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Serum Insulin-like Growth Factor-I (IGF1), Growth Hormone (GH), insulin, and glucose in first parity sows exposed to Heat Stress (HS) during gestation
Objectives were to examine the effects of gestational HS on metabolic and hormonal profiles. Gilts (n=54) in environmental chambers were assigned to cyclical heat stress (HS; n=27; 27 to 37ºC; relative humidity, RH 85 to 55%) or thermoneutral (TN; n=27; 15 to 20ºC; RH 60 to 50%) treatments that were applied from week (wk) 1 to wk16 of gestation. Gilts were moved to a TN farrowing room during wk17. Blood was collected during gestation [wk1, wk5, wk9, wk13, and wk17; samples (S) S1 to S5], after farrowing (lactation wk1, wk2, and wk3; S6 to S8), and 9d after weaning (S9). Body weight (BW), back fat (BF), and loin eye area (LEA) of sows were measured monthly. There was an effect of treatment (P<0.001) on rectal temperature (38.44±.02 vs. 38.26±.02ºC; P<0.001) and respiration rate (50±1 vs. 31±1 BPM; P<0.001) (HS vs. TN, respectively). HS and TN gilts had similar starting BW (138±2 kg), BF (2.7±.1 cm), and LEA (42.6±.7 cm2) but HS gilts were heavier (186±3 vs. 178±2 kg; P<0.001), had more BF (2.7±.1 vs. 2.4±.1 cm; P<0.05), and greater LEA (45.2±.1.1 vs. 41.4±1.0 cm2; P<0.01) at end of gestation. Blood glucose increased from late gestation and early lactation (70, 73, 69, 76, 88, 87, 83, 79, and 70 mg/dL; S1 to S9; SEM=1; P<0.001). Pattern for serum insulin was similar to glucose (0.13, 0.11, 0.20, 0.25, 0.19, 0.41, 0.40, 0.40, and 0.24 ng/mL; S1 to S9; SEM=.03; P<0.001). HS decreased (P<0.001) blood glucose during wk9 and 13. IGF1 progressively decreased during gestation and then increased after farrowing (106, 88, 61, 51, 52, 121, 119, 105, 122 ng/mL; S1 to S9; SEM=4; P<0.001). Changes in IGF1 were associated with changes in GH (38, 32, 28, 38, 38, 37, 39, 36, 36 ng/mL; S1 to S9; SEM=2; P<0.001) during early gestation. HS did not affect insulin, IGF1, or GH. There were large changes in hormonal and metabolic profiles during gestation and lactation. HS elevated glucose during late gestation. Changes in IGF1 were not explained by changes in GH perhaps suggesting an uncoupling (during gestation) and then recoupling (during lactation) of the somatotropic axis. This project was supported by USDA NIFA 2011-67003-30007.
Keywords: sow, heat stress, endocrinology