Accurately quantifying activated immune system energy requirements in vivo is difficult, but a better understanding may advance strategies to maximize animal productivity. Study objectives were to estimate whole-body glucose utilization following an i.v. endotoxin challenge. Lactating Holstein cows were jugular catheterized and assigned 1 of 3 bolus treatments: control (CON; 5 mL of saline; n = 6), lipopolysaccharide (LPS)-administered (LPS-C; 1.5 μg/kg of body weight; Escherichia coli 055:B5; n = 6), and LPS + euglycemic clamp (LPS-Eu; 1.5 μg/kg of body weight; 50% glucose solution infusion; n = 6). After LPS administration, blood glucose was determined every 10 min and glucose infusion rates were adjusted in LPS-Eu cows to maintain euglycemia for 720 min. Blood samples were obtained 180, 360, 540, and 720 min postbolus for further analysis. Cows were milked 360 and 720 min postbolus. Blood glucose was increased 84% in LPS-administered cows for up to 150 min postbolus; thereafter, circulating glucose was decreased 30% in LPS-C relative to LPS-Eu and CON cows. Mild hyperthermia (+0.5°C) occurred between 30 and 90 min postbolus in LPS-administered relative to CON cows; thereafter, rectal temperature did not differ between treatments. Milk yield and lactose percentage were decreased 80 and 11%, respectively, in LPS-administered relative to CON cows. Circulating insulin was increased 4 fold and nonesterified fatty acids, β-hydroxybutyrate, and ionized Ca were decreased ∼50% in LPS-administered compared with CON cows. Plasma l-lactate, haptoglobin, and serum amyloid A increased ∼160, 260, and 75%, respectively, in LPS-administered relative to CON cows. Overall, LPS-binding protein was increased 87% in LPS-administered relative to CON cows; however, at 720 min, it was decreased 25% in LPS-Eu compared with LPS-C cows. White blood cell count decreased ∼90% in LPS-administered cows at 180 min and progressively increased to ∼50% of CON values by 720 min. Total glucose deficit during the 720 min following LPS administration was calculated as the decrease in the amount of glucose required to synthesize milk (due to the decrease in milk yield relative to prebolus levels) plus the amount of glucose infused to maintain euglycemia (in LPS-Eu cows only) and was 461, 1,259, and 1,553 g for CON, LPS-C, and LPS-Eu cows, respectively. Our data indicate an acutely activated immune system uses >1 kg of glucose within 720 min and maintaining euglycemia did not rescue milk synthesis.

Heat stress (HS) decreases milk protein synthesis beyond what would be expected based on the concomitant reduction in feed intake. The aim of the present study was to evaluate the direct effects of HS on milk protein production. Four multiparous, lactating Holstein cows (101 ± 10 d in milk, 574 ± 36 kg of body weight, 38 ± 2 kg of milk/d) were individually housed in environmental chambers and randomly allocated to 1 of 2 groups in a crossover design. The study was divided into 2 periods with 2 identical experimental phases (control phase and trial phase) within each period. During phase 1 or control phase (9 d), all cows were housed in thermal neutral conditions (TN; 20°C, 55% humidity) and fed ad libitum. During phase 2 or treatment phase (9 d), group 1 was exposed to cyclical HS conditions (32 to 36°C, 40% humidity) and fed ad libitum, whereas group 2 remained in TN conditions but was pair-fed (PFTN) to their HS counterparts to eliminate the confounding effects of dissimilar feed intake. After a 30-d washout period in TN conditions, the study was repeated (period 2), inverting the environmental treatments of the groups relative to period 1: group 2 was exposed to HS and group 1 to PFTN conditions. Compared with PFTN conditions, HS decreased milk yield (17.0%), milk protein (4.1%), milk protein yield (19%), 4% fat-corrected milk (23%), and fat yield (19%). Apparent digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, crude protein, and ether extract was increased (11.1-42.9%) in HS cows, as well as rumen liquor ammonia (before feeding 33.2%; after feeding 29.5%) and volatile fatty acid concentration (45.3%) before feeding. In addition, ruminal pH was reduced (9.5 and 6% before and after feeding, respectively) during HS. Heat stress decreased plasma free amino acids (AA; 17.1%) and tended to increase and increased blood, urine, and milk urea nitrogen (17.2, 243, and 24.5%, respectively). Further, HS cows had reduced plasma glucose (8%) and nonesterified fatty acid (39.8%) concentrations compared with PFTN controls. These data suggest that HS increases systemic AA utilization (e.g., decreased plasma AA and increased nitrogen excretion), a scenario that limits the AA supply to the mammary gland for milk protein synthesis. Furthermore, the increase in AA requirements during HS might represent the increased need for gluconeogenic precursors, as HS is thought to prioritize glucose utilization as a fuel at the expense of nonesterified fatty acids.

Acute heat stress (HS) and heat stroke can be detrimental to the health, well-being, and performance of mammals such as swine. Therefore, our objective was to chronologically characterize how a growing pig perceives and initially copes with a severe heat load. Crossbred gilts (n=32; 63.8±2.9 kg) were subjected to HS conditions (37°C and 40% humidity) with ad libitum intake for 0, 2, 4, or 6 h (n=8/time point). Rectal temperature (Tr), respiration rates (RR), and feed intake were determined every 2 h. Pigs were euthanized at each time point and fresh ileum and colon samples were mounted into modified Ussing chambers to assess ex vivo intestinal integrity and function. Transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran (FD4) permeability were assessed. As expected, Tr increased linearly over time (P<0.001) with the highest temperature observed at 6 h of HS. Compared to the 0-h thermal-neutral (TN) pigs, RR increased (230%; P<0.001) in the first 2 h and remained elevated over the 6 h of HS (P<0.05). Feed intake was dramatically reduced due to HS and this corresponded with significant changes in plasma glucose, ghrelin, and glucose-dependent insulinotropic peptide (P<0.050). At as early as 2 h of HS, ileum TER linearly decreased (P<0.01), while FD4 linearly increased with time (P<0.05). Colon TER and FD4 changed due to HS in quadratic responses over time (P=0.050) similar to the ileum but were less pronounced. In response to HS, ileum and colon heat shock protein (HSP) 70 mRNA and protein abundance increased linearly over time (P<0.050). Altogether, these data indicated that a short duration of HS (2-6 h) compromised feed intake and intestinal integrity in growing pigs. KeywordsAnimal Science, appetite, heat stress, intestinal integrity, swine ABSTRACT: Acute heat stress (HS) and heat stroke can be detrimental to the health, well-being, and performance of mammals such as swine. Therefore, our objective was to chronologically characterize how a growing pig perceives and initially copes with a severe heat load. Crossbred gilts (n = 32; 63.8 ± 2.9 kg) were subjected to HS conditions (37°C and 40% humidity) with ad libitum intake for 0, 2, 4, or 6 h (n = 8/time point). Rectal temperature (T r ), respiration rates (RR), and feed intake were determined every 2 h. Pigs were euthanized at each time point and fresh ileum and colon samples were mounted into modified Ussing chambers to assess ex vivo intestinal integrity and function. Transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran (FD4) permeability were assessed. As expected, T r increased linearly over time (P < 0.001) with the highest temperature observed at 6 h of HS. Compared to the 0-h thermal-neutral (TN) pigs, RR increased (230%; P < 0.001) in the first 2 h and remained elevated over the 6 h of HS (P < 0.05). Feed intake was dramatically reduced due to HS and this corresponded with significant changes in plasma glucose, ghrelin, and glucose-dependent insulinotropic peptide (P < ...

Peroxisomes are highly dynamic and metabolically active organelles that play an important role in cellular functions, including reactive oxygen species (ROS) metabolism. Peroxisomal dynamics, such as the proliferation, movement, and production of dynamic extensions called peroxules, have been associated with ROS in plant cells. However, the function and regulation of peroxules are largely unknown. Using confocal microscopy, we have shown that treatment of Arabidopsis leaves with the heavy metal cadmium produces time course-dependent changes in peroxisomal dynamics, starting with peroxule formation, followed by peroxisome proliferation, and finally returning to the normal morphology and number. These changes during Cd treatment were regulated by NADPH oxidase (C and F)-related ROS production. Peroxule formation is a general response to stimuli such as arsenic and is regulated by peroxin 11a (PEX11a), as Arabidopsis pex11a RNA i lines are unable to produce peroxules under stress conditions. The pex11a line showed higher levels of lipid peroxidation content and lower expression of genes involved in antioxidative defenses and signaling, suggesting that these extensions are involved in regulating ROS accumulation and ROSdependent gene expression in response to stress. Our results demonstrate that PEX11a and peroxule formation play a key role in regulating stress perception and fast cell responses to environmental cues.Peroxisomes are highly versatile organelles that adapt to changes in their cellular environment through morphological and metabolic adjustments (Hu et al., 2012;Sandalio et al., 2013). Plant peroxisomes perform essential functions such as photorespiration and fatty acid b-oxidation, ureide, and phytohormone (auxin and jasmonic acid) metabolisms, and also act as a source of signal molecules such as reactive oxygen and nitrogen species (ROS and RNS; Sandalio and RomeroPuertas, 2015). Peroxisomes contain a large battery of antioxidants to control ROS and RNS accumulation (Sandalio and Romero-Puertas, 2015). These organelles proliferate in response to environmental cues through a complex process involving elongation, constriction, and fission (Hu et al., 2012;Baker and Paudyal, 2014). Deciphering the signaling pathways governing the regulation of peroxisome proliferation under different environmental and metabolic conditions presents a major challenge in this field of research. Before peroxisomal division, organelle elongation occurs in a process regulated by peroxins 11 (PEX11), with the final division requiring dynamin-like or dynamin-related proteins and fission proteins (Hu et al., 2012, Schrader et al., 2012. There is evidence to suggest that ROS are involved in regulating peroxisome proliferation, as some peroxisomal biogenesis genes (PEX) are transcriptionally regulated by H 2 O 2 in both plant and animal cells (López-Huertas et al., 2000). The formation of peroxisomal extensions, known as peroxules, has also been observed to be regulated by exogenous applications of H 2 O 2 (Sinclair et al., 2009;Ba...

Heat stress (HS) jeopardizes human and animal health and reduces animal agriculture productivity; however, its pathophysiology is not well understood. Study objectives were to evaluate the direct effects of HS on carbohydrate and lipid metabolism. Female pigs (57 ± 5 kg body weight) were subjected to two experimental periods. During period 1, all pigs remained in thermoneutral conditions (TN; 20°C) and were ad libitum fed. During period 2, pigs were exposed to: (1) constant HS conditions (32°C) and fed ad libitum (n = 7), or (2) TN conditions and pair-fed (PFTN; n = 10) to minimize the confounding effects of dissimilar feed intake. All pigs received an intravenous glucose tolerance test (GTT) and an epinephrine challenge (EC) in period 1, and during the early and late phases of period 2. After 8 days of environmental exposure, all pigs were killed and tissue samples were collected. Despite a similar reduction in feed intake (39%), HS pigs tended to have decreased circulating nonesterified fatty acids (NEFA; 20%) and a blunted NEFA response (71%) to the EC compared to PFTN pigs. During early exposure, HS increased basal circulating C-peptide (55%) and decreased the insulinogenic index (45%) in response to the GTT. Heat-stressed pigs had a reduced T3 to T4 ratio (56%) and hepatic 5′-deiodinase activity (58%). After 8 days, HS decreased or tended to decrease the expression of genes involved in oxidative phosphorylation in liver and skeletal muscle, and ATGL in adipose tissue. In summary, HS markedly alters both lipid and carbohydrate metabolism independently of nutrient intake.