Detection of Local Tissue Reactions after Anti-GnRF Injection in Male Pigs Assessed Using Magnetic Resonance Imaging

Abstract

This study aimed at evaluating the local tissue reaction of an anti-GnRF product, which is used for the so called “immunocastration” in male pigs. A total of 34 pigs were injected two times (including a booster injection) with an anti-GnRF product. Injection was performed using the prescribed safety vaccinator. Injection sites were evaluated three times post injection using magnetic resonance imaging. Two examinations were performed after the first injection and one after the booster. The local tissue reaction was evaluated three-dimensionally by semi-automatic analyses, by linear measurements of injection depth and length, and by scoring the kind of tissue affected. Results showed a long-lasting reaction in affected muscle tissue. Therefore, needle length should be discussed, and an evaluation of the injection site after slaughter should be performed include behavioural scorings post injection to evaluate the impact on animal well-being and carcass quality.

Magnetic Resonance Imaging Used to Define the Optimum Needle Length in Pigs of Different Ages

“…Human and animal research [ 16 , 17 , 18 , 19 , 26 , 27 ] have shown that the optimum injection depth results in less pain and being transferred to animals might result in higher animal welfare. This is of great importance, even if irritating inoculums or vaccines are used, which can result in large-scale tissue alterations [ 1 , 2 , 5 , 6 , 7 , 25 ].…”

“…Additionally, the volume of injectable solutions may influence the location and the local reaction [ 1 , 2 , 5 , 25 ]. Therefore, muscle growth should be taken into account as well.…”

“…Each intramuscular injection results in tissue alteration and tissue destruction [ 1 , 2 , 3 , 4 ], which very likely results in pain. Tissue alterations based on drug application are described for different formulations and different animal categories [ 5 , 6 , 7 ]. In contrast to laboratory animals [ 8 , 9 , 10 ], explicit information on injection type, volume and needle size is missing for farm animals.…”

Tracing the Inside of Pigs Non-Invasively: Recent Developments

“…To date, MRI in pigs is mainly being used for research purposes-and not for classical performance testing [39][40][41][42][43][44]. A few studies exist, however, where MRI (+DXA) helped to verify or to develop new performance test equations related to fattening of intact boars [45] or to test relationships between male phenotypes and carcass and meat quality [46,47], as was also done by using CT [48].…”

“…Further useful applications of MRI include the determination of in vivo tissue aberrations (density and volume changes) after the administration of different vaccines or hormone analogs in pigs [40,49,50]. The administration of a GnRF analog can lead to massive tissue changes and ultimately tissue necrosis at the administration site [40,50], negatively affecting muscle function and local meat quality.…”