Caprylic acid reduces Salmonella Enteritidis populations in various segments of digestive tract and internal organs of 3- and 6-week-old broiler chickens, therapeutically.

We investigated the efficacy of feed supplemented with caprylic acid (CA), a natural, 8-carbon fatty acid for reducing Salmonella enterica serovar Enteritidis colonization in commercial broiler chickens. In separate 3- and 6-wk trials, 1-d-old straight-run broiler chicks (n = 70 birds/trial) were assigned to a control group (challenged with Salmonella Enteritidis, no CA) and 2 replicates of 0.7 and 1% CA (n = 14 birds/group). Water and feed were provided ad libitum. On d 1, birds were tested for any inherent Salmonella (n = 2 birds/group). For the 3-wk trial, on d 5, birds were challenged with 8 log(10) cfu of Salmonella Enteritidis of a 4-strain mixture by crop gavage, and after 5 d postchallenge, birds (n = 2 birds/group) were euthanized to ensure Salmonella Enteritidis colonization. Caprylic acid was supplemented the last 5 d before tissue collection (n = 10 birds/group). For the 6-wk trial, on d 25, birds were challenged and confirmed for Salmonella Enteritidis colonization. The birds (n = 10 birds/group) were euthanized for tissue samples after CA supplementation for the last 5 d. Caprylic acid at 0.7 or 1% decreased Salmonella Enteritidis populations in cecum, small intestine, cloaca, liver, and spleen in both 3- and 6-wk trials. Body weight of birds did not differ between the groups (P ≥ 0.05). Further, to elucidate a potential antibacterial mechanism of action of CA, we investigated if CA could reduce Salmonella Enteritidis invasion of an avian epithelial cell line and expression of invasion genes hilA and hilD. The cell invasion study revealed that CA reduced invasive abilities of all Salmonella Enteritidis strains by ~80% (P < 0.05). Gene expression studies indicated that CA downregulated (P < 0.001) Salmonella invasion genes hilA and hilD. These results suggest that supplementation of CA through feed could reduce Salmonella Enteritidis colonization in broiler chicken and potentially reduces the pathogen's ability to invade intestinal epithelial cells by downregulating key invasion genes, hilA and hilD.

A new in vivo model for luteolysis using systemic pulsatile infusions of PGF(2α).

A new in vivo model for studying luteolysis was developed in sheep to provide a convenient method for collecting corpora lutea for molecular, biochemical, and histological analysis during a procedure that mimics natural luteolysis. It was found that the infusion of prostaglandin F(2α) (PGF(2α)) at 20 µg/min/h into the systemic circulation during the mid luteal phase of the cycle allowed sufficient PGF(2α) to escape across the lungs and thus mimic the transient 40% decline in the concentration of progesterone in peripheral plasma seen at the onset of natural luteolysis in sheep. Additional 1h-long systemic infusions of PGF(2α), given at physiological intervals, indicated that two infusions were not sufficient to induce luteolysis. However, an early onset of luteolysis and estrus was induced in one out of three sheep with three infusions, two out of three sheep with four infusions, and three out of three sheep with five infusions. Reducing the duration of each systemic infusion of PGF(2α) from 1h to 30 min failed to induce luteolysis and estrus even after six systemic infusions indicating that, not only are the amplitude and frequency of PGF(2α) pulses essential for luteolysis, but the actual duration of each pulse is also critical. We conclude that a minimum of five systemic pulses of PGF(2α), given in an appropriate amount and at a physiological frequency and duration, are required to mimic luteolysis consistently in all sheep. The five pulse regimen thus provides a new accurate in vivo model for studying molecular mechanisms of luteolysis.

Evidence for a potential role of neuropeptide Y in ovine corpus luteum function.

Neuropeptide Y (NPY) is a neurohormone that is typically associated with food intake, but it has also been reported to affect the production of progesterone from luteal tissue in vitro. However, NPY has not been previously immunolocalized in the ovine ovary or in the corpus luteum (CL) of any species, and the effects of this neurohormone on luteal function in vivo are not known. Thus, we performed fluorescent immunohistochemistry (IHC) to localize NPY in the ovine ovary and used avidin-biotin immunocytochemistry (ICC) to further define the intracellular localization within follicles and the CL. We then infused NPY directly into the arterial supply of the autotransplanted ovaries of sheep to determine the in vivo effect of exogenous NPY on ovarian blood flow and on the luteal secretion rate of progesterone and oxytocin. Immunohistochemistry revealed that the NPY antigen was localized to cells within the follicles and CL, in the nerve fibers of the ovarian stroma, and in the vessels of the ovarian hilus. In the follicle, the NPY antigen was localized to nerves and vessels within the theca interna layer, and strong staining was observed in the granulosal cells of antral follicles. In the CL, NPY was localized in large luteal cells and in the vascular pericytes and/or endothelial cells of blood vessels, found dispersed throughout the gland and within the luteal capsule. In vivo incremental infusions of NPY at 1, 10, 100, and 1,000 ng/min, each for a 30-min period, into the arterial supply of the transplanted ovary of sheep bearing a CL 11 d of age increased (P< or =0.05) ovarian blood flow. The intra-arterial infusions of NPY also increased (P< or =0.05) in a dose-dependent manner the secretion rate of oxytocin, which was positively correlated (P< or =0.05) with the observed increase in ovarian blood flow. The infusions of NPY had a minimal effect on the secretion rate of progesterone, and similar intra-arterial infusions of NPY into sheep with ovarian transplants bearing a CL over 30 d of age had no significant effect on ovarian blood flow or on the secretion rate of progesterone. These results suggest that NPY acts on the luteal vascular system and the large luteal cells to rapidly stimulate blood flow and the secretion of oxytocin, respectively, which collectively implies a putative role for NPY during the process of luteolysis when increasing amounts of oxytocin are secreted from the ovine CL in response to uterine pulses of prostaglandin F2alpha.

Function and lifespan of corpora lutea in ewes treated with exogenous oxytocin.

Oxytocin was administered to Dorset and Shropshire ewes in one experiment and to Dorset ewes in a further 4 experiments. In Exp. 1, concentrations of plasma progesterone and lengths of the oestrous cycle in ewes given oxytocin subcutaneously twice a day on Days 0-3, 2-5, 4-7, 6-9, 8-11, 10-13, 12-15 or 14-17 were similar to those of control ewes. In Exp. 2, intraluteal infusions of oxytocin from Day 2 to Day 9 after oestrus had no effect on concentration of progesterone, weight of CL collected on Day 9 or length of the oestrous cycle. In Exp. 3, intraluteal infusions of oxytocin on Days 10-15 after oestrus had no effect on weight of CL collected on Day 15. In Exp. 4, s.c. injections of oxytocin on Days 3-6 after oestrus had no effect on weight of CL collected on Day 9, concentrations of progesterone or length of the oestrous cycle. In Exp. 5, s.c. injections of oxytocin twice a day did not affect the maintenance and outcome of pregnancy in lactating and nonlactating ewes. Exogenous oxytocin, therefore, does not appear to affect luteal function at any stage of the ovine oestrous cycle although oxytocin has been reported by others to alter ovine CL function.