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Study objectives were to characterize the effects of citrulline (CIT) on physiological and intestinal morphology metrics during heat stress (HS) and feed restriction. Forty crossbred gilts (30 ± 2 kg body weight [BW]) were assigned to one of five treatments: (1) thermoneutral (TN) fed ad libitum (AL) with control (CON) supplement (TNAL; n  = 8), (2) TN pair-fed (PF) with CON (PF-CON; n  = 8), (3) TN PF with CIT (PF-CIT; n  = 8), (4) HS AL with CON (HS-CON; n  = 8), and (5) HS AL with CIT (HS-CIT; n  = 8). During the period (P) 1 (7 d), pigs were in TN conditions (23.6 °C) and fed AL their respective supplemental treatments. During P2 (2.5 d), HS-CON and HS-CIT pigs were fed AL and exposed to cyclical HS (33.6 to 38.3 °C), while TNAL, PF-CON, and PF-CIT remained in TN and were fed either AL or PF to their HS counterparts. Citrulline (0.13 g/kg BW) was orally administered twice daily during P1 and P2. HS increased rectal temperature (Tr), skin temperature (Ts), and respiration rate (RR) relative to TN pigs (0.8 °C, 4.7 °C, and 47 breaths/min, respectively; P  < 0.01). However, HS-CIT had decreased RR (7 breaths/min, P  = 0.04) and a tendency for decreased Tr (0.1 °C, P  = 0.07) relative to HS-CON pigs. During P2, HS pigs had decreased feed intake (22%; P  < 0.01) and a tendency for decreased average daily gain (P  = 0.08) relative to TNAL pigs, and by experimental design, PF pigs followed this same pattern. Circulating lipopolysaccharide-binding protein tended to be decreased (29%; P  = 0.08) in PF relative to TNAL pigs and was increased (41%; P  = 0.03) in HS compared to PF pigs. Jejunum villus height was decreased in PF relative to TNAL pigs (15%; P  = 0.03); however, CIT supplementation improved this metric during feed restriction (16%; P  = 0.10). Jejunum mucosal surface area decreased in PF (16%; P  = 0.02) and tended to decrease in HS (11%; P  = 0.10) compared to TNAL pigs. Ileum villus height and mucosal surface area decreased in HS compared to TNAL pigs (10 and 14%, respectively; P  ≤ 0.04), but both parameters were rescued by CIT supplementation (P  ≤ 0.08). Intestinal myeloperoxidase and goblet cell area remained similar among treatments and intestinal segments (P  > 0.24). In summary, CIT supplementation slightly improved RR and Tr during HS. Feed restriction and HS differentially affected jejunum and ileum morphology and while CIT ameliorated some of these effects, the benefit appeared dependent on intestinal section and stressor type. [ABSTRACT FROM AUTHOR]

Study objectives were to determine the effects of chromium (Cr) propionate (Cr propionate 0.04%; 0.5 g/kg of feed to deliver 200 parts per billion Cr/d; KemTRACE Cr, Kemin Industries, Inc. Des Moines, IA) on growth performance, metabolism, and health biomarkers in heat-stressed and nutrient-restricted pigs. Crossbred barrows (n = 96; 105 ± 1 kg BW) were enlisted in an experiment conducted in two replicates, blocked by initial BW, and randomly assigned to one of six dietary-environmental treatments: (i) thermoneutral (TN) and fed ad libitum a control diet (TNCtl), (ii) TN and fed ad libitum a Cr supplemented diet (TNCr), (iii) TN and pair-fed a control diet (PFCtl), (iv) TN and pair-fed a Cr supplemented diet (PFCr), (v) heat stress (HS) and ad libitum fed a control diet (HSCtl), or (vi) HS and ad libitum fed a Cr supplemented diet (HSCr). The study consisted of three experimental periods (P). During P0 (5 d), all pigs were housed in TN conditions (21.3 ± 0.1 °C, 56.8 ± 0.3% relative humidity [ RH ]) and fed the control diet ad libitum. During P1 (5 d), pigs were fed their respective dietary treatments ad libitum and kept in TN conditions. During P2 (35 d), HSCtl and HSCr-treated pigs were fed ad libitum and exposed to progressive cyclical HS conditions (27 to 31 °C, 50 ± 0.3% RH), while TNCtl, TNCr, PFCtl, and PFCr pigs remained in TN conditions and were fed ad libitum or pair-fed to their respective HSCtl and HSCr counterparts to eliminate the confounding effects of dissimilar feed intake. Overall, HS pigs had increased (P < 0.01) rectal temperature, skin temperature, and respiration rate (0.3 °C, 3.8 °C, and 32 breaths per minute, respectively) relative to TN pigs. Overall, HS decreased ADFI and ADG (20 and 21%, respectively; P < 0.01) compared with TN controls. Final BW tended to be increased in HSCr (2.7 kg, P = 0.06) compared with HSCtl pigs. Similarly, ADG tended to be increased during P2 in HSCr relative to HSCtl-treatment (0.77 vs. 0.72 kg/d; P = 0.10). There were no effects of Cr on most production parameters, but ADFI tended to be increased in Cr relative to Ctl-fed pigs (3.19 vs. 3.09 kg/d; P = 0.08). No effects of Cr supplementation were detected on circulating glucose, insulin, NEFA, cholesterol, triglycerides, or lipopolysaccharide binding protein. However, blood neutrophils were increased in HSCr (37%; P < 0.01) relative to HSCtl pigs. In summary, these results suggest Cr supplementation may benefit growth performance during HS. [ABSTRACT FROM AUTHOR]

Heat stress (HS) jeopardizes animal productivity and health. The intestinal barrier is sensitive to HS and heat-induced hyperpermeability plays a key role in its pathophysiology. However, the biology of recovery following HS is less understood. Thus, study objectives were to determine the temporal pattern of metabolic, inflammatory, and intestinal histological parameters during HS recovery. Female pigs (n = 32; 19.5 ± 0.5 kg BW) were sacrificed following exposure to 1 of 4 environmental treatments: 1) constant thermoneutral (TN) conditions (TNC; 24.2 ± 0.5°C), 2) no TN recovery post HS (0D), 3) 3 d of TN recovery post HS (3D), and 4) 7 d of TN recovery post HS (7D). The HS protocol was cyclical (33.6 ± 1.8 to 37.4 ± 2.1°C) and lasted for 3 d for all HS treatments. During the 3 d of HS, rectal temperature, skin temperature, and respiration rates were increased (1.3°C, 4.8°C, and 77 breaths/min, respectively; P < 0.01) and ADFI was decreased (27%; P < 0.01) compared to TNC pigs. Skin temperature tended to be decreased 0.6°C in 3D pigs during days 1–3 of recovery (P = 0.06) and was decreased 1.6 and 0.7°C during days 1–3 and 4–7 of recovery, respectively, in 7D pigs (P ≤ 0.03) compared to TNC. Relative to TNC pigs, ADFI remained 14% decreased during days 1–3 of recovery in both 3D and 7D pigs, and 17% decreased during days 4–7 in 7D pigs (P ≤ 0.01). Plasma glucose was decreased (10%; P = 0.03) for 0D and 3D relative to TNC pigs. Circulating lipopolysaccharide-binding protein was increased in 3D and 7D vs. TNC pigs (110 and 147%, respectively; P = 0.01) and tended to increase linearly with increasing recovery time (P = 0.08). Circulating tumor necrosis factor alpha was decreased (15%) in 0D pigs and increased linearly with advancing recovery time (P < 0.01). Jejunum and ileum villus height were reduced 17 and 11% in 0D vs. TNC pigs and increased linearly with progressive recovery time (P < 0.01). Jejunum and ileum mucosal surface areas were reduced 17 and 9% in 0D pigs and remained decreased in the jejunum while the ileum recovered to TNC levels by day 3 of recovery. Relative to TNC pigs, goblet cell area was similar in jejunum and colon of 0D pigs but was reduced in the ileum of 0D pigs and in jejunum, ileum, and colon of 3D and 7D relative to TNC pigs (P < 0.01). In summary, HS has deleterious effects on intestinal morphology that seem to improve with recovery time. In contrast, feed consumption remained suppressed and inflammatory biomarkers indicative of leaky gut increased following the heat load. [ABSTRACT FROM AUTHOR]

The intestinal epithelium has two critical roles: nutrient absorption and protection against numerous pathogens and antigens present in the gastrointestinal tract (GIT). The GIT is thought to be the evolutionary developmental site of the original immune system which later progressed into adding more specialized tissues. The GIT contains an enormous surface area to defend against invading pathogens and contains the majority of the body's immune cells. Poor gut health can be caused by a variety of stressors, and ruminant research has characterized the negative impacts of rumen acidosis, heat stress, and feed restriction (FR) on lower gut health. Recently, FR has been utilized as a model to study negative consequences of GIT health and strategies to ameliorate it. The mechanism by which FR causes barrier dysfunction is not known but could be due to a lack of luminal nutrients or associated psychological stress. If stress causes GIT health to be compromised to the point where pathogens/antigens cross into the host animal and if the insult is severe enough, systemic inflammation can ensue. Inflammation is energetically costly, in part because activated immune cells have a preferential appetite for glucose. Inflammation also alters basal and stimulated metabolism, likely to help support glucose sparing for immune system use. This is extremely costly to the producer, as an animal must mobilize valuable skeletal muscle stores or compromise milk (lactose) production to ensure adequate glucose for survival. In an intensely activated immune system, it has been estimated that ~1.0 g glucose / kg BW0.75 / hour is utilized to mount a response. Therefore, it is important for producers to minimize stresses known to compromise gut integrity and for nutritionists and allied industry personnel to understand and utilize nutritional strategies and interventions to protect GIT health. [ABSTRACT FROM AUTHOR]