This review makes an attempt to characterize the physical attributes of heat tolerance, thermal equilibrium and thermal stress thresholds for dairy cows living in tropical environments, with a particular emphasis on pasture-based systems. Under such circumstances, the radiant heat load is the principal climatic factor that determines rates of heat and mass exchanges between cows and the environment. This fact may explain why simple mechanistic models based on air temperature and humidity are not adequately predicting thermal stress thresholds for cattle in tropical regions. To overcome this limitation, the Index of Thermal Stress for Cows (ITSC) and Index for the time spent in shade (ITS), which account for various sources of thermal radiation, were proposed to predict autonomous and behavioral thermoregulation of cows. Overall, the evolutionary adaptation of cattle in tropics favored animals that have cutaneous surface with a skin well protected against penetration of ultraviolet solar radiation (UV), covered by a coat surface with high thermal conductivity. For Holstein breed, although predominantly black animals absorb greater levels of short-wave solar radiation, they may present better protection of skin than white ones. However, dark-colored cows in tropical pastures have potential to absorb as much as 640 W m⁻² of thermal radiation. This amount of heat load would require close to 1,300 g h⁻¹ of cutaneous evaporative water loss through sweating to prevent increases to body temperature, where cows do not have access to shade. Cows are motivated to reduce time spent grazing and to seek shade when solar irradiance exceeds 550 W m⁻², levels that in equatorial latitudes are likely to occur between 08:00 and 16:00h. This information may help producers improve the welfare of cows, as they can determine more comfortable hours for them to graze, for example, by employing nocturnal grazing. Over the daytime, cows should have access to areas with shade and this could include shade provided via solar panels, which has the potential to improve thermal comfort and sustainability of dairy production in tropical areas.

The objective of this study was to evaluate the seasonal and daily variation in sexual behavior of Morada Nova breeders raised in the Brazilian semi-arid region. The data were collected from four rams and 114 ewes of the Morada Nova breed - 55 females in the dry season and another 59 in the rainy season. Observations were performed in the dry and rainy seasons, divided into four times of the day: morning (05:01 h to 11.00 h), afternoon (11.01 h to 17.00 h), evening (17.01 h to 23:00 h), and dawn (23:01 h to 05.00 h). Sexual behavior was assessed for a period of 24 h/day, in a breeding season. One ram was used each three days. The behavioral patterns of the rams in view of females were observed during the recognition (sniffing the female urine, bouts of anogenital sniffing, and flehmen reaction), preparatory (exposure of tongue and penis, leg-kicking, and low-pitched bleats), and copulatory (number of mounts, number of ejaculations, and refractory period) phases. The rams were more active during daytime. The animals in the rainy season showed more efficient sexual behaviors by the lower frequency of mounts per ejaculation and greater number of ejaculations in a shorter time. In contrast, courting behaviors such as exposure of tongue, number of mounts, low-pitched bleats, and leg-kicking were more frequent in the dry season. In the semi-arid region with latitudes close to 7°N, Morada Nova rams have a higher intensity of precopulatory behaviors and lower frequency of ejaculations in the dry season.

Different types of supplied roughage may cause losses in the chemical composition and digestibility of gliricidia (Gliricidia sepium [Jacq.] Kunth ex Walp.) depending on their making and fed-out management. This study has summarized data from scientific studies on gliricidia and compared its nutritional value in various fed forms using a systematic review approach and principal component analysis (PCA). A robust survey of scientific papers was realized on web indexes of periodicals and databases from 1990 to 2023. Data from 100 scientific researches has been compiled and analyzed. In 40% of the trials, the gliricidia nutritional value was determined as fresh leaves, while 30% was in the form of ‘leaves + thin stems’. Gliricidia was evaluated as silage in 11% of the opportunities, followed by 10% as leaf meal and 9% as hay. Non-fiber carbohydrates, crude protein (CP), and organic matter digestibility (OM) had negative correlations with neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin. Only NDF, ADF, and CP contents could explain 71% of the total data variation (PC1 and PC2). There was no discrimination among fed forms, so they showed similar nutrient compositions. Eventual nutrient losses reported in the scientific researches owing to ensilage, haymaking, and leaf meal-making processes do not mischaracterize the gliricidia nutritional value. The assorted manners of roughage making, and fed-out management traditionally performed by farmers can conserve the excellent nutritional quality of gliricidia.

The welfare of dairy cows is a major global concern, due to its impact on cow health and productivity, as well as public health. The aim of this study was to identify the main problems related to welfare in dairy herds managed on pasture in the state of Paraíba, Brazil. For this investigation, a cross-sectional study was conducted in 12 dairy farms in the municipalities of Areia, Alagoa Grande, Serraria, and Pilões, Paraíba, Brazil. Each farm was visited only once, recording the number of cows in the herd, type and number of milkings per day, daily milk yield, and access time to the pasture. Body condition score, cleanliness score, bodily injuries, and qualitative behavioral assessment (QBA) were measured. A total of 335 dairy cows were evaluated; herds ranged from 14 to 43 lactating cows, with an average milk yield of 8.4 ± 3.25 kg day-1. Of the 335 cows observed, 26% had a low body condition score, 82% had bodily injuries, and 20% had dirt on their legs. For the QBA, a principal component analysis (PCA) indicated that PC1 had a high correlation mainly with positive body expressions (e.g., sociable, active, and happy), and PC2 was associated with negative terms of body expression (e.g., apathetic, frustrated, and fearful). In conclusion, evaluating indicators of cows’ body condition, bodily injury, and cleanliness highlighted the importance of promoting improvements in pasture, management, and housing conditions to enable better performance, health, and welfare of the animals.

Tannins have been used to trigger positive effects on ruminal metabolism and increase ruminant production efficiency, since they increase the supply of dietary protein in the small intestine. Increasing levels of tannic acid in a sorghum-based diet on the feeding behavior of five Holstein/Zebu crossbred lactating dairy cows was evaluated. They were subjected to a 5 × 5 Latin square experimental design, with fivelevels of tannin as dry matter (DM) in the diet (0.46, 1.30, 2.60, 3.90, and 5.20%). The levels of the tannic acid added were established based on the quantity of condensed tannin in high-tannin sorghum. Thus, diets 2, 3, 4 and 5 were supplemented with 1.5 g (13% DM), 79.5 g (2.6% DM), 157.5 g (3.9% DM), and 235.5 g (5.2% DM) of tannic acid, totaling 0.078, 0.156, 0.234, and 0.321 kg of tannin/day, respectively. Feeding behavior variables included the following states and events: feeding, drinking, rumination, and inactivity; the frequency of visiting the feed and water troughs; and the occurrence of urination and defecation. Water was provided ad libitum, and its intake was measured during periods of behavioral data collection. The use of two tannin sources (hydrolysable and condensed) corresponding to the total level of 5.20% (on a DM basis) in the diet of lactating dairy cattle does not affect the animals’ health. Tannic acid can be included in the diet of lactating dairy cattle at a level of 3.93% (on a DM basis) without inducing variation in the total time spent daily on feed intake. Dairy cows dilute the effects of dietary tannin (5.20%) through greater fragmentation of food consumption in the hours following its supply (180 min). The astringent effects caused by tannin intake in lactating dairy cows are mitigated by increasing the daily water intake as the amount of tannin in the diet increases, starting at a level of 3.90% tannin (on a DM basis).