Supplements of sodium bicarbonate (NaHCO3) added to the diet or drinking water of finishing broilers (3-6 weeks of age) improved food intake, live weight gain and food efficiency at high (30�C), but not at moderate (2l�C), temperatures. The improved performance was not related to increases in amino acid digestibilities which were reduced in birds kept at 30�C. Increased consumption of drinking water appears to be a major prerequisite for the improved performance at high temperatures. The methionine : total sulfur amino acid (TSAA) ratio of the diets also influenced broiler performance at 30�C with ratios of 0.43 and 0.55 giving superior growth and food conversion to a ratio of 0.62. The intake of drinking water and the water : food intake ratio were significantly reduced at the dietary methionine : TSAA ratio of 0.62, the effect being significant when the drinking water contained NaHCO3.

No abstract

The methionine requirements of 3-6-week-old broilers kept at a constant 30�C or at diurnally cycling temperatures of 25-35�C were reduced compared with broilers kept at 21�C. The methionine requirements varied from 0.29 g/MJ of metabolizable energy (ME) at 2 1�C to 0.26 g/MJ of ME at 25-35�C to 0.22 g/MJ of ME at 30�C with total sulfur amino acid requirements of between 0.51 and 0.55 g/MJ of ME. The estimate at 21�C is similar to recommendations made by others for moderate temperatures. Differences in response to DL-methionine and methionine hydroxy analogue free acid were small.

In teleosts fish, secretion of GH is regulated by several hypothalamic factors that are influenced by the physiological state of the animal. There is an interaction between immune and endocrine systems through hormones and cytokines. GH in fish is involved in many physiological processes that are not overtly growth related, such as saltwater osmoregulation, antifreeze synthesis, and the regulation of sexual maturation and immune functions. This study was conducted to characterize a decapeptide compound A233 (GKFDLSPEHQ) designed by molecular modeling to evaluate its function as a GH secretagogue (GHS). In pituitary cell culture, the peptide A233 induces GH secretion and it is also able to increase superoxide production in tilapia head-kidney leukocyte cultures. This effect is blocked by preincubation with the GHS receptor antagonist [D-Lys 3 ]-GHRP6. Immunoneutralization of GH by addition of anti-tilapia GH monoclonal antibody blocked the stimulatory effect of A233 on superoxide production. These experiments propose a GH-mediated mechanism for the action of A233. The in vivo biological action of the decapeptide was also demonstrated for growth stimulation in goldfish and tilapia larvae (P!0 . 001). Superoxide dismutase levels, antiprotease activity, and lectin titer were enhanced in tilapia larvae treated with this novel molecule. The decapeptide A233 designed by molecular modeling is able to function as a GHS in teleosts and enhance parameters of the innate immune system in the fish larvae.

To date, many technologies have been developed to increase efficiency in aquaculture, but very few successful biotechnology molecules have arrived on the market. In this context, marine biotechnology has an opportunity to develop products to improve the output of fish in aquaculture. Published in vivo studies on the action of the pituitary adenylate cyclase-activating polypeptide (PACAP) in fish are scarce. Recently, our group, for the first time, demonstrated the biological role of this neuropeptide administrated by immersion baths in the growth and development of larval fish. In this work, we have evaluated the effects of recombinant Clarias gariepinus PACAP administration by intraperitoneal injection on growth performance and feeding behavior in juvenile fish. Our results showed the physiological role of this peptide for growth control in fish, including the juvenile stage, and confirm that its biological functions are well conserved in fish, since C. gariepinus PACAP stimulated growth in juvenile tilapia Oreochromis niloticus. In addition, we have observed that the growth-promoting effect of PACAP in juvenile tilapia was correlated with higher GH concentration in serum. With regard to the neuroendocrine regulation of growth control by PACAP, it was demonstrated that PACAP stimulates food intake in juvenile tilapia. In general, PACAP appears to act in the regulation of the growth control in juvenile fish. These findings propose that PACAP is a prominent target with the potential to stimulate fish growth in aquaculture.