Little is known about the effects of heat stress during the late gestation period on lactation in dairy goats. For this reason, 32 Saanen goats were randomly assigned to 1 of 2 groups, control (CT; n = 16) or heat stress (HS; n = 16), during late gestation. The HS goats were housed in a climatic chamber before parturition and subjected to heat stress for the last 45 d. After parturition, the HS goats were housed in the same conditions as the CT group. Mammary gland biopsies were performed on 7 goats per treatment at −30, −15, 15, and 30 d relative to parturition, so that the expression levels of several genes could be determined. The HS goats produced less milk than the CT goats did during the first half of lactation, but not during the rest of lactation. Before parturition, apoptosis-related transcripts (TP53 and BAX) were higher in the mammary glands of the HS goats than in those of the CT goats. The HS goats also had higher levels of HSPB1 gene expression during gestation and lactation. However, expression of the prolactin receptor gene was lower after parturition in the mammary glands of HS, suggesting downregulation of prolactin signaling. In summary, heat stress during final gestation reduces milk yield in the subsequent lactation. Although the upregulation of apoptosis signaling in the HS goats suggests that heat stress affects mammary cell number, the loss of the effect on milk production is more compatible with an effect on cell activity, which could be due to a downregulation of prolactin signaling.

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.

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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.

The hematopoietic system changes during the pregnancy to carry fetal development and maternal needs. This study compared the hematological parameters between ewes with single and twin pregnancies during gestation, delivery, and postpartum. The experiment was conducted on 60 healthy pregnant Dorper ewes that were divided into two experimental groups: Group 1 (G1), with single pregnancies (n=30), and Group 2 (G2), with twin pregnancies (n=30). Blood samples were collected from all ewes at different times: immediately before fixed-time artificial insemination (AI); on day 30, 90, 120, 130, and 140 of pregnancy; immediately after delivery; and at 24h and 48h postpartum. Statistical analysis compared the two groups at different times (P<0.05). Mild, normocytic, and hypochromic anemia was detected in all ewes from AI time and throughout pregnancy from both groups, but did not prove to be of clinical relevance. In the peripartum stage (from the 140th day of pregnancy to 48h postpartum), the ewes with twin pregnancies (G2) exhibited higher erythrogram values and neutrophil:lymphocyte ratio than did ewes with single pregnancies (G1). This indicated a greater hematopoietic adaptation in the body during the development of two fetuses. Except for the eosinophil numbers, all leukogram parameters were influenced by pregnancy in a similar way in both groups, and was characterized mainly by leukocytosis with neutrophilia during peripartum due to the high presence of endogenous cortisol at delivery. Thus, these findings showed that pregnancy was a stressful physiological event that increased the leukocyte count with a slight alteration in the erythrogram of Dorper ewes.

Avaliou-se o conforto térmico de vacas leiteiras mestiças, anteriormente à inseminação artificial, e a relação com a taxa de concepção. Este estudo foi realizado em Uberlândia, Minas Gerais, região caracterizada por invernos secos e verões chuvosos, utilizando 112 vacas leiteiras mestiças, cuja composição genética envolvia as raças Holandesa, Gir, Jersey e Pardo Suíça. Os parâmetros fisiológicos, frequência respiratória e temperatura retal foram mensurados previamente à inseminação artificial, juntamente com os parâmetros ambientais,  temperatura, umidade do ar e velocidade do vento. A temperaturamínima e a umidade relativa foram maiores no verão do que no inverno. Já a amplitude térmica foi menor no verão em relação ao inverno (p ˂ 0,05). As temperaturas média e máxima do ar, ITU (índice de temperatura e umidade) e ITE (índice de temperatura equivalente) não diferiram entre as estações (p ˃ 0,05). Observou-se uma tendênciade maior taxa de concepção quando as inseminações foram realizadas no ITU ≤ 72 (p = 0,06). Conclui-se que o momento em que foram realizadas as inseminações artificiais contribuiu para que os animais estivessem em  conforto térmico e, portanto, não foi observado prejuízo na taxa de concepção das vacas leiteiras mestiças.

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