Economic and environmental constraints are pushing down piglets’ dietary protein content and several amino acids (AA) tend to limit performance. Various synthetic AA are often used to overcome this problem.
Apart from lysine (Lys), methionine, tryptophan and threonine, the use of which is common and well documented, valine (Val) is proving to be restrictive in piglets receiving low-protein diet. However, the data in the literature are still scant and need to be corroborated.
To that end, trials have been carried out at the CRA-W’s experimental piggery, in cooperation with ORFFA Belgium, to validate growth-limiting lysine and valine levels in weaned piglets fed low-protein diets. The first step was to verify that a level of 0.95% standardised ileal digestible (SID) lysine and a Val/SID Lys ratio of 60% were limiting in post-weaning piglets (Phase 1). Then, a valine dose-response test on post-weaning piglets was carried out to establish the Val/SID Lys ratio that optimizes expression of the growth potential (Phase 2).
The Phase 1 tests showed that a low-protein diet deficient in lysine and valine restricted animal performance. Performance was improved when the diet was supplemented with those amino acids. A level of 0.95% SID lysine in the feed in combination with a Val/SID Lys ratio of 60% was therefore found to limit the performance of piglets on a low-protein diet. The Phase 2 valine dose-response test established the optimum Val/SID Lys ratio for expression of the animals’ growth potential in these conditions. By applying a curvilinear-plateau statistical model to the performance data (weight gain and consumption index) the Val/SID Lys ratio was established as 69.2%, which is close to that quoted in the literature (70%).
The study has validated the valine level needed to optimise growth in piglets fed a low-protein diet.