168 VITAMINS A AND CAROTENES 



TABLE XIX 



Estimates of the Vitamin A Requirement of Cattle 



I.U. fed per kilogram 

 of body weiglit per 



day Criterion used References 



32 Growth, nyctalopia 23 



44 Growth 24 



43-55 Nyctalopia 2 



60 Growth 25 



64 Growth 23 



83 Fertility in bulls 26 



100 Protection for winter conditions 24 



110 Spinal fluid pressure in Holstein calves 27 



115 Spinal fluid pressure in Jersey calves 27 



125 Spinal fluid pressure in Guernsey calves 27 



125 Blood level in Holsteins 28 



165 Reproduction 29 



210 Blood level in Guernseys 28 



220 Exigencies of normal conditions 27 



250 Growth, liver storage 23 



220 NRC recommendation 30, 31 



TABLE XX 

 Estimates of the Vitamin A Requirement of Chickens 



I.U. fed per 

 pound of diet Criterion used References 



Starting and growing chicks 



700 Growth 33 



1100 Growth, survival, liver storage 34 



1000 Growth 35 



1200 Growth 36 



1400 Growth 37 



1400 Growth, general health 38 



1600 Growth, liver storage 39 



1900 Liver storage 40 



2000 NRC recommendation 41 



Laying and breeding hens 



2000 Mortality, egg production, hatchability 42 



2000 Hatchability, chick survival 43 



2100 Egg production, hatchability 33 



2300 Maintenance of laying hens 35 



3200 Maintenance of l>reeding h(Mis 35 



4200 Liver storage, egg jjroductioii, survival, halc'hal)ililv 44 



4200 Kgg production, fertility, hatch;il)ility 38 



3300 NRC recommendation 41 



