Heat stress effects on milk yield traits and metabolites and mitigation strategies for dairy cattle breeds reared in tropical and sub-tropical countries

Heat Stress Effects on Physiological and Milk Yield Traits of Lactating Holstein Friesian Crossbreds Reared in Tanga Region, Tanzania

Global warming caused by climate change is a challenge for dairy farming, especially in sub-Saharan countries. Under high temperatures and relative humidity, lactating dairy cows suffer from heat stress. The objective of this study was to investigate the effects and relationship of heat stress (HS) measured by the temperature-humidity index (THI) regarding the physiological parameters and milk yield and composition of lactating Holstein Friesian crossbred dairy cows reared in the humid coastal region of Tanzania. A total of 29 lactating Holstein Friesian x Zebu crossbred dairy cows with 50% (HF50) and 75% (HF75) Holstein Friesian gene levels in the second and third months of lactation were used. The breed composition of Holstein Friesians was determined based on the animal recording system used at the Tanzania Livestock Research Institute (TALIRI), Tanga. The data collected included the daily temperature, relative humidity, daily milk yield, and physiological parameters (core body temperature, rectal temperature, respiratory rate, and panting score). THI was calculated using the equation of the National Research Council. The THI values were categorized into three classes, i.e., low THI (76-78), moderate THI (79-81), and high THI (82-84). The effects of THI on the physiological parameters and milk yield and composition were assessed. The effects of the genotype, the parity, the lactation month, and the interaction of these parameters with THI on the milk yield, milk composition, and physiological parameters were also investigated. The results show that THI and its interaction with genotypes, parity, and the lactation month had a highly significant effect on all parameters. THI influenced (p ˂ 0.05) the average daily milk yield and milk fat %, protein %, lactose %, and solids-not-fat %. As the THI increased from moderate to high levels, the average daily milk yield declined from 3.49 ± 0.04 to 3.43 ± 0.05 L/day, while the fat % increased from 2.66 ± 0.05% to 3.04 ± 0.06% and the protein decreased from 3.15 ± 0.02% to 3.13 ± 0.03%. No decline in lactose % was observed, while the solid-not-fat % declined from 8.56 ± 0.08% to 8.55 ± 0.10% as the THI values increased from moderate to high. Also, the THI influenced physiological parameters (p ˂ 0.05). The core body temperature (CBT), rectal temperature (RT), respiratory rate (RR) and panting score (PS) increased from 35.60 ± 0.01 to 36.00 ± 0.01 °C, 38.03 ± 0.02 to 38.30 ± 0.02 °C, 62.53 ± 0.29 to 72.35 ± 0.28 breaths/min, and 1.35 ± 0.01 to 1.47 ± 0.09, respectively, as the THI increased from low to high. The THI showed a weak positive correlation with the average daily milk yield and fat percentage, whereas the protein, lactose, and solids-not-fat percentages showed negative relationships with THI (p ≤ 0.05). CBT, RT, RR, and PS showed positive relationships (p ≤ 0.05) with THI. These negative relationships indicate that there is an antagonistic correlation between sensitivity to HS and the level of production. It is concluded that the THI, the genotype, the parity, and the lactation month, along with their interactions with THI, significantly influenced the milk yield, milk composition, and physiological parameters of lactating Holstein Friesian dairy crosses at THI thresholds ranging from 77 to 84.

Detection of haptoglobin and serum amyloid A as biomarkers in naturally infected Mycoplasma bovis calves

The livestock sector of Pakistan is increasing rapidly and it plays important role both for rural community and national economy. It is estimated that almost 8 million rural people are involved in livestock rearing and earning about 35-40 % of their income from the livestock sector. Mycoplasma bovis (M. bovis) infection causes significant economic losses in dairy animals especially young calf in the form of clinical illnesses such as pneumonia, poly-arthritis, respiratory distress and mortality. M. bovis is hard to diagnose and control because of uneven disease appearance and it is usually noticed in asymptomatic animals. For the identification of M. bovis in sub-clinical and clinical samples, determination of acute phase proteins i.e., haptoglobin (Hp) and serum amyloid A (SAA) are important tools for the timely diagnosis of disease. Therefore, early diagnosis of disease and hemato-biochemical changes are considered beneficial tools to control the infectious agent to uplift the economy of the dairy farmers. For this purpose, blood samples were collected from 200 calves of Bovidae family. Serum was separated from blood samples to determine the concentration of Hp and SAA, while blood samples were processed to determine hematological changes in blood from calves by using hematological analyzer. The blood plasma obtained from the blood samples was processed to measure oxidative stress factors. Lungs tissues from slaughterhouses/ morbid calves were collected to observe histopathological changes. The results of present study indicated that level of SAA and Hp remarkably increased (P < 0.05) in M. bovis infected calves in comparison to healthy calves. The oxidative stress markers indicated that nitric oxide and MDA levels in the infected calves increased significantly (P < 0.05), while infected claves had considerably lower levels of superoxide dismutase, catalase and glutathione. These findings indicate that oxidative stress play role to increase the level of APPs, while monitoring of APPs levels may serve as a valuable addition to the clinical evaluation of naturally infected calves with M. bovis. The hematological parameters were decreased significantly (P < 0.05). Altogether, this study suggests that Hp and SAA are proposed as promising biomarkers for detecting naturally occurring M. bovis infection in calves.

Pregnancy Rates of Holstein Friesian Cows with Cavitary or Compact Corpus Luteum

Cavitary corpora lutea are commonly observed during the estrous cycle in bovines. Since the quality of the corpus luteum (CL) is extremely important during embryo transfer when embryos are implanted into the recipient, the ultrasonographic examination of the CL is becoming more and more important in terms of the outcome of the procedure. In the present study, a total of 2477 ultrasonographic transrectal diagnoses were performed, and data were collected between the years of 2018 and 2020 in a large-scale Holstein Friesian dairy farm in Hungary. In 91.1% (n = 2257) and in 8.9% (n = 220) of the cases, compact CLs and cavitary CLs, respectively, were diagnosed at pregnancy diagnosis. The presence of a cavitary CL on the ovary at pregnancy diagnosis increased the odds of remaining open after pregnancy by 21 times compared to the presence of a compact CL (OR = 21.0, p < 0.001) in the cows. The presence of cavitary CL was not influenced either by month or season. Ovarian cysts were detected in 196 cases (8.0%) in the examined animals. The presence of a cavitary CL decreased by 9 times when an ovarian cyst was also diagnosed (OR = 9.0, 1.6% vs. 9.5%, p < 0.001). The presence of an ovarian cyst decreased the odds of established pregnancy by 81 times (OR = 81.1, p < 0.001). Based on our results, the presence of a cavitary CL between days 31 and 42 after artificial insemination is associated with a smaller chance of conception in Holstein Friesian cows. The presence of an ovarian cyst decreases the occurrence of cavitary CL and the chance of conception.

Influence of thermal heat load accumulation on daily rumination time of lactating Holstein cows in a zone with temperate climate

In the future, conflicts between animal welfare and climate change will gradually intensify. In the present study, we investigated the daily rumination time (RT) of lactating Holstein-Friesian cows in a zone with temperate climate and the effects of heat load duration and heat load intensity. Responses of individual cows to heat load were assessed, adjusting for milk yield, lactation number, days in milk as well as reproductive status and season. A total of 27,149 data points from 183 cows in a naturally ventilated barn in Brandenburg, Germany, were collected from June 2015 to May 2017. Ambient temperature and relative humidity were recorded at eight positions inside the barn every 5 min, and the temperature-humidity index (THI) was calculated. Based on THI, the degree of heat load was determined, using critical thresholds of THI = 68, 72, and 80. Daily RT was measured with a microphone-based sensor system (collar) on the cow's neck. The analysis models included autocorrelations in time series as well as individual cow-related effects. With each 5 min exposure to contemporaneous heat load, a decrease of approximately 1.17 min d-1 in RT per cow from non-heat stress to heat stress conditions by exceeding THI ≥68 (p < 0.01). This effect was intensified by exceeding the critical THI thresholds of 68 and 72. As heat load duration and intensity increased, daily RT decreased in comparison to daily RT under non-stress conditions. High-yielding (>38.4 kg milk/day) cows were more influenced in rumination time than low-yielding (≤28.8 kg milk/day) cows. With moderate contemporaneous heat load, RT decreased by 0.14 min d-1 per 5 min in high-yielding cows compared to low-yielding cows under moderate heat load. A decrease of 0.1 min d-1 was found in daily RT of mid-yielding cows. However, the delayed effects of heat load (one to three days after the heat stress event) were associated with days in milk and reproduction status. When the heat load duration lasted for several days, the responses were less pronounced than the impacts of contemporaneous heat load (when the heat stress event lasted for one day). Delayed mild heat load resulted in an increase in RT by 0.13 min d-1 in lactating cows ≤60 DIM. This was also found with delayed moderate heat load. Lactating cows ≤60 DIM showed a rise of 0.09 min d-1 in RT. RT also showed interactions with reproduction status of cows under delayed moderate heat stress. Lactating cows with ≤180 days of pregnancy showed an increase of 0.61 min d-1 in RT. Similarly, cows with >180 days of pregnancy had 0.64 min d-1 more RT compared to non-pregnant cows. Further analysis with higher temporal resolution of RT than data accumulation in 24-h blocks as well as the assessment of the correlation between feed composition, intake and rumination will elucidate the influence of heat load on daily RT.

The glass of milk half-empty? Dairy development and nutrition in low and middle income countries

Dairy products have an exceptionally rich nutrient profile and have long been promoted in high income countries to redress child malnutrition. But given all this potential, and the high burden of undernutrition in low- and middle-income countries (LMICs), why isn't dairy consumption more actively promoted in the developing world? In this review we focus on a broadly defined concept of "dairy development" to include production, trade, marketing, regulation, and demand stimulation. We address three key questions. First, how strong is the evidence on the importance of dairy production and consumption for improving nutrition among young children in LMICs? Second, which regions have the lowest consumption of dairy products? Third, what are the supply- and demand-side challenges that prevent LMICs from expanding dairy consumption? We argue that although more nutrition- and consumer-oriented dairy development interventions have tremendous potential to redress undernutrition in LMICs, the pathways for achieving this development are highly context-specific: LMICs with significant agroecological potential for dairy production primarily require institutional solutions for the complex marketing challenges in perishable milk value chains; lower potential LMICs require consumer-oriented trade and industrial approaches to the sector's development. And all dairy strategies require a stronger focus on cross-cutting issues of nutrition education and demand creation, food safety and quality, gender and inclusiveness, and environmental sustainability and resilience. We conclude our review by emphasizing important areas for research and policy expansion.

Potential for quantifying general environmental resilience of dairy cattle in sub-Saharan Africa using deviations in milk yield

Introduction: Genetic improvement of general resilience of dairy cattle is deemed as a part of the solution to low dairy productivity and poor cattle adaptability in sub-Saharan Africa (SSA). While indicators of general resilience have been proposed and evaluated in other regions, their applicability in SSA remains unexplored. This study sought to test the viability of utilizing log-transformed variance (LnVar), autocorrelation (rauto), and skewness (Skew) of deviations in milk yield as indicators of general resilience of dairy cows performing in the tropical environment of Kenya. Methods: Test-day milk yield records of 2,670 first-parity cows performing in three distinct agroecological zones of Kenya were used. To predict expected milk yield, quantile regression was used to model lactation curve for each cow. Subsequently, resilience indicators were defined based on actual and standardized deviations of observed milk yield from the expected milk yield. The genetic parameters of these indicators were estimated, and their associations with longevity and average test-day milk yield were examined. Results: All indicators were heritable except skewness of actual and standardized deviation. The log-transformed variance of actual (LnVar1) and standardized (LnVar2) deviations had the highest heritabilities of 0.19 ± 0.04 and 0.17 ± 0.04, respectively. Auto-correlation of actual (rauto1) and standardized (rauto2) deviations had heritabilities of 0.05 ± 0.03 and 0.07 ± 0.03, respectively. Weak to moderate genetic correlations were observed among resilience indicators. Both rauto and Skew indicators had negligible genetic correlations with both longevity and average test-day milk yield. LnVar1 and LnVar2 were genetically associated with better longevity (rg = -0.47 ± 0.26 and -0.49 ± 0.26, respectively). Whereas LnVar1 suggested that resilient animals produce lower average test-day milk yield, LnVar2 revealed a genetic association between resilience and higher average test-day milk yield. Discussion: Log transformed variance of deviations in milk yield holds a significant potential as a robust resilience indicator for dairy animals performing in SSA. Moreover, standardized as opposed to actual deviations should be employed in defining resilience indicators because the resultant indicator does not inaccurately infer that low-producing animals are inherently resilient. This study offers an opportunity for enhancing the productivity of dairy cattle performing in SSA through selective breeding for resilience to environmental stressors.

The Challenge of Global Warming in Water Buffalo Farming: Physiological and Behavioral Aspects and Strategies to Face Heat Stress

Water buffaloes have morphological and behavioral characteristics for efficient thermoregulation. However, their health, welfare, and productive performance can be affected by GW. The objective of this review was to analyze the adverse effects of GW on the productive behavior and health of water buffaloes. The physiological, morphological, and behavioral characteristics of the species were discussed to understand the impact of climate change and extreme meteorological events on buffaloes' thermoregulation. In addition, management strategies in buffalo farms, as well as the use of infrared thermography as a method to recognize heat stress in water buffaloes, were addressed. We concluded that heat stress causes a change in energy mobilization to restore animal homeostasis. Preventing hyperthermia limits the physiological, endocrine, and behavioral changes so that they return to thermoneutrality. The use of fans, sprinklers, foggers, and natural sources of water are appropriate additions to current buffalo facilities, and infrared thermography could be used to monitor the thermal states of water buffaloes.