High dietary Ca and microbial phytase reduce expression of Ca transporters while enhancing claudins involved in paracellular Ca absorption in the porcine jejunum and colon.

Expression levels of genes (RT-qPCR) related to Ca and P homeostasis (transporters and claudins (CLDN)) were determined in porcine jejunal and colonic mucosa. Forty growing pigs (BW 30.4±1.3 kg) received a low and high Ca content (2.0 and 9.6 g/kg, respectively) diet with or without microbial phytase (500 FTU/kg) for 21 days. Dietary Ca intake enhanced serum Ca and alkaline phosphatase concentration and reduced P, 1,25(OH)2D3, and parathyroid hormone concentration. Jejunal TRPV5 mRNA expression was decreased (32%) with phytase inclusion only, while colonic transient receptor potential vanilloid 5 (TRPV5) mRNA was reduced by dietary Ca (34%) and phytase (44%). Both jejunal and colonic TRPV6 mRNA expression was reduced (30%) with microbial phytase. Calbindin-D9k mRNA expression was lower in colonic but not jejunal mucosa with high dietary Ca (59%) and microbial phytase (37%). None of the mRNAs encoding the Na-P cotransporters (NaPi-IIc, PiT-1, PiT-2) were affected. Jejunal, but not colonic expression of the phosphate transporter XPR1, was slightly downregulated with dietary Ca. Dietary Ca downregulated colonic CLDN-4 (20%) and -10 (40%) expression while CLDN-7 was reduced by phytase inclusion in pigs fed low dietary Ca. Expression of colonic CLDN-12 tended to be increased by phytase. In jejunal mucosa, dietary Ca increased CLDN-2 expression (48%) and decreased CLDN-10 (49%) expression, while phytase slightly upregulated CLDN-12 expression. In conclusion, compared to a Ca deficient phytase-free diet, high dietary Ca and phytase intake in pigs downregulate jejunal and colonic genes related to transcellular Ca absorption and upregulate Ca pore-forming claudins.

Supplementation of piglets with nutrient-dense complex milk replacer improves intestinal development and microbial fermentation.

Weaning of piglets causes stress due to environmental, behavioral, and nutritional stressors and can lead to postweaning diarrhea and impaired gut development. The diet changes experienced during weaning require extensive adaptation of the digestive system. A well-developed piglet that had creep-feed experience before weaning performs better after weaning. In the current study, the effect of providing sow-fed piglets with a supplemental nutrient-dense complex milk replacer (NDM) on gut development and growth performance was studied. Litters of sows with similar parities (3.6 ± 0.8) and similar numbers of live born piglets (13.5 ± 0.3) were assigned to 1 of 2 groups: 1 group of piglets had ad libitum access to NDM from Day 2 through 21 after birth, whereas the other group was used as controls. Nutrient-dense complex milk replacer-fed piglets were shown to be significantly heavier after 21 d of supplementation compared with the control piglets. At Day 21, 3 piglets from each litter were euthanized for morphological and functional analyses of the intestinal tract. The small intestines of NDM-fed piglets had significantly higher weights (g) as well as significantly higher relative weight:length ratios (g//cm) compared with the small intestines of control piglets ( < 0.05). Morphometric analysis demonstrated that villi length and numbers of goblet cells did not differ between groups. However, NDM-fed piglets had deeper crypts ( < 0.001) and an increased expression of the cell-proliferation marker proliferating cell nuclear antigen in crypts ( < 0.05), suggesting higher cell-proliferation rates. The gene encoding IGF-1 showed a tendency to higher gene expression in the jejunum from NDM-fed piglets ( = 0.07) compared with the jejunum from control piglets, suggesting that IGF-1 might be involved in the regulation of cell proliferation and intestinal growth. Finally, as a result of dietary fiber in NDM, piglets showed significantly increased concentrations of metabolic fermentation products. This suggests differences in metabolic activity in the colon between treatment groups. In conclusion, providing sow-fed piglets with NDM before weaning stimulates intestinal proliferation, leading to increased circular growth. Nutrient-dense complex milk replacer supplementation might, therefore, help piglets through the transition period at weaning by increased BW and increased capacity for uptake of nutrients.

An increased ratio of dietary tryptophan to lysine improves feed efficiency and elevates plasma tryptophan and kynurenine in the absence of antimicrobials and regardless of infection with enterotoxigenic Escherichia coli in weaned pigs.

This experiment examined if a higher ratio of dietary Trp:Lys in the absence of antimicrobials improves production indices and modulates diarrhea in weaned pigs infected with enterotoxigenic Escherichia coli (ETEC). Effects of the Trp:Lys ratio on plasma levels of Trp and its metabolite kynurenine (Kyn) were also examined. Individually housed mixed-sex pigs (n = 72) weaned at 21 d of age (Landrace × Large White; initial BW of 6.3 ± 0.32 kg) were stratified into 1 of 6 treatments (n = 12) according to a 2 × 3 factorial arrangement of (i) infection or without infection with ETEC and (ii) 3 dietary standardized ileal digestible (SID) Trp:Lys ratios of 0.17, 0.21, or 0.26 in a randomized complete block design. Pigs were fed diets (10.4 MJ NE; 1.24% SID Lys; 19.5% CP) ad libitum for 3 wk after weaning. Pigs were infected with ETEC (O149:K98:K88) at 72, 96, and 120 h after weaning and then bled on day 11. A Trp:Lys ratio of 0.26 improved (P = 0.021) G:F over the study period compared to other ratios, without an infection effect (P > 0.05). Treatments did not affect ADG or ADFI (P > 0.05). Infection increased (P = 0.039) the diarrhea index and increased fecal consistency scores (P = 0.010). Plasma Trp and Kyn were lower (P < 0.001) in pigs fed 0.17 Trp:Lys than those fed ratios of 0.21 and 0.26 and were not affected (P > 0.05) by infection. In conclusion, in the absence of antimicrobials, increasing the dietary Trp:Lys ratio to 0.26 improved G:F after weaning and increased plasma levels of Trp and Kyn.

Steroid glucuronides as male pheromones in the reproduction of the African catfish Clarias gariepinus--a brief review.

After ovulation, female African catfish are strongly attracted by the odor of male conspecifics. This attraction depends on the presence of the seminal vesicle, a part of the male reproductive organs. Removal of the seminal vesicle illustrates this fact. A low dose of seminal vesicle fluid, added to the water, appears to be highly attractive for catfish which have ovulated. Fractionation of the fluid and testing of the different fractions shows that steroid glucuronides could be responsible for the attraction. These steroid glucuronides can be identified with gas chromatographic-mass spectrometric analysis. A mixture of glucuronides, prepared to resemble the composition of the seminal vesicle fluid, evokes a dose-dependent attraction. The most potent odorant, observed by measuring electrical responses from the olfactory epithelium and from the olfactory tract appears to be 3 alpha,17 alpha-dihydroxy-5 beta-pregnan-20-one-3 alpha-glucuronide.

The seminal vesicle of the African catfish, Clarias gariepinus. A histological, histochemical, enzyme-histochemical, ultrastructural and physiological study.

The seminal vesicle of the African catfish, Clarias gariepinus, consists of 36-44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. In this fluid sperm cells are stored. The seminal vesicle fluid immobilizes the sperm cells. After ejaculation, it prolongs the period of sperm activity. The seminal vesicle fluid is secreted by the epithelium lining the tubules. The tubules in the proximal part of the lobes are predominantly lined by a simple cylindrical and those of the distal part by a simple squamous epithelium. These epithelial cells contain enzymes involved in energy-liberating processes, the enzyme activities being proportional to the height of the cells. Interstitial cells between the tubules have enzyme-histochemical and ultrastructural features indicative of steroid biosynthesis. Similar characteristics are found in testicular interstitial cells. The most rostral seminal vesicle lobes and the most caudal testicular efferent tubules form a network of tubules that opens at the point where the paired parts of the sperm ducts fuse with each other. The tubules of most seminal vesicle lobes, however, form a complex system that fuses with the unpaired part of the sperm duct.

A quantitative study of steroid bioconversions in the testis of the African catfish, Clarias gariepinus (Burchell), under natural spawning and natural and cultivated non-spawning conditions.

Quantitative aspects of bioconversions in the testes of the African catfish (Clarias gariepinus) were studied in vitro by incubation of tissue with [3H]pregnenolone or [3H]androstenedione. During the breeding period, spawning and non-spawning animals were collected from their natural habitat, the Hula nature reserve, in northern Israel. In the same period, non-spawning animals were collected from a fish pond in the same region. It was shown that spawning was accompanied by significant changes in steroid bioconversions, i.e. a reduction in androgen synthesis, especially of 11 beta-hydroxyandrostenedione and 11 beta-hydroxytestosterone and an increase in the production of C21-steroids, especially progesterone, 17 alpha-hydroxyprogesterone and a pregnenolone ester. These changes resulted from a decreased contribution of the cytochrome P-450 enzymes 17 alpha-hydroxylase, C17-20-lyase and 11 beta-hydroxylase. A rise in plasma gonadotrophin concentration was observed only in spawning catfish. In the absence of such an increase in plasma gonadotrophin, steroid synthesis in the testes of non-spawning feral and pond catfish was primarily directed towards the production of 11-oxygenated androgens and 5 beta-pregnane-3 alpha,17 alpha,20 alpha-triol. It is suggested that spawning is induced by gonadotrophin and the ensuing change in steroidogenesis. It is possible that husbandry conditions inhibit the necessary increase in gonadotrophin release.

Gonadal steroidogenesis and the possible role of steroid glucuronides as sex pheromones in two species of teleosts.

In general, female zebrafish,Brachydanio rerio, ovulate only in the presence of males. The stimulant must be pheromonal as even male holding water is capable of inducing ovulation. After ovulation the mating phase begins. During this phase the male follows the female and oviposition as well as fertilization takes place. Both the ovulation and the mating are controlled by pheromones synthesized by the gonads. Ovulation can be induced by testicular homogenates. After the lipid material has been extracted from the testicular homogenates, the remaining aqueous phase can still induce ovulation. However, when the aqueous phase is treated with the enzymeß-glucuronidase, it loses the ability to induce ovulation. This is an indication that glucuronides, probably steroid glucuronides, are the compounds responsible.During the mating phase, ovulated female zebrafish become attractive to males. It was found that, after ovulation, ovarian extracts contain the compounds responsible for attracting males. The attractant consists of a mixture of steroid glucuronides.After incubation of the gonads with(3)H-precursors seven steroid glucuronides have been identified in the testis and five in the ovary.Under fish culture conditions the African catfish,Clarias gariepinus, can produce postivitellogenic oocytes throughout the year. However, in capitivity neither males nor females spawn. In female catfish maturation and ovulation can be induced by treatment with gonadotropins. It might be possible that, analogous to the zebrafish, some reproductive processes in the catfish have to be induced by pheromones. It has been demonstrated that pheromonal compounds released by the seminal vesicles are involved in the attraction of female conspecifics. The steroid glucuronide synthesizing capability of the testes and the seminal vesicles of the male catfish are examined, as well as that of the ovary before and after ovulation of the female catfish. Both testes and seminal vesicles appear to be capable of steroid biosynthesis but only the latter synthesizes steroid glucuronides. Six of these conjugates have been isolated and identified. In the female catfish the ovaries are capable of synthesizing seven steroid glucuronides, but only after ovulation.

Pimozide modulates the luteinizing hormone-releasing hormone effect on gonadotrophin release in the African catfish, Clarias lazera.

In the African catfish the effect of (i) the dopamine antagonist pimozide (PIM), (ii) a luteinizing hormone-releasing hormone analog (LH-RHa), and (iii) a combination of these substances on gonadotrophin (GTH) release and on ovulation was investigated. PIM alone increased plasma GTH levels in juvenile catfish but was ineffective in mature animals. LH-RHa increased plasma GTH levels in both juvenile and mature catfish and within 12 hr after the injection a high rate of ovulation (80%) was observed. PIM potentiated the LH-RHa effect on GTH release and ovulation. It was concluded that dopamine does not effect the GTH release directly, but modulates the effect of endogenous and exogenous gonadotrophin-releasing hormone.