Coat and skin morphology of hair sheep breeds in an equatorial semi-arid environment

This study aims to address if are there annual changes in the hair coat traits and skin morphology of hair sheep breeds raised in an equatorial semi-arid region? Coat and skin samples were taken from thirty Morada Nova (4 ± 2 years old; red coat; ±SD) and twenty Santa Inês multiparous ewes (5 ± 2 years old; brown and black coat; ±SD) every 3 months over a year. Hair coat traits included thickness (mm), density (number of hairs cm^-2), length (mm), and diameter (mm), plus epidermal and dermal thickness (μm), sweat glands and blood capillaries area (μm cm^-2) were determined. Means of solar irradiance and ambient air temperature were higher between September and December. Annual changes (P < 0.05) in hair density, diameter, length and thickness, as well as the skin blood capillaries and sweat gland area differed between breeds. The modifications on hair coat traits resulted in minor changes on the effective thermal conductivity of the hair coat surface both for Morada Nova and Santa Ines sheep. Nevertheless, it was clearly evident that the overall cutaneous thermal insulation for Morada Nova sheep was lowest in September that was coupled with lower hair density, coat thickness, and higher sweat gland and blood capillary area (P < 0.05). In conclusion, even in an equatorial region, phenotypic acclimatization on morphological traits of cutaneous surface and skin traits can modify the overall thermal insulation of sheep breeds.

Supplementation of diets with glutamine and glutamic acid attenuated the effects of cold stress on intestinal mucosa and performance of weaned piglets

In this study we investigated the effect of glutamine and glutamic acid inclusion in the diet of weaned piglets subjected to cold stress and thermoneutral environment. Sixty-four weaned piglets were assessed from 28 to 65 days of age. A completely randomised design consisting of a 2 × 2 factorial arrangement was tested – environments (thermoneutral and cold stress) and diets (control and L-glutamine + L-glutamic acid (G + GA)). Performance, relative organ weight and carcass yield, and morphology of the intestinal mucosa were assessed. Supplementing the diets with G + GA reduced feed intake under both environments. This was associated with a decline in growth rate for piglets in the thermoneutral environment but not in the cold environment (P &lt; 0.002). Feed efficiency was lower for piglets offered the control diets in the cold environment, but was significantly improved (24.6%) by G + GA supplementation in the cold but not the thermoneutral environment (P &lt; 0.001). G + GA supplementation decreased small intestinal length and altered intestinal morphology with the highest villus/crypt depth ratio observed in piglets offered the G + GA supplemented diet in the cold environment. In summary, glutamine and glutamic acid diets mitigated the effects of cold stress on the intestinal mucosa and performance of weaned piglets.

The use of simple physiological and environmental measures to estimate the latent heat transfer in crossbred Holstein cows

The aim of the present study was to estimate the heat transfer through cutaneous and respiratory evaporation of dairy cows raised in tropical ambient conditions using simple environmental and physiological measures. Twenty-six lactating crossbred cows (7/8 Holstein-Gir) were used, 8 predominantly white and 18 predominantly black. The environmental variables air temperature, relative humidity, black globe temperature, and wind speed were measured. Respiratory rate and coat surface temperature were measured at 0700, 0900, 1100, 1300, and 1500 h. The environmental and physiological data were used to estimate heat loss by respiratory (E_R) and cutaneous evaporation (E_C). Results showed that there was variation (P < 0.01) for respiratory rate depending on the times of the day. The highest values were recorded at 1100, 1300, and 1500 h, corresponding to 66.85 ± 10.20, 66.98 ± 7.80, and 65.65 ± 6.50 breaths/min, respectively. Thus, the amount of heat transferred via respiration ranged from 19.21 to 29.42 W/m². There was a variation from 31.6 to 38.8 °C for coat surface temperature; these values reflected a range of 55.52 to 566.83 W/m² for heat transfer via cutaneous evaporation. However, throughout the day, the dissipation of thermal energy through the coat surface accounted for 87.9 % total loss of latent heat, and the remainder (12.1 %) was via the respiratory tract. In conclusion, the predictive models based on respiratory rate and coat surface temperature may be used to estimate the latent heat loss in dairy cows kept confined in tropical ambient conditions.