Effects of diet form and corn particle size on growth performance and carcass characteristics of finishing pigs

• Pigs fed pelleted diets had improved growth performance compared with those fed meal diets.
• Feed efficiency improved as corn particle size decreased for pigs fed meal diets but not for those fed pelleted diets.
• These results suggest that in pelleted diets, grinding corn finer than 650 μm for offers no benefit.

A total of 960 crossbred pigs, initially 34.3 ± 0.50 kg, were used in a 101-day trial to determine the effects of corn particle size and diet form on growth performance and carcass characteristics of finishing pigs. Pens were randomly allotted by initial weight to 1 of 6 experimental treatments with 8 pens per treatment and 20 pigs per pen. The 6 experimental treatments were arranged in a 2 × 3 factorial with main effects of final feed form (meal vs. pellet) and corn particle size (650 μm, 350 μm, or an equal blend of the 650 μm and 350 μm ground corn). The 650 μm corn was ground using a two-high roller mill, and the 350 μm corn was ground using a full circle hammer-mill equipped with a 1.59 mm screen. After all corn was ground, the diet containing the blend of particle sizes was manufactured by adding equal portions of the 2 at the mixer. Overall (day 0–101), linear particle size × diet form interactions were observed (P < 0.05) for average daily feed intake (ADFI) and gain:feed ratio (G:F), because ADFI decreased and G:F increased as particle size was reduced for pigs fed meal diets but was unchanged for pigs fed pelleted diets. Pigs fed pelleted diets had increased (P < 0.05) average daily gain (ADG) compared with pigs fed meal diets. As corn particle size decreased, ADG decreased (linear; P < 0.05). Pigs fed pelleted diets had increased (P < 0.05) hot carcass weight compared with pigs fed meal diets, but no other effects on carcass characteristics were observed. In summary, grinding corn finer than 650 μm decreased ADFI and improved G:F for pigs fed meal diets, but did not affect performance of pigs fed pelleted diets. Pigs fed pelleted diets had improved ADG compared with those fed meal-based diets. Thus, grinding corn finer than 650 μm improved feed efficiency for pigs fed meal diets, but provided no benefit in pelleted diets.