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Hypothalamic orexin neurons project to numerous brain areas, including the ventral tegmental area (VTA), which is involved in motivation and food-seeking behavior. Here we address how exogenously administered orexin-A and endogenous orexin 1 receptor (OX1R) activation in the VTA affects feeding behavior. We hypothesized that orexin-A and OX1R antagonist SB334867 delivered to the VTA, at doses that were subthreshold for effect when injected into the ventricle, would affect intake of palatable foods in multiple test situations. We first used a hedonic feeding model in which satiated rats selectively consume a high-fat diet (HFD). Intra-VTA orexin-A stimulated additional consumption of chow and increased HFD intake in this model. In ad libitum-fed rats given daily 30-min test sessions, intra-VTA orexin-A also increased intake of HFD and 0.1 M sucrose. Further analysis of licking patterns revealed that that VTA orexin-A increased meal size and licking burst size only toward the end of the meal. Consistent with this finding, a subthreshold dose of VTA orexin-A prevented intake suppression induced by gastrointestinal nutrient infusion. Surprisingly, intra-VTA orexin-A had no effect on operant responding for sucrose pellets on a progressive ratio schedule of reinforcement. A role for endogenous VTA OX1R stimulation is supported by our finding that bilateral VTA injection of the selective OX1R antagonist SB334867 suppressed 0.1 M sucrose intake. Together, our data suggest that OX1R activity in the VTA facilitates food intake, potentially by counteracting postingestive negative feedback that would normally suppress feeding later in a meal.

Phytases are important commercial enzymes that catalyze the dephosphorylation of myo-inositol hexakisphosphate (phytate) to its lower inositol phosphate (IP) esters, IP6 to IP1. Digestion of phytate by Citrobacter braakii 6-phytase deviates significantly from monophasic Michaelis-Menten kinetics. Analysis of phytate digestion using isothermal titration calorimetry (ITC) using the single injection method produced a thermogram with two peaks consistent with two periods of high enzyme activity. Continuous-flow electrospray ionization time-of-flight mass spectroscopy (ESI-ToF-MS) provided real-time analysis of phytase catalysis. It was able to show that the first two cleavage steps were rapid and concurrent but the third cleavage step from IP4 to IP3 was slow. The third (IP4 to IP3), fourth (IP3 to IP2) and fifth (IP2 to IP1) cleavages were effectively sequential due to the preferred association of the more phosphorylated species with the phytase catalytic site. This created a bottleneck during the cleavage of IP4 to IP3 until the point at which IP4 was exhausted and was followed by the rapid cleavage of IP3 to IP2, which was observed as the second peak in the ITC thermogram. This work illustrates the importance of an orthogonal approach when studying non-specific or complex enzyme catalyzed reactions.

A total of 300 nursery pigs (initially 5.9 ± 0.05 kg BW) were used in a 42-d growth trial to evaluate the effects of feeding a therapeutic level of chlortetracycline (CTC) with or without direct fed microbials (DFM) on growth performance and antimicrobial resistance (AMR) of fecal Escherichia coli. CTC is a broad-spectrum in-feed antibiotic commonly used in the swine industry. Weaned pigs (~21 d of age) were allotted to pens based on initial BW and fed a common starter diet for 4 d. Pens were then blocked by BW and allotted to dietary treatments in a completely randomized block design. Dietary treatments were arranged in a 2 × 3 factorial consisting of combinations of CTC (none vs. 400 mg/kg from days 0 to 42) and DFM (0 vs. 0.05% DFM 1 vs. 0.05% DFM 2). Fecal samples were collected from three randomly selected pigs from each pen on days 0, 21, and 42 for E. coli isolation and AMR determination. Overall, pigs fed diets containing CTC had improved (P < 0.001) ADG, ADFI, and BW compared to those not fed CTC with no evidence for any effect of either DFM 1 or DFM 2. Regardless of CTC, inclusion of DFM 2 in diets improved (P < 0.05) ADFI from days 0 to 14 and on day 14 BW compared to diets that did not include DFM 2. The addition of CTC with or without DFMs to nursery pig diets increased (P < 0.05) the probability of AMR to tetracycline and ceftiofur of fecal E. coli isolates, but this resistance generally decreased (P < 0.05) over time. A decrease (P < 0.05) in AMR to ampicillin and tetracycline (TET) throughout the trial was observed, while resistance to ceftriaxone decreased (P < 0.020) from days 0 to 21 and increased from days 21 to 42 amongst dietary treatments regardless of CTC or DFM inclusion in the diet. A CTC × DFM × day interaction (P < 0.015) was observed for streptomycin, whereby from days 21 to 42 AMR increased in diets containing either CTC or DFM 1 alone, but the combination decreased resistance. There was no evidence for any effect of DFMs on AMR of fecal E. coli isolates to any other antibiotics evaluated. In conclusion, therapeutic levels of added CTC with or without DFM inclusion improved nursery pig performance, but increased AMR of fecal E. coli isolates to TET and ceftiofur. A moderate improvement in intake and day 14 BW was observed when DFM 2 was included in the diet with or without CTC, but, except for streptomycin, there was no evidence that added dietary DFMs affected resistance of fecal E. coli to antibiotics.

Three studies evaluated the effects of added dietary salt on growth performance of pigs weighing 7 to 10, 11 to 30, and 27 to 65 kg. In experiment 1, 325 pigs were used with 5 pigs per pen and 13 pens per treatment. Pigs were fed a diet (0.39% Na and 0.78% Cl) for 7 d after weaning, then randomly assigned to diets with either 0, 0.20, 0.40, 0.60, or 0.80% added salt for 14 d. All diets were corn-soybean meal-based with 10% dried whey. Calculated Na concentrations were 0.11, 0.19, 0.27, 0.35, and 0.43% and calculated Cl concentrations were 0.23, 0.35, 0.47, 0.59, and 0.70%, respectively. Increasing salt increased (linear, P < 0.05) average daily gain (ADG) and gain to feed ratio (G:F). For ADG, the linear, quadratic polynomial (QP), and broken-line linear (BLL) models were competing with the breakpoint for the BLL at 0.59% salt. For G:F, the BLL reported a breakpoint at 0.33% while the QP indicated maximum G:F at 0.67% added salt. In experiment 2, 300 pigs were used in a 34-d trial with 5 pigs per pen and 12 pens per treatment. Pigs were weaned at 21 d of age and fed a phase 1 diet (0.50% Na and 0.67% Cl) for 11 d and then a phase 2 diet (0.35% Na and 0.59% Cl) for 14 d. Then pens of pigs were randomly assigned to corn-soybean meal-based diets containing 0.20, 0.35, 0.50, 0.65, or 0.80% added salt. Calculated dietary Na concentration were 0.10, 0.16, 0.22, 0.28, and 0.34% and calculated Cl concentrations were 0.23, 0.32, 0.41, 0.50, and 0.59%, respectively. Overall, ADG and G:F increased (quadratic, P < 0.07) with increasing added salt. For ADG, the QP and BLL had similar fit with the breakpoint for BLL at 0.51% added salt. For G:F, the BLL model predicted a break point at 0.35% added salt. In experiment 3, 1,188 pigs were used in a 44-d study with 27 pigs per pen and 11 pens per treatment. Pens of pigs were randomly assigned to corn-soybean meal-based diets containing 0.10, 0.33, 0.55, or 0.75% added salt. Calculated dietary Na concentrations were 0.10, 0.19, 0.28, and 0.36% and calculated Cl concentrations were 0.23, 0.36, 0.49, and 0.61%, respectively. Overall, there was no evidence to indicate that added salt above 0.10% of the diet affected growth. In conclusion, the BLL models suggested to maximize ADG for 7 to 10 and 11 to 30 kg pigs was 0.59% (0.34% Na and 0.58% Cl) and 0.51% added salt (0.22% Na and 0.42% Cl), respectively. There was no evidence that growth of 27 to 65 kg pigs was improved beyond 0.10% added salt (0.11% Na and 0.26% Cl).

Formaldehyde-based feed additives are approved in the US for Salmonella control and reducing bacterial contamination in animal feed. However, we hypothesize formaldehyde inclusion in swine diets may influence gut microbial composition due to its antimicrobial properties which might negatively influence microbial populations and pig growth performance. Also, formaldehyde inclusion in diets is known to reduce the dietary availability of amino acids. Therefore, our study was conducted to characterize if the effects of feed formaldehyde-treatment are due to influences on microbial population or diet amino acid (AA) sources. Dietary treatments were arranged in a (2 × 2) + 1 factorial with formaldehyde treatment (none vs. 1000 ppm formaldehyde) and crystalline AA inclusion (low vs. high) with deficient AA content plus a positive control diet to contain adequate AA content without dietary formaldehyde. Treating diets with formaldehyde reduced growth rate (P = 0.001) while the AA inclusion had no evidence of impact. Formaldehyde reduced feed bacterial content and altered fecal microbial communities (P

A total of 300 nursery pigs (initially 5.9 ± 0.05 kg BW) were used in a 42-d growth trial to evaluate the effects of feeding a therapeutic level of chlortetracycline (CTC) with or without direct fed microbials (DFM) on growth performance and antimicrobial resistance (AMR) of fecal Escherichia coli. CTC is a broad-spectrum in-feed antibiotic commonly used in the swine industry. Weaned pigs (~21 d of age) were allotted to pens based on initial BW and fed a common starter diet for 4 d. Pens were then blocked by BW and allotted to dietary treatments in a completely randomized block design. Dietary treatments were arranged in a 2 × 3 factorial consisting of combinations of CTC (none vs. 400 mg/kg from days 0 to 42) and DFM (0 vs. 0.05% DFM 1 vs. 0.05% DFM 2). Fecal samples were collected from three randomly selected pigs from each pen on days 0, 21, and 42 for E. coli isolation and AMR determination. Overall, pigs fed diets containing CTC had improved (P < 0.001) ADG, ADFI, and BW compared to those not fed CTC with no evidence for any effect of either DFM 1 or DFM 2. Regardless of CTC, inclusion of DFM 2 in diets improved (P < 0.05) ADFI from days 0 to 14 and on day 14 BW compared to diets that did not include DFM 2. The addition of CTC with or without DFMs to nursery pig diets increased (P < 0.05) the probability of AMR to tetracycline and ceftiofur of fecal E. coli isolates, but this resistance generally decreased (P < 0.05) over time. A decrease (P < 0.05) in AMR to ampicillin and tetracycline (TET) throughout the trial was observed, while resistance to ceftriaxone decreased (P < 0.020) from days 0 to 21 and increased from days 21 to 42 amongst dietary treatments regardless of CTC or DFM inclusion in the diet. A CTC × DFM × day interaction (P < 0.015) was observed for streptomycin, whereby from days 21 to 42 AMR increased in diets containing either CTC or DFM 1 alone, but the combination decreased resistance. There was no evidence for any effect of DFMs on AMR of fecal E. coli isolates to any other antibiotics evaluated. In conclusion, therapeutic levels of added CTC with or without DFM inclusion improved nursery pig performance, but increased AMR of fecal E. coli isolates to TET and ceftiofur. A moderate improvement in intake and day 14 BW was observed when DFM 2 was included in the diet with or without CTC, but, except for streptomycin, there was no evidence that added dietary DFMs affected resistance of fecal E. coli to antibiotics.

Newborn pigs (n = 324; 1.6 kg BW) were used in an 19-d study evaluating the effects of Fe injection timing after birth on preweaned pig performance and blood criteria. A total of 27 litters were used, with the number of pigs per sow equalized on each day of farrowing. Two d after farrowing, all piglets were weighed, and six barrows and six gilts within each litter were allotted to 1 of 6 treatments in a CRD. Treatments consisted of a negative control receiving no Fe injection or 200 mg of injectable Fe (Gleptoforte, Ceva Animal Health, Lenexa, KS) provided on d 2, 4, 6, 8, or 10 after farrowing. Piglets were weighed and bled on d 2, 12, and 21 after birth to determine growth performance and blood Fe status. Overall, increasing the age that piglets received a 200 mg Fe injection until 4 or 6 d after birth tended to increase (quadratic; P = 0.065) ADG (Table 1). Not providing an Fe injection tended to decrease (P = 0.070) overall ADG and decreased (P = 0.0003) d 21 BW compared to all other treatments. Significant treatment×day interactions (P < 0.001) were observed for hemoglobin (Hgb) and hematocrit (Hct). The interactions occurred because pigs injected with 200 mg of Fe on d 2, 4, 6, or 8 after birth had increasing values until d 21 after birth, while pigs receiving a 200 mg Fe injection on d 10 after birth had decreasing values to d 12 then increasing values to d 21. Pigs not provided an Fe injection after birth had decreasing values to d 21. These results suggest that providing a 200 mg Fe injection on d 4 or 6 after farrowing provided the greatest preweaning growth performance and blood Fe status until weaning.

Newborn pigs (n = 336; 1.7 kg BW) were used in a 21-d study evaluating the effects of increasing injectable Fe on preweaning pig performance and blood Fe status. A total of 28 litters were used and at processing (d 3 after farrowing) all piglets were weighed and six barrows and six gilts/litter were allotted to 1 of 6 treatments in a CRD. Treatments consisted of a negative control receiving no Fe injection and increasing injectable Fe (Gleptoforte, Ceva Animal Health, Lenexa, KS) to achieve 50, 100, 150, 200-mg, or 200-mg plus a 100-mg injection on d 11 post-farrowing. Piglets were weighed and bled on d 3, 11, and 21 of age to determine growth performance and blood Fe status. Preweaned pig growth data and hematological criteria were evaluated using individual pig as the experimental unit with hematological criteria analyzed as a repeated measure. Increasing injectable Fe up to 100-mg improved (quadratic; P < 0.05) ADG and d 21 BW with no further improvement thereafter (Table 1).There were no evidence of differences (P > 0.10) between the 200-mg and 200 + 100-mg treatments for growth. Significant treatment×day interactions (P < 0.001) were observed for hemoglobin (Hgb) and hematocrit (Hct). The interactions were the result of decreased values for pigs receiving no Fe injection or an Fe injection of 100-mg or less, while pigs receiving an Fe injection greater than 100-mg had increased values at d 21. Pigs receiving the 200 + 100-mg treatment had increased (P < 0.05) Hgb and Hct values compared to pigs receiving a single 200-mg Fe injection on d 21. Results suggest that a 100-mg Fe injection is sufficient for growth performance during the preweaning phase, but an Fe injection greater than 100-mg is needed to maximize blood criteria. An extra 100-mg Fe injection at d 11 did not influence growth performance but does increase Hgb and Hct at weaning.

Hindbrain glucagon-like peptide 1 (GLP-1) neurons project to numerous forebrain areas, including the lateral septum (LS). Using a fluorescently labeled GLP-1 receptor (GLP-1R) agonist, Exendin 4 (Ex4), we demonstrated GLP-1 receptor binding throughout the rat LS. We examined the feeding effects of Ex4 and the GLP-1R antagonist Exendin (9–39) (Ex9) at doses subthreshold for effect when delivered to the lateral ventricle. Intra-LS Ex4 suppressed overnight chow and high-fat diet (HFD) intake, and Ex9 increased chow and HFD intake relative to vehicle. During 2-h tests, intra-LS Ex9 significantly increased 0.25 M sucrose and 4% corn oil. Ex4 can cause nausea, but intra-LS administration of Ex4 did not induce pica. Furthermore, intra-LS Ex4 had no effect on anxiety-like behavior in the elevated plus maze. We investigated the role of LS GLP-1R in motivation for food by examining operant responding for sucrose on a progressive ratio (PR) schedule, with and without a nutrient preload to maximize GLP-1 neuron activation. The preload strongly suppressed PR responding, but blockade of GLP-1R in the intermediate subdivision of the LS did not affect motivation for sucrose under either load condition. The ability of the nutrient load to suppress subsequent chow intake was significantly attenuated by intermediate LS Ex9 treatment. By contrast, blockade of GLP-1R in the dorsal subdivision of the LS increased both PR responding and overnight chow intake. Together, these studies suggest that endogenous activity of GLP-1R in the LS influence feeding, and dLS GLP-1Rs, in particular, play a role in motivation.