GENERAL PROBLEMS IN DAIRY HUSBANDRY 353 



maintain her weight when dry. When the lactation period has reached 

 a certain stage, even moderate underfeeding causes a decline in milk 

 flow. Underfeeding following a period of liberal feeding causes a marked 

 increase in the percentage of fat in the milk, especially when the cow 

 has a surplus store of fat in her body. Underfeeding produces marked 

 effects on the chemical and physical properties of the butter fat, which 

 may or may not change the melting point. Ragsdale and Swett of 

 the Missouri Station 36 report that when the ration of cows during the 

 first half of the lactation period was reduced one-half, the percentage 

 of fat was temporarily increased, the high point occurring either the 

 second or third day after the reduction was made. As soon as the 

 cows were put back on full feed the fat content of the milk fell and 

 went even below normal. The amount of milk varied almost directly 

 with the amount of feed given. 



Eckles and Palmer found that the most pronounced effect of over- 

 feeding; i.e., feeding a more liberal ration than is required for the pro- 

 duction of a normal yield of milk, was that it caused the cow to gain in 

 weight. Only to a limited extent was the excess food used for the pro- 

 duction of milk and even under the most favorable conditions the ani- 

 mals seemed unable to increase their milk flow beyond the fixed maximum 

 inherited by the individual. Overfeeding will sometimes cause a re- 

 covery of the milk flow lost because of previous poor nutrition, but this 

 recovery is only partial even under the best conditions. 



563. Effect of temperature, weather, and turning to pasture. The tend- 

 ency is for cows of all breeds to give richer milk when the temperature 

 falls and poorer milk as it rises, and so they generally yield slightly poorer 

 milk in summer than in winter. This was shown in 5 trials by Hills at 

 the Vermont Station, 37 covering practically the entire year, and 

 including varying conditions of pasture, summer soiling, and 

 winter barn feeding. The same conclusion was reached by Eckles, 38 

 on studying the records for 240 lactation periods of cows in the herds 

 at the Missouri and Iowa Stations, by White and Judkins, 39 on com- 

 piling the records for the herd at the Connecticut (Storrs) Station, and 

 by Ragsdale and Turner of the Missouri Station 40 on studying the 

 records of over 3,000 Guernsey cows which had made the Advanced 

 Registry, and also records of Jerseys and Holsteins at the Missouri Sta- 

 tion. No matter when a cow freshens, the tendency is for her to give 

 richer milk in the winter months and poorer milk in summer, especially 

 during June and July. White and Judkins found that the milk con- 

 tained on the average 0.31 per ct. less fat and 0.56 per ct. less solids-not- 

 fat in the summer than in the cold months. In any particular cow this 

 tendency may be offset by the usual rise in percentage of fat during the 

 last 2 or 3 months of lactation. 



M Mo. Bui. 179, pp. 22-23. "Vt. Rpt. 1907. 



^Milchwirtschaftliches Zentralblatt, 5, 1909, pp. 488-502. 

 'Conn. (Storrs) Bui. 94. ^Information to the authors. 



