Ethological behavior of Bos taurus, Bos indicus, and Caqueteño Creole cattle in three tree cover systems of Brachiaria decumbens paddocks at the Amazon foothills in Colombia

The study was conducted at the Amazon Research Center CIMAZ MACAGUAL of the University of Amazonia, Colombia, with a tropical rain forest climate (Af). The behavior of Bos taurus, Bos indicus, and Caqueteño Creole cattle, the animals were observed in paddocks with three levels of scattered tree cover density. The pasture was composed of Braquiaria decumbens with 35 days of regrowth. Direct observations were made from 9:00 a.m. to 5:00 p.m. with 10-minute intervals between the recording of the activities. The activity performed most often during the day by all of the animals was grazing under the sun, and those who pasture the most are the Caqueteño Creole, followed by the Bos indicus and, finally, the Bos taurus. Ruminating was the second most important activity performed by the cattle, having presented the same tendency. In the paddocks with a low level of tree cover, the animals pasture more in the shade; this trend is more relevant among B. taurus cattle. Caqueteño Creole cattle dedicate less time to water consumption and rest, spending more time grazing, in the high and medium cover levels, they interrupt the grazing at noon for a shorter time compared to B. indicus and B. taurus; after 2 p.m., the creoles vertiginously increase grazing. At the high cover level, the peak of grazing of the Caqueteño Creoles is at 9 a.m. and from 1-1:30 p.m., while at the medium tree cover level, the peak of pasturing was at noon, 1:30 p.m., and 4:30 p.m., at the high tree level of cover, the peak for the three breeds was at 11 a.m. Only at the average tree level of cover did the Caquetaño creoles and B. indicus present a similar peak. In 9-9:30 a.m. and 4-5 p.m., the breeds substantially reduce rumination.


MATERIAL AND METHODS
The Amazon Research Center CIMAZ -MACAGUAL Cesar Augusto Estrada of the University of Amazonia is located 20 km from Florencia, in the south of the Department of Caquetá the Colombian Amazon, at 1º37'N and 75º36'W ( Figure 1). The region is classified as a rainy tropical forest climate region (Af) (KÖPPEN & GEIGER 1938). This region has an average temperature of 25.5º, 3793 mm of annual rainfall, 1707 hours of solar irradiance per year, relative humidity of 84.27%, and an altitude of 250 meters above sea level (SIAT-AC 2018).
Three breeds of cattle from dual-purpose production systems were studied in the dry season (January -March) to establish a behavioral pattern.
The animals with a higher tendency towards the Bos indicus breed are those with more than 50% of genetic ancestry from this breed, particularly Brahman and Gyr. Similarly, the animals that tend towards Bos taurus are those with more than 50% of the breed's genetic material. The Caquetaño Creoles are pure breeds. This study used three animals of each breed.
The paddocks were made up of three levels of scattered tree cover-low (less than 20% of coverage), medium (from 20 to 40%), and high density (more than 40%). The paddocks were covered with Braquiaria decumbens, a more decumbent pasture, with regrowth of 35 days to guarantee homogeneity. Two paddocks were identified for each cover level (two of low, two of medium, and two of high-density), amounting to six paddocks. Before a period of adaptation of two days, the behavior of the animals of the three racial types was evaluated over three days. In the first low-cover paddock, a resting period of seven days was allowed. Later, applying the same time frames, the animals were moved to a paddock with medium cover and, subsequently, to one with high cover. The same procedure was repeated in each level of cover in the second paddocks, where the animals were always pasturing. The methodology determined to evaluate their behavior was adapted from the proposed method by PÉREZ et al. (2008). The observations were made from portable tents located near the paddocks using binocular equipment. The design was carried out at random and the data was analyzed by means of statistical description. To characterize the behavior of the animals, the time dedicated to the activities of pasture, grazing, ruminating, resting, drinking water, defecating, urinating, and shading was quantified. Observations were made during four days of each month of the dry period for eight consecutive hours, from 9 a.m. to 5 p.m. Activity was recorded every ten minutes (Table 1). The formula by PETIT (1972) and PÉREZ et al. (2008) was used to calculate the total time spent in each action dividing the day, where the product of the time dedicated was related to each activity according to the formula: (ai x n)/A Where: "ai" is the number of animals performing the activity, "n" is the time between two successive observations, and "A" is the total number of animals. A descriptive statistics analysis (means and frequencies of the variables) was performed for each one of the ethological variables. In addition, a factorial variance analysis was done, in which the level of tree cover was associated with the breed by the Fisher LSD test (p<0.05) using the R package version 3.2.0 (R DEVELOPMENT CORE TEAM 2013) by means of the independent platform for statistical analysis R Commander (FOX 2005) and InfoStat (DI RIENZO et al. 2015).
In the hours between 12:00 a.m. and 2:00 p.m. for each activity and in each hour, a generalized linear model fitted to a Poisson distribution family was applied and a Tukey HSD adjusted multiple comparison of means test (p-value<0.05) was performed to find statistically significant differences between breeds using the R package version 3.2.0 (R DEVELOPMENT CORE TEAM 2013). Figure 1 shows the behavior of the breeds evaluated. In general, regardless of the breed, the activity performed more often by the animals during the day was pasturing under the sun, and those who perform this activity more often are the Creole Caqueteños, followed by the Bos indicus and, finally, the Bos taurus. Ruminating is the second most important activity performed by the animals, presenting the same tendency.   Table 2 shows how the different activities of the three breeds of cattle evaluated were distributed in time under the three levels of scattered tree cover in the paddocks. It was found that leaf litter consumption, grazing, water consumption, defecating, and urinating are inconsequential. Three large groups of activities are presented: those related to pasturing (SUNP and SHP), to rest (SRS, SHRS, SRL, and SHRL), and to rumination (CCSS, CCSSH, CCSL, and CCSHL), which take up most of the animals' time. In the paddocks with low tree cover, the cattle pasture more under the shade; this tendency is more relevant in the B. taurus. Table 3 shows the three main activities (grazing, rumination and rest). It is highlighted that the Creole bovine cattle are the ones that consume less water, less rest and more time graze. Thus, it shows that the inclemency of the tropics to which less affected the racial types evaluated is the Creole Caqueteños. Figure 2, illustrates the grazing behavior of the three selected racial types evaluated in the three levels of coverage of the trees dispersed in the pasture, finding that the creole bovine cattle show a behavior superior to the B. indicus and the B. taurus. In the midday hours, creoles do not graze less than the other two groups in the high and medium coverage levels. Additionally, when the level of tree cover is low the behavior between the groups of B. indicus and Creole Caqueteños is similar, only that after 14:00, the creoles increase dizzyingly grazing.   In the high coverage level, the grazing peak of the Caqueteños Creoles is at 9 a.m. and between 1 -1:30 p.m., while in the average tree cover level, it was at 12 p.m., 1:30 p.m. and 4:30 p.m.

RESULTS AND DISCUSSION
The behavior of the rumination is very similar in this activity between the groups of Creole Caqueteños and B. indicus, as shown in Figure 3. At the level of high tree cover the peak of the rumination in the three racial types was presented at 11 a.m. In the periods from 9:00 to 9:30 a.m. and from 4:00 p.m. to 5:00 p.m. none of the racial types presented rumination at this level.
At the average coverage level, the Creole cattle and B. indicus showed a peak of rumination at 11 a.m.  Taking into account that the highest temperatures occurred between 12:00 and 2:00 p.m., a greater analysis was carried out to evaluate the effect of the cover and its level of incidence on the three main activities (resting, ruminating and grazing). Graph 4 shows that there were differences in behavior according to Arborea cover. The greatest number of animals resting and ruminating are found in the low tree cover. The highest grazing is found in the high and medium tree cover. The Caqueteño Creoles presented greater grazing in the high and medium cover, always presenting a significant difference (p<0.05) with the crosses where B. taurus predominated. In the low cover, B. indicus grazing was higher, but did not present a significant difference (p>0.05) with the Caqueteños.
Letters adjusted to HSD Tukey test (p-value<0.05). *Equal letters indicate no difference between groups. According to CERQUEIRA et al. (2016), stress is an indicator of adverse environmental conditions for animal welfare. It is difficult to evaluate its magnitude and associated impact on animal production. AGUILAR (2015), suggests that the only way to measure its magnitude is by means of the animals' response, hence the importance of conducting studies of animal behavior under the effects of heat stress generated by the environment.
In the high and medium cover, from 11 a.m. to 1 p.m., the animals reduce pasturing to rest under the canopy of the trees, as this helps them to minimize heat stress caused by the high temperatures. This occurs because, in mammals, the hypothalamic-adrenal-pituitary axis regulates the responses to stress processes SORROZA et al. (2019). According to PHILLIPS (2016), the midday hours mark the peak of environmental heat, and , this generates an physiological disorder. As a result, it increases cortisol levels and raises body temperature, heart rate, and respiratory rate. So, the support of external elements to rebalance physiological functions is needed. According to VEISSIER et al. (2018), the shade of the trees reduces the passage of solar radiation towards the animal's body surface, reducing heat stress.
Considering pasturing on the three selected levels of tree coverage, it was found that at the low level, where few trees are found, the animals of the three breeds pastured more under the shade. According to MAURICIO et al. (2019), the shade generates beneficial effects in animals, such as more pasturing and grazing, allowing greater consumption and selection of food and decreasing water requirements.
The presence of trees encourages pasturing; in paddocks with medium and high tree cover, the activity's frequency and duration is greater than in the paddocks with low cover, as shown in Figure 2.
In the high cover paddocks, the Caqueteño Creoles presented pasturing peaks from 9-9:30 a.m., 1-1:30 p.m., and 4-5 p.m. The B. indicus presented a similar tendency, but with less intensity, and the B. taurus presented low pasturing at a constant level from 9 to 10:30 a.m. and from 3 to 5 p.m.
At the level of low tree cover, the consumption trends were lower than at the other levels. The Caqueteño Creoles presented consumption peaks at 9 a.m. and 11 a.m. and increased their consumption after 2:30 p.m. until 4:30 p.m. The B. indicus presented a similar trend, although with less intensity than the Creoles, and the B. taurus increased their consumption after 3 p.m.
The difference in behavior associated with the breeds, where B. taurus is the least efficient in pasturing, is related to that proposed by VALENTE et al. (2015), that not all bovines have the same comfort temperature range. It is also similar to the trend found by (BRITO et al. 2004), who investigated the effect of stress on B. indicus and B. taurus breeds and found that the B. taurus presented a higher stress index.
The findings on the Caqueteño Creole coincides with GINJA et al. (2019), who states that Latin American Creole cattle adapt to the environment where they evolved, since they can have a unique set of genes for a given environment, which gives them the ability to adapt to the adverse environmental conditions prevailing in the tropical regions and are highly tolerant to high environmental temperatures. Creoles that evolved in warm zones can transfer internal heat to the outside and regulate their body temperature more efficiently than Bos taurus breeds (UNCHUPAICO et al. 2020).
The presence of trees in the pastures helped the animals to spend more time pasturing. According to NAVAS (2008), this is due to the fact that trees reduce caloric stress in cattle, they create microclimates, making the pasture more comfortable, partially block solar radiation and decrease the environmental temperature of their area of influence, allowing the animals to approach their zone of thermoneutrality (PÉREZ et al. 2008) and spend their time in feeding activities.
At the level of high tree cover, the Caqueteño Creole cattle presented rumination peaks at 11 a.m. and low activity in the afternoon. However, no rumination was observed from 9 to 9:30 a.m., 1 to 1:30 p.m. and 4 p.m. to 5 p.m. The B. indicus also presented a peak at the same time, extending until 11:30 a.m., and another peak at 2:30 p.m. This specific breed did not ruminate from 9 to 10 a.m. In turn, the B. taurus presented three peaks with low intensity at 11 a.m., 12:30 a.m., and 2:30 p.m. and did not ruminate from 9:00-10:30 a.m., at 1:30, and from 3:30-5 p.m.
In general terms, tree cover was found to affect animal behavior. The least amount of animals graze in the hours of higher temperature where the cover is low. Due to heat stress, animals reduce feed intake, minimizing endogenous heat production (MARTÍNEZ et al. 2005). Medium and high covers decrease the effects of high temperatures, because the leaves and branches of the trees reduce the passage of solar radiation to the body surface of the animal (VEISSIER et al. 2018), reducing heat stress, so there is higher forage consumption than in low covers (UNCHUPAICO et al. 2020).
The greater grazing of Caqueteño and B. indicus, presenting significant difference (p<0.05) with B. taurus, demonstrates the greater adaptation of the first two. These results are similar to those proposed by (NÚÑEZ et al. 2016), genetically B. indicus have the adaptive capacity to assimilate extreme environmental conditions, while B. taurus do not have the same capacity to withstand high temperatures. However, having evolved in temperate zones, they suffer high levels of heat stress in equatorial or tropical conditions, which modifies their physiology and behavior, decreasing grazing time (LIMA et al. 2020). The adaptation of Creole breeds is due to the fact that these B. taurus animals were brought to America more than 500 years ago, achieving acclimatization (GINJA et al. 2019).

CONCLUSION
Medium and high tree cover had a beneficial effect on the animals, decreasing heat stress in the animals allowing them to increase their voluntary intake, while low tree cover drastically decreased the animals' voluntary intake in the hours of 12 to 2 p.m.
The Caqueteño Creole and those crossed with B. indicus showed similar behavior, while the B. taurus were more affected by the high temperature conditions from 12 to 2 p.m., showing lower feed intake