Carcass composition of market weight XXXX subjected to heat stress in utero and during finishing.

@entity1707 @entity26680 @entity8682 @entity7443
Objectives were to investigate the effects of prolonged gestational and/or postnatal heat stress on performance and carcass composition of market weight @entity1707 . Pregnant gilts were exposed to gestational heat stress (GHS, 28  C to 34  C, diurnal) or thermal neutral (18  C to 22  C, diurnal) conditions during the entire gestation or during the first or second half of gestation. At 14 wk of age (58    5 kg), barrows were housed in heat stress (32  C, @entity8682 ) or thermal neutral (21  C, @entity7443 ) conditions. Feed intake and BW were recorded weekly, and body temperature parameters were monitored twice weekly until slaughter (109    5 kg). Organs were removed and weighed, and loin eye area (LEA) and back fat thickness (BF) were measured after carcass chilling. Carcass sides were separated into lean, separable fat, bone, and skin components and were weighed. Moisture, lipid, and protein content were determined in the LM at the 10th rib. Data were analyzed using a split plot with random effect of dam nested within gestational treatment. Carcass measurements included HCW as a covariate to control for weight. Planned orthogonal contrast statements were used to evaluate the overall effect of GHS in the first half, second half, or any part of gestation. Gestational heat stress did not alter postnatal performance or most body temperature parameters (P > 0.10). However, ADFI in the finishing period was increased (P < 0.05) in response to GHS, particularly in @entity1707 receiving GHS in the first half of gestation. Gestational heat stress during the first half of gestation decreased head weight as a percent of BW (P = 0.02), whereas GHS in the second half of gestation decreased bone weight as a percent of BW (P = 0.02). Heat stress reduced ADG, BW, and HCW (P < 0.0001). Lean tissue was increased in @entity8682 @entity1707 on both a weight and percentage basis (P < 0.0001), but LEA was similar to @entity7443 carcasses (P = 0.38). Carcasses from @entity8682 barrows also had less carcass separable fat (P < 0.01) and tended to have less BF (P = 0.06) compared with those from @entity26680 , even after controlling for HCW. However, percent intramuscular fat did not differ between treatments (P = 0.48). The LM from @entity8682 carcasses had a greater moisture to protein ratio (P = 0.04). @entity8682 barrows also had decreased heart (P < 0.001) and kidney (P < 0.0001) as a percent of BW compared with @entity7443 @entity1707 . In summary, GHS may affect head and bone development, subsequently affecting carcass composition. Chronic @entity8682 during finishing results in longer times to reach market weight and a leaner carcass once market weight is achieved.
