Average Temperature-humidity Index Research Articles

Investigating the relationship between heat load and shade seeking behaviour in dairy buffaloes.

The study presented in this Research Communication aimed to investigate the relationship between physiological responses, body surface temperature and shade-seeking behaviour in Nili Ravi dairy buffaloes during summer months. We enrolled 60 buffaloes, and each animal was observed for three consecutive days starting before sunrise until they moved towards the shade structures. A repeated measures ANOVA was employed to assess the changes in physiological parameters and body surface temperature between the early morning and the occurrence of shade-seeking behaviour. The average temperature humidity index and heat load index during the behavioural monitoring period (0400 to 1200 h) were 81.3 ± 6.5 and 92.9 ± 17, respectively (mean ± sd). There was no significant difference in core body temperature between sunrise and the time of shade-seeking event. However, the buffaloes had a slightly higher respiration rate at the time of shade-seeking (19.2 vs. 22.4 breaths/min). In addition, body surface temperature, measured at the flank region, shoulder, base of the ear and forehead was significantly higher at the occurrence of shade-seeking behaviour compared to the early morning. On average, the buffaloes sought shade when the surface temperature was 2°C higher than the temperature recorded before sunrise. Overall, the current findings suggest that body surface temperature, rather than core body temperature was strongly associated with shade-seeking behaviour in dairy buffaloes. These findings could be useful in developing strategies to mitigate the effects of heat stress in dairy buffalo herds and thereby improve animal welfare.

228 The effect of temperature-humidity index in different pregnancy stages on litter traits in Taiwan Landrace sows

Abstract Because of climate change, annual average temperatures are gradually rising. Hence, increasing heat stress can impair the litter traits of Taiwanese sows located in tropical and subtropical zones. However, some pregnancy stages may be impacted more by heat stress than other periods. Thus, the purpose of this study was to demonstrate the effect of temperature-humidity index (THI) in different pregnancy stages on total number born (TNB), number born alive (NBA), and stillborn rate (STB). Data were collected in two Taiwanese farms from 2008 to 2021 for TNB, NBA, and STB, while weather data were collected from the closest respective weather station. There were 4,247 and 6,812 pure line Landrace record from farm 1 and farm 2, respectively. Pregnancy stages included 28 d before mating (BEFORE), mating to 30 d of pregnancy (EARLY), 31 to 70 d of pregnancy (MIDDLE), and 71 d of pregnancy to farrowing (LATE). Average THI was calculated in each pregnancy stage and regression coefficients were estimated by linear mixed models within ASReml. A two-trait analysis was used to estimate regression coefficients and genetic correlations among TNB, NBA, and STB. Results showed THI impacted (P < 0.05) TNB and NBA BEFORE and EARLY, while THI influenced (P < 0.05) STB EARLY and MIDDLE. Regression coefficients for TNB were -0.0069 and -0.0228 for BEFORE and EARLY, respectively. For NBA, regression coefficients were 0.0106 and -0.0391 for BEFORE and EARLY, respectively. Regression coefficients for STB were -0.0651 and 0.1332 for EARLY and MIDDLE, respectively. Heritability estimates for TNB, NBA, and STB were 0.168, 0.113, and 0.069, respectively. Genetic correlations between TNB with NBA and STB were 0.913 and 0.539, respectively. While the genetic correlation between NBA and STB was 0.158. In conclusion, THI impacted BEFORE and EARLY stages for TNB and NBA, while the stages of EARLY and MIDDLE were impacted by THI for STB. Hence, control of the environments in these specific stages for sows could improve the performance of litter traits.

Performance, blood and antioxidant status in dual-purpose laying hens supplemented with aqueous extract of Christ's thorn jujube (Ziziphus spina-christi L.) leaves as phytogenic agent in subtropical conditions.

The potential of aqueous extract of Christ's thorn jujube (Ziziphus spina-christi) leaves (SLAE) to reduce the negative impacts of heat stress on production performance and physiological traits was investigated in dual-purpose layers under subtropical farming. A total of 200, 25-week-old laying hens (Inshas strain) were randomly assigned to four dietary treatments including SLAE at 0, 2.5, 5.0, and 7.5 mL/kg, respectively. The average temperature-humidity index value was 26.69 during the experimental period. The SLAE contained saponin (0.045%), total flavonoid content of 17.9 mg of quercetin equivalent/ 100 g and overall antioxidant capacity concentration of 17.9 mg of ascorbic acid equivalent/100 g. The maximum final body weight (BW), BW gain, egg weight, number, and mass occurred at the level of SLAE7.5 inclusion. The egg quality was significantly higher in SLAE groups than in control, and overall, SLAE7.5 had the most favorable influence at 28 and 32 weeks. Liver and kidney function, as well as lipids profile, improved significantly by SLAE inclusion; the lowest concentrations of these parameters were in SLAE7.5 hens. Treatment with SLAE7.5 increased total antioxidant capacity and endogenous antioxidant enzymes compared to control, whereas no effect on superoxide dismutase was noticed. The addition of SLAE at 7.5 mL/kg diet improved egg laying performance and quality, metabolic profiles, and antioxidant status during hyperthermia conditions.

Dietary effects of protected fat, glycerol, and soybean meal on performance, physiological parameters, carcass characteristics, and behavioral measurements of late-fattening Hanwoo steers under heat stress conditions.

This study aimed to determine the effects of increasing energy and protein levels in diets by including protected fat (PF), glycerol (GL), and soybean meal (SBM) on growth performance, physiological parameters, carcass characteristics, and behavioral measurements of late-fattening Hanwoo steers under heat stress conditions. Thirty-six steers (initial BW, 724.9 ± 58.3 kg; age, 25.5 ± 0.4 month) were assigned into Control (TDN 76%, CP 15%), PF (TDN 83.6%, CP 15%), PF+GL (TDN 83.6%, CP 15%) and PF+GL+SBM (TDN 83.6%, CP 16.5%) by randomized complete block design for a total of 16 weeks with division of 4 week periods. The average temperature-humidity index was 87.0 (1st period; Severe), 82.8 (2nd; Moderate), 71.4 (3rd; Comfort), and 68.1 (4th; Comfort). The DMI showed no treatments differences during the whole experiment. However, DMI in 1st and 2nd period decreased by approximately 30% and 10% compared to 4th period, respectively. Higher ADG and FCR were noted for treatments compared to Control at both 1st and 2nd period (p<0.05). There were no treatment effects on rectal temperature (RT), cortisol, and behaviors during the entire experiment. However, both RT and cortisol in 0, 1st and 2nd period were higher than those of 3rd and 4th period (p<0.05). Carcass yield and grade remained unaffected by increasing TDN and CP levels. Behavioral changes in the hot season (1st period) included reduced lying (43%), increased standing (48%), decreased walking (62%), and decreased eating (38%) (p<0.05), with an increase in drinking by 54%. Rumination during standing was 53% higher, while rumination during lying was about 33% lower compared to the post-hot season (3rd period) (p<0.05). Dietary supplementation of protected fat in late-fattening Hanwoo steers under heat stress had a positive effect on preventing a reduction in performance.

Evaluating the dose-dependent effects of curcumin nano-micelles on rumen fermentation, nitrogen metabolism, and nutrient digestibility in heat-stressed fattening lambs: Implications for climate change and sustainable animal production.

Global warming threatens livestock production, especially in hot climates. This study evaluated the dose-dependent impacts of dietary curcumin nano-micelles (CNM) on rumen fermentation, nitrogen metabolism, and nutrient digestibility in heat-stressed fattening lambs. Thirty-two crossbred male lambs [ˆIle-de-France × (Dalagh × Romanov)] were utilized within the current study. The initial weight of lambs was documented as averaged by 31.2 ± 1.55 kg, while they were in their 4th to 5th months of age. Animals were fed increasing doses of dietary CNM (0, 20, 40, and 80 mg/day) over 97 days, under severe heat stress conditions with average temperature-humidity index (THI) of 24.5. Quadratic improvements (p < 0.01) occurred in weight gain, average daily gain (ADG), and feed conversion ratio (FCR) by 28.7%, 27.4%, and 23.9%, respectively, in the T40 group compared to the control. Additionally, T40 increased fiber digestion by 2.8% (p < 0.05). Furthermore, T40 quadratically improved parameters of rumen fermentation, including concentrations of NH3-N (p < 0.05), total volatile fatty acids (TVFA; p < 0.01), acetate (p < 0.05), and iso-valerate (p < 0.05), by 13.9%, 12.5%, 15.0%, and 43.5%, respectively, compared to the control. Quadratic increases were also observed in nitrogen balance (p < 0.05) and microbial protein synthesis (p < 0.01) by 19.8% and 37.6%, respectively, in the T40 group. Quadratic models estimated optimal CNM levels between 41.5 and 48.6 mg/day for multiple parameters. These findings indicate CNM at dose level of 40 mg/day could benefit heat-stressed lambs through enhanced rumen function and microbiota. Further research should refine ideal dosing for various species and production phases as higher levels adversely impacted fiber digestibility. Overall, CNM shows promise as a sustainable nutritional intervention for livestock production facing global warming.

Relationship among thermal environment, stage of lactation, body characteristics, yield and milk constituents of dairy Gyr cows managed on pasture.

Our aims were to evaluate changes in body characteristics, milk yield and milk constituents as well as to determine the relationship between the thermal environment and production characteristics during the first lactation of dairy Gyr cows managed on pasture. Between 2013 and 2015, forty-five primiparous dairy Gyr cows were evaluated from prepartum to 10 months of lactation in Southeast of Brazil. Body weight, body condition score (BCS), subcutaneous fat thickness (SFT), milk yield (305 d), and milk constituents were collected monthly and progesterone was collected weekly. Additionally, we determined the temperature humidity index (THI) based on microclimate data. Overall, the cows lost body weight until six months of lactation and there was a progressive decrease in BCS, SFT, milk yield and milk lactose as the months in lactation progressed. In contrast, there was an increase in milk fat, milk protein and milk solids. The thermal environment did not pose a consistent heat challenge, nevertheless, we found a positive correlation between the average THI two days before milk collection with milk yield, fat and lactose contents, but in contrast a negative correlation was found with total solids and protein. In conclusion, the THI and months of lactation affected the yield and constituents of milk. However, more studies are necessary to understand the impacts of body characteristics and thermal environment on yield and milk constituents throughout the productive life of Gyr dairy cows.

Applicability evaluation of a temperature humidity index-controlled ventilation system in livestock using a building energy simulation model

In general, for livestock building, a simple system for controlling the HVAC system that is based only on the indoor air temperature is applied. This study evaluated the applicability of temperature humidity index (THI)-based ventilation systems installed in livestock buildings using a building energy simulation model. Based on the monitoring data of an actual pig house, the integrated predictive performance of the indoor temperature and humidity of the building energy simulation model was calibrated. Additionally, the indoor environment of the existing temperature-based control and THI-controlled ventilation systems was compared through simulations. The average THI and the section exceeding the THI threshold were both lower compared to the existing system. This was because the part load ratio of the fans of the THI-controlled ventilation system was higher than that of the existing system, indicating better ventilation. These results suggest that THI-based ventilation systems can overcome the limitations of existing temperature-based systems and effectively improve the thermal stress management of livestock buildings. This study portrays that the indoor environment can be improved by simply changing control variables, while presenting the field applicability and research value of THI-based control systems in the management of livestock environments.

External Progesterone Supplementation During the Ovsynch Protocol Reduces the Incomplete Luteolysis in Dairy Cows Under Heat Stress

Abstract The present study aimed to determinate the effect of external progesterone (P4) supplementation on luteolysis in cows under heat stress. Forty-eight (n=48) dairy cows in the period from July–September 2018 were part of and at day 35±3 postpartum scored for BSC, synchronized using PG-3-G + Ovsynch protocol and randomly allocated into two treatments: PRID group (n=27) treated with external P4 device between G1 and PGF2α and CON group (n=21) left without treatment. Collection of blood samples to assess P4 concentrations was done at Pre-PG, at G1, at PGF2α, at 72 h after PGF2α (at timed artificial insemination TAI) and at d 21 after TAI. The pregnancy diagnosis was done at d 21 and d 30 after TAI by ultrasound. The average temperature-humidity index (THI) was 79.5±0.6. At G1, the P4 was significantly lower in the PRID group (1.84±0.99 ng/mL) in comparison to the CON group (2.97±1.82 ng/mL). In contrast, at PGF2α, there was a tendency (p=0.09) of increased P4 concentration in PRID group compared with the CON group (4.26±1.68 and 3.74±2.39 ng/mL), respectively. At TAI, more PRID cows (p=0.0001) had a lower P4 (0.06±0.03 ng/mL), in comparison to CON (1.28±2.41 ng/mL). At d 21 and d 30 after TAI, more PRID cows were predicted and diagnosed pregnant (16/27 or 59.25% and 13/27 or 48.14%) compared with the CON group (11/21 or 52.38% and 8/21 or 38.08%) respectively, but without any significant differences. Supplementation of the P4 during the Ovsynch protocol increases the P4 before TAI and reduces the incomplete luteolysis in heat stressed dairy cows.

Physiological response of Katahdin ewes to the absence of shadows in tropical region of Mexico

This study evaluated the effect of environmental conditions on the physiological and body infrared temperature traits of Katahdin sheep. Ten recently reproductive-managed ewes were randomly segregated into two groups. The control group (CG) was under outdoor conditions with shadow access, and the experimental group (EG) was under outdoor conditions without shadow access. Traits were measured for 16 days, and the environmental traits confirmed significant differences between groups, with an average temperature-humidity index (THI) of 68.64±1.46 for the CG and 72.98±3.17 for the EG, with a breach of five units between groups. The THI was subsequently used to evaluate the heat load. Respiratory frequency was the physiological variable that responded the most to heat stress. The rectal temperature of the sheep was greater in the experimental group than in the control group, indicating an increase in heat stress. The EG also presented higher heat emissions from body regions, which was associated with changes in core body temperature and blood flow at the body surface. Differences in hematological parameters, such as the erythrocyte count, mean corpuscular volume, and total plasma protein concentration, were found between the groups. Infrared thermography was found to be efficient for estimating heat stress in sheep species, and head temperature was found to be a reliable indicator of physiological thermal stress.

Evaluation of Colostrum Quality and Passive Transfer Immunity in Terms of Heat Stress and Disease Incidence in Central Anatolia

The effects of heat stress on colostrum quality, passive transfer failure and disease incidence experienced by cows and calves raised in the Central Anatolian region, where temperature differences are very high, were investigated in a large population in order to prevent calf deaths and yield losses. Cow's daily temperature humidity index, 7-day average temperature humidity index, average temperature and humidity index (p

Equine chorionic gonadotropin treatment and timed artificial insemination for dairy cow production under heat stress.

This study investigated the effects of timed artificial insemination (TAI) and equine chorionic gonadotropin (eCG) administration on lactating dairy cows under heat-stress conditions (average temperature-humidity index: 80). Timed artificial insemination was performed on the cows with (n = 57) or without (control, n = 41) supplementation with 500 IU of eCG at the day of PGF2α treatment using the CIDR-Ovsynch protocol. GnRH was administered, and a progesterone device (CIDR) was inserted on Day -10 of the treatment protocol. The CIDR was removed on Day -3, and the cows were treated with PGF2α. Two days later, a 2nd GnRH injection was administered. Subsequently, AI was performed on Day 0 (16-20 h after the 2nd GnRH injection), and pregnancy was diagnosed on Days 32 and 60. Plasma progesterone (P4) concentrations were measured after AI. Results showed that the eCG group had a higher pregnancy per AI (P/AI) than the control group (43.9 vs. 12.2%, P = 0.002), which was also accompanied by elevated P4 levels. Four cows in the eCG group had multiple calves, representing 7.0 and 16.0% of the group and pregnant cows, respectively. In conclusion, 500 IU of eCG combined with CIDR-Ovsynch in lactating dairy cows under severe heat stress conditions successfully improved fertility. However, the protocol may have a slight risk of multiple births.

STUDY OF THE ROLE OF GREEN OPEN SPACE IN DKI JAKARTA AS AN AMENITY INFRASTRUCTURE

Green open spaces are often incompatible with the functions they should have. In the last few years, DKI Jakarta has continued RTH construction, but the implementation has been neglected, resulting in non-compliance with RTH requirements. Green open spaces in Kota Hijau are frequently located in the outskirts of DKI Jakarta, yet, in reality, the area allocated to green open space has not met the mandated 30% minimum requirement. The creation of well-designed green open spaces is crucial to providing essential amenities for the community. This study aims to analyze thermal comfort levels, community activities, and security in three parks in DKI Jakarta. The average Temperature-Humidity Index (THI) value of 24.5 suggests favorable conditions below the threshold of 27. Although the current state is considered satisfactory, continuous monitoring and efforts are recommended to maintain optimal THI conditions. Additionally, an evaluation of visitor comfort in the Green Open Spaces (RTH) of DKI Jakarta, based on a questionnaire, revealed a reasonably comfortable score of 3.6 out of 5. Consequently, there is a need to improve facility quality to enhance visitor comfort. The security questionnaire results from three parks in DKI Jakarta indicate a sufficiently safe environment, with an overall score of 3.6 out of 5. However, it is advisable to augment security facilities and personnel to further enhance the sense of safety for park visitors. In conclusion, this research underscores the importance of optimizing and expanding green open spaces in DKI Jakarta, not only for thermal comfort but also for the overall well-being, security, and recreational needs of its urban residents.

A new proposal for the use of the focal animal technique in buffaloes in the Eastern Amazon.

This study aims to present a proposal for using the focal animal recording technique to evaluate the welfare of buffaloes and to verify the association between each behavior and thermal comfort indices. The study was conducted in an experimental paddock located in Santarém, Pará, Brazil. A total of 10 female Murrah animals were used. The behavior of the animals was recorded during the day, with the use of three trained observers, for 72 consecutive h. Climatic variables were collected, and the Temperature-Humidity Index (THI) and the practical Buffalo Comfort Climatic Conditions Index (BCCCIp) were determined. The multivariate technique of principal components and Spearman's correlation were employed. BCCCIp and THI were outside the thermal comfort zone at different times of the day. Grazing (P) was more frequent in the coldest hours of the day, while rumination occurred at different periods, mainly during the daytime and frequently in a lying position. There was a positive correlation between idle lying behavior and average temperature-Tmed (r = 0.583; p < 0.028), THI (r = 0.432; p < 0.034), and BCCCIp (r = 0.554; p < 0.049). There was a positive correlation between grazing and Tmed (r = 0.665; p < 0.0004) and BCCCIp (r = 0.583; p < 0.036). The standing idle behavior negatively correlated with Tmed (r = -0.718; p < 0.0001), THI (r = -0.522; p < 0.008), and BCCCIp (r = -0.8076; p < 0.0008). The lying ruminating behavior had a positive correlation with Tmed (r = 0.586; p < 0.002), THI (r = 0.477; p < 0.018), and BCCCIp (r = 0.8033; p < 0.0009). Furthermore, ruminating while standing correlated positively with Tmed (r = 0.680; p < 0.0003). The adaptation of the focal animal technique, with six observers evaluating each animal for 6 min through filming, proved to be efficient in pointing out the different behaviors of buffalo raised in Eastern Amazon fields under heat stress at different times of the day.

Evaluating the impact of sprinkler cycle and flow rate on dairy buffalo performance during heat stress.

The aim of this study was to evaluate the effect of the sprinkler cycle and flow rate on physiological, behavioural, and productive responses in dairy buffaloes. Nine Nili Ravi lactating buffaloes were subjected to three sprinkler cycles and two flow rates using a double replicated 3 × 3 Latin square design. The flow rates were 1.25 and 2 l/min, and the sprinkler cycles (minutes water on/off, number of cycles/h) were: 3/3, 10 cycles; 3/6, 7 cycles and 3/9, 5 cycles. The showering was applied from 0800 till 1630 h daily. In the first square of 21 d, each of the three sprinkler cycles was applied using a 1.25 l/min flow rate for 7 d per cycle. In the later square, the same treatments (sprinkler cycles) were applied using the 2 l/min flow rate. The average temperature humidity index during the study period was 85.7 ± 3.8 (Mean ± sd). The result showed that the 3/3 treatment group had lower body temperature and respiration rate than the other groups. The buffaloes in the 3/3 group produced 0.5 and 0.7 kg more milk with 1.4 and 2.4% more fat than the 3/6 and the 3/9 treatment groups, respectively. Similarly, the 2 l/min flow rate had a lower core body temperate and respiration rate and higher milk yield than the 1.25 l/min group. The 3/3 showering cycle with a 2 l/min flow rate appeared effective in improving physiological responses and milk yield in dairy buffaloes.

Effect of Adding Choline Chloride to the Diet in Milk Production of Holstein Cows

This study aimed to show the effect of adding choline chloride to the feed on milk production during the summer in central Iraq. This study was conducted at Al-Khalis cows station in Diyala Governorate during the period from 21/6 to 21/9/2022, where 25 Holstein cows between the ages of 3-5 years used, the cows were divided into five treatments, so that treatment T1 represents the control treatment (without adding Choline chloride), while treatments T2 and T3 add untreated and formaldehyde-treated choline chloride, respectively, to the concentrated feed with an amount of 35 g /cow /day, T4 and T5 add untreated and formaldehyde-treated Choline chloride, respectively, with an amount of 70 g /cow /day, It is noted from the results that there is a significant effect of the treatment of adding Choline chloride treated with formaldehyde T3 during the ninth and thirteenth weeks in the daily milk. In the ninth week, the average milk production was 14.50 kg / cow/day compared to 9.88 kg/cow/day in the control treatment, and the rest of the treatments were T4 and T5 were 11.25 and 10.00 kg/cow/ day respectively. In the thirteenth week milk yield was 12.50 kg/cow/day compared to 7.20 kg/cow/day in the comparison treatment, and the rest of the treatments T2, T4, and T5 were 8.75, 8.50, and 8.60 kg/cow/day, respectively. While the monthly and total milk production and the amount of fat and protein in milk for cows, there were no significant differences between the treatments, we conclude from the current experiment that adding Choline chloride treated with formaldehyde in an amount of 35 g / cow/day to the feed increases the daily milk production in some weeks for this experiment in the season Summer when the average Temperature Humidity Index for this season is 79 and cows are under heat stress.

Effects of chromium propionate supplementation on lactation performance, nutrient digestibility, rumen fermentation patterns, and antioxidant status in Holstein cows under heat stress

Chromium propionate (CrP) supplementation has the potential effects on mitigating metabolic stress on dairy cows, however, the effect of increased CrP supply on alleviating heat stress of mid-lactation cows is rarely evaluated. This study was conducted to evaluate the effect of CrP supplementation on lactation performance, nutrient digestibility, rumen fermentation patterns, and antioxidant status in dairy cows under heat stress. Sixty-four Holstein dairy cows in mid-lactation with similar parity (2.1 ± 0.2), current milk production (40 ± 1.4 kg/d), and days in milk (143 ± 7.8 d) were randomly allocated to one of four treatments with a completely randomized design. After a 7-day adaptation period, cows were fed CrP at doses of 0, 4, 8, and 12 mg/d of Cr per head for 49 d. The average temperature humidity index (THI) was 77 during the experimental period. The average respiration rate and rectal temperature decreased quadratically (P < 0.01) with increasing CrP supplementation. Dry matter intake (DMI), milk yield, and milk lactose yield increased quadratically (P < 0.05) with increasing CrP supplementation, whereas 4% fat-corrected milk was not affected by treatments, and feed efficiency tended to decrease quadratically (P = 0.07). The percentage of milk protein and lactose increased linearly (P = 0.05) with increasing CrP supplementation, whereas milk urea-N concentration and somatic cell count decreased quadratically (P < 0.01). Although total-tract apparent digestibility of dry matter, organic matter, crude protein, and ether extract was not affected by CrP supplementation, neutral detergent fiber digestibility increased quadratically (P = 0.01) with increasing CrP supplementation. The concentrations of milk Cr and urinary Cr were not affected by CrP supplementation. Ruminal pH, the concentration of total VFA and ammonia-N, and the molar proportion of propionate and butyrate were not affected by treatments, whereas the molar proportion of acetate increased quadratically (P < 0.01) with increasing CrP supplementation. The blood urea-N concentration decreased quadratically (P < 0.01) and the concentration of glutathione peroxidase and superoxide dismutase increased quadratically (P < 0.01) with increasing CrP supplementation, while the ratio of glucose to insulin and the concentration of glucose and malonaldehyde did not differ among treatments. In conclusion, CrP supplementation could increase milk yield in mid-lactation cows under heat stress by increasing DMI, reducing respiration rate and rectal temperature, and improving antioxidant status. The recommended dose of CrP is 4–8 mg/d of Cr per cow in hot weather.

Seasonal effects on multiparous dairy cow behavior in early lactation

Controlled studies have shown that heat stress abatement positively influences health, productivity, behavior, and reproductive performance of dairy cows during all stages of the lactation cycle. Based on previous findings, the present study focused on a better understanding of how seasonal changes affect the behavior of multiparous lactating dairy cows kept in typical free-stall housing with the objective to aid in the management of lactating cows exposed to variable environmental conditions. Automated monitoring devices (Nedap, the Netherlands) were used to assess behavioral activity of mature Holstein dairy cows during the “hot season” (HS; n = 19; July, August, and September) and the “cool season” (CS; n = 15; December, January, and February) under normal management conditions. Cows received a leg tag to measure daily lying time, and number of steps and standing bouts, and a neck tag to measure eating and rumination time. All cows were housed in sand-bedded freestall barns equipped with cooling systems (soakers and fans). Behavior, milk production and milk components were recorded for the first 9 wk of lactation after calving. Average temperature-humidity index (THI) was 78.2 ± 0.4 (± standard error) in the HS and 54.4 ± 0.2 in the CS. Fat-corrected milk yield was greater in the CS compared with HS during the first 5 wk of lactation. Milk protein percentage was lower in CS during the first 2 wk of lactation. In contrast with HS, milk fat percentage was greater in the CS. Compared with CS, overall, during HS cows spent less time eating, lying down, and tended to spend less time ruminating. In addition, exposure to high THI resulted in increases in standing bouts, and overall standing time in HS relative to CS. No differences in number of steps were observed between HS and CS. In summary, exposure to high THI during lactation seems to negatively affect the behavior and consequently the daily time budget of lactating Holstein cows, even under housing conditions with active cooling. A better understanding on how different seasons affect the daily time budget of lactating dairy cows may contribute to the development of more effective management strategies to decrease the negative effects of heat exposure.

Effect of Slow-Release Urea Partial Replacement of Soybean Meal on Lactation Performance, Heat Shock Signal Molecules, and Rumen Fermentation in Heat-Stressed Mid-Lactation Dairy Cows.

This study aimed to assess the effects of partially substituting soybean meal in the diet with slow-release urea (SRU) on the lactation performance, heat shock signal molecules, and environmental sustainability of heat-stressed lactating cows in the middle stage of lactation. In this study, 30 healthy Holstein lactating dairy cattle with a similar milk yield of 22.8 ± 3.3 kg, days in milk of 191.14 ± 27.24 days, and 2.2 ± 1.5 parity were selected and randomly allocated into two groups. The constituents of the two treatments were (1) basic diet plus 500 g soybean meal (SM) for the SM group and (2) basic diet plus 100 g slow-release urea and 400 g corn silage for the SRU group. The average temperature humidity index (THI) during the experiment was 84.47, with an average THI of >78 from day 1 to day 28, indicating the cow experienced moderate heat stress conditions. Compared with the SM group, the SRU group showed decreasing body temperature and respiratory rate trends at 20:00 (p < 0.1). The substitution of SM with SRU resulted in an increasing trend in milk yield, with a significant increase of 7.36% compared to the SM group (p < 0.1). Compared to the SM group, AST, ALT, and γ-GT content levels were significantly increased (p < 0.05). Notably, the levels of HSP-70 and HSP-90α were significantly reduced (p < 0.05). The SRU group showed significantly increased acetate and isovalerate concentrations compared with the SM group (p < 0.05). The prediction results indicate that the SRU group exhibits a significant decrease in methane (CH4) emissions when producing 1 L of milk compared to the SM group (p < 0.05). In summary, dietary supplementation with SRU tended to increase the milk yield and rumen fermentation and reduce plasma heat shock molecules in mid-lactation, heat-stressed dairy cows. In the hot summer, using SRU instead of some soybean meal in the diet alleviates the heat stress of dairy cows and reduces the production of CH4.

Single-step genomic predictions for heat tolerance of production yields in US Holsteins and Jerseys

The physiological stress caused by excessive heat affects dairy cattle health and production. This study sought to investigate the impact of heat stress on test-day yields in United States (US) Holstein and Jersey cows and develop single-step genomic predictions to identify heat tolerant animals. Data included 12.8 and 2.1 million test-day records for 923,026 Holstein and 153,710 Jersey cows in 27 US states. From 2015 through 2021, test-day records from the first 5 lactations included milk, fat, and protein yields (kg). Cows' records were included if they had at least 5 test-day records per lactation. Heat stress was quantified by analyzing the impact of a 5-d hourly average temperature-humidity index (THI5d¯) on observed test-day yields. Using a multiple trait repeatability model, a heat threshold (THI threshold) was determined for each breed based on the point that the average adjusted yields started to decrease, which was 69 for Holsteins and 72 for Jerseys. An additive genetic component of general production and heat tolerance production were estimated using a multiple trait reaction norm model and single-step genomic BLUP methodology. Random effects were regressed on a function of THI5d¯ and THI threshold. The proportion of test-day records that occurred on or above the respective heat thresholds was 15% for Holstein and 10% for Jersey. Heritability of milk, fat, and protein yields under heat stress for Holsteins increased, with a small standard error, indicating that the additive genetic component for heat tolerance of these traits was observed. This was not as evident in Jersey traits. For Jersey, the permanent environment explained the same or more of the variation in fat and protein yield under heat stress indicating that non-genetic factors may determine heat tolerance for these Jersey traits. Correlations between the general genetic merit of production (in the absence of heat stress) and heat tolerance genetic merit of production traits were moderate in strength and negative. This indicated that selecting for general genetic merit without consideration of heat tolerance genetic merit of production may result in less favorable performance in hot and humid climates. A general GEBV for genetic merit and a heat tolerance GEBV were calculated for each animal. This study contributes to the investigation of the impact of heat stress on US dairy cattle production yields and offers a basis for the implementation of genomic selection. The results indicate that genomic selection for heat tolerance of production yields is possible for US Holsteins and Jerseys, but a study to validate the genomic predictions should be explored.

Behavioral and physiological responses to an inspired-air supplemental cooling system for dairy cows in free-stall housing.

During heat stress, dairy cows spend less time lying down to dissipate heat. Heat stress abatement strategies generally target cows outside of their resting areas. However, cooling cows while in their stalls could help alleviate heat stress without compromising lying behavior. The objective of this study was to assess the effects of an inspired-air supplemental cooling system (SCS) on respiration rate, rectal temperatures, lying behavior, rumination time, and milk production (energy-corrected milk, ECM) of lactating dairy cows. A free-stall pen was retrofitted with custom stall partitions to deliver cooled air and mist. The pen, including the stall platform, was divided into two separate sides. Twenty-eight lactating Holstein cows were randomly sorted into two groups, each housed on one side of the experimental pen. Cows experienced four treatments (control, CTRL; cooled air, AIR; mist, MIST; cooled air and mist, AIR+MIST) in a four-treatment, four-period, two-sequence crossover design, with each period lasting seven days. Cooled air was provided continuously, and mist was cycled 3min on, 12min off from 0900 to 2100h. Respiration rates were observed hourly between 0900 and 1500h, and only measurements recorded while cows were lying down were used in the analysis. Rectal temperatures of 16 focal cows were recorded at 1545h once per day. Lying behavior and rumination were recorded continuously, and milk yields recorded twice daily were used to calculate ECM. Throughout the experimental period, the average temperature-humidity index was 66.4±6.07. During the MIST treatment, the respiration rate was lower than the CTRL (45.7 vs 49.0±1.92 breaths/min) and AIR (45.7 vs 48.7±1.92 breaths/min). CTRL and AIR did not differ (48.7 vs 49.0±1.92 breaths/min), and MIST and AIR+MIST (45.7 vs 47.1±1.92 breaths/min) did not differ. All other variables were not significantly different between treatments. In conclusion, the SCS appeared to be tolerated by cows and shows the potential to assist in alleviating heat stress. The cooling capacity needs to be evaluated under more extreme environmental conditions causing heat stress than those experienced during this study. Further testing is required to determine the cooled air temperature specifications and mist delivery frequency.