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United States Department of Agriculture

Agricultural Research Service


item Spiers, D
item Eichen, P
item Robinson, E
item Matteri, Robert - Bob
item Byatt, J

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/26/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Recombinant bovine placental lactogen (rBPL) was administered daily to determine growth promotant activity of this compound as a function of ambient temperature. Sprague-Dawley female rats (100 d of age) were acclimated to either thermoneutral (TN; 21 deg) or heat-challenge (HC; 31 deg C) environments for 7 d. After this time, rats were injected ip with either rBPL (20 mg/day/kg BW) or sterile water for a 10-day period. Body weight and food consumption were recorded daily during the entire period. Measurement of resting metabolic rate and body temperatures occurred on the last injection day, followed one day later by determinations of fat free mass (FFM), total body water (TBW), and mass of selected organs. Change in body weight of rBPL-injected rats was greater than for controls (P<.001), with the increase over the first 9 days of injection being 18.5 versus -4.0 g (P<.001) for TN rats and 23.4 versus 6.9 (P<.001) for HC rats. Treatment twith rBPL and vehicle resulted in average daily gains of 2.41 and .95 g (P<.01), respectively. Daily food intake relative to body mass over this period was greater for rBPL-injected versus control TN rats (P<.02), but not different for HC rats. FFM and TBW relative to body mass were lower in HC rats compared to TN rats (P<.004), but not affected by rBPL treatment. In general, organ mass relative to body mass was not altered by rBPL treatment, but the heart was lighter in rBPL rats (P<.035). Likewise, metabolic rate decreased (P<.0001) and tail-skin temperature increased (P<.0001) from 21 to 31 deg C, but were not affected by rBPL treatment. These results show that treatment of adult rats with rBPL increased growth rate in both thermoneutral and heat-challenge conditions, with only slight indication of changes in feed intake and body composition.

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