Due to the conditions in which traditional sheep production systems operate, the evaluation of animal growth from live weight (LW) is limited by the high cost of the livestock scale as well as the sophisticated maintenance required. In this scenario, in recent years, biometric measurements have been investigated as an accurate indirect method to predict the LW of farm animals. Therefore, the present study was undertaken to examine different models for predicting the body weight of growing lambs using the body volume (BV) formula. Body volume, heart girth (HG) and body length (BL) data of 290 lambs aged between two and eight months were recorded. Body volume was calculated from HG and BL data using a formula that calculates the volume of a cylinder. The estimation of LW from the BV formula was achieved through regression equations using three mathematical models (linear, quadratic and exponential). The mean values of LW, HG, BL and BV of the lambs were 29.12±12.04kg, 70.00±11.69cm, 38.40±6.43cm and 23.93±9.90dm3, respectively. The correlation coefficient between LW and BV was r = 0.96 (P<0.001). The quadratic model showed the highest coefficient of determination (0.93) and the lowest prediction error (3.29kg). Under the experimental conditions adopted in this study, it is possible to predict the live weight of growing lambs using the body volume formula.

SUMMARY The Guajolote is a native North American poultry, originally domesticated in Mexico, from where it was exported to Europe, and from there to the rest of the world, becoming the genetic base of the breeds and varieties of turkeys that are known in the present. However, the phenotypic and productive characteristics of Guajolotes have been poorly studied, which has limited its racial recognition. This review describes the current knowledge on the historical distribution, morphological, morphometric and phaneroptic characteristics of Guajolotes, as well as the productive performance and quality attributes of Guajolote meat and eggs. Due to the long process of evolution, Guajolotes have a good capacity for adaptation and high rusticity that allows it to reproduce under different environmental and management conditions. It has unique morphological peculiarities and great variability in terms of its morphometric and phaneroptic descriptors. This bird has a marked sexual dimorphism in favor of males. Females are excellent natural incubators, they start laying from between 6 and 8 months of age, laying an average of 16.7 ± 3.6 eggs per laying season. Males have a good capacity to convert food into meat and can reach a live weight of between 5499 ± 148 to 5835 ± 173 g at week 30 of age, having a carcass yield of 79%. The nutritional quality of meat and eggs of Guajolote is even higher than that of chicken. In conclusion, Guajolotes are poultry with characteristics of high biological and productive value; however, better management strategies are required to maximize its genetic potential for the benefit of the food security of small and mid-size producers that depend on this poultry genetic resource.

Direct collection of biometric measurements (BM) from sheep is an expensive and stressful procedure for animals; instead, indirect and novel methods have recently been used. The objective of this study was to use digital image analysis (DIA) to predict biometric measurements of Pelibuey sheep as a non-invasive approach under on-farm conditions. Withers height (WH), body length (BL), body diagonal length (BDL), and rib depth (RD) were predicted in Pelibuey ewes using DIA. Images were taken from the left flank of 65 nonpregnant and nonlactating Pelibuey ewes using a digital camera and analyzed by DIA. The BM determined from both in vivo and by DIA presented positive and moderate (P < 0.05) correlation coefficients (r) of 0.43, 0.66, 0.73, and 0.75 for BL, BDL, WH, and RD, respectively. Regression equations from BM by DIA had determination coefficients (r2) of 0.19, 0.44, 0.54, and 0.56 for BL, BDL, WH, and RD, respectively. The equations developed were from low to moderate precision (r2 = 0.18 to 55), moderate to high accuracy with a bias correction factor (Cb > 0.69), and low to moderate reproducibility index (> 0.30). Overall, the use of DIA was able to predict the BM in Pelibuey ewes with low to moderate precision and accuracy. Factors affecting the accuracy and precision of this relationship should be further investigated.