Lipopolysaccharide (LPS) from Gram-negative bacteria induces an immune response and impairs reproduction through suppression of gonadotropin releasing hormone (GnRH), subsequently luteinizing hormone (LH) secretion. While there is evidence that acute inflammation inhibits kisspeptin, little is known about the impact of chronic inflammation on this key reproductive neuropeptide in livestock species. Thus, we sought to examine a central mechanism whereby LPS suppresses LH secretion in sheep. Twenty wethers were randomly assigned to one of five treatment groups: control (CON; n=4), single acute IV LPS dose (SAD; n=4), daily acute IV LPS dose (DAD; n=4), daily increasing IV LPS dose (DID; n=4), and chronic subcutaneous LPS dose (CSD; n=4). On Days 1 and 7, blood samples were collected every 12 minutes for 360 minutes using jugular venipuncture. Following blood collection on Day 7, all animals were euthanized, brain tissue was perfused with 4% paraformaldehyde, and hypothalamic blocks were removed and processed for immunohistochemistry. On Day 1, LH pulse frequency was significantly lower (p=0.02) in SAD (0.25 ± 0.1 pulses/hour), DAD (0.25 ± 0.1 pulses/hour), DID (0.35 ± 0.1 pulses/hour), and CSD (0.40 ± 0.1 pulses/hour) compared to CON (0.70 ±0.1 pulses/hour). On Day 7, only DID animals (0.35 ± 0.1 pulses/hour) had significantly lower (p=0.049) LH pulse frequency compared to controls (0.85 ± 0.1 pulse/hour). Furthermore, only DID animals (33.3 ± 10.9 cells/section/animal) had significantly fewer (p=0.001) kisspeptin-immunopositive cells compared to controls (82.6 ± 13.6 cells/section/animal). Taken together, we suggest that daily increasing doses of LPS is a powerful inhibitor of kisspeptin neurons in young male sheep and a physiologically relevant model to examine the impact of chronic inflammation on the reproductive axis in livestock.

α-1-Acid glycoprotein (AGP) is an acute-phase protein that may suppress dry matter intake (DMI), potentially by acting on the leptin receptor in the hypothalamus. Our objectives were to characterize plasma AGP concentration and associations with DMI during the transition period, and to determine the utility of AGP to identify or predict cows with low DMI. Plasma samples (n = 2,086) from 434 Holstein cows in 6 studies were analyzed on d −21, −13 ± 2, −3, 1, 3, 7 ± 1, 14 ± 1, and 21 ± 1 relative to parturition. A commercially available ELISA kit specific for bovine AGP was validated, and 2 internal controls were analyzed on each plate with interplate variation of 15.0 and 17.3%, respectively. Bivariate analysis was used to assess the relationship between AGP and DMI. For significant associations, treatment(study) was added to the model, and quadratic associations were included in the model if significant. Plasma AGP concentration (±SEM) increased from 213 ± 37.3 μg/mL on d −3 to 445 ± 60.0 μg/mL on d 14. On d 3, AGP was associated negatively with DMI in a quadratic manner for wk 1 and wk 2 and linearly for wk 3. Day 7 AGP was associated negatively with DMI in a quadratic manner for wk 2 and linearly for wk 3. Similarly, d 14 AGP was negatively associated with DMI for wk 3 and wk 4. As d 3 AGP concentration increased over the interquartile range, a calculated 1.4 (8.5%), 0.5 (2.7%), and 0.4 (1.9%) kg/d reduction in predicted DMI was detected during wk 1, 2, and 3, respectively. Using bivariate analysis, d 3 AGP explained 10% of the variation in DMI during wk 1. We explored the clinical utility of d 3 AGP to diagnose low DMI, defined as wk 1 DMI >1 standard deviation below the mean. Receiver operating characteristic analysis identified a threshold of 480.9 μg/mL, providing 76% specificity and 48% sensitivity (area under the curve = 0.60). Limited associations occurred between AGP and blood biomarkers; however, AGP was associated with plasma haptoglobin concentration postpartum and incidence of displaced abomasum, retained placenta, and metritis. These results demonstrate a negative association between plasma AGP concentration and DMI in early-postpartum dairy cows, although its diagnostic performance was marginal. Further investigation into whether AGP directly suppresses DMI in dairy cattle is warranted.

Kisspeptin (KP) is a neuropeptide integral in regulating puberty and gonadotropin releasing hormone. Compound 6 (C6), a KP analog, is more potent in vitro, has a longer half-life, and may have greater therapeutic applications than KP. To determine the acute and subacute effects of KP and C6 on serum concentrations of luteinizing hormone (LH), follicle stimulating hormones (FSH), and testosterone (T), prepubertal bull calves [12.1 ± 1.1 (SD) weeks of age; 91.2 ± 10.8 kg BW] were assigned to one of three treatment groups [Saline (n = 4), KP (n = 4; 20 nmoles), or C6 (n = 4; 20 nmoles). Treatments were administered intramuscularly once daily for four consecutive days. Blood samples were collected every 15 min for 6 h immediately following treatment administration on Day 1 (acute) and Day 4 (subacute). Serum concentrations of LH, FSH, and T were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment × time interaction during Day 1 (P < 0.0001) and Day 4 (P = 0.02) such that LH concentrations were greatest following administration of C6 (albeit diminished during Day 4). Number of LH pulses were least (P = 0.02) and LH nadirs were highest (P = 0.04) following administration of C6 (P = 0.02). There was no effect of treatment (P = 0.95) or treatment × time interaction (P = 0.10) on serum FSH concentrations during Day 1. During Day 4 FSH concentrations (P = 0.02) and number of FSH pulses (P = 0.02) were least following administration of C6. There was no effect of treatment (P = 0.33), time (P = 0.19) or treatment × time interaction (P = 0.44) on T concentrations. In conclusion, acute and subacute C6 increased LH concentrations and subacute C6 decreased FSH concentrations and pulse parameters. Despite suppression of FSH with subacute daily administration of C6, altered frequency and timing of treatment with KP analogs may have application to affect the onset of puberty in livestock.

Central administration of α-1-acid-glycoprotein (AGP) induces an increase in rectal temperature in ewes. To determine if AGP-induced fever in sheep is dependent on prostaglandin synthesis, non-lactating, non-pregnant, adult (≥1 yr of age) mixed breed black face ewes (n = 19) weighing 85.4 ± 19.4 (SD) kg were ovariectomized and surgically implanted with a cannula into a lateral ventricle of the brain. Ewes were kept indoors in individual pens with a 12-hour light/dark photoperiod and approximately 22–24℃. Ewes had ad libitum access to water and a diet calculated to meet their requirements. Ewes were intravenously administered either 0 (SAL) or 2.2 mg/kg BW flunixin meglumine (FLU; PrevailTM; VetOne Meridian, ID; a cyclooxygenase inhibitory non-steroidal anti-inflammatory drug) 30 minutes prior to receiving either 0 (SAL) or 25 mg AGP (~0.3 µg/kg BW; from bovine plasma; Sigma Aldrich Co. Saint Louis, MO) administered in 500 µL of sterile, nonpyrogenic, isotonic, 0.9% sodium chloride into the lateral ventricle. Rectal temperature was determined at -72, -48, -24, -2, 0, 2, 4, 6, 8, 12, and 24 h relative to AGP treatment. Data were analyzed using procedures for repeated measures with JMP software (version 10.0.0; SAS Inst. Inc., Cary, NC) and tested for effects of AGP treatment, FLU treatment, time, and interactions. There was an effect of central AGP administration (P = 0.0063) and AGP by time interaction (P < 0.001) on rectal temperature such that ewes treated centrally with AGP had greater rectal temperatures at 2, 4, 6, 8, and 12 h relative to ewes treated centrally with SAL. There was no effect of intravenous FLU, FLU by time interaction, FLU by AGP, or AGP by FLU by time interaction (P > 0.17). Thus, central AGP administration increases rectal temperature in sheep by a mechanism independent of prostaglandin synthesis.

l-Citrulline can influence circulating concentrations of arginine and thus enhance nitric oxide (NO) generation to increase blood flow to tissue. This experiment was conducted to determine the dose response of horses to oral l-citrulline administration. The day before blood collection, mature gelding American Quarter Horses (n = 5; 521 ± 27 kg BW) were sedated with xylazine (0.5 mg/kg IV) and fitted with an IV catheter in the jugular vein. The horses were then placed in individual stalls and allowed water and bermudagrass hay ad libitum. The following day, 1 h prior to treatment administration, hay was removed. Blood samples were collected via jugular catheter at −60, −30, 0, 30, 60, 90, 120, 240, 360, 720, and 1,440 min relative to treatment administration. At time 0, horses received treatments of 0 (water), 0.018 (low), 0.09 (medium), or 0.18 g/kg (high) of l-citrulline dissolved in 200 mL of distilled water orally via nasal gastric tube, and hay was returned. Plasma was harvested and frozen at −20°C for analysis of l-citrulline and arginine concentrations in circulation by HPLC as well as nitrate and nitrite levels by colorimetric assay (Cayman Chemical, Ann Arbor, MI). Horses were administered a 7-d washout period, and the study was repeated until all horses received all treatments. Data were tested for effects of replication, dose, time, and dose × time interaction using procedures for repeated measures with JMP software (version 10; SAS Inst. Inc., Cary, NC). Circulating concentrations of l-citrulline were greater with the high dose compared with those of the water or low dose (P < 0.04). Circulating concentrations of arginine were greater with the high and medium dose than with the water or low dose (P < 0.01). There was also a dose × time effect on circulating concentrations of arginine such that the medium dose had greater arginine concentrations than the water at 120 min as well as the water and low dose at 240, 360 and 720 m. The high dose had greater arginine concentrations than the water and low dose at 120, 360, and 720 min. There was no effect of dose or dose × time interaction on plasma concentration of nitrate and nitrites (P > 0.56). These results indicate oral l-citrulline administration can alter circulating concentrations of both l-citrulline and arginine in horses.

Leukemia inhibitory factor (LIF) has been suggested to function as a potent inhibitor of feed intake in rodents. In sheep, intravenous injection of lipopolysaccharide (LPS) resulted in an increase in gene expression for LIF in the arcuate nucleus ( < 0.01). In the same experiment, agouti related protein (AgRP) expression was elevated ( < 0.05) but there were no effects on proopiomelanocortin expression. Another group of sheep were provided intracerebroventricular (ICV) injections of LIF at 250, 500, 1,000, and 2,500 ng per sheep. Cumulative feed intake was inhibited by the 1,000- and 2,500-ng doses at 8 and 10 h after ICV injection ( < 0.03). All doses of LIF elevated temperature above 40°C, indicating a fever. When AgRP was intracerebroventricularly injected before LIF, there was no effect of LIF to reduce feed intake, suggesting the LIF inhibition of feed intake is consistent with the concept that the effect is mediated by the melanocortin-4 receptor. In an experiment to determine whether endocrine and metabolic effects of LIF were similar to reported effects of LPS, sheep were intracerebroventricularly injected with 2,500 ng LIF, and blood samples were collected at 10-min intervals for 6 h for assay of LH, samples from the first 3 h were assayed for GH, and samples at 30-min intervals were assayed for glucose and free fatty acids. The effect of treatment and treatment × time interaction was significant, indicating elevated plasma free fatty acids ( < 0.03 and < 0.001, respectively) and glucose ( < 0.01 and < 0.0001, respectively). There was also a treatment × time interaction on circulating concentrations of LH such that LIF caused LH to decrease ( < 0.0001). Additionally, there was a tendency for LIF treatment to increase circulating concentrations of GH (P = 0.0874). The effects of LIF on feed intake and other parameters was similar to the effects of LPS and leads to a hypothesis that LIF expression in response to LPS may be a component of the mechanism for feed intake inhibition and perhaps for changes in selected hormone and metabolites in disease models.

A large percentage of students entering undergraduate animal science programs have a desire to become a veterinarian. For example, at Berry College, a private school in northwest Georgia with an animal science program, 81 ± 0.6% of the incoming freshmen (n = 194) for the last 2 yr have indicated a desire to become a veterinarian. Animal science is an appropriate undergraduate major for students interested in veterinary science, and animal science programs should help those students to successfully obtain those goals, however many students come from a background with little experience or knowledge of opportunities for a career working with animals other than veterinary medicine. At Berry College, 69 ± 1.5% of the incoming freshmen for the last 2 yr reported coming from an urban or suburban area, and only 14 ± 1.9% reported living on a farm. While more freshmen report being from a farm at Iowa State University (29.15% in 2014 and 42% in 2015), the trend is still similar. These urban and non-farm students have a desire to work with animals, but limited knowledge of the opportunities available as indicated by the fact that 25 ± 2.9% of the incoming freshmen at Berry College indicated having no experience working with their primary animal of interest. To help students further define where their passion may lie, steps have been implemented in the Department of Animal Science at Iowa State University to inform incoming and freshmen students about the diversity of careers in animal science. During campus visits with high school students and families, the vast array of opportunities surrounding careers in Animal Science are discussed briefly. More discussion follows during Freshmen Orientation, and also during ANS 110: Orientation in Animal Science. Freshmen and transfer students enrolled in ANS 110 were asked to indicate their interest in various careers at the beginning and again at the end of the semester. At the beginning of the semester, 62% (315 responding) indicated that veterinary school was their primary interest. The last week of class, only 43% (296 responding) responded that this was still at the top of their interests. Even more interesting was the increased interest in graduate school (8% in September vs. 17% in November). Identifying interests earlier in their collegiate career will allow students to take advantage of internships and other experiences more closely related to their interest.

Ghrelin is a hormone that stimulates feed intake and regulates energy homeostasis. A link has been observed in sheep, in which simulated feedings at scheduled meal times resulted in an increase in ghrelin concentrations. The present study sought to characterize the effect of feeding cues outside of scheduled meal times on circulating ghrelin concentrations in sheep. Katahdin wethers (age 201 ± 4.9 d; weight 35 ± 1.2 kg) were not offered feed (CONT; = 5), offered 275 g of feed (FED; = 5), or fitted with a muzzle and offered 275 g of feed (SHAM; = 5) during the sampling period, which began 2.5 h after normally scheduled daily feeding time. Blood samples were collected via jugular catheter every 15 min for 2.5 h. Feed was offered for 15 min 0.5 h after the start of blood sampling. The CONT samples were collected on d 1, and FED and SHAM samples were collected on d 2. The active ghrelin present in the plasma was then analyzed by RIA. After the Shapiro-Wilk W goodness of fit test demonstrated that 1 SHAM wether was an outlier and it was removed, data were tested for effect of treatment (FED, SHAM, or CONT), time, and treatment × time interaction using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was no treatment or time effect ( > 0.05); however, there was a treatment × time interaction on plasma ghrelin concentrations ( = 0.0028) such that ghrelin concentrations in SHAM wethers were greater than in CONT wethers 15, 60, and 90 min after feeding, whereas ghrelin concentrations in SHAM wethers were greater than those in FED wethers 30, 60, 90, and 120 min after feeding ( < 0.05). Within the SHAM treatment, ghrelin concentrations were greater at 15 min than at -30 min. Moreover, ghrelin concentrations within the FED treatment were greater at -30 min than at 30, 45, 60, 90, 105, and 120 min and at -15 min than at 15 through 120 min. The area under the curve representing circulating concentrations of ghrelin in CONT, FED, and SHAM treatments, determined using the trapezoidal method, yielded a treatment effect with a tendency toward significance ( = 0.0866). These results indicate plasma ghrelin concentrations in scheduled meal-fed wethers are elevated following visual, olfactory, and auditory feeding cues outside of scheduled feeding times.

Bovine anaplasmosis, caused by Anaplasma marginale, is the most prevalent tick-transmitted disease of cattle worldwide and a major obstacle to profitable production in the U.S. Several serological assays such as complement fixation (CF), card agglutination, and competitive enzyme-linked immunosorbent assay (cELISA) have been used in the detection of anaplasmosis carriers. The CF and card agglutination tests are not considered reliable due to low diagnostic sensitivities (<2 0% and 67%, respectively). Commercially available major surface protein-5 (MSP-5) epitope-based cELISA is more reliable with high sensitivity (99%) and specificity (89%). Recently, maltose binding protein included as fusion protein in the recombinant MSP-5 used in the commercially available cELISA was identified as the source of some false-positive results. A new cELISA test was developed to improve diagnostic specificity by reducing false positive reactions due to maltose binding protein antibodies and other non-specific antibodies in bovine sera. The objective of this study was to compare results generated using the current and new cELISA tests and real-time RT-PCR to provide veterinarians with up to date information regarding the most appropriate test to use for anaplasmosis diagnosis.

Bovine anaplasmosis, caused by Anaplasma marginal, is the most prevalent tick-transmitted disease of cattle worldwide and a major obstacle to profitable production in the U.S. The introduction of anaplasmosis into a naive herd can result in a reduced calf crop and increased cull and mortality rates in infected adult cattle. The cost of anaplasmosis to the US beef industry is estimated to be over $300 million annually. Control of anaplasmosis in the U.S. is predicated on biosecurity and administration of antimicrobials both of which require knowledge of regional prevalence for implementation to be successful. The last reported prevalence of anaplasmosis in cattle in the southern U.S. ranged from 2% to 24%. However, the test used to determine the prevalence, complement fixation, is no longer considered reliable. Therefore, true prevalence of anaplasmosis in this region is likely much higher than previously reported.

Nutrient availability is a determinant of reproductive success. It is well known that inadequate nutrition results in reproductive failure due to a number of factors including delay of puberty or anoestrous in post-pubertal animals. The lack of nutrients is detected primarily by changes in circulating nutrient molecules and hormones and communicated directly or indirectly to the hypothalamus and brain stem for integration. The general effect is that low nutrition leads to increased appetite stimulation and reduced reproductive performance. When nutrition is adequate, the reverse is true. Both aspects will be the focus of this review. One result of the lack of nutrients is a reduction in luteinizing hormone (LH) concentrations and pulse frequency. Nutrient signals, such as glucose availability, hormonal signals, such as insulin and leptin, and neuroendocrine signals, such as neuropeptide Y and corticotropin-releasing hormone, have been clearly demonstrated to interact to produce changes in LH and reproductive success. Other signals, such as fatty acids, ghrelin, agouti-related peptide, melanin-concentrating hormone, orexin, melanocyte-stimulating hormone, kisspeptin, neurokinin, dynorphin and gonadotropin inhibitory hormone may also play a role in integrating nutrition and reproduction. This review will focus on the major features of the reciprocal control of appetite and reproduction in sheep.

Electroejaculation is a reliable method of obtaining a semen sample for a bull breeding soundness examination, but is sometimes regarded as painful. Substance P is a neuropeptide involved in the integration of pain, stress, and anxiety. We hypothesized that substance P is a measure of pain in bulls following electroejaculation. The specific objective was to compare vocalization and plasma concentrations of cortisol, progesterone, and substance P immunoreactivity in bulls following electroejaculation. Nine Angus bulls (501.9 ± 14.3 kg) were used. Blood samples were collected at -60, -30, 0, 2, 10, 20, 30, 45, 60, 75, 90, 120 min relative to treatment. At Time 0, bulls were subject to electroejaculation, rectal probe insertion without electroejaculation, or no manipulation. Treatments were administered contemporaneously to three bulls. Treatments were repeated weekly until each bull had received each treatment in a 3 × 3 Latin square design. More bulls (P = 0.0147) in the electroejaculation group vocalized (5 of 9 bulls; 55.6%) when compared to controls (0 of 9 bulls; 0%). Mean plasma cortisol and progesterone concentration following electroejaculation in bulls were higher (P < 0.05) than concentrations in probed and control bulls through the 45 min sample. However, mean plasma substance P concentration following electroejaculation in bulls (77.2 ± 17.2 pg/mL) was not different (P = 0.6264) from probed (79.1 ± 17.2 pg/mL) or control bulls (93.4 ± 17.2 pg/mL). A significant increase in vocalization and plasma cortisol and progesterone concentrations in bulls following electroejaculation was likely owing to acute stress. However, the lack of a difference in plasma concentrations of substance P after electroejaculation was interpreted as a lack of pain associated with nociception.

Appetite is a complex process that results from the integration of multiple signals at the hypothalamus. The hypothalamus receives neural signals; hormonal signals such as leptin, cholecystokinin, and ghrelin; and nutrient signals such as glucose, FFA, AA, and VFA. This effect is processed by a specific sequence of neurotransmitters beginning with the arcuate nucleus and orexigenic cells containing neuropeptide Y or agouti-related protein and anorexigenic cells containing proopiomelanocortin (yielding the neurotransmitter α-melanocyte-stimulating hormone) or cells expressing cocaine amphetamine-related transcript. These so-called first-order neurons act on second-order orexigenic neurons (containing either melanin-concentrating hormone or orexin) or act on anorexigenic neurons (e.g., expressing corticotropin-releasing hormone) to alter feed intake. In addition, satiety signals from the liver and gastrointestinal tract signal through the vagus nerve to the nucleus tractus solitarius to cause meal termination, and in combination with the hypothalamus, integrate the various signals to determine the feeding response. The activities of these neuronal pathways are also influenced by numerous factors such as nutrients, fasting, and disease to modify appetite and hence affect growth and reproduction. This review will begin with the central nervous system pathways and then discuss the ways in which hormones and metabolites may alter the process to affect feed intake with emphasis on farm animals.