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In utero heat stress negatively affects the growth performance of barrows
In utero heat stress can alter fetal development and postnatal growth. Heat stress has been known to affect piglet birth weight which can affect growth performance, resulting in more days on feed and lighter weights at slaughter. Therefore the objectives of this work were to determine the effects of in utero heat stress, excess dietary lysine and Paylean on growth performance of barrows. 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% NRC; n=20) or exceeded (110% NRC; 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. Weight, average daily gain (ADG), feed disappearance (FD), feed efficiency (G:F), and liver weight were recorded. At one week of age, HS barrows were heavier (2183.00 ± 60.48 vs 1999.01 ± 59.66 g; P=0.03). In the late finisher phase, PAY barrows were heavier (125.96±0.89 vs 129.00± 0.89 kg; P=0.05). In both the grower (P=0.04) and finisher (P=0.05) phases, FD was greater in HS barrows (2.22 ± 0.05 vs 2.08 ± 0.05; 3.29 ± 0.08 vs 3.00 ± 0.08, respectively). In the grower phase, G:F tended to be greater (P=0.08) in TN barrows (0.40 ± 0.01 vs 0.38 ± 0.01) and was greater (P = 0.003) in 100% NRC barrows (0.40 ± 0.01 vs 0.38 ± 0.01), while FD was reduced (P=0.02) in 110% NRC barrows (2.07 ± 0.05 vs 2.23 ± 0.05). In the finisher phase, PAY barrows had improved (P<0.0001) G:F (0.36 ± 0.01 vs 0.28 ± 0.01) and (P<0.0001) ADG (0.96 ± 0.04 vs 0.75 ± 0.04 kg/d). Liver weight was increased (P=0.05) in 110% NRC barrows (1.49 ± 0.02 vs 1.42 ± 0.02 kg). Barrows exposed to heat stress during gestation have increased FD, but reduced weight at finishing. Supplementation with excess lysine and Paylean offer benefits during finishing, and may help overcome the negative effects of gestational heat stress.
Keywords: Heat stress, growth performance, ractopamine