212 Scientific Proceedings, Royal Dublin Society. 



therefore tested on animals already receiving at least the minimum protein 

 requirements referred to. Three lactatin,^ goats were used, and the tests 

 continued from the beginning of May, 1922, to the middle of December, 1922. 

 The yield of milk, the percentage of milk fat, and the total milk fat from each 

 goat were determined daily, and the animal's weight was recorded weekly. 

 Curves were drawn of the total milk yield, percentage of fat in the milk, total 

 fat in the milk, and weight of animal; the figures 1, 2, and 3 represent the 

 result from the individual goats, and show the daily ration supplied to 

 them. By examining the milk and fat curves in eonji;nction with the curve of 

 body weight for successive periods during which comparative foods were fed, 

 it is possible to observe the effect produced on the milk fat by the comparative 

 diets. It is known that the proportion of sugar in milli is nearly constant, 

 and that the changes in the percentage of protein are small and irreg-ular — 

 Paton and Cathcart (1911), and Eckles and Palmer (1916) : consequently the 

 consideration of the sugar and nitrogen content of the milk can be reasonably 

 neglected. Each animal was separately fed and housed. A basal daily ration of 

 hay lib., mangels 10 lbs., crushed oats ^ lb., and white fish meal Jib. was given. 

 From previous experience with the same goats, this ration was deemed barely 

 sufficient to maintain weight and give a moderate flow of milk; and it was 

 calculated that the ration contained sufficient protein to supply the animal's 

 protein requirements and also to provide for the protein secreted in the milk. 

 In a previous paper — Sheehy (1922) — the author showed the effect on the milk 

 fat of increasing this ration, so that particular test was excluded in this ease, 

 and the basal ration was supplemented from the beginning by fat, carbohydrate, 

 or protein. The fat used was hydrogenated soya bean oil, the carbohydrate was 

 maize starch, and the protein was casein. As the milking period advanced, the 

 fat, starch, and casein were interchanged and the effects produced on the fat 

 yields noted. 



The total yield of milk in all three cases gradually increased after parturition ; 

 it maintained a high level for some time, and declined towards the end of the 

 lactation period. Fortunately the individual milk jdeld remained constant for 

 coiisiderable periods, and by effecting changes in the food during these periods 

 of constant millv yield it was possible to show very definite effects on the milk 

 fat from' the change in food. Unfortunately on other occasions changes in 

 the diet synchronised with variations in the milk yield; but, since the 

 effect on the total fat of the variation in the milk yield could be easily 

 calculated, the part played by the food was, even in these eases, determined. 

 It will be noticed that in fig. 2 there is a considerable fall in yield at the 

 beginning of period C ; this is clue to illness from which the animal suffered 

 during periods C and D. ■ In comparing period A with 'B in fig's. 2 and 3, 

 reference must be made to fig. 1, which serves as a control in this connexion. 

 Fig. 1 shows the natural inclination for the yields of milk and butter fat, and 

 it will be noticed that, while the gTaphs in fig. 3 (periods A and B) follow a 

 similar course to those of fig. 1, the percentage and total milk fat curves in fig. 2 

 are raised in period B. In the case of each animal the daily ration was reduced 

 to the basal level during the last period of the experiment. This change caused 

 a considerable drop in both the percentage of, and the total milk fat, which shows 

 that the previous increase was not the consequence of advance in lactation 

 period, but rather of change of diet. All three goats increased rapidly in weight 

 for the first three or four weeks, after which the increase in weight was very 

 slight but fairly regular right up to the end of the lactation period. The small 

 irregularities in the weight curve are principally due to slight variations in 

 health, caused by irregularity of the action of the bowels to which goats con- 

 tinuously confined to the house are subject. 



