The effects of particle size and pelleting on growth performance, carcass characteristics, nutrient digestibility, and stomach morphology were determined using 160 finishing pigs. The pigs were fed a corn-soybean meal-based diet with the corn milled to particle sizes of 1,000, 800, 600, or 400 microns. The diets were fed in meal or pellet form. Pelleting the diets resulted in 5% greater ADG (P < .01) and 7% greater grain/feed (P < .001). Also, pelleting increased digestibilities of DM, N, and GE by 5 to 8% (P < .001). Reducing particle size increased electrical energy required for milling and decreased milling production rates, especially as particle size was decreased from 600 to 400 microns. Reducing particle size of the corn from 1,000 to 400 microns increased gain/feed by 8% (linear effect, P < .001) and digestibility of GE by 7% (quadratic effect, P < .03). Improved nutrient digestibility and lower ADFI resulted in 26% less daily excretion of DM and 27% less daily excretion of N in the feces as particle size was reduced from 1,000 to 400 microns (linear effects, P < .001). Stomach lesions and keratinization increased with reduced particle size (P < .003) and keratinization increased with pelleting (P < .02), although they were unrelated to growth performance (i.e., gain/feed actually improved as lesion scores increased). Considering milling energy, growth performance, stomach morphology, nutrient digestibility, and nutrient excretion, a particle size of 600 microns, or slightly less, is an acceptable compromise for corn in both meal and pelleted diets for finishing pigs.

A total of 240 weanling pigs (22 d of age and 5.3 kg average BW) were used to determine the effects of particle size of corn and two sorghum hybrids on diet processing, growth performance, apparent digestibility of nutrients, and morphology of the stomach and intestines in weanling pigs. Treatments were corn, hard endosperm sorghum, and soft endosperm sorghum milled to particle sizes (geometric mean) of 900, 700, 500, and 300 microns, in a 3 x 4 factorial arrangement. All diets were pelleted and the pigs were allowed to consume feed and water on an ad libitum basis. As particle size was reduced, production rate (tons/hour) decreased and energy required to mill (kilowatt hours/ton) increased. Corn required more energy to mill and had a lower production rate than the sorghums. For d 0 to 14, ADG and gain/feed increased linearly (P < .009 and P < .002, respectively) as particle size was decreased to 300 microns. However, there was a grain source x particle size interaction; pigs fed corn responded to particle size reduction more than pigs fed the sorghums (P < .04). For d 0 to 35, pigs fed diets with corn grew 23% faster and were 6% more efficient (P < .001) than pigs fed diets with sorghum. Gain/feed responded quadratically to reduction of particle size (P < .01), with maximum gain/feed at 500 microns for all grains. Lowest cost of gain (including milling and ingredient costs) was achieved at 500 to 700 microns for corn and 500 microns for the hard and soft sorghums. These data suggest that response to reducing particle size is greatest during the first 2 wk postweaning and that optimal particle size for corn and sorghums increases with age of nursery pigs.

Rations containing varying ratios of corn, high-oil corn, soybean meal, and mechanically expelled soybean meal were pelleted. The effects of ingredients, conditioning steam pressure, and mixing paddle configuration inside the conditioner on pellet quality were investigated. Ration ingredients strongly affected pellet quality. Increasing the protein content increased the pellet durability, whereas increasing the oil content above 7.5% greatly decreased pellet durability. High-oil corn and mechanically expelled soybean meal produced acceptable pellets when combined with soybean meal and regular corn, respectively. However, poor pellet quality resulted when rations containing high-oil corn and mechanically expelled soybean meal were processed. Increasing the residence time in the conditioner by changing mixing paddle pitch resulted in an average 4.5-point increase in pellet durability indices among 65:35 (wt) corn:soybean meal and 65:35 high-oil corn:soybean meal rations.

The objective of this study was to determine the effects of diets containing crude glycerol on pellet mill production efficiency and nursery pig growth performance. In a pilot study, increasing crude glycerol (0, 3, 6, 9, 12, and 15%) in a corn-soybean meal diet was evaluated for pellet mill production efficiency. All diets were steam conditioned to 65.5 degrees C and pelleted through a pellet mill equipped with a die that had an effective thickness of 31.8 mm and holes 3.96 mm in diameter. Each diet was replicated by manufacturing a new batch of feed 3 times. Increasing crude glycerol increased both the standard (linear and quadratic, P < 0.01) and modified (linear, P < 0.01; quadratic, P

The effects of particle size uniformity and mill type used to grind corn were determined in three experiments. In Exp. 1, 120 pigs (47.8 kg initial BW) were used. Treatments were 1) a 40:60 blend of coarsely rolled (in a roller mill) and finely ground (in a hammermill) corn with a large standard deviation (sgw) of particle size (sgw of 2.7), 2) hammermilled corn with an sgw of 2.3, and 3) roller-milled corn with an sgw of 2.0. Mean particle size of the corn was approximately 850 microns for all treatments. Growth performance was not affected (P > .11); but, stomach keratinization tended to be less severe (P < .08) and apparent nutrient digestibilities were greater (P < .008) when the sgw was smaller. In Exp. 2, 128 pigs (55.3 kg initial BW) were used. Treatments were corn ground in a hammermill and a roller mill to 800 and 400 microns. Pigs fed corn ground to 400 microns were more efficient (P < .004) and had greater apparent digestibilities of DM, N, and GE (P < .001) than pigs fed corn ground to 800 microns. Mill type did not affect growth performance (P > .40), but pigs fed corn ground in the roller mill had greater apparent nutrient digestibilities (P < .008). In Exp. 3, 128 pigs (67.3 kg initial BW) were used. Treatments were corn ground to 400 microns in a hammermill and a roller mill fed in meal and pelleted forms. Pigs fed pelleted diets had greater ADG (P < .003) and gain/feed (P < .03) but also had greater incidence of ulcers (P < .04). Pigs fed roller-milled corn were more efficient (P < .05) and had a lower incidence of ulcers (P < .04), but diets with hammermilled corn had lower sgw and greater apparent digestibilities of nutrients (P < .02). Our results suggest that mill type had inconsistent effects on growth performance, but more uniform particle sizes consistently gave greater nutrient digestibilities.