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In utero heat stress alters body composition during the early finishing phase (60 to 80 kg) in pigs
The detrimental effects of heat stress (HS) on animal productivity have been well-documented. However, whether gestational HS interacts with a future environmental insult to alter tissue deposition during the early finishing phase in pigs is unknown. Study objectives were to compare the subsequent rate and quantity of tissue accretion in finisher pigs exposed to differing in utero and postnatal thermal environments. Pregnant gilts were exposed to thermal neutral (TN; cyclical 15ºC nighttime and 22ºC daytime; n = 9) or HS (cyclical 27ºC nighttime and 37ºC daytime; n = 11) conditions during the entire gestation. Twenty-four offspring from gestational TN (GTN; n = 6 gilts, 6 barrows; 62.4 ± 0.7 kg BW), and gestational HS (GHS; n = 6 gilts, 6 barrows; 61.9 ± 0.8 kg BW) gilts were euthanized as part of an initial slaughter group (ISG). After the ISG, 48 pigs from GTN (n = 12 gilts, 12 barrows; 66.1 ± 1.0 kg BW) and GHS (n = 12 gilts, 12 barrows; 63.4 ± 0.7 kg BW) were exposed to constant HS (34.4 ± 1.8°C) or TN (22.7 ± 2.5°C) conditions until they reached 80.5 ± 1.5 kg BW, at which point they were sacrificed and chemical body composition determined. Homogenized carcasses were analyzed for N, crude fat, ash, water and gross energy content. Data were analyzed using PROC MIXED in SAS 9.3. Rectal temperature and respiration rates were increased during postnatal HS compared to TN (39.6 vs. 39.3˚C and 92 vs. 58 bpm, respectively; P < 0.01). Postnatal HS decreased (P < 0.01) feed intake (19.4%) and ADG (0.70 vs. 0.94 kg/d) compared to TN conditions, but neither variable was influenced by gestational environment. Protein and adipose tissue accretion rates were reduced in HS pigs compared to TN controls (126 vs. 164 g/d and 218 vs. 294 g/d, respectively; P < 0.04). In utero HS independently reduced protein accretion (16%; P < 0.01), and increased adipose accretion rates (292 vs. 220 g/d; P < 0.07) compared to GTN in the finisher phase. The ratio of adipose to protein accretion rates increased (95%; P < 0.01) in pigs experiencing GHS compared to GTN. In summary, pigs from GHS employ epigenetic mechanisms that impact the future hierarchy of tissue accretion and this altered nutrient partitioning favors adipose tissue deposition at the expense of skeletal muscle during this phase of growth.
Keywords:
heat stress, tissue accretion, epigenetics