31 research outputs found
Efecto del transporte en los indicadores de bienestar en bovinos productores de carne; un análisis
Objective: Review different factors related to cattle transport associated with welfare indicators.
Approach: During transport, cattle is subject to stress triggers that include: i) increased handling, ii) mixing of animals from different sources and contact with strangers, iii) physical challenges such as ramps, slippery surfaces, load density, movement, noise and vibration of the vehicle; iv) contact with new and unfamiliar environments; v) food and water deprivation; vi) changes in the social structure, vii) changes in climatic conditions such as temperature, radiation and humidity, viii) inability to rest, among other aspects. This document reviews the effects of transport on the welfare indicators of cattle and the effects of temperature, load density, duration of travel, rest, water and food provision among others.Objetivo: Revisar distintos factores relacionados con el transporte de ganado bovino asociados a los indicadores de bienestar.
Aproximación: Durante el transporte los bovinos son sometidos a factores desencadenantes de estrés que incluyen: i) incremento del manejo, ii) mezcla de animales de diferente procedencia y contacto con personal extraño, iii) desafíos físicos como rampas, superficies resbaladizas, densidad de carga, movimiento, ruido y vibración del vehículo; iv) contacto con ambientes nuevos y no familiares; v) privación de alimento y agua; vi) cambios en la estructura social, vii) cambios en las condiciones climáticas como temperatura, radiación y humedad, viii) imposibilidad de descanso, entre otros aspectos. En este documento se revisan los efectos del transporte en los indicadores de bienestar del ganado bovino y los efectos de la temperatura, la densidad de carga, duración del viaje, provisión de descanso, agua y alimento entre otros
Polymorphisms associated with the number of live-born piglets in sows infected with the PRRS virus in southern Sonora Mexico
The porcine reproductive and respiratory syndrome (PRRS) is a viral disease that decreases the reproductive performance in breeding sows and leads to economic losses to the swine industry. The objective of the present study was to identify single nucleotide polymorphisms (SNP) associated to the number of live-born piglets in the first (LBP1) and second birth (LBP2) in breeding sows exposed to PRRS virus. The study included 100 pregnant females of the Landrace(¾)/ Yorkshire(¼) line, 75 of which were infected with the PRRS virus and 25 were free of PRRS. Individual blood samples (6-8 drops) were obtained and spotted onto FTA cards and subsequently processed for DNA extraction, which was genotyped using a 10,000 SNP chip for genomic profile. Resulting genotypes were analyzed using a multi-locus mixed model that detected three SNP associated to LBP1 and five SNP associated to LBP2 (P<0.001). These eight SNP were validated using an associative mixed effects model which included the terms genotype and age of dam as fixed effects, and sire as random effect. Allele substitution effects were estimated using the same model including the term genotype as covariate. The SNP rs81276080, rs81334603 and rs80947173 were associated to LBP1 (P<0.001), whereas the SNP rs81364943, rs80859829, rs80895640, rs80893794 and rs81245908 were associated to LBP2 (P<0.001). Only two SNP were in functional chromosomal regions and the remainder SNP were within an intergenic position. In conclusion, these results suggest the existence of gene variants associated with the reproductive performance of sows infected with the PRRS virus.The porcine reproductive and respiratory syndrome (PRRS) is a viral disease that decreases the reproductive performance in breeding sows and leads to economic losses to the swine industry. The objective of the present study was to identify single nucleotide polymorphisms (SNP) associated to the number of live-born piglets in the first (LBP1) and second birth (LBP2) in breeding sows exposed to PRRS virus. The study included 100 pregnant females of the Landrace(¾)/ Yorkshire(¼) line, 75 of which were infected with the PRRS virus and 25 were free of PRRS. Individual blood samples (6-8 drops) were obtained and spotted onto FTA cards and subsequently processed for DNA extraction, which was genotyped using a 10,000 SNP chip for genomic profile. Resulting genotypes were analyzed using a multi-locus mixed model that detected three SNP associated to LBP1 and five SNP associated to LBP2 (P<0.001). These eight SNP were validated using an associative mixed effects model which included the terms genotype and age of dam as fixed effects, and sire as random effect. Allele substitution effects were estimated using the same model including the term genotype as covariate. The SNP rs81276080, rs81334603 and rs80947173 were associated to LBP1 (P<0.001), whereas the SNP rs81364943, rs80859829, rs80895640, rs80893794 and rs81245908 were associated to LBP2 (P<0.001). Only two SNP were in functional chromosomal regions and the remainder SNP were within an intergenic position. In conclusion, these results suggest the existence of gene variants associated with the reproductive performance of sows infected with the PRRS virus
Vitrification of White-tailed Deer (Odocoileus virginianus) oocytes with sucrose or trehalose for in vitro maturation and fertilization.
Objective: Evaluate the White-tailed Deer (WTD) in vitro embryo production (IVP) and oocytes vitrified with Trehalose (TH) or Sucrose (SC).
Design/methodology/approach: Total vitrified oocytes were placed into two different groups: TH (n=60) and SC (n=61). Samples were selected and analyzed for viability evaluation TH (n=5) and SC (n=5), nuclear status (NS) TH (n=4) and SC (n=5), Germinal Vesicle (GV), Metaphase I, or not evaluable (NE) after warming. In vitro maturation (IVM) was conducted for 36 h in supplemented TCM-199 medium. Immediately afterwards, oocyte NS was evaluated (n=88) [(GV, MI=immature), (MII=mature)]. In vitro fertilization (IVF) was performed in supplemented TALP medium for 24 h using frozen WTD semen (3x106 sperm/mL), NS was classified [Fertilized (F), Not fertilized (NF), or NE].
Results: After warming, viability for the TH group (n=5) was 60% versus 40% for SC group (n=5), however, oocytes in both groups were immature (GV and MI stage). For IVM, NS evaluations of the TH group (n=38) revealed no maturation versus 2% in the SC group (n=50) (MII stage=matured). IVF evaluations for the TH group (n=10) revealed no fertilization compared to 20% in the SC group (n=5). A statistical difference (p>0.05) was not found between the TH and SC groups.
Limitations on study/implications: White-tailed Deer in vitro embryo production is not well documented.
Findings/conclusions: Future research with a larger number of WTD oocytes is needed for further evaluation of oocyte vitrification IVP techniques as a model for endangered cervids
Innovaciones y mejoras en el proyecto tutoría entre compañeros. Curso 2015-2016
Memoria ID-0137. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2015-2016
Suplementación con zinc orgánico y rendimiento productivo de cerdos en ambiente caluroso
In order to evaluate the influence of organic zinc supplementation on the performance of developing pigs in a warm environment (t 30.4 °C, RH of 73% and THI 82), 96 pigs of 84 d of age were used (33.8 ± 0.96 kg of live weight) in a randomized complete block design. The treatments were: 1) Control (n = 24), corn/soybean-based developing pig diet; 2) Control plus 120 ppm Zn/kg of DM; 3) Control plus 240 ppm Zn/kg of DM, and 4) Control plus 360 ppm organic Zn/kg of DM. Zinc was provided as zinc methionine (ZnMet). The pigs in groups of eight (4 males and 4 females) were placed in 12 pens (3 per treatment). The pen was the experimental unit. The pigs were weighed on days 1 and 42; fed intake, air temperature, and RH were recorded daily. The results were analyzed by ANOVA (p <0.05) and the influence of the Zn level on the productive response was explored by orthogonal polynomials. Quadratic responses were observed at the Zn supplementation level in the final weight (P = 0.05), daily weight gain (P = 0.03) and daily feed intake (P = 0.05). The feed conversion tended (P = 0.08) to improve linearly as the Zn level increased, with mean values of 2.97, 2.83, 2.90 and 2.70 kg of feed/kg of gain, for Control, 120 ZnM, 240 ZnM, and 360 ZnM, respectively. The results indicate that the diets intake supplemented with Zn improves the feed
conversion of pigs during the development stage, under warm environment conditionCon el objetivo de evaluar la influencia de la suplementación con zinc orgánico en el rendimiento de los cerdos en desarrollo en ambiente caluroso (t 30.4°C; HR de 73% y THI 82), se usaron 96 cerdos de 84 d de edad (33.8 ± DE 0.96 kg de p.v.) en un diseño de bloques completos al azar. Los tratamientos fueron: 1) Testigo (n = 24), dieta de desarrollo basada en maíz/soya; 2) Testigo más 120 ppm de Zn/kg de MS; 3)
Testigo más 240 ppm de Zn/kg de MS, y 4) Testigo más 360 ppm de Zn orgánico/kg de MS. El zinc se proporcionó como metionina de zinc (ZnMet). Los cerdos, en grupos de ocho (4 machos y 4 hembras), fueron colocados en 12 corrales (3 por tratamiento). El corral fue la unidad experimental. Los cerdos se pesaron los días 1 y 42; el consumo de alimento, la temperatura del aire y la humedad relativa (HR) se registraron diariamente. Los resultados se analizaron mediante ANDEVA (p <0.05) y la influencia del nivel de Zn en la respuesta productiva se exploró mediante polinomios ortogonales. Se observaron respuestas cuadráticas al nivel de suplementación con Zn en el peso final (P = 0.05), ganancia diaria de peso (P =0.03) y consumo diario de alimento (P = 0.05). La conversión alimenticia tendió (P = 0.08) a mejorar linealmente a medida que se incrementó el nivel de Zn, con valores medios de 2.97, 2.83, 2.90 y 2.70 kg de alimento/kg de ganancia, para el testigo, 120 ZnM, 240 ZnM y 360 ZnM, respectivamente. Los resultados indican que el consumo de dietas suplementadas con Zn mejora la conversión alimenticia de los cerdos durante la etapa de desarrollo, bajo condiciones de ambiente cálid
Efecto del consumo de zinc orgánico en la respuesta productiva de la cerda y su camada
Abstract: To evaluate the productive response of sows and their litter to the supplementation with zinc in a tropical climate two experiments were realized. Exp. 1 (Fresh season). 46 Yorkshire x Landrace sows were used, assigned to one of two treatments (T) in a completely randomized design. T1 (SZn; n = 22); diet without addition of Zn from 35 days of gestation and during 21 d of lactation, and T2 (CZn; n = 24), T1 diet plus supplementation with 100 mg Zn/kg of feed. Exp. 2 (Warm season). Another 44 sows were assigned to one of two treatments similar to Exp. 1. T1 (SZn; n = 25) and T2 (CZn; n = 19). Results were analyzed by ANOVA (P ≤ 0.05). Results: Exp. 1. Feed consumption added with Zn increased (P < 0.05) IgG plasmatic concentration in weaned pigs. Exp. 2. Feed consumption added with Zn increased (P < 0.05) backfat thickness (BFT) of the sows during the gestation (16.6 vs. 14.8 mm) and decreased (P = 0.006) the mortality of nursing pigs during the lactation (11 vs. 26%). It concludes that additional consumption of zinc increase the BFT in gestating sows under environment heat stress and diminished the mortality of nursing pigs during lactation and intake of supplemented diet with zinc during fresh season increase IgG plasmatic concentration levels in weaned pigs.Resumen: Para evaluar la respuesta productiva de la cerda y su camada a la suplementación con zinc orgánico en clima tropical, se realizaron dos experimentos. Exp. 1 (Época fresca). Se utilizaron 46 cerdas Yorkshire x Landrace, asignadas a uno de dos tratamientos (T) en un diseño completamente al azar. T1 (SZn; n = 22); dieta sin adición de Zn a partir de los 35 días de gestación y durante 21 d de lactación; T2 (CZn; n = 24) T1 más la adición de 100 mg de Zn/kg de alimento. Exp. 2 (Época cálida). Se utilizaron 44 cerdas, asignadas al azar a uno de dos T similares al Exp.1: T1 (SZn; n = 25) y T2 (CZn; n = 19). Los resultados fueron analizados por ANDEVA (P ≤ 0.05). Resultados: Exp. 1. El consumo de alimento adicionado con Zn incrementó (P = 0.001) la concentración plasmática de IgG en los cerdos destetados. Exp. 2. El consumo de alimento adicionado con Zn, incrementó (P < 0.05) el espesor de grasa dorsal (EGD) de las cerdas durante la gestación (16.6 vs. 14.8 mm) y disminuyó (P = 0.006) la mortalidad durante la lactancia (11 vs. 26%). Se concluye que el consumo adicional de Zn incrementa el EGD en las cerdas gestantes bajo condiciones de estrés calórico y disminuye la mortalidad de lechones durante la lactancia, y el consumo adicional durante la época fresca incrementa los niveles plasmáticos de IgG en los LD
Respuesta productiva de corderos en engorda a la suplementación con extractos de taninos
Abstract: To determine the effect of supplementation tannin extract level (TE) on feedlot performance finishing hair lamb, was realized one experiment with a randomized complete block design, in that were used 48 hair lamb (3/4 Katahdin x 1/4 Pelibuey) with average 70 ± (standard deviation) 5 d old SD and an body weight of 21.3 ± 3.23 kg SD during a period of 70 day. The treatments were: 1) diet formulated with corn grain, soybean meal and corn straw, with nutritional support according physiology requirement, without addition of TE (Control; n = 12); 2) control diet plus supplementation with 0.15 % of TE (TE 15; n = 12); 3) control diet plus 0.3% of TE (TE 30; n = 12); and 4) control diet plus 0.45 % of TE (TE 45; n = 12). Results were analyzed by ANOVA (P ≤ 0.05), and the influence of TE level on productive response was explored using polynomial contrasts. Average daily gain (ADG) and feed conversion (feed/gain ratio) was improved (P ≤ 0.05) with the diet supplemented with 0.15 and 0.30% of TE, and body weight last was higher (P = 0.05) in the lamb feeding with supplemented diets 0.15% TE. Quadratic response was observed (P ≤ 0.05) to the TE supplementation level; the regression analyses suggest that better productive response may be found with TE 0.2% supplementation level (R2 = 0.75; P < 0.01). It is concluded, that intake of supplemented diets with TE improved ADG and feed conversion, and the better performance it is obtained with 0.2 % of TE in the diet.Resumen: Para determinar el efecto del nivel suplementario de extracto de taninos (ET) en la respuesta productiva de corderos en engorda, se realizó un experimento con un diseño de bloques completos al azar, en el que se usaron 48 corderos de pelo (3/4 Katahdin x 1/4 Pelibuey) con una edad promedio de 70 ± (desviación estándar) 5 d de edad DE y peso de 21.3 ± 3.23 kg DE durante un periodo de 70 días. Los tratamientos fueron: 1) Dieta formulada con grano de maíz, harina de soya y paja de maíz, con aporte nutrimental de acuerdo a la etapa fisiológica, sin adición de ET (testigo; n = 12); 2) dieta testigo más 0.15 % de ET (ET 15; n = 12); 3) dieta testigo más 0.30 % de ET (ET 30; n = 12) y 4) dieta testigo más 0.45 % de ET (ET 45; n = 12). Los resultados fueron analizados por ANDEVA (P ≤ 0.05), y la influencia del nivel de ET en la respuesta productiva se exploró mediante polinomios ortogonales. La ganancia diaria de peso (GDP) y la conversión alimenticia (CA) mejoraron (P ≤ 0.05) con la inclusión de 0.15 y 0.30 % de ET en la dieta, y el peso final fue mayor (P = 0.05) en los corderos que consumieron la dieta con 0.15 % de ET. Se observó una respuesta cuadrática (P ≤ 0.05) al nivel de adición de ET; el análisis de regresión sugiere que la mejor respuesta productiva puede obtenerse con niveles de 0.2 % de ET en la dieta (R2 = 0.75; P < 0.01). Se concluye, que el consumo de dietas suplementadas con ET mejora la GDP y la CA, y la mejor respuesta se obtiene con 0.2 % de ET en la dieta
Método de suplementación de zinc orgánico y respuesta productiva de cerdos en etapa de iniciación en clima cálido
Abstract: In order to evaluate the productive response of pigs in initiation under conditions of high environmental heat load to organic zinc additional supplementation, 816 piglets (21 days of age and 6.280 ± 0.817 kg of body weight) were used, born of mothers who were supplemented with 0 or 100 mg Zn / kg of diet during pregnancy and lactation, under a randomized complete block design with a 2 x 2 x 2 factorial arrangement. The experiment was carried out during two periods: 1) May-July and 2) September-November; each with duration of 49 days. In each period, 408 piglets were grouped by weight in 3 uniform groups, distributed in 12 pens (6 repetitions / treatment). The levels of additional supplementation tested were 0 and 100 mg Zn/kg of diet and the treatments were: 1) Mothers not supplemented-piglets not supplemented (Control); 2) Mothers not supplemented-supplemented piglets (ZnC); 3) Mothers supplemented-piglets not supplemented (ZnGL) and 4) Mothers supplemented-piglets supplemented (ZnGL + ZnC). The pigs were fed diets that met their nutritional requirements during the experiment. The average THI was 78.19 ± 2.9 during the test period. There was no interaction between treatments on the variables evaluated. Supplementing Zn during the gestation-lactation period tended (P = 0.06) to decrease mortality; however, continuing with additional supplementation during the initiation phase offered no advantage. There were no differences in the other variables evaluated in the supplemented group due to the supplementation method. It is concluded that additional supplementation with 100 mg of Zn from Zn during the gestation-lactation phase help to reduce the mortality in the initiation stage, in piglets bred in warm weather.Resumen: Con el objetivo de evaluar la respuesta productiva de cerdos en etapa de iniciación bajo condiciones de alta carga de calor ambiental a la suplementación adicional con zinc orgánico, se usaron 816 lechones (21 días de edad y 6.280 ±0.817 kg de peso corporal), nacidos de madres que fueron suplementadas con 0 ó 100 mg Zn/kg de dieta durante la gestación y lactación, bajo un diseño de bloques completos al azar con arreglo factorial 2 x 2 x 2. El experimento se realizó en dos periodos: 1) Mayo-julio y 2) Septiembre-noviembre; cada uno con una duración de 49 días. En cada periodo, 408 lechones fueron agruparon por peso en 3 grupos uniformes, distribuidos en 12 corraletas (6 repeticiones/tratamiento). Los niveles de suplementación adicional probados fueron de 0 y 100 mg Zn/kg de dieta y los tratamientos consistieron en: 1) Madres no suplementadas-lechones no suplementados (Testigo); 2) Madres no suplementadas-lechones suplementados (ZnC); 3) Madres suplementadas-lechones no suplementados (ZnGL) y 4) Madres suplementadas-lechones suplementados (ZnGL + ZnC). Los cerdos se alimentaron con dietas que cubrieron sus requerimientos nutrimentales durante el experimento. El THI promedio fue de 78.19±2.9 durante el periodo de prueba. No existió interacción entre tratamientos sobre las variables evaluadas. El suplementar Zn orgánico durante el periodo de gestación-lactación tendió (P=0.06) a disminuir la mortalidad; sin embargo, el continuar con la suplementación adicional durante la fase de iniciación no ofreció ventaja. No existieron diferencias en las otras variables evaluadas en el grupo suplementado debido al método de suplementación. Se concluye que la suplementación adicional con 100 mg de Zn a partir de Metionina de Zinc durante la fase de gestación-lactación ayuda a disminuir la mortalidad en la etapa de iniciación, en lechones criados en clima cálido
Respuesta productiva de cerdos en crecimiento-finalización a la suplementación con extracto de taninos
With the objective of evaluate the productive performance of fattening pigs under heat stress conditions to the consumption of food supplemented with hydrolysable tannins extract (HT), 72 pigs of 70 days old and 26.98 ±SD 4.36 kg BW were used, in a complete randomized block experimental design. The treatments were: 1) Diets based on corn and soybean meal, with nutrient intake according to their productive stage (Control; n = 36), and 2) Control plus 0.2 % extract of HT (n = 36). Pigs were housed in groups of 3 females and 3 males in 12 pens. To the data applied ANOVA (P 0.05) by treatment. When taking together both periods (growth and finalization phase, day 1 - 90), the additional consumption of HT tended to increased (P = 0.06) the ADG in 12.91 % (0.782 vs. 0.681 kg), and the final body weight in 9.26 % (97.17 vs. 88.17 kg; P = 0.06). It is conclude that the consumption of diets with 0.2 % HT enhanced weight gain in the growing-finishing phases of pig fattening under heat stress conditions.Con el objetivo de evaluar la respuesta productiva de cerdos en crecimiento-finalización bajo condiciones de estrés calórico al consumo de alimento adicionado con extracto de taninos hidrolizables (TH), se usaron 72 cerdos de 70 días de edad y 26.98 ±DE 4.26 kg de peso corporal, en un diseño experimental de bloques completos al azar. Los tratamientos fueron: 1) dietas a base de maíz y pasta de soya, con aporte nutrimental de acuerdo a la etapa productiva (testigo; n = 36); y 2) testigo más 0.2 % de extracto de TH (n = 36). Los cerdos fueron alojados en grupos de 3 hembras y 3 machos en 12 corraletas. A los datos se les aplicó un ANDEVA (P ≤ 0.05). Los cerdos que consumieron alimento adicionado con TH durante la fase de crecimiento (día 1 - 49), tuvieron mejor (P = 0.04) ganancia diaria de peso (GDP; 0.802 vs. 0.680 kg). En el periodo de finalización (día 50 - 90) la GDP y conversión alimenticia (CA) no fueron afectadas (P > 0.05) por el tratamiento. Al considerar los dos periodos juntos (crecimiento y finalización, del día 1 - 90 de prueba), la adición de TH tendió a aumentar (P = 0.06) en 12.91 % la GDP (0.782 vs. 0.681), y el peso final en 9.26% (97.17 vs. 88.17 kg; P = 0.06). Se concluye que el consumo de dietas con 0.2 % de extracto de TH, mejora la GDP de los cerdos en crecimiento-finalización criados bajo condiciones de estrés calórico
Respuesta al consumo adicional de zinc orgánico en la calidad seminal de ovinos de pelo
With the objective to evaluate the response of additional intake of different levels of organic zinc on the seminal quality of hair lamb, nine prepubertal lambs were used (between 3.5 to 4.5 months of age) with an average weight of 13 kg and assigned to one of three treatments in an experimental design completely randomized. The treatments consisted on 1) Control (C; n = 3); the lambs received a diet from corn-soybean meal-forage, without addition of organic zinc (Zn); 2) ZnMet35, control diet plus addition of 35 ppm zinc from Zn methionine (ZnMet); and 3) ZnMet70, control diet plus addition of 70 ppm Zn. The investigation was carried out between July 2009 and April 2010. The consumption of the diet supplemented with 70 ppm organic Zn raised the seminal volume (P<0.05), (0.9696 vs. 0.7773 y 0.6864 mL), and the total of spermatozoa per ejaculation (1955.9 vs. 1463 and 1301.1 millions), improved (P<0.05) the percentage of spermatozoa with normal morphology (92.870 vs. 89.045 and 86.818 %), as well as the plasmatic concentration of testosterone (403.87 vs. 332.12 and 264.59 ng/dL; p = 0.09) respect to the treatments that received a diet supplemented with 35 ppm of organic Zn, and the control group, respectively. It is concluded, that consumption of diet supplemented with 70 ppm of Zn from ZnMet, raises the ejaculated volume, quantity, quality of spermatozoa, and raises the plasmatic concentration of testosterone, in hair lambs breeding in the subtropical zone.Con el objetivo de evaluar la respuesta al consumo adicional de diferentes niveles de zinc orgánico en la calidad seminal de ovinos de pelo, se utilizaron 9 borregos prepúberes (entre los 3 ½ a 4 ½ meses de edad) con un peso promedio de 13 kg, los cuales fueron asignados a uno de tres tratamientos en un diseño experimental completamente al azar. Los tratamientos consistieron: 1) Testigo (T; n = 3), los borregos recibieron una dieta a base de maíz-soya-forraje, sin adición de zinc (Zn); 2) ZnMet35, dieta testigo más la adición de 35 ppm de Zn a partir de metionina de Zn (ZnMet) y 3) ZnMet70, dieta testigo más la adición de 70 ppm de Zn. La investigación se llevó a cabo entre los meses de julio de 2009 a abril de 2010. El consumo de dietas adicionadas con 70 ppm de Zn elevó (P < 0.05) el volumen del eyaculado (0.9696 vs. 0.7773 y 0.6864 mL) y la cantidad total de espermatozoides por eyaculado (1955.9 vs. 1463 y 1301.1 millones), mejoró (P < 0.05) el porcentaje de espermatozoides con morfología normal (92.870 vs. 89.045 y 86.818%) y elevó (P = 0.09) la concentración plasmática de testosterona (403.87 vs. 332.12 y 264.59 ng/dL) respecto de los borregos que consumieron dietas adicionadas con 35 ppm de Zn orgánico y los del grupo testigo, respectivamente. Se concluye que el consumo adicional de 70 ppm de Zn a partir de ZnMet eleva el volumen, la cantidad y calidad de espermatozoides del eyaculado, así como la concentración plasmática de testosterona en ovinos de pelo criados en condiciones subtropicales