Effects of the daily heat load duration exceeding determined heat load thresholds on activity traits of lactating dairy cows
Introduction
An extensive literature review carried out by Gauly et al. (2013) clearly reveals that the exposure of animals to heat load will increase in the course of the predicted climate change, even under moderate climatic conditions in Central Europe. In Europe, dairy farms typically use naturally ventilated loose housing systems because of their moderate building costs, energy savings and positive impacts on the welfare of the cows. Therefore, cows are directly exposed to outside climatic conditions, which deteriorate because of climate change. The temperature-humidity index (THI) (NRC, 1971), a combination of ambient temperature and relative humidity, is commonly used to estimate the effects of the climate conditions on the heat load of cows (Herbut and Angrecka, 2018, Nasr and El-Tarabany, 2017, Schüller and Heuwieser, 2016).
Numerous studies in different climatic zones have indicated that the activity of cows is a sensitive indicator for heat load. Scientists have used many strategies to study the influence of climate conditions on cow activity. Different methods have been used to describe the climate conditions with THI, such as average THI per hour, per day or per defined parts of the day (Cincović et al., 2011, Herbut and Angrecka, 2018, Zähner et al., 2004). Furthermore, THI thresholds or THI classes were defined to distinguish different intensities of heat load (Allen et al., 2015, De Palo et al., 2005, Endres and Barberg, 2007, Provolo and Riva, 2009). The most important THI thresholds are 68 THI (Zimbelman and Collier, 2011) and 72 THI (Armstrong, 1994). They indicate the initial decrease in milk production. Herbut and Angrecka (2018) followed another new approach, which could be scientifically valuable. They divided the obtained THI values into periods characterized by different durations of THI throughout the entire day.
At the same time, other existing studies dealing with heat load of dairy cows have utilized many different methods to record cow behavior, such as video analysis or sensor technology (Allen et al., 2015, Herbut and Angrecka, 2018, Uzal Seyfi, 2013). Various activity traits have been analyzed, including the total lying/standing time, the number of steps, the number of lying bouts, the average length of lying bout, percentage of standing/lying cows, cow comfort index, and cow stress index (Brzozowska et al., 2014, Herbut and Angrecka, 2018, Uzal Seyfi, 2013). The lying time decreased significantly with increasing heat load, and consequently, the standing time increased (Cincović et al., 2011, Cook et al., 2007, De Palo et al., 2005, Tapkı and Şahin, 2006, Zähner et al., 2004). The number of lying bouts per day is not significantly influenced by the heat load (Brzozowska et al., 2014, Endres and Barberg, 2007, Zähner et al., 2004). The average duration of each lying bout decreased as the heat load increased (De Palo et al., 2005, Endres and Barberg, 2007). The quantitative impact on the activity change of cows in relation to daily heat load duration was not analyzed until now and is introduced in this paper.
The objective of the present study was to determine heat load thresholds of average daily THI that lead to changes in different activity traits of lactating high-yielding Holstein-Friesian cows in the moderate climatic zone. It is assumed that the thresholds leading to decline in milk production as given in the literature can be different from these of activity traits. Furthermore, we studied how the activity of the cows was influenced by the daily heat load duration exceeding the determined heat load thresholds. We hypothesized that increasing heat load duration exceeding the determined heat load thresholds result in significant activity changes of the cows in the functional groups, “resting behavior” and “locomotion behavior”, in addition to the effect of the average daily THI. The novelty of the results should help to interpret the activity of cows more precisely and develop prediction models for early detection of heat load in further studies.
Section snippets
Barn designs, animals
The experimental farm was located in Groß Kreutz, Germany, and was situated in the moderate climate zone between the maritime and continental climate (average annual temperature 9.9 ± 7.1 °C). The measurements were carried out in a naturally ventilated dairy barn with a loose housing system (Fig. 1). The barn was 38.88 m long and 17.65 m wide and had a north-south orientation with a deviation of 18° in the clockwise direction. The height of the fiber cement roof varied from 6.2 m at the gable
Determined heat load threshold of average daily THI per activity trait
The heat load threshold was determined for each activity trait within the functional groups “resting behavior” and “locomotion behavior”. The results were two different heat load thresholds. The determined heat load threshold of LT, LB, LBD, ST and SB was at an average daily THI of 67. The determined heat load threshold of SBD and NS was at an average daily THI of 47. Fig. 3 shows the AIC values of the broken-stick regressions from THI breakpoint 42–77 by the example of LT. As regards AIC
Discussion
In the present study, the effects of heat load conditions on the activity traits of lactating dairy cows were investigated. We used eight different climate measurement points inside the barn to representatively depict the heat load conditions of the cows. This is in accordance with previous studies, which demonstrate that the climate should be directly recorded inside the barn on account of differences to the climate outside (Gorniak et al., 2014, Schüller et al., 2013). Furthermore, there is a
Conclusions
Our study revealed that cows changed their activity affected by daily heat load duration exceeding determined heat load thresholds. The study determined the heat load threshold of 67 THI indicating changes in different activity traits (LT, LB, LBD, ST, SB) of lactating high-yielding dairy cows in the moderate climatic zone. There were significant changes in LT, ST, and NS induced by increasing daily heat load duration. The effect of the daily heat load duration additionally intensified the
Acknowledgements
This project was funded by the "optimized animal-specific barn climatization facing temperature rise and increased climate variability" (OptiBarn) project of the FACCE ERA-NET Plus Initiative "Climate Smart Agriculture" in Brussels and by the "Projektträger Bundesanstalt für Landwirtschaft and Ernährung" (ptble) (funding code: 315-06.01-2814ERA02C) in Bonn. The authors gratefully acknowledge the staff of the Department of Engineering for Livestock Management at ATB Institute, in particular,
Conflict of interest
The authors declare no conflict of interest.
Julia Heinicke is an agricultural scientist and works as PhD student at the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam, Germany. She studied agricultural science and did her Bachelor of Science and her Master of Science in Berlin, Germany. In October 2015, she started her PhD study at the ATB in the Department Engineering for Livestock Management. Her topic is the activity behavior of lactating dairy cows in relation to the climate conditions in the
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Julia Heinicke is an agricultural scientist and works as PhD student at the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam, Germany. She studied agricultural science and did her Bachelor of Science and her Master of Science in Berlin, Germany. In October 2015, she started her PhD study at the ATB in the Department Engineering for Livestock Management. Her topic is the activity behavior of lactating dairy cows in relation to the climate conditions in the experimental barn.
Gundula Hoffmann is a veterinarian and works as a scientist at the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam, Germany. She studied Veterinary Medicine at the University of Veterinary Medicine in Hanover, Germany and did her dissertation (DVM) at the Federal Agricultural Research Centre in Braunschweig, Germany. Since November 2008 she is working as a senior research scientist at the ATB in the Department Engineering for Livestock Management. Her work there is integrated in the ATB research program “precision farming in crop and livestock production” with a focus on sustainable milk production and innovative livestock husbandry systems.
Christian Ammon is responsible for design of experiments and statistical analyses in the Department Engineering for Livestock Management at the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam, Germany since June 2007. He studied agricultural sciences at the Justus-Liebig-University in Giessen, Germany and did his thesis at the Workgroup Biometry and Agricultural Informatics at the Martin-Luther-University Halle-Wittenberg in Halle, Germany.
Barbara Amon did her PhD in 1998. In 2007 she habilitated in agricultural engineering. Since 1999 senior research scientist at the University of Natural Resources and Life Sciences Vienna (BOKU), Austria, since 2012 also at the Agricultural Engineering and Bioeconomy (ATB), Germany. Since 2015 coordinator of ATB research programme "Precision farming in crop and livestock production". Research interests: greenhouse gas and nitrogen emission mitigation from animal husbandry systems.
Thomas Amon Since 2012, Thomas Amon is the head of Department “Engineering for Livestock Management” at the Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) in Potsdam, Germany. His research focusses on mitigation of ammonia and greenhouse gasses, airborne zoonoses and sustainable manure management, and research on advanced precision livestock farming systems regarding animal welfare, environmental, and hygienic issues. Simultaneously, he holds a W2 professorship for “Livestock – Environment – Interactions” at the Department of Veterinary Medicine, Freie Universität Berlin, Germany. He did his dissertation at the Technical University of Munich-Weihenstephan, Germany and his habilitation at University of Natural Resources and Life Science, Vienna.