Studies of urinary and blood nitrogen curves after feeding in the dog

Abstract

The following studies were designed to show the hourly variations in the normal dog of the total non-protein nitrogen of the blood compared with the output of urine and of the nitrogen in the urine and the effect upon these of various diets and of variations in the water intake.

Eight dogs have been placed on a diet consisting of meat, lard, sugar, sodium chloride, bone ash and water adequate in calories and containing about 0.4 gm. of nitrogen per kilo of body weight. On the sixth day the ration was varied to suit the study; in dogs 2 to 6 being richer in nitrogen, while in dogs 7, 8 and 9 no food was given on the days of the study. The water intake was varied as shown in the table. On the day of the study the animals were catheterized at intervals of two to four hours and at the time of each catheterization 5 c.c. of blood was taken from the jugular vein for estimation of the non-protein nitrogen by Folin's method. The urinary nitrogen was estimated by Kjeldahl. The results are shown in the table.

Conclusions.—The daily variation in the non-protein blood nitrogen of the normal dog receiving a diet containing 0.4 gm. of nitrogen per kilo is about g milligrams, the maximum being reached about two hours after feeding with a return to the original level in about 10 to 14 hours. By feeding excessive quantities of meat the non-protein blood nitrogen may be increased 25 to 40 milligrams in 6 to 8 hours and the original level is usually not reached even at the end of 24 hrs. In one animal (Dog 4) the blood nitrogen did not reach its maximum until 14 hours after feeding; the urinary nitrogen exhibiting a parallel gradual rise; this is probably only to be explained on the basis of slow absorption from the gastrointestinal tract.