Nutreco (Canada)

Abstract Although several animal models have been developed so far, there are very few that are in use for either research or commercial applications. In poultry, the challenge of model application may be greater than for other species because decision making must be quick and low-risk given the short production cycle of the birds. However, poultry growth models are an important opportunity for both research and commercial applications as they represent a chance to better understand the growth response of birds and to better determine their requirements depending on the growing conditions. Given the limited volume of turkey meat production relative to broiler production, there is a great opportunity to apply turkey models in the industry and in research. This chapter explains the challenges that may be faced when developing and applying models, and proposes a methodology to ensure the successful application of these models using the turkey as an example.

In vitro digestibility techniques have been developed to predict the apparent total tract digestibility (ATTD) of energy and DE content of mixed diets and feedstuffs including barley grain in swine. However, the techniques have not been tested properly for their accuracy in predicting the variation in ATTD of energy and DE content within wheat grain. The objectives were 1) to compare two 3-step in vitro digestibility techniques with either cellulase (IVD-CEL) or Viscozyme (a multienzyme complex to digest fiber; Novozymes, Bagsvaerd, Denmark; IVD-VIS) as the third step, and differing in the amount of enzymes used and the duration of digestion, for their accuracy in predicting ATTD of energy and DM of wheat in grower pigs; and 2) to develop equations to predict ATTD of energy of different batches of wheat. Wheat grain samples (n = 20) with a wide range in quality were collected; the ADF and CP content ranged from 3.3 to 6.2% and from 11.2 to 20.8% (DM basis), respectively. The ATTD of energy was determined using barrows (n = 60, 30.7 +/- 4.7 kg of initial BW) in 2 periods with 6 observations per sample, and ranged from 73.3 to 84.5%. In IVD-CEL, 1 g of ground wheat was digested sequentially in digestion solutions containing pepsin (10 mg/36.5 mL) for 6 h, pancreatin (150 mg/54.5 mL) for 18 h, and cellulase (75 mg/55.5 mL) for 24 h. In IVD-VIS, 0.5 g of ground wheat sample was digested sequentially in solutions containing pepsin (25 mg/36.5 mL) for 2 h, 3 mL of pancreatin (100 mg/54.5 mL) for 6 h, and Viscozyme (0.5 mL/65.3 mL) for 18 h. The in vitro energy and DM digestibility ranged from 79.8 to 91.0% and from 82.0 to 91.5% for IVD-CEL, and ranged from 76.2 to 87.0% and from 79.1 to 89.4% for IVD-VIS, respectively. The R(2) between ATTD of energy and in vitro DM and energy digestibility for IVD-VIS (0.82 and 0.73, respectively) was greater than for IVD-CEL (0.55 and 0.54, respectively). The equation y = 1.05x - 8.85 using the in vitro DM digestibility value from IVD-VIS can predict the ATTD of the energy of wheat in swine with an SE of prediction of 1.2. The relationship between in vitro DM digestibility and grain characteristics such as ADF was stronger for the IVD-VIS than for the IVD-CEL technique (R(2) = 0.89 vs. 0.70). In conclusion, the IVD-VIS, but not the IVD-CEL, technique can accurately (R(2) = 0.82) predict the ATTD of energy in wheat in grower pigs. Therefore, the IVD-VIS technique might be useful as the reference analysis to calibrate analytical equipment to predict the ATTD of energy rapidly in wheat.

Clostridium perfringens is an important pathogen of animals and humans and is the causative agent of necrotic enteritis (NE) in poultry. This study focuses on the typing of intestinal C. perfringens isolates (n = 61) from outbreaks of NE collected from several areas of Southern Ontario, using a recently developed multilocus sequence typing (MLST) technique. For comparison, C. perfringens isolates from healthy birds were also obtained and typed. An additional locus, the pfoS locus, was included in our analysis, in an attempt to increase the discriminatory ability of the method previously published. Birds were collected from two major poultry processors in Canada, and isolates from processor 2 formed a distinct MLST cluster. Isolates from healthy birds also collected from the outbreak flocks clustered together with isolates from the birds with NE. Although isolates from eight outbreaks clustered together, MLST types were also occasionally different between outbreaks. Strong linkage disequilibrium was observed between loci, suggesting a clonal C. perfringens population structure. Detection assays for toxin genes cpb2 (beta-2 toxin), tpeL, and the newly described netB (NetB toxin) were also performed. netB was almost always found in outbreak isolates, whereas cpb2 was found exclusively in healthy bird isolates. The toxin gene tpeL, which has not been previously identified in C. perfringens type A strains, was also found, but only in the presence of netB. Resistance to bacitracin was found in 34% of isolates from antimicrobial agent-free birds and in 100% of isolates from conventionally raised birds.

Cell proliferation and alpha-toxin gene expression of Clostridium perfringens in relation to the development of necrotic enteritis (NE) were investigated. Unlike bacitracin-treated chickens, non-bacitracin-treated birds exhibited typical NE symptoms and reduced growth performance. They also demonstrated increased C. perfringens proliferation and alpha-toxin gene expression that were positively correlated and progressed according to the regression model y = b(0) + b(1)X - b(2)X(2). The average C. perfringens count of 5 log(10) CFU/g in the ileal digesta appears to be a threshold for developing NE with a lesion score of 2.