(GEBIOMET team) – The integrated systems of agricultural production (SIPA) have shown promising results for cattle raised on pasture. However, a question arises: how would this system be for sheep? Does it work?

One of the modalities of SIPA, the silvopastoral system, is a sustainable system of raising animals on pasture, very promising for sheep farming when considering the thermal comfort and welfare of animals. When kept on open field, sheep and lambs are exposed to challenging environmental conditions, which may lead to reduced productivity of these animals, altering their physiological regulation and behaviours. Based on this, studies were conducted by GEBIOMET to investigate the influence of the housing system on the behaviour and physiology of lambs and ewes. The results were published in two papers in the scientific journal Small Ruminant Research, entitled “Physiological responses of Santa Inês x Dorper ewes and lambs to thermal environment of silvopasture and open pasture systems", published on the Small Ruminant Research (Elsevier) (click here to read the full-text) and “Postpartum behavioural response of Santa inês x Dorper ewes and lambs in a silvopastoral system”, also published on the Small Ruminant Research (Elsevier) (click here to read the full-text), under the supervision of Prof. Frederico and Prof. Flávia. Frederico and Prof. Flávia Barros (UTFPR), the works were written by the Veterinary Julia Dada (MSc. in Animal Science, and current PhD candidate by PPZ UNIOESTE/UTFPR) and the Bioprocess Engineer and Biotechnology, Matheus Luquirini (PhD student at UNESP - Botucatu), students members of the group, along with the co-authorship of Prof. Maria Nunes-Zotti (UDESC) and the former student, the Animal Scientist Pricilla Muniz. Let us see below the main results of this work.

Microclimate
Regarding the environmental data of the experiments, we observed that the microclimate of both was characterised as stressful to the animals, presenting an average Temperature and Humidity Index (THI or UTI) of 77 for the silvopastoral (SP) and 78 for the open pasture (OP), being that the THI between 74 and 81 is considered a concern for sheep. However, the SP was milder, with a difference of 1.1 °C in mean air temperature compared to the OP.

Thermoregulation and physiology
During the hottest hours of the day, the sheep showed signs of high heat stress in the OP, characterised by an increased respiratory rate (121-192 breaths/min). In the morning period, on the other hand, they showed moderate to severe stress (61-80 breaths/min). In contrast, the SP ewes went from low pressure in the morning (40-60 breaths/min) to severe in the afternoon. Furthermore, a high heart rate when the animal is at rest indicates heat stress. Our results showed that ewes and lambs had an elevated heart rate in both environments (70-80 and 80-100 beats/min).

One of the methods of reducing body temperature is heat exchange through the skin with the environment. Our results showed that sheep and lambs exposed to the sun had a higher mean surface temperature, which is the value of the body surface temperature, signalling that these animals would have more incredible difficulty regulating their body temperature. However, when the rectal temperature was measured, both ewes (38.3°C to 39.9°C) and lambs (39.8°C to 40.3°C) of both environments did not show values outside what is considered normal (up to 42°C). This means the thermoregulatory mechanisms efficiently maintained a constant temperature inside the animal. However, the animals of the OP system expended more metabolic energy to keep the rectal temperature within the normal range.

Behaviour
Sheep and lambs exposed to the direct sun are subject to stress and are more likely to be panting for several hours than those kept in a shaded environment. During the morning period, interestingly, animals tended to exhibit the same behaviours both on the pasture and in the SP, probably due to the similar temperature in both environments.
Certain behaviours demonstrated throughout the day indicate the animals' thermal comfort. Our studies showed that both ewes and lambs kept on open pasture had a greater tendency to remain standing still. These results are by the warmer stressful microclimate of the OP system.

Conclusion
SIPAs already had plenty of reasons to be adopted in livestock farming. Through this research, silvopastoral systems gain prominence for sheep and lambs. If well managed and correctly implemented, the shading trees provide an environment for the sheep to perform thermal exchanges and increase their thermal comfort. However, the emphasis is also on young animals. Shade is necessary for the lamb to reach its optimal level of well-being and remain on its development curve appropriate for the breeds.