358 FEEDS AND FEEDING 



therms of net energy. As these requirements are stated in different 

 terms, they can be compared only indirectly. It will be found that when 

 legume hay, or a combination of legume hay and such feeds as corn 

 stover or straw, are taken for a maintenance ration, about the same 

 amount of feed will be needed to meet the requirements for the net- 

 energy standards as for the standards based on total digestible nutrients. 

 On the other hand, if feeds higher in net energy, such as either good corn 

 silage or else concentrates, are used as part of the maintenance ration, 

 less feed will be needed to meet the net energy requirements ex- 

 pressed in therms than to satisfy the standards based on total digestible 

 nutrients. 



The most extensive investigations which have been conducted to de- 

 termine the maintenance requirements of dairy cows are those of Hills 

 and his colleagues at the Vermont Station. 50 In these trials, which have 

 been carried on from 1907 to 1920, a total of 20 cows have been fed while 

 dry and barren for periods of 391 to 2,701 days. Ten of these cows 

 were fed less than the maintenance requirements as given in the stand- 

 ards based on digestible nutrients, some being fed 40 per ct. less. The 

 cows, however, suffered in no wise, but, instead, gained in weight. These 

 data seem to indicate that these standards prescribe more feed than is 

 actually required for the mere body maintenance of a dry dairy cow 

 when mature and not pregnant. 



Data secured from 14 cows in these trials indicate that the building 

 of the fetus when a cow is pregnant makes relatively little additional 

 draft for non-nitrogenous nutrients, but may require on the average 

 0.05 to 0.10 Ib. daily of digestible protein, spread over the entire gesta- 

 tion period, in addition to the amount needed for mere maintenance. 

 This need for additional protein is naturally greatest during the last 

 third of gestation, when the development of the fetus is most rapid. 



The requirements for the development of the fetus have also been 

 studied by Eckles at the Missouri Station. 51 He fed 2 cows during their 

 entire gestation periods on rations which had previously been only suf- 

 ficient to maintain their weight when not pregnant and not producing 

 milk. The cows developed normal calves, and their average weight was 

 greater after calving than before the trial started. Similar results were 

 secured in another trial. Eckles believes these results are due to the rela- 

 tively small amount of dry matter in the fetus, which has already been 

 discussed (121), and also probably to the cows requiring less feed for 

 mere body maintenance when pregnant, owing to their being quieter. 



Hills believes from his investigation that a ration which furnishes suf- 

 ficient nutrients to meet the requirements for maintenance and for the 

 production of the amount of milk yielded, will suffice for the first two- 

 thirds of the gestation period. For the last third of the period it should 

 be sufficient to add to the nutrients required for maintenance and for 



"Information to the authors. 

 61 Mo. Res. Bui. 26. 



