Metabolic conditions of lactating Friesian cows during the hot season in the Po valley. 2. Blood minerals and acid-base chemistry

In two consecutive summers, 21 and 18 cows respectively were monitored for acid-base chemistry and some blood minerals, to assess their variation according to the level of heat stress at different stages of lactation. During both years, the cows were monitored according to their lactation phase (early, mid-, and late) at the beginning of the summer. Climatic conditions were described through the temperature humidity index. Cows were monitored weekly for: breathing rate, rectal temperature, hemogas parameters and blood minerals (morning and afternoon collection). In the first year, two hotter periods were identified, with more severe conditions in the second one, when cows had rectal temperatures higher than 40°C. In the second year, only one hotter period was identified, with a heat stress comparable to that of the first period of the first year. The behaviour of rectal temperature, breathing rate and the parameters of the acid-base status indicated that the suffering of the cows was on the borderline between mild and high heat stress during the hotter periods only, according to the climatic conditions in the two years. During the hotter periods, the acid-base chemistry differed significantly with a reduction of and an increase of Cl during the hotter hours of the day. The compensation mechanism for mild alkalosis during hotter hours maintained blood pH and the returned to normal values during the night. Significant reductions were observed for Mg and Zn during the hotter periods. The cows in late lactation appeared to be less stressed by the hot climate.     

Effects of feeding supplemental palmitic acid (C16:0) on performance and milk fatty acid profile of lactating dairy cows under summer heat

The objective was to determine performance and milk fatty acid changes of high producing dairy cows in early lactation, under summer heat, by adding a supplemental rumen inert fat in the form of a saturated free fatty acid (856 g/kg C16:0/kg of total fatty acids) to the total mixed ration (TMR). Early lactation multiparous Holstein cows in two similar pens of 99 and 115 cows were used in a 2 × 2 Latin Square design experiment with 35 d periods during a period when daily high and low temperatures averaged 34.3 and 15.9 °C, the relative humidity averaged 51% and there were no rain events. The TMR was the same for both groups, consisting of approximately 435 g/kg forage and 565 g/kg concentrate, except that the vitamin/mineral premix had no added fat (control, C) or added fat (C16:0) at a level designed to deliver approximately 450 g/cow/d of supplemental fat if cows consumed 26.5 kg/d of dry matter (DM). The two TMR averaged 905 g/kg organic matter (OM), 318 g/kg neutral detergent fiber (aNDF), and 186 g/kg crude protein (CP). The ‘C’ TMR had 58 g/kg total fatty acids with an estimated net energy for lactation (NE_l) of 7.3 MJ/kg (DM), while the C16:0 TMR had 72 g/kg total fatty acids and 7.5 MJ/kg NE_l (DM). Whole tract digestibility of DM, OM, aNDF and CP tended (P<0.10) to increase, and that of fatty acids increased substantially (P<0.01), with C16:0 feeding, whereas, DM intake was not affected. Milk fat content decreased (P<0.01) with C16:0 feeding (37.5 versus 36.0 g/kg), whereas, true protein content tended (P=0.09) to increase. There was a tendency (P=0.07) for increased milk yield (36.69 versus 38.04 kg/d), while milk protein yield increased (P=0.03) with C16:0 supplementation (1.08 versus 1.13 kg/d). Milk fat yield was unaffected by treatment. Concentrations of short and medium chain milk fatty acids (C6:0–C15:0), decreased, or tended to decrease, with C16:0 addition (C13:0 and C15:0, P<0.10; all others, P≤0.05). The concentration of C16:0 increased (P<0.001) in milk triglycerides from cows fed C16:0 (27.10 versus 31.57 g/kg), the longer chain saturated fatty acids C17:0 and C18:0 decreased (P≤0.05) and other long chain unsaturated fatty acids were unaffected. Benefits of C16:0 feeding on cow productivity must be balanced against negative effects on the nutritive value of the milk (i.e., increased C16:0 in milk fatty acids) produced for human consumption. However, relatively low amounts of supplemental C16:0 (27.10 versus 31.57 g/kg in milk triglycerides for C and C16:0 supplemented cows, respectively) were actually secreted in milk, in spite of them being essentially fully digested in the digestive tract. Strategies to divide cows into production groups based on milk yield and/or milk fat proportions could further limit C16:0 secretion in milk. Supplemental dietary C16:0 may have positive effects on milk production that outweigh the negative health effects of the increased C16:0 content in the milk fat.     

Effects of evaporative cooling on reproductive performance and milk production of dairy cows in hot wet conditions

Fourteen animals of second and third lactation of Thai Friesian crossbred cows (87.5% Friesian × 12.5% Bos indicus) located at Sakol Nakhon Research and Breeding Centre, Department of Livestock Development, Ministry of Agriculture and Cooperatives, were divided randomly into two groups of seven each to evaluate the effects of evaporative cooling on reproductive and physiological traits under hot, humid conditions. Results indicated that installation of evaporating cooling in the open shed gave a further improvement in ameliorating heat stress in dairy cows in hot-wet environments by utilising the low humidity conditions that naturally occur during the day. The cows housed in an evaporatively cooled environment had both a rectal temperature and respiration rate (39.09°C, 61.39 breaths/min, respectively) significantly lower than that of the non-cooled cows (41.21°C; 86.87 breaths/min). The former group also had higher milk yield and more efficient reproductive performance (pregnancy rate and reduced days open) than the latter group. It is suggested that the non-evaporatively cooled cows did not gain benefit from the naturally lower heat stress during night time.     

Daily rumination time of lactating dairy cows under heat stress conditions

The dairy industry in regions with moderate climates, such as Central Europe, will be increasingly challenged in the future by climate change. The problem of heat stress will especially affect dairy husbandry in naturally ventilated barns (NVB). The approach of the study was to determine a heat stress threshold of the average daily temperature-humidity index (THI) that results in changes in the daily rumination time (RT) of lactating, high-yielding cows. The data set was composed of a high sample size of 183 cows and long-duration measurements of 21240 daily observations over two years from June 2015 to May 2017, which were collected in an NVB in Groβ Kreutz, Germany. The THI was calculated in 5-min intervals by data from several sensors in different positions inside the barn. Additionally, every cow from the herd of an average of 53 cows in the experimental procedure was wearing a neck collar with a Lely Qwes HR system that provided the RT 24 h a day (12 2-h recordings were summarized). The study showed that heat stress also negatively influenced RT in moderate climates. The heat stress threshold of 52 THI was determined by broken-stick regression and indicated changes of RT of lactating dairy cows in Germany. During the experimental period, the heat stress threshold for RT was reached from April to September for up to 720 h per month. The changes in RT to the heat stress threshold will be affected by cows' characteristics. Therefore, we considered several cow-related factors, such as milk yield (MY), lactation number (LN), lactation stage (days in milk, or DIM) and pregnancy stage (P) to better understand cows’ individual reactions to heat stress. Multiparous, high-yielding cows in later lactation stages are potentially more strongly affected than other cows.     

The effect of fiber characteristics on thermoregulatory responses and feeding behavior of heat stressed cows

We examined the effect of replacing wheat hay with soy hulls on thermoregulatory responses and feeding behavior under summer condition in dairy cows. Milk yield, feed intake, meal size, and number, heart rate and heat production were similar in the two dietary groups. Visit duration and time spent eating were shorter, and body temperature was higher in the soy hulls fed cows. It was concluded that supplying soy hulls can enable cows subjected to heat load conditions to reduce the costs of feed ingestion. However, the contribution of this tool to the overall energy budget is rather small.     

Genotype effects on body temperature in dairy cows under grazing conditions in a hot climate including evidence for heterosis

We compared diurnal patterns of vaginal temperature in lactating cows under grazing conditions to evaluate genotype effects on body temperature regulation. Genotypes evaluated were Holstein, Jersey, Jersey × Holstein and Swedish Red × Holstein. The comparison of Holstein and Jersey versus Jersey × Holstein provided a test of whether heterosis effects body temperature regulation. Cows were fitted with intravaginal temperature recording devices that measured vaginal temperature every 15 min for 7 days. Vaginal temperature was affected by time of day (P < 0.0001) and genotype × time (P < 0.0001) regardless of whether days in milk and milk yield were used as covariates. Additional analyses indicated that the Swedish Red × Holstein had a different pattern of vaginal temperatures than the other three genotypes (Swedish Red × Holstein vs others × time; P < 0.0001) and that Holstein and Jersey had a different pattern than Jersey × Holstein [(Holstein + Jersey vs Jersey × Holstein) × time, P < 0.0001]. However, Holstein had a similar pattern to Jersey [(Holstein vs Jersey) × time, P > 0.10]. These genotype × time interactions reflect two effects. First, Swedish Red × Holstein had higher vaginal temperatures than the other genotypes in the late morning and afternoon but not after the evening milking. Secondly, Jersey × Holstein had lower vaginal temperatures than other genotypes in the late morning and afternoon and again in the late night and early morning. Results point out that there are effects of specific genotypes and evidence for heterosis on regulation of body temperature of lactating cows maintained under grazing conditions and suggest that genetic improvement for thermotolerance through breed choice or genetic selection is possible.     

Dynamics of heat shock protein 70 concentrations in peripheral blood lymphocyte lysates during pregnancy in lactating Holstein-Friesian cows

The aim of this study was to characterize the dynamics of the concentrations of heat shock protein 70 kDa (HSP70) in peripheral blood lymphocytes of lactating Holstein-Friesian dairy cows (Bos taurus) during pregnancy. The detection of pregnancy was carried out and blood samples collected on Days 40, 90, 120, 150, 180, and 210 of gestation from 46 cows (11 primiparous and 35 pluriparous, 34 seropositive and 12 seronegative to Neospora caninum). Peripheral blood lymphocytes were isolated by density gradient centrifugation. Serologic analysis of Neospora infection and determinations of HSP70 concentrations in lymphocyte lysates were carried out using commercial enzyme-linked immunosorbent assay kits. Climate variables were monitored using on-farm data loggers. Heat shock protein 70 concentrations increased in lymphocytes as gestation progressed, particularly in primiparous cows, with no effect from Neospora infection, climate variables, milk production, semen-providing bull, or outcome of gestation (singletons or twins). Our results show that HSP70 concentrations increased in lymphocytes as gestation progressed and were not affected by stressful factors, such as milk production, heat stress, chronic infection (neosporosis), or twin pregnancies.     

Modeling heat stress effects on dairy cattle milk production in a tropical environment using test-day records and random regression models

In tropical environments, dairy cattle production is constrained by several factors, including climate. The seasonal loss of milk due to heat stress is a recurring challenge for many dairy producers. The objective of this study was to detect heat stress thresholds, milk yield loss and individual animal variations using random regression models for dairy cattle from test-day milk records. Data were obtained from the Kenya Livestock Breeders Organization for the years 2000–2017 and merged with weather data. The weather parameters were grid-interpolated solar and meteorological data obtained from the National Aeronautics and Space Administration/Prediction Of Worldwide Energy Resources (NASA/POWER). After editing, the records comprised 49 993, 45 251 and 36 136 test-day records for first, second, and third lactations, respectively, for the four main dairy breeds: Friesian (68.0%), Ayrshire (21.1%), Jersey (7.6%) and Guernsey (3.3%). Variance components were estimated using Restricted Maximum Likelihood in ASReml software. Random regression models with third-order Legendre polynomials were fitted to the average and individual lactation curves and the reaction norms. An extended factor analytic variance structure for the random cow effects was used to estimate (co)variances between days in milk and thermal load. The daily average temperature (TA) and temperature humidity index (THI) were identified as the most suitable thermal load indicators for assessing milk yield losses. Considering a one day lag, the estimated heat stress thresholds were about 22 °C and 69 index units for TA and THI, respectively. Almost no differences were observed for estimated residual variances between the thermal load indicators, indicating there was no better model fit by TA or THI. The heat stress thresholds and milk loss patterns are important for management of dairy production systems in the tropics with climatic conditions similar to this study. Data recording should be improved as a tool to monitor the expected impacts of climate change and mitigation measures.     

Effect of feeding Saccharomyces Cerevisiae on performance of dairy cows during summer heat stress

Effects of feeding a culture of Saccharomyces cerevisiae to lactating cows on their lactational performance during heat stress were determined. Multiparous Holstein cows (n = 723) calving during the summer months from two dairy farms were randomly assigned to a diet containing no yeast culture (control; n = 361) or 30 g/d of a S. cerevisiae yeast culture (YC; n = 362) fed from 20 to 140 d in milk (DIM). Cows were milked twice daily and the production of milk and milk components was measured every 2 weeks. Dry matter (DM) intakes from 6 pens were measured daily and pen temperature and humidity were evaluated hourly from June to November. Rectal temperature was measured in 88 cows (22/treatment/farm), once weekly, and blood was sampled from a subset of 120 cows at 58 and 100 DIM for measurements of plasma glucose, nonesterified fatty acids, 3-OH-butyrate, insulin, and urea N concentrations. Daily temperature, humidity and the temperature-humidity index in the study pens did not differ between treatments, and rectal temperature of cows in the control and YC treatments differed with days postpartum. Intake of DM was similar between diets, but cows fed YC produced 1.2 kg/d more milk, more milk true protein, solids-not-fat and lactose than that produced by control cows. However, energy-corrected milk yield, and concentrations of true protein, solids-not-fat and lactose did not differ between treatments. Feeding YC did not influence plasma metabolites, insulin, or body condition score of cows, but urea N concentrations were reduced. Feeding a yeast culture of S. cerevisiae improved yields of milk and milk components in heat-stressed multiparous Holstein cows.     

Assessing heat tolerance through productive vs physiological indicators. Data from dairy sheep under on-farm conditions

The search for criteria that allow the quantification of the level of thermotolerance of an animal is a major challenge in animal production. Different criteria have been proposed to date, mainly the use of routine milk recording and weather information or the collection of physiological measures related with heat stress. This study aimed at quantifying the association between indicators of heat tolerance derived from productive and physiological traits. For this purpose, two physiological traits, rectal temperature (RT) and respiratory rate (RR), and nine productive traits (milk yield, fat, protein and lactose yields and contents, casein and urea contents) were measured from June to September of 2018 in three flocks of Manchega sheep. A total of 462 lactating ewes participated in the study. Air temperature (Ta), relative humidity (RH) and associated temperature and humidity index (THI) were recorded inside the barn and also obtained from the closest weather station from the national meteorological network, and used to produce several measurements of heat load on animals. Based on the results of fits for quadratic and cubic regressions on the alternative heat load measures, the cubic regression on Ta and THI obtained inside the barn at time of recording yielded the best fit for physiological and productive parameters. The use of weather information taken from the official weather station closest to the farm also produced similar estimates and could be considered as a good alternative when on-farm meteorological data are not available. Two-trait random regression models that involved individual intercept and slope of response to heat load were used to obtain correlations between basal levels and heat tolerance within and across traits. Estimated correlations showed that animals with smaller vs larger basal levels of RT and RR tend to be more vs less heat tolerant (correlations up to 0.46) and that slopes of increase for RR and RT under heat stress were highly correlated (0.82). Estimated correlations between tolerance criteria from production vs physiology were up to ?0.5 (between milk yield and RT), indicating that animals that show less increase in body temperature also tend to show a smaller decrease in production under heat stress. However, because of the non-unity correlation between the two types of indicators of heat tolerance, both sources of information, productive and physiological ought to be taken into account to ensure the long-term sustainability of selection programmes aiming at improving productive levels when heat stress is a concerning issue.     

Absence of a causal relationship between environmental and body temperature in dairy cows (Bos taurus) under moderate climatic conditions

1.

Continuous body temperature records from dairy cows for 46 days of summer and contemporary data for climate temperature humidity index (THI) were analysed.     

Hydrogenated fish fat for grazing dairy cows in summer

Thirty-two multiparous Holando argentino cows in mid lactation were randomly assigned to two treatments: control or HFF (hydrogenated fish fat) at Rafaela, 31° 11’ South, during summer 1997/1998, to evaluate the effect of using HFF as a supplement under grazing conditions. Animals in both treatments grazed an alfalfa pasture, and were confined from 1000 hours to 1700 hours daily in a shaded pen where water was provided ad libitum. During each milking, animals in the control group received 3.73 kg dry matter per cow each day (DM cow^–1 day^–1) concentrate (15% crude protein; 8.69 MJ energy for location/kg DM). Cows in the HFF group received 3.25 kg DM cow^–1 day^–1 concentrate, plus 0.200 kg DM cow^–1 day^–1 HFF. Both diets presented similar energy, protein and neutral detergent fibre contents. The trial was performed during a strong ”El Niño” event, which resulted in a total rainfall of 396.3 mm (80% higher than normal). The mean temperature was 23.7 (SD 3.2)°C and the mean temperature humidity index was 72.9 (SD 4.96). Production data were analysed using a completely randomised design with analysis of covariance. Supplementation with HFF produced an increase in daily milk production (26.4 (SD 2.46) l/cow compared to 23.9 (SD 2.68) l/cow for the controls; P<0.05). Milk fat production was higher for HFF (P<0.05): 941 (SD 96) g cow^–1 day^–1 as compared to controls, which yielded 846 (SD 95) g cow^–1 day^–1. Milk protein yields also differed significantly (P<0.05), the respective values for HFF and controls being 795 (SD 72) g cow^–1 day^–1 and 715 (SD 83) g cow^–1 day^–1. It was concluded that hydrogenated fish fat could be a good ingredient to sustain high yields and elevated maintenance requirements in a grazing system during hot conditions.     

Functionality and DNA-damage properties of blood cells in lactating cows exposed to glyphosate contaminated feed at different feed energy levels

ABSTRACT

Glyphosate (GL) inhibits the aromatic amino acid biosynthesis in plants and is worldwide the most used non-selective herbicide. Less is known about in vivo effects of GL contaminated feedstuffs on the health of dairy cows. The aim of this study was to examine the effects of GL residues in feed at different concentrate feed proportions (CFP) on haematology, immunological and redox parameters and on DNA-damage of blood cells in lactating dairy cows. During a 16-trial, 61 German Holstein cows (207 ± 49 d in milk; mean ± SD) were fed the same ration in week 0. Afterwards, they were assigned to either a group receiving a GL contaminated or a group receiving an uncontaminated total mixed ration (CON). Each group was subdivided into a “low concentrate” group (LC) and a “high concentrate” group (HC) with an energy content of 6.63 MJ NEL and 7.18 MJ NEL/kg dry matter, respectively. The diets were offered for ad libitum consumption. Blood samples were taken at weeks 0, 4, 8, 12 and 16. All blood samples were analysed for white and red blood cell counts. T-cell subpopulations, oxidative burst capability of leukocytes, apoptosis rate, phagocytic activity, activities of superoxide dismutase and glutathione peroxidase, the total non-enzymatic antioxidative capacity, viability and stimulation capacity of peripheral blood mononuclear cells and micronucleus- and comet assay on bovine leukocytes were measured only in week 16. The average individual GL intake of groups CON, GL_LC and GL_HC was 1.2 µg, 112.6 µg and 132.8 µg per kg body weight and day, respectively. GL contamination did not affect any of the tested parameters whereas CFP and time-influenced leukocytes, granulocytes, red blood cells, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin and CD4⁺ T-cells in an interactive manner characterised by a time-dependent increase in HC groups. It can be concluded that GL and GL in combination with different CFP showed no influence on any of the tested endpoints, whereas CFP and time influenced most parameters in an interactive manner.     

Impact of season on haematological and biochemical parameters of crossbred female calves in hot and humid tropics

The objective of the present study was to assess the impact of season on haematological and biochemical parameters of crossbred female calves. Seven crossbred female calves of 6–12 months of age were selected. The study was conducted in three different spells of 30 days each in pre-monsoon, monsoon and post-monsoon seasons. Ambient temperature (AT), relative humidity (RH) and temperature humidity index (THI) was recorded in all the three seasons. Whole blood was collected for estimation of haematological and plasma was used estimation of biochemical parameters. Highest AT and THI was recorded in pre-monsoon while highest RH was recorded in monsoon. The study revealed that season had no effect on haematological parameters such as total leucocyte, haemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, while total erythrocyte count was significantly lower in monsoon compared to pre and post-monsoon seasons. Glucose and cholesterol were significantly lower in pre-monsoon and monsoon compared to post-monsoon. Glutathione peroxidase activity was significantly higher in pre-monsoon compared to monsoon and post-monsoon. No significant difference between seasons in the concentration of total protein, albumin, globulin and albumin globulin ratio was noticed. The results indicate that hot conditions have profound effect on haematological and biochemical parameters of crossbred calves.     

Carry-over effect of summer thermal stress on characteristics of the preovulatory follicle of lactating cows

Low fertility of cattle during the cool autumn is mostly associated with exposure to thermal stress in the previous summer. This study examined carry-over effects of summer heat stress and induction of enhanced follicular turnover, on the characteristics of preovulatory follicles during autumn. Holstein cows were treated with PGF₂ and GnRH to induce six successive 9-day follicular waves during autumn. Intact cows served as controls. Follicular fluid concentrations of androstenedione were higher in treated cows, but those of IGF-I and progesterone did not differ between groups. The concentration of estradiol at the end of the treatment was higher, and the content per follicle increased with time and was numerically higher in treated cows. The volume of follicular fluid increased during the autumn and was greater in treated cows. A delayed effect of heat stress on preovulatory follicles was noted, and induction of follicular waves by GnRH was able to improve follicular characteristics in autumn.     

Access to shade changes behavioral and physiological attributes of dairy cows during the hot season in the subtropics

The effect of shade on behavior and physiological attributes of grazing cows in a high altitude subtropical zone is not well established. This work aimed to investigate how social and ingestive behaviors, as well as physiological and other attributes of dairy cows such as milk production, change in a subtropical environment during the hot season either with or without free access to shade. Fourteen lactating cows were kept on pasture either with no shade or with free access to shade for 5 days and their behavior was recorded with instantaneous scan sampled every 10 min, from sunrise, 0530 h (Greenwich mean time, GMT−0200 h) to sunset, 2100 h (GMT−0200 h). Behavior traits included (1) time spent in activities such as grazing, ruminating, resting, lying, standing, walking, seeking shade and staying in the proximity to the water trough and (2) number of events such as water ingestion, aggressive interactions, as well as competition for shade and water. Physiological attributes such as heart and respiratory rates, rectal temperature, number of rumen movements, panting score, as well as milk yield, were evaluated. Time spent in behavioral activities, number of behavioral events and physiological attributes varied between groups (with and without access to shade). Cows with no shade showed increased respiratory and heart rates and panting score at 1300 h, higher values for time of permanence near the water trough, number of competition and aggression events for shade. On the other hand, they showed lower values for time spent resting while lying, ruminating while standing, seeking shade. Access to shade did not change time spent lying, standing, walking with the head up, ruminating while lying, resting while standing, as well as milk yield and number of ruminal movements. Significant interactions between access to shade and days of measurements were detected for time spent walking, ruminating, grazing, resting, number of water ingestion events, competition events near the water trough and for shade, as well as for rectal temperature and panting score measured at 1700 h. In the high altitude subtropical region, access to shade minimizes negative heat stress effects on behavior and physiological aspects of dairy cows.     

Evaluation of the genetic trend of milk yield in the multiple ovulation and embryo transfer populations of dairy cows, using stochastic simulation

Stochastic modeling of dairy cattle populations using multiple ovulation and embryo transfer (MOET) was used to compare 15-year genetic responses with an artificial insemination (AI) program. MOET and AI techniques were simulated in four populations, two with 100 breeding females each and two with 400 breeding females. The selection goal was to maximize genetic progress in milk yield. The reduction in genetic variation due to inbreeding and linkage disequilibrium was accounted for in the simulation process. All four MOET breeding schemes studied achieved larger genetic responses than the realized and theoretical genetic gains from the current AI progeny testing populations. Strict restriction against inbred matings slowed genetic progress significantly in the small population but would not be consequential in the larger population. However, allowing inbred matings in the smaller population caused a rapid accumulation of inbreeding. Linkage disequilibrium was as important as inbreeding in reducing genetic variation. Genetic drift variance was much smaller in the larger population.     

Diurnal behaviors and herd characteristics of dairy cows housed in a compost-bedded pack barn system under hot and humid conditions

With international demand for production systems aimed at thermal comfort and animal welfare, milk producers have become increasingly interested in compost barns. However, doubts about the behavioral aspects of cows in tropical and subtropical climates remain, because the compost barn system offers a larger bed area per animal at a lower stocking rate. The objective of this study was to evaluate whether the diurnal behaviors, hygiene and lameness of crossbred dairy cows are influenced by different number of lactations when housed in a compost-bedded pack barn system under hot and humid conditions. Crossbred cows (Holstein and Jersey), which were divided into two treatments based on number of lactations (primiparous and multiparous cows), were evaluated during lactation (n=12). The study was conducted from September 2015 to February 2016 in a compost barn in the southwest region of the state of Paraná, Brazil. Daytime behavior was observed between milking schedules using focal observations with 0/1 sampling. Cow hygiene and lameness were evaluated using subjective scores ranging from 1 to 4 and 1 to 5, respectively. Animal behavior and welfare was analyzed using Bayesian inference with a mixed effects model. The probabilities of dyspnea and pushing behaviors were higher (P<0.05) in multiparous cows, and the probability increased during the hottest hours of the day. For both multiparous and primiparous cows, the agonistic behaviors of pushing, butting and chasing peaked during the afternoon. Eating behaviors had the highest likelihood values (0.8 at 0800 h). The cows preferred to remain lying down in the morning, while rest and standing rumination were preferred in the afternoon. Primiparous cows were cleaner than multiparous cows, and the hygiene score for this group was significantly lower (P<0.05). The hygiene and lameness scores for all animals were low, and the highest scores were 1 and 2. In conclusion, multiparous cows exhibited more frequent agonistic behaviors during the hottest hours of the day. Regarding hygiene and lameness scores, multiparous cows exhibited a higher degree of dirtiness compared with the primiparous cows.     

Microclimate modeling in naturally ventilated dairy barns during the hot season: Checking the accuracy of forecasts

Monitoring and predicting the microclimate in naturally ventilated barns (NVB) is important given the adverse effects of high summer temperatures on dairy cows in the context of global climate change. The aim of the work was to verify the accuracy of the microclimate forecast in a NVB using linear regression (LR). Our working hypothesis suggested that multiple periodic measurements of air temperature and relative humidity outside and inside the barns at the same time will allow us to build LR models for predicting the temperature-humidity index (THI). This was done not only for a specific dairy barn based on this indicator outside, but also in other dairy barns with a similar design, located in similar weather conditions. The results of the research indicate that the use of LR had a high accuracy of forecasting (93–96%) the THI in NVB of various designs during the summer heat. At the same time, differences were found between traits (air temperature, relative humidity as well as resulting THI) provided by meteorological weather stations and these data measured simultaneously next to the dairy barns. The proposed LR models can be used to predict THI in NVBs of different designs.