This study examined the influence of ambient temperature (AT), relative humidity (RH) and temperature-humidity index (THI) on milk yield (MY) and milk compositions (MC) of West African Dwarf (WAD) ...goats using a total of thirty-six (36) lactating does. The goats were milked twice daily for twelve (12) weeks during which, AT and RH were monitored. The AT and RH data were used to generate THI. The milk collected at every milking was quantified and also analysed for MC, The AT, RH and THI during each milking period were categorized into low, medium and high ranges, under which the corresponding MY and MC were fixed. The data generated were subjected to Analysis of Variance of a Completely Randomized Design. The result revealed that the highest MY (350.28 mL), recorded during low AT range, was not significantly different from 329.43 mL obtained during medium AT, while high RH range (70-99%) facilitates higher MY (364.30 mL) compare to low and medium ranges. AT exerted no significant difference on all the MCs except protein. Milk fat was highest (7.34%) at low THI, while the lactose (11.30%) at high THI range was significantly higher compared to other ranges. A relatively higher MY (324.35 mL) and milk density (1034.94 kg/m3) was obtained within medium THI range (75.6-85.6). It is concluded that, AT and RH exhibit a synergistic effect on MY and some of the MCs.It is recommended that thermo-comfort THI for dairy WAD goats is between 75.6 and 85.6.
Heat stress is known to affect performance of dairy cows experiencing prolonged periods of high temperature and relative humidity. Less is known about its effects in cooler climates. The goals of the ...present study were to determine the prevalence of days susceptible to cause mild heat stress in dairy cows living in a humid continental climate and to investigate the relationship between the number of consecutive days of mild heat stress and milk, fat, protein, and lactose production. A 6-yr data set (2010–2015) containing 606,031 milk analysis records for 34,360 Holstein dairy cows at different parities was matched with the corresponding daily maximum temperature–humidity index. Exposure to heat stress conditions was divided into 5 categories corresponding to 0, 1 to 2, 3 to 4, 5 to 6, and 7 to 8 consecutive days before milk test date. On average, cows were exposed to heat stress conditions for 135.8 ± 5.9 d/yr in Southwest Quebec and 95.3 ± 10.2 d/yr in Eastern Quebec. Cows experiencing heat stress conditions produced on average less fat, protein, and energy-corrected milk and lower fat and protein concentrations. The decrease in milk fat reached 6% for category 7 to 8 exposure of cows in parity 3 or more. The association between exposure category and milk yield and lactose yield and concentration was weak. Heat stress lowered milk fat and protein production but had little effect on milk volume output. Further research is necessary to better understand the mechanism underlying the effects of sporadic low- to medium-intensity heat stress on dairy productivity.
Increased ambient temperatures has been identified to contribute to reproductive outcomes for several domesticated species, but its impact on equine reproduction has not been previously investigated. ...Therefore, this study aimed to examine the relationship between ambient climatic conditions, as measured by temperature-humidity index (THI) between day 7 and day 14 of gestation, and early embryonic loss (EEL) in recipient mares undergoing embryo transfer.
The study examined records from 834 embryo transfers at an equine breeding facility in Victoria, Australia. Early embryonic loss was defined as a negative transrectal ultrasound on day 14 of gestation after an embryo was transferred on day 7. Both maximum THI on the day of transfer (day 7) and mean THI between day 7 and day 14 were investigated for association with the outcome of EEL using multivariable logistic regression, controlling for confounders including embryo age and quality, recipient mare quality and embryo transfer quality.
EEL was observed in 21% of embryo transfers. A five-unit increase in maximum THI on the day of transfer was associated with an 18% increase in the odds of EEL (p = 0.01). Similarly, the odds of EEL increased by 25% for each five-unit increase in mean THI between day 7 and 14 (p = 0.003).
As both single and cumulative episodes of high THI were associated with increased EEL in embryo transfer mares from this equine breeding facility, further studies are warranted to identify similar effects in a broader population, establish causality and evaluate possible mitigation strategies in anticipation of heat waves.
•Heat stress reduces reproductive outcomes in mares.•High temperature at equine embryo transfer associated with early embryonic loss.•High temperature after embryo transfer associated with early embryonic loss.
The objective of this study was to evaluate the reproductive performance of the Holstein (HO) and their backcross HO × Brown Swiss (BS) under Egyptian subtropical conditions. The backcrosses were HBH ...(HO sires crossed with F1 BS × HO cows) and HHB (HO sires crossed with F1 HO × BS cows). Several reproductive indices and health traits for different genotypes were measured, and the effect of temperature–humidity index level (THI) on reproductive performance was investigated. Reproductive indices of the HHB backcross were better than those of the HO. The conception (30.1%) and pregnancy (28.9%) rates of the HHB backcross were significantly higher than those of the HO (28.1% and 22.6%, respectively). The calving interval and the days open of the HHB backcross were significantly shorter than those of the HO. The fertility of the HHB backcross was not affected by the level of the THI. The conception and the pregnancy rate of the HO decreased from 35.8% and 29.4%, respectively, at low THI to 16.1% and 12.1%, respectively, at high THI. The HHB backcross had the significant lowest incidence of retained placenta and metritis (9.6 and 16.9, respectively). In conclusion, despite their high milk production efficiency, pure HO had retarded reproductive performance and adaptability. On the other hand, the HHB backcross had a better adaptability and fertility under Egyptian conditions.
The data set for this study comprised 1,488,474 test-day records for milk, fat, and protein yields and fat and protein percentages from 191,012 first-, second-, and third-parity Holstein cows from ...484 farms. Data were collected from 2001 through 2007 and merged with meteorological data from 35 weather stations. A linear model (M1) was used to estimate the effects of the temperature-humidity index (THI) on production traits. Least squares means from M1 were used to detect the THI thresholds for milk production in all parities by using a 2-phase linear regression procedure (M2). A multiple-trait repeatability test-model (M3) was used to estimate variance components for all traits and a dummy regression variable (t) was defined to estimate the production decline caused by heat stress. Additionally, the estimated variance components and M3 were used to estimate traditional and heat-tolerance breeding values (estimated breeding values, EBV) for milk yield and protein percentages at parity 1. An analysis of data (M2) indicated that the daily THI at which milk production started to decline for the 3 parities and traits ranged from 65 to 76. These THI values can be achieved with different temperature/humidity combinations with a range of temperatures from 21 to 36°C and relative humidity values from 5 to 95%. The highest negative effect of THI was observed 4 d before test day over the 3 parities for all traits. The negative effect of THI on production traits indicates that first-parity cows are less sensitive to heat stress than multiparous cows. Over the parities, the general additive genetic variance decreased for protein content and increased for milk yield and fat and protein yield. Additive genetic variance for heat tolerance showed an increase from the first to third parity for milk, protein, and fat yield, and for protein percentage. Genetic correlations between general and heat stress effects were all unfavorable (from −0.24 to −0.56). Three EBV per trait were calculated for each cow and bull (traditional EBV, traditional EBV estimated with the inclusion of THI covariate effect, and heat tolerance EBV) and the rankings of EBV for 283 bulls born after 1985 with at least 50 daughters were compared. When THI was included in the model, the ranking for 17 and 32 bulls changed for milk yield and protein percentage, respectively. The heat tolerance genetic component is not negligible, suggesting that heat tolerance selection should be included in the selection objectives.
In the last decades, livestock species have been severely affected by heat stress because of increasing temperatures, which has threatened animal welfare and decreased production. Based on thermal ...comfort indices and ensemble climate projections, we analyzed the current and future global spatiotemporal patterns of the heat exposure of cattle in 10 agroclimatic zones. The results show that ~7% of the global cattle population is currently exposed to dangerous heat conditions. This percentage is projected to increase to ~48% before 2100 under a scenario of growing emissions. Tropical agroclimatic zones are expected to face an early increase in the exposure to intense heat before 2050. Heat exposure was negatively correlated with the socioeconomic variables, showing that poor and livestock-dependent tropical countries are the most affected. Our results demonstrate the near-future consequences of heat stress on livestock, emphasizing the limited time available to implement effective abatement strategies.
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•Heat stress is increasingly affecting global livestock farming.•We analyzed cattle exposed to heat stress in 10 agroclimatic zones.•~48% of the global cattle population can be exposed to severe heat stress by 2100.•Humid agroclimatic zones in tropical regions are the most vulnerable.
The presented study determining the relationship between the Temperature Humidity Index (THI) value during the summer months (June-August) and daily behaviour of 40 Holstein-Friesian dairy cows, ...including the length of standing, laying bouts and locomotor activity. Behaviour observations were conducted on a preferences test concerning their choice to time and place of rest with respect to time duration of THI: neutral (maximum 3 h with THI = 68), warm (time of THI > 68 occurrence lasted less than 12 h) and hot (time of THI > 68 occurrence lasted longer than 12 h). Obtained results was processed using analysis of the Spearman's correlation coefficient with significant at p < .05. The results showed a decrease in daily total lying time between the neutral and hot periods from 9.9 to 7.8 h/d. Along with the increase in THI by 1 unit between the warm and hot periods, there was observed a decrease in total lying time by 38 min/d in the cubicles. With an increase in the THI was also observed an increase by 15 min/d in the lying cows in the manure alleys during the night-time. During the warm and hot periods, the cows' activity showed a negative correlation with the increasing THI. Cows changed their behaviour during the summer depending on the prevailing environmental conditions. The behavioural studies on cows, without taking into account the variability of microclimate conditions, can lead to their inaccuracy and the misrepresentation of their results.
In an attempt to determine the possible detrimental effects of continuous selection for milk yield on the genetic tolerance of Zebu cattle to heat stress, genetic parameters and trends of the ...response to heat stress for 86,950 test-day (TD) milk yield records from 14,670 first lactations of purebred dairy Gir cows were estimated. A random regression model with regression on days in milk (DIM) and temperature–humidity index (THI) values was applied to the data. The most detrimental effect of THI on milk yield was observed in the stage of lactation with higher milk production, DIM 61 to 120 (−0.099kg/d per THI). Although modest variations were observed for the THI scale, a reduction in additive genetic variance as well as in permanent environmental and residual variance was observed with increasing THI values. The heritability estimates showed a slight increase with increasing THI values for any DIM. The correlations between additive genetic effects across the THI scale showed that, for most of the THI values, genotype by environment interactions due to heat stress were less important for the ranking of bulls. However, for extreme THI values, this type of genotype by environment interaction may lead to an important error in selection. As a result of the selection for milk yield practiced in the dairy Gir population for 3 decades, the genetic trend of cumulative milk yield was significantly positive for production in both high (51.81kg/yr) and low THI values (78.48kg/yr). However, the difference between the breeding values of animals at high and low THI may be considered alarming (355kg in 2011). The genetic trends observed for the regression coefficients related to general production level (intercept of the reaction norm) and specific ability to respond to heat stress (slope of the reaction norm) indicate that the dairy Gir population is heading toward a higher production level at the expense of lower tolerance to heat stress. These trends reflect the genetic antagonism between production and tolerance to heat stress demonstrated by the negative genetic correlation between these components (−0.23). Monitoring trends of the genetic component of heat stress would be a reasonable measure to avoid deterioration in one of the main traits of Zebu cattle (i.e., high tolerance to heat stress). On the basis of current genetic trends, the need for future genetic evaluation of dairy Zebu animals for tolerance to heat stress cannot be ruled out.
•An artificial heating protocol was validated by climate and animal parameters.•Weight of pigs had no effect on physiological parameters during a higher heat load.•The effect of reduced stocking ...density on heat stress in pigs was investigated.•A lower stocking density decreased the rise in rectal temperature during heat load.•A lower stocking density tended to result in a better daily gain across the trial.
As climate change intensifies, heat stress mitigation for pigs becomes more important. Trials involving induced heat waves are useful to test several measures (e.g. reduced stocking density) at a faster rate, but only when accurately evaluated and validated. In the present study, we investigated the suitability of an artificial heating protocol at different pig weights (experiment 1). The impact of different stocking densities on fattening pigs during an artificial heat wave (experiment 2) was also investigated. Experiment 1: Forty 20-week-old pigs weighing 96.5 ± 7.3 kg (W100) and forty 17-week-old pigs weighing 72.7 ± 9.9 kg (W70) were housed in two compartments. An artificial heat wave (heat load) was induced for 3 days. During 3-day periods before, during and after the heat load, physiological parameters (respiration rate (RR), rectal temperature (Trectal), skin temperature (Tskin) and behavior) were measured and average daily feed intake was observed. Ambient temperature, relative humidity and temperature-humidity index (THI) were monitored. Experiment 2: A total of 150 fattening pigs were randomly divided into three treatment groups: SD1.3 (1.3 m2/pig), SD1.0 (1.0 m2/pig) and SD0.8 (0.8 m2/pig). All pens had a total pen surface of 4.88 m2, corresponding with 4, 5 and 6 fattening pigs in the SD1.3, SD1.0 and SD0.8 groups, respectively. The heat load was induced for 7 days on week 21. Respiration rate and Trectal were observed as in experiment 1. Average daily gain and average daily feed intake were also noted. During the heat load, THI reached ≥ 75 (78.4 (experiment 1) and 78.6 (experiment 2)), even when relative humidity decreased to ± 45%. Every physiological parameter showed significant increases during the heat load. The prolonged heating protocol in experiment 2 also provoked significant decreases in average daily feed intake (15%) and average daily gain (19%) for all groups. Weight within the studied range of 70–100 kg did not have a significant impact on any of the parameters. However, Tskin was affected by both weight and heat load (P < 0.05), where Tskin from W100 was always lower in comparison to W70. In addition, we found that 0.8 m2/pig doubled the increase of Trectal during the heat load, namely SD0.8 (0.22 °C) compared to SD1.0 (0.12 °C) (P = 0.033) and SD1.3 (0.13 °C) (P = 0.053). This suggests that pigs housed at higher densities are less able to regulate their internal heat production. However, RR and performances were not significantly affected by heat load in this experimental set-up. A stocking density of 1.0 m2/animal may be sufficient to mitigate some negative effects of heat stress.
Climate change is a major world-wide challenge to livestock production because food security is likely to be compromised by increased heat stress of the animals. The objective of this study was to ...characterize, using bioclimatic indexes, two livestock regions located in an arid zone of México, and to use this information to predict the impact of global warming on animal production systems of these regions located in the state of Baja California (México). A 5-year database (i.e., 2011 to 2015) consisting of about one million data points from two zones (i.e., coast, valley) from four meteorological stations in the north of Baja California were used. Bioclimatic indexes were constructed for the four types of livestock production systems most common in this region, being: dairy cattle, beef cattle, sheep, pigs. The temperature-humidity index (THI) thresholds used to classify heat stress were determined and scaled for each livestock species as: THIbeef and THIpig 74 units; THImilk 72 units; and THIsheep 23 units. Statistical differences between indices were detected (P < 0.01) during summer for the valley and coast zones as (THIbeef = 72.9 and 51.8; THImilk = 80.6 and 67.4; THIpigs = 83.9 and 65.2; THIsheep = 29.5 and 20.1 units). Coast zone weather did not suggest vulnerability of livestock production systems to heat stress at any time of the year, but heat stress risk during summer for valley zone dairy cattle, sheep and pigs was classified as severe, but lower for feedlot cattle. Prediction models showed significant adjustment just in the coastal zone for THImilk, THIsheep, and THIsheep, suggesting more impact of global warming during summer in the coastal zone. Use of management strategies to reduce heat load of domestic animals during summer in northern Baja California is essential to maintain their productivity, with more emphasis in the valley zone.
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•A 5-year database consisting of almost one million points of an arid zone were analyzed.•Bioclimatic indexes were estimated for dairy and beef cattle, as well as for sheep and pigs.•Temperature-humidity index (THI) thresholds for each livestock systems were calculated in two different zones of northwestern México.•Duration and intensity of heat stress were estimated to determine vulnerability of each livestock system on the valley zone.•Environmental strategies should be considered in the short term to avoid the negative effects.
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