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.

The effect of two housing systems during the fattening period on productive performance of lambs from different hair-type sheep breeds in southeastern Mexico was evaluated. Effects of housing system (raised-slatted floor cages (RFC) vs. floor pens (FP)), year (2009, 2012 and 2013) and season of the year (rainy vs. dry) on average daily gain (ADG), weights adjusted to 60 (P60) and 90 (P90) days post-weaning were evaluated. Data from 1213 lambs collected on the farm over a period of three years were analysed. The ADG, P60 and P90 were affected (P < .01) by the housing system, year and the housing system × year interaction. The season was not a significant source of variation. Lambs housed in RFC were heavier (ADG 306.5 ± 2.69 g, P60 33.2 ± 0.16 kg, P90 42.4 ± 0.24 kg) than those in FP (ADG 269.4 ± 4.24 g, P60 30.9 ± 0.25 kg, P90 39.0 ± 0.38 kg) (P < .01); however, the significant interaction housing system × year suggests that productive performance of lambs may vary between years, despite the housing system. It was concluded that productive performance of hair lamb was affected by housing systems, year and their interaction.

El objetivo del estudio fue describir los sistemas intensivos de engorda de corderos en el Estado de Yucatán, México. El estudio se desarrolló de marzo a junio de 2013. Se aplicó una encuesta a productores o responsables de 34 granjas, seleccionadas por conveniencia. La información fue analizada a través de tablas de frecuencias, medidas de tendencia central y análisis de varianza obtenidos con el paquete estadístico STATGRAPHICS® Centurion XV. Los resultados mostraron que los sistemas intensivos de engorda de corderos se diferencian básicamente por dos tipos de alojamiento: a) corrales a nivel del suelo (SICS) y b) corrales elevados con piso de rejilla (SICE). Los genotipos están formados por la cruza de razas Pelibuey, Dorper y Katahdin, principalmente (93.94 %). La alimentación se basa en la utilización de concentrados de marcas comerciales (47.06 %), elaborados en la granja (47.06 %) y elaborados por proveedores informales (5.88 %). El manejo sanitario consiste en la vacunación (79.41 %) y desparasitación de los animales (100 %). Se encontró, un mejor comportamiento productivo de los corderos de engorda en SICE comparado con aquellos de SICS. La venta de corderos en pie (91.18 %) es la principal fuente de ingresos económicos, con un precio de $29.75/kg. La mayoría de los productores (67.65 %) comercializan a sus animales en la unidad de producción. Es necesario hacer una evaluación prospectiva de los SICE y los SICS desde el punto de vista productivo y económico.

La engorda de corderos en corrales elevados con piso de rejilla permite que los animales se mantengan en un ambiente sano, con reducida exposición a los parásitos, protección de los depredadores, reducción en el gasto energético y una mejor comodidad durante las estaciones calurosas del año; sin embargo, poco se conoce sobre el comportamiento productivo de los corderos bajo este sistema de producción. La identificación y focalización de los factores específicos que pueden afectar el comportamiento productivo de los corderos de engorda en corrales elevados con piso de rejilla es crucial para mejorar la productividad. Además, su conocimiento es importante para lograr índices óptimos de producción, para incrementar la producción de los corderos durante la engorda. Se analizaron 882 datos de la ganancia diaria de peso post-destete (GDP), del peso corporal final (PCF) y de los días de engorda (DE) de corderos machos de cuatro granjas (granja A, 166; granja B, 122; granja C, 350; granja D, 244). El modelo estadístico incluyo los efectos fijos de la granja (A, B, C y D), del año (2010, 2011, 2012 y 2013) y de la época del año (lluvia y seca) sobre GDP, PCF y DE. Los datos del peso corporal inicial fueron utilizados como covariable. La GDP fue afectada por la granja y el año (P < 0.001), pero no por la época del año (P > 0.05). El PCF y DE fueron afectado por todos los factores evaluados (P < 0.001). En conclusión, el comportamiento productivo de corderos en corrales elevados en el trópico de México, es afectado por la granja, el año y parcialmente por la época del año. Los corderos engordados durante la época seca mostraron mayor PCF y DE que los corderos engordados durante la época de lluvia.

The aim of this review was to determine the influence of the housing type on the productive performance and welfare of lambs in intensive fattening systems. The available literature shows several housing types that differ by their position, either at ground level or elevated or from the bedding material used. Raised pens, per se, do not seem to improve the productive performance of the lambs. In addition, they negatively influence animal welfare. For these reasons, it is proposed to enrich the environment in these housing types without increasing costs and improving comfort for animals. In Mexico, contrary to other producing countries of sheep, there is a lack of scientific evidences of the suitable housing for fattening and finishing lambs in the different geographical zones of the country. The attention to this demand, in a multidisciplinary manner, would help to reduce the production problems, welfare issues and economic losses in a sustainable manner in the fattening of sheep in Mexico.

Objective. Predict the tissue carcass composition of “Blackbelly” lambs using in vivo and postmortem measurements. Materials and methods. Twenty lambs with an average age and weight of seven months and 29.07±2.88 kg, respectively, were used. Before slaughter, the subcutaneous fat thickness, depth, width and Longissimus dorsi muscle area were measured with ultrasonography. After slaughter, the cold carcass and tissues: muscle, fat and bone weight, were recorded. In the carcass, the thoracic depth, length, perimeter, length and width of the leg, as well as the compactness index, were also measured and recorded. Correlation analysis and regression models were used to predict tissue carcass composition. Results. The carcass tissues were correlated with L. dorsi muscle depth (p≤0.05; r-values ranged from 0.67 to 0.80) and carcass compactness index (p≤0.05; r ranged from 0.54 to 0.75). The r2 for the prediction equations of the carcass tissue composition ranged from 0.71 to 0.78 for fat (p≤0.001). Conclusions. The use of in vivo and postmortem measurements allowed the prediction of tissue carcass composition of lambs, with moderate to high accuracy (r2 >0.71≤ and ≤0.78).