Dietary supplementation of artificial sweetener and capsicum oleoresin as a strategy to mitigate the negative consequences of heat stress on pig performance.

Pigs exposed to elevated ambient temperatures exhibit reduced daily gain, alterations in muscle and fat deposition, and decreased health. Negative aspects of gastrointestinal (GI) function, integrity, and permeability also occur. High-intensity sweeteners can ameliorate the negative effects of heat stress (HS) by increasing GI glucagon-like peptide-2 production while capsicum oleoresin has been shown to reduce inflammatory response. The effects of an artificial high-intensity sweetener and capsicum oleoresin (CAPS-SUC; TakTik X-Hit, Pancosma, Switzerland) on growth performance of pigs were examined. Forty-eight pigs (12 wk of age, 43.2 ± 4.3 kg) were assigned to six treatments: thermoneutral conditions (21 ± 1.1 °C; 40% to 70% relative humidity) fed ad libitum with (TN+) or without supplement (TN-), heat stress (35 ± 1 °C; 20% to 40% relative humidity) fed ad libitum with (HS+) or without supplement (HS-), and thermoneutral conditions pair-fed to HS intake with (PFTN+) or without supplement (PFTN-). Supplementation (0.1 g/kg feed) began 2 d prior to the 3-d environmental treatment period. Body weights (BWs) and blood samples were collected on days -1 and 3. Rectal temperature (RT) and respiration rate (RR) were measured thrice daily and the feed intake (FI) was recorded daily. Intestinal sections were collected for histology. Pigs in HS conditions exhibited increased RT (~1.2 °C) and RR (~2.7-fold) compared with TN and PFTN groups (P < 0.01). HS+ animals had increased RR when compared with HS- animals (P < 0.02). Heat stress decreased FI compared with TN. HS and PFTN decreased (P < 0.05) average daily gain compared with TN. Supplement did not alter the BW gain. HS and PFTN decreased (P < 0.05) Gain:Feed compared with TN during environmental treatment. Supplementation with CAPS-SUC increased Gain:Feed by 0.12 (P < 0.05). Circulating glucose concentrations tended to decrease in CAPS-SUC vs. non-supplemented HS and PFTN animals (P ≤ 0.1). Circulating insulin concentrations as well as monocyte count increased in HS compared with PFTN (P < 0.04) but did not differ from TN and likely linked to altered FI. CAPS-SUC increased basophil count (P < 0.02), irrespective of environment. Ileal villus height tended to decrease during HS and PFTN compared with TN (P < 0.08), indicating an effect of intake. Overall, CAPS-SUC supplementation increased pig feed efficiency and may improve immune response.

Oxytocin is involved in steroid hormone-stimulated bovine satellite cell proliferation and differentiation in vitro.

Sex steroid hormones are used in the meat industry due to their ability to regulate muscle hypertrophy. However, the mechanisms underlying their action are not fully elucidated. Recent reports demonstrate that steroid hormones increase oxytocin (OXT) expression in skeletal muscle, indicating that OXT may play a role in satellite cell activity. This hypothesis was tested using steroid hormones (17ß-estradiol [E2]; trenbolone acetate [TBA]), tamoxifen (TAM), OXT, and atosiban (A: OXT receptor inhibitor) applied to bovine satellite cells (BSCs) to investigate BSC regulation by OXT. Oxytocin alone increased fusion index (P < 0.05) but not BSC proliferation. Oxytocin reduced (P < 0.05) apoptotic nuclei and stimulated migration rate (P < 0.05). Similarly, E2 and TBA increased (P < 0.05) BSC proliferation rate, fusion index, and migration and decreased (P < 0.05) apoptotic nuclei. 17ß-Estradiol or TBA supplemented with A had lower (P < 0.05) BSC proliferation rate, fusion index, and migration and more (P < 0.05) apoptotic nuclei compared with E2 or TBA alone. Furthermore, OXT expression increased (P < 0.05) in E2 or TBA-treated proliferating BSC. Oxytocin, E2, and TBA increased (P < 0.05) MyoD and MyoG expression in proliferating BSC. During BSC differentiation, OXT expression increased (P < 0.05) with E2 or TBA treatments. MyoG expression increased (P < 0.05) in OXT, E2, and TBA compared with control. However, A, OXT + A, TAM, TAM + OXT, E2 + TAM, E2 + A, and TBA + A decreased (P < 0.05) MyoG expression during BSC differentiation. These results indicate that OXT is involved in steroid hormone-stimulated BSC activity.

Effects of heat stress during porcine reproductive and respiratory syndrome virus infection on metabolic responses in growing pigs.

Heat stress (HS) and immune challenges negatively impact nutrient allocation and metabolism in swine, especially due to elevated heat load. In order to assess the effects of HS during Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection on metabolism, 9-wk old crossbred barrows were individually housed, fed ad libitum, divided into four treatments: thermo-neutral (TN), thermo-neutral PRRSV infected (TP), HS, and HS PRRSV infected (HP), and subjected to two experimental phases. Phase 1 occurred in TN conditions (22 °C) where half the animals were infected with PRRS virus (n = 12), while the other half (n = 11) remained uninfected. Phase 2 began, after 10 d with half of the uninfected (n = 6) and infected groups (n = 6) transported to heated rooms (35 °C) for 3 d of continuous heat, while the rest remained in TN conditions. Blood samples were collected prior to each phase and at trial completion before sacrifice. PPRS viral load indicated only infected animals were infected. Individual rectal temperature (Tr), respiration rates (RR), and feed intakes (FI) were determined daily. Pigs exposed to either challenge had an increased Tr, (P < 0.0001) whereas RR increased (P < 0.0001) with HS, compared to TN. ADG and BW decreased with challenges compared to TN, with the greatest loss to HP pigs. Markers of muscle degradation such as creatine kinase, creatinine, and urea nitrogen were elevated during challenges. Blood glucose levels tended to decrease in HS pigs. HS tended to decrease white blood cell (WBC) and lymphocytes and increase monocytes and eosinophils during HS. However, neutrophils were significantly increased (P < 0.01) during HP. Metabolic flexibility tended to decrease in PRRS infected pigs as well as HS pigs. Fatty acid oxidation measured by CO2 production decreased in HP pigs. Taken together, these data demonstrate the additive effects of the HP challenge compared to either PRRSV or HS alone.