Effects of mill type and particle size uniformity on growth performance, nutrient digestibility, and stomach morphology in finishing pigs.

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.

Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in finishing pigs.

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.

Reducing particle size of corn in lactation diets from 1,200 to 400 micrometers improves sow and litter performance.

One hundred primiparous sows were used to determine the effects of particle size of corn in lactation diets on sow and litter performance. The sows were fed a corn-soybean meal-based diet with the corn ground to 1,200, 900, 600, or 400 microns. Particle size of corn had no influence on sow BW or backfat loss (P > .30), subsequent weaning-to-estrus interval (P > .40), or percentage of sows returning to estrus (P > .09). However, ADFI was increased (linear effect, P < .04) as particle size was reduced from 1,200 to 400 microns. Pig survivability was not affected (P > .30) but litter BW gain was increased by 11% when sows were fed diets with 400 vs 1,200 microns corn (linear effect, P < .05). Apparent digestibilities of DM, N, and GE were increased by 5, 7, and 7%, respectively, as particle size was reduced from 1,200 to 400 microns (linear effects, P < .001). Intake of DE was increased 14% (13.7 to 15.6 Mcal/d) as corn particle size was reduced from 1,200 to 400 microns. Intakes of digestible DM and N also were increased (11 and 14%, respectively), whereas fecal excretions of DM and N were decreased by 21 and 31%, respectively (linear effects, P < .001). Reducing particle size increased severity of ulceration and keratinization (nonzero correlations of P < .04 and P < .004, respectively) in the esophageal region of the stomach, although the changes were not associated with reduced sow performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary buffers on growth performance, nutrient digestibility, and stomach morphology in finishing pigs.

The effects of supplemental alkaline salts on growth performance, blood chemistry, and stomach morphology were determined in two experiments using 248 finishing pigs fed finely ground diets. In Exp. 1, 128 pigs (56 kg average initial BW) were fed a corn-soybean meal-based diet (488-microns mean particle size) for 66 d. Treatments were control and 1, 2, or 3% added NaHCO3 in a randomized complete block design. Average daily gain (linear effect, P < .005), dressing percentage (linear effect, P < .04), and plasma urea N concentration (linear effect, P < .004) decreased as the concentration of NaHCO3 in the diet was increased, but primarily at the 2 and 3% additions. Feed intake, gain/feed, backfat thickness, stomach ulceration score, blood gases (pCO2 and HCO3), and plasma Na and K were not affected by treatment (P > .11). In Exp. 2, 120 pigs (55 kg average initial BW) were fed a pelleted wheat-soybean meal-based diet (355-microns mean particle size) during a 64-d growth assay. Treatments were 1) control, 2) 1% NaHCO3, and 3) 1% KHCO3. Average daily gain, ADFI, gain/feed, backfat thickness, stomach keratinization score, blood pCO2, plasma urea N, and digestibilities of DM and N were not affected by treatment (P < .15). However, addition of NaHCO3 and KHCO3 tended to decrease (P < .10) the incidence of ulcers and increased (P < .05) the concentration of blood HCO3- and digestibility of GE. These data indicate that 1% addition of either NaHCO3 or KHCO3 may help to reduce the severity of gastric ulcers in finishing pigs without adversely affecting growth performance or nutrient digestibility.

Effects of reducing particle size of corn in lactation diets on energy and nitrogen metabolism in second-parity sows.

Thirty-eight second-parity sows were used to determine the effects of particle size of corn in lactation diets on nutrient metabolism. The sows were fed a corn-soybean meal-based diet with the corn ground to targeted average particle diameters of 1,200, 900, 600, and 400 microns. Loss of BW and backfat and litter performance were not influenced by treatment (P > .10). However, as particle size was reduced from 1,200 to 400 microns, apparent digestibilities of DM (linear effect, P < .001) and N (quadratic effect, P < .007) were increased by 7 and 10%, respectively, and fecal excretions of DM and N were decreased (linear effects, P < .001) by 35 and 42%, respectively. Urinary N excretion was not affected by particle size (P > .20), but there was a trend (P < .08) for the greatest apparent biological values at the intermediate particle sizes (i.e., 900 and 600 microns). Thus, with increased apparent digestibility and no increases in urinary loss, N retention was increased by 22% as particle size of corn was reduced from 1,200 to 600 microns (quadratic effect, P < .04). Digestible energy and ME concentrations of the diets were increased as particle size of corn was reduced from 1,200 to 400 microns (linear effects, P < .001), with a ME value of 3,745 kcal/kg for the diet with corn at 400 microns compared with 3,399 kcal/kg for the diet with corn at 1,200 microns.(ABSTRACT TRUNCATED AT 250 WORDS)