Polymorphism in Calpain gene of registered Brahman cattle from Mexico

The present study was conducted to assess genotypic, allelic and haplotypic frequencies, in Brahman cattle in Mexico, of three single nucleotide polymorphism markers in the m -calpain gene, previously associated with beef tenderness in European, crossbred, and Zebu cattle (C316, C530, C4751).  Three allelic discrimination assays were designed for generation of the said frequencies.  The C316 marker showed a high frequency of the heterozygotic genotype (CG = 92%), and frequencies of these alleles were similar (54 and 46% for G and C, respectively).  By contrast, for C530, the main segregated genotype was the A alleles homozygote (98%).  For C4751, the heterozygotic genotype (CT) had the highest frequency (99%).  As to haplotypes, the most frequent compositions were GAT (50%) and CAC (45%).  These findings suggest that some favorable alleles for beef tenderness (C in 316 and C4751) are appreciably segregated in the Brahman population sampled. Thus, favorable homozygotic genotypes might be increased by integrated selection programs, including either the single marker or dual marker haplotype evaluation.  Further research is needed to determine relationships between meat quality traits (beef tenderness) and productive performance (current selection criteria), thus to promote consumption of Brahman beef and better position it in both national and international markets

ANÁLISIS DE CRECIMIENTO INICIAL DE CINCO GENOTIPOS DE BRACHIARIA EN TRÓPICO HÚMEDO

A study was conducted to evaluate the initial growth of five Bracharia varieties in the rainy season characteristic of the humid tropic prevalent in the Santo Domingo de los Tsáchilas Province, Ecuador. The evaluated genetic material were improved varieties of Bracharia brizantha (Piatá, Xaraés y Marandú), a hybrid (Mulato II) and the variety Brachiaria decumbens, considered the check because this is the more spread material in the region. The materials were randomly distributed in plastic bags and cultivated in the open to evaluate growth during the twelve weeks after seed emergency. Results indicate that the hybrid Mulato II has higher plant establishment potential (P<0.05) than B. decumbens. However, when the growth rate was evaluated, the Marandú variety was superior (P<0.05) from the beginning of the evaluation, which translates in a greater biomass gain per unit area. The rate of net assimilation (RNA) and the relative growth rate (RGR) has a declining trend in all varieties (P<0.05) through time, the hybrid Mulato II being the one which presented the lower RNA, probably due to a lower height and greater leaf area. Reported data demonstrates the importance of determining plant physiological efficiency in the environment where they are going to be cultivated to guaranty the productive efficiency of the pastures.Se condujo un estudio para evaluar el crecimiento inicial de cinco variedades de Brachiaria en la época de lluvia característica del clima tropical húmedo de la provincia de Santo Domingo de los Tásachilas, Ecuador. Los materiales genéticos evaluados fueron variedades mejoradas de Brachiaria brizantha (Piatá, Xaraés y Marandú), Brachiaria híbrido (Mulato II) y la variedad Brachiaria decumbens, considerada como testigo por ser la que prevalece en la zona en estudio. Las variedades fueron sembradas por semilla en fundas de plástico y colocadas a la intemperie para evaluar el crecimiento durante las doce semanas posteriores a la emergencia. Los resultados indican que el híbrido Mulato II tiene mayor potencial de establecimiento (P<0.05) que B. decumbens; sin embargo, cuando se estimó la tasa de crecimiento, la variedad Marandú fue superior (P<0.05) desde el inicio de la evaluación, ex presado por una mayor acumulación de biomasa por unidad de área. La tasa de asimilación neta (TAN) y la tasa relativa de crecimiento (TRC) mostraron un comportamiento descendente en todas las variedades (P>0.05) a lo largo del tiempo, siendo el hibrido Mulato II el que presentó la menor TAN, debido probablemente a la menor altura y mayor área foliar. Los resultados obtenidos demuestran la importancia de determinar la eficiencia fisiológica de las plantas forrajeras en el ambiente donde se van a cultivar, para garantizar la eficiencia durante el establecimiento de las praderas

Rendimiento y digestibilidad de forraje de cultivares de Urochloa spp. a tres edades de rebrote en épocas de lluvias y seca

The humid tropics of Ecuador is a potential livestock production area. Urochloa spp. cultivars are a forage option in this region. Environmental and management conditions determine forage yield and nutritional value and should be researched prior to establishing new forage species. An evaluation was done of total dry matter yield (TDM; t ha-1), morphological components proportions (%; leaf, stem, dead material and inflorescence) and in situ dry matter digestibility (DMD; g kg-1)) in five Urochloa cultivars (Mulato II, Marandú, Xaraés, Piatá and Señal [control]) and at three regrowth ages (4, 6 and 8 wk) during the rainy and dry seasons. A completely randomized block design in a split plot arrangement was used to analyze the data by season. During the rainy season, TDM did not differ (P>0.05) between cultivars. In the dry season, Marandú had a lower yield than Xaraés (0.92 vs 1.21 t ha-1). Morphological component proportions differed between cultivars (P0.05) en MST, entre cultivares evaluados. Durante la ESE Marandú presentó menor rendimiento que Xaraés (0.92 vs 1.21 t ha-1). La proporción de componentes morfológicos fue diferente entre cultivares (P<0.05) y las hojas fueron el componente que más contribuyó al rendimiento. La DISMS se redujo de 64 a 56 % y de 60 a 56 %, cuando el forraje se cosechó a 4 y 8 semanas durante la ELL y ESE, respectivamente. Los cultivares evaluados mostraron rendimientos aceptables de MST, 2.6 y 1.0 t ha-1 y DISMS, 602 y 574 g kg-1, durante la ELL y ESE, respectivamente; por lo que pueden ser una alternativa forrajera para la ganadería del trópico húmedo de Ecuador

Milk production of Suiz-Bu, a dual purpose cattle breed in the Mexican tropics

El objetivo del presente trabajo fue determinar el efecto de factores ambientales sobre la producción de leche de vacas Suiz-Bú en las condiciones del trópico mexicano. Se analizaron los registros de producción de leche de 728 vacas con información disponible de los años 2012 al 2014. Las vacas se ordeñaban dos veces al día a partir del quinto día posparto y eran alimentadas bajo condiciones de pastoreo y suplementación con concentrado comercial. Las variables producción de leche a 305 días (PL305) y media de producción diaria (MPD) fueron analizadas con un modelo mixto que incluyó efectos de número de lactancia (NL), año de parto (AP), época de parto (EP) y las interacciones simples. El año de parto fue estadísticamente significativo para PL305 y PMD que aquellas que parieron en época seca (p&lt;0.05), y las vacas de primer parto tuvieron una menor PL305 que vacas con dos o tres lactancias (p&lt;0.05). Asimismo, los efectos de las interacciones fueron significativas (p&lt;0.05).

Genetic improvement of sheep production by crossbreeding strategies with hair sheep breeds

The objective is to propose crossbreeding strategies with hair sheep breeds to improve meat production in Mexico. Two crossbreeding schemes are presented that can provide solutions to the problem of intensive use of several breeds in unplanned crosses that has occurred in some flock. The starting point of the first scheme is a hybrid base population (hair sheep x Dorper) in which the breed proportions are unknown, by using two hair sheep breeds alternatively as maternal lines and Dorper as paternal line. The second scheme aims to develop a hybrid or synthetic breed ⅝ Charollais ⅜ hair sheep. For purposes of this discussion the two hair sheep breeds Blackbelly and Pelibuey will be used along with Charollais as the meat-type breed in the understanding that any suitable breed may be used to achieve the objectives of a particular production system

Genética General

La presente obra está dirigida a estudiantes de nivel medio superior y superior, y pretende ser la base del aprendizaje sobre genética para estudiantes de niveles avanzados. El lenguaje sencillo y cotidiano utilizado permitirá al lector un panorama general sobre la Genética, la ciencia del estudio de las leyes de la herencia y variación tanto en plantas como en animales

Frequency and association of polymorphisms in CSN3 gene with milk yield and composition in Saanen goats/Frecuencia y asociación de polimor smos en gene CSN3 con producción y composición de la leche de cabras Saanen

K-casein (CSN3) gene is of particular interest in goat production due to the e ect of its polymorphisms on milk quality and composition. The objective of this study was to assess the genotypic and allelic frequencies in CSN3 gene in the Saanen goat breed and its e ect on milk production and some of its compositional traits. Allelic discrimination assays were designed to determine the variants (A, B or C) using qPCR and allelic discrimination method. Allelic frequencies for A, B and C were 0.23, 0.64 and 0.13, respectively. Association analysis indicated that the CSN3 was signi cantly associated only with protein percentage (p = 0.006). Results indicated that animals with AC, BB and CC genotypes showed higher milk protein percentage than those with genotype AB. This evidence suggests that genotypes favorable to this associated trait could be included into Saanen goat breeding strategies