Infrared Thermography to Evaluate Heat Tolerance in Different Genetic Groups of Lambs.

Heat stress is considered a limiting factor for sheep production. We used information from physiological characteristics linked to heat tolerance to determine whether infrared thermography temperatures were able to separate groups of animals and determine the most important variables in this differentiation. Forty-eight four-month-old male lambs from eight genetic groups were used. Physiological (rectal temperature-RT, heart rate-HR, respiratory rate-RR) and blood traits, infrared thermography temperatures, heat tolerance indices, body measurements, weight and carcass traits were measured. Statistical analyses included variance, correlations, factor, discrimination and regression. Observing the correlations between physiological characteristics (RT, RR and HR) with temperatures measured by infrared thermography, regions for further studies should include the mean temperature of flank, nose and rump. Results show that there are strong relationships between thermograph measurements and RR, RT and HR in lambs, which are suggested to be directly correlated with heat tolerance capacity of the different genetic groups evaluated in this study. The assessment of body surface temperature measured by the thermograph could be used as a noninvasive tool to assess heat tolerance of the animals.

Fatty acid profile of hair lambs and their crossbreds slaughtered at different weights.

This study aims to investigate the effect of breed and slaughter weight on fatty the acid profile of the Longissimus dorsi muscle in lambs. Twenty-four Santa Inês (SI), 24.5 Ile de France × 0.5 Santa Inês (Ile × SI) and 12.5 Texel × 0.5 Santa Inês (Te × SI), slaughtered at different weights (30, 35, 40, and 45 kg), were evaluated. The animals were reared with creep feeding to weaning and were feedlot finished, receiving a diet composed of 30% hay and 70% concentrate. The analyses of fatty acids were carried out on the Longissimus muscle of the 13th rib. The experiment was in a three by four factorial design. The total mean saturated fatty acid level was 44.88%, with 43.30% monounsaturated fats and 1.72% polyunsaturated. The major fatty acids found included oleic (43%), palmitic (22%), and stearic (18%). The concentration of desirable fatty acids varied from 61.56% to 66.78%, with Te × SI (66.78%) having the highest levels (P < 0.05). The slaughter weight affected (P < 0.05) the saturated and unsaturated (both mono and poly) fatty acid profiles. The 35-kg slaughter weight showed the most desirable fatty acid profile. The saturated myristic and stearic fatty acids decreased with an increase in the slaughter weight, but oleic acid increased. In the conditions of the present study, the meat from Santa Ines and Texel × Santa Ines lambs had fatty acid profiles more beneficial for human health due to the higher levels of unsaturated fatty acids.

Physical, chemical and sensorial parameters for lambs of different groups, slaughtered at different weights.

The object of this experiment was to study physicochemical and sensorial traits in the 11th and 13th ribs of 24 Santa Ines (SI), 24 1/2 Ile de France × 1/2 Santa Inês (ILE × SI) and 8 1/2 Texel × 1/2 Santa Inês (TE × SI), slaughtered at different weights (30, 35, 40 and 45 kg, respectively). Subjective measurements (marbling, colour and texture) were carried out on the Longissimus dorsi, as well as initial pH (0 h) and final pH (24 h) after slaughter. The experiment was in a 3 × 4 factorial design and analysed using general linear model and correlation procedures in SAS®. Breed group did not influence colour (3.32), shear force (3.57 kg-force (kgf)) or loss in cooking (24.05%) of the L. dorsi, but slaughter weight affected these, with stronger colour, tougher meat and greater loss in cooking as slaughter weight increased. For sensorial analysis, the L. dorsi were cut, identified and evaluated by 30 untrained judges using a linear scale. Significant differences were detected in preference (6.61 points), tenderness (6.32 points), succulence (6.33 points) and flavour (7.08 points) of the meat from different breed groups and slaughter weights. For preference, all meats were well accepted although the crossbred animals slaughtered at 45 kg were less acceptable.

Use of multivariate analyses for determining heat tolerance in Brazilian cattle.

Adaptability can be evaluated by the ability of an animal to adjust to environmental conditions and is especially important in extreme weather conditions such as that found in tropical Brazil. A multivariate analysis using physical and physiological traits in exotic (Nellore and Holstein) and naturalized (Junqueira, Curraleira, Mocho Nacional, Crioula Lageana, and Pantaneira) cattle breeds was carried out in the Federal District of Brazil to test and determine which traits are important in the adaptation of animal to heat stress as well as the ability of these traits and statistical techniques to separate the breeds studied. Both physical and physiological traits were measured on three occasions and included body measurements, skin and hair thickness, hair number and length, pigmentation, sweat gland area as well as heart and breathing rates, rectal temperature, sweating rate, and blood parameters. The data underwent multivariate statistical analyses, including cluster, discriminate, and canonical procedures. The tree diagram showed clear distances between the groups studied, and canonical analysis was able to separate individuals in groups. Coat traits explained little variation in physiological parameters. The traits which had higher discriminatory power included packed cell volume, shoulder height, mean corpuscular volume, body length, and heart girth. Morphological and physiological traits were able to discriminate between the breeds tested, with blood and size traits being the most important. More than 80% of animals of all breeds were correctly classified in their genetic group.

Use of heat tolerance traits in discriminating between groups of sheep in central Brazil.

The animal and its environment make up an integrated system, where each acts on the other. Tropical regions are characterized by high levels of solar radiation and environmental temperature which may adversely affect animal production. This study carries out a multivariate analysis of physical and physiological traits in sheep in the Federal District of Brazil to test the ability to separate groups of animals and determine which traits are most important in the adaptation of animal to heat stress. The variables studied included coat thickness, number and length of hairs, pigmentation of the skin and coat, number of sweat glands as well as heart and respiratory rates, rectal and skin temperatures, sweating rate, and blood parameters. Five groups of ten animals were used depending on breed (Bergamasca, crossbred, or Santa Inês) or coat color (Santa Inês--brown, white, and black). The data underwent multivariate statistical analyses including cluster, discriminate, and canonical, using Statistical Analysis System--SAS®. The tree diagram showed clear distances between groups studied and canonical analysis was able to separate individuals in groups, especially Bergamasca and white Santa Inês. The canonical correlation redundancy analysis showed that coat reflectance as well as hair length and number of hairs per unit area were the most useful in explaining changes in physiological traits. Skin and coat traits such as hair length, coat reflectance, percentage of epithelial area occupied by sweat glands, skin reflectance and thickness, as well as heart and breathing rates were the most important in separating these groups.

Multivariate analysis for characteristics of heat tolerance in horses in Brazil.

The environment in which the horse is reared affects its ability to maintain thermal balance which is in turn related to thermal characteristics and regulatory physiological mechanisms. In this study a multivariate analysis of physiological traits in relation to heat tolerance in horses was carried out in the Federal District, Brazil. The aim was to test the ability of these analyses to separate groups of animals and determine which physiological traits are most important in the adaptation to heat stress. Forty adult horses (4 to 13 years) were used, ten from each of four different genetic groups (English thoroughbred, Brazilian showjumper, crossbred and Breton). The traits examined included heart and breathing rate, rectal temperature as well as blood parameters. The data underwent multivariate statistical analysis including cluster, discriminate and canonical using Statistical Analysis System - SAS (R) procedures CLUSTER, STEPDISC, CANCORR and DISCRIM. The tree diagram showed clear distances between groups studied and canonical analysis was able to separate individuals in groups. The discriminate analysis identified the variables which were most important in separating these groups. The multivariate analysis was able to separate the animals into groups with RR, HR and RT being important in this separation.