Using extreme thermal processing to improve nutrient utilization of diets for finishing pigs

Abstract Text: A total of 270 pigs (PIC 337 × 1050; initially 52.2 kg BW) were utilized in a 79-d experiment to determine the effects of feed processing methods (long-term conditioning or extrusion) on finishing pig growth performance and carcass characteristics. There were 7 or 8 pigs per pen and 9 pens per treatment. Treatments included 1) negative control: non-processed mash, 2) positive control: pelleted with 45 s conditioner retention time, 3) pelleted with 95 s conditioner retention time, and 4) extruded. Diets were fed in 3 phases with the same low energy formulation across treatments containing 30% corn dried distillers grains with solubles and 19% wheat middlings. Thermal processing, regardless of length or type, affected ADG and G:F (P < 0.05), but not ADFI (P > 0.10). Extruded diets tended to improve G:F compared to pelleted diets (P < 0.10). Interestingly, HCW was greater when pigs were fed pelleted diets compared to extruded diets, regardless of conditioning time (P < 0.05). However, pigs fed any thermally-processed treatment had greater HCW compared to those fed the negative control mash (P < 0.05). Thermal processing did not influence percentage yield, backfat, or loin depth when HCW was used as a covariate (P > 0.10). However, pigs fed thermally-processed diets had greater jowl iodine value compared to those fed mash diets (P < 0.05). This experiment again confirms the benefits of thermally processing feeds to improve ADG and G:F, but neither extended conditioning nor extrusion extracted additional nutrients from low energy feedstuffs compared to traditional pelleting. However, this research suggests that more extreme thermal processing conditions may be used for feed safety purposes without hindering nutrient utilization.

Keywords: extrude, pellet, pig

Table 1.
Item	Mash	45s Pellet	90s Pellet	Extruded	SEM	P =
ADG, kg	0.95	0.99	1.01	0.98	0.012	< 0.001
ADFI, kg	2.78	2.73	2.78	2.68	0.038	0.140
G:F	0.341	0.362	0.363	0.368	0.003	< 0.001
HCW, kg	91.5	95.1	95.5	94.9	1.20	0.046
Yield, %	72.1	72.7	72.4	72.6	0.19	0.092
Backfat, mm	20.5	19.7	20.9	20.6	0.56	0.524
Loin depth, mm	60.9	62.7	62.5	62.7	0.83	0.353
Jowl iodine value	75.7	77.0	77.1	77.5	0.40	0.008