The impact of pellet quality on production efficiency and pig behavior in heat-stressed and thermoneutral environments

Abstract Text: Two studies evaluated the impact of pellet quality on production efficiency and pig behavior in differing environments. Pigs (n=180) were housed in one of two adjacent environmental rooms, heat-stressed (HS) or thermoneutral (TN). Both the HS and TN environments were replicated 3 times. Average daily highs and lows for HS were 32° and 23°C and for TN were 14° and 11°C. Pigs were housed individually in pens (1.5m²) with woven wire flooring, cup waters and open-faced feeders. Corn-soy diets were manufactured at the NCSU Feed Mill to contain 1 of 5 levels of pellet fines; 0, 15, 30, 45 or 60%. Different levels of pellet fines were created by separating the pellets from the fines and then adding the fines back to the pellets at the desired ratio. At an average weight of 112.5±5.9kg, barrows and gilts were randomly assigned to treatments for 21 d. Weekly pig weights, feed consumption, pig behavior, respiration rate (breaths per min) and rectal temperature (RT) were collected. Pig behavior was categorized as; drinking, eating, standing or resting. Statistical analysis was performed using analysis of variance. Pen was the experimental unit when evaluating pellet fines and room was the experimental unit when comparing HS and TN environments. Level of pellet fines was not associated (P≥0.35) with ADFI or ADG in either HS or TN. A 10% increase in pellet fines numerically reduced (P≥0.14) G:F in HS and TN by 0.007±0.005 and 0.003±0.006, respectively. A 10% increase in pellet fines was associated with lower (P<0.05) RT for both HS and TN on d 0 (-0.038°±0.018 and -0.039°C±0.019, respectively) and d 14 (-0.092°±0.021 and -0.038°C±0.016, respectively). Level of pellet fines did not impact (P>0.05) behavior. However, a 10% increase in pellet fines numerically increased (P≥0.35) the percentage of time observed eating in HS and TN by 0.3±0.4 and 0.4%±0.5, respectively. Heat-stress had similar (P=0.44) ADFI (2.87 vs. 3.01kg), tended (P=0.08) to have lower ADG (0.95 vs. 1.07kg) and had similar (P=0.35) G:F (0.336 vs. 0.366) in comparison to TN. Respiration rate and RT were greater (P<0.05) for HS in comparison to TN on d 7 (95 vs. 34 and 39.5° vs. 38.8°C, respectively) and d 14 (71 vs. 30 and 39.3° vs. 38.7°C, respectively). Results are in disagreement with previous findings associating pellet quality and pig performance. Differences in experimental design, specifically housing and feeder type, may have contributed to the results.

Keywords: growth, heat-stress, pellet