was provided by the tibre in the ration.
We do not regard the ration used as perfect by any means. It is probable that it would be improved by the addition of milk, green food, a good scratch litter, and the provision of more direct sunlight. The experiment is not conclusive with regard to the proper amounts of cod liver oil, yeast, or minerals to be used. We publish it as a suggestion for the type of feeding procedure which may be used in rearing chicks indoors.
Growth under even more artificial conditions than those obtaining in this experiment have been secured by other investigators. At the Wisconsin Experiment Station. Hart Steenbock. Halpin and associates have secured growth and survival indoors on a ration of white corn, minerals, skim milk and cod liver oil with shavings for
F.g. 3. Nine weeks old cockerel from right
hand lot in Fig 2. litter. Where the chicks were exposed to unfiltered daylight all day, it was found that the cod liver oil could be omitted from the ration without causing leg-weakness. There is some evidence that a part of the beneficial effect of sunlight may be secured by exposing growing chickens to the light from quartz mercury lamps. Light from ordinary electric lamps is not effective in this way. It is apparently the violet rays of sunlight or of an artificial source of light which are beneficial to chickens and these rays fail to pass through ordinary window or lamp glass, but will pass through quartz glass. Whether or not they are affected by passage through the muslin curtains frequently used in brooder houses for young chicks has not been ascertained, but since muslin soon soils, and becomes partially opaque, the amount of light which passes through is usually small.
Experiments now in progress at this station have served to confirm the earlier findings in regard to the efficacy of cod liver oil as a preventive and a cure of leg-weakness, and have in addition provided some data on (1) the amounts of cod liver oil which must be added to a ration known to be free from the anti-rachitic substance, (2) a satisfactory amount of roughage to be incorporated in the ration adopted, (3) the deterioration of the anti-rachitic substance under one method of storage.
The basic ration used in these experiments was the same as that adopted by Hart, Steenbock and associates (1922) with the exception that we have incorporated in the ration a measured proportion of roughage in the form of pine sawdust. Our basic ration consists of pasteurized skim milk given freely as drink, and a mash made up as follows:
Grams % White corn meal
873.0 97.0 Nutrients Calcium carbonate (CaCo')
2.0 Common salt (NaCi)
1000.0 To this ration have been added various supplements as proportions of the total nutrients.
In the present experiments, four lots of thirteen White Leghorn chicks each from our inbred family No. 8 (hatched J:wuary 8) were placed on a ration of cracked white corn and skim milk from the second through the sixth days after hatching. After the seventh day all lots received skim milk and the mash described above with the addition of supplements as follows: Lot 1--Mash + 42% Cod Liver Oil (Harris) 2
+ 2% + 1%
(in dry mix)