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In utero heat stress alters body temperature and loin eye area in barrows
In utero heat stress has been shown to alter the thermoregulation of the postnatal animal, altering heat tolerance and potentially growth performance. Therefore, the objective here was to determine how in utero heat stress, excess lysine and Paylean altered body temperature, lean tissue accretion, and fat deposition in barrows throughout the finishing phase. At 25 kg, barrows of control (TN; n=40) or heat stressed (HS; n=40) dams were individually housed and fed a corn soybean meal diet. At this time, barrows were equally and randomly assigned to receive a diet that met (100%; n=20) or exceeded (110%; n=20) NRC lysine requirements. In the last 30 days of finishing, barrows were again equally and randomly assigned to a diet containing 0 (CTL; n=10) or 7.4 ppm Paylean (PAY; n=10). Diets were fed until 121 kg of weight was attained. During both finishing phases, skin temperatures of the ear (ETEMP) and body (BTEMP) were obtained twice daily two days per week and ultrasound was performed to determine loin eye area (LEA) and back fat depth (BF). Temperatures and ultrasound data are reported according to which finishing phase measures were taken, either first finish phase (F1) or second finish phase (F2). In F2, HS caused reduced (P<0.05) ETEMP (35.07 ± 0.14 vs 35.54 ± 0.14 oC) and greater LEA (P = 0.03; 40.13 ± 0.66 vs 38.15 ± 0.65 cm2); 110 caused higher BTEMP (P<0.05; 32.77 ± 0.34 vs 33.76 ± 0.33 oC); and Paylean increased ETEMP and BTEMP (P<0.05; 34.54 ± 0.26 vs 33.51 ± 0.26; 33.44 ± 0.28 vs 32.31 ± 0.28 oC) and LEA at slaughter (54.89 ± 1.06 vs 48.85 ± 1.04 cm2). HS PAY pigs had higher temperatures (P<0.05) than HS CTL pigs (33.96 ± 0.41 vs 32.1 ± 0.40 oC), but not TN CTL pigs (33.96 ± 0.41 vs 32.52 ± 0.40 oC). HS CTL had larger (P=0.02) LEA in F2 than TN CTL (44.01 ± 0.89 vs 40.97 ± 0.89 cm2). ETEMP was inversely related (P<0.05) to LEA in F1 (r=-0.20). HS barrows maintain lower temperatures, which were increased by 110% lysine and Paylean, indicating that HS barrows have the potential to maintain lower body temperatures and produce greater LEA at slaughter.
Keywords:
Temperature, heat stress, ractopamine, loin eye area