Dietary non-phytate phosphorus requirements for optimal productive and reproductive performance, and egg and tibial quality in egg-type duck breeders.

Optimal dietary non-phytate phosphorus (NPP) is essential in poultry to maximise productive and reproductive performance, along with indices of egg and bone quality. This study aimed to establish the NPP requirements of egg-type duck breeders aged from 54 to 80 weeks on the following traits: egg production, egg incubation, egg quality, tibial characteristics, reproductive organ, plasma indices, and the expression of genes related to phosphorus absorption. Longyan duck breeders aged 54 weeks (n = 300) were randomly allotted to five treatments, each containing six replicates of 10 individually caged birds. Birds were fed corn-soybean meal-based diets containing 0.18, 0.25, 0.32, 0.38, and 0.45% NPP/kg for 27 weeks. The tested dietary NPP levels did not affect egg production or egg quality indices. The hatchling weight of ducklings increased (quadratic, P < 0.01) as dietary NPP level increased, and the highest value occurred with 0.25% NPP. The number of large yellow follicles (LYF), and the relative weights of LYF and ovary showed linear and quadratic responses to dietary NPP levels; the lowest number and relative weight of LYF occurred with 0.38% NPP, and the lowest ovarian weight was obtained with 0.25% NPP. There were no differences in tibial length, breaking strength, and mineral density in response to dietary NPP levels. In contrast, tibial content of Ca increased (linear, P < 0.01) with dietary NPP levels increasing from 0.18 to 0.45%, and the tibial content of P increased at 0.32% NPP and the higher dietary NPP levels. Plasma concentration of P showed a quadratic (P < 0.05) response to the dietary NPP levels, where the highest value was seen at 0.38% NPP. In conclusion, dietary NPP levels from 0.18 to 0.45% had no effects on egg production, and egg and tibial quality of duck breeders. The duck breeders fed a diet with 0.25% NPP showed the highest hatchling weight of their offspring, while those fed 0.38% NPP had the lowest number and relative weight of LYF. These results indicated that the diet with 0.25% NPP can be used in egg-type duck breeders to improve the hatchling weight of their offspring, without adverse effects on their productivity. The regression model indicated that the maximal hatchling weight of ducklings was obtained from duck breeders fed the diet with 0.30% NPP.

Unilateral low-frequency stimulation of central piriform cortex delays seizure development induced by amygdaloid kindling in rats.

Low-frequency stimulation of the kindling site interferes with the course of kindling epileptogenesis. The present study examined the effect of unilateral low-frequency stimulation of the central piriform cortex on seizure development induced by amygdaloid kindling in rats. The ipsilateral or contralateral central piriform cortex received low-frequency stimulation (15 min train of 0.1 ms pulses at 1 Hz and 50-150 muA) immediately after termination of once daily kindling stimulation (2 s train of 1 ms pulses at 60 Hz and 150-300 microA) in the right amygdala for 30 days. Low-frequency stimulation of either the ipsilateral or contralateral central piriform cortex significantly suppressed the progression of seizure stages and reduced afterdischarge duration throughout the course of amygdaloid kindling. The marked suppression induced by low-frequency stimulation of the central piriform cortex on either side was predominantly due to the significant retardation of progression from stage 0 to stage 1 and stage 3 to stage 4 seizures. In addition, the suppressive effect of low-frequency stimulation did not disappear when the stimulation was stopped; it could persist for at least 10 days. These findings indicate that brain areas other than the kindling focus, such as the central piriform cortex on both sides, can also be used as reasonable targets for low-frequency stimulation to retard seizure development induced by amygdaloid kindling. Secondly, like the ipsilateral central piriform cortex, the contralateral central piriform cortex may also participate in the progression and secondary generalization of focal seizures. The study suggests that unilateral low-frequency stimulation of the central piriform cortex may have a significant antiepileptogenic effect, and may be helpful for exploring effective and long-lasting therapies for human temporal lobe epilepsy.

Effects of carnosine on amygdaloid-kindled seizures in Sprague-Dawley rats.

The effects of carnosine (beta-alanyl-L-histidine) on amygdaloid-kindled seizures were investigated in rats. I.p. injection of carnosine (500, 1000, 1500 mg/kg, i.p.) significantly decreased seizure stage, afterdischarge duration and generalized seizure duration, and significantly prolonged generalized seizure latency of amygdaloid-kindled seizures, in a dose-dependent, and time-related manner. The protective effect of carnosine (1500 mg/kg) was completely antagonized by histamine H1-antagonists pyrilamine (2, 5 mg/kg, i.p.) and diphenhydramine (5, 10 mg/kg, i.p.), but not by histamine H2-antagonist zolantidine even at a high dose of 10 mg/kg. Carnosine (1500 mg/kg, i.p.) caused a significant increase of carnosine and histidine levels in the hypothalamus, thalamus, hippocampus, amygdala and cortex, as well as histamine levels in the hippocampus and amygdala. I.c.v. injection of alpha-fluoromethylhistidine (50 microg, i.c.v.), a selective and irreversible histidine decarboxylase inhibitor, only partially reversed the inhibition of amygdaloid-kindled seizures induced by carnosine. In addition, carnosine significantly decreased glutamate contents in the amygdala and hippocampus. These results indicate that carnosine could protect against amygdaloid-kindled seizures in rats, and its action may be due to the activation of histamine postsynaptic H1-receptors via two different mechanisms, one being carnosine's direct action, and the other being indirectly mediated by histaminergic pathway. The study suggests that carnosine may be an endogenous anticonvulsant factor in the brain and could be used as a new antiepileptic drug in the future.