Desempenho e rendimento de carcaça em frangos de corte de um a 46 dias alimentados com dietas contendo diferentes níveis de valina e reduzido teor proteico / Performance and carcass yield of broilers from 1 to 46 days fed diets containing different levels of valine and reduced protein content

Este estudo teve como objetivo avaliar as relações de valina:lisina digestíveis em dietas com teor reduzido de proteína bruta (PB) e os efeitos dessa redução sobre desempenho e rendimento de carcaça em frangos de corte. Foram utilizados 1200 pintos machos seguindo modelo inteiramente ao acaso, com seis tratamentos de seis repetições (exceto controle, com 10 repetições), compostos por 30 aves cada. O tratamento controle (T1) foi formulado conforme os níveis de proteína bruta e aminoácidos (AAs) recomendados por Rostagno et al . (2011), e os demais tratamentos (T2 a T6) tiveram seus níveis de PB reduzidos (4% em relação ao controle) e variaram em função da relação valina:lisina digestíveis, com cinco níveis equidistantes em intervalos de 0,07:1, variando de 0,63:1 e 0,91:1 (dietas até 21 dias) e de 0,64:1 e 0,92:1 (dietas após 21 dias). As seguintes características de desempenho foram avaliadas: ganho de peso, consumo de ração, conversão alimentar, viabilidade criatória e índice de eficiência produtiva. Aos 46 dias de idade, seis animais por repetição foram abatidos para determinação de rendimento de carcaça e de cortes comerciais. As diferentes relações valina:lisina digestíveis não influenciaram o desempenho dos animais (P>0,05) para nenhuma característica avaliada. A redução proteica piorou a conversão alimentar dos animais (P≤0,05) até os 21 dias. Os resultados sugerem que os níveis de valina utilizados não afetam o desempenho dos animais, apenas o rendimento de peito e que, portanto, a redução proteica não é recomendada durante as três primeiras semanas de criação.

This study aimed to evaluate valine:lysine ratios in diets with reduced content of crude protein and the effects of this reduction on the performance of broiler chickens. 1200 male chicks were used following a complete randomized design with six replicates of six treatments (except control, with 10 replicates), each one with 30 chicks. The control treatment (T1) was formulated following levels of crude protein (CP) and the amino acids (AAs) recommended by Rostagno et al. (2011), and the other treatments (T2 to T6) had reduced levels of CP (4 % compared to control) and varied in proportion valine:lysine, with 5 levels at equidistant intervals 0.07:1 ranging from 0.63:1 to 0.91:1 (up to 21 days) and from 0.64:1 to 0.92:1 (after 21 days). The performance characteristics measured were: weight gain, feed intake, feed conversion, viability and productive efficiency index. At 46 days six animals per replicate were slaughtered for evaluation of carcass and commercial cuts. The different valine:lysine ratios did not affect animal performance (P>0.05). Reducing protein impaired feed conversion (P≤.05) up to 21 days. The results suggest that levels of valine used did not affect the broilers' performance, however, breast meat yield and reduced protein are not recommended during the first three weeks.

Enkephalinergic involvement in substantia nigra in the modulation of hypothalamically-induced predatory attack behavior.

The present study was carried out in five cats which did not attack the rats spontaneously. Predatory attack on an anaesthetized rat was elicited by electrical stimulation of lateral hypothalamus at a mean current strength of 650 microA. The attack was accompanied by minimal affective display and culminated in neck biting. Microinfusions of DAME (delta-alanine methionine enkephaline) in 500 ng dose in substantia nigra facilitated the predatory attack and there was a significant reduction in the threshold current strength for affective display as well as somatomotor components. Microinfusions of naloxone, an opioid antagonist in 1.0 microg dose when DAME effect was at its peak reversed the facilitatory effects and the threshold returned to the control levels within 10 minutes of naloxone infusion at the same locus. Microinfusions of naloxone alone in similar dosage completely blocked the predatory attack response as indicated by an increase in the threshold current strength for somatomotor as well as affective display components. The somatomotor were completely inhibited and could not be elicited even when the current strength was increased to 1000 microA. Control injections of saline in similar volumes (0.5 microl) failed to produce any response Microinfusions of naloxone in lower dose (250 ng) failed to produce any blocking effect. These findings indicate that hypothalamically elicited predatory attack is facilitated by enkephalinergic mechanisms operating at the midbrain level.

Role of midbrain ventro-lateral tegmental area (VTA) enkephalinergic mechanisms in the facilitation of hypothalamically-induced predatory attack behaviour.

Bipolar concentric electrodes were implanted in five cats in extreme lateral regions of hypothalamus. These sites were electrically stimulated using biphasic square wave pulses at a current strength ranging from 300-800 microA to evoke predatory attack on an anaesthetized but live rat. At lower current strength (300 microA) only alertness with pupillary dilatation was produced. Gradual increase in the current strength led to the recruitment of somatic and affective components and a predatory attack was exhibited at a mean current strength of 700 microA. A scoring system allowed the construction of stimulus response curves, which remained fairly constant when repeated over a period of 3-4 weeks. Bilateral microinjections of delta-alanine methoinine enkephaline (DAME) (500 ng in 0.5 microliter saline) in ventrolateral tegmental area (VTA) elevated the mean threshold current strength for affective components while somatomotor components were totally inhibited. The blocking effect of DAME persisted for 1 hour. Microinjections of naloxone (1 microgram) in similar volumes facilitated the response as indicated by a reduction in threshold current strength for somatomotor and affective components. Microinjections of naloxone (1 microgram) in similar volumes facilitated the response as indicated by a reduction in threshold current strength for somatomotor and affective components. Microinjections of naloxone (1 microgram) also reversed the blocking effect of DAME and the thresholds returned to the control level within 10 min while microinjection of normal saline as control had no effect. The excitatory effects of naloxone and inhibitory effects of DAME were statistically significant at P < 0.01 and P < 0.05 respectively with Wilcoxon's signed rank test. The present study indicates that enkephalinergic as well as opioidergic mechanisms operating at the midbrain (VTA) level are involved in the inhibition of predatory attack as elicited from lateral hypothalamus.

Efeito inibidor do crescimento tumoral pela metionina-encefalina / Inhibitory effect of tumor growth by methionine-enkephalin

A metionina-encefalina (Met-Enk) é um pentapeptídeo opióide derivado do prónormônio proencefalina A, presente em células neuroendócrinas e hematopoéticas. Estudos experimentais evidenciam seu papel na induçäo, ativaçäo e controle de eventos imunomoduladores, inclusive com potente efeito inibidor do crescimento tumoral. O presente estudo demonstra que o efeito inibidor da Met-Enk no crescimento de um fibro-histocitoma, em camundongos BALB/cJ, é influenciado pelo protocolo utilizado, via de administraçäo e dose do pentapeptídeo opióide utilizada no tratamento. A administraçäo de Met-Enk por via intracerebral retardou de forma eficiente o processo de tumorigênese, aumentando a sobrevida dos animais e reduzindo de forma significativa a área tumoral final. Dose baixa (0,25mg/Kg) de Met-Enk administrada por via intracerebral foi ainda mais potente no controle da tumorigênese

Effects of ACTH, epinephrine and met-enkephalin on brain B-endorphin-like immunoreactivity, and of ACTH, epinephrine, met-enkephalin and naloxone on retention, in normal and in protein- malnourished rats

Rats raised and maintained on a normal-protein diet (25% protein) responded to the ip adminsitration of ACTH-(1-24), epinephrine or Met-enkephalin with a decrease in hypothalamic Beta-endorphin-like immunoreactivity, which is attributable to a release of this substance. This effect was not seen in rats raised an maintained on a low-protein diet (8% protein). In the normal animals, the pre-test administration of ACTH, epinephrine or Met-enkephalin and the post-training adminsitration of naloxone enhanced retention-test performance of a step-down inhibitory avoidance task. These behavioral effects were absent in the protein-malnourished rats. Previous studies have shown that the behavioral effect of post-training naloxone is secondary to the release of brain Beta-endorphin during training, and that the pre-test it is not likely that the differences were caused by hyperreactivity to the aversive stimuli employed, the suggested interpretation is that protein-malnourished rats present a dysfunction in the brain Beta-endorphin system which renders it unresponsive not only to novel training experiences, but also to the pre-test retrieval enchancing effects of ACTH, epinephrine and Met-enkephalin

Participation of opiate pathways in the lateral hypothalamic area in the control of renal electrolyte and water excretion

Injection of Met-enkephalin (0.05, 0.25 and 0.50 µg in 1 µl) solutions into the lateral hypothalamic area (LHA), of unrestrained and unanesthetized rats caused a significant decrease of sodium (0.30 ñ 0.13 to 0.07 ñ 0.01, P < 0.05) and potassium (0.61 ñ 0.17 to 0.21 ñ 0.04, P < 0.05) excretion. When the blocking agent nalaxone (0.20 µg in 1 µl) was injected alone, a signifricant increase of sodium (0.34 ñ 0.04 to 0.96 ñ 0.28, P < 0.05) and potassium (0.76 ñ 0.13 to 1.72 ñ 0.30, P < 0.05) excretion was observed. However, a dose-response relationship was not observed. However, when in another experiment naloxone was injected before Met-enkepalin into the same area, reversal of the effect of naloxone occured, with decreased sodium and potassium excretion. We conclude that the enkephalinergic pathway of the LHA when stimulated with Met-enkephalin plays an inhibitory role in the contorl of sodium and potassium excretion

Efecto combinado de angiotensina II, met-encefalina y acetilcolina administradas intracerebroventricularmente sobre la presión arterial media en ratas albinas / Combined effect of intracerebroventricular injections of angiotensin II, met-enkephalin and acetylcholine on mean arterial pressure in albino rats

Se probó el efecto de la inyección intracerebroventricular de varios neurotransmisores, dados en forma independiente y combinada (Ang. II, 200 ng; ACh., 6 µg; y met-encefalina, 50 µg) sobre la presión arterial media (PAM) de ratas albinas de la cepa Sprague-Dawley. Bajo anestesia con nembutal (35mg/Kg), se implantó una cánula metálica en el tercer ventrículo por los medios esteriotáxicos usuales y al tercer día el animal se anestesió de nuevo para la medición de la presión carótidea mediante un transductor de presión y registro continuo en un polígrafo fisiológico. La Ang. II aumentó la PAM; la acetilcolina mostró un aumento significativo en los primeros cinco minutos luego de la inyección y la met-encefalina no mostró ningún cambio significativo en al PAM. El efecto combinado mostró resultados interesantes. En vez de una potenciación del aumento de la presión arterial media, cuando ACh. y Ang. II se administrarón conjuntamente, no se observaron cambios estadísticamente significativos, por lo que su efecto se neutralizó. También, la met-encefalina bloqueó la respuesta hipertensora de la Ag. II al darse en forma combinada. Esto es compatible con la acción inhibitoria de la met-encefalinaen el sistema neuronal angiotensinérgico. Se especula acerca de un modelo hipotético que explica los hallazgos observados