EFFECT OF THREONINE LEVEL IN A HIGH PROTEIN DIET ON GROWTH PERFORMANCE AND CARCASS CHARACTERISTICS OF 50 TO 91 DAYS OLD SLOW-GROWING INDIGENOUS MALE BOSCHVELD CHICKENS

Tebogo Mack SekgotodiJones Wilfred Ng'ambiTlou Grace Manyelo^*

• University of Limpopo, Sovenga, Limpopo, South Africa

An experiment was conducted to determine dietary threonine level effect on the growth performance of slow-growing 50-91 days old male Boschveld chickens. A total of 75 chickens were used in a complete randomized design having 5 dietary treatments, with three replicates and five chickens per replicate. The dietary treatments had similar nutrient contents but different threonine levels of 4.0, 7.5, 8.0, 8.5 or 9.0 g/kg DM. Collected data was subjected to a one-way analysis of variance using SAS version 9.4. A quadratic equation was used to determine dietary threonine levels for optimal performance of the chickens. Threonine levels affected (P<0.05) feed intake, body weight gain, feed conversion ratio, metabolisable energy intake, nitrogen retention, abdominal fat weight, and meat crude protein and threonine levels of the chickens. Body weight gain, feed conversion ratio, metabolizable energy intake, nitrogen retention, abdominal fat weight, and meat crude protein and threonine levels of the chickens were optimized at dietary threonine levels of 6.12, 6.82, 5.71, 6.0, 6.9, 5.9 and 5.7 g/kg DM, respectively. However, feed intake of the chickens decreased (P<0.05) when dietary threonine levels were increased. Dietary threonine levels did not affect (P>0.05) chicken meat pH values.However, the threonine level in the diet affected (P<0.05) chicken meat colour. Chicken meat lightness and hue angle had positive relationships (P<0.05) with dietary threonine levels while meat redness, yellowness and chroma had negative relationships (P<0.05) with dietary threonine levels. It was concluded that male Boschveld chicken production parameters were optimized at different dietary threonine levels.