Valine and isoleucine requirements
Valine is a limiting essential AA in current piglet diets and potentially limiting in fattening pig diets containing very low levels of CP. In comparison to piglets, the Val requirement of fattening pigs has not been extensively studied since, considering the current CP levels, it is a less potentially limiting AA for heavier pigs than Trp for instance. Van Milgen et al. (2013) recently published a review and meta-analysis of the existing Val dose-response trials for growing pigs and concluded that, on average, a dietary level of 69% SID Val:Lys ratio is necessary to achieve the best ADG in the considered data set. This supports the practical usual recommendation of 70% SID Val:Lys implemented in piglet (25 kg LW) remains to be confirmed since only few studies have been performed (i.e., one study only is considered in van Milgen et al., 2013 work). An optimum value is therefore difficult to assess but it is at least recommended to apply a minimum level of 65% SID Val:Lys for pigs above 25 kg when dietary CP is reduced in fattening pigs.
Isoleucine requirement in growing pigs used to be controversial due to published values varying from less than 50% to more than 60% SID Ile:Lys for the same weight category. One of the main reasons of such variability is now explained and lies into the usage of Spray Dried Blood Cells (SDBC) in the dose-response experiments. The SDBC are poor in Ile and so are a very good material to use in basal diet dedicated to perform Ile dose responses. But, at the same time, the SDBC have an imbalanced global AA content (low level of Ile but excessive amount of Val, Leu, His & Phe) which leads to singular interactions. This results in an increasing catabolism of Ile and so in an apparent increase of the Ile requirement. The work of Wiltafsky et al. (2009) and a meta-analysis work of van Milgen et al. (2012) clearly indicate that without usage of SDBC in pig diets the Ile requirement is between 50% and 54% SID Ile:Lys.
Valine and isoleucine requirements Valine is a limiting essential AA in current piglet diets and potentially limiting in fattening pig diets containing very low levels of CP. In comparison to piglets, the Val requirement of fattening pigs has not been extensively studied since, considering the current CP levels, it is a less potentially limiting AA for heavier pigs than Trp for instance. Van Milgen et al. (2013) recently published a review and meta-analysis of the existing Val dose-response trials for growing pigs and concluded that, on average, a dietary level of 69% SID Val:Lys ratio is necessary to achieve the best ADG in the considered data set. This supports the practical usual recommendation of 70% SID Val:Lys implemented in piglet (<25 kg LW) but the question of the optimum Val level in fattening pigs (>25 kg LW) remains to be confirmed since only few studies have been performed (i.e., one study only is considered in van Milgen et al., 2013 work). An optimum value is therefore difficult to assess but it is at least recommended to apply a minimum level of 65% SID Val:Lys for pigs above 25 kg when dietary CP is reduced in fattening pigs.Isoleucine requirement in growing pigs used to be controversial due to published values varying from less than 50% to more than 60% SID Ile:Lys for the same weight category. One of the main reasons of such variability is now explained and lies into the usage of Spray Dried Blood Cells (SDBC) in the dose-response experiments. The SDBC are poor in Ile and so are a very good material to use in basal diet dedicated to perform Ile dose responses. But, at the same time, the SDBC have an imbalanced global AA content (low level of Ile but excessive amount of Val, Leu, His & Phe) which leads to singular interactions. This results in an increasing catabolism of Ile and so in an apparent increase of the Ile requirement. The work of Wiltafsky et al. (2009) and a meta-analysis work of van Milgen et al. (2012) clearly indicate that without usage of SDBC in pig diets the Ile requirement is between 50% and 54% SID Ile:Lys.
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