Do newborn lambs with black and white hair-coats in an equatorial semi-arid environment maintain homeothermy?

We assessed newborn lambs from two hair-coat sheep breeds, the black Santa Ines (n = 29) and white Dorper (n = 26), to determine how they behaviourally and physiologically respond to the prevailing thermal conditions in an equatorial semi-arid environment. Measurements of hair-coat surface temperature, rectal temperature and the lambs' exposure to sun were recorded across the first 24 h of life every hour, after the lambs had received colostrum. Lambs and ewes were kept in a lambing pen and could freely move between a shaded area or be exposed to sun. During the study period, the air temperature ranged between 20 ºC and 34 ºC. When exposed to sun, lambs and ewes could experience as much as 1200 W m-2 of solar irradiance. Santa Ines lambs exhibited higher (highest density interval at 95%, HDI) hair-coat surface temperatures than did Dorper lambs. Overall, both Santa Ines and Dorper lambs sustained homeothermy, with a mean rectal temperature ranging from 38.7 ºC to 39.1 ºC between night and daytime phase, and a mean amplitude of ~ 0.8 ºC. Nevertheless, from 10:00 to 15:00, some lambs were found to be moderately hyperthermic. Five Santa Ines and three Dorper lambs had rectal temperatures above 40 ºC, and one Santa Ines lamb, while exposed to sun, had a rectal temperature of 41.3 ºC. Over this time period, lambs were more likely to move to shade (HDI at 95%). From 00:00 to 06:00, despite the air temperature being lower than the hair-coat surface, favouring high rates of sensible heat loss to the environment, no lamb exhibited signs of hypothermia (rectal temperature < 37.5 ºC). In conclusion, haired newborn lambs coped well with high levels of radiant heat during the daytime and lower temperatures at night. However, providing access to shade during the daytime is important to improve the welfare of newborn lambs delivered in equatorial semi-arid regions.

Influence of the climatic environment and duration of labor on the mother-offspring interaction in Morada Nova sheep.

The objective of this study was to confirm the influences of stress from labor and climate on the formation of the mother-offspring bond in Morada Nova sheep in the first 2 h after delivery or at the moment of the first suckling of the newborn. The data were collected from 80 Morada Nova ewes (25 primiparous and 55 multiparous) and their lambs in 2 periods of the year. On the basis of the average length of parturition and the black globe temperature-humidity index (BGTHI) at the time of the birth, the ewes were grouped into 3 classes corresponding to the length of parturition, classified as short (less than 15 min), medium (between 15 and 30 min), or long (more than 30 min). Similarly, the BGTHI at the moment of birth was classified into 1 of 3 ranges: low (less than 65), intermediate (greater than 65 but less than 80), and high (greater than 80). For the characterization of mother-offspring behavior, evaluations were performed in the first 2 h after birth or until the moment of the first suckling of the newborn. Maternal factors such as maternal grooming, facilitating sucking, frequency of low-pitched bleats, and latency to groom were recorded. For the lamb, attempts to seek the udder, the frequency of low-pitched bleats, latency to first reaction, latency to stand, and latency to suckle were recorded. The lambs were slower (P < 0.05) to stand and suckle when they were born in conditions of a BGTHI below 65. The latencies to stand and suckle were greater (P < 0.05) in newborn lambs born during labor that took more than 30 min. For maternal behaviors, activities such as maternal grooming and the facilitation of suckling were greater (P < 0.05) during the time periods with higher bioclimatic index values. Moreover, the dams cleaned or licked (maternal grooming) the newborns for a lower percentage of time (P < 0.05) when the labor lasted longer than 30 min. From the present study, it can be concluded that newborn Morada Nova lambs are slower to stand and suckle when born under BGTHI conditions below 65. Furthermore, prolonged labor harms the mother-offspring bond, especially in terms of the dam's ability to clean (maternal grooming) her lamb's body and facilitate its first suckling.