Effect of physical form of whole ear corn silage (coarse vs wet milled) included at high dietary levels (30 vs 40% dry matter) on performance of heavy finishing pigs

The aim of the trial was to compare two dietary levels of whole ear corn silage (ES), fed in two physical forms (coarse or after wet milling), on growth, slaughter traits and stomach development of heavy finishing pigs. Fifty six “Italian Large White × Italian Duroc” (about 5 months of age and 78-80 kg of live weight (LW) were divided into pairs homogeneous and were kept in 28 pens (1.2 × 3 m, partially-slatted) equipped with two separate troughs to avoid competitions for feeding and with free access to water. Four dietary treatments resulted from the combination of two ES inclusion levels (300 and 400 g/kg dry matter (DM), ES30 and ES40, respectively) and two physical forms of the silage (coarse and wet milled). Seven pairs of pigs were randomly assigned to each dietary treatment and the animals were slaughtered at an average LW of 163.0 kg (±1.9 kg). The coarse ES had particles longer than the milled silage (4.4 vs 2.7 mm) and when it was fed to pigs the pH of fecal samples were lower (P<0.01) than that from pigs fed the milled ES, at both dietary inclusion levels (6.00 vs 6.20 for the ES30 diets and 5.97 vs 6.14 for the ES40 diets). There were no significant differences in organic matter total tract digestibility, average daily gain, DM intake and gain:feed ratio among the dietary treatments (0.81, 764 g/d, 77.1 g DM/kg LW0.75, 0.266 g/g DM, on average, respectively). The ES40 diets reduced the Longissimus dorsi thickness (56.4-59.8 vs 62.7-64.1 mm, P<0.011) and increased the stomach weight (0.0040 vs 0.0038 of the LW, P<0.05), while the coarse dimension of silage particles increased the DM content of the material in the stomach (from 142-171 to 179-183 g/kg DM, P<0.045) and the surface of the pyloric region (from 214-216 to 225-232 cm2, P<0.029). The two dietary inclusion levels and physical forms of ES do not differentiate growth and slaughter traits of the heavy finishing pigs. However, the coarse form of the silage modifies the development of the stomach by increasing the internal surface of the pyloric region as a possible consequence of a longer retention time in the stomach.