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The production of beef cattle in the Atlantic Forest biome mostly takes place in pastoral production systems. There are millions of hectares covered with pastures in this biome, including degraded pasture (DP), and only small area of the original Atlantic Forest has been preserved in tropics, implying that actions must be taken by the livestock sector to improve sustainability. Intensification makes it possible to produce the same amount, or more beef, in a smaller area; however, the environmental impacts must be assessed. Regarding climate change, the C dynamics is essential to define which beef cattle systems are sustainable. The objectives of this study were to investigate the C balance (t CO2e./ha per year), the intensity of C emission (kg CO2e./kg BW or carcass) and the C footprint (t CO2e./ha per year) of pasture-based beef cattle production systems, inside the farm gate and considering the inputs. The results were used to calculate the number of trees to be planted in beef cattle production systems to mitigate greenhouse gas (GHG) emissions. The GHG emission and C balance, for 2 years, were calculated based on the global warming potential (GWP) of AR4 and GWP of AR5. Forty-eight steers were allotted to four grazing systems: DP, irrigated high stocking rate pasture (IHS), rainfed high stocking rate pasture (RHS) and rainfed medium stocking rate pasture (RMS). The rainfed systems (RHS and RMS) presented the lowest C footprints (−1.22 and 0.45 t CO2e./ha per year, respectively), with C credits to RMS when using the GWP of AR4. The IHS system showed less favorable results for C footprint (−15.71 t CO2e./ha per year), but results were better when emissions were expressed in relation to the annual BW gain (−10.21 kg CO2e./kg BW) because of its higher yield. Although the DP system had an intermediate result for C footprint (−6.23 t CO2e./ha per year), the result was the worst (−30.21 CO2e./kg BW) when the index was expressed in relation to the annual BW gain, because in addition to GHG emissions from the animals in the system there were also losses in the annual rate of C sequestration. Notably, the intensification in pasture management had a land-saving effect (3.63 ha for IHS, 1.90 for RHS and 1.19 for RMS), contributing to the preservation of the tropical forest.

Adaptation is a relevant characteristic to be understood in livestock animals in order to maintain and raise productivity. In Brazil, the Nellore beef cattle are widely disseminated and well-adapted breed that present good thermoregulatory characteristics for tropical environment conditions. Conversely, the physiological and cellular mechanisms required for thermoregulation and thermotolerance in this breed are still limited. The aim of this study was to comprehend the heat loss efficiency at the whole animal level and heat shock response at the cellular level of Nellore cows in tropical climate conditions. Healthy purebred Nellore cows were classified according to their capacity to lose body heat as Efficient or Inefficient based on vaginal temperature which was continuously monitored by data-loggers. Rectal, tail, and ocular temperatures, sweating rate, and respiratory frequency were collected to assess other thermoregulatory responses. Peripheral mononuclear cells were used for gene expression of heat shock proteins 60, 70, and 90 induced by in vitro heat treatments at 38, 40, and 42 °C. In our findings, the Efficient cows presented higher sweating rates compared to Inefficient cows that presented higher rectal temperature with greater amplitude of vaginal temperature profile. Transcription of the HSP genes was stable at 38 and 40 °C and decreased for all HSP genes at 42 °C. In conclusion, the Nellore efficiency to lose heat was mainly associated with their sweating capacity and cellular thermotolerance confirmed by the maintenance of heat shock proteins transcripts under heat stress. Taken together, this knowledge contributes as a future key for genetic selection of adapted animals.

Physiological and productive responses were studied in five Holstein cows in thermal comfort (T1), stress by exogenous adrenocorticotropic hormone (ACTH) administration (T2) and heat stress (T3) to compare acute and punctual stress (ACTH) and prolonged stress (heat stress). During T1 and T2, cows were housed in a climatic-free stall barn. In T3, the animals were kept in a climatic room (air temperature of 37°C from 08:00 to 13:00 h, and of 26°C from 14:00 to 07:00 h) for 7 days. Milk yield, rectal temperature (RT), respiratory rate (RR) and blood samples were obtained before, during and after all treatments. In T1 at 08:00 h, RT and RR were below the upper critical limit. Simultaneously, cortisol and insulin growth-factor I (IGF-I) were within the normal limits. After ACTH administration (T2), cortisol significantly increased, reaching maximum levels at 60 min and returning to basal levels at 300 min. However, IGF-I was not affected. During T3, Holstein cows did not effectively dissipate their body temperature and RT, RR and cortisol significantly increased. There was a 26.6% reduction in milk production after heat stress (P < .05). Prolonged heat stress was more stressful and cows had higher levels of CORT in T3 than in T2 even before the increase in body temperature. Although the total amount of cortisol and IGF-I presented a negative and significant Pearson correlation (r = −0.79), IGF-I was not significantly influenced by heat stress or ACTH administration, and the relationship between IGF-I and heat stress remains controversial. ARTICLE HISTORY

A B S T R A C TStress during pregnancy negatively affects fetal development, and artificial weaning can negatively affect animal health and welfare; however, maternal care can reverse the possible consequences of stress on the offspring. Our study aims to determine the combined effect of a prenatal disease challenge and artificial weaning on welfare and productive performance of lambs. During pregnancy, 43 ewes were distributed into three experimental groups, and at 70th and 120th days of pregnancy (Ig;n = 14; Fg = 14;), the ewes were administered with Escherichia coli Lipopolysaccharides (LPS). Fifteen ewes were included in the control group (Cg = 15). Cortisol and rectal temperature measurements were done subsequently to LPS or saline injection. Fourty-six lambs (21 males; 25 females) born in a six-day interval from Ig, Fg, and Cg ewes were subjected to two types of weaning, namely progressive (from 39 to 45 days) and abrupt (at 45 days of age). Lamb data, including plasma cortisol levels, rectal temperature, weaning weight, and performance in feedlot were analyzed and compared through F test and Student's t-test (PDIFF; P = 0.05). The injection of LPS resulted in a 619% increase in cortisol levels after two hours, and rectal temperature reached 39.48 ± 0.134°C after four hours of LPS administration in a pregnant sheep. Both male and female lambs from the Fg group had lower birth weight (P < 0.05) as compared to other groups. Cortisol levels and rectal temperature decreased during progressive weaning (P < 0.05), in which a higher weaning weight was observed than in abrupt weaning (P < 0.05). On the first day at feedlot, cortisol level was reduced after 60 min upon entrance (P < 0.05), and higher cortisol values were observed during abrupt weaning (P < 0.05). Lower values of dry mater intake and average daily gain were observed for Fg males (P < 0.05). LPS challenge during late pregnancy compromised the lambs' indicators of productive performance. Albeit progressive weaning was less stressful during feedlot entrance and total bond separation, more days of maternal care during weaning had no relation with stress during pregnancy.