388 ANIMAL BIOCHEMISTRY 



meat, milk, and eggs are rich in phosphate. Hence almost any human 

 diet contains enough and there is little concern over minimum daily 

 allowances. 



On the other hand, farm animals are not always so fortunate and 

 tentative daily allowances have been set for them. Values for the 

 different species and age groups are listed in the tables of the Ap- 

 pendix. Cattle should get from 3 to 20 g./day, depending on size, 

 with special increments during lactation. Rations for sheep should 

 contain 2.5 to 3.5 g. daily, increased to 5.0 g. for 150-lb. ewes in lacta- 

 tion. Swine requirements range from 5 to 10 g. daily with double 

 the intake during breeding and lactation. Recommended allowances 

 for chickens are from 0.60 to 0.75 per cent of the feed with about one- 

 third of this as inorganic phosphate. Turkeys need somewhat more 

 inorganic phosphate, 0.4 per cent of the ration, and a total of 0.75 to 

 1.0 per cent. 



As suggested earlier in connection with both calcium and vitamin 

 D, the minimum requirement for phosphate depends on other factors 

 in the diet. The vitamin aids in the utilization of both elements and 

 helps prevent deficiencies with borderline intakes of phosphate. How- 

 ever, an excess of Ca++ renders part of the ingested phosphate un- 

 available as the insoluble Ca3(P04)2. This condition is aggravated 

 when the diet tends to raise the pH of the intestine. Carnivores nor- 

 mally have more acidic digestive tracts than herbivores and are less 

 susceptible to phosphate deficiencies. The presence of sizable quan- 

 tities of other cations like Mg++ may also reduce the availability of 

 phosphate and raise the amount needed in the diet to compensate. 



Phosphate deficiency is the most widespread of any in livestock. It 

 occurs all over the world and has been reported in at least twenty 

 states of the United States. Common in cattle, it occurs to a lesser ex- 

 tent in sheep when foraging on plants that do not supply enough 

 phosphate. Soils may contain sufficient of the mineral for normal 

 plant growth but not enough to raise the concentration in certain 

 plants to the levels needed by animals. Minimal demands by animals 

 probably exceed those of plants because of large amounts in the 

 bones. Thus ruminants with their none too efficient absorption are 

 prone to phosphate deficiency even in the feedlot unless supplemen- 

 tary phosphate is added. Note the caution necessary (page 378) when 

 phosphate rock is used without removal of fluoride. 



The symptoms of phosphate deficiency are loss of appetite and crav- 

 ings for wood and bones, eaten instinctively in an attempt to over- 

 come the shortage. Emaciation becomes severe and is accompanied 

 by weakness, stiffness, and bone fragility with tendency toward numer- 



