Effect of milk replacer and solid feed on water balance, glomerular filtration rate, and reabsorption of water from renal tubules in suckling calves
1998
Matsunaga, M. (Azabu Univ., Sagamihara, Kanagawa (Japan). Faculty of Veterinary Medicine) | Tsuyama, T. | Iriki, T. | Funaba, M. | Kagiyama, K. | Wada, Y. | Honjo, T. | Abe, M.
Two trials were conducted using Holstein bull calves purchased from a market at wk of age. In trial a, 20 calves were used to examine the effect on water balance and fecal moisture content during wk 2 of daily amounts of milk replacer (500 vs. 200 g/d) with or without free access to solid feed (timothy hay and concentrate) from wk 1. In trial 2, the other 20 calves were used to examine the effect of the similar treatments on glomerular filtration rate (GFR) and reabsorption of water (RAOW) from renal tubules during wk 2. Both trials were conducted in a factorial arrangement by dividing 20 calves into 4 groups of 5 calves each. When water balance was determined in trial 1, difference of the sum of urine volume and fecal water excretion from the sum of water used to prepare liquid milk replacer, and moisture originally contained in dry milk replacer and ingested solid feed was designated as apparent water retention(AWR), because metabolic water and evaporation from the lung and body surface were not considered. Ingestion of solid feed and a larger amount of milk replacer resulted in a decrease in urine volume and an increase in fecal water excretion, independent of the amounts of milk replacer. Fecal moisture content also increased from 66-67% in calves received no solid feed to 76-77% in calves given solid freed from wk 1, independent of daily amounts of milk replacer. However, AWR was increased not only by the ingestion of solid feed but also by the larger amount of milk replacer. Results of trial 2 suggested that decease in urine volume resulting from ingestion of solid feed was due to enhanced RAOW which occurred in spite of an increase in GFR
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