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Antibiotics have traditionally been used for growth promotion in the pork industry; however, their use in animal feed has recently been limited because of human health concerns. The intestinal microbiota plays an important role in mediating many physiological functions such as digestion and animal growth. It was hypothesized that use of antibiotics as growth promotants and subsequent variations in intestinal microbiota induce significant changes in the intestinal glycoconjugate composition, which ultimately affects animal growth and disease susceptibility. The aim of this study was to characterize the lectin binding profiles of the ileum of weanling pigs in response to the absence of intestinal microbiota and to the use of the antibiotic chlortetracycline as growth promotant. Eighteen half-sib piglets obtained by cesarean section were divided into 3 treatment groups (n = 6) and maintained as control, antibiotic-fed, and gnotobiotic piglets until 5 wk of age. The glycoconjugate composition of the ileal tissues was examined by lectin histochemistry. Lycopersicon esculentum lectin, Jacalin, Pisum sativum agglutinin, Lens culinaris agglutinin (LCA), and Sambucus nigra lectin showed significant differences (P < 0.05) in binding intensities on the dome and villous epithelium between the treatment groups. Griffonia simplicifolia lectin I, Glycine maxi agglutinin, and Arachis bypogea agglutinin exhibited differences (P < 0.05) between treatment groups in lectin binding on goblet cells. Triticum vulgaris agglutinin, Pisum sativum agglutinin, and LCA showed significant differences (P < 0.05) in binding intensities on dome, corona, and follicular regions of the ileum among treatment groups of animals. Overall, ileal tissues from gnotobiotic piglets expressed significantly weaker (P < 0.05) lectin binding for many lectins compared with control and antibiotic groups. This suggests that the intestinal microbiota plays an important role in the expression of sugar moieties in the intestine. Lectins LCA, Phaseolus vulgaris Leucoagglutinin, and Maackia amurensis lectin II showed significant differences (P < 0.05) in lectin bindings between control and antibiotic-fed piglets. This indicates that chlortetracycline as a growth promotant induces biologically relevant changes in the lectin binding profile of the ileum. These findings will help in further understanding the role of the gut microbiota and the mechanisms of action of antibiotics as growth promotants in pigs. Key words: chlortetracycline, gnotobiotic, growth promotant, intestinal microbiota, lectin, pig

An experiment was conducted to evaluate the impact of lipid source on energy and lipid digestibility, and on metabolic oxidation status of nursery pigs fed diets containing 10% of soybean oil (SO), choice white grease (CWG), palm oil (PO), or 1 of 2 different sources of distillers corn oil (DCOl and DCO2). Fifty-four barrows weaned at 28-d of age were fed a common starter diet from d 1 to 7, followed by group feeding their respective experimental diets (either 100% basal or 90% basal + 10% test lipid) from d 8 to 14 to adapt the pigs to their dietary treatments and to optimize subsequent feed intake. For the next 10 d (d 15 to 24), pigs were moved to metabolism crates for continued diet adaptation and to become accustomed to the twice daily feeding regimen in the metabolism crates. Following this period, a 4-d total fecal and urine collection occurred (d 25 to 29, final BW 11.03 ± 0.51 kg) to determine apparent total tract digestibility (ATTD) of energy and lipids, and to determine the DE and ME content of each lipid source. After an overnight fast of 12 h, urine was collected for 5 h, quantified, and subsequently analyzed for thiobarbituric acid reactive substances (TBARS) and isoprostane (IsoP) concentration. Following this collection, serum was obtained and analyzed for TBARS. Soybean oil had greatest (P < 0.05) DE (9388 kcal/kg) content compared with DCOl, DCO2, CWG, PO, and SO containing 8001, 8052, 8531, 8293, and 9388 kcal/kg lipid, respectively. Digestible energy as a percentage of GE was greatest (P < 0.05) for SO when compared to the other lipid sources (P < 0.05). The ATTD of EE averaged 85.0% and varied slightly (84.4% to 85.6%) among treatments. Differences in ME among lipids were similar to that for DE, with ME values for DCOl, DCO2, CWG, PO, and SO containing 7921, 7955, 8535, 8350, and 9408 kcal/kg lipid, respectively. Metabolizable energy as a percentage of DE did not differ between lipid sources. Pigs fed the diets containing lipids had higher (P < 0.05) plasma TBARS compared to pigs fed the control diet, but no differences were noted in urinary TBARS excretion among treatments. Urinary IsoP excretion differed among treatments (P < 0.01), but was highly variable (34.0 to 104.6 pg/ml). These results indicate that DE and ME values vary among lipid sources and appear to have variable effects on metabolic oxidation measures. [ABSTRACT FROM AUTHOR]

Twenty-nine Angus yearling steers (BW=417.3 ±31.3 kg) were used in a 2X2 factorial experiment conducted over 105 d feeding period to determine the effects of Synovex-S and ractopamine on serum concentration of IGF-I, performance and carcass characteristics. Traits analyzed were ADG from 0 d to 105 d after implant (ADG1) and ADG from 70 d to 105 d (ADG2), after starting ractopamine administration, HCW, LM area (LMA), back fat thickness (BF), marbling score (MARB), KPH and Yield Grade (YG), IGF-I and estradiol-17β (E2) concentrations. Treatments included: 1) control (C), 2) ractopamine (R), 3) Synovex-S implant (I) and 4) ractopamine and implant (RI). Weights were collected monthly, while blood samples were drawn on 0, 7, 35, 79 and 105 d. No interactions were found for any trait analyzed. ADG1 were 1.42, 1.55, 1.70 and 1.72 kg/d while ADG2 were 1.43, 1.73, 1.67 and 1.81 kg/d for C, R, I and RI respectively. Synovex-S affected ADG1 (P=0.02) but did not affect ADG2 (P=0.17). Ractopamine tended to increase ADG2 (P=0.06). No significant differences were found for HCW, LMA, BF, MARB, KPH or YG. Average carcass traits were HCW=357.8kg, LMA=83.1cm2, BF=1.12cm, MARB=415 (SM15), KPH=1.93% and YG=2.87. Synovex-S increased mean serum concentrations of E2 by 44% at 7 d (P=0.0003), by 42% at 35 d (P=0.0001), by 46% at 79 d (P=0.0001) and 13% at 105 d (P=0.012). Synovex-S increased mean serum concentrations of IGF-I by 43% at 7 d (P=0.036), by 51% at 5 d (P=0.007), by 60% at 79 d (P=0.011) and 25% at 105 d (P=0.063). Ractopamine did not alter serum concentration of E2 or IGF-I. Results indicate an effect of Synovex-S on IGF-I concentrations as well as on ADG1. Reduced increase on E2 and IGF-I might explain the lack of significance on ADG2 from the implant. Gene expression analysis using microarray will be performed on mRNA extracted from muscle biopsies (79 d) to identify changes in response to ractopamine and Synovex-S. [ABSTRACT FROM AUTHOR]