•This study evaluates the effect of heat stress on milk production and describes the pattern of response of milk yield to increasing heat load, in small holder dairy farms in sub-Saharan Africa.•Milk ...yield showed a W-shaped pattern of response across the THI scale.•Cows experienced heat stress in the THI window between THI values of 67 and 76.•Milk loss plateaued beyond THI value of 76 suggesting that the animals acclimatized to the heat stress conditions despite the initial heat load shock.
This study evaluates the effect of heat stress on milk production and describes the pattern of response of milk yield to increasing heat load, using temperature-humidity index (THI) on test-day milk records of small holder dairy cattle herds in the sub-Saharan African climate of Tanzania. Climate data obtained from aWhere, an agricultural weather data platform (http://www.awhere.com) was analysed with 14,367 first lactation test day milk records of 3511 dairy cows collected between 2016 and 2019. THI was calculated from daily maximal temperatures and daily minimum humidity. Three sets of analysis were performed. In the first and second analysis, two mixed effect repeatability models were fitted with THI treated as a categorical variable grouped into 5 classes (THI1= 61 - 66, THI2= 67 - 71, THI3= 72 - 78, THI4=79 - 81, THI5=82 - 86), to obtain least squares estimates of THI effect on milk production, and as a continuous variable within THI classes to identify THI thresholds at which milk yield started to decline. In the third analyses, one quadratic polynomial regression (POL) and three regression spline functions namely piecewise linear spline function (PLF), natural splines function (NSF) and cubic splines function (CSF) were fitted to determine the average effect of THI on milk yield in the population and describe the pattern of response of milk yield to increasing head load.
The results show that heat stress reduced milk yield by 4.16% to 14.42% across THI groups, with daily milk yield being the highest in THI1 (7.40±0.39 litres) and the lowest in THI4 (6.33±0.32).
Regression coefficients within groups showed significant daily milk yield decrease in THI2 (-0.09) and THI3 (-0.06), but not for other THI classes, indicating that cows experienced heat stress between THI values of 67 and 76 and milk loss plateaued afterwards, suggesting that the animals acclimatized to heat stress conditions beyond THI value of 76. At the population level, THI and its squared term were significantly negatively and positively (-0.61, 0.004) associated with milk production, indicating a non-linear relationship between milk yield and THI. The CSF model showed better goodness of fit and predictive ability than other models for predicting future population response of milk yield to heat stress in small holder dairy farms in Tanzania.
Herd management strategies and animal husbandry measures are needed in small holder dairy farms in Tanzania to minimize the impact of heat stress on milk yield and income of the farmers.
•Remote sensing based temperature-humidity index (MTHI) was proposed to explore the spatio-temporal characteristics of urban thermal comfort.•Landscape metrics were utilized to investigate the ...response of urban thermal comfort to urban landscape patterns seasonally and annually.•The impacts of landscape patterns on urban thermal comfort were analyzed at both macro and micro scale.
The traditional in situ data based temperature-humidity indexes (THIs) have been widely used in the assessment of the quality of urban thermal environment, with the spatial details of thermal comfort currently unavailable. In this study, the THI is modified replacing the required in situ air temperature and relative humidity with remote sensing retrieved Land Surface Temperature and Normalized Difference Moisture Index, being the modified temperature-humidity index. The proposed remote sensing based index is then used to explore the spatio-temporal characteristics of urban thermal comfort, which are used to describe the urban thermal comfort grading in different seasons and the landscape metrics as well as to investigate the response of urban thermal comfort to landscape patterns seasonally and annually. The results show that at the macro scale, the impacts of landscape patterns on thermal comfort are the most important in summer with water bodies and built-up land being the most desirable and uncomfortable types, respectively. The opposite results are found in spring and winter despite the relatively less important effect in winter. At the micro scale, the variance contribution rate of the Percentage of Landscape to the MTHI is above 70%, and that of the Landscape Division Index and Aggregation Index is from 10% to 38.1%. It indicates that the composition of the landscape is the main factor affecting urban thermal comfort and is better than the landscape structure. The MTHI based on remote sensing data can monitor the spatial distribution of urban thermal comfort and is suitable to explain the reasons for the thermal comfort temporal variations.
We investigated the effect of the temperature-humidity index (THI) on the conception rate (CR) in Holstein heifers and cows receiving in vitro-produced (IVP) Japanese Black cattle fresh embryos. IVP ...embryos were transferred to Holstein heifers (n = 1,407) and cows (n = 3,189) on 245 commercial farms. The monthly average ambient temperature (AT) and THI ranged from 4.7 to 29°C and 41 to 81, respectively; both were the highest in August. The monthly CR ranged from 16.3% to 46.7% in cows and 23.8% to 74.1% in heifers. The CR of heifers was unaffected by THI, AT, or the month of embryo transfer. However, these parameters affected the CR of cows. The CR at THI values of 61–65 and 71–75 was greater than that at THI > 75, whereas other THI values had no effect. The CR at temperatures > 25°C was lower (P = 0.008) than that at temperatures of 15–20°C and 20–25°C. Moreover, the CR was lowest (P = 0.003) in July. THI and parity (P = 0.057 and P = 0.001, respectively) and AT and parity (P = 0.019 and P = 0.001, respectively) showed significant effects on CR; however, there was no interaction between these two factors. In conclusion, AT > 25°C and THI > 75 adversely affect the CR outcome in cows but not in heifers.
To evaluate various influencing factors of rumination time (RT) variation in Holstein cattle in China, data from 38 consecutive months from 864 lactating cows using three-axis accelerometer based ...wearable neck sensors were collected. Year, season, parity, THI, bihourly rumination time in minutes (R2h), and days in milk (DIM) had a significant effect on the diurnal rhythm of rumination. The average daily rumination time in minutes (DRT) was 527, increased in spring (550), and declined in summer (514). A prenatal decline in DRT from 557 at −18DIM to 344 at DIM0 and its gradual rise (597) on DIM4, gave valuable insights regarding periparturient management. A stable return of DRT was observed by DIM30, later rumination time gradually decreased with increasing DIM. From 22:00 to 04:00 the R2h was higher and had a strong correlation (0.45) with DRT. Milking and feeding time drop in R2h pattern, though significant (P < 0.05), was consistent between concerning parity and season. The average DRT of the first parity cows was lower (29 min/d) than multiparous cows, while this difference was greater (47 min d−1) in summer. DRT reached the highest daily average upon THI63–65, decreased gradually in winter, and touched the lowest during extreme summer. A chronological influencing concomitance of THI63 and THI68 with the RT of dairy cows provided valuable insights into THI thresholds for RT decline and heat stress. RT was maximum at THI63, while higher the duration spent above the THI thresholds of 68 and 72, more pronounced was the RT decline.
•Three-axis accelerometer-based wearable reliably predicts the rumination behaviour.•Daily rumination time (DRT) is lower in summer months, cooling measures helps.•DRT of primiparous dairy cows is higher than multiparous cows.•DRT decline sharply around parturition and rise back to maximum at day 4.•DRT is highest at THI 63–65, decrease at THI 68 and declines markedly after THI 72.
There are clear signs that milk production growth is leveling off, and recently even declining, in China. Heat stress is one of the main reasons for the recent reduction in milk production. In this ...study, we computed the change in milk production as a result of heat stress in major milk production areas in China. We constructed a temperature–humidity index (THI) spatial layer to understand the monthly distribution of heat and moisture. We documented specific areas in northern China where cattle were at high risk to heat stress in specific months. THI values exceeded the threshold above which milk production declines during months of June, July, and August. Especially during July, the THI value was higher than the production threshold in recent years (2008 to 2016) and in projected future scenarios (2050 and 2070). THI-based milk yield losses were up from 0.7 to about 4 kg per cow per day in July 2016. These losses are projected to increase from 1.5 to 6.5 kg in 2050 and 2 to 7.2 kg in 2070 (representing production losses between 15 and 50%). These results suggest that climate change will have significant consequences for the dairy sector in major milk-producing areas in China. Our results are useful in identifying areas susceptible to heat stress where adaptive livestock management practices are needed to prevent significant production decreases.
The objective of this study was to devise an optimal method for estimating air temperatures outside pig farms to be able to evaluate the genetic performance of pigs. Using daily temperature data from ...Japan Meteorological Agency meteorological stations, we investigated the optimal number of observation weather stations (number of records), and methods of estimating outside temperature when temperature records are missing. We also considered the possibility of using relative humidity data. Our results showed that it is possible to use records from the three nearest weather stations to estimate off‐farm ambient temperatures. We also concluded that estimates of outside temperatures when records are missing can be made by using data from at least one weather station that holds a full set of data. The correlation coefficients between the true THI (temperature‐humidity index) and the estimated THI and the average daily temperature were almost the same, indicating that the daily average temperature can be used instead of estimated THI.
Adequate supply of high-quality colostrum is essential for calf health. Colostrum production, at first milking, varies between animals and seasons, but herd-level and management associations with ...colostrum production have not been well described. Our objectives were to (1) describe colostrum production and colostrum handling practices and (2) to identify individual cow, herd management, and environmental factors associated with colostrum production. A convenience sample of 19 New York Holstein dairy farms (620 to 4,600 cows) were enrolled in this observational study to describe colostrum production and to evaluate cow, management, and prepartum environmental factors associated with colostrum yield and Brix %. Herd owners or managers were given a colostrum management questionnaire, and farm personnel recorded individual colostrum yield and Brix % for primiparous (PP; n = 5,978) and multiparous (MPS; n = 13,228) cows between October 2019 and February 2021. Temperature, relative humidity, and light intensity were measured by sensors placed in each farm's close-up dry cow pens for the entire length of the study. Median colostrum yield for each farm ranged from 2.5 to 7.6 kg for PP and 4.0 to 7.7 kg for MPS cows. Mean Brix % from each farm ranged from 22.2 to 27.9% for PP and 22.0 to 28.8% for MPS cows. Lowest colostrum yield from PP animals was associated with calf sex (female) and colostrum Brix % (≤22%). Greatest colostrum yield from MPS cows was associated with colostrum Brix % (≤22%), calf sex (twin), dry period length (>67 d), gestation length (283–293 d), an alive calf, second parity, previous lactation length (>344 d) and previous lactation 305-d mature equivalent milk yield (>13,091 kg), heat and humidity exposure area under the curve (AUC) 7 d before calving (>69.2 average temperature-humidity index per 30-min interval), and light intensity AUC 14 d before calving (>154.2 average lux per 15-min interval). Greatest colostrum Brix % from PP animals was associated with calf sex (male), an alive calf, and light intensity AUC 14 d before calving (≤64.0 average lux per 15-min interval). Greatest colostrum Brix % from MPS cows was associated with dry period length (>67 d), an alive calf, 305-d mature equivalent milk yield of previous lactation (≤15,862 kg), gestation length (274–282 d), colostrum yield (<6 kg), fifth or greater parity, and heat and humidity exposure AUC 7 d before calving (≤50.1 average temperature-humidity index per 30-min interval). Dairy producers can use this information to recognize the variation in colostrum production and alter colostrum management programs in anticipation of periods of low production or quality.
•The relationship between environmental, physical and physiological variables in the thermal tolerance of cattle was analyzed by path and logistic analyses.•Among the locally adapted breeds studied, ...there were differences in responses to heat stress.•Rectal temperature has been shown to be a late response to heat stress and varies by breed.
Environmental conditions, along with physiological and morphological conditions of cattle from six different local adapted breeds in Brazil were analyzed to evaluate, through path and logistic regression analyses, the response to temperature and humidity variation, more specifically to heat stress. Breeds included Bos taurus ibericus (Crioulo Lageano, Curraleiro Pé Duro, Junqueira, Pantaneiro), Bos taurus ibericus x Bos taurus aquitanicus (Mocho Nacional) and Bos taurus indicus (Indubrasil) totaling 548 observations. The statistical analyses carried out were path analysis and logistic regression using SAS software to determine the relationship between the Temperature Humidity Index (THI) and physiological parameters for the different breeds. Path analysis showed the relationship between environmental conditions and physiological variables such as respiratory rate, heart rate, blood parameters and rectal temperature, as well as morphological traits. Logistic regression analysis showed that the Mocho Nacional breed presented an increased respiratory rate before the other breeds, and Junqueira was the last breed. The change in rectal temperature occurred first in the Pantaneiro breed and last in the Indubrasil breed. The use of path analysis and logistic regression allows a better comprehension of how the animal organism's responses in each breed to environmental alterations that lead to heat stress.
The climatic conditions in Serbia are suitable for the development of heat stress in cows. The values of the bioclimatic THI indicator point to a positive trend in increase in the number of days ...during which the conditions for the occurrence of heat stress are present. In cows, a change in body temperature is noted, activation of the cooling mechanisms, along with reduced milk production and reproductive efficiency. The behavioral changes of cows occur on farms, and the level of welfare decreases slightly when measured according to animal-based criteria. Changes in productivity are mainly related to metabolic, hematological and inflammatory adaptations. The metabolic adaptation that leads to a decrease in milk production is related to an increase in sensitivity to insulin with reduced lipolysis, an increase in TNF-a in cows, as well as to metabolic rearrangements of the mammary gland. Reproductive efficiency is reduced and is characterized by reduced expression of estrus and reduced response to estrus induction procedures. High ambient temperatures, in in vitro conditions, can affect the stability of laboratory parameters in the blood serum of cows. Cows exhibit different profiles of resilience to heat stress, and the study of resilience curves, for productive and blood parameters, represents the starting point for selecting cows that will tolerate heat stress better. For this purpose, the cumulative effects of heat stress expressed in the area under the resilience curve can be used. Certain precautionary measures such as providing shade, cooling by using fans and sprinklers or some other advanced technological methods, can reduce losses during heat stress. All of the above indicate that it is necessary to pay extra attention to all aspects of health care and production on cow farms in Serbia during late spring and summer when the animals are exposed to heat stress.
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