Effect of feed particle size in pelleted diets on growth performance and digestibility of weaning piglets

Abstract

The objective of this study was to evaluate the effect of particle size in pelleted diet on nutrient digestibility and growth performance of weaning piglets. 352 uncastrated males, aged 28 to 63 d, were distributed in a randomized block design (initial weight) according to treatments. The experimental feeds were divided into two phases, pre-initial (28 to 42 d) and initial (43 to 63 d) and produced with different corn particle sizes ground in a hammer mill, which provided a geometric mean diameter (GMD) of 394 µm, 534 µm, 647 µm, and 695 µm respectively, to the pre-initial phase diets. In the initial phase the GMD were 587 µm, 625 µm, 798 µm, and 943 µm. All feeds were pelleted (pellet diameter 2.5 mm) and supplied ad libitum. After an analysis of variance (P < 0.05), orthogonal contrasts were constructed to evaluate the linear and quadratic effect of increasing feed particle size on digestibility and growth performance. In the pre-initial phase, there was no difference in daily feed intake and daily weight gain between treatments; however, there was a quadratic response (P < 0.05) in feed/gain ratio, and the reduction of GMD to 534 µm was positively correlated with feed/gain ratio. In the initial phase, feed intake increased linearly (P < 0.05) with increasing GMD in the pelleted diet. GMD had no effect on feed/gain ratio, but there was a linear correlation (P < 0.05) between GMD and weight gain in this phase, owing to greater feed consumption. There was a linear response (P < 0.05) in dry matter and ether extract digestibility coefficients, with the highest values determined in pigs consuming the finest diets (587 µm). GMD had no effect on crude protein digestibility, but there was a quadratic correlation (P < 0.05) between particle size and digestible energy, as digestible energy reduced when GMD increased up to 798 µm, followed by a slight increase at 943 µm. In conclusion, as the weaning pigs become older, their growth performance response increases with increasing particle size of the pelleted diet. The GMD for an optimal pelleted feed is 534 µm for pre-initial and 943 µm for initial phase. Additionally, during the initial phase, fine particle sizes results in better efficiency of feed utilization.