Pigeons preferences

The properties of 7a-hydroxylase from pigeon liver microsomes305 and from rat liver306,307 have been further described, and new assay methods are available.308,309 Free cholesterol, rather than a cholesteryl ester, was the preferred substrate for the enzyme from rat liver microsomes,310 and the substrate pool for the hydroxylase was about one third of the total amount of cholesterol present in the microsomal preparation.309 Cholesterol 7a-hydroxylase activity is more sensitive to thyroid function than are the activities of the enzymes responsible for cholesterol synthesis,311 and (22f )-22-aminocholesterol, although having no effect on serum or liver cholesterol levels in rats, drastically reduced 7a-hydroxylase activity.312... 

The animal assays are hardly ever used, as they are time consuming (6-8 weeks) and poorly reproducible. Experimental animals include rats, pigeons and chickens, although rats are preferable (Caster and Meadows 1980). The material being tested enables the measurement of the curative elfect of a food source on rats that have been made thiamine-deficient and comparing it with the curative elfect of pure synthetic thiamine hydrochloride. 

Wenzel (62) cautions researchers that domesticated and laboratory animals (albino rats, pigeons, and chickens) may be much less sensitive to taste and odor stimuli than are wild mammals and birds. For example, domestic chickens are able to compensate for reduced caloric content in their diet by drinking larger quantities of 10% sucrose in water solution. Normally, however, chickens are indifferent to sucrose. Kare and Mailer ( 2) found, on the other hand, that Red Jungle fowl tend to prefer sucrose solutions at all times and appear to be superior to the domestic chicken in caloric regulation. Likewise, there is some evidence ( that caloric regulation in wild rodents is usually superior to that demonstrated by laboratory rats. 

Some of the discrepancies found for preference behavior of the same general species (e.g., chickens, quail, pigeons) could be a function of different methods of measuring preference. Gentile (85 ), for example, found that chickens preferred certain concentrations of sucrose and glucose (1-5%) when brief-exposure (< 3 minutes) preference tests are used. Gentile believes that the Kare and Medway (8 ) preference data for carbohydrates reflect not only taste but also postingestional factors. 

Figure 6. Instrumental test apparatus for studying preference of pigeons...

Each data point represents a preference ratio which our hypothetical pigeon would produce in choosing between foods which differ in quantitative or qualitative ways. 

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