Níveis da bacitracina de zinco como melhorador do desempenho de frangos de corte

A utilização de antimicrobianos melhoradores de desempenho na criação de frangos de corte é uma prática comum na indústria avícola e, no Brasil, seu uso deve ser feito de acordo com os limites determinados pelo Ministério da Agricultura Pecuária e Abastecimento (MAPA).Objetivou-se com o presente trabalho determinar o efeito da utilização da bacitracina de zinco, dentro dos níveis recomendados pelo Ministério da Agricultura Pecuária e Abastecimento (MAPA), em dietas para frangos de corte sobre o desempenho de aves e criadas de 1 a 42 dias de idade. Utilizou-se o delineamento inteiramente casualizado, com 5 tratamentos, distribuídos em 10 repetições de 25 pintos machos de corte da linhagem Cobb 500®, totalizando 1250 aves. Os tratamentos experimentais foram constituídos de cinco níveis de inclusão de bacitracina de zinco (0, 10, 25, 40 e 55ppm). As variáveis analisadas foram consumo de ração, ganho de peso, conversão alimentar e avaliação econômica das dietas. Para o período total de criação, avaliou-se também a viabilidade dos frangos de corte. A bacitracina de zinco foi eficiente como beneficiador do desempenho de frangos de corte criados no período de 1 a 21, 1 a 35 e 1 a 42 dias. Para o período de 1 a 21 dias, o uso de 55 e 29,3ppm de bacitracina de zinco resultou em menor consumo de ração e maior ganho de peso, respectivamente. No geral, a melhor conversão alimentar foi obtida quando se adicionou 55ppm de bacitracina de zinco na ração de frangos de corte

Supplementation of fungal and/or bacterial phytase in broiler diets formulated with reduced phosphorus level and different calcium contents

The objective of the current study was to evaluate the effects of three calcium:available phosphorus (Ca:aP) ratios and different supplementation with phytases from different origins on performance and ash, Ca, and P contents in the tibia of broilers. A total of 900 male broilers (22 to 35 days old) were fed ten dietary treatments in a completely randomized design. A 3 × 3 + 1 factorial scheme was used, corresponding to three Ca:aP ratios (4.5:1.0, 6.0:1.0, and 7.5:1.0) and three different supplementations with phytases from different origins (isolated or combined supplementation with bacterial and fungal phytase), plus a control diet. Regardless of the dietary Ca:aP ratio, the isolated use of bacterial phytase provided better feed conversion than the fungal phytase but did not differ from combined supplementation with bacterial and fungal phytase. However, regardless of the supplemented phytase, the 7.5:1.0 Ca:aP ratio decreased the feed conversion. Best results for bone P deposition were observed using diets containing the 4.5:1.0 Ca:aP and fungal phytase or the 4.5:1 and 6.0:1 Ca:aP ratios using the bacterial phytase. In general, when the parameters of feed conversion, bone ash, and P content in tibia are considered together, diets containing a 4.5:1.0 or 6.0:1.0 Ca:aP ratio and 1,500 FTU kg−1 bacterial phytase, or a 4.5:1.0 Ca:aP ratio using fungal phytase and only 1.0 g kg−1 available phosphorus provide better result

Influence of heat stress, sex and genetic groups on reference genes stability in muscle tissue of chicken

<div><p>Quantitative RT-PCR is an important technique for assessing gene expression. However, a proper normalization of reference genes prior to expression analyses of target genes is necessary. The best normalizer is that gene which remains stable in all samples from different treatments. The aim of this study was to identify stable reference genes for normalization of target genes in muscle tissue from three genetically divergent chickens groups (Peloco, Cobb 500^® and Caneluda) under environmental (heat stress and comfort) and sex influence. Expressions of ten reference genes were tested for stability in breast muscular tissue (<i>Pectoralis major</i> muscle). Samples were obtained from 36 males and females of two backyard breeds (Caneluda and Peloco) and one commercial line (Cobb 500^®) under two environments. The heat stress and comfort temperature were 39 and 23°C, respectively. Animals were housed in the Animal Science Department at <i>Universidade Estadual do Sudoeste da Bahia</i>. We analyzed the expression data by four statistical tools (SLqPCR, NormFinder, Bestkeeper and Comparative CT). According to these tools, genes stability varied according to sex, genetic group and environment, however, some genes remained stable in all analyzes. There was no difference between the most stable genes for sex effect, being <i>MRPS27</i> more stable for both males and females. In general, <i>MRPS27</i> was the most stable gene. Within the three genetic groups, the most stable genes were <i>RPL5</i>, <i>HMBS</i> and <i>EEF1</i> to Cobb 500^®, Peloco and Caneluda, respectively. Within the environment, the most stable gene under comfort and heat stress conditions was <i>HMBS</i> and <i>MRPS27</i>, respectively. BestKeeper and Comparative Ct were less correlated (28%) and SLqPCR and NormFinder were the most correlated (98%). <i>MRPS27</i>, <i>RPL5</i> and <i>MRPS30</i> genes were considered stable according the overall ranking and can be used as normalizer of relative expression of target genes in muscle tissue of chickens under heat stress.</p></div

Initial feed used in the production of chicks up to 30 days of age (ROSTAGNO, GOMES, 2011).

<p>Initial feed used in the production of chicks up to 30 days of age (ROSTAGNO, GOMES, 2011).</p

Descriptive statistics of expression levels of reference genes for chickens obtained by BestKeeper (n = 36).

<p>Descriptive statistics of expression levels of reference genes for chickens obtained by BestKeeper (n = 36).</p

ANOVA analysis of Ct values of genetic group, sex and environment effects among previous chosen genes.

<p>ANOVA analysis of Ct values of genetic group, sex and environment effects among previous chosen genes.</p

Ranking with stability values for each treatment (genetic group, sex, and environment) in chicken obtained from BestKeeper tool.

<p>Values into the parenthesis refer to ranking by Bestkeeper to each treatment. Values on the last column refer to the ranking position by RankAggreg package among all the treatments.</p

Overall ranking of reference genes in chickens obtained by different tools (SLqPCR, NormFinder, Bestkeeper and Comparative Ct) and ranked by RankAggreg package according to each treatment (genetic groups, environment and sex).

<p>Overall ranking of reference genes in chickens obtained by different tools (SLqPCR, NormFinder, Bestkeeper and Comparative Ct) and ranked by RankAggreg package according to each treatment (genetic groups, environment and sex).</p