Fernando González

Evidence of Fractality in a Pattern of Crystallization of Bovine Cervical Mucus Obtained at Oestrus

La fractalidad ha surgido como una caracteristica propia de algunos sistemas biologicos complejos. Varias secreciones biologicas presentan patrones de tipo fractal al cristalizar; no obstante, su presencia en las cristalizaciones de moco cervical bovino aun se desconoce. Con el objetivo de investigar la presencia de fractalidad en las cristalizaciones de moco cervical bovino, se obtuvieron muestras de este fluido de vaquillas en estro, fotografiandose los patrones cristalinos observados. Entre las tipicas disposiciones similares a frondas de helechos observadas para la cristalizacion del moco cervical, se encontro una imagen con un arreglo geometrico altamente simetrico, constando de tres zonas caracterizadas por estructuras arborescentes similares a pinos, muy semejantes entre si. Mas aun, las dimensiones fractales obtenidas para esas zonas fueron estadisticamente iguales al ser dichas areas analizadas con un programa computacional apropiado. En resumen, esta comunicacion breve demuestra por primera vez que uno de los patrones de cristalizacion de moco cervical bovino en estro esta caracterizado por una organizacion de tipo fractal.

Physiological and behavioural response of two dairy cows’ genotypes during summertime in the central region of Chile

ABSTRACT: Heat stress has been recognised as a serious problem in dairy farms. The study goal was to assess the effects of climatic conditions on physiological and behavioural responses of dairy cows in Central Chile. Data of tympanic temperature (TT), panting score, respiration rate (RR), and shade utilization of cows from two genotypes, Holstein (H) and Holstein x Montbeliarde (HM), were collected twice per day (AM/PM) during three periods of the summer season in Central Chile. Moreover, three thermal comfort indices: Comprehensive climate index (CCI), temperature humidity-index (THI), and adjusted THI were estimated using meteorological data. The hour of each day was classified as “Normal” or “Stressful” based on CCI threshold of 25 °C. Statistical analysis included ANOVA, repeated measures analysis and Chi square test (a=0.05). There was an interaction of genotype x CCI condition x period (P=0.0026) with the highest TT of both genotypes under a stressful condition within each period. In addition, interactions of genotype x hour (P<0.0001) and genotype x CCI condition (P<0.0002) were also observed. The HM cows showed greater TT than H cows in both CCI conditions. The RR was higher during the afternoon and a greater proportion of cows used shade at “Mild” and “Moderate” CCI categories (P<0.001). Both genotypes showed some degree of heat stress, but cool nights and shade seem to be enough to allow to cows’ cope with the challenging diurnal conditions observed in the summer season. A study of these effects on milk production is necessary to confirm or discard the previous.