A study was conducted by Todd Applegate of Purdue University and others there and at Maple Leaf Farms and Cotter Laboratory to establish the dietary threonine requirement of Pekin ducks from 15 to 35 days of age.

In a paper in Poultry Science, they describe how experimental diets were formulated to contain 0.55, 0.60, 0.65, 0.75, and 0.85 per cent threonine (0.57, 0.60, 0.64, 0.72 and 0.80 per cent on an analysed basis) and were studied in two experiments.

In Experiment 1, each diet was fed to 10 pens of 52 drakes per pen. Samples were collected on day 35 for determinations of carcass yields, serum immune parameters and intestinal characteristics.

Experiment 2 was a digestibility study, wherein 0.5 per cent chromic oxide was mixed into the experimental diets and fed from 15 to 19 days. Ileal digesta were collected on day 19 to analyse mucin secretions and apparent ileal threonine digestibility.

The results showed that feeding 0.72 per cent versus 0.64 per cent threonine improved bodyweight gain between 15 and 35 days by 55g (P<0.05), reduced feed-to-gain by 0.04 (P<0.05) and increased carcass and breast meat yields by 22 and 24g, respectively.

Also, 0.72 per cent threonine had the highest crude mucin secretion on a dry matter intake (DMI) basis (P<0.05), although threonine had no effect on villus height, crypt depth, goblet cells or MUC2 gene expression in the jejunum and ileum.

In addition, serum natural immounoglobulin Y (IgY) linearly increased (P<0.0001) with dietary threonine increase.

Using non-linear regressions, threonine requirement was estimated to range from a low of 0.70 per cent to maximise dry crude mucin secretion on the basis of dry matter intake to a high of 0.80 per cent to maximise carcass weight and serum IgY production by the linear or quadratic regression.

Equivalently, threonine requirement varied between a low of 0.62 per cent to minimise mortality and a high of 0.73 per cent to maximise dry crude mucin secretion expressed on the basis of dry matter intake using the quadratic broken-line model.

Correspondingly, the apparent ileal digestible threonine requirements were estimated to be 0.52 to 0.66 per cent (0.70 to 0.80 per cent dietary threonine) by quadratic and 0.47 to 0.56 per cent (0.62 to 0.73 per cent dietary threonine) by quadratic broken-line model.

Reference

Zhang Q., L. Xu, A. Doster, R. Murdoch, P. Cotter, A. Gardner and T.J. Applegate. 2014. Dietary threonine requirement of Pekin ducks from 15 to 35 days of age based on performance, yield, serum natural antibodies, and intestinal mucin secretion. Poultry Science. 93(8):1972-1980. doi: 10.3382/ps.2013-03819

August 2014