Steam-pelleting temperatures of sorghum-based broiler diets
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Sorghum is uniquely vulnerable to ‘moist-heat’, which raises the possibility that high steam-pelleting temperatures of sorghum-based diets may have a deleterious impact on growth performance and nutrient utilisation in broiler chickens.
Broiler diets are steam-pelleted at high temperatures (~ 90°C) to achieve acceptable pellet quality via starch gelatinisation and to reduce bacterial contamination (eg Salmonella). However, there is increasing interest in the possibility that excessive steam-pelleting temperatures may have deleterious effects on broiler growth performance and nutrient utilisation. This appears to be the case with ‘viscous’ grains (eg wheat, barley) largely due to solubilisation of non-starch polysaccharides; however, the position is less clear with non-viscous grains (eg sorghum, maize). ‘Moist-heat’ has been shown to reduce sorghum in vitro pepsin digestibility substantially where the dominant proteins in sorghum are kafirin and glutelin. The negative impact of moist-heat is mainly attributed to the formation of disulphide linkages in b- and g-kafirin fractions located in the periphery of protein bodies of sorghum endosperm. Kafirin is the dominant sorghum protein and this ‘case-hardening’ of the protein body impedes digestion of the central core of a-kafirin. It is probable that moist-heat also induces disulphide linkage formation in the glutelin component of sorghum protein. Both kafirin (protein bodies) and glutelin (protein matrix) are intimately associated with starch granules in the sorghum endosperm. Thus the likelihood is that reductions in the digestibility of kafirin and glutelin will, in turn, depress starch digestibility and energy utilisation. Thus the pivotal question is whether or not steam-pelleting broiler diets constitutes sufficient moist-heat to compromise the nutritive value of sorghum. If this is the case, the practical challenge will be to produce acceptable pellet quality (and decontamination) at reduced steam-pelleting temperatures.
This project will be supported by a Poultry CRC Scholarship for the successful applicant. These Scholarships are available only to Australian and New Zealand citizens and Australian permanent residents. The Scholarships offer an annual stipend of $30,000 AUD as well as up to $20,000 AUD per annum in operating costs. The project will be run as part of a larger project supported by the RIRDC CME. International applicants will be considered if they have scholarships already in place.
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The opportunity ID for this research opportunity is: 1199
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