20 EXPERIMENT STATION BULLETIN 354 



fairly good amounts of phosphorus were inchided, normal calcium and 

 phosphorus levels \^ere maintained in the blood with only pulverized lime- 

 stone and salt as mineral supplements. 



The nitrogen and energy balances were carried out in co-operation 

 with the Animal Husbandry Nutrition Laboratory. 

 K. S. Morrow, H. A. Keener, S. R. Shimer, N. F. Colovos, A. E. Terri 



* 



Improving the Solids-Not-Fat Content of Milk by Selective Breeding 



Sixteen sires have now been proven, including nine Holsteins, three 

 Ayrshires, three Jerseys, and one Guernsey. Ten of the 13 sires on last 

 year's annual report were re-proven by adding new lactation records. 



Ten sires increased and six sires lowered milk production;* 11 in- 

 creased and five lowered fat percentage ; 1 1 increased and five lowered the 

 percentage solids-not-fat. Eight sires increased both the fat and the solids- 

 not-fat percentage ; two lowered both the fat and the solids-not-fat per- 

 centage ; three increased the fat percentage and lowered the percentage 

 solids-not-fat ; and three decreased the fat percentage and increased the 

 solids-not-fat percentage. 



Placing the sires in groups where fluctuations were similar with ref- 

 erence to milk production, percentage butterfat, and percentage solids-not- 

 fat (Ex. -j-milk, — per cent fat, -j-solids-not-fat; -|-milk,  — per cent fat, 

 — per cent solids-not-fat, etc.) and averaging the figures, the following 

 table results : 



*These figures are calculated on the basis that an increase in the 1 per cent fat is accompanied by 

 an increase of about 0.4 per cent solids-not-fat. 



The influence of inheritance in affecting the solids-not-fat in milk is 

 illustrated in the study of a single cow family. Cow No. 102 with a record 

 of 9390 pounds milk, 3.61 per cent fat, and 8.27 per cent solids-not-fat, was 

 the great granddam of two full sisters. No. 240 and No. 271, with records 

 of 10672 pounds milk, 3.81 per cent fat, and 8.82 per cent solids-not-fat; 

 and 10663 pounds milk, 3.63 per cent fat, and 8.40 per cent solids-not-fat, 

 respectively. The high solids-not-fat test (8.82 per cent) of cow 240 was 

 very likely due to the effect of sires B and L that both raised the solids-not- 

 fat content, whereas the low solids-not-fat test (8.40 per cent) of cow 271 

 reverts to the test of the great granddam (8.27 per cent) and the grand- 

 dam (8.40 per cent). The dam of 240 and 271 had a record of 8.75 per 

 cent solids-not-fat. 



The results with the sires and the cow family indicate that the three 

 factors, milk production, percentage butterfat, and percentage of solids-not- 



