Evaluación económica de dos variaciones de un tratamiento lactoinductor en vaquillas de reemplazo en un sistema de doble propósito tropical / Economic evaluation of two variations of a hormonal induction treatment in replacement heifers in a tropical dual purpose system

The aim of this study was to evaluate the productivity and profitability of two commercial sources of progesterone therapy as part of a hormonal induction treatment in a heifer dual purpose herd. A second objective was to determine the productivity and profitability of a recombinant bovine somatotropin (ST) application during induced lactation. Forty four Holstein heifers x Zebu crosses were used. Four treatments and two control groups were evaluated. For economic analysis all components of total cost (TC) of the companies were considered, further there was a simulation which was designed for three natural lactations after the hormonal induction, based on two scenarios in which different body weights were considered as different periods. Artificial induction of lactation yielded a 100% success rate in the four groups of animals with no statistical differences between them (P > 0.05). The best cost-benefit ratio (CBR) was recorded by CIDR treatment without ST. Although the four treatments showed economic viability, those without ST had a better ratio (B / C) than those supplemented with ST. As for the net present value (NPV), the benefits updated showed that the profits were higher when ST was not applied and, mainly, in the CIDR treatment. The internal rate of return (IRR) reveals that most of the treatments have a yield above 20%.

Los objetivos del presente trabajo fueron: 1) evaluar la productividad y rentabilidad de dos fuentes comerciales de progesterona como integrantes de un tratamiento lactoinductor en vaquillas de reemplazo de un hato de doble propósito y 2) determinar la productividad y rentabilidad de la aplicación de somatotropina bovina recombinante (ST) durante la lactación inducida. Se usaron 44 novillonas producto de cruzas Holstein x Cebú. Se evaluaron cuatro tratamientos y se manejaron dos grupos testigo. Para el análisis económico se consideraron todos los componentes del costo total (CT) de las empresas, adicionalmente se realizó una simulación en la que se proyectó para tres lactaciones naturales posteriores a la lactoinducción, basadas en dos escenarios en los que se consideraron diferentes pesos corporales como diferentes periodos. En los cuatro grupos de animales lactoinducidos, el 100% de las vaquillas respondió al tratamiento sin diferencias estadísticas entre ellas (P > 0.05). La mejor relación beneficio-costos (RBC) la registró el tratamiento CIDR sin ST. Si bien los cuatro tratamientos presentaron viabilidad económica, los tratamientos sin ST presentaron mejor relación (beneficio/costo) que aquellos tratamientos que sí fueron complementados con ST. En cuanto al valor actual neto (VAN), los beneficios actualizados de todos los años muestran que las utilidades que generaron los tratamientos fueron superiores cuando no se aplicó ST y, principalmente, en el tratamiento con CIDR. La tasa interna de rentabilidad (TIR) revela que la mayoría de los tratamientos tienen una rentabilidad arriba del 20%.

Effects of adrenocorticotropic hormone challenge and age on hair cortisol concentrations in dairy cattle.

Dairy cattle suffer stress from management and production; contemporary farming tries to improve animal welfare and reduce stress. Therefore, the assessment of long-term hypothalamic-pituitary-adrenal function using non-invasive techniques is useful. The aims in this study were: to measure cortisol concentration in cow and calves hair by radioimmunoassay (RIA), to test cortisol accumulation in bovine hair after adrenocorticotropic hormone (ACTH) challenges, and determine the influence of hair color on cortisol concentrations. Fifteen Holstein heifers were allotted to 3 groups (n = 5 each): in control group (C), just the hair was sampled; in the saline solution group (SS), IV saline solution was administered on days 0, 7, and 14; and the ACTH group was challenged 3 times with ACTH (0.15 UI per kg of body weight) on days 0, 7, and 14. Serum samples from the SS and ACTH groups were obtained 0, 60 and 90 min post-injection. Serum cortisol concentration was greater 60 and 90 min after injection with ACTH. Hair was clipped on days 0, 14, 28, and 44. Hair cortisol was methanol extracted and measured by RIA. Hair cortisol was preserved for 11 mo. Hair cortisol concentrations in the ACTH group were greater than in the saline and control groups on days 14 and 28, but not on day 44. Concentrations were greater in calves than in cows and greater in white hair than in black hair. Cortisol accumulated in bovine hair after ACTH challenges, but the concentration was affected by both age and hair color. If hair color effects are taken into account, assessing cortisol concentration in hair is a potentially useful non-invasive method for assessing stress in cattle.

[Experimental model of canine oleic acid-induced acute lung injury: establishment of a working model]. / Modelo experimental canino de daño pulmonar agudo producido con ácido oleico: estableciendo un modelo de trabajo.

INTRODUCTION: There are several experimental model of acute lung injury induced by oleic acid (OA); however, there are few studies that show how this injury develops. OBJECTIVE: This study seeks to detail the x-ray, hemodynamic, gasometrical, gravimetrical, macroscopic and microscopic alterations developed in an experimental model of canine OA-induced acute lung injury (ALI). MATERIAL AND METHODS: Twelve dogs were divided in 2 study groups: Group I (n=6): Control group without ALI. Group II (n=6); OA-induced ALI. All dogs were submitted to X-ray, hemodynamic and gasometric evaluation before ALI induction, and later every 15 minutes during 150 minutes. At the end of the study, the animals were euthanatized and were evaluated the changes gravimetric, macroscopic and microscopic in injured lungs. RESULTS: All the animals survived through the study. In group II, 100% of the animals developed x-ray (p < 0.003 Wilcoxon), hemodynamic, gasometrical and gravimetric (p < 0.5 ANOVA, Tukey), macroscopically and microscopically (p < 0.001 Wilcoxon) ALI. CONCLUSIONS: The OA-induced ALI is a model in which dogs develop X-ray, hemodynamic, gasometrical, gravimetrical, macroscopically and microscopically injuries of the exudative phase that lung with ALI injury presents.

Vampire bat reproductive control by a naturally occurring phytooestrogen.

Rabies transmission by wild animals has not being controlled satisfactorily. One major rabies vector to humans and cattle is the hematophagous vampire bat Desmodus rotundus whose distribution is still increasing in the Americas. Of all of the strategies currently in place to control this vector, none of them are really specific and some have ecological impacts. In the present study we used a naturally occurring phytoestrogen on a small vampire bat colony. After collection, bats were fed bovine blood containing 200 microg coumestrol for a 30-day period. After treatment, gonads were excised and processed for histological evaluation. Data indicate that coumestrol adversely affects gonad histology and has a possible impact on the fertility of both male and female vampire bats.

Efecto de la Naloxona sobre la secreción pulsátil de la hormona luteinizante en vacas de doble propósito con doble ordeño y amamantamiento / Effect of Naloxone over the secretion of the Luteinizing Hormone on double purpose cows with double milking and suckling

Se examinó el efecto de cero, una y tres inyecciones de naloxona (NX; 500 mg) el día 30 posparto a intervalos de 1 h, sobre la liberación de la hormona luteinizante (LH), en vacas de doble propósito en anestro: ¾ Europeo x » Cebú (n = 18). Las vacas pastorearon en zacate Estrella de África (Cynodon plectostachyus) y gramas nativas (Axonopus y Paspalum spp.) con un consumo de 5 kg de alimento balaceado diariamente (16 % de PC). El ordeño fue mecánico dos veces al día y se realizó amamantamiento de las crías después del ordeño (30 min). Las vacas y las crías permanecieron separadas, excepto durante el amamantamiento. Se colectó una muestra de sangre cada 2 días desde el parto hasta el día 30 posparto y se cuantificó la progesterona (P) sérica por RIA. El anestro fue indicado por P < 1 ng/ml. El día 30 posparto se tomaron muestras de sangre cada 15 min durante 3 horas: una hora después de cada inyección de NX o solución salina fisiológica y se cuantificó la LH sérica por RIA. Las variables de respuesta fueron: concentración media (MLH) y basal (BLH), número (NP), amplitud (AP) y duración (DP) de pulsos de LH. Se usó un ANDEVA con parcelas divididas, parcela mayor = tratamiento y subparcela = período de muestreo. No hubo efectos (p >0.05) de tratamiento, período y sus interacciones en las variables de respuesta. En vacas de doble propósito con doble ordeño y amamantamiento, la naloxona no cambió la secreción de la LH en el día 30 posparto.

This study determined the effect of zero, one and three intramuscular injection of naloxone (NX, 500 mg) on 30 postpartum day for 1 hour intervals over the release of the luteinizing hormone in dual purpose cows in anestrous (¾ Europe x » Zebu) cows (n =18). The cows grazed on African Star grass (Cynodon plectostachyus) and native grass (Axonopus and Paspalum spp) and ate daily 5 kg of balanced food (16% crude protein). The cows were mechanically milked twice a day and after that their calves were allowed to suck for 30 minutes. A blood sample was collected every two days, from the delivery until 30 days postpartum for the quantification of progesterone (P) by RIA. In this blood anestrous was indicated by P< 1 ng/ml. On day 30 postpartum blood samples were drawn every 15 min during 3 hours: one hour after each naloxone injection or saline solution and Luteinising Hormone (LH) was measured by RIA. The response variables were mean (MLH) and basal concentration (BLH), number (PN), amplitude (PA) and pulse duration (PD) of LH. The statistic analysis was divided plot; principal plot was the treatment and secondary plot was the samples period. There were not effects (p>0.05) of treatment, samples period and its interactions on response variables. In double purpose cows with double milking and suckling naloxona did not affect the LH secretion at 30 day pospartum.

Sistemas neurales de retroalimentación durante el ciclo reproductivo anual de la oveja: una revisión / Neural feedback systems during the annual reproducctive cycle of the ewe: a review

El ciclo reproductivo anual de la oveja es regulado por la amplitud del fotoperiodo. La señal luminosa se traduce en una señal hormonal a través de la síntesis de melatonina. La disminución en la duración del fotoperiodo induce la actividad reproductiva y el aumento en las horas luz, inhibe la actividad ovulatoria estral, la conducta de estro y la ovulación (anestro estacional). Durante la época reproductiva, la progesterona (P4) regula los ciclos estrales de la oveja inhibiendo la secreción pulsátil de la hormona liberadora de gonadotropinas (GnRH) a nivel del área preóptica (POA) del hipotálamo, donde ejerce su acción de manera indirecta, posiblemente a través del ácido gama amino butírico (GABA) y los péptidos opioides endógenos (POEs). En la fase folicular del ciclo estral, el estradiol (E2) ejerce un efecto de retroalimentación positiva a nivel del hipotálamo mediobasal (HMB), incrementa la secreción pulsátil de GnRH y de la hormona luteinizante (LH), e induce el pico preovulatorio de ambas hormonas, provocando la conducta de estro y la ovulación. Durante la época de anestro estacional, el patrón de secreción de melatonina favorece el aumento en la sensibilidad del hipotálamo a la concentración basal de E2; este esteroide inhibe la secreción pulsátil de GnRH, actuando específicamente en el núcleo A15 dopaminérgico del área retroquiasmática lateral (Arch) hipotalámica. En este mecanismo, el sistema dopaminérgico participa como intermediario entre el E2 y las neuronas GnRH