ABSTRACT The effect of including partially dehulled sunflower seeds in the diet of grazing chickens in meat quality was evaluated. Two hundred and forty, one-day-old, Ross 308 chickens were used, randomly distributed into four treatments with six replicates of 10 birds each. Seventy-two birds were slaughtered at seven weeks of age, 18 per treatment, extracting the Pectoralis major muscle to analyze meat quality. The treatments were completely randomized in a 2x2 factorial arrangement, where type of rearing (confinement or grazing) and diet (base diet or base diet substituting 10% soybean meal for partially dehulled sunflower seeds) were the independent variables. The grazing chickens spent 8 hours a day in a white clover (Trifolium repens) paddock. Including sunflower seeds improved (p<0.05) the color and crude protein (CP) in breast meat (p<0.05), while grazing increased (p<0.05) CP, dry mater (DM), and shear force (SF), and the percentage of breast fat decreased (p<0.05) by up to 50%. Additionally, grazing increased (p<0.05) saturated fatty acids (SFA) and reduced (p<0.05) lipid oxidation by up to 50%. Partially replacing soybean meal with partially dehulled sunflower seeds in the diet of grazing chickens with white clover improves the physicochemical characteristics and nutritional quality of the breast meat; it also decreases lipid oxidation, extending the shelf life of the meat.

Tannins are polyphenolic compounds with some beneficial properties for ruminants as they act as antioxidants, antimicrobials, and anthelmintics, which may improve animal performance. However, the results are variable, depending on the type, source, and dose. The objective of this research was to determine the effect on fattening performance and carcass characteristics of lambs supplemented with condensed tannins (CTs) from Acacia mearnsii extract. Thirty-six, three-month-old Dorset x Hampshire cross lambs of 20.8 ± 3.3 kg live weight were used in a completely randomized design with four treatments (n = 9), namely T1: basal diet, 0.0 g CT/kg DM-1; T2: T1 + 1.75 g CT/kg DM-1; T3: T1 + 3.5 g CT/kg DM-1; and T4: T1 + 5.25 g CT/kg DM-1. The daily weight gain was higher in T2 and T3 than in T1. The weight at slaughter and empty weight at slaughter were higher in T2 than in T1. The hot carcass weight was higher in T3 than in T1, but no different from T2 or T4. The hot carcass yield was higher in T3 than in the other treatments. The meat pH at slaughter and 24 hours postmortem was higher in T4 than in T1 and the meat protein percentage was higher in T3 than in T1. The inclusion of CTs from Acacia mearnsii extract in the diet of fattening lambs increased their daily weight gain, yield, and carcass weight.

The objective of this study was to evaluate the available variability in 21 Brachiaria humidícola genotypes with respect to protein concentration and dry matter production, during the dry season of the year. The study was carried out during the March, April and May months of the years 2004 and 2005, with neither watering nor fertilising of the soil. Three harvests were obtained per genotype each year, with a regrowth period that varied from 33 to 35 d between harvests. The experiment was established under a completely randomised design in a split split-plot arrangement. Results showed an important among-genotype variability (p < 0.0001) for protein concentration within the year, that varied from 101.1 to 119.5 g kg-1 of MS, for the 26 160 and 26 413 genotypes, respectively. The 26 413 and 16 891 genotypes recorded the greatest protein concentrations although not significantly above (p > 0.05) those of the 679 genotype (commercial Humidícola). Moreover, protein concentration presented an important stability in the environment with no interaction with the year or the harvest date (p > 0.05). On the other hand, an inverse relationship was observed between protein concentration and dry matter production: For this reason, a decrease in protein concentration was observed in the harvest material with the greatest dry matter production. This decrease is explained through a decrease in the proportion of leaves in the total aerial biomass of the plant.

El objetivo del presente estudio fue evaluar la variabilidad disponible en 21 genotipos de Brachiaria humidícola en cuanto a la concentración de proteína y producción de materia seca, durante la época seca del año. El estudio se realizó durante los meses de marzo, abril y mayo de los años 2004 y 2005, sin aplicar riego ni fertilizante al suelo. Se realizaron tres cosechas por genotipo en cada año, con un tiempo de rebrote de cada cosecha que varió de 33 a 35 d. El experimento fue establecido bajo un diseño de bloques completos al azar en arreglo de parcelas subdivididas. Los resultados mostraron una importante variabilidad entre los genotipos (p < 0.0001) para la concentración de proteína dentro del año, la cual varió de 101.1 a 119.5 g kg-1 de MS, valores que corresponden a los genotipos 26 160 y 26 413. Los genotipos 26 413 y 16 891 fueron los que presentaron las concentraciones de proteína más elevadas pero, sin ser significativamente superiores (p > 0.05) al genotipo 679 (Humidicola comercial). Además, la concentración de proteína mostró una estabilidad importante al ambiente al no interactuar ni con el año ni con la fecha de corte (p > 0.05). Por otra parte, la concentración de proteína mostró una relación inversa con la producción de materia seca, razón por la cual se observó una disminución en la concentración de proteína en los cortes con mayor producción de materia seca, explicada esta disminución por un decremento de la proporción de hojas en la biomasa aérea total de la planta.

A high production of crossbreed Brown Swiss x Zebu bullocks exists in the damp tropical regions of Mexico, and in spite of its economic importance, there is little information on the characteristics and yield of the carcasses obtained. The purpose of this study was to evaluate the yield of the carcass and non meat components of the bullocks reared in three feeding systems in a damp tropical climate. Thirty one bovines were used: 11 under extensive grazing (PE), 10 under grazing + a complement (PS) and 10 in a dry feed-lot (EC). Measured variables were live weight (PV), empty body weight (PVC), carcass yield (RC), consumable and non consumable body components yield, gastrointestinal tract content (CGI), dorsal fat thickness (EGD) and marbling. PV was similar in all rearing systems (419.4, 423.6, 414.4 kg for PE, PS and EC, respectively). The bullocks reared in EC were younger (P < 0.05), had more EGD (4.2 mm; P < 0.05), a greater PVC (90.9%; P < 0.05) and a lower CGI (9.04%; P < 0.05). Carcasses did not present marbling (P < 0.05) in the three feeding systems (P > 0.05). The bullocks reared in EC presented the greatest percentages of skin, feet and respiratory tract (9.5, 2.4 and 1.4 %, respectively). It can be concluded that producing bullocks in EC improves their carcass characteristics and increases the thickness of dorsal fat. The feeding system affected the gastrointestinal tract weight and the carcass yield, but not the non meat components yield.

Suizo Pardo x Cebú, y a pesar de su importancia económica poco se conoce sobre el rendimiento y las características de las canales obtenidas. El objetivo de estudio fue evaluar el rendimiento de la canal y de los componentes no cárnicos de toretes criados en tres sistemas de alimentación en clima cálido húmedo. Se utilizaron 31 toretes: 11 de pastoreo extensivo (PE), 10 de pastoreo + suplemento (PS) y 10 de engorda en corral (EC). Las variables de respuesta fueron peso vivo (PV), peso vacío del cuerpo (PVC), rendimiento de la canal (RC) y de los componentes consumibles y no consumibles, contenido del tracto gastrointestinal (CGI), espesor de grasa dorsal (EGD) y marmoleo. El PV fue similar entre los sistemas de crianza evaluados (419.4, 423.6, 414.4 kg en PE, PS y EC, respectivamente). Los toretes finalizados en EC presentaron mayor EGD (4.2 mm; P < 0.05), mayor porcentaje de PVC (90.9%; P < 0.05) y menor CGI (9.04%; P < 0.05). Las canales no mostraron marmoleo en los tres sistemas de alimentación (P > 0.05). Los animales de EC presentaron los mayores porcentajes de piel, patas y aparato respiratorio (9.5, 2.4 y 1.4 %, respectivamente). Se concluye que el sistema de EC mejora el terminado de la canal e incrementa el espesor de la grasa de cobertura. El sistema de alimentación afectó el peso del contenido gastrointestinal y el rendimiento de la canal, pero no modificó el rendimiento de los componentes no cárnicos.

The aim of this study was to evaluate the influence of age at first mating on the reproductive performance of Pelibuey ewe lambs. The study consisted of two trials: postweaning growth and reproductive handling. Twenty Pelibuey ewe lambs were used which were fed a complete diet throughout the study. In the first trial, the studied variable was the type of birth (TN). Body weight (PV) and daily weight gain (GDP) were studied during 42 days. The TN did not influence (P > 0.05) PV, GDP and age of the ewe lambs at 28 kg PV. In the second trial, the studied variable was the age of the ewe lamb at 28 kg PV: YOUNG (139 days) vs MATURE (169 days). PV and ewe lambs in estrus (%) were studied. In the MATURE group, a 43% (6/13) of ewe lambs in estrus were detected, whereas in the YOUNG group there were no ewe lambs in estrus (0/7). It was concluded that the type of birth of the ewe lambs had no effect on the postweaning growth performance nor the starting age for reproductive handling at a determined body weight. The starting age for reproductive handling of ewe lambs had an important effect on estrus detection, and there was a high ratio of reproductive failure in young ewe lambs.

El objetivo del estudio fue evaluar la influencia de la edad al primer apareamiento sobre la eficiencia reproductiva de las corderas Pelibuey. El estudio se dividió en dos ensayos, crecimiento postdestete y manejo reproductivo. Se utilizaron 20 corderas Pelibuey. Las corderas se alimentaron con una dieta integral durante todo el estudio. En el primer ensayo, el factor de estudio fue el tipo de nacimiento (TN). Se evaluó el PV y la ganancia diaria de peso (GDP) durante 42 días. El TN no influyó (P > 0,05) el PV, GDP y edad a la que las corderas alcanzaron 28 kg P V. En el segundo ensayo, el factor de estudio fue la edad de las corderas al alcanzar los 28 kg: JOVEN (139 días) vs MADURA (169 días). Las variables evaluadas fueron: PV y corderas en estro (%). En el grupo MADURA se detectó un 43% (6/13) de corderas en estro. Mientras que en JOVEN no se detectaron corderas en estro (0/7). Se concluye que el tipo de nacimiento de las corderas no influyó sobre su eficiencia de crecimiento postdestete, ni sobre la edad a la que estas inician el manejo reproductivo a un peso fijo. La edad con la que inician el manejo reproductivo las corderas tiene un efecto importante sobre la detección del estro, en donde la mayor proporción de fallas reproductivas se presentan en corderas jóvenes.