Assessment of biochemical mechanisms of compensatory growth in channel catfish and integration of nutritional strategies for increasing the efficiency of production

A series of experiments was undertaken to: (1) identify a feeding strategy to induce compensatory growth in channel catfish (Ictalurus punctatus), (2) investigate potential mechanisms by which the compensatory growth phenomenon occurs, and (3) determine if diet formulations could be altered to enhance the compensatory growth phase. One experiment delineated alterations in body composition in response to periods of feed deprivation and refeeding. Hepatosomatic index decreased rapidly at onset of feed deprivation (within 3 days), stabilized at 5 days and was restored rapidly in response to realimentation. Tissue composition also changed in response to feed deprivation as nutrients were mobilized from liver and muscle. Liver and muscle composition returned to normal shortly after realimentation. Compensatory growth and enhanced feed efficiency were observed upon realimentation of fish deprived of feed for 4 weeks.;A second experiment addressed the effects of short-term feed deprivation on growth and thyroid hormone status. Restricted feeding had a pronounced effect in that fish lost weight in 3 days. Thyroxine and triiodothyronine were depressed with feed restriction and rose to or above control levels following realimentation. The assessed regimes were incapable of inducing a compensatory growth phase, but thyroid hormones appeared to respond rapidly to feed restriction and potentially overcompensate following realimentation.;A third experiment addressed effects of elevated dietary protein, energy, and indispensable amino acid supplementation on compensatory gain. Elevated protein (37% of diet) and digestible energy (3.6 kcal/g) singularly or in combination did improve growth of fish compared to lower levels (32% protein and 3.0 kcal/g). However, neither elevated dietary protein nor energy levels had any added benefit to the period of compensatory gain when induced by feed deprivation.;A final study was conducted to assess alterations in protein synthesis rates of fish in response to refeeding after feed deprivation. Although significant alterations were observed in RNA and protein content of muscle tissue, protein synthesis rates were not altered in support of the compensatory growth phase.;In conclusion, channel catfish can exhibit compensatory growth in response to a period of feed deprivation. The mechanism behind this phenomenon appears to be hormonally driven for improving growth rates as well as feed efficiency.