Low-Protein Diets Differentially Regulate Energy Balance during Thermoneutral and Heat Stress in Cobb Broiler Chicken (Gallus domesticus).

The objective was to assess whether low-protein (LP) diets regulate food intake (FI) and thermogenesis differently during thermoneutral (TN) and heat stress (HS) conditions. Two-hundred-day-old male broiler chicks were weight-matched and assigned to 36 pens with 5-6 chicks/pen. After 2 weeks of acclimation, birds were subjected into four groups (9 pens/group) including (1) a normal-protein diet under TN (ambient temperature), (2) an LP diet under TN, (3) a normal-protein diet under HS (35 °C for 7 h/day), and (4) an LP diet under HS, for 4 weeks. During HS, but not TN, LP tended to decrease FI, which might be associated with a lower mRNA abundance of duodenal ghrelin and higher GIP during HS. The LP group had a higher thermal radiation than NP under TN, but during HS, the LP group had a lower thermal radiation than NP. This was linked with higher a transcript of muscle ß1AR and AMPKα1 during TN, but not HS. Further, LP increased the gene expression of COX IV during TN but reduced COX IV and the sirtuin 1 abundance during HS. The dietary protein content differentially impacted plasma metabolome during TN and HS with divergent changes in amino acids such as tyrosine and tryptophan. Compared to NP, LP had increased abundances of p_Tenericutes, c_Mollicutes, c_Mollicutes_RF9, and f_tachnospiraceae under HS. Overall, LP diets may mitigate the negative outcome of heat stress on the survivability of birds by reducing FI and heat production. The differential effect of an LP diet on energy balance during TN and HS is likely regulated by gut and skeletal muscle and alterations in plasma metabolites and cecal microbiota.

Immune phenotype is differentially affected by changing the type of bovine respiratory disease vaccine administered at revaccination in beef heifers.

During preconditioning, modified-live vaccines are frequently administered to beef calves before weaning. In this study, we began to characterize the immune phenotype of calves that received a modified-live vaccination at 3-4 months of age and then either received the same modified-live or an inactivated vaccine upon arrival at the feedlot (weaning) and 28 days post-arrival (booster). Innate and adaptive immune measures were assessed before revaccination and 14 and 28 days post. Heifers that received three doses of the modified-live vaccine exhibited a relatively balanced immune response based on increases in mean cytokine concentrations (IL-17, IL-21) and total immunoglobulin-G (IgG) and subsets IgG1 and IgG2, which are related to both arms of the adaptive immune system. Conversely, heifers that received one dose of modified live and two doses of the inactivated vaccine had a more robust neutrophil chemotactic response and greater serum-neutralizing antibody titers, resulting in an enhanced innate immune and a skewed proinflammatory response. These results indicate that the revaccination protocol used after initial vaccination with a modified-live vaccine differentially influences the immune phenotype of beef calves, with three doses of modified live inducing potentially immune homeostasis and a combination of modified live and inactivated vaccines inducing a skewed immune phenotype. However, more research is needed to determine the protective efficacy of these vaccination protocols against disease.

The Effects of Respiratory Vaccine Type and Timing on Antibody Titers, Immunoglobulins, and Growth Performance in Pre- and Post-Weaned Beef Calves.

In order to examine the effects of vaccine type and timing of crossbred beef calves (n = 151) were assigned to one of three BRD vaccination protocols stratified by breed of sire, sex, and date of birth, which included: (1) KM-a pentavalent killed viral (KV) vaccine at 2 to 3 months of age (D 0) and a pentavalent modified-live viral (MLV) vaccine at weaning (D 127); (2) MM-MLV on D 0 and revaccinated on D 127 or (3) WN-MLV at weaning and D 140. Vaccination treatment did not affect performance nor BRSV serum-neutralizing antibody titers. Serum-neutralizing antibody titers to BVDV-1 were greatest for the MM through D 154. However, following booster (KM) or initial vaccination (WN) at D 127, titers increased for the other treatment groups to higher values (KM) by the end of the study. Delay of initial vaccination until weaning may have delayed specific antibody response in the WN group and skewed the immune response towards a Th-1 or cell-mediated response. Overall, the inclusion of an MLV in the vaccine protocol resulted in a more robust antibody response, and the timing of vaccination may affect the onset of efficacious and robust vaccine responses.

Association of maternal temperament and offspring disposition on growth performance.

Animal behavior is complex and varies in definition, depending upon specific traits under observation. Temperament is one component of behavior, that in cattle, is described as the level of fearfulness to a novel or threatening environment. Temperament is a heritable trait which is important since aggressiveness and docility contribute to reproductive success, growth, and carcass quality. We observed maternal temperament at calving and the subsequent influence, if any, on offspring disposition at weaning and their effects collectively on growth performance and carcass traits. Maternal behaviors at calving were observed at four locations within the University of Arkansas system. Cows were assigned a maternal disposition score (MDS) at calving; a scale from 1 to 5 in which aggression decreases. At weaning, calves were assigned a chute score (CS); a scale from 1 to 6 in which aggression increases. Both scoring systems have been previously established. Blood was collected during the 56-d backgrounding period postweaning for blood glucose analysis. Data were analyzed using GLIMMIX procedures of SAS (α = 0.05). The relationship between the two scoring systems was determined with a Pearson correlation (P = 0.22). Animal was the experimental unit and blocked by location for all dependent variables. Location, sex, diet, and MDS were included in the class as covariables for all growth performance and carcass data related to CS. Cows that were more aggressive birthed heavier calves (P < 0.01) compared to indifferent cows. Calves born to cows with either very aggressive or very attentive (MDS of 2 or 3, respectively) scores were heavier upon feedlot entry (P = 0.03) compared to those from indifferent or apathetic cows (MDS of 4 or 5, respectively). Calves defined as nervous and restless (CS of 3 and 2, respectively) were heavier at weaning compared to docile calves (P < 0.01). Restless calves were heavier compared to nervous calves upon arrival and exiting the feedlot (P ≤ 0.01). Calves that were docile at weaning had greater marbling compared to calves that were restless (P ≤ 0.01). Calves that were restless at weaning had greater lean muscle area compared to calves that were nervous (P = 0.05). No definitive relationship was determined between dam and calf temperament. However, the results suggest temperament does impact growth performance and carcass traits but whether the influence comes from the dam or calf temperament, specifically, remains unanswered.

Maternal Supplementation of Saccharomyces cerevisiae boulardii during Late-Gestation through Lactation Differentially Modulated Immune Status and Stress Responsiveness of the Progeny to Farrowing and Weaning Stressors.

The study aimed to investigate and characterize the maternal effects of feeding Saccharomyces cerevisiae var. boularddii (Scb) to sows from late-gestation through lactation on progeny cortisol, immune status, and stress responsiveness from birth to 14 days post-weaning. Eighty-four piglets were born to sows fed control (CON) or probiotic (PRO) boluses twice daily for 59 days. Blood samples were obtained at birth and 24 h later to assess prenatal effects; 7, 14, and 21 day-of-age to assess potential developmental effects; and at 24 h, 7, and 14 days post-weaning to assess the effects of weaning stress on immune and cortisol responses. Pigs born to PRO sows had less robust cortisol response and enhanced immune parameters at birth and 24 h later, indicating less stress. In response to weaning, pigs born to and nursed by PRO sows displayed unique cortisol and immune profiles than CON pigs. These results indicate that feeding sows Scb probiotics during late gestation reduces stress responsiveness to farrowing stress while increasing immune cell populations. Pigs nursed by PRO sows had a more robust initial cortisol response and enhanced neutrophil function and B-cell lymphocyte proliferation in response to weaning stress. These data imply it may be possible to maternally alter immune and stress responses in utero and during suckling in the short-term and up to 14 days post-weaning. However, more research is needed to optimize this strategy.

Social status and housing factors affect reproductive performance of pregnant sows in groups.

Group-housing systems for pregnant sows are considered a welfare-promoting alternative to the individual stall. A major concern associated with pregnant sows housed in group pens is increased aggression at mixing and at feeding, which may cause chronic stress among some of the sows in the group due to low feed intake and social stress. Prolonged activation of the stress axis, based on elevated cortisol levels, may inhibit or impair reproductive success via disruption of the reproductive axis. Mixing sows into groups shortly after insemination evokes a stress response, which may affect fertilization and implantation due to sustained, elevated cortisol levels that disrupt reproductive processes. Yet, most studies reported minimal effects of group housing sows during pregnancy on reproduction or cortisol-related stress response. Differences between housing systems-in terms of group size, floor-space allowance, feeding system, and genetics-could account for these unexpected results. Indeed, interrupted feed intake, especially in early pregnancy, and sustained aggression in late pregnancy are two unfavorable social stresses that deserve special attention in order to achieve good reproductive performance. Unfortunately, most studies do not consider other factors, such as social rank and parity, which may interactively affect reproductive success and aggressive behavior of sows, especially in group-pen systems.

Heat and social rank impact behavior and physiology of PRRS-virus-infected pigs.

Changes in thermal environment can invoke a stress response in pigs, which in turn can potentially impact their immune system and disease susceptibility. We investigated effects of heat stress and social rank on behavior, immune responsiveness, and performance of pigs challenged with porcine reproductive and respiratory syndrome (PRRS) virus. Sixty-four 7-week-old PRRS-naïve pigs were assigned to each of four experimental treatments consisting of a 2 x 2 factorial design: PRRS (PRRS- or PRRS+) and environmental temperature (24 degrees C or 32 degrees C). Blood samples were taken prior to and at days 7 and 14 post-inoculation, and alveolar macrophages were collected via bronchoalveolar lavage at day 14. Total white blood cell counts, natural killer cytotoxicity, macrophage numbers, macrophage subpopulations, and performance measures were all significantly affected by social rank, heat stress, and/or infection status of the pig. Heat stress and PRRS status also significantly influenced the amount of time pigs spent lying with or without contacting another animal. Cortisol and various immune measures were also affected by PRRS status. These results show not only that intranasal inoculation with PRRS virus affects physiological, behavioral, and performance measures in growing pigs, but that social rank influences pigs' immune responsiveness to PRRS as well. Moreover, heat stress does not have additive negative impact on physiological or performance traits in pigs challenged with PRRS virus.

Differential dose effects of central CRF and effects of CRF astressin on pig behavior.

The elevation of central corticotropin releasing factor (CRF) causes an increase in behavioral activity, including increases in overall activity and oral/nasal/facial (ONF) chewing-rooting-rubbing behaviors in the pig and similar behaviors in other species. This study detailed changes in the frequency, duration and sequences of behaviors after central administration of vehicle or porcine CRF (pCRF at 0.5, 5.0, 50 and 150 microg). A sequential analysis described the complex behaviors induced in a dose-dependent fashion by central pCRF. The frequency and duration of ONF behaviors were significantly increased among pigs receiving 50 microg of pCRF. For behaviors such as ONF, 50 microg represented a breakpoint at which the frequency and duration of single behaviors increased. Pigs receiving 50 microg of pCRF were considerably more active and exhibited more ONF behaviors than did pigs receiving lower doses. The highly sensitive sequential analysis revealed that very low doses of central pCRF induced subtle changes in sequences of behaviors. Low doses of central pCRF (0.5 microg) induced fear-related behavioral sequences that included ONF behaviors alternating with periods of inactivity. Central injection of astressin, a CRF receptor antagonist, blocked many, but not all, of CRF-induced behaviors. Compared with saline-injected control pigs, central pCRF increased general activity, ONF, fear-related freezing and sham chewing behaviors. When pCRF was given following astressin, fear-related freezing behaviors were not different compared with pigs receiving saline. However, pigs given astressin plus pCRF showed elevated sham chewing compared with saline-injected control pigs, as did pigs receiving intracerebroventricular (ICV) pCRF. These data indicate that central pCRF activates brain mechanisms associated with hyperactivity, ONF and fear-related behaviors, whereas other behaviors induced by pCRF may be nonspecifically mediated by CRF. Astressin antagonized some, but not all, pCRF-induced behaviors. This model represents the induction of hyperactivity and stereotyped behaviors, which may represent a new model for the study of mania or obsessive-compulsive behaviors.