Effects of different dietary threonine levels on growth and slaughter performance in finishing pigs

Abstract

The objective of this study was to determine the threonine (Thr) requirement of a modern crossbred growing pig from Austria in the finisher stage (67 to 113 kg body weight). For on average 50 days, 30 castrated male and 30 female pigs were fed isonitrogenous diets (135 g/kg crude protein, 8.0 g/kg lysine) supplemented with increasing levels of crystalline Thr. Total dietary Thr contents (g/kg) were 4.9 (basal diet), 5.0, 5.4, 5.8, 6.1, 6.5, corresponding to a Thr:Lys ratio of about 0.60, 0.64, 0.68, 0.73, 0.76, 0.81. Dietary Thr concentration of 5.4 g/kg improved daily gains by about 15 percentage points (<i>P</I> < 0.05) and the feed conversion ratio by about 7 percentage points, compared to pigs fed the basal diet (4.9 g/kg Thr). Increasing dietary Thr above 5.4 g/kg had no further effects on performance. The blood plasma urea concentration was minimized at a dietary Thr concentration of 6.1 g/kg. For all treatments there was a low effect of dietary Thr supply on carcass quality. Goblet cell density in the small intestine and colon did not differ between different levels of dietary Thr. Based on the results of growth performance, an optimum total dietary Thr:Lys ratio in the finisher stage of pigs ranges from 0.66 to 0.68.