Blood immunometabolic indices and polymorphonuclear neutrophil function in peripartum dairy cows are altered by level of dietary energy prepartum.

Cows experience some degree of negative energy balance and immunosuppression around parturition, making them vulnerable to metabolic and infectious diseases. The effect of prepartum feeding of diets to meet (control, 1.34 Mcal/kg of dry matter) or exceed (overfed, 1.62 Mcal/kg of dry matter) dietary energy requirements was evaluated during the entire dry period (∼45 d) on blood polymorphonuclear neutrophil function, blood metabolic and inflammatory indices, and milk production in Holstein cows. By design, dry matter intake in the overfed group (n=9) exceeded energy requirements during the prepartum period (-4 to -1 wk relative to parturition), resulting in greater energy balance when compared with the control group (n=10). Overfed cows were in more negative energy balance during wk 1 after calving than controls. No differences were observed in dry matter intake, milk yield, and milk composition between diets. Although nonesterified fatty acid concentration pre- (0.138 mEq/L) and postpartum (0.421 mEq/L) was not different between diets, blood insulin concentration was greater in overfed cows prepartum (16.7 µIU/mL) compared with controls pre- and postpartum (∼3.25 µIU/mL). Among metabolic indicators, concentrations of urea (4.63 vs. 6.38 mmol/L), creatinine (100 vs. 118 µmol/L), and triacylglycerol (4.0 vs. 8.57 mg/dL) in overfed cows were lower prepartum than controls. Glucose was greater pre- (4.24 vs. 4.00 mmol/L) and postpartum (3.49 vs. 3.30 mmol/L) compared with control cows. Among liver function indicators, the concentration of bilirubin increased by 2 to 6 fold postpartum in control and overfed cows. Phagocytosis capacity of polymorphonuclear neutrophils was lower prepartum in overfed cows (32.7% vs. 46.5%); phagocytosis in the control group remained constant postpartum (50%) but it increased at d 7 in the overfed group to levels similar to controls (48.4%). Regardless of prepartum diet, parturition was characterized by an increase in nonesterified fatty acid and liver triacylglycerol, as well as blood indices of inflammation (ceruloplasmin and haptoglobin), oxidative stress (reactive oxygen metabolites), and liver injury (glutamic oxaloacetic transaminase). Concentrations of the antioxidant and anti-inflammatory compounds vitamin A, vitamin E, and ß-carotene decreased after calving. For vitamin A, the decrease was observed in overfed cows (47.3 vs. 27.5 µg/100 mL). Overall, overfeeding energy and higher energy status prepartum led to the surge of insulin and had a transient effect on metabolism postpartum.

Dietary-induced negative energy balance has minimal effects on innate immunity during a Streptococcus uberis mastitis challenge in dairy cows during midlactation.

Ten multiparous Holstein cows were used to determine the effects of negative energy balance (NEB) on the immune response to a Streptococcus uberis (strain O140J) mastitis challenge during midlactation. Before the study, milk from all quarters of each cow was bacteriologically negative, with a composite somatic cell count of <200,000 cells/mL. Cows were paired based on parity, days in milk, and milk yield. At approximately 77 d in milk, half the cows (n = 5) were feed-restricted to 60% of calculated net energy for lactation requirements to induce NEB. Feed restriction lasted 7 d. Control cows (n = 5) were fed the same diet ad libitum (i.e., positive energy balance; PEB). After 5 d, one rear quarter in all cows was inoculated with 5,000 cfu of Strep. uberis. Jugular blood and aseptic quarter milk samples were collected daily until inoculation and every 6 h postinoculation for 36 h. Blood was analyzed for nonesterified fatty acids, beta-hydroxybutyrate, insulin, cortisol, albumin, serum amyloid A (SAA), and haptoglobin (Hp). Periodically throughout the trial period, blood neutrophils were isolated for determination of cell morphology, chemotaxis, and phagocytosis capability in vitro. Quarter milk samples were analyzed for concentrations of SAA, Hp, cytokines (tumor necrosis factor-alpha, IL-10 and IL-1beta), and activity of respiratory burst enzymes (superoxide dismutase and glutathione peroxidase). All cows developed local and systemic signs of mastitis and calculated NEB was similar to that of cows experiencing postpartal NEB. Serum glucose and insulin concentrations increased in both groups after challenge, most likely because of enhanced glycogenolysis and gluconeogenesis; results indicate that immune cell function may be glucose dependent. Serum cortisol concentration was higher in NEB than PEB cows during feed restriction only (before inoculation), and serum albumin concentration was higher in NEB than PEB cows during the infection period. Compared with PEB, cows in NEB had lower SAA concentrations in serum after 5 d of feed restriction but higher SAA concentrations in milk after Strep. uberis challenge. Serum Hp concentration was higher by 36 h postchallenge in NEB than in PEB cows. Phagocytic capability of neutrophils was lower in NEB than in PEB cows at 0 h of infection but decreased in both PEB and NEB cows through 36 h postinfection. Our results indicate that cows subjected to dietary-induced NEB during midlactation had relatively minimal alterations in immune function.

Review: Effects of Ractopamine Hydrochloride (Paylean) on welfare indicators for market weight pigs.

This review summarizes the effects of ractopamine hydrochloride (RAC) dose (5, 7.5, 10, and 20 mg/kg) on market weight pig welfare indicators. Ractopamine hydrochloride (trade name Paylean) is a ß-adrenergic agonist that was initially approved in the U.S. in 1999 at doses of 5 to 20 mg/kg to improve feed efficiency and carcass leanness. However, anecdotal reports suggested that RAC increased the rate of non-ambulatory (fatigued and injured) pigs at U.S. packing plants. This led to the addition of a caution statement to the Paylean label, and a series of research studies investigating the effects of RAC on pig welfare. Early research indicated that: (1) regardless of RAC administration, fatigued (non-ambulatory, non-injured) pigs are in a state of metabolic acidosis; (2) aggressive handling increases stress responsiveness at 20 mg/kg RAC, while 5 mg/kg reduces stress responsiveness to aggressive handling. Given this information, dosage range for Paylean was changed in 2006 to 5 to 10 mg/kg in market weight pigs. Subsequent research on RAC demonstrated that: (1) RAC has minimal effects on mortality, lameness, and home pen behavior; (2) RAC fed pigs demonstrated inconsistent prevalence and intensity of aggressive behaviors; (3) RAC fed pigs may be more difficult to handle at doses above 5 mg/kg; and (4) RAC fed pigs may have increased stress responsiveness and higher rates of non-ambulatory pigs when subjected to aggressive handling, especially when 20 mg/kg of RAC is fed.

Genetic parameters estimated at receiving for circulating cortisol, immunoglobulin G, interleukin 8, and incidence of bovine respiratory disease in feedlot beef steers.

Bovine respiratory disease complex (i.e., shipping fever and bacterial bronchopneumonia) is a multifaceted respiratory illness influenced by numerous environmental factors and microorganisms. Bovine respiratory disease (BRD) is just one component of BRD complex. Because BRD is moderately heritable, it may be possible to reduce the incidence of BRD through genetic selection. The objectives of this study were to determine the heritability and associative genetic relationships among immune system traits (i.e., cortisol, total IgG, IgG isotypes, and IL-8) in cattle monitored for BRD incidence. At an average of 83 d after weaning (219 d age and mean = 221.7 kg [SD 4.34]), crossbred steer calves ( = 2,869) were received at a commercial feedlot in southeastern Colorado over a 2-yr period. At receiving, jugular blood samples were collected at 212 (yr 1) and 226 d (yr 2) of age for immune trait analyses. The BRD phenotype was defined as a binomial variable (0 = no and 1 = yes) and compared with immune system traits measured at receiving (prior to illness onset). An animal identified as BRD positive exhibited ≥ 2 clinical signs (i.e., eye or nasal discharge, cough, lethargy, rapid breathing, acute interstitial pneumonia, or acute upper respiratory syndrome and/or a rectal temperature > 39.7°C). Heritability and genetic correlation estimates for categorical variable BRD, cortisol, IgG, IgG1, IgG2, and IL-8 were estimated from a sire model using ASREML. Heritability estimates were low to moderate for BRD (0.17 ± 0.08), cortisol (0.13 ± 0.05), IgG (0.15 ± 0.05), IgG1 (0.11 ± 0.05), IgG2 (0.24 ± 0.06), and IL-8 (0.30 ± 0.06). A moderate negative genetic correlation was determined between BRD and cortisol ( = -0.19 ± 0.32). Moderate positive correlations were found between BRD with IgG (0.42 ± 0.28), IgG1 (0.36 ± 0.32), and IL-8 ( = 0.26 ± 0.26). Variation in the BRD phenotype and immune system traits suggested herd health improvement may be achieved through genetic selection.

Neurochemical and cellular reorganization of the spinal cord in a murine model of bone cancer pain.

The cancer-related event that is most disruptive to the cancer patient's quality of life is pain. To begin to define the mechanisms that give rise to cancer pain, we examined the neurochemical changes that occur in the spinal cord and associated dorsal root ganglia in a murine model of bone cancer. Twenty-one days after intramedullary injection of osteolytic sarcoma cells into the femur, there was extensive bone destruction and invasion of the tumor into the periosteum, similar to that found in patients with osteolytic bone cancer. In the spinal cord, ipsilateral to the cancerous bone, there was a massive astrocyte hypertrophy without neuronal loss, an expression of dynorphin and c-Fos protein in neurons in the deep laminae of the dorsal horn. Additionally, normally non-noxious palpation of the bone with cancer induced behaviors indicative of pain, the internalization of the substance P receptor, and c-Fos expression in lamina I neurons. The alterations in the neurochemistry of the spinal cord and the sensitization of primary afferents were positively correlated with the extent of bone destruction and the growth of the tumor. This "neurochemical signature" of bone cancer pain appears unique when compared to changes that occur in persistent inflammatory or neuropathic pain states. Understanding the mechanisms by which the cancer cells induce this neurochemical reorganization may provide insight into peripheral factors that drive spinal cord plasticity and in the development of more effective treatments for cancer pain.

Wider stall space affects behavior, lesion scores, and productivity of gestating sows.

Limited space allowance within the standard gestation stall is an important welfare concern because it restricts the ability of the sow to make postural adjustments and hinders her ability to perform natural behaviors. Therefore, we evaluated the impacts of increasing stall space and/or providing sows the freedom to access a small pen area on sow well-being using multiple welfare metrics. A total of 96 primi- and multiparous crossbred sows were randomly assigned in groups of 4 sows/treatment across 8 replicates to 1 of 3 stall treatments (TRT): standard stall (CTL; dimensions: 61 by 216 cm), width-adjustable stall (flex stall [FLX]; dimensions: adjustable width of 56 to 79 cm by 216 cm), or an individual walk-in/lock-in stall with access to a small communal open-pen area at the rear of the stall (free-access stall [FAS]; dimensions: 69 by 226 cm). Lesion scores, behavior, and immune and productivity traits were measured at various gestational days throughout the study. Total lesion scores were greatest for sows in FAS and least for sows in FLX ( < 0.001). Higher-parity sows in FAS had the most severe lesion scores (TRT × parity, < 0.0001) and scores were greatest at all gestational days (TRT × day, < 0.05). Regardless of parity, sows in FLX had the least severe scores ( < 0.0001). As pregnancy progressed, lesion scores increased among sows in CTL ( < 0.05). Sow BW and backfat (BF) were greater for sows in FLX and FAS ( < 0.05), and BCS and BF were greater for parity 1 and 2 sows in FAS than the same parity sows in CTL (TRT × parity, < 0.05). Duration and frequency of some postural behaviors and sham chew behavior were affected by TRT ( < 0.05) and time of day (TRT × day, < 0.05). These data indicate that adequate stall space, especially late in gestation, may improve the well-being of higher-parity and heavier-bodied gestating sows as assessed by changes in postural behaviors, lesion severity scores, and other sow traits. Moreover, compromised welfare measures found among sows in various stall environments may be partly attributed to the specific constraints of each stall system such as restricted stall space in CTL, insufficient floor space in the open-pen area of the FAS system, and gate design of the FLX (e.g., direction of bars and feeder space). These results also indicate that parity and gestational day are additional factors that may exacerbate the effects of restricted stall space or insufficient pen space, further compromising sow well-being.

Murine models of inflammatory, neuropathic and cancer pain each generates a unique set of neurochemical changes in the spinal cord and sensory neurons.

The aim of this investigation was to determine whether murine models of inflammatory, neuropathic and cancer pain are each characterized by a unique set of neurochemical changes in the spinal cord and sensory neurons. All models were generated in C3H/HeJ mice and hyperalgesia and allodynia behaviorally characterized. A variety of neurochemical markers that have been implicated in the generation and maintenance of chronic pain were then examined in spinal cord and primary afferent neurons.Three days after injection of complete Freund's adjuvant into the hindpaw (a model of persistent inflammatory pain) increases in substance P, calcitonin gene-related peptide, protein kinase C gamma, and substance P receptor were observed in the spinal cord. Following sciatic nerve transection or L5 spinal nerve ligation (a model of persistent neuropathic pain) significant decreases in substance P and calcitonin gene-related peptide and increases in galanin and neuropeptide Y were observed in both primary afferent neurons and the spinal cord. In contrast, in a model of cancer pain induced by injection of osteolytic sarcoma cells into the femur, there were no detectable changes in any of these markers in either primary afferent neurons or the spinal cord. However, in this cancer-pain model, changes including massive astrocyte hypertrophy without neuronal loss, increase in the neuronal expression of c-Fos, and increase in the number of dynorphin-immunoreactive neurons were observed in the spinal cord, ipsilateral to the limb with cancer. These results indicate that a unique set of neurochemical changes occur with inflammatory, neuropathic and cancer pain in C3H/HeJ mice and further suggest that cancer induces a unique persistent pain state. Determining whether these neurochemical changes are involved in the generation and maintenance of each type of persistent pain may provide insight into the mechanisms that underlie each of these pain states.

Photoperiod and bromocriptine treatment effects on expression of prolactin receptor mRNA in bovine liver, mammary gland and peripheral blood lymphocytes.

Recent evidence suggests that photoperiod influences immune function. Interestingly, photoperiod has profound effects on concentrations of prolactin (PRL), a hormone also known to be involved in fluctuations of the immune system. However, the impact of photoperiod on PRL receptor (PRL-R) expression is poorly understood, particularly in tIssues of the immune system. Two experiments were performed to increase the general understanding of how photoperiod interacts with the immune system. Our first objective was to determine the effects of photoperiod on PRL-R mRNA expression and cellular immune function. Lymphocytes were isolated from blood collected from calves (n=10) and PRL-R mRNA expression of both long and short forms was quantified using real-time PCR. Lymphocytes expressed PRL-R mRNA, suggesting that PRL could act directly on these cells. To determine the relationship between photoperiod and PRL-R mRNA expression in other tIssues, hepatic and mammary biopsies were collected after calves were exposed to long days (LDPP; 16 h light:8 h darkness) or short days (SDPP; 8 h light:16 h darkness). Relative to LDPP, SDPP decreased circulating PRL, but increased expression of both forms of PRL-R mRNA in liver, mammary gland and lymphocytes. Short days also increased lymphocyte proliferation compared with long days. Reversal of photoperiodic treatments reversed the effects on circulating PRL, PRL-R mRNA expression and lymphocyte proliferation. Our second objective was to manipulate PRL concentration in photoperiod-treated animals, using bromocriptine. Concentrations of PRL in LDPP animals injected daily with bromocriptine for 1 week were decreased compared with LDPP controls, to a level similar to SDPP animals. Receptor expression was increased in LDPP+bromocriptine-treated animals relative to LDPP controls, as was lymphocyte proliferation. Overall, our results indicate that photoperiodic effects on PRL-R mRNA expression were inverse to those on circulating PRL, with short days stimulating expression of both forms of PRL-R mRNA. Expression of PRL-R mRNA changed in the same direction as lymphocyte proliferation with regard to photoperiod treatment, suggesting a link between photoperiodic effects on PRL sensitivity and immune function. Thus, PRL signaling may mediate photoperiodic effects on immune function.

Intracerebroventricular porcine corticotropin-releasing hormone and cortisol effects on pig immune measures and behavior.

The effects of intracerebroventricular (icv) administration of porcine corticotropin-releasing hormone (pCRH) and cortisol on the immune system and behavior were examined in domestic pigs. In Experiment 1, 50 micrograms of pCRH in 200 microliters of saline or 200 microliters of vehicle was administered i.c.v. at 0600 h. Blood samples were obtained at 0600 (prior to injection), 0700, and 0800 h. Plasma cortisol concentrations were higher at 1 and 2 h after pCRH than after saline. Generally, pCRH failed to effect NK cytotoxicity or lymphocyte proliferation in response to phytohemagluttin (PHA). However, 1 h postinjection, pigs administered pCRH i.c.v. had marginally lower NK activity than control pigs. Pigs injected with pCRH had substantially lower neutrophil chemotaxis (CHTX) than the control pigs at 1 and 2 h postinjection. As blood cortisol concentration increased, neutrophil CHTX decreased. Pigs injected i.c.v. with pCRH had higher neutrophil numbers and neutrophil:lymphocyte ratios than control pigs. Percentage of lymphocytes was higher among control than treated pigs. Central pCRH increased overall activity, particularly walking, standing, licking, rooting, and increased activity-related sequences (e.g., sit, walk and stand, walk), but reduced complex oral/nasal sequences (e.g., root, lick). In Experiment 2, pigs were injected i.c.v. with 10 micrograms of cortisol in 200 microliters of saline or with vehicle at 0600 h. Administration of cortisol failed to effect NK cytotoxicity, lymphocyte proliferation, CHTX, or leukocyte distribution. Pigs given cortisol had no apparent change in behavior. These data indicate leukocyte distribution and specific neutrophil function in pigs were significantly modulated by stress-related hormones of the hypothalamic-pituitary-adrenal axis and complexity of behavioral sequences (pigs repeating certain behavioral sequences) associated with increased activity was reduced. Oral/nasal stereotypies (as seen among confined sows) were not elevated among pigs given i.c.v. pCRH. CRH given by i.c.v. administration may serve as a better model for acute rather than chronic stress.

Heat and social stress effects on pig immune measures.

Forty-eight domestic pigs were used to evaluate the effects of heat and social stress on immune indices. Pigs were brought together in groups of three per pen and video-taped for the first 72 h. Video tapes were viewed to determine time spent in aggressive and submissive behaviors. Social status of each pig was determined from outcomes of agonistic interactions. Pens of pigs were housed in either a thermoneural (control, 24 degrees C) or heat-stress (33 degrees C) air temperature. Immune measures were determined from blood samples obtained on d 0, 7, 14, 21, and 28 after grouping. Social status had an effect (P < .05) on lymphocyte proliferation in response to pokeweed mitogen: socially intermediate pigs had a higher proliferative response than socially dominant or subordinate pigs. Many immune measures showed a significant interaction between heat and social stress over days of the study. Generally, socially dominant or submissive pigs had alterations in immune function (elevated numbers of neutrophils, decreased antibody production) compared with socially intermediate pigs. In conclusion, heat and social stress interact in their effect on the pig's immune system. Although one might have predicted immunosuppression among submissive pigs, there also seemed to be immunological costs to dominant pigs as well. These data also have implications in design of stressor research in that social behavior should be measured or controlled.

In vivo glucocorticoid effects on porcine natural killer cell activity and circulating leukocytes.

Porcine natural killer (NK) cell cytotoxicity, plasma cortisol, total white blood cells (WBC), neutrophil:lymphocyte ratio (N:L), and circulating blood leukocytes were examined from pigs injected i.v. with either saline, ACTH, cortisol, or treated with metyrapone. Plasma cortisol increased (P < .05) after ACTH and cortisol treatments and decreased (P < .05) after metyrapone treatment; thus, treatments had the intended effects on in vivo cortisol concentrations. In Exp. 1, pigs were injected with either saline or ACTH at 0600 after the initial blood samples were taken (time 0). The ACTH had no effect (P > .10) on NK cytotoxicity. Pigs injected i.v. with ACTH had fewer lymphocytes and more neutrophils (P < .05) than control pigs. The N:L ratio was greater (P < .05) among ACTH-injected than among control pigs. In Exp. 2, pigs were injected i.v. with either saline or 40 or 400 micrograms of cortisol at 0600 after the initial blood samples were obtained (time 0). Cortisol at 40 micrograms had no effect (P > .10) on NK cytotoxicity. However, a 400-micrograms bolus of cortisol reduced (P < .05) NK cytotoxicity (control = 39.5, cortisol = 28.3% cytotoxicity, SEM = 3.7). Each dose of cortisol reduced (P < .05) circulating blood lymphocyte numbers. In Exp. 3, pigs were fed 1 g of metyrapone or no metyrapone the night before sampling. Blood samples were obtained at 0600, 0700, and 0800. Metyrapone reduced (P < .05) NK cytotoxicity (control = 28.6, metyrapone = 11.8%, SEM = 1.9). Pigs treated with metyrapone had greater (P < .05) numbers of neutrophils than control pigs. Numbers of lymphocytes were greater (P < .05) among control than among treated pigs. Pigs treated with metyrapone had a greater (P < .05) N:L ratio than control pigs. In conclusion, normal physiological concentrations or moderately increased blood cortisol concentrations did not influence NK activity, although leukocyte distributions were changed. We conclude that greatly increased or greatly decreased circulating concentrations of cortisol reduced NK cytotoxicity.

Space allowance and high fiber diet impact performance and behavior of group-kept gestating sows.

Identifying and optimizing housing and management systems that improve the well-being of the gestating sow is essential to sustaining animal agriculture. Therefore, the impact of 2 floor-space allowances and a high-fiber gestation diet on dry group-housed sows were evaluated using multiple measures of well-being. Groups of 10 multiparous sows/pen (n = 221) were assigned randomly to treatments in a 2 × 2 factorial arrangement to either a corn-soybean meal diet (CTL) or corn-soybean meal diet supplemented with soybean hulls and wheat middlings (FBR), and floor-space allowance of either 1.7 or 2.3 m(2)/sow. Sow BW, backfat (BF), and body condition score (BCS) were all recorded on d 34, 65, 90, and 110 of gestation, whereas skin lesions were scored on d 34, every 2 d for the first 2-wk postmixing, and then biweekly throughout gestation. Blood sample was collected only on d 34 for cortisol (baseline), and samples were collected on d 90 of gestation for other measures including cortisol. Behavior was registered on multiple days throughout gestation. Sows fed FBR and kept at 1.7 m(2) produced heavier litter and weaning weights and greater number of piglets born alive, compared to sows fed FBR but kept at 2.3 m(2) of floor space (diet × floor space, P ≤ 0.04). Sows fed FBR and kept at 1.7 m(2) performed fewer oral-nasal-facial and sham-chew behaviors than sows fed CTL and kept at the same floor space (diet × floor space, P ≤ 0.044). Sows kept at 1.7 m(2) of floor space had a greater (P < 0.05) total lesion severity score than sows kept at 2.3 m(2)/sow, and vulva lesion scores were more (P < 0.02) severe among CTL-fed sows than FBR-fed sows. Parities 2 and 3 sows fed FBR and kept at 1.7 m(2) of floor space were heavier (P < 0.001) than sows fed the same diet but kept at 2.3 m(2). These results indicate that keeping small groups of pregnant sows at a minimum floor-space allowance of 1.7 m(2)/sow and floor feeding these sows a high-fiber diet can improve short-term sow well-being.

Effect of variability in lighting and temperature environments for mature gilts housed in gestation crates on measures of reproduction and animal well-being.

The effects of room temperature and light intensity before breeding and into early gestation were evaluated on the reproductive performance and well-being of gilts housed individually in crates. In eight replicates, estrus was synchronized in mature gilts (n = 198) and after last feeding of Matrix were randomly assigned to a room temperature of 15°C (COLD), 21°C (NEUTRAL), or 30°C (HOT) and a light intensity of 11 (DIM) or 433 (BRIGHT) lx. Estrous detection was performed daily and gilts inseminated twice. Blood samples were collected before and after breeding for determination of immune measures and cortisol concentrations. Gilt ADFI, BW, and body temperature were measured. On d 30 postbreeding, gilts were slaughtered to recover reproductive tracts to evaluate pregnancy and litter characteristics. There were no temperature × light intensity interactions for any response variable. Reproductive measures of follicle development, expression of estrus, ovulation rate, pregnancy rate (83.2%), litter size (14.3 ± 0.5), and fetal measures were not affected by temperature or lighting (P > 0.10). Gilts in COLD (37.6°C) had a lower (P < 0.05) rectal temperature than those in NEUTRAL (38.2°C) and HOT (38.6 ± 0.04°C). Both BW gain and final BW were greater (P < 0.0001) for gilts kept in HOT than those in NEUTRAL or COLD environments. Cortisol was greater (P < 0.01) for gilts kept in COLD compared with those kept in the HOT room. Gilts housed in the HOT environment made more postural changes (P < 0.05) than did those kept in either COLD or NEUTRAL temperatures. Gilts kept in the HOT temperature spent more total time lying and more time lying ventrally compared with those gilts housed in the NEUTRAL or COLD rooms. Total white blood cells and the percentage of neutrophils as well as neutrophil-to-lymphocyte ratio were all influenced (P < 0.05) by temperature but there was no effect (P > 0.10) of light or interaction with temperature on other immune cells or measures. These results indicate that temperatures in the range of 15 to 30°C or light intensity at 11 to 433 lx do not impact reproduction during the follicular phase and into early gestation for mature gilts housed in gestation crates. However, room temperature does impact physiological, behavioral, and immune responses of mature gilts and should be considered as a potential factor that may influence gilt well-being during the first 30 d postbreeding.

Space allowance for gestating sows in pens: behavior and immunity.

Different floor space allowances for dry, pregnant sows in pens were evaluated to determine the impacts of space on sow behavior, immune, and cortisol measures. The experiment consisted of 6 replications (blocks 1 to 6; n = 20 sows/group), and within each replicate, physiological measurements were recorded for 2 consecutive pregnancies. A total of 152 sows were measured at 1 gestation, and 65 of those sows were measured at the successive gestation (n = 217). Groups of 5 sows/pen were assigned to 1.4, 2.3, or 3.3 m(2) of floor space/sow or of 5 sows in individual stalls (1.34 m(2)). Behavior measures were stand, sit, lie, walk, drink, oral-nasal-facial (ONF), sham chew, and aggression. Immune traits included both descriptive and functional aspects and cortisol. At d 90 ± 5 of gestation, the occurrence of ONF behaviors increased from 0300 to 1500 h, and lying behavior decreased from 0700 to 1100 h for sows kept at 2.3 m(2). Sows in stalls displayed more (P < 0.05) ONF from 1500 to 2300 h. Stand, sit, drink, ONF, and sham-chew behaviors were affected by floor space; sows in pens at 2.3 m(2) performed more ONF, and sows at 1.4 m(2) performed more sham chewing (P < 0.05). Standing (P = 0.05) and drinking (P = 0.06) were increased, but lying (P = 0.06) was reduced for sows in pens at 2.3 or 3.3 m(2). Sitting and drinking were greater but lying was less for sows in stalls compared with sows in pens (P < 0.01). Immune traits were affected by treatment (P < 0.05); neutrophils were less and lymphocytes were greater, resulting in a reduced neutrophil:lymphocyte (N:L) ratio (P < 0.05) for sows in pens at 3.3 m(2). Natural killer cell was greater but lymphocyte proliferation was less for sows in pens at 1.4 m(2) (P < 0.05). Sows in stalls had greater N:L ratio than sows in pens (P < 0.05). For sows in pens, linear and quadratic responses were detected for behavior and immune traits. As floor space increased, walking and aggression increased. As floor space decreased, neutrophils, N:L, and natural killer cell increased, but as floor space increased lymphocyte proliferation increased. On the basis of behavioral and physiological responses shown by sows in all 4 environments it is apparent that neither floor space nor stall environment provided adequate or quality of space to improve sow well-being. However, the differential behavioral and physiological mechanisms initiated by sows in response to their specific environment the sows were able to evoke the appropriate response(s) needed to adequately adapt to their environment.

Making sense of apparently conflicting data: stress and immunity in swine and cattle.

Stress is generally considered to suppress the immune system and may lead to an increase in the occurrence of disease in the presence of a pathogen. The immune system is ordinarily brought back to a baseline response level after immune challenge through homeostatic processes, in part regulated by the hypothalamic-pituitary-axis. Often, findings reported from various studies investigating the effects of stress on the immune system are conflicting and difficult to reconcile into a cohesive and comprehensible set of universally applicable theories. These discrepancies may be partly explained by the types and durations of the stressors, the aspect(s) of immune system measured, genetics, and social status. A particular stressor may enhance cell-mediated immune responses while suppressing humoral responses or vice versa, thus disrupting the balance between these components of the immune system. How farm animals perceive their environment depends not only on traditional environmental stressors (e.g., heat, cold, humidity, pollutants), but also on aspects of their social environment. Dominant animals may have enhanced immune activation, whereas subordinates have suppression of the same immune component in response to the same stressor. This could explain why individual animals within a group respond differently to stressors and disease challenges. A better understanding of the consequences and complex interactions between social and environmental stressors for innate and adaptive immune traits must be developed so we can more fully understand the effects of stress on immunity in livestock. Once these complex relationships are better understood, more effective interventions can be designed to improve animal health and well-being.

Immune responses of piglets to weaning stress: impacts of photoperiod.

An acute stress response can be provoked by abrupt social, nutritional, and environmental changes associated with weaning, and this may disrupt homeostasis and thus compromise well-being. Manipulating environmental factors, such as photoperiod, might provide a simple way to reduce the physiological consequences that piglets experience due to weaning stress. The objective of this study was to evaluate the impacts of photoperiod manipulation across various weaning ages on leukocyte populations, lymphocyte proliferation, natural killer cytotoxicity (NK), chemotaxis, phagocytosis, and immunoglobulin G, cortisol, and BW of piglets during the nursery phase. Sixty-eight crossbred piglets were obtained from sows kept on a short-day (8 h of light/d) photoperiod from d 90 of gestation until weaning. Piglets were weaned at 14, 21, or 28 d of age and kept on a short or long (16 h of light/d) photoperiod until 10 wk of age. Piglet BW and blood samples were collected at weaning and at 6, 8, and 10 wk of age. Pigs weaned at 28 d had reduced neutrophil counts (P < 0.001), phagocytosis (P < 0.001), and lymphocyte proliferation (P < 0.05) at weaning compared with those weaned at 14 and 21 d. Pigs weaned at 21 d tended to have lower (P = 0.08) lymphocyte counts than did pigs weaned at 14 or 28 d. Pigs weaned at 14 d had reduced (P < 0.01) NK relative to those weaned at 21 or 28 d. Photoperiod also influenced pig BW and immune status. Generally, those pigs on the long-day photoperiod and weaned at 28 d were heavier (P < 0.001) than their counterparts weaned at 14 or 21 d. At 6 wk of age, NK was greater (P = 0.002) in pigs kept on a long day and weaned at 14 or 21 d than in pigs weaned at 28 d. Phagocytosis was less (P = 0.005) at 6 wk of age, but was greater at 8 wk, in piglets kept on the long day and weaned at 28 d than in long-day pigs weaned at 14 or 21 d. These results suggest that photoperiod differentially influences immune responses in piglets weaned at different ages and indicate an inverse relationship between growth and immune status. Here, weaning at 28 d and a long-day photoperiod was the treatment combination that was most physiologically beneficial to piglets, whereas a 14-d weaning and short-day photoperiod was least physiologically beneficial.

Space allowance for dry, pregnant sows in pens: body condition, skin lesions, and performance.

Different floor space allowances for dry, pregnant sows in pens were evaluated to determine the impacts of space on sow performance, productivity, and body lesions during 2 consecutive farrowings. Treatment groups of 5 sows/pen were assigned to 1.4, 2.3, or 3.3 m(2) of floor space/sow or of 5 sows in individual stalls (1.34 m(2)). The experiment consisted of 6 replications (blocks 1 to 6), and within each block measurements were recorded for 2 consecutive pregnancies and farrowings. A total of 152 sows were measured at 1 farrowing, and 65 of those sows were measured at the successive farrowing (n = 217 records). Performance traits were BCS, BW, backfat (BF), days until rebred, and proportion culled. Litter traits were number of piglets born alive, male:female ratio, and proportions of stillborn, mummified, or dead piglets after birth. Litter performance measures were mean piglet BW and gain and litter BW. Lesion scores were assessed for several body regions. There were treatment and parity effects and interactions for several traits. An interaction of space treatment and parity occurred for sow mean BW, d-110 BW, BF, litter size, and litter and piglet BW and gain, with most effects in parity 2, 3, and 4 sows. Space affected sow mean (P < 0.001) and d-110 BW (P < 0.05) and mean BF and adjusted BF (P < 0.001); sows in pens at

Impacts of chronic stress and social status on various physiological and performance measures in pigs of different breeds.

Pigs typically experience various environmental stressors, which can negatively affect performance. Cortisol concentrations and various immune and performance measures are influenced by breed, but few data exist describing the impact of breed on stress responsiveness in pigs. The objective of this experiment was to determine if certain physiological responses to chronic stressors differed among 3 breeds and 2 commercial lines of pigs. The pigs were Landrace (n = 36), Meishan (n = 30), Yorkshire (n = 32), or 1 of 2 commercial lines (Line-A and Line-B; both n = 36). All pigs were weaned at 17 to 21 d and kept in a common nursery. At 49 d of age, pigs were assigned to 1 of 2 treatments: stress (heat, crowding, and mixing) or control (no stress treatment). Pigs were allocated to groups of 3 pigs per pen of the same sex. Control pigs were kept with their littermates. At the onset of the experiment, stressed pigs were mixed with 2 unfamiliar pigs once, and heat and crowding stressors were implemented simultaneously for 14 d. Pigs allocated to the stress treatment were video-recorded for 24 h following initiation of mixing to determine social status: dominant, intermediate, or submissive. Blood samples were taken at d 0 (baseline), 1, 7, and 14 to assess cortisol concentrations and immune measures. Breed and treatment affected cortisol, immune, and performance measures, but no significant breed x treatment interactions were found. In general, pigs subjected to the chronic stressor had lower (P < 0.001) BW and ADG (P < 0.001) than did control pigs. Plasma cortisol was lower (P < 0.001) among stressed pigs at d 7 and 14. Regardless of breed, lipopolysaccharide-induced proliferation (P < 0.01) and natural killer (NK; P < 0.005) cytotoxicity were greater in stressed pigs compared with controls. Furthermore, among stressed pigs, dominant pigs had a greater total white blood cell count (P < 0.005), NK (P < 0.05), and phagocytosis (P < 0.05) than the subordinate pigs. The results indicate that pig breed did not influence the physiological responses to the chronic concurrent stressors imposed for 14 d in this study, but social status did influence the immune responsiveness of these pigs to heat, crowding, and mixing.

Photoperiod influences the immune status of multiparous pregnant sows and their piglets.

Manipulation of photoperiod may provide a noninvasive, easily implemented, effective method to improve immune status and enhance the efficiency of production. The objective of this study was to evaluate the impact of manipulation of photoperiod on endocrine and immune responses of pregnant sows and their offspring. At d 83 of gestation, sows were moved to gestation stalls and kept on a photoperiod of 12 h of light:12 h of dark until d 90, when sows were assigned to a long day (LD; 16 h of light/d) or a short day (SD; 8 h of light/d) treatment. During farrowing and lactation, one-half of the sows remained on their initial photoperiod (LD:LD or SD:SD), whereas one-half were switched to the opposite treatment (LD:SD or SD:LD). Blood samples were collected from sows at d 0, 7, 14, and 21 posttreatment, 24-h postfarrowing, and the end of lactation (approximately d 21 postfarrowing). Piglets were bled at 7 and 21 d of age for immune measures. Relative to sows on LD, sows on SD had greater concanavalin A- (P = 0.003) and lipopolysaccharide- (P = 0.02) induced proliferative responses at d 7 but reduced responses at d 14. Compared with SD, sows on LD had a greater (P < 0.05) percentage of neutrophils and fewer (P < 0.05) lymphocytes at d 7, resulting in a greater (P = 0.05) neutrophil:lymphocyte ratio. Neutrophil phagocytosis was greater at d 21 in sows kept on LD. Cortisol concentrations tended to be greatest (P = 0.10) in sows on SD:SD at 24-h postfarrowing and throughout lactation. At 7 d of age, piglets on LD:SD had greater (P = 0.001) total white blood cells (WBC) and plasma cortisol (P = 0.001) relative to those on the other photoperiod treatments. Plasma immunoglobulin G was less (P = 0.001) in piglets from sows kept on SD:LD compared with the other photoperiod treatments. Piglets from sows kept on LD:LD tended to have lower total WBC (P = 0.08) at 21 d of age. Piglets from sows kept on SD:SD had greater concanavalin A- (P < 0.001) and lipopolysaccharide-induced (P < or = 0.10) proliferation responses and cortisol (P = 0.05). Phagocytosis was greater (P < 0.003) in piglets from sows that were kept on LD:LD. Cortisol (P = 0.02), WBC (P = 0.003), and immunoglobulin G (P = 0.001) were all influenced by gestational photoperiod treatment. These data indicate that photoperiod influences the immune status and endocrine response of piglets from dams that have been kept on a defined photoperiod. We conclude that photoperiod effects on piglets may be programmed in utero and can last throughout lactation.