A study supported by FAPESP and published in the journal Frontiers in Animal Science shows that the way in which male pigs are confined – and not just females, as was known – profoundly affects the way in which the offspring deal with stress, which interferes with their well-being. of these animals.
A series of experiments carried out at the Faculty of Veterinary Medicine and Animal Science at the University of São Paulo (FMVZ-USP), in Pirassununga, showed that four weeks of living in cells are enough for males to have puppies with emotional changes linked to fear and anxiety, in addition to high levels of cortisol in saliva when exposed to challenges.
“While eggs are formed during the female’s intrauterine life, sperm are formed from puberty onwards and continuously. Males, therefore, can serve as sentinels of what is happening, giving the possibility of intervening to obtain piglets with greater well-being”, explains Adroaldo José Zanella, professor at FMVZ-USP who coordinated the study.
The work is part of the project “The contribution of the male to the development of robust phenotypes and the mitigating role of the welfare of female pigs”, supported by FAPESP and coordinated by Zanella.
In the experiments, 138 piglets aged 25 days were subjected to behavioral tests, to assess emotionality, and saliva analysis, in order to check cortisol levels, an indicator of stress.
Only after carrying out the experiments were paternity tests carried out to determine which treatment the father of each piglet came from. This is because the semen of animals in contrasting conditions was mixed before inseminating the females, therefore, each female gave birth to piglets from several fathers.
The sperm donors that gave rise to the piglets were subjected, for four weeks, to one of three types of treatment: they were kept in cells where they only had to get up and lie down, housing conditions used in commercial breeding; in individual bays, with more space; or in individual enriched pens.
In the latter, they received a daily bath and tactile stimuli: they were brushed daily and had access to hay to chew or lie on. Food and water availability were the same for all treatments.
The researchers demonstrated that the parents’ housing conditions influenced the offspring’s behaviors. In all behavioral tests, offspring of male pigs raised in the cells showed changes in emotional states indicative of anxiety and fear.
Saliva tests also showed an increase in cortisol levels after the application of behavioral tests to the puppies of males raised in cells and stalls. In piglets whose parents lived in enriched pens, there was no difference in measurements before and after the tests.
The results are consistent with another study by the group, which used the same animals and treatments. In the article, the researchers show that males raised in enriched pens gave birth to more live piglets that survived their first month of life.
Furthermore, piglets originating from male pigs housed in the cells had a greater perception of pain, an indicator that the environment to which the father is exposed altered the child’s perception, which could influence his well-being.
Next steps
“We are carrying out other studies that show that the type of treatment to which males are subjected causes epigenetic changes [no genoma] which are possibly transmitted to the puppies”, says Leandro Sabei, first author of the article, carried out during his doctorate at FMVZ-USP.
In a previous study by the group, researchers demonstrated that the type of confinement influences the physiology of adults’ testicles.
“In animals raised in cells, the beginning of testicular degeneration occurs. The semen becomes more clumped and the temperature of the testicle is higher, which can compromise fertility”, adds Thiago Bernardino de Almeida, first author of that work and co-author of the current one, both carried out during his doctorate with a scholarship from FAPESP.
In another study from the same project, the group demonstrated how the gestation environment of females affects the brain development of piglets.
Another publication by the researchers showed how five days in crates during the period after heat causes stress and interferes with the females’ vaginal microbiota, which can affect nutrient absorption and protection against diseases in puppies.
“Our work is already influencing the decisions of breeders, who are seeing that greater welfare increases productivity and profits. The objective now is to carry out even more robust studies of all stages of the animals’ lives, in addition to offering the porcine model for studies relevant to humans”, concludes Zanella.
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