2022, Zhou, M., Huynh, T.T.T., Groot Koerkamp, P.W.G., van Dixhoorn, I.D.E., Amon, T., Aarnink, A.J.A.

The focus of this study was to identify the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on heat loss from the skin surface and through respiration of dairy cows. Twenty Holstein dairy cows with an average parity of 2.0 ± 0.7 and body weight of 687 ± 46 kg participated in the study. Two climate-controlled respiration chambers were used. The experimental indoor climate was programmed to follow a diurnal pattern with ambient T at night being 9°C lower than during the day. Night ambient T was gradually increased from 7 to 21°C and day ambient T was increased from 16 to 30°C within an 8-d period, both with an incremental change of 2°C per day. A diurnal pattern for RH was created as well, with low values during the day and high values during the night (low: RH_l = 30-50%; medium: RH_m = 45-70%; and high: RH_h = 60-90%). The effects of AV were studied during daytime at 3 levels (no fan: AV_l = 0.1 m/s; fan at medium speed: AV_m = 1.0 m/s; and fan at high speed: AV_h = 1.5 m/s). The AV_m and AV_h were combined only with RH_m. In total, there were 5 treatments with 4 replicates (cows) for each. Effects of short and long exposure time to warm condition were evaluated by collecting data 2 times a day, in the morning (short: 1-h exposure time) and afternoon (long: 8-h exposure time). The cows were allowed to adapt to the experimental conditions during 3 d before the main 8-d experimental period. The cows had free access to feed and water. Sensible heat loss (SHL) and latent heat loss (LHL) from the skin surface were measured using a ventilated skin box placed on the belly of the cow. These heat losses from respiration were measured with a face mask covering the cow's nose and mouth. The results showed that skin SHL decreased with increasing ambient T and the decreasing rate was not affected by RH or AV. The average skin SHL, however, was higher under medium and high AV levels, whereas it was similar under different RH levels. The skin LHL increased with increasing ambient T. There was no effect of RH on the increasing rate of LHL with ambient T. A larger increasing rate of skin LHL with ambient T was observed at high AV level compared with the other levels. Both RH and AV had no significant effects on respiration SHL or LHL. The cows lost more skin sensible heat and total respiration heat under long exposure than short exposure. When ambient T was below 20°C the total LHL (skin + respiration) represented approx. 50% of total heat loss, whereas above 28°C the LHL accounted for more than 70% of the total heat loss. Respiration heat loss increased by 34 and 24% under short and long exposures when ambient T rose from 16 to 32°C.

2019, Herbut, Piotr, Angrecka, Sabina, Godyń, Dorota, Hoffmann, Gundula

A trend of global warming has been observed over the last few years and it has often been dis-cussed whether there is an effect on livestock. numerous studies have been published about heat stress in cattle and its influence on the physiology and productivity of animals. Preventing the negative effects of heat stress on cattle is essential to ensure animal welfare, health and produc-tivity. Monitoring and analysis of physiological parameters lead to a better understanding of the adaptation processes. This can help to determine the risk of climate change and its effects on performance characteristics, e.g. milk yield and reproduction. This, in turn, makes it possible to develop effective measures to mitigate the impact of heat load on animals. The aim of this article is to provide an overview of the current literature. studies especially about the physiological and productive changes due to heat stress in cattle have been summarised in this review. The direction of future research into the aspect of heat stress in cattle is also indicated

2019, Pinto, Severino, Hoffmann, Gundula, Ammon, Christian, Heuwieser, Wolfgang, Levit, Harel, Halachmi, Ilan, Amon, Thomas

The aim of this study was to evaluate the effects of evaporative cooling at two different frequen-cies per day on the respiration rate (rr) of lactating dairy cows, considering cow-related factors. twenty multiparous israeli holstein dairy cows housed in a naturally ventilated cowshed were di-vided randomly into two treatment groups. the cows of both groups were exposed to 3 or 8 cooling sessions per day (3xcool vs. 8xcool, respectively). the rr was observed hourly, with a maximum of 12 measurements per day. Body posture (standing vs. lying) was simultaneously documented. milk yield was recorded daily. coat color was determined from a digital photograph. the rr of standing and lying cows was lower in the 8xcool group (60.2 and 51.6 breaths per min (bpm), re-spectively) than in the 3xcool group (73.1 and 65.6 bpm, respectively). For each increment of five kilograms of milk produced, rr increased by one bpm, and the rr of cows in early days in milk (dim) was 12.3 bpm higher than that of cows in late dim. in conclusion, eight cooling sessions per day instead of three lead to a rr abatement in heat-stressed cows under hot conditions, and cow-related factors directly impact the rr during heat stress assessment