Sex proportion as a covariate increases the statistical test power in growth performance based experiments using as-hatched broilers.

The availability of sexed day-old broiler chicks is becoming an issue as feather sexing is no longer possible. This has great implications for broiler researchers as the use of randomly distributed mixed-sex birds may result in a greater between-pen variation and thus less statistical power than the use of single-sex birds. The objective of this study was to evaluate the effect of including sex proportion as a covariate in an analysis of covariance (ANCOVA) on the statistical power compared to analysis of variance (ANOVA) where sex was not considered. The statistical parameters examined include mean square error (MSE), the F-statistic, model fit, model significance and observed power. A total of 4 separate experiments that used mixed-sex broilers with unequal numbers of male and female birds per pen were conducted during which performance of the birds was measured. The male % in each pen was recorded during each experiment and corrected for mortality. The performance results were analysed by ANOVA and the statistical parameters were then compared to ANCOVA where sex proportion was included as a covariate. The results showed that a set of assumptions first needed to be met to run ANCOVA. In addition, if the ANOVA results show a high level of model significance and power, then ANCOVA may not be necessary. In other circumstances where the assumptions are met and model significance and observed power are low, the inclusion of sex proportion as a covariate in the analysis will help to reduce MSE, increase the F-statistic value and improve the model significance, model fit and observed power. Therefore, it is suggested that sex proportion should be considered as a covariate in ANCOVA to improve statistical power in nutritional experiments when male and female broilers are unequally and randomly distributed in pens.

Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase.

An experiment was conducted to explore the effects of digestible amino acid (dAA) concentrations and supplemental protease on live performance and energy partitioning in broilers. Ross 308 male broilers (n = 288) were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age. Dietary treatments consisted of a 2 × 2 factorial arrangement with dAA concentrations (standard and reduced [34 g/kg below standard]) and supplemental protease (without or with) as the main factors. At 1, 15, 28, and 35 d of age, feed and broilers were weighed to determine live performance. From 20 to 23 d of age, a total of 32 birds (2 birds/chamber, 4 replicates) were placed in closed-calorimeter chambers to determine respiratory exchange (heat production, HP), apparent metabolisable energy (AME), retained energy (RE), and net energy (NE). From 29 to 35 d of age, supplemental protease in the reduced-dAA diet decreased broiler feed conversion ratio (FCR) by 5.6 points, whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points. The indirect calorimetry assay revealed that supplemental protease decreased (P < 0.05) the heat increment of feed (HIF) by 0.22 MJ/kg. Also, from 20 to 23 d of age, broilers offered the reduced-dAA diet with supplemental protease had a higher daily body weight gain (BWG) (+10.4%), N intake (+7.1%), and N retention (+8.2%) than those offered the standard-dAA with supplemental protease. Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6% higher AME-to-crude protein (CP) ratio than those offered other treatments. Protease supplementation in the standard- and reduced-dAA diets resulted in 2.7% and 5.6% lower AME intake-to-N retention ratios, respectively, compared with the unsupplemented controls. Reduced-dAA increased (P < 0.05) AME intake (+4.8%), RE (+9.8%), NE intake (+5.8%), NE intake-to-CP ratio (+3.0%), and RE fat-to-RE ratio (+8.6%). Protease supplementation increased (P < 0.05) respiratory quotient (+1.2%) and N retention-to-N intake ratio (+2.2%), NE-to-AME ratio (+1.9%), and reduced HP (-3.6%), heat increment (-7.4%), and NE intake-to-N retention (-2.5%). In conclusion, protease positively affected FCR and energy partitioning in broilers; responses were most apparent in diets with reduced-dAA concentrations.

Detection and Quantification of Clostridium perfringens and Eimeria spp. in Poultry Dust Using Real-Time PCR Under Experimental and Field Conditions.

Infection of poultry with Eimeria spp., the causative agent of coccidiosis, can predispose birds to necrotic enteritis (NE) caused by netB gene-positive strains of Clostridium perfringens. The detection of Eimeria spp., C. perfringens, and netB were examined in settled dust from broiler flocks under experimental and field conditions. Dust samples were collected from settle plates twice weekly from two experimental flocks inoculated with three species of pathogenic Eimeria in 9-day-old chicks, followed by netB gene-positive C. perfringens 5 days later to produce subclinical and clinical NE. A noninoculated flock was sampled weekly from day 0 and served as a control flock. An additional 227 dust samples from commercial broiler flocks were collected at the end-of-batch (6-7 wk of age; one scraped dust sample per flock). In the NE-subclinical and NE-clinical flocks, high levels of Eimeria spp. and C. perfringens were detected after inoculation followed by a gradual decline over time. In the control flock, C. perfringens and netB were detected at low levels. No significant effect of sampling location was evident on Eimeria spp., C. perfringens, and netB load within poultry houses. These results provide evidence that Eimeria spp., C. perfringens, and netB gene copies can be readily measured in poultry dust samples collected in settle plates and may provide an alternative sampling method for monitoring flock coccidiosis and NE status. Further studies are required to assess the utility for such a test in commercial flocks.

Artículo regular­Detección y cuantificación de Clostridium perfringens y Eimeria spp. en polvo de instalaciones avícolas mediante PCR en tiempo real bajo condiciones experimentales y de campo. La infección de aves comerciales con Eimeria spp., el agente causante de la coccidiosis, puede predisponer a las aves a enteritis necrótica (NE) causada por cepas de Clostridium perfringens positivas a la presencia del gene netB. La detección de Eimeria spp., C. perfringens y del gene netB se examinó en el polvo sedimentado de parvadas de pollos de engorde bajo condiciones experimentales y de campo. Se recolectaron muestras de polvo por sedimentación en placa dos veces por semana de dos parvadas experimentales inoculadas con tres especies de Eimeria patógena en pollitos de nueve días, seguidas de C. perfringens positiva al gene netB cinco días después para producir enteritis necrótica subclínica y clínica. Una parvada no inoculada se muestreó semanalmente desde el día cero y sirvió como parvada control. Se recolectaron 227 muestras adicionales de polvo de parvadas de pollos de engorde comerciales al final del lote (6 a 7 semanas de edad; una muestra de polvo por raspado por parvada). En las parvadas con enteritis necrótica subclínica y clínica, se detectaron niveles altos de Eimeria spp. y de C. perfringens después de la inoculación seguida de una disminución gradual con el tiempo. En la parvada control, C. perfringens y el gene netB se detectaron en niveles bajos. No fue evidente ningún efecto significativo de la ubicación del muestreo sobre la carga de Eimeria spp., C. perfringens y del gene netB dentro de las casetas. Estos resultados proporcionan evidencia de que las copias genéticas de Eimeria spp., C. perfringens y del gene y netB se pueden medir fácilmente en muestras de polvo de instalaciones avícolas recolectadas mediante sedimentación en placa y pueden proporcionar un método de muestreo alternativo para monitorear coccidiosis y el estado de enteritis necrótica en la parvada. Se requieren más estudios para evaluar la utilidad de tal prueba en parvadas comerciales.

Multi-carbohydrase enzymes improve feed energy in broiler diets containing standard or low crude protein.

This study evaluated the effect of multi-carbohydrase (MC) on energy and nitrogen (N) balance and gene expression in broilers fed diets with different crude protein (CP) contents. The study employed a 2 × 2 factorial arrangement of treatments. The factors were presence or absence of MC, and standard (SCP) or low (LCP) dietary CP concentration. A 3-phase feeding program was used, including starter (0 to 7 d), grower (8 to 17 d) and finisher (18 to 28 d) phases. The study was undertaken in closed calorimetry chambers. Each of the 4 dietary treatments was replicated 8 times in total across 2 runs, with 2 birds per replicate (n = 64). Data for energy partitioning and N balance were collected from d 25 to 28. On d 28, birds were euthanized to collect muscle and intestinal tissue samples for gene expression. The results showed that the MC increased apparent metabolizable energy (AME, P < 0.01) and net energy (NE, P < 0.05), and reduced the feed conversion ratio (FCR, P < 0.01) in all diets. The proportion of energy retained as fat per total energy retention (REf/RE) was positively correlated with feed AME and NE (r = 0.541, P < 0.01 and r = 0.665, P < 0.001, respectively), suggesting that feed energy augmented with increased fat gain. Muscle ATP synthase subunit alpha (ATP5A1W) gene expression had a positive correlation with REf/RE and feed NE (r = 0.587, P < 0.001 and r = 0.430, P < 0.05, respectively). Similarly, muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1A) expression was negatively correlated with weight gain and positively correlated with FCR (r = -0.451, P < 0.05 and r = 0.359, P < 0.05, respectively). These correlations show that over-expressions of muscle genes related to energy production reduce bird performance. This study demonstrated that MC increase dietary energy utilization, regardless of dietary CP concentration. However, the energy released by the enzymes increases feed energy-to-CP ratio, meaning there is excess energy that is then deposited as body fat. This suggests that supplemental MC in broiler feeds is beneficial if diets are formulated to contain marginal energy levels.

Multi-carbohydrase effects on energy utilization depend on soluble non-starch polysaccharides-to-total non-starch polysaccharides in broiler diets.

Non-starch polysaccharides (NSP), especially in water-soluble form, are a common anti-nutritional factor in cereal-based poultry diets. Consequently, carbohydrases are applied to diets to combat the negative effects of NSP on bird performance and health, particularly when feeding viscous grains. This study investigated the effect of supplementing multi-carbohydrases (MC) to broiler diets containing either low (LS) or high (HS) soluble NSP (sNSP) to total NSP (tNSP) ratios on energy partitioning, nitrogen (N) balance, and performance. A 2 × 2 factorial arrangement of treatments (MC, no or yes; sNSP/tNSP, LS vs. HS) was applied, resulting in 4 dietary treatments, each replicated 8 times. These treatments were fed to Ross 308 broilers in closed-circuit indirect calorimetry chambers, with 2 birds (a male and a female) per replicate chamber (n = 64). The results showed that MC addition increased AME, net energy (NE), and AME/gross energy, regardless of sNSP/tNSP content (P < 0.01 for all). There was an MC × sNSP/tNSP interaction for feed intake (FI, P < 0.05), denoting that in the absence of MC, the HS-fed birds had lower FI than LS-fed birds, but this difference was eliminated when MC was present. There were MC × sNSP/tNSP interactions observed for AME intake (AMEi) per metabolic BW (BW0.70, P < 0.05), AMEi/N retention (Nr, P < 0.01), NE intake (NEi)/Nr (P < 0.05), retained energy (RE) as fat per total RE (REf/RE, P < 0.01), and N efficiency (Nr/N intake, P < 0.05). These interactions showed that MC application increased AMEi/BW0.70, AMEi/Nr, NEi/Nr, and REf/RE only in the HS-fed birds, and N efficiency only in the LS-fed broilers. This study demonstrated that MC application markedly increased feed energy utilization in all diets, and increased N efficiency in birds fed an LS diet.

Replacement value of cottonseed meal for soybean meal in broiler chicken diets with or without microbial enzymes.

A 4×2 factorial feeding trial was designed to investigate the effect of replacing soybean meal (SBM) with cottonseed meal (CSM) in wheat/sorghum/SBM-based diets fed with or without microbial enzymes in diets on the performance, visceral organ development and digestibility of nutrients of broiler chickens. Four graded levels of CSM - none (0%), low (4%, 8%, and 12%), medium (5%, 10%, and 15%), and high (6%, 12%, and 18%) of complete diets in starter, grower and finisher, respectively were fed with or without 100 mg/kg of xylanase and ß-glucanase blend. Eight isocaloric and isonitrogenous diets were formulated using least-cost method to meet the nutrient specifications of Ross 308 male broilers. Each treatment was randomly assigned to 6 replicates (10 birds per replicate). There were CSM-enzyme interactions (p < 0.05) on feed intake (FI) and weight gain (WG) in the starter phase. Enzyme supplementation improved (p < 0.05) feed conversion ratio (FCR) in the grower and finisher phases, and increased WG in growing and finishing birds. CSM inclusion reduced (p < 0.05) the weight of gizzard and proventriculus in starter chicks, while these organs were bigger (p < 0.05) in the grower phase. The test ingredient decreased (p < 0.05) small intestinal weight in starter and grower birds. The CSM increased the absolute weight of thighs (p < 0.05) while breast meat was increased (p < 0.01) by enzyme addition. Starch digestibility was improved (p < 0.01) by enzyme inclusion and decreased (p < 0.01) by CSM. Enzyme supplementation improved (p < 0.05) the ileal digestibility of gross energy and protein. The results demonstrate that CSM can substitute up to 90% SBM in broiler chicken diets without compromising performance, and the nutritive value of CSM-containing diets can effectively be improved by enzyme supplementation.