58 EXPERIMENT STATION BULLETIN 351 



compared with a 1000-pound adult animal the average daily increases by 

 months were respectively 12.7, 10.4, 9.3, and 7.0 pounds. 



About 90 per cent of this increase in body weight could be accounted 

 for by the deposition of protein as body flesh which indicates that the 

 growth trend is extraordinary at the start, but declines rapidly during the 

 first four months. Even with a liberal supply of food energy, the extra- 

 ordinary activity of the body tissues (metabolism) in early life burns up 

 so much energ) that relatively little fat is deposited at this time. 



The utilization of digestible protein intake decreased from an aver- 

 age of 89 per cent (on milk only) during the first moiith to 77 per cent 

 during the second, 70 per cent during the third, and 61 per cent during 

 the fourth month. In other words, the biological value of the digested 

 protein decreased as grain and hay gradually supplied a greater propor- 

 tion of it. This does not indicate any particularly favorable associative 

 effects, but rather a comparatively low order of biological values for 

 cereal proteins. 



That biological value of protein for growth is determined not only 

 by the character of the nitrogenous constituents consumed, but also to a 

 material degree by the physiological adaptability of the individual to 

 utilize these constituents, is apparent during the first month when utiliza- 

 tion of milk protein (for growth) b\^ individual calves \\as respectively 

 96, 80, and 87 per cent. Similar individual differences were obtained in 

 the percentages of metabolizable energy that were applied to net use. 



The complete report of this investigation is now prepared for publi- 

 cation as a station bulletin. 



E. G. RiTZMAN, N. F. CoLovos, A. D. Littlehale 



Nutrition Studies with Lactating Cows 



The work during the current \ear includes ten experiments in which 

 the complete ingo and outgo of matter and energy of lactating cows was 

 measured by means of digestion balances and metabolism experiments. 

 Simplified rations, containing for the most part cornmeal, ground oats, 

 Vvheat bran, and linseed oil meal in proportions of 1-2-2-1 by weight, have 

 been used. 



These experiments are still in progress (now in their second lactation) 

 and no final conclusions are advisable until this second lactation is com- 

 pleted when the whole picture can be presented. However, some general 

 observations may be reported at this time. 



The simplified feed mixture was entireh' satisfactory. The grain mix- 

 ture averaged between 12 and 13 per cent digestible protein which is 

 much lower than is commonly used. A production of 40 pounds of milk 

 was maintained on 8 pounds of this low protein mixture with pasture up 

 to the middle of August when pasture conditions declined, parth' due to 

 drouth. In this case the ratio of grain to milk was 1-5. 



No attempt was made to encourage maximum potential production 

 during the earlier stage, the grain when fed in dr\- rations w ith beet pulp 

 and mixed grass hay being kept at the ratio of one pound to about 4.6' 

 pounds of milk. The grain was, however, gradually later increased to a 

 ratio of one pound to about 3.0 pounds of milk to maintain the >'ield. On 

 this treatment one heifer produced 11182 pounds of milk testing 4.3 per 



