Dose-response effects of recombinant bovine somatotropin (PosilacTM) on growth performance and body composition of two-year-old rainbow trout (Oncorhynchus mykiss)

Abstract

Two hundred rainbow trout (Oncorhynchus mykiss, mean weight 301.5 g) were allotted to four treatments with five replicates in a randomized block design to determine the dose-response effects of recombinant bovine somatotropin (rbST; Posilac) on growth performance and carcass composition. Treatments were sham-injected controls (S), 10 micrograms/g BW of rbST (L), 20 micrograms/g BW of rbST (M), and 30 micrograms/g BW of rbST (H). The tanks held 135 L; water flow = 15.1 L/min; temperature = 15 degrees C. The fish were maintained in a 12-h light:dark cycle and hand-fed twice daily. The fish received a single intraperitoneal (i.p.) injection on d 0 and were weighed on d 0, 14, 28, and 56. On d 56 the fish were killed. The whole body (WBW), eviscerated carcass (EC), viscera (VIS), and reproductive organ weights and the increase in average daily body length (ADL) were determined. Recombinant bST reduced (linear, P < .004) feed intake 17.6% from d 0 to 14 and improved ADG 44.8% from d 0 to 14 (linear, P < .001) and 8.1% from d 0 to 56 (linear, P < .022). Treated groups had improved (linear, P < .001) feed efficiencies for d 0 to 28. Treatment with rbST increased final weight (linear, P < .018) and length (linear, P < .001), decreased carcass dry matter (linear, P < .001) and fat (linear, P < .001), content, increased carcass ash (linear, P < .001) and tended to increase carcass protein (linear, P < .054) content. Recombinant bST increased WBW (linear, P < .018) and EC (linear, P < .003) but decreased (linear, P < .015) testes weight. Ovary weights, VIS and overall gonadosomatic index were unaffected (P > .05) by rbST. Recombinant bST was undetectable in serum samples taken on d 56 as determined by radioimmunoassay. Overall, the improved ADG, feed efficiency, body mass, and composition indicate that administration of rbST to rainbow trout may be an efficacious method of modulating growth in fish.

Effects of short-term growth hormone treatment on liver and muscle transcriptomes in rainbow trout (Oncorhynchus mykiss)

“…Previous experiments have shown that exogenous GH treatment and the production of GH transgenic fish result in a significant increase in overall growth rate in rainbow trout and other salmonids (21,39,52). In addition, studies have examined the effects of GH augmentation on aspects of physiology and gene expression in salmonids (3,4,26,44,57,66).…”

“…In the rainbow trout, a 6-wk recombinant bovine somatotropin (rbST) treatment significantly increased weight and length (21). Determinations of the underlying biological pathways enhancing growth in the salmonids after recombinant bovine GH (rbGH) treatment have been limited to individual gene expression studies (3,4,5,26) and measurements of metabolic parameters (21,28,29,42,34,57).…”

Comparative Aspects of GH and Metabolic Regulation in Lower Vertebrates

“…The increase in weight associated with growth in fish appears to be due to a combination of increased appetite [14, 15] and increased feed conversion [[14, 16, 17]; for review,see [18]]. In fish, both GH administration [19, 20] and GH transgenesis [21] result in increased growth that might be attributed to increased feeding and improved food assimilation [20, 22].…”

Effect of European seabass (Dicentrarchus labrax) fry source (Wild, NIOF and GAFRD K21) on its growth performance and physiology

“…Growth of post larvae were measured carefully as total length were to nearest 0.1 mm and total weight to nearest 0.001 mg to calculate total weight gain, average daily gain, specific growth rate in weight were according to Castell [14], Condition factor were according to Yildiz et al [15] and average daily gain or increase in length were according to Garber [16] and specific growth rate in length were according to Nour [17].…”