Opportunities and challenges from the use of genomic selection for beef cattle breeding in Latin America

In 2009, Latin American countries had approximately 401 million cattle (29% of the world’s total cattle population) and produced 8.2 million tonnes of beef, equivalent to 29% of the world’s total production (FAO, 2011). Beef in Latin American countries is produced under widely differing climates (ranging from tropical to temperate), resources available (vegetation, food), types of markets, and genetic backgrounds of the animals. The main production systems are classified as beef and dual-purpose cattle. The genetic backgrounds of animals vary from purebred European (Bos taurus taurus) or Zebu (Bos taurus indicus) to crossbreeds (Figures 1 and 2). Beef production systems may also be characterized by their management intensification levels as grazing only, grazing with food supplementation, and feedlot production. The main beef-producing countries are Brazil (51.6% of the total Latin American beef production), Argentina (18.5%), Mexico (9.4%), and Colombia (5.1%). Other countries contributing more than 1% of the total regional production are Uruguay, Venezuela, Paraguay, Bolivia, Ecuador, and Chile (Table 1). Latin America is a region of the world that can significantly increase its production in response to beef demand. Brazil has a mature beef cattle industry based on grass-fed cattle, in which feeding B. taurus indicus cattle, especially the Nellore breed, is a common practice. Over the last 8 years, beef production in Brazil has become one of the most important activities for employment and wealth creation. Foot-and-mouth disease issues are still a factor limiting the increase in Latin American beef exports (Ferraz and de Felício, 2010; Domingues Millen et al., 2011). Only a few Latin American countries, including Chile and Mexico, have the status of being free of this disease without vaccination. In most countries, the disease is controlled using a combination of free areas without vaccination and areas with vaccination. Other countries with a strong B. taurus indicus background in their beef cattle populations are those with large tropical areas dedicated to beef cattle production, such as Colombia, Venezuela, and Paraguay. Beef production in Argentina, Chile, Uruguay, and some portions of Brazil and Mexico is based mainly around the production of B. taurus taurus cattle (Peel et al., 2010; Arelovich et al., 2011; Domingues Millen et al., 2011). The Mexican beef cattle industry consists of 2 nearly separate market components. Beef producers in the northern part of Mexico have largely focused on the production of calves for export to the United States (Galyean et al., 2011). European beef genetics have been widely used in the region, beginning with importations of Hereford cattle and continuing with today’s popularity of Angus and Brangus along with several continental breeds, such as Charolais and Simmental. The central and southern regions of Mexico have historically produced grass-fed beef for the national market as well as dual-purpose dairy-Zebu crossbred cattle to produce milk and beef (Peel et al., 2010). Currently, breeding programs for the genetic evaluation of beef cattle in Latin America are based on statistical analyses in which performance and pedigree information are integrated. These analyses are based on a mixed model methodology, in particular the animal model statistical approach using best linear unbiased prediction methods to obtain estimated breeding values (EBV) for economically important traits. This methodology for obtaining EBV has been set up in Argentina, Brazil, Colombia, Mexico, Uruguay, Venezuela, and other countries. It has been established for specific purebred populations and also for some crossbred populations, such as multibreed populations with a dual purpose (beef and milk) in the Latin American humid tropics, which involve animals crossbred between B. taurus taurus and B. taurus indicus and composite breeds. Most programs focus on evaluating growth and reproductive traits, although a few have included longevity (stayability), heifer pregnancy, conformation, and carcass and meat quality traits

Genomic variability in Mexican chicken population using Copy Number Variation

Copy number variants (CNVs) are polymorphisms which influence phenotypic variation and are an important source of genetic variability [1]. In Mexico the backyard poultry population is a unique widespread Creole chicken (Gallus gallus domesticus) population, an undefined cross among different breeds brought to Mexico from Europe and under natural selection for almost 500 years [2-3]. The aim of this study was to investigate genomic variation in the Mexican chicken population using CNVs.A total of 256 DNA samples genotyped with Axiom® Genome-Wide Chicken Genotyping Array were used in the analyses. The individual CNV calling, based on log-R ratio and B-allele frequency values, was performed using the Hidden Markov Model (HMM) of PennCNV software on the autosomes [4-5]. CNVs were summarized to CNV regions (CNVRs) at a population level (i.e. overlapping CNVs), using BEDTools.The HMM detected a total of 1924 CNVs in the genome of 256 samples resulting, at population level, in 1216 CNV regions, of which 959 gains, 226 losses and 31 complex CNVRs (i.e. containing both losses and gains), covering a total of 47 Mb of sequence length corresponding to 5,12 % of the chicken galGal4 assembly autosome. A comparison among this study and 7 previous reports about CNVs in chicken was performed, finding that the 1,216 CNVRs detected in this study overlap with 617 regions (51%) mapped by others studies. This study allowed a deep insight into the structural variation in the genome of unselected Mexican chicken population, which up to now has not been never genetically characterized with SNP markers. Based on a cluster analysis (pvclust – R package) on CNV markers the population, even if presenting extreme morphological variation, does not resulted divided in differentiated genetic subpopulations. Finally this study provides a CNV map based on the 600K SNP chip array jointly with a genome-wide gene copy number estimates in Mexican chicken population.

Embryo development after ICSI, using spermatozoa from bovine testicular tissue treated with three membrane-destabilizing agents

ABSTRACT Objective: To determine differences in embryo development of bovine oocytes fertilized by frozen/thawed spermatozoa (F/T), or by intracytoplasmic sperm injection (ICSI) using F/T or spermatozoa from fresh (FTT) or cryopreserved testicular tissue (CTT) using three spermatozoa membrane destabilizers. Methods. Treatment (TRT) 1- In vitro fertilization (FIV) with F/T, TRT-2 ICSI with F/T, TRT-3 ICSI with FTT, TRT-4 ICSI with CTT. The spermatozoa membranes were destabilized using Triton X-100 (TX), Lysolecithin (LL) or Heparin--Glutathione (Hep-GSH). Embryo cleavage at 48 h and grade 1 and 2 blastocyst on day 8 post fertilization were recorded. The comparison among main effect means were analyzed based on the least significant difference of Fisher. Results. At D8 there was no difference in percentage of blastocyst formation among ICSI TRTs (F/T 13 ± 3, FTT 6 ± 3 and CTT 6 ± 3 p>0.05), but they were lower than control (FIV 23 ± 5). With Hep-GSH destabilizer, there was a lower cleavage at 48 h than the LL and TX (35± 5, vs 50± 5 and 56± 5 p<0.05). Cleavage at 48 h was better for the ICSI with F/T and LL, while for D8, the best percentage to blastocyst was for TX. Conclusion. It is possible to produce blastocysts using ICSI with spermatozoa obtained from fresh or cryopreserved testicular tissue. Sperm cells treated with TX or LL produced more BL than those treated with Hep-GSH. More experiments using spermatozoa obtained from different sources are necessary to improve embryo development after ICSI. Keywords:  ICSI, Vitrification, Testicular tissue, Oocytes, Bovine, Fertilization.R Objective. To determine the differences in the embryo development of bovine oocytes fertilized with frozen/thawing (F/T) spermatozoa or with the intracytoplasmic sperm injection (ICSI) of F/T, spermatozoa from fresh testicular tissue (FTT), and cryopreserved testicular tissue (CTT), using three spermatozoa membrane-destabilizing agents. Methodology. Four treatments were used. Treatment (TRT-1): In vitro fertilization (IVF) with F/T. TRT-2: ICSI with F/T. TRT-3: ICSI with FTT. TRT-4: ICSI with CTT. The spermatozoa membranes were destabilized with Triton X-100 (TX), Lysolecithin (LL), and Heparin-Glutathione (Hep-GSH). Embryonic division was recorded at 48 h and grade 1 and 2 blastocysts (BL) were recorded 8 days (D8) after the fertilization. The means were compared using Fisher’s least significant difference method. Results. At D8, the blastocysts formation between ICSI treatments (F/T 13 ± 3, FTT 6 ± 3, and CTT 6 ± 3, p>0.05) were lower than control (IVF 23 ± 5). There was a lower cleavage at 48 h using Hep-GSH than when LL and TX were used (35 ± 5 vs 50± 5 and 56± 5, p<0.05). Embryo division at 48 h obtained better results with the ICSI + F/T and LL treatment, while the highest blastocyst percentage at D8 was obtained using TX. Conclusions. Blastocysts can be produced through ICSI, using spermatozoa from fresh or cryopreserved testicular tissue. The spermatozoa treated with TX and LL produced a higher percentage of BL than the spermatozoa treated with Hep-GSH. Further experiments should be carried out using spermatozoa obtained from different sources, in order to improve embryo development after the ICSI

Análisis genético para vida productiva en ganado Holstein de México

Se usó la metodología de análisis de supervivencia con un modelo de riesgos proporcionales de Weibull para estudiar la duración de vida productiva funcional (DVPF) de ganado Holstein en México, usando un modelo padre-abuelo materno con el software Survival Kit V3.12. La DVPF se calculó como el número de días entre la fecha de primer parto y la fecha de desecho o censura, con un crédito máximo de 305 días por lactación. Los datos analizados se obtuvieron de la Asociación Holstein de México. El archivo final constó de 36,507 registros para DVPF de vacas que parieron por primera vez entre 1995 y 2008. El modelo incluyó la función de riesgo basal de Weibull y los siguientes efectos fijos: edad al primer parto, número de lactación por fase de lactación con cortes en los días 29, 249 y 305 y nivel de producción estandarizado con 10 clases con cambios en cada lactación, incluidas como variables tiempo dependientes y los efectos aleatorios de hato-año de parto y efectos genéticos de padre y abuelo materno. El porcentaje de censura fue de 25.54 %. Todos los efectos fijos analizados fueron significativos (P<0.0001) y tuvieron una influencia importante en el riesgo de desecho de los animales. Las heredabilidades calculadas en escalas logarítmica, original, efectiva y equivalente resultaron de 0.08, 0.13, 0.12 y 0.10 respectivamente, indicando que este carácter se puede integrar efectivamente a los programas de mejoramiento genético como se ha hecho en otras poblaciones de ganado Holstein

Genetic parameters for scrotal circumference, frame score and yearling weight of Mexican Charolais and Charbray young bulls

Abstract Background: Knowledge of genetic correlations and the economics of traits are essential to decide which traits should be used as selection criteria. Objective: To estimate heritabilities and genetic, environmental, and phenotypic correlations, and direct (DRS) and correlated (CRS) responses to selection by scrotal circumference (SC), frame score (FS), and yearling weight (YW) of Mexican Charolais (CH), and Charbray (CB) young bulls. Methods: Actual SC, height and YW records (10,078 for CH, and 500 for CB) were adjusted to 365 d. The 0.0505 adjustment factor recommended by the Beef Improvement Federation was used to obtain the 365-d adjusted SC for both breeds. Height and age records were used to obtain FS. Data were analyzed using a three-trait animal model. The animal model for each trait included bull breed, contemporary group (groups of young bulls born in the same herd, year, and season of the year), and age of dam as a linear covariate as fixed effects, and direct additive genetic and residual as random effects. Results: Heritability estimates for SC, FS and YW were 0.21 ± 0.04, 0.25 ± 0.04, and 0.29 ± 0.04, respectively. The genetic correlation between YW with SC was 0.37 ± 0.16, and between YW with FS was 0.42 ± 0.16. The estimate of genetic correlation between SC and FS was low and positive (0.15 ± 0.14). The DRS was 0.38 cm, 0.18 units, and 8.30 kg for SC, FS and YW. The CRS was 0.16 cm, and 0.08 units for SC and FS from indirect selection on YW. Conclusions: Direct selection for YW is expected to be effective. Indirect selection for SC and FS based on YW would not be expected to be as effective as direct selection for improving SC and FS

Efecto del riego sobre la calidad, desarrollo y producción de biomasa a dos edades de corte en Cenchrus purpureus vc. CT-115 para la región central del estado de Veracruz

En un diseño en bloques al azar con arreglo factorial 2 x 2, se estudió la calidad, desarrollo y acumulación de biomasa del pasto Cenchrus purpureus vc. CT-115. Los tratamientos consistieron en aplicación o no de riego durante el periodo seco, con un corte a 56 y 98 días. Se midieron el largo del tallo (cm), largo de hoja (cm), largo y grosor del segundo entrenudo (cm) y los rendimientos tMSha-1 totales, y de hojas y tallos, así como los porcentajes de PC (proteína cruda), FDA (fibra detergente ácido), FDN (fibra detergente neutro) y lignina en hoja. No se encontraron interacciones entre edad y riego para ninguna de las variables. El rendimiento de hojas, tallos y total fue mayor (P = 0.0001) cuando se aplicó riego y se cortó a los 98 días. Los indicadores: largo del tallo y hojas, grosor del tallo y largo de los entrenudos, fueron mejores cuando se aplicó riego. La PC en hoja fue mayor (P = 0.0007) a los 56 días con 11.45 % y de 8.30 % a los 98 días. La PC fue mayor (P = 0.0064) con riego 11.05 % y de 8.70 % sin riego. Se concluye que los incrementos en producción de MS total (tMSha-1) y la calidad de la biomasa indican la posibilidad de acortar los tiempos de reposo e incrementar la capacidad productiva de sistemas con bancos de biomasa de Cuba CT-115 cuando se aplica riego. Palabras clave Rendimiento, periodo seco, tallo, hoja

Correlaciones genéticas entre producción de leche y características de crecimiento en una población multirracial

In order to estimate the genetic parameters and correlations between total lactation milk yield and growth traits in a multiracial population of dual purpose cattle in tropical environments of Mexico, genetic variances and covariances were estimated between total milk yield during the first (PTL1L), second (PTL2L) and third lactations (PTL3L) and between PTL1L with birth weight (PN) and with weights adjusted to 205 (P205) and 365 (P365) days of age. To carry out this study, 1,349 records of lactations of females of cebuine breed crosses (CE) with Holstein (HS) [558], with Brown Swiss (SP) [444] and with Simmental (SM) [357] were used. Estimated heritabilties in both analyzes are presented. Genetic correlations found in the first analysis were 0.77 (± 0.16) between PTL1L and PTL2L, 0.47 (± 0.25) between PTL1L and PTL3L, and 0.73 (± 0.21) between PTL2L and PTL3L. Genetic correlations found in the second analysis were 0.10 (± 0.35) between PTL1L and PN, 0.20 (± 0.25) between PTL1L and P205 and 0.21 (± 0.32) between PTL1L and P365. It is concluded that the genetic correlations are positive between the first three lactations and a positive correlation is suggested between first lactation milk yield and growth traits, which makes feasible the genetic improvement programs that take into account both characteristics simultaneously.Con el objetivo de estimar las varianzas y covarianzas genéticas entre producción total de leche por lactación y crecimiento corporal en una población multirracial de bovinos de doble propósito en el trópico de México, se estimaron las varianzas y covarianzas genéticas entre la producción total de leche durante la primera (PTL1L), la segunda (PTL2L) y la tercera lactaciones (PTL3L), y las varianzas y covarianzas genéticas entre PTL1L con peso al nacimiento (PN) y los pesos ajustados a los 205 (P205) y 365 (P365) días de edad. Se utilizaron 1,349 registros de lactaciones de hembras de cruzas de razas cebuinas (CE) con Holstein (HS) [558], con Suizo Pardo (SP) [444] y con Simmental (SM) [357]. Se presentan las heredabilidades estimadas en ambos análisis. Las correlaciones genéticas encontradas en el primer análisis fueron 0.77 (± 0.16) entre PTL1L y PTL2L, 0.47 (± 0.25) entre PTL1L y PTL3L, y 0.73 (± 0.21) entre PTL2L y PTL3L. Las correlaciones genéticas encontradas en el segundo análisis fueron 0.10 (± 0.35) entre PTL1L y PN, 0.20 (± 0.25) entre PTL1L y P205 y 0.21 (± 0.32) entre PTL1L y P365. Se concluye que las correlaciones genéticas son positivas entre las tres primeras lactaciones y se sugiere una correlación positiva entre la primera lactación y características de crecimiento corporal, lo cual hace factible el planteamiento de programas de mejoramiento genético que tomen en cuenta ambas características de manera simultánea