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Heat stress and a high metabolic rate of broilers increase the production of reactive oxygen species, which must be removed by antioxidants to prevent oxidative stress. Selenium (Se) is a potent antioxidant as it is a structural part of glutathione peroxidase (GPx). Dietary supplementation of Se can help reduce the oxidative stress caused by heat-stress conditions. The aim was to evaluate the effect of Se supplementation on the performance and antioxidant status of broilers under heat stress, by using a meta-analysis approach, and to quantify the contribution to heterogeneity of the explanatory variables through a meta-regression procedure. A database of 74 trials was created from 56 published studies that met the following inclusion criteria: papers that reported a measure of effect size, sample size, measure of variability and random procedure. The response variables were GPx and malondialdehyde concentrations, DM intake, average daily gain, and feed conversion rate. Broiler line, Se source, and dosage, heat-stress level, days of experimentation, sample source (blood, liver or meat) and basal Se concentration were considered to be explanatory variables. All statistical analyses were performed in R software, by using the ‘meta’ and ‘Metafor’ packages for meta-analysis and meta-regression respectively. High concentrations of GPx were found in Se-supplemented broilers (>1.76; P = 0.001), in comparison to control groups. However, when the random model was applied to GPx studies, it showed high heterogeneity (I2 = 95.4%), which was reduced (I2 = 61.5) when heat-stress temperature, Se source and its dosage and tissue sample were included as covariates in the meta-regression analysis. The highest standard mean difference of GPx was founded in studies that reported supplementation with inorganic Se sources (2.92), in comparison to supplementation with organic and nano-Se sources (1.66 and 1.44 respectively). The standard mean differences of malondialdehyde and feed conversion rate were significantly lower (

Automated systems for monitoring the behavior of cows have become increasingly important for management routines and for monitoring health and welfare. In the past few decades, various devices that record rumination have been developed. The aim of the present study was to compare rumination activity measured with a commercially available rumination collar (RC) against that obtained by direct visual observations and analysis of video recordings in commercial dairy cows. Rumination time from video recordings was recorded by a trained observer. To assess observer reliability, data were recorded twice, and the duration of recorded behaviors was very similar and highly correlated between these 2 measurements (mean = 39 ± 4 and 38 ± 4 min/2 h). Measurements of rumination time obtained with RC when compared with analysis of video recordings and direct observations were variable: RC output was significantly positively related to observed rumination activity when dealing with animals housed indoors (trial 1 video recordings: slope = 1.02, 95% CI = 0.92–1.12), and the limits of agreement method (LoA) showed differences (in min per 2-h block) to be within −26.92 lower and 24.27 upper limits. Trial 1 direct observations: slope = 1.08, 95% CI = 0.62–1.55, and the LoA showed differences to be within −28.54 lower and 21.98 upper limits. Trial 2: slope = 0.93, 95% CI = 0.64–1.23, and the LoA showed differences to be within −32.56 lower and 19.84 upper limits. However, the results were poor when cows were outside grazing grass (trial 3: slope = 0.57, 95% CI = 0.13–1.02, and the LoA showed differences to be within wider limits −51.16 lower and 53.02 upper). Our results suggest that RC can determine rumination activity and are an alternative to visual observations when animals are housed indoors. However, they are not an alternative to direct observations with grazing animals on pasture and its use is not advisable until further research and validation are carried out.

The aims of the present study were to evaluate the effects of live yeast supplementation (Vistacell MUCL 39855, AB Vista, Marlborough, England UK) on performance, rumination time and rumen pH on dairy cows in commercial farm environments. Three Trials were carried out, the trials lasted: trial 1 = 12 weeks, trial 2 = 15 weeks and trial 3 = 19 weeks. In each trial, 14 multiparous Holstein dairy cows were allocated to two groups that received a) Trial 1 a standard diet plus yeast b) Trial 2 an acidogenic diet plus yeast and c) Trial 3 grazing pasture plus yeast. Milk production, milk chemical characteristics, body weight and body condition score, rumination time and rumen pH were monitored for each group throughout the three Trials. No statistically significant differences were observed in any of the three Trials for any of the recorded variables (P > 0.05). In contrast, an effect of time (Period or days in milk) on rumen pH was observed in all three of the Trials as time spent under the acidotic thresholds increased across the experimental periods (P < 0.05); however the differences were not associated with live yeast supplementation (P > 0.05). No effect of live yeast supplementation was observed in any of the three Trials reported. Further research should include studies on animals at different stages of lactation (with emphasis on transition period and early lactation), consuming more challenging diets (higher level of inclusion of concentrates or starch), or under different environments such as grazing of succulent forages. Such studies might be required to elucidate any possible effect of live yeast supplementation of dairy cows when the rumen environment is under challenge.