Search

Copyright of Investigación y Ciencia de la Universidad Autónoma de Aguascalientes is the property of Universidad Autonoma de Aguascalientes, Direccion General de Investigacion y Posgrado and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Con el objeto de evaluar algunas respuestas fisiológicas preparto y productivas posparto, se asignaron 24 vacas Holstein multíparas a dos tratamientos: con (n=12) y sin (n=12) sistema de enfriamiento durante su periodo seco en verano. Vacas enfriadas tuvieron menor (P<0.05) tasa respiratoria (77.5 vs 83.7) y menor (P<0.05) temperatura rectal (39.1 vs 39.3 °C) por la tarde, que vacas no enfriadas. Los niveles de T3 y T4 fueron mayores (P<0.05) en vacas enfriadas sobre no enfriadas (38.0 vs 30.2 y 0.857 vs 0.681 ng/ml, respectivamente). El peso nacimiento fue sólo numéricamente mayor (P=0.421) en vacas con enfriamiento (36.1 vs 34.6 kg). La producción de leche tendió a ser mayor (P=0.144) en vacas enfriadas (28.1 kg) sobre vacas no enfriadas (25.2 kg), mientras que el porcentaje de grasa fue mayor (P<0.05) en vacas enfriadas (3.2 %) sobre vacas testigo (2.9 %); como resultado, la producción de leche ajustada fue mayor (P<0.01) en vacas enfriadas sobre no enfriadas (28.6 vs 25.7 kg). Reproductivamente, sólo la concepción total fue mayor (P<0.05) en vacas enfriadas sobre no enfriadas (100 vs 63.6 %). El grupo no enfriado presentó 42 % de tasa de desecho, y en el grupo enfriado fue de cero. El análisis económico mostró un beneficio de $ 770.50 vaca/año. Estos resultados demuestran que el uso de sistemas de enfriamiento 60 días preparto reduce el estrés calórico en vacas Holstein, y puede impactar positivamente en la productividad posparto, lo cual origina mayores beneficios económicos para el productor. [ABSTRACT FROM AUTHOR]

In order to determine some physiological responses 60 d prepartum and production responses postpartum to a cooling system in summer, 24 multiparous Holstein cows were allocated to two groups: one group with (n=12) and a second group without (n=12) cooling. Cooled cows showed a lower (P<0.05) respiration rate (77.5 vs 83.7 breaths/min) and rectal temperature (39.1 vs 39.3 °C) in the afternoon, than non-cooled (control) cows. Serum thyroxin and triiodothyronine levels were higher (P<0.05) in cooled cows than in non-cooled cows (38.0 vs 30.2 ng/ml and 0.857 vs 0.681 ng/ml, respectively). Calf birth weight showed only a numerical trend to be higher (P=0.421) in cooled cows (35.7 vs 32.9). Milk production showed a tendency (P=0.144) to be higher in the cooled (28.1 kg) than in the non-cooled group (25.2 kg), while fat content (P<0.05) was greater in the cooled (3.2 %) than in the non-cooled group (2.9 %); therefore, average fat-corrected milk production at week eight postpartum was higher (P<0.01) for the cooled group (28.6 vs 25.7 kg) compared to control. However, milk production and protein percent were similar (P>0.05). Reproductively, only total conception rate was higher (P<0.05) in cooled cows than in non-cooled cows (100 vs 63.6 %). Non-cooled cows showed a 42 % culling rate, while no cow was culled in the cooled group (P<0.05). An economic analysis showed a net profit of 75 dollars cow/year for the cooling system. Results show that cooling dry cows reduce heat stress, that resulted in higher fat-corrected milk and milk fat production in the subsequent lactation and in higher economical benefits for dairy producers. [ABSTRACT FROM AUTHOR]

In view of the problem of global warming and climate change, small ruminants may be key to maintain animal protein production since they are more heat stress tolerant than most other domestic animals. Hair breed sheep are known for their ability to grow and reproduce under conditions of high temperatures and low nutrient availability. Their adaptation to heat stress involves a complex interaction between thermoregulation mechanisms and the presence of genetic factors. These confer physiological plasticity to these breeds, allowing them to tolerate hot climates without drastically affecting their productivity. In Mexico, hair sheep are distributed in different climates throughout the country. The lack of strict reproductive seasonality in these breeds has allowed the sheep industry to maintain constant mutton production year-round. Very limited research has addressed hair breeds' ability to produce under heat stress conditions. The present review describes the effects of heat stress on reproductive performance, lamb growth and thermoregulation in hair sheep breeds. [ABSTRACT FROM AUTHOR]

Evaluation of the effects of an open space cooling system on weight gain, respiration rate and serum thyroid hormone (T3 and T4) levels in feedlot steers was done using 60 Holstein steers (344 kg) allotted randomly in two treatments: a control with only shade in the corral (n = 30); and a cooling with an open space cooling system (n = 30). Daily maximum temperature-humidity index (THI) ranged from 82 to 88 during the 12-week study period. The open space cooling system consisted of a fan with 2.4 m diameter blade that displaced 1,416 m³ of air per minute and had a 90° oscillation range, and sprinklers. The fan was installed at 8 m distance on the south side of the shade. Water discharge was 12 L per minute over a 7 h period. Body weight and thyroid hormone levels were measured every two weeks and respiration rate twice a week (1400). Data were analyzed by repeated measures, including initial weight as a covariate. Daily weight gain was different (P<0.05) between the cooling treatment (1.43±0.091 kg/d) and the control treatment (1.25±0.091 kg/d). Respiration rate was lower (P<0.05) in steers in the cooling treatment (94±0.74 breaths per minute) than in those in the control treatment (111±0.74 breaths per minute). Levels of T3 were higher (P<0.05) in the cooling treatment (1.7±0.042) than in the control (1.5±0.042). Levels of T4 were similar between the cooling (79.3±1.82 ng/ml) and control (78.2±1.82 ng/ml) treatments. Use of this cooling system improved production performance and comfort in feedlot Holstein steers in a hot, dry climate. [ABSTRACT FROM AUTHOR]

Con objeto de evaluar el efecto de un sistema de enfriamiento a espacio abierto sobre la ganancia de peso, frecuencia de respiración y niveles sanguíneos de triiodotironina (T3) y tiroxina (T4) durante el verano, 60 novillos Holstein fueron asignados aleatoriamente a un grupo testigo con únicamente sombra y un segundo grupo con sombra, más enfriamiento. Durante el experimento se registró un Índice de temperatura-humedad máximo que oscilo entre 82 a 88. El sistema de enfriamiento colocado a 8 m a partir de la sombra, consistió de una hélice de 2.4 m de diámetro produciendo 1,416 m³/min de aire con una rotación de 90° y un flujo de agua de 12 L/min. El peso corporal y los niveles de hormonas fueron registrados cada dos semanas, mientras la frecuencia de respiración (1400) en dos ocasiones por semana. Los datos fueron analizados con un diseño de mediciones repetidas, incluyendo el peso inicial como covariable. La ganancia de peso fue mayor (P<0.05) en el grupo con enfriamiento (1.43±0.091 kg/animal/día) que en el testigo (1.25±0.091 kg/animal/día). La frecuencia respiratoria expresada en respiraciones por minuto difirió (P<0.01) entre el grupo testigo (111±0.74) y enfriamiento (94±0.74). El grupo con enfriamiento obtuvo mayores (P<0.05) niveles de T3 (1.7±0.042 ng/ml) en comparación al testigo (1.5±0.042 ng/ml); sin embargo, los niveles de T4 fueron similares entre el enfriamiento (79.3±1.82 ng/ml) y el testigo (78.2±1.82 ng/ml). El enfriamiento artificial puede ser una alternativa para incrementar la eficiencia productiva y el confort de novillos Holstein en verano. [ABSTRACT FROM AUTHOR]