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(AU)

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(AU)

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.

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

Methionine-enkephalin (Met-Enk) is an endogenous opioid pentapeptide derived from the prohormone proenkephalin A, present in neuroendocrine and hematopoietic cells. Enkephalins are known to play an important role on the processes of induction, activation and control of immunomodulatory events. Met-Enk has been considered a potent antitumoral agent. The present study shows that Met-Enk exerts an inhibitory effect on the growth of a macrophage derived fibrous histiocytoma (MC-II) inoculated intradermally into BALB/cJ mice. Such effect was mainly influenced by the protocol, route of administration and concentration of Met-Enk used for treatment. Neither higher doses of Met-Enk injected intracerebrally or subcutaneously, nor the use of various protocols of treatment, did modify the process of tumorigenesis. In contrast, low dose (0.25 mg/kg) of Met-Enk injected intracerebrally together with tumor inoculation, significantly reduced tumor growth and prolonged survival rate.

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 post-training beta-endorphin and Met-enkephalin administration on two-way active avoidance task in well-nourished and protein malnourished rats.

Protein malnutrition during suckling period or throughout the life affects the hypothalamic beta-endorphinergic system of adult rats. In the present study, rats were undernourished during suckling by feeding their dams an 8% casein diet whereas well-nourished dams received a 25% casein diet from birth until weaning (21 day of postnatal life). After weaning, the offsprings were maintained with the same diet as their dams. When rats were 3 month-old, they were subjected to two-way active avoidance task. Protein malnutrition did not affect the performance in the two-way active avoidance task. Post-training beta-endorphin or Met-enkephalin administration impaired the retention of shuttle avoidance task in both well-nourished and undernourished rats. However, the amnesic effect of the peptides was only achieved in undernourished rats with higher doses of opioids when compared to the well-nourished rats. These data suggest that undernourished rats present alterations in opioid sensitivity which may be related to changes in the levels of beta-endorphin previously observed both in brain and hypothalamus of early undernourished adult rats.

Conditioned place preference produced by infusion of Met-enkephalin into the medial preoptic area.

The conditioned place preference procedure was used to evaluate the rewarding properties of D-Ala2-Met5-enkephalinamide (DALA) after bilateral infusion into the medial preoptic area. Doses of 60, 250 and 100 ng/cannula were used. It was found that all doses of DALA produced place preference. This suggests that the medial preoptic area is a structure where opioid reward is produced in doses as low as those required in already established reward systems. The significance of this in relation to sexual reward is discussed.

Effects of ACTH, epinephrine and Met-enkephalin on brain beta-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 administration 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 and 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 administration 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 effect of the hormones is due to a release of brain beta-endorphin induced by the substances themselves. Since 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 enhancing 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 micrograms in 1 microliter) solutions into the lateral hypothalamic area (LHA) of unrestrained and unanesthetized rats caused a significant decrease of sodium (0.39 +/- 0.13 to 0.07 +/- 0.01, P less than 0.05) and potassium (0.61 +/- 0.17 to 0.21 +/- 0.04, P less than 0.05) excretion. When the blocking agent naloxone (0.20 micrograms in 1 microliter) was injected alone, a significant increase of sodium (0.34 +/- 0.04 to 0.96 +/- 0.28, P less than 0.05) and potassium (0.76 +/- 0.13 to 1.72 +/- 0.30, P less than 0.05) excretion was observed. However, a dose-response relationship was not observed. However, when in another experiment naloxone was injected before Met-enkephalin into the same area, reversal of the effect of naloxone occurred, 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 control of sodium and potassium excretion.

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

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

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

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 Ag; y met-encefalina, 50 Ag) 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 (AU)

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

Single and combined effects of intracerebroventricular bolus injection of Ang. II (200 ng), ACh (6 micrograms) and met-enkephalin (50 micrograms) on mean arterial pressure (MAP), was tested in Sprague-Dawley albino rats. A metallic cannula was implanted in the third ventricle according to standard stereotaxic procedures under pentobarbital anesthesia (35 mg/kg). On the third day, the animal was anesthetized again, a carotid artery was cannulated and connected to a pressure transducer for recording of MAP. Ang. II increased MAP; ACh produced a significant increase in the initial 5 minutes after injection and met-enkephalin did not induce any significant changes in MAP. The combined effect showed interesting results. Instead of a potentiation of the rise in MAP, Ang. II and ACh, when given together, did not show any significant changes. Also, met-enkephalin blocked the hypertensive response due to Ang. II, if given combined. This is compatible with an inhibitory action of met-enkephalin on an angiotensinergic neuronal system. A simplified hypothetical model that explains the findings described above is proposed as a working hypothesis.