Planting trees in pastures to provide shade for cattle has the potential to increase dairy and beef cattle productivity and improve the animals’ reproductive performance. This is demonstrated in studies carried out by researchers from the Brazilian Agricultural Research Corporation (EMBRAPA) in São Paulo and the Federal District. The study aimed to understand the benefits of providing thermal comfort to bulls and cows using a production system that combines cattle breeding, tree planting, and food cultivation in the same area. Known by the acronym ICLF (Integrated Crop-Livestock-Forestry), this system is based on a strategy of eco-efficient intercropping and crop rotation of plant-, animal-, and wood-based foods (see sidebar).
The study that researched the effects of adopting the ICLF system for raising beef cattle was conducted by EMBRAPA Southeast Livestock, in São Carlos, in inland São Paulo State. The study’s main conclusion is that planting shade trees in tropical pastures generates a microclimate that is more favorable to the animals’ physiological conditions, reducing water consumption frequency, improving animal welfare, and boosting their ability to gain weight.
“Continued exposure to excessive heat, in a pasture lacking trees, can put the cattle in a state of heat stress that impairs homeostasis, leading to nutritional and metabolic disorders,” explains veterinarian Alexandre Rossetto Garcia, coordinator of the study backed by FAPESP. Homeostasis is the physiological stability of living organisms.
Under heat stress, notes the researcher, the cattle activate mechanisms to regulate their body temperature, such as excessive sweating, changes in heart rate, and labored breathing. “The animals’ thermoregulation efforts sap energy that could be used for weight gain and reproduction,” he states. Additionally, under heat stress, the cattle tend to feel less inclined to eat, similar to humans on very hot days, which can also have an impact on their weight gain.
The field study was conducted at EMBRAPA’s Canchim Farm in São Carlos. Researchers selected 64 bulls, including Nelore, a Zebu breed that accounts for more than 80% of Brazilian beef cattle, and Canchim, the result of crossing Zebu cattle with Charolais (a European breed of Taurine cattle). At the outset of the study, the cattle were 24 months old and weighed on average 412 kilos (kg). The bulls were divided into two groups of 32. Each group occupied an area of 12 hectares covered with the same forage, Urochloa brizantha, better known to farmers by its old name, Brachiaria brizantha.
In one of the study’s areas, there were few trees and natural shade covered between 3% and 4% of the area — sun exposure conditions typical of the vast majority of beef cattle pastures in Brazil. The other area was adapted to the ICLF system, featuring 165 eucalyptus trees (Eucalyptus urograndis) per hectare, which generated a shade index between 30% and 35% throughout the year.
Over the course of 13 months, from January 2018 to January 2019, both groups of animals had unrestricted access to water and mineral supplementation to complement their diet and underwent the same health management procedures. During the study, which spanned all seasons, both groups were closely monitored.
Both areas had weather stations to measure air temperature, humidity, and environmental radiation, among other climatic variables. A thermography system aboard an aircraft identified and mapped heat zones and thermal comfort zones in the pastures. The cattle, in turn, had accelerometers (devices that analyze body acceleration) attached to a collar in order to monitor their movement and rest. Each individual animal’s temperature was constantly measured using infrared thermography (a technique for detecting the heat emitted by an object). Finally, blood, skin, and hair samples were collected for laboratory analysis and to check the herd’s capacity for heat loss and stress.
Juliana Sussai / EmbrapaJuliana Castro, an EMBRAPA researcher, enters data for animals in the field (below); around the bulls’ necks, an accelerometer attached to a collar allows researchers to analyze the cattle’s movementJuliana Sussai / Embrapa
The project was conducted in partnership with the University of São Paulo (USP), Fluminense Federal University (UFF), the Federal University of Pará (UFPA), and the Federal Rural University of Amazônia (UFRA). Two Italian educational institutions, the University of Bologna and the University of Milan, also participated in the study. The study and its findings were detailed in scientific articles published in Applied Animal Behaviour Science, in 2022, and in Agricultural Systems and Computers and Electronics in Agriculture, both in 2023.
Shade reduces the demand for water
One relevant finding from the study was the 26% reduction in visits to the water trough by the cattle allocated to the ICLF area, indicating a probable “water-saving” effect. The exact amount of water saved is the subject of another study due to be completed next year. “We plan to electronically map water consumption at the water trough,” says Garcia. “In Brazil, we have a population of 234 million cattle. The ability to save water, a limited natural resource, could bolster the sustainability of national production.
In both areas, cattle fattening was identical, with the bulls weighing around 650 kilos at the end of the study. Garcia notes, however, that in the ICLF area, the availability of grass was 20% to 30% lower due to shading. “This means that the group grazing in the shaded ICLF area was more biologically efficient and reached the same weight with less forage,” he says.
There are two possible factors that may have influenced this result of greater fattening with less forage — and the distinction between them will be the subject of future EMBRAPA studies. One factor is that the trees used for the ICLF system, as well as the rotation between pasture area and grain crops, increase the organic matter in the soil and result in grass that is higher in protein. The other factor is the reduction in short- and long-term stress generated specifically by the shade, which has been quantified in this line of research.
The study should also result in a new scientific publication, which is still being drafted, on the effects of shade on the reproductive capacity of bulls. For this, researchers are analyzing the animals’ testicular echotexture data from ultrasounds and semen quality. “Under shade, bulls maintain healthy testicular tissue and their ability to produce sperm remains unimpaired. Individuals under intense and continuous heat stress produce less and lower quality semen, negatively affecting their fertility,” notes Garcia.
In Brazil, pasture farming is also predominant in dairy cattle. More than 70% of milk production is carried out by crossbred cows, the result of crossing Zebu and European cattle, such as Girolando cattle, Gir cattle, and Dutch Belted cattle. Veterinarian Isabel Cristina Ferreira, of EMBRAPA Cerrados, in the Federal District, studied the impact of thermal comfort provided by the ICLF system on the productivity of Gir and Girolando cattle.
The study, which began in January 2017, lasted 33 months and was conducted at EMBRAPA’s Technology Center for Dairy Zebu Breeds, in Recanto das Emas (Federal District). During this time, researchers evaluated the performance of 141 cattle, half of which grazed in the sun, while the other half grazed in an ICLF system with 260 trees per hectare, which reduced insolation by 44%. Rectal temperature measurements, published in the Animals journal in August 2021, indicate that excess heat causes the cattle to enter a state of heat stress. The presence of shade trees, in turn, promotes animal welfare.
EMBRAPA’s researchers also noted a productivity gain generated by improving the environment’s climatic conditions. Gir cattle in the shaded area produced 24% more milk. During the 305-day lactation period, the average increase was 2.4 kg of milk per cow each day, which represented an additional 732 kg of milk over the entire period. Girolando cattle, in the shaded area, also produced more milk, but in insignificant quantities.
Alexandre Rossetto Garcia / EmbrapaSuperficial body temperature reading of a bull raised in a pasture with scarce trees (left) and of another animal living in a wooded area (right)Alexandre Rossetto Garcia / Embrapa
“The ICLF system is an economic alternative that provides thermal comfort to dairy cattle,” states the veterinarian. The other option, says Ferreira, is to raise the animals in stables, which requires investing in the physical structure and higher labor costs for management, as well as substantial electricity use for ventilation and humidification. Or even installing canvas shelters over the pasture, also known as “sombrites” in Brazil, which cannot withstand strong winds and rain.
The study performed at EMBRAPA Cerrados also confirmed that thermal comfort increases the reproductive capacity of dairy cows, with a fourfold increase in embryo production among animals grazing in the shade.
Cattle farmer Jônadan Hsuan Min Ma, owner of the 970-hectare Boa Fé farm in Conquista, Minas Gerais, has adopted the ICLF system on 38 hectares of his property, equivalent to 4% of the total. His dairy cattle herd consists of 330 cows, 95% of which are Girolando — the others are Gir and Dutch Belted cattle. According to the farmer, he adopted the ICLF strategy to improve the reproductive performance of Girolando heifers using in vitro fertilization.
According to Ma, under the comfort of eucalyptus tree shade, the embryo donor heifers increased the number of oocytes (female gametes) qualified for in vitro fertilization by 25% to 30%. “They began producing between 8 and 15 oocytes with each ovulation, enough to successfully fertilize between three and five embryos,” he says.
After the cows were moved to the shaded areas, says the cattle farmer, the conception rate in the herd, i.e. the number of heifers that became pregnant when inseminated, reached a level of 63% to 65%. Previously, when the cattle were raised in pastures without trees and shade, the rate was between 40% and 50%.
Intelligent strategy
Zootechnician Claudia Cristina Paro de Paz, researcher and technical director of the Institute of Zootechnics’ Research Programming Center, linked to the São Paulo State Department of Agriculture and Food Supply, says that the ICLF system is an intelligent approach to combating heat stress in cattle, which combines productive sustainability and greater profitability for rural farmers. “In addition to the income generated by livestock, there are further gains from the sale of agricultural production and timber,” says Paz, who did not take part in the EMBRAPA study but who has conducted studies in the area.
With the support of FAPESP, she studied the impact of tropical insolation on Zebu breeds, native to hot environments, and Taurine cattle, originally from temperate and cold climates. The study worked with Nelore, cattle of Indian origin present in Brazil since the nineteenth century, and Caracu Taurine cattle, which arrived in Brazil at the beginning of Portuguese colonization and are considered to be of European origin and better adapted to the Brazilian climate.
The study found that heat stress affects both breeds, but more intensely in the cattle of European origin, even after hundreds of years of exposure to the tropical climate. Blood analyses, rectal temperature measurements, and data collected from infrared thermography detected that, at high temperatures, the concentration of cortisol, a hormone that regulates the body and is commonly used as a stress response indicator, was higher in the bloodstream of Caracu cattle compared to Nelore cattle.
The level of heat shock proteins (HSP), which play a central role in the homeostasis process, was also higher among the Caracu cattle. The study generated three articles published in the scientific journals Livestock Science, in 2019 and 2022, and Tropical Animal Health and Production, in 2020.
“Even though this study did not evaluate other Taurine breeds that have only recently been gaining popularity in Brazil, such as Angus cattle, we can assume that the impact of heat stress is even greater among them,” says Paz.
Around 10% of Brazilian pastureland adopts the intercropping strategy
Created by EMBRAPA in the 1990s, the Integrated Crop-Livestock-Forestry (ICLF) system is a strategy that aims to promote biodiversity on cattle farms and increase their productivity. This approach involves rotating between agricultural and livestock activities in an area also used for planting trees. Well-managed crops and pastures, scientific studies show, provide an important secondary benefit: capturing carbon from the atmosphere, offsetting emissions from livestock. Cattle are a major generator of methane (CH4), one of the greenhouse gases responsible for global warming (see Pesquisa FAPESP issue nº 314).
In addition to improving animal welfare due to thermal comfort, ICLF systems have the potential to enhance nutrient cycling in the soil and help preserve the biodiversity and sustainability of farming activities. The ICLF system also diversifies production and can help mitigate the pressure to cut native vegetation in order to grow food or raise animals. According to EMBRAPA, ICLF systems are implemented in nearly 17.4 million hectares across Brazil, which is equivalent to 10% of the pastureland.
Projects
1. From the sky to the cell: A multidimensional approach to thermal comfort for animals in integrated crop-livestock-forest systems (ILPFs) (nº 19/04528-6); Grant Mechanism Regular Research Grant; Principal Investigator Alexandre Rossetto Garcia (EMBRAPA); Investment R$168,562.08.
2. Expression profile of genes associated with heat stress in Nelore and Caracu cattle (nº 16/19222-1); Grant Mechanism Regular Research Grant; Principal Investigator Claudia Cristina Paro de Paz (Institute of Zootechnics); Investment R$197,388.14.
Scientific articles
BARRETO, A. N. et al. Thermal comfort and behavior of beef cattle in pasture-based systems monitored by visual observation and electronic device. Applied Animal Behaviour Science. vol. 253. aug. 2022.
ROMANELO, N. et al. Thermal comfort of nelore (Bos indicus) and canchim (Bos taurus x Bos indicus) bulls kept in an integrated crop-livestock-forestry system in a tropical climate. Agricultural Systems. vol. 209. june 2023.
GARCIA, A. R. et al. Use of infrared thermography from a crewed aerial vehicle for remote sensing of tropical pasture areas with different levels of afforestation. Computers and Electronics in Agriculture. oct. 1, 2023.
PIRES, B. V. et al. Differential expression of heat shock protein genes associated with heat stress in nelore and caracu beef cattle. Livestock Science. vol. 230. dec. 2019.
LIMA, S. B. G. P. N. P et al. Effect of high temperature on physiological parameters of nelore (bos taurus indicus) and caracu (bos taurus taurus) cattle breeds. Tropical Animal Health and Production. mar. 3, 2020.
PIRES, B. V. et al. Meta-analysis and meta-regression of core body temperature in taurine and zebuine cattle under different environmental conditions. Livestock Science. vol. 265. nov. 2022.
REIS, N. S. et al. Shade modifies behavioral and physiological responses of low to medium production dairy cows at pasture in an integrated crop-livestock-forest system. Animals. aug. 15, 2021.
