Effect of timing of post-partum introduction to pasture and supplementation with Saccharomyces cerevisiae on milk production, metabolic status, energy balance and some reproductive parameters in early lactation dairy cows.

Dietary change, an inconsistent nutrient intake and high levels of milk production make the early post-partum period (PP) a challenging time for the lactating dairy cow. This experiment investigates the effects of two early PP nutritional management strategies (NM): abrupt introduction to pasture (AP) or a total mixed ration (TMR) for 21 days followed by a gradual introduction to pasture over 7 days (GP), with (Y) or without (C) live yeast (YS) on milk production, energy balance (EB) and selected metabolic and reproductive variables. Forty multiparous dairy cows were assigned to one of four dietary treatments in a two (AP vs. GP) by two (Y vs. C) factorial, randomized block design. The experiment was conducted from days 1 to 70 PP. Blood samples were taken on day 1, day 5 and every 10 days until day 45 to determine metabolites, whilst intake (DMI), and EB were determined during week 6 PP. Milk was sampled weekly for fat, protein and lactose. Trans-rectal scanning for reproductive variables commenced on day 10 PP. Animals in the GP group had a higher DMI (p = 0.04), higher fat yield (p = 0.08) and fewer days to first ovulation (p = 0.09) vs. those in the AP group. EB (-3.5 ± 0.67 units of energy for milk production) and body condition score loss (0.70 ± 0.09) were not affected by NM. However, non-esterified fatty acids (NEFA) (p < 0.01) were higher, and glucose (p = 0.02) was lower in the AP vs. the GP group. Supplementary YS tended to improve EB (p = 0.09) and reduced NEFA (p < 0.01) vs. non-supplemented animals. These data suggest that offering animals a nutritionally balanced TMR during the first 3 weeks PP followed by a gradual introduction to pasture can improve DMI vs. pasture-based diets. Additionally, the blood metabolic profile suggests a more favourable energy status in the GP group or where YS was supplemented during the early PP period.

Eosinophil-nerve interactions and neuronal plasticity in rat gut associated lymphoid tissue (GALT) in response to enteric parasitism.

Intestinal lymphoid tissues and Peyer's patches (PP) are innervated sites of immune surveillance in the gastrointestinal tract. Following infection with F. hepatica, neuronal hyperplasia and significantly increased eosinophil and mast cell trafficking to colonic PP sites were evident in rat tissues. Nerve-eosinophil associations were significantly elevated in infected colon and colonic PP, as were colonic tissue levels of the circulatory recruitment factors IL-5 and eotaxin. Increased immunoreactivity for neuronal plasticity markers GAP-43 and neural cell adhesion molecule (NCAM) was also found in infected tissues. Such neuronal alterations in the PP during enteric parasitism may have functional consequences on particular or pathogen uptake.

Effect of mast cell degranulation on chicken ileal ion transport in vitro.

Histamine is a primary mediator of the inflammatory response in mammals. Degranulation of intestinal mast cells results in the release of mast cell mediators such as histamine. Histamine stimulates epithelial ion transport in a range of mammalian tissues via specific histamine receptors. The aim of this study was to assess a potential role of tissue mast cells and of exogenous histamine in the regulation of ion transport in avian mucosa. Broiler chicken ileal histamine release and secretory responses to mast cell degranulation were determined in vitro with the use of ELISA and Ussing chamber techniques. Pharmacological degranulation of mucosal mast cells using compound 48/80 (15 microg/mL) resulted in histamine release and an immediate-onset transient increase in transmural short-circuit current. The response to compound 48/80 was subject to tachyphylaxis and was significantly reduced in the presence of the histamine H(1) antagonist mepyramine, but was unaffected by the cyclooxygenase inhibitor piroxicam. Prior incubation with the mast cell stabilizer ketotifen prevented compound 48/80-induced increase in transmural short-circuit current. In conclusion, degranulation of avian intestinal mast cells would appear to result in histamine release that stimulates epithelial ion transport via histamine H(1) receptor activation. Although prostaglandin E(2) is a potent secretagogue in the avian small intestine epithelium, prostanoid production appears to have little role to play in mast cell-mediated epithelial ion transport.

The effects of intracoeliac injections of alpha-adrenergic agonists and veratridine on reticuloruminal motility and the evocation of rumination in sheep.

The ability of alpha-2 adrenoreceptor agonists and veratridine to evoke rumination and to modify reticular motility in adult Suffolk-cross sheep when injected by close-arterial injection into the forestomach was investigated. The specific alpha-2 adrenoreceptor agonists, xylazine and medetomidine, evoked rumination and increased reticular motility. The Na+ channel activator veratridine also evoked rumination and dramatically increased reticular motility. In contrast, injection of the alpha-1 adrenoreceptor agonist, phenylephrine, was ineffectual in evoking rumination and resulted in reduced reticular motility. It is concluded that the evocation of rumination by alpha-2 adrenergic agonists and veratridine is probably due to the activation of sensory nervous receptors (epithelial receptors) located in the reticulorumen.

An investigation into the mechanism of action of almitrine on isolated rat diaphragm muscle fatigue.

BACKGROUND: Previous studies have shown that almitrine bismesylate, a respiratory stimulant which acts on the mitochondrial electron transport chain, enhances recovery of rat diaphragm muscle from fatigue. OBJECTIVES: Our aim is to investigate if the enhanced recovery is due to an anti-oxidant property of almitrine, since the electron transport chain is a major site of intracellular free radical production. METHODS: A low-frequency fatigue protocol was used (30 Hz; 250 ms; delivered once every 2 s for 5 min), and the effects of almitrine before and after fatigue onset were compared to those of the anti-oxidant compound N-acetylcysteine (NAC). RESULTS: Almitrine (6 and 10 microg/ml) given before fatigue gave better recovery rates than postfatigue application. In contrast, NAC (100 microM) application before fatigue onset was not as effective as NAC given immediately after the cessation of the fatigue protocol. However, almitrine (6 microg/ml) completely reversed the reduction in baseline twitch tension brought about by a free-radical-producing mixture of FeCl(3) + ADP (1 mM + 2.5 mM, respectively). CONCLUSION: The results of this study confirm that almitrine enhances recovery from fatigue and, in contrast to NAC prefatigue application, is more effective. Also, almitrine was shown to have an anti-oxidant effect, but it does not act like a typical anti-oxidant.