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.

The object of the present review is to analyze the methodologies that are commonly used to estimate protein degradability in the rumen, focusing on their attributes and limitations to offer suggestions for improving their use. This information is essential for selecting food types when formulating feed diets. A reliable prediction of the digestibility of ruminal proteins is basic information necessary for optimizing the use of nitrogenous sources because digestibility can translate, on the one hand, into higher yields of milk, milk protein, meat or wool and, on the other hand, into lower excretion of nitrogenous compounds into the environment; it also has an impact on animal health and welfare. Traditionally, the digestibility of feed proteins in the rumen has been predicted by in vivo , in situ and in vitro methods, but other techniques based on infrared spectroscopy have been developed, notably the NIRS and FTIR methods. All of these techniques present limitations, such as a disturbance factor or a source of error, that may result in inaccurate predictions. The in situ and in vitro methods, which use enzyme extracts of ruminal origin, and FTIR probably have the greatest advantages, but they need to be perfected through further research. El objetivo de esta revision es analizar las metodologias comunmente usadas para estimar la degradabilidad de las proteinas en el rumen, resaltando sus atributos y limitaciones en orden a ofrecer algunas sugerencias para mejorar su utilizacion. Esta informacion es esencial para seleccionar los tipos de alimentos cuando se formulan las dietas alimenticias. Una confiable prediccion de la digestibilidad de las proteinas en el rumen constituye una informacion basica para optimizar el uso de los recursos nitrogenados, pudiendo por un lado traducirse en una mayor produccion de leche, proteina lactea, carne o lana, y por otro, en una menor excrecion de compuestos nitrogenados al ambiente; esta mayor eficiencia tambien tiene un impacto sobre la salud y el bienestar animal. Tradicionalmente, la digestibilidad ruminal de las proteinas de los alimentos ha sido predicha a traves de metodos in vivo , in situ e in vitro . Sin embargo, otras tecnicas han sido desarrolladas, basadas sobre espectroscopia infraroja, destacando los metodos NIRS y FTIR. Todas estas tecnicas presentan limitaciones, factores perturbadores o fuentes de error, las cuales podrian generar predicciones sesgadas e inseguras. Los metodos in situ e in vitro , utilizando extractos enzimaticos de origen ruminal, y FTIR, probablemente poseen las mayores ventajas, no obstante, estas tecnicas requieren ser perfeccionadas a traves de futuras investigaciones.

The objective of this study was to compare the prediction efficiency of IgG concentration in bovine colostrum by NIRS, using liquid and dried (Dry-Extract Spectroscopy for Infrared Reflectance, DESIR ) samples by transflectance and reflectance modes, respectively. Colostrum samples (157), obtained from 2 commercial Holstein dairy farms, were collected within the first hour after calving and kept at −20 °C until analysis. After thawing and homogenisation, a subsample of 500 mg of liquid colostrum was placed in an aluminium mirror transflectance cell (0·1 mm path length), in duplicate, to collect the spectrum. A glass fiber filter disc was infused with another subsample of 500 mg of colostrum, in duplicate, and dried in a forced-air oven at 60 °C for 20 min. The samples were placed in cells for dry samples to collect the spectra. The spectra in the VIS-NIR region (400–2500 nm) were obtained with a NIRSystems 6500 monochromator. Mathematical treatments, scatter correction treatments and number of cross-validation groups were tested to obtain prediction equations for both techniques. Reference analysis for IgG content was performed by radial immunodiffusion. The DESIR technique showed a higher variation in the spectral regions associated with water absorption bands, compared with liquid samples. The best equation for transflectance method (liquid samples) obtained a higher coefficient of determination for calibration (0·95 vs. 0·94, respectively) and cross validation (0·94 vs. 0·91, respectively), and a lower error of cross validation (9·03 vs. 11·5, respectively) than the best equation for reflectance method (DESIR samples). In final, both methods showed excellent capacity for quantitative analysis, with residual predictive deviations above 3. It is concluded that, regarding accuracy of prediction and time for obtaining results of IgG from bovine colostrum, NIRS analysis of liquid samples (transflectance) is recommended over dried samples (DESIR technique by reflectance).

Nutritional recommendations of the past 35-40 years have promoted the reduction of fat intake, calories and particularly saturated fatty acids (SFA), emphasizing lower consumption of red meat and high fat dairy products, because of its association with cardiovascular diseases (CVD), being in turn replaced by sugars and refined carbohydrates. There is consensus that the SFA concentration in blood plasma, particularly palmitic acid, are associated with an increased risk of CVD and heart attacks. However, there is no evidence of causality between CVD and consumption of SFA, raising reasonable doubts about the relationship between consumption of SFA with those present in blood plasma, as well as with the CVD risk. This review presents scientific evidence that demonstrates that the inclusion of fats in the diet, specifically animal fats from ruminants, provide important health benefits for people, especially when accompanied by a reduction in the consumption of carbohydrates. It is also proposed that ruminant products and their fatty acids contribute with beneficial saturated fats for people's health, especially those from pastoral production systems such as vaccenic, rumenic and linolenic acids.