CAROTENOIDS 



carotehoid levels in healthy beasts, i « i- 1 • » but have no effect on the 

 carotenoid content of the early mammary secretions. ^3» There is ap- 

 parently a factor in raw soya bean oil which has the same effect as 

 vitamin A, for Squibb, Cannon and Allen ^ * * found that supplements 

 of this oil decreased the carotene levels of both the blood and milk 

 of cattle. The carotene levels are also depressed when the diet contains 

 30 per cent, of ground soya beans. ^ '"^ 



Feeding of tocopherols tend to neutralize the depressant action of 

 vitamin A. ^"^ Sulphonamide therapy has no effect on the carotene 

 plasma levels of cows^** and neither have changes in the ambient 

 temperature of the animals. ^ ' ' 



The relationship between carotene metabolism and the thyroid 

 gland is discussed in Chapter XI ; information on the effect of thyro- 

 globulin and iodinated casein, which are used to increase milk yield, 

 on the carotene level in blood and milk, ^ « »' ^ « ^a jg somewhat con- 

 tradictory. 



Other Organs 



Carotenoids, preferentially p-carotene, accumulate in a number of 

 other body organs in cattle, viz. body fat,*'^.i«».i'« ovaries, I'l.^'* 

 testes, 2 «. 1 ' 3 adrenals, i « ». i ' *- 1 ^ e corpus luteum, 8. i ? 2, i ? 7- 1 ? 9 corpus 

 rubrum,i«« thymus, i'« liver, ^ '*• ^ « ^ retina, ^ « 2- 1 s 4 the pigment 

 epithelium and iris,i«* pituitary, 1 ««• 1 « « bile,i«'.i«» muscle, ^'^ 

 kidney i»*'^'*'^'* and placenta. '• ^ <> The spleen appears to contain 

 no carotenoids. 1 «. 1 ^ 1 T^g reason for the accumulation of carotenes 

 rather than xanthophylls in all these organs as well as in the blood 

 and milk is probably due to the failure to absorb xanthophylls 

 from the intestinal tract, for these greatly preponderate over carotenes 

 in cows' faeces ; ^ ' ^ even so the faeces of cows feeding on green 

 pasture contain over 100 (Jtg./g. of carotene. ^ » " 



The carotene deposited in the body fat of cattle can accumulate with 

 age to a considerable extent, as witnessed by the colour of the fat of a 

 particularly tough week-end joint. Zechmeister and Tuzson^'** 

 isolated 2 mg. of crystalline carotene per 2 kg. of cow fat. The claim 

 that cow fat contains considerably more carotene than does bull fat*^ 

 has not yet been confirmed, but it is possible for there may be analogous 

 sexual differentiation in plasma carotenoid levels, 1 3 3. i « 1 although, as 

 mentioned previously {see p. 238), this may be partly due to different 

 dietary habits. 



The amount of carotene present in the corpus luteum and corpus 

 rubrum is considerable and can reach 6 and 120 mg./lOO g. for these 

 two organs respectively. No other mammalian tissue contains such a 



244 



