Seasonal variations in thermoregulatory patterns enable Morada Nova sheep to adapt to Brazilian semi-arid

Abstract

The present study aimed evaluate possible modifications of thermoregulatory morphophysiological responses of Morada Nova sheep throughout the year in 4 properties of the nucleus of participatory genetic breeding. In the months of March, June, September and December, respiratory rate (RR), rectal temperatures (RT) and surface (ST) were recorded as well as the environmental variables air temperature (airT), relative humidity (RH) wind (Ws). Calculated the radiant heat load (RHL) and the Black Globe Humidity Index (BGHI). The coat thickness was measured and hair samples were collected and determined hair density, hair length and hair diameter. Blood collection was collected for determination of T3 and total T4 concentrations. In the rainy season, which includes the months of March and June, higher values of RR and RT, probably due to the combination of high RH, associated to RHL, BGHI and airT were recorded, as these hamper loss and heat. All values of RT independent of month and flocks remained within values considered normal for the species. September and December are inserted in the dry season, with a low RH factor that can facilitate heat loss through evaporation. In these months, lower values of RT and RR were observed when compared to the rainy season, lower values of RR were recorded between 40 and 60 mov.min-1 . The secretion of thyroid hormones was greater in the environmental conditions considered more comfortable. The homeothermia was maintained by Morada Nova sheep at different times evaluated as indicated by the normal physiological parameters. The rainy season was considered the most stressful for the animals, since they used a more intense set of variables in order to thermoregulate and maintain the homeothermia, which justifies the importance of providing shelters, with the objective of reducing the overheating, even in view of their great adaptive capacity, already demonstrated in previous studies. Changes in the coat characteristics were observed during all the months of the year, assisting for either physical protection or heat dissipation and could therefore be indicated as a thermotolerance phenotypic marker with the potential to be used as selection criteria in breeding programs and conservation of resistant animals to heat.

Effects of Feed Supplementation on Nesfatin-1, Insulin, Glucagon, Leptin, T3, Cortisol, and BCS in Milking Ewes Grazing on Semi-Natural Pastures

“…Thyroid hormone concentrations tended to decrease from 36 h to 21 days post-partum and thereafter constantly rose until day 51 post-partum [ 39 ], and slightly higher concentrations of TH were observed in the blood of ewes at the 40th day of lactation than at the 20th day [ 40 ]. After the start of our trial, animals were also exposed to rising summer ambient temperatures, which exert a well-known depressive effect on thyroid gland activity and TH action [ 41 ] and are inversely correlated with plasma thyroid hormone levels [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. In the present study, high ambient temperatures may have prevented the physiological recovery of thyroid hormone concentrations, which are often observed toward the end of lactation in small ruminants, in parallel with the reduction of milk production and the increase of energy balance.…”

“…On the other hand, in early lactation, low TH, leptin and insulin levels can indicate an energy deficiency of ewes, even despite the concentrate supplementation. Blood metabolic hormones and BCS are very useful tools for the assessment of ewes’ nutritional status in very demanding physiological states, such as late pregnancy and lactation [ 40 , 41 , 42 , 43 , 44 ].…”

“…Regarding the COR peak observed in SUP ewes at the last sampling, different papers report similar effects by heat stress in small ruminants [ 46 , 47 ]. The serum COR levels were the highest during summer [ 43 , 44 , 45 , 46 , 47 , 48 , 49 ] and positively correlated with ambient temperature, showing reverse trends and negative correlations with TH [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Moreover, during thermal stress, feed-restricted ewes [ 51 ] and rams [ 25 ] showed less increase in cortisol blood concentrations: therefore, if the nutritional deficit is added to thermal stress, the animals can adjust their response, avoiding the potential adverse effects of extreme cortisol action, as it could be the case of the UNS group of the present study.…”

“…The farm where our ewes were kept suffered a lot of damage, as well as the houses of the farmers, so it was not possible to carry on the intended further controls, and the overall situation after the earthquake could have direct and indirect effects influencing the results. Despite this accident, fortunately, we had the possibility to have some indication from research performed on other ewes of the same flock, which showed that the feed supplementation had a positive effect on resistin production in the sheep uterine glands [ 52 ] and in the apelinergic system expression in both mammary glands and female reproductive apparatus [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ].…”