ABSTRACT The aims of this study were to evaluate the effect of genetic and non-genetic factors on the growth of Socorro Island Merino lambs and to model their growth curve using nonlinear mathematical models. The weight of 41 Socorro Island Merino lambs was recorded at birth and at 45, 90, 135, 180, 225, 270, 315 and 365 days of life from May 2019 to September 2021. The effects on growth of sex, genotype, year of birth, and parity of the dam were analyzed. Four non-linear models (Brody, Logistic, Gompertz and von Bertalanffy) were fitted for determining the best model to describe growth curve. Birth weight and pre-weaning growth rate were not affected (P > 0.05) by any of the factors studied, while weaning weight was only significantly affected (P < 0.05) by sex. Year of birth significantly affected (P < 0.05) post-weaning growth rate and weight of the lamb from 270 days, while sex significantly affected (P < 0.05) weight at 315 days. The Gompertz and Brody models were the best fitted to describe growth curves of lambs. Purebred males showed a larger response to increasing levels of energy-protein supplementation, while they had greater mature weight and lower maturation rate compared to females and crossbred males. In conclusion, knowledge of growth and factors influencing growth pattern can help implement appropriate management strategies and make decisions aimed at the conservation of Socorro Island Merino lambs.

RESUMEN La revisión fue elaborada para conocer el efecto que tiene la fibra usada como prebiótico en pollo de engorda y gallinas de postura. Se realizó una revisión sobre las generalidades de la fibra y los beneficios que aporta sobre la inmunidad, desarrollo digestivo, digestibilidad de los nutrientes y rendimiento productivo. Se encontró que la fibra como aditivo se puede incluir a niveles menores del 3% para mejorar la respuesta inmune de las aves, aumenta el desarrollo de vellosidades intestinales y la cantidad de citoquinas reguladoras de la quimiotaxis limitando la permeabilidad de sustancias tóxicas al torrente sanguíneo, además, regula la respuesta inflamatoria del intestino. La fibra estimula el microbiota intestinal evitando la adherencia y desarrollo de bacterias patógenas, así como la producción de péptidos antimicrobianos. Además, la fibra puede regular la motilidad intestinal, la microbiota general, la acumulación de lípidos en hígado, disminuir el colesterol, contribuir al funcionamiento hepático, disminuir emisiones contaminantes al ambiente y mejorar la absorción de los nutrientes. Por lo tanto, la fibra puede mejorar la ganancia de peso, la conversión del alimento y el desarrollo muscular de la molleja. Se concluye que la fibra como prebiótico puede ser incluida en la dieta de las aves para sustituir a los aditivos sintéticos para incrementar el rendimiento productivo de las aves.

ABSTRACT The review was elaborated to know the effect of fiber used as a prebiotic in broilers and laying hens. A review was made on generalities of fiber and its benefits on immunity, digestive development, nutrient digestibility and productive performance. It was found that fiber as an additive can be included at levels lower than 3% to improve the immune response of birds, increase the development of intestinal villi and the amount of cytokines that regulate chemotaxis, limiting the permeability of toxic substances to the bloodstream, and regulate the inflammatory response of the intestine. Fiber stimulates the intestinal microbiota by preventing the adherence and development of pathogenic bacteria, as well as the production of antimicrobial peptides. In addition, fiber can regulate intestinal motility, general microbiota, lipid accumulation in the liver, lower cholesterol, contribute to liver function, reduce pollutant emissions to the environment and improve nutrient absorption. Therefore, fiber can improve weight gain, feed conversion and gizzard muscle development. It is concluded that fiber, as a prebiotic can be included in the poultry diet to replace synthetic additives to increase the productive performance of poultry.

Resumen El objetivo fue analizar la relación entre el perfil de resistencia a antibióticos y la formación de biofilm de aislados de S. aureus provenientes de mastitis bovina. Se analizaron 30 aislados de S. aureus procedentes de casos de mastitis subclínica en granjas lecheras en sistemas de producción semi-intensivo y de traspatio ubicadas en los estados de Guanajuato y Michoacán, México. Se realizó un antibiograma por el método de difusión en disco Kirbi Bauer. La formación de biofilm se determinó por el método de tinción con cristal violeta. Para la evaluación de genes de resistencia a antibióticos y de formación de biofilm se obtuvo ADN genómico de una colonia para la identificación de los genes: blaZ, mecA, tetK, tetM, gyrA y gyrB, y icaA e icaD. Los resultados mostraron que el 100 % de los aislados fueron resistentes a penicilina y dicloxacilina, seguidos por cefotaxima (86.6 %), ampicilina y cefalotina (83.3 %) y ceftazidima (80.0 %), mientras que se observó un 36.6 % de resistencia a oxacilina. Se identificó que todos los aislados de S. aureus presentaron la capacidad de formar biofilm con un rango del 20 a 98 %. Se observó además que los aislados con una multirresistencia elevada presentaron una mayor formación de biofilm; estableciéndose una correlación positiva significativa. En conclusión, los aislados de S. aureus provenientes de mastitis bovina presentaron elevados niveles de resistencia a antibióticos; así como una importante capacidad formadora de biofilm, demostrando la existencia de una correlación positiva entre estos dos factores.

Abstract The objective was to analyze the relationship between the antibiotic-resistance profile and the biofilm formation of S. aureus isolates from bovine mastitis. Thirty (30) isolates of S. aureus from cases of subclinical mastitis in dairy farms in semi-intensive production and backyard production systems, located in the states of Guanajuato and Michoacán, Mexico, were analyzed. An antibiogram was performed by the Kirbi-Bauer disc-diffusion method. Biofilm formation was determined by the violet crystal staining method. For the evaluation of antibiotic resistance genes and biofilm formation, genomic DNA was obtained from a colony for the identification of the genes: blaZ, mecA, tetK, tetM, gyrA and gyrB, and icaA and icaD. The results showed that 100 % of the isolates were resistant to penicillin and dicloxacillin, followed by cefotaxime (86.6 %), ampicillin and cephalotin (83.3 %) and ceftazidime (80.0 %), while a 36.6 % resistance to oxacillin was observed. It was identified that all isolates of S. aureus had the ability to form biofilm with a range between 20 to 98 %. It was also observed that isolates with a high multi-resistance presented a greater formation of biofilm, establishing a significant positive correlation. In conclusion, S. aureus isolates from bovine mastitis presented high levels of antibiotic resistance; as well as an important biofilm-forming capacity, demonstrating the existence of a positive correlation between these two factors.

Resumen: El objetivo de la investigación fue conocer el comportamiento y la habilidad materna del Cerdo Pelón Mexicano (CPM) mediante el análisis de parámetros reproductivos y productivos desde el parto al destete. Se evaluaron dos ecotipos de CPM provenientes de Huehuetla, Hidalgo (CPH) y de Atlequizayán, Puebla (CPP). Las variables por lechón fueron peso al nacimiento (PN) y peso al destete (PD). En los partos no se registraron distocias, ni muertes y presentaron anidación; el ecotipo CPP presentó el mayor número en los parámetros reproductivo que CPH. Las medias de los PN y PD fueron superiores para los lechones CPH que CPP. El comportamiento materno fue favorable, ya que no se presentaron muertes al nacimiento ni en la lactancia. En los parámetros productivos las hembras del CPP tuvieron camadas ligeramente de mayor tamaño en comparación con las CPH, mientras que los lechones de CPH presentaron un mayor peso.

Abstract: The objective of the research was to know the behavior and maternal ability of the Cerdp Pelon Mexicano (CPM) through the analysis of reproductive and productive parameters from birth to weaning. Two ecotypes of CPM from Huehuetla, Hidalgo (CPH) and from Atlequizayán, Puebla (CPP) were evaluated. The variables per piglet were birth weight (PN) and weaning weight (PD). No dystocia, no deaths were recorded in the deliveries and they presented nesting; the CPP ecotype presented the highest number in reproductive parameters than CPH. The means of the PN and PD were higher for the CPH than CPP piglets. Maternal behavior was favorable, since there were no deaths at birth or in lactation. Regarding the productive parameters, the CPP females had slightly larger litters compared to the CPH, however, the CPH piglets presented a higher weight.

ABSTRACT The study evaluated the causes and risk factors associated with pre-weaning mortality in extensive and semi-extensive lamb production systems in a municipality in the coastal region of the state of Colima, Mexico. Mortality was assessed by necropsy and information on the number of births and the body condition of the ewe before lambing, litter size, sex, breed and weight of the lamb was recorded at the time of lambing. Statistical analysis was done using the Chi-square test of independence and by means of stepwise Logistic Regression. The overall pre-weaning mortality rate was 27.9%. The number of lambs born and dead was 875 and 244, respectively, where 88.1% of the mortality occurred during the first 48 hours of birth due to starvation-exposure syndrome. Pre-weaning mortality was significantly associated (p<0.05) with the flock, body condition of the ewe at parturition and with the lamb´s weight at birth and breed. Lambs that weighed less than 2 kg at birth were eight times more likely to die than heavier lambs (OR= 8.30) and lambs born to ewes with a body condition of less than two at lambing were more likely to die than those born of a sheep with higher body condition (OR = 3.02).

RESUMEN El estudio tuvo como objetivo de estudiar las causas y factores de riesgo asociados a la mortalidad predestete en sistemas de producción de corderos bajo sistemas extensivos y semi-extensivos en un municipio de la región costera del estado de Colima, México. La mortalidad se evaluó mediante necropsia y la información sobre el número de parto y la condición corporal de la oveja antes del parto, el tamaño de la camada, el sexo, la raza y el peso del cordero se registró en el momento del parto. El análisis estadístico se hizo mediante la prueba de independencia de Chi-cuadrado y por medio de la Regresión Logística por pasos. La tasa global de mortalidad predestete fue de 27.9%. El número de corderos nacidos y muertos fue de 875 y 244, respectivamente, donde 88.1% de la mortalidad ocurrió durante las primeras 48 horas del nacimiento por el síndrome de inanición-exposición. La mortalidad predestete se asoció significativamente (p<0.05) con el hato, la condición corporal de la oveja al parto y con el peso al nacimiento y la raza del cordero. Los corderos que pesaron menos de 2 kg al nacer (OR = 8.30) tuvieron ocho veces más probabilidades de morir que los corderos más pesados y los corderos nacidos de ovejas con una condición corporal menor a dos al parir tuvieron más probabilidades de morir que aquellos nacidos de una oveja con mayor condición corporal (OR = 3.02).

ABSTRACT Records of 3716 Nubian goats from the United States (US) were analyzed to estimate relationships between fourteen conformation traits (CT) with lactation average somatic cell score (ASCS). To analyze ASCS, a mixed model was implemented. Linear and quadratic effects of CT traits, days in milk (DIM), and kidding age in months (KA) were considered as fixed covariates, and herd-year (HY) of kidding as a random effect. Correlation coefficients between CT traits and ASCS adjusted for HY and linear and quadratic KA effects were also obtained. The average ± standard deviations for ASCS, DIM, and milk yield were 5.17±0.54 Log2, equivalent to 451.3 cells × 103/mL, 266.3±52.1 days, and 776.3±280.4 kg per lactation, respectively. Significant non-linear relationships with an intermediate maximum were found between ASCS with teat diameter and medial suspensory ligament, while linear relationships were observed with stature, strength, rump width, fore udder attachment, udder depth, teat diameter, teat placement, and medial suspensory ligament. The model explained 53.7% of the ASCS variability, but the contribution of each type variable to increase the coefficient of determination was low (<0.52%). Herd-year explained a large proportion of the variation of ASCS (38.4%). All estimated correlations between CT and ASCS had low values, from −0.04 to 0.11, but most were significant. The results of this study show that conformation traits have few opportunities to contribute phenotypically to assess somatic cell score in Nubian goats.

ABSTRACT: The objective of the present study was to describe macroscopic and microscopic lesion in the rumen of bovine slaughtered in the Municipal Meat Processor of Colima, Mexico. The lesions found during the slaughter were macroscopically and subsequently fixed in 10% buffered formalin with pH 7.2 described. It was with the routine histological technique, and stained with hematoxylin-eosin (H-E) processed. 100 rumen were collected, as well as data on the origin, age, sex, and species of the animals. Data were, with the Chi- square independence test and logistic regression analysis analyzed. The 98% of the bovines presented at least one of the following lesions: hemorrhages, erosions, ulcers, scars, hyperkeratosis, hydropic degeneration, rumenitis, lymphangiectasia, a sample had a papilloma and the presence of the protozoan Balantidium coli was in 30% of the samples found. Dependence was found between B. coli to the origin (P= 0.046) and the sex (P= 0.041) of the animals. The variables that were significant (P= <0.05) in the logistic regression analysis were scars, rumenitis, lymphangiectasia, and B. coli. The injuries found to interfere with the absorption of nutrients, loss of production, and productivity, as well as the presence of opportunistic pathogens that can represent a health risk for animals and humans.

RESUMEN: El objetivo del presente estudio fue describir los hallazgos macroscópicos y microscópicos encontrados en el rumen de bovinos sacrificados en la Procesadora Municipal de Carne de Colima, Colima, México. Las lesiones encontradas durante la faena se describieron macroscópicamente, posteriormente se fijaron en formalina amortiguada al 10% con pH 7.2, se procesaron con la técnica histológica de rutina y se tiñeron con hematoxilina-eosina (H-E). Se colectaron 100 rúmenes, así como datos de la procedencia, edad, sexo y especie de los animales. La información fue analizada con la prueba de independencia de Chi cuadrada y un análisis de regresión logística. El 98% de los bovinos presentaron al menos una de las siguientes lesiones: hemorragias, erosiones, úlceras, cicatrices, hiperqueratosis, degeneración hidrópica, rumenitis, linfangiectasia, una muestra presentó un papiloma y se encontró la presencia del protozoario Balantidium coli en el 30% de las muestras. Se encontró dependencia entre B. coli con la procedencia (P=0.046) y el sexo (P=0.041) de los animales. Las variables que fueron significativas (P=<0.05) en el análisis de regresión logística fueron las cicatrices, rumenitis, linfangiectasia y B. coli. Las lesiones encontradas interfieren con la absorción de nutrientes, pérdida de producción y productividad, así como la presencia de patógenos oportunistas que pueden representar un riesgo sanitario para animales y humanos.

ABSTRACT: This research aimed to evaluate the substitution of alfalfa hay to garlic leaves during the in vitro gas and methane production, as well as in ruminal fermentation patterns. There were four treatments: (T1) alfalfa hay (50%); (T2) alfalfa hay (33%) + raw garlic leaves (17%); (T3) alfalfa hay (17%) + raw garlic leaves (33%) and (T4) raw garlic leaves (50%). The highest values of "a" (gas production from the soluble fraction); "b" (gas production from the insoluble fraction) and "c" (gas production rate) were found in T4 (mL). While lower in T1 (P<0.05); but no differences were observed between T2 and T3 (P>0.05).The highest ammonia-nitrogen (NH3-N) concentration was recorded in T4 and the lowest in T1 (P<0.05). The propionate concentrations increased with T4 and decreased with T1, whereas the acetate decreased with T4 and increased with T1 (P<0.05). The highest methane production was recorded in T1 and the lowest in T4 (P<0.05). It is concluded that substitution of alfalfa hay to garlic leaves in beef cattle diets, improved the ruminal fermentation and decreased methane production under in vitro conditions.

RESUMEN: Esta investigación tuvo como objetivo evaluar la sustitución de heno de alfalfa por hojas de ajo en la producción de gas in vitro y metano, así como en los patrones de fermentación ruminal. Se evaluaron cuatro tratamientos: (T1) heno de alfalfa (50%); (T2) heno de alfalfa (33%) + hojas de ajo crudo (17%); (T3) heno de alfalfa (17%) + hojas de ajo crudo (33%) y (T4) hojas de ajo crudo (50%). Los valores más altos de "a" (producción de gas a partir de la fracción soluble); "b" (producción de gas a partir de la fracción insoluble) y "c" (tasa de producción de gas) se encontraron en T4 (mL); mientras que fueron menores en T1 (P <0.05); pero no se observaron diferencias entre T2 y T3 (P> 0.05). La concentración más alta de nitrógeno amoniacal (N-NH3) se registró en T4 y la más baja en T1 (P <0.05). Las concentraciones de propionato aumentaron con T4 y disminuyeron con T1, mientras que las de acetato disminuyeron con T4 y aumentaron con T1 (P <0.05). La producción de metano más alta se registró en T1 y la más baja en T4 (P <0.05). Se concluye, que la sustitución de heno de alfalfa por hojas de ajo en dietas de bovinos carne, mejoró la fermentación ruminal y disminuyó la producción de metano en condiciones in vitro.

ABSTRACT The aim of this study was to characterize the morphology of the creole goat of the Volcanes de Colima physiographic sub-province, Mexico. Seventeen body measurements were taken from 371 goats older than two years and four racial indices and seven functional indices were calculated. Data were analysed using Pearson correlation, principal component, and hierarchical cluster analysis. The rump angle, chest width and all measurements of the ears and udder showed the greatest variability. Also, the goats showed great morpho-structural harmony. Racial indices showed that goats are dolichocephalic, ellipometric, and have a convex rump, while functional indices indicated dual-purpose zootechnical aptitude. Four principal components explained 84.5% of the variation of body measurements. Rump angle, hearth girth, body length and ear length presented the highest weighting coefficients in PC1, PC2, PC3 and PC4, respectively. The hierarchical cluster analysis classified the goats into four groups: group 1 has the lower rump angle, suitable for milk production; groups 2 and 3 with a phenotype tending to dual purpose, being able to focus on the production of meat or milk; and group 4 with a phenotype predisposed to meat production.

RESUMEN El objetivo del presente estudio fue caracterizar la morfología de la cabra mestiza de la subprovincia fisiográfica Volcanes de Colima, México. Se tomaron 17 medidas corporales a 371 cabras mayores de dos años y se calcularon cuatro índices raciales y siete índices funcionales. Los datos fueron analizados usando análisis de correlación de Pearson, de componentes principales y de conglomerados jerárquicos. El ángulo de caída de grupa, la anchura de pecho y todas las medidas de las orejas y la ubre fueron las que mostraron la mayor variabilidad. Asimismo, las cabras mostraron una gran armonía morfoestructural. Los índices raciales mostraron que las cabras son dolicocéfalas, elipométricas y tienen una grupa convexa, mientras que los índices funcionales indicaron una aptitud zootécnica de doble propósito. Cuatro componentes principales explicaron el 84.5% de la variación entre las medidas corporales de las cabras. El ángulo de caída de la grupa, el perímetro torácico, la longitud corporal y la longitud de oreja presentaron los mayores coeficientes para los componentes CP1, CP2, CP3 y CP4 respectivamente. El análisis de conglomerados jerárquicos clasificó a los animales en cuatro grupos: grupo 1 conformado por cabras con un menor ángulo de caída de grupa, apropiado para la producción de leche; grupos 2 y 3 con fenotipo tendiente al doble propósito, pudiendo orientarse a la producción de carne o leche; y grupo 4 con fenotipo con predisposición a la producción de carne.

Abstract Coenzyme Q9 (COQ9), a coenzyme Q (CoQ) precursor, is an essential component of the mitochondrial electron transport chain that drives adenosine triphosphate production. COQ9 polymorphism 18:25527339 is characterized by substitution of guanine (allele G) for adenine (allele A), which modifies the function of the protein encoded by the gene. In Holsteins, allele A has been associated with better reproductive performance in terms of the conception rate, number of services per conception (SPC) and days open (DO). The signal transducer and activator of transcription (STAT) protein is a transcription factor activated in the presence of cytokines and growth factors. STAT5A polymorphism 19:42407732 in exon 8 has been associated with higher fertility and embryonic survival rates. The objective of this study was to determine the relationship of COQ9 and STAT5A polymorphisms with reproductive parameters [calving to first heat interval (CFHI), DO and SPC]. Blood samples were taken from 112 lactating Holstein from a herd in México for allele genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). To estimate the association between reproductive parameters and genotypes, a linear mixed-effect model was performed. The COQ9 AG genotype was associated significantly with lower SPC (P<0.05) but not with DO or CFHI. No significant association with any reproductive parameter was found for STAT5A. Our findings suggest that the COQ9 18:25527339 polymorphism is a useful molecular marker for improvement of reproductive performance in dairy herds.

Abstract: The aspiration of oocytes by laparoscopy for the transfer of embryos is a technique used in the extraction of oocytes from a genetically superior animal, with the purpose of producing in vitro embryos to implant them in a female, which allows to increase the response to selection in a program of genetic improvement, by obtaining animals above the population average and because the generation interval can be reduced. Prior to the aspiration of the oocytes, it is necessary to prepare the donor and recipient females based on exogenous hormones, to achieve maximum production and extraction of oocytes in the same donor female and, consequently, a greater probable number of embryos produced and transferred. With the aim of describing the different protocols used in the aspiration of oocytes by the laparoscopic technique for the transfer of embryos in goats, the present literature review was carried out through scientific publications.

Resumen: La aspiración de ovocitos por laparoscopía para la transferencia de embriones es una técnica utilizada en la extracción de ovocitos de un animal genéticamente superior, con la finalidad de producir embriones in vitro para implantarlos en una hembra, lo cual permite incrementar la respuesta a la selección en un programa de mejoramiento genético, al obtener animales superiores al promedio de la población y porque se puede reducir el intervalo de generación. Previo a la aspiración de los ovocitos, es necesario preparar a las hembras donantes y receptoras a base de hormonas exógenas, para lograr la producción y extracción máxima de ovocitos en una misma hembra donante y, por consecuencia, un mayor número probable de embriones producidos y transferidos. Con el objetivo de describir los diferentes protocolos utilizados en la aspiración de ovocitos por la técnica de laparoscopía para la trasferencia de embriones en cabras, se realizó la presente revisión de literatura mediante publicaciones científicas.

Abstract In this work, we use the records from 643 goats in order to evaluate the phenotypic relationships between conformation traits and milk production in goats. Correlations were estimated using data on goats which included fifteen conformation traits and first lactation milk yield adjusted for age, calving month and 305 milking days (MY1). We also compared the average scores for type traits on the goats under study with those on a sample of goats from the United States of America (USA). Correlations between conformation traits and MY1 were estimated and an analysis was performed to evaluate the nonlinear relationships between them. The highest correlations were found between milk production and udder depth (-0.22), stature (0.18) and rear udder side view (0.12) (p < 0.05), non-linear (cubic) effects for stature and strength being significant (p < 0.05). American goats had a better overall conformation than the Mexican ones but results indicated that goats with better body conformation were not the best for milk production.

Resumen Con el objeto de evaluar las relaciones fenotípicas entre características de conformación y la producción de leche en cabras, se utilizó la información de 643 animales. Los datos de las cabras incluyeron quince rasgos de conformación y la producción de leche de la primera lactancia ajustada a edad, mes de parto y 305 días de ordeño (MY1, por sus siglas en inglés). Se compararon también los promedios de las calificaciones de tipo de las cabras de este estudio y de una muestra de cabras de los Estados Unidos de América (USA, por sus siglas en inglés). Se estimaron correlaciones entre las características de conformación con MY1 y se efectuó un análisis para evaluar las relaciones no lineales entre ellas. Las correlaciones más altas fueron entre MY1 y la profundidad de ubre (-0.22), estatura (0.18) y ubre trasera vista de lado (0.12) (p < 0.05) y los efectos no lineales (cúbicos) para estatura y fortaleza resultaron significativos (p < 0.05). Las cabras de USA tuvieron una mejor conformación general que las cabras de México; sin embargo, los resultados indican que las cabras con mejor conformación corporal no fueron las mejores para producir leche.

The objective of the study was to estimate the genetic and phenotypic trends for milk yield (MILK, n = 1041), fat yield (FAT, n = 487), protein yield (PROT, n = 477), lactose yield (LACT, n = 401), fat content (%FAT, n = 487), protein content (%PROT, n = 477) and lactose content (%LACT, n = 401), analyzing first lactation records adjusted to 305-d, obtained between 2000 and 2006 from 10 Saanen goats flocks from Guanajuato, Mexico. Predicted breeding values (PBV) were obtained with single-trait animal models that included phantom parent groups. Genetic trends were estimated as the regression of the PBV on year of birth. Phenotypic trends were estimated as the linear regression coefficients of production records on the year of birth. The annual genetic trends for MILK, FAT, PROT and LACT were 2.99 ± 1.06 kg, -0.21± 0.09 kg, -0.10 ± 0.04 kg and -0.19 ± 0.09 kg, respectively (P<0.05). Annual genetic trends for %FAT, %PROT and %LACT were close to zero (P>0.05). The mean annual genetic trend for MILK was 0.32 % of the phenotypic mean. These results indicate that it is necessary to use more appropriate selection criteria, increasing the emphasis on all the production traits, including fat and protein contents in order to maximize the economic progress in this population, whose main objective is milk production for cheese yield manufacture.

Con el objetivo de estimar las tendencias genéticas y fenotípicas, se analizaron registros de primera lactancia estandarizados a 305 días para producción de leche (MILK, n = 1041), producción de grasa (FAT, n = 487), producción de proteína (PROT, n = 477), producción de lactosa (LACT, n = 401), contenido de grasa (%FAT, n = 487), contenido de proteína (%PROT, n = 477) y contenido de lactosa (%LACT, n = 401), obtenidos entre 2000 y 2006 en 10 rebaños de cabras Saanen de Guanajuato, México. Los valores genéticos aditivos predichos (VGP) se obtuvieron mediante modelos animales univariados que incluyeron grupos genéticos de progenitores fantasmas. Las tendencias genéticas se estimaron a partir de la regresión de los VGP en el año de nacimiento. Las tendencias fenotípicas se estimaron a partir de la regresión de los registros en el año de nacimiento. Las tendencias genéticas anuales para MILK, FAT, PROT y LACT fueron de 2.99 ± 1.06 kg, -0.21 ± 0.09 kg, -0.10 ± 0.04 kg y -0.19 ± 0.09 kg, respectivamente (P<0.05). Las tendencias genéticas anuales para %FAT, %PROT y %LACT fueron cercanas a cero (P>0.05). La tendencia genética anual para MILK fue de 0.32 % de la media fenotípica. Estos resultados indican que es preciso usar criterios más adecuados de selección, incrementando el énfasis en todas las características productivas, incluyendo los contenidos de grasa y proteína, para maximizar el progreso económico en esta población, cuya principal finalidad es la producción de leche para la fabricación de queso.

With the objective of estimating allele frequencies, and testing for population divergence for the CSN1S1 locus, genotypes of animals from five goat populations; Saanen (n = 97), Alpine (n = 81) Toggenburg (n = 92), local goats with external appearance similar to the Murciana-Granadina breed from Central Mexico (n = 26) and heterogeneous local animals denominated Mosaico Lagunero (n = 30), from Northern Mexico, were identified using PCR and Xmn1 PCR-RFLP methodology. For Saanen, Alpine and Toggenburg, the sum of E and F alleles had the largest frequencies (from 0.468 to 0.789), while for the groups local Murciana-Granadina and Mosaico Lagunero the sum of the most frequent allelic groups (A* and B*), were 0.385 and 0.533 respectively. Both local Murciana-Granadina and Mosaico Lagunero populations showed heterozygote excess (P < 0.08). The percentage of the total genetic variation (F ST) explained by population differences was 5.16. There was genetic differentiation for most pair comparisons between populations (P < 0.05), excepting for Alpine versus Toggenburg, and Toggenburg versus Mosaico Lagunero (P > 0.05). For Saanen and Alpine the frequencies of alleles E and F were similar to the same breeds previously analyzed in Europe. Therefore there are opportunities of increasing the frequency of the strong alleles for protein content Gene Assisted Selection (GAS) in these two breeds. For Toggenburg the most frequent allelic groups were F (0.32) and B* (0.21). Results indicate differentiation between most populations for this locus. Moreover, heterozygote excess in local populations indicated breed admixture.

Se utilizaron datos de 47609 vacas e información de pedigrí de 57787 animales Holstein, obtenidos entre 1970 y 1997, para estimar las heredabilidades (h²) así como correlaciones genéticas y fenotípicas para la duración de la vida productiva a la tercera lactancia (DVP), producción total de leche acumulada a la tercera lactancia (PTA), habilidad de permanencia a los 48 meses de edad (HP48) y producción de leche de la primera lactancia (PL1). Para estimar los componentes de covarianza se utilizó el procedimiento de máxima verosimilitud restringida con modelos animales uni y bivariados. Para DVP, PTA y HP48, el modelo incluyó el efecto de hato-año-estación de parto, considerado fijo, la producción de leche real a 305 días como covariable y los efectos aleatorios del animal y error. Para PL1 el modelo incluyó el hato-año-estación de parto como efecto fijo, y los efectos aleatorios del animal y error. Los promedios para DVP, PTA HP48 y PL1 fueron 51,4 meses, 16469kg, 60% y 7673kg, respectivamente. Las heredabilidades para DVP, PTA, HP48 y PL1 fueron 0,04; 0,06; 0,03 y 0,25 respectivamente. Todas las correlaciones genéticas y fenotípicas entre las distintas variables estudiadas fueron positivas. Las correlaciones genéticas y fenotípicas de HP48 con DVP y PTA fueron entre 0,72 y 0,94. Los resultados sugieren que la HP48 puede utilizarse como indicador temprano de longevidad, que se debe continuar seleccionando sobre PL1 en función de su valor económico y que algunas de las características de longevidad estudiadas pueden incluirse como criterios u objetivos de selección en programas de mejoramiento para ganado Holstein en México.

Data from 47609 cows and pedigree information from 57787 Holstein animals, obtained from 1970 to 1997, were used to estimate heritabilities as well as genetic and phenotypic correlations for length of productive life until third lactation (DVP), total milk production until third lactation (PTA), stayability to 48 months of age (HP48) and first lactation milk yield (PL1). Restricted maximum likelihood procedure was used to estimate the covariance components with uni and bivariate animal models. For DVP, PTA and HP48, the model included the effect of herd-year-season of calving, considered fixed, actual 305-day milk production as covariate, and the random effects of animal and error. The model used for PL1 included herd-year-season as fixed effect, and animal and error as random effects. Averages for DVP, PTA, HP48 and PL1 were 51.4 months, 16469kg, 60% and 7673kg, respectively. Heritabilities for DVP, PTA, HP48 and PL1 were 0.04, 0.06, 0.03 and 0.25 respectively. All genetic and phenotypic correlations among the studied variables were positive. The genetic and phenotypic correlations obtained between HP48 with DVP and PTA were from 0.72 to 0.94. Results suggest that HP48 can be used as an early indicator of longevity, that selection on PL1 should be continued because of their economic value, and that some of the longevity traits studied may be included as selection criteria or selection objectives in the improvement programs for Holstein cattle in Mexico.

Se utilizaram dados de 47609 vacas e informação de pedigrí de 57787 animais Holstein, obtidos entre 1970 e 1997, para estimar as heredabilidades (h²) assim como correlações genéticas e fenotípicas para a duração da vida produtiva à terceira lactância (DVP), produção total de leite acumulada à terceira lactância (PTA), habilidade de permanência aos 48 meses de idade (HP48) e produção de leite da primeira lactância (PL1). Para estimar os componentes de covarianza utilizou-se o procedimento de máxima verosimilitude restringida com modelos animais uni e bi-variados. Para DVP, PTA e HP48, o modelo incluiu o efeito de rebanho-ano-estação de parto, considerado fixo, a produção de leite real a 305 dias como co-variável e os efeitos aleatórios do animal e erro. Para PL1 o modelo incluiu o rebanho-ano-estação de parto como efeito fixo, e os efeitos aleatórios do animal e erro. As médias para DVP, PTA HP48 e PL1 foram 51,4 meses, 16469 kg, 60% e 7673 kg, respectivamente. As heredabilidades para DVP, PTA, HP48 e PL1 foram 0,04; 0,06; 0,03 e 0,25 respectivamente. Todas as correlações genéticas e fenotípicas entre as distintas variáveis estudadas foram positivas. As correlações genéticas e fenotípicas de HP48 com DVP e PTA foram entre 0,72 e 0,94. Os resultados sugerem que a HP48 pode utilizar-se como indicador temprano de longevidade, que se deve continuar selecionando sobre PL1 em função de seu valor econômico e que algumas das características de longevidade estudadas podem incluir-se como critérios ou objetivos de seleção em programas de melhoramento para gado Holstein no México.