The animal article of the month for February is ‘Short communication: natural interomone 1 2-methyl-2-butenal stimulates feed intake and weight gain in weaned pigs‘.  Authors: J. J. McGlone, G. Thompson and S. Devaraj

While nearly two-thirds of human olfactory receptors have mutated and become non-functional pseudogenes, farm mammals have retained a high number of functional olfactory receptors. Pigs have a large number of robust olfactory receptors which make them “see” their world through a rich olfactory landscape. Discovering the olfactory needs of farm animals is a developing field of science; much like nutritionists discovered nutrient requirements of animals. Indeed, when olfactory signals are missing, it parallels nutrient deficiencies in that animal health, welfare and growth can be compromised.

The term interomone indicates a molecule or molecules that are clearly a pheromone in one species, but have yet-unexplained by clear effects on the behavioral biology of other species.

The first interomone to be described is the pig sex pheromone that changes dog behavior. Androstenone was the first sex pheromone reported in mammals. We showed that the pig sex pheromone stopped dogs from barking, jumping and leash pulling (McGlone et al., 2014; Pirner et al., 2016).

Then, we turned our attention to stress-reducing pheromones. Among many candidates, we knew that rabbit pups show nipple-searching behavior in response to the maternal pheromone 2-Methyl-2-Butenal (2M2B; Schall et al., 2003). Maternal pheromones tend to be comforting to the neonate. When we sprayed 2M2B in the post-weaning environment, the weaned pigs ate more feed and grew faster (McGlone et al., 2016). This work was performed at our university farm with high-health pigs (ex., there was zero mortality during the month after weaning). We have had difficulty replicating this work in commercial farm pigs whose health was poorer and the environment more odorous. Among high-health pigs, this interomone may provide a boost in performance via a mechanism quite different than growth-promoting antibiotics. The requirement for the environment to be very clean and the pigs healthy, may limit its application at this time. The “normal” production environment is a confusing olfactory environment because pigs are present with varying health statuses and varied levels of stress (which produces alarm pheromones, among other negative volatile molecules). Restoration of a maternal pheromone or interomone in the post-weaning environment is a potentially powerful way to reduce the negative impact of weaning where piglets are placed in an environment deficient in maternal odors.

The big picture here relates to the discovery of a new class of candidate compounds that have the potential to improve farm animal performance and/or welfare. These are not drugs by USA FDA definition and they are natural molecules conserved across species from insects to mammals. Reproductive pheromone technologies have been suggested to be clean, green and ethical tools (Martin et al., 2004). Here, I suggest that the clean, green and ethical concept can be extended to include interomones and semiochemicals with the potential to improve not only reproduction, but the health and welfare of growing and adult farm animals. We have many candidate semiochemical molecules and many production problems to solve, including restoration of deficiencies in the olfactory environment, and use of natural chemical signals to improve health, performance and welfare.

This article is freely available for one month:

Short communication: natural interomone 1 2-methyl-2-butenal stimulates feed intake and weight gain in weaned pigs‘.

Authors: Authors: J. J. McGlone, G. Thompson and S. Devaraj

The animal Article of the Month is selected by the Editor-in-Chief and is freely available for one month. View the recent selections

Literature cited
Martin GB, Milton JTB, Davidson, RH, Banchero Hunzicker GE, Lindsay DR, Blache, D 2004. Natural methods for increasing reproductive efficiency in small ruminants. Anim. Reprod. Sci. 82, 231-245.
McGlone JJ, WG Thompson, and Guay, KA 2014. Case study: The pig pheromone, acting as an interomone, stops dogs from barking. Prof. Anim. Sci. 30:105-108.
McGlone JJ, Thompson, G, Devaraj S 2016. A natural interomone 2-methyl-2-butenal stimulates feed intake and weight gain in weaned pigs. Animal 10, 1–3.
Pirner G and McGlone JJ 2016. Impact of androstenone on leash pulling and jumping up in dogs. Animals 6, 34-43.
Schall B, Coureaud G, Langlois D, Ginies C, Semon,E, Perrier G 2003. Chemical and behavioral characterization of the rabbit mammary pheromone. Nature. 424, 68-72.

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