Interference of stress with the somatotropic axis in pigs - lights on new biomarkers

Abstract

The acceptance of animal products is increasingly associated with standardized animal welfare, which relates to appropriate animal husbandry from birth to slaughter. In particular, shipment to the slaughterhouse is considered as a critical process exposing the animals to a number of, in part severe, stressors. New biomarkers may be useful for the assessment of animal welfare. The IGF-system has been assessed in a commercial pig transport in conjunction with established markers of stress response. Furthermore, the effect of repeated restraint as an experimental model for repeated acute stress was investigated. During shipment from farm to slaughterhouse, plasma concentrations of IGFBP-3 and IGFBP-2 were significantly reduced (p < 0.01). After shipment, the plasma concentrations of IGFBP-5, glucocorticoids and IL-2 increased but decreased after lairage (p < 0.05) whereas IGF-1 decreased after shipment (p < 0.01). Repeated acute stress increased concentrations of IGFBP-3 and IGF-1 in exsanguination blood (p < 0.05). Differential IGF- signatures can indicate altered endocrine or metabolic control and thus contain complex animal-related information. The somatotropic axis may be of particular interest when established biomarkers such as cortisol, glucose, or lactate cannot be used for the assessment of animal stress or welfare.

Figure 1

IGF-system at different sampling times of transportation procedure: IGFBP-profile (A), IGFBP-3 ((B); n = 31), IGFBP-2 ((C); n = 31), IGFBP-5 ((D); n = 31), IGF-1 ((E); n = 13) and IGF-2 ((F); n = 13). Quantitative data are presented as LS-means+ SE. rh: recombinant human. *p < 0.05, **p < 0.01, ***p < 0.001, ^#p < 0.1.

Figure 2

The total amount of IGFBPs as marker for IGF-binding capacity ((A); n = 31) and the ratio of IGF-1/total IGFBPs as indicator for IGF-1 bioavailability ((B), n = 13) during different stations of transport. Data are presented as LS-means+ SE. *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 3

Effect of transport duration on plasma IGFBP-2 ((A); n = 240) and cortisol ((B); n = 90). IGFBP-2 was analyzed using quantitative Western ligand blot. Cortisol was analyzed using LC-MS/MS. Data are presented as LS-means+ SE. *p < 0.5, **p < 0.01, ***p < 0.001.

Figure 4

Stress and inflammation associated parameters at different sampling times of commercial transportation procedure: Plasma concentrations of cortisol (A), corticosterone (B), adrenaline (C) and noradrenaline (D), IL-2 (E), SAA (F) and albumin (G). Cortisol, IL-2 and SAA were analyzed with ELISA. Corticosterone was analyzed using LC-MS/MS. Adrenaline and noradrenaline were analyzed using HPLC. Albumin was analyzed using an enzymatic spectrophotometric assay. All Data are presented as LS-means+ SE. Cortisol, adrenaline, noradrenaline, SAA: n = 31 per sampling time. Corticosterone, IL-2, albumin: n = 13 per sampling time. ^#p < 0.1, *p < 0.05, ** p < 0.01, ***p < 0.001.

Figure 5

Stress vocalization and evaluation of lesions at different events of pig transport. (A) Stress vocalization, presented as LS-means + SE of every event, respectively. (B) Exemplary data of stress vocalization during different events of trial 2. (C) The number of lesions measured in home pen and after transport, presented as LS-means + SE. (D) Percentage of animals per category of transport-induced increase of lesion score. The stress vocalization was analysed using STREMODO and includes all animals in the range of sound recorder. Lesions: n = 65. *p < 0.05, **p < 0.01, ***p < 0.001.