Stable isotopes to study sulfur amino acid utilization in broilers.

Nutritionists have been discussing whether the dietary supplementation of cyst(e)ine is required as a part of the dietary methionine (Met) in the total sulfur amino acid (TSAA) requirement to achieve optimum performance in broilers. Part of Met is converted to cysteine (Cys) to meet the Cys requirement, especially for feather growth. The TSAA requirement has been determined by using graded levels of free Met in the diet, without supplementation of free cyst(e)ine. It has also been argued that the Met to Cys ratio (Met : Cys) changes with age and even with different Met sources. The objective of this study was to evaluate the two sources of Met, while determining the proportion of Met and Cys in total dietary TSAA that optimize the performance of broilers. A performance assay was carried out in a factorial arrangement (5 × 2) using 1080 broilers from 42 to 56 days of age fed diets having different dietary proportions of Met and Cys (44 : 56, 46 : 54, 48 : 52, 50 : 50 or 52 : 48) while maintaining the same dietary TSAA in the diets. Two synthetic Met sources (dl-Met or l-Met) were used for each of the diets with different dietary Met : Cys ratios. Twenty-one broilers of the same age were fed the diets 44 : 56, 48 : 52 and 52 : 48 by supplementing the diet with L-(15N) Met or L-(15N2) Cystine to study the metabolism of TSAA. No differences were observed between Met sources for feed intake, BW gain and feed conversion ratio (FCR; P > 0.05); however, FCR was numerically improved at 50 : 50 Met : Cys. Regarding TSAA utilization, the conversion of Met to Cys increased with increase in Met : Cys ratios, but the concentration of Met intermediates decreased. Broiler chickens responded to different dietary proportions of sulfur amino acids by altering their sulfur amino acid metabolism, and diets containing 50 : 50 Met : Cys is recommended for broilers of age 42 to 56 days.

A new species of Anchoviella (Clupeiformes: Engraulidae) from the western Amazon River in Peru, with comments on congeners in the Peruvian Amazon River.

Anchoviella hernanni sp. nov. is described from the upper Amazon River basin, in tributaries of the Marañon, Ucayali and Madre de Dios river drainages that drain the Peruvian Andes. The new taxon can be distinguished from all congeners except Anchoviella jamesi, Anchoviella manamensis and Anchoviella perezi, by having 12-15 gill rakers in the lower branch of the first gill arch (v·16-35) and from those species by the distance between verticals through the posterior margin of the orbit to the posterior margin of the upper jaw 9·5-14·8% head length; LH (v. up to 6·0% LH ). An updated identification key of all freshwater species of Anchoviella and morphological comparisons between all species of the genus occurring in Peru are provided.

Teleocichla preta, a new species of cichlid from the Rio Xingu Basin in Brazil (Teleostei: Cichlidae).

Teleocichla preta nov. sp. inhabits the rapids along the Rio Xingu and lower portion of the Rio Iriri. It is the largest species in the genus, reaching 121·3 mm standard length (LS ) while others do not reach more than 87·8 mm LS . Teleocichla preta is distinguished from all other species of Teleocichla by the unique blackish (in live specimens) or dark brown (preserved specimens) overall colouration of the body, which masks the faint vertical bars or zig-zag pattern of blotches on the flanks. Teleocichla preta also has a deeper body and a deep laterally compressed caudal peduncle, unlike any other congener, as well as a stout lower pharyngeal tooth plate bearing molariform teeth on its median area.