Aerobic heterotrophic bacteria associated with oyster larvae feed algae Isochrysis galbana, Monochrysis lutheri and Pseudoisochrysis paradoxa were isolated and enumerated. The bacterial numbers ranged from 7.8x10³ to 3.9x10⁶ CFU per ml. The bacteria associated with Pseudoisochrysis sp. were identified and the majority of isolates belonged to genera Leucothrix (51%). Also present were members of Pseudomonas III sp. (19.1%), atypical Moraxella sp. (16.8%), Moraxella sp. (7.2%) and Flavobacterium sp. (5.9%). The growth of bacteria on marine agar was fastidious and took four days to form visible colonies. None of the bacterial isolates grew in buffered salt broth in which the algae had been grown. Marine broth supplemented with 0.1% beef extract best supported the growth of the isolates, while ferric citrate (3x10⁻⁴ M) supported their growth in buffered salt broth. The role of algae as a solid support for bacteria was investigated by studying the attachment of bacteria on glass slides suspended in the growth medium. The percent of Leucothrix sp. attached to the slide was 2.1-3.0%. This was four to six times greater than that of Staphylococcus (0.5%), an organism well known for its commensal growth on skin and mucus membranes of man and animal. Hydrophobic attraction, which is thought to play an important role in the orientation of bacteria to solid surfaces, was studied by measuring the adsorption of bacteria on hydrocarbons introduced to a bacterial suspension. Leucothrix sp. exhibited the strongest affinity, whereas Flavobacterium sp. and Pseudomonas sp. adsorbed the least. An attempt to obtain an axenic culture of algae by antibiotic treatment was unsuccessful due to the detrimental effect of antibiotics to both algae and bacteria. / Graduation date: 1982

Residual feed intake (RFI) is one method to identify feed efficient animals; however, this method is costly and time consuming therefore, identifying an indirect measure of RFI is important. Evaluating the glucoregulatory mechanisms in cattle selected for divergent RFI may provide insight into metabolic processes involved in feed efficiency. This study evaluated the effect of a glucose (GLUC) challenge on efficient (LRFI) and inefficient (HRFI) tropically adapted bulls and heifers. Insulin (INS) secretion was determined by radioimmunoassay (RIA) and GLUC was determined by colorimetry. Insulinogenic index (IIND) was calculated as the ratio of INS to GLUC (I/G). Bonsmara heifers were evaluated in two experiments. Similar results were observed in both experiments. RFI affected (P < 0.05) INS response; with LRFI heifers having a greater INS response than HRFI heifers. Similarly, RFI affected (P < 0.05) IIND; with LRFI heifers having a greater IIND than HRFI heifers. In Santa Gertrudis bulls, RFI did not affect (P > 0.05) GLUC conc. or Ins. response; however, numerically HRFI bulls had a greater INS response than LRFI bulls. RFI affected (P < 0.05) IIND; with LRFI bulls having a lower IIND than HRFI bulls. In Brahman heifers (Exp 1), RFI did not affect (P > 0.05) GLUC concentration or INS. response; however, numerically HRFI heifers had a greater INS response than LRFI heifers. RFI affected (P < 0.05) IIND; with LRFI heifers having a lower IIND than HRFI heifers. In Brahman bulls (Exp 2), RFI affected (P > 0.05) INS response; with HRFI bulls having a greater INS response than LRFI bulls. RFI affected (P < 0.05) IIND; with LRFI bulls having a lower IIND than HRFI bulls. Bonsmara cattle evaluated for RFI had a response to an influx of exongenous glucose that was opposite to that observed in the Brahman and Santa Gertrudis cattle evaluated for RFI. Insulinogenic index was significantly different between RFI groups in each experiment. The lower amount of INS required for clearance of the GLUC from the circulation of the Brahman and Santa Gertrudis cattle fits with our hypothesis that more efficient cattle would require less INS than the less efficient cattle. Further research and studies need to establish glucoregulatory differences between breeds and sexes of cattle evaluated for RFI.

Objectives of this study were to characterize residual feed intake (RFI) in growing calves and to examine relationships with growth, carcass composition, physiological indicators, energy metabolism and reproduction. To accomplish these objectives, multiple experiments were conducted. In all experiments, RFI was calculated as the difference between actual DMI and expected DMI from linear regression of DMI on mid-test metabolic BW and ADG. To examine the relationships between RFI and rate and composition of growth, and reproduction an experiment was conducted with postweaning Brangus heifers (N = 348). Measures of carcass composition (longissimus muscle area, LMA; and 12th rib fat thickness, BF) were obtained by ultrasound at the start and end of each experiment. To determine if serum IGF-I concentration is associated with RFI, two experiments were conducted with Angus bulls and heifers (N = 95) divergently selected for serum IGF-I concentration. To evaluate relationships with energy metabolism, calves with low and high RFI were selected for determination of heart rate as an indicator trait for energy expenditure (4 experiments) and liver mitochondrial function (3 experiments). Residual feed intake was not correlated with ADG, but was positively correlated with gain in BF such that the more efficient calves were leaner. Calves from the low IGF-I selection line had lower RFI suggesting that RFI and IGF-I are related and that IGF-I could be used as an indicator trait to aid in selection for improved RFI in Angus cattle. Calves with low RFI had lower energy expenditure and greater mitochondrial acceptor control ratios than calves with high RFI suggesting improved regulation of energy metabolism. A similar percentage of heifers with low RFI attained puberty as those with high RFI by the end of the experiment. Results from this study indicate that producers can utilize RFI to select for improved feed efficiency with minimal impact on growth, carcass composition and reproduction.

Objectives of this research were to characterize residual feed intake (RFI) in growing and finishing steers and examine phenotypic correlations between performance, feed efficiency, carcass, digestib ility, and physiological indicator traits. The research included two growing studies and one finishing study. Braunvieh-sired crossbred steers (n = 169) and Santa Gertrudis steers (n = 120) were individually fed a roughage-based diet for 77 d during the growing phase. Santa Gertrudis steers (n = 120) were individually fed a grain-based diet for 80 d during the finishing phase. Individual body weight (BW) and feed intake data were recorded. Residual feed intake was calculated as the difference between actual dry matter intake (DMI) and DMI predicted from linear regression of DMI on mid-test metabolic BW. During the growing phase, initial ultrasound measures of 12th rib fat thickness (FT) and final ultrasound measures of Longissimus muscle area (LMA), FT, and intramuscular fat (IMF) were obtained. During the finishing phase, initial and final LMA, FT, and IMF ultrasound measurements were obtained. Finishing steers were slaughtered at 1.0 cm of FT and carcass cooler traits measured. Blood samples were collected at the start and end of each feeding period and analyzed for physiological indicators. Temperament traits were also measured at the start and end of each feeding period. Growing and finishing steers with low RFI consumed 19-22% less feed than growing and finishing steers with high RFI, but did not differ in average daily gain (ADG). Consequently, steers with low RFI were also more efficient as measured by feed conversion ratio and partial efficiency of growth. Steers with low RFI had less FT compared to steers with high RFI. Initial serum IGF-I was correlated with RFI in growing steers indicating that IGF-I could be a potential indicator trait for RFI in growing cattle. Additionally, RFI was correlated with digestibility to indicate more efficient cattle had higher dry matter digestibility. Results indicate that RFI has potential to allow producers to select more efficient animals without increasing growth rate. Moreover, serum IGF-I may facilitate early detection and more accurate selection of animals that are superior for growing RFI.

The US hybrid striped bass (Morone chrysops x M. saxatilis) industry has been negatively impacted by infectious diseases because there are very few approved drugs and vaccines. Therefore, a series of experiments was conducted to explore the potential use of various dietary supplements including autolyzed brewers yeast, the commercial prebiotic GroBiotic®, oligonucleotides and levamisole for improvement of hybrid striped bass growth, immunity and resistance to disease caused by various pathogenic bacteria. In two trials with brewers yeast, fish fed diets supplemented with yeast at 2% generally showed enhanced weight gain and feed efficiency compared with those fed a basal diet. Brewers yeast also positively influenced resistance to S. iniae infection. In addition, results of immune response assays demonstrated that brewers yeast can be administered for relatively long periods without causing immunosuppression. GroBiotic® (Grobiotic) also resulted in significantly enhanced weight gain, innate immune responses and resistance of juvenile hybrid striped bass to S. iniae infection. An additional experiment with sub-adult fish showed significantly reduced mortality of fish fed a diet supplemented with GroBiotic® at 2% when subjected to an in-situ Mycobacterium marinum challenge. This is the first report of positive effects from dietary prebiotics for fish health management, although many fundamental questions should be pursued further. Dietary supplementation of a commercial oligonucleotide product (Ascogen P®) at 0.5% of the diet was shown to enhance resistance of hybrid striped bass against S. iniae infection and increased their neutrophil oxidative radical production. However, the effect on growth was marginal. Dietary levamisole supplementation at a low level (100 mg/kg) enhanced the growth and feed efficiency of juvenile hybrid striped bass. However, an elevated dosage (1000 mg/kg diet) strongly suppressed growth, feed intake and feed efficiency. Hypothesized beneficial influences, including antibody production and resistance to S. iniae and A. hydrophila were not substantiated. Although dietary levamisole increased fish macrophage respiratory burst, an in vitro study failed to show a direct effect on cultured macrophages. This suite of studies demonstrated the potential use of some dietary supplements to enhance hybrid striped bass production. Thus, immunonutrition represents a valuable strategy to apply in aquaculture.

Thesis--PlanA (M.S.)--University of Wisconsin--Stout, 2003. / Includes bibliographical references.

Thesis (Ph. D. (Plant Production))--University of Pretoria, 2001. / Adobe Acrobat Reader needed to open files.

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In Venezuela, four sheep fitted with rumen cannulas were fed the toxin-containing legumes <i>Leucaena leucocephala</i> (sun dried leaves and stems) and <i>Canavalia ensiformis</i> (grains). <i>L. leucocephala</i> did not have any apparent toxic effects on the animals, in spite of the presence of the toxic compounds 3,4 DHP and 2,3 DHP in the rumen. There were no significant effects on the rumen pH, concentrations of VFAs, microbial counts, rate of rice straw degradation or in the rumen outflow of liquids and solids. However, there was an increase in the concentration of ammonia in the rumen, and in the number of Gram negative rods isolated from the rumen of sheep when <i>L. leucocephala</i> was added to the diet. When <i>C. ensiformis</i> was supplemented the presence of canavanine in the rumen was confirmed. Sheep did not show signs of toxicity. There was no effect on rumen pH, microbial counts, degradation of rice straw or rates of outflow of liquids and solids from the rumen. There was a decrease in the rumen concentrations of valerate and ammonia and an increase in the numbers of Gram negative bacteria isolated from the rumen of sheep as the dietary inclusion of <i>Canavalia</i> increased. Several pure cultures capable of mimosine, 2,4 DHP and (in fewer cases) 3,4 DHP wre isolated. One of them, a Gram variable spore-forming rod, presumably a new species of <i>Clostridium</i>, was characterised. The presence of degraders of mimosine and DHP in the rumen presumably accounted for the lack of toxicity of <i>L. leucocephala</i> in Venezuela. The effect of canavanine on the growth and products of fermentation of pure cultures was independent of the Gram staining reaction and the results of experiments using media containing either peptides and amino acids or free amino acids alone suggest that canavanine may have an effect on peptide hydrolysis.