Determination of apparent metabolizable energy of crude glycerin in broilers chickens

The objective of the experiment was to determine the Apparent Metabolizable Energy corrected for nitrogen (AMEn) of a glycerin product derived from biodiesel production for broilers. A number of 35 male Ross 308 broilers, with 35 days of age was fed ad libitum diets containing 0, 5, 10, 15, or 20% glycerin. AMEn was determined using total excreta collection, with four days of adaptation and three days of collection. Increasing glycerin intakes resulted in increased water excretion. Glycerin AMEn varied as a function of dietary inclusion levels, and a cubic equation was identified by regression analysis. Maximum AMEn level- 4890 kcal/kg DM- was obtained with 15% glycerin inclusion. However, this level caused excessive water excretion, making its use unpractical.

Determination of apparent metabolizable energy of crude glycerin in broilers chickens

The objective of the experiment was to determine the Apparent Metabolizable Energy corrected for nitrogen (AMEn) of a glycerin product derived from biodiesel production for broilers. A number of 35 male Ross 308 broilers, with 35 days of age was fed ad libitum diets containing 0, 5, 10, 15, or 20% glycerin. AMEn was determined using total excreta collection, with four days of adaptation and three days of collection. Increasing glycerin intakes resulted in increased water excretion. Glycerin AMEn varied as a function of dietary inclusion levels, and a cubic equation was identified by regression analysis. Maximum AMEn level- 4890 kcal/kg DM- was obtained with 15% glycerin inclusion. However, this level caused excessive water excretion, making its use unpractical.

Fatty-Acid composition of free-choice starter broiler diets

Two experiments were carried out to evaluate the inclusion of vegetable oils with different fatty acid content in starter and pre-starter broiler diets. In Experiment I 480 1- to 9-day-old male Ross 308 broilers were fed diets containing corn oil (CO), acid corn oil (ACO), linseed oil (LO) or coconut fat (CoF). Chicks were distributed according to a factorial 2x2x2arrangement (2 free fatty acids - FFA ) x (2 n6:n3 ratios) x (2 medium-chain fatty acids levels - AGMC). Performance responses and dry matter (DMM), crude protein (CPM), and crude fat (CFM) metabolizability were evaluated. In Experiment II, 480 1- to 20-day-old male Ross 308 broilers were offered the free choice of 2 different diets: with no fat addition, or with 10% addition of the following fat sources: CO, LO, CoF, soybean soapstock (SBS), acid soybean oil (ASO), or acid cottonseed oil (ACtO). Performance responses and diet selection were evaluated. In experiment I, there were no significant effects of the diets on performance, DMM, or CPM; however, the inclusion of FFA depressed CFM. In experiment II, there was a marked preference of birds of the diets with fat inclusion, leading to the selection of diets with more than 3100 kcal/kg ME in the period of 1 to 20 days, independently of fat source. The broilers selected the high fat and energy diets since the first days of age, which resulted in better bird performance.

Fatty-Acid composition of free-choice starter broiler diets

Two experiments were carried out to evaluate the inclusion of vegetable oils with different fatty acid content in starter and pre-starter broiler diets. In Experiment I 480 1- to 9-day-old male Ross 308 broilers were fed diets containing corn oil (CO), acid corn oil (ACO), linseed oil (LO) or coconut fat (CoF). Chicks were distributed according to a factorial 2x2x2arrangement (2 free fatty acids - FFA ) x (2 n6:n3 ratios) x (2 medium-chain fatty acids levels - AGMC). Performance responses and dry matter (DMM), crude protein (CPM), and crude fat (CFM) metabolizability were evaluated. In Experiment II, 480 1- to 20-day-old male Ross 308 broilers were offered the free choice of 2 different diets: with no fat addition, or with 10% addition of the following fat sources: CO, LO, CoF, soybean soapstock (SBS), acid soybean oil (ASO), or acid cottonseed oil (ACtO). Performance responses and diet selection were evaluated. In experiment I, there were no significant effects of the diets on performance, DMM, or CPM; however, the inclusion of FFA depressed CFM. In experiment II, there was a marked preference of birds of the diets with fat inclusion, leading to the selection of diets with more than 3100 kcal/kg ME in the period of 1 to 20 days, independently of fat source. The broilers selected the high fat and energy diets since the first days of age, which resulted in better bird performance.

Compensatory water consumption of broilers submitted to water restriction from 1 to 21 days of age

A hundred and fifty male Ross 308 broilers were submitted to water restriction (WR) in different levels (0 to 40%) until 21 days of age. The birds received water ad libitum from 22 to 28 days of age and the compensatory consumption of water (CConW) was calculated as the difference in water intake between birds submitted and not submitted to WR. All WR groups showed a compensatory consumption of water, mainly during the first days of the ad libitum period. The water intake in such groups decreased as the birds adapted to the new condition. Higher water intake was observed in birds with 30 and 40% WR than in birds with 10% WR. Furthermore, chickens showed an unusual drinking and feeding behavior during the restriction period.

Compensatory water consumption of broilers submitted to water restriction from 1 to 21 days of age

A hundred and fifty male Ross 308 broilers were submitted to water restriction (WR) in different levels (0 to 40%) until 21 days of age. The birds received water ad libitum from 22 to 28 days of age and the compensatory consumption of water (CConW) was calculated as the difference in water intake between birds submitted and not submitted to WR. All WR groups showed a compensatory consumption of water, mainly during the first days of the ad libitum period. The water intake in such groups decreased as the birds adapted to the new condition. Higher water intake was observed in birds with 30 and 40% WR than in birds with 10% WR. Furthermore, chickens showed an unusual drinking and feeding behavior during the restriction period.

Different sodium levels and electrolyte balances in pre-starter diets for broilers

An experiment with 400 one-day-old male chicks (Ross) was conducted to evaluate the effects of different Na levels (0.10, 0.22, 0.34 and 0.46%) and different cation/anion balances (Na+K-Cl) (100, 150, 200, 250 and 300 meq/kg) in pre-starter diets on broiler performance. The corn and soybean-based diets had 22% crude protein and 2,900 kcal/kg metabolizable energy and were fed ad libitum. Performance data showed a positive quadratic effect of increasing Na levels on feed and water consumption, weight gain and feed conversion. Na+K-Cl also had a quadratic influence on feed intake and weight gain. None of the effects tested affected the amount of water measured in excreta. Derivatives of obtained regression equations pointed to optimal Na levels of 0.45% for water consumption, 0.40% for feed intake and weight gain and 0.38% for feed conversion. As to the effect of dietary Na+K-Cl balances on performance, regression equation values were 174 meq/kg for feed consumption and 163 meq/kg for weight gain. These results show that both Na level and Na+K-Cl balance interfere on broiler performance.

Effect of energy levels of diets formulated on total or digestible amino acid basis on broiler performance

This study was conducted to evaluate the performance and carcass and breast yields of broilers fed two different energy levels (3,200 or 2,900 kcal ME/kg) and two ways of expressing amino acid requirements (total - TAA or digestible - DAA) between 21 and 42 days of age. The results showed that broilers fed the diet containing 3,200 kcal ME/kg had higher weight gain (P=0.015), better feed conversion (P=0.001), and higher abdominal fat deposition (P=0.001) as compared to those fed the diet containing 2,900 kcal ME/kg. Diets formulated on DAA basis promoted higher weight gain (P=0.043), better feed conversion (P=0.010) and better conversion of ME intake into weight gain (P=0.007) as compared to those formulated on TAA basis. The results of this study suggest that formulation based on DAA is necessary if the diets contain protein sources that are not reliable in terms of amino acid digestibility. The response to formulation based on DAA was minimized when birds received the low energy level diet (2,900 kcal ME/kg).

Effect of energy levels of diets formulated on total or digestible amino acid basis on broiler performance

This study was conducted to evaluate the performance and carcass and breast yields of broilers fed two different energy levels (3,200 or 2,900 kcal ME/kg) and two ways of expressing amino acid requirements (total - TAA or digestible - DAA) between 21 and 42 days of age. The results showed that broilers fed the diet containing 3,200 kcal ME/kg had higher weight gain (P=0.015), better feed conversion (P=0.001), and higher abdominal fat deposition (P=0.001) as compared to those fed the diet containing 2,900 kcal ME/kg. Diets formulated on DAA basis promoted higher weight gain (P=0.043), better feed conversion (P=0.010) and better conversion of ME intake into weight gain (P=0.007) as compared to those formulated on TAA basis. The results of this study suggest that formulation based on DAA is necessary if the diets contain protein sources that are not reliable in terms of amino acid digestibility. The response to formulation based on DAA was minimized when birds received the low energy level diet (2,900 kcal ME/kg).

Different sodium levels and electrolyte balances in pre-starter diets for broilers

An experiment with 400 one-day-old male chicks (Ross) was conducted to evaluate the effects of different Na levels (0.10, 0.22, 0.34 and 0.46%) and different cation/anion balances (Na+K-Cl) (100, 150, 200, 250 and 300 meq/kg) in pre-starter diets on broiler performance. The corn and soybean-based diets had 22% crude protein and 2,900 kcal/kg metabolizable energy and were fed ad libitum. Performance data showed a positive quadratic effect of increasing Na levels on feed and water consumption, weight gain and feed conversion. Na+K-Cl also had a quadratic influence on feed intake and weight gain. None of the effects tested affected the amount of water measured in excreta. Derivatives of obtained regression equations pointed to optimal Na levels of 0.45% for water consumption, 0.40% for feed intake and weight gain and 0.38% for feed conversion. As to the effect of dietary Na+K-Cl balances on performance, regression equation values were 174 meq/kg for feed consumption and 163 meq/kg for weight gain. These results show that both Na level and Na+K-Cl balance interfere on broiler performance.

Performance of female broiler breeders submitted to different feeding schedules

The performance of Arbor Acres broiler breeders (1,296 females; 144 roosters) was evaluated when submitted to the following treatments (T): T1 = feeding at 6:30 a.m. (control); T2 = 50% feeding at 6:30 a.m. and 50% at 3:30 p.m. (dual feeding); T3 = feeding at 11:00 a.m.; and T4 = feeding at 3:30 p.m. Treatments were randomly distributed in 48 pens. There were 27 females and 3 males in each pen and 12 repetitions per treatment. Nutrition and management were as recommended for the commercial strain. It was evaluated age at first egg (AFE), total egg production (TEP), number of days with production above 80% (DAP80), laying peak (P), female mortality (MOR), and gross profit margin (GM) per hen. Data were submitted to analysis of variance and means were compared by Student's t-Test. TEP of T1 (186.3±2.3) and T2 (186.5±1.5) were higher (p 0.05) than that of other treatments. TEP of T3 (177.2±2) was the smallest (p 0.05), probably due to the less significant values of DAP80 (18.9±6.0 days) and P (81.36±0.95%). AFE was earlier (p 0.05) in T2 birds. Mortality was similar (p>0.10) among treatments. GM per hen was better (p 0.05) in T1 and T2 hens. Control and dual treatments were more efficient than other treatments. It was concluded that it is possible to change conventional feeding management's by the dual feeding system.

Influence of feeding time on sexual maturity and carcass composition in female broiler breeders

One thousand two hundred and ninety six Arbor Acres females and 144 males were used to study the influence of feeding time on sexual maturity and carcass composition. Treatments were: T1 = feeding at 6:30 am, T2 = 50% feeding at 6:30 am and 50% at 3:30 pm (dual), T3 = feeding at 11:00 am, T4 = feeding at 3:30 pm. Nutrition and management were as recommended to the commercial line. Variables studied were: sexual maturity at 5% production (SM), mean egg production percentage (PEP) body weight (BW), carcass composition, tibia weight (TIBW) and tibia calcium (Ca) and phosphorus (P) contents. Analysis of variance was used, and the means were compared using Student's t test. T2 females reached SM at 25.92 weeks, which was earlier (p 0.01) than the other treatments. PEP was greater (p 0.01) for T1 and T2 than for the other treatments. BW was greater in T1 and smaller in T4 (p 0.05) than in the other treatments. TIBW was greater in T3 than in T1 and T2 (p 0.05), with no effect (p>0.10) on carcass dry matter (DM), ether extract (EE), crude protein (CP) and ash (ASH). DM, EE, TIBW, Ca and P increased (p 0.05) whereas CP and ASH decreased with age. Time of feeding influenced body weight, but not carcass composition. Hens fed twice a day had earlier sexual maturity and similar egg production compared to those fed once at 6:30 am.

Influence of feeding time on sexual maturity and carcass composition in female broiler breeders

One thousand two hundred and ninety six Arbor Acres females and 144 males were used to study the influence of feeding time on sexual maturity and carcass composition. Treatments were: T1 = feeding at 6:30 am, T2 = 50% feeding at 6:30 am and 50% at 3:30 pm (dual), T3 = feeding at 11:00 am, T4 = feeding at 3:30 pm. Nutrition and management were as recommended to the commercial line. Variables studied were: sexual maturity at 5% production (SM), mean egg production percentage (PEP) body weight (BW), carcass composition, tibia weight (TIBW) and tibia calcium (Ca) and phosphorus (P) contents. Analysis of variance was used, and the means were compared using Student's t test. T2 females reached SM at 25.92 weeks, which was earlier (p 0.01) than the other treatments. PEP was greater (p 0.01) for T1 and T2 than for the other treatments. BW was greater in T1 and smaller in T4 (p 0.05) than in the other treatments. TIBW was greater in T3 than in T1 and T2 (p 0.05), with no effect (p>0.10) on carcass dry matter (DM), ether extract (EE), crude protein (CP) and ash (ASH). DM, EE, TIBW, Ca and P increased (p 0.05) whereas CP and ASH decreased with age. Time of feeding influenced body weight, but not carcass composition. Hens fed twice a day had earlier sexual maturity and similar egg production compared to those fed once at 6:30 am.

Performance of female broiler breeders submitted to different feeding schedules

The performance of Arbor Acres broiler breeders (1,296 females; 144 roosters) was evaluated when submitted to the following treatments (T): T1 = feeding at 6:30 a.m. (control); T2 = 50% feeding at 6:30 a.m. and 50% at 3:30 p.m. (dual feeding); T3 = feeding at 11:00 a.m.; and T4 = feeding at 3:30 p.m. Treatments were randomly distributed in 48 pens. There were 27 females and 3 males in each pen and 12 repetitions per treatment. Nutrition and management were as recommended for the commercial strain. It was evaluated age at first egg (AFE), total egg production (TEP), number of days with production above 80% (DAP80), laying peak (P), female mortality (MOR), and gross profit margin (GM) per hen. Data were submitted to analysis of variance and means were compared by Student's t-Test. TEP of T1 (186.3±2.3) and T2 (186.5±1.5) were higher (p 0.05) than that of other treatments. TEP of T3 (177.2±2) was the smallest (p 0.05), probably due to the less significant values of DAP80 (18.9±6.0 days) and P (81.36±0.95%). AFE was earlier (p 0.05) in T2 birds. Mortality was similar (p>0.10) among treatments. GM per hen was better (p 0.05) in T1 and T2 hens. Control and dual treatments were more efficient than other treatments. It was concluded that it is possible to change conventional feeding management's by the dual feeding system.

Granulometria do Milho em Rações de Crescimento de Frangos de Corte e seu Efeito no Desempenho e Metabolismo

Two experiments were carried out to evaluate corn particle size, expressed by the average geometric diameter (AGD), .0.337; 0.574; 0.680; 0.778; 0.868 e 0.936mm on performance, energetic metabolism and intestinal morphology (villi height and crypts depth of duodenum) of 21 to 42 day-old male broilers. In the first experiment, particle size of 0.868 mm showed greater feed intake and weight gain and better feed conversion. Villi height was not affected by the AGD of the diets, but increased with the broilers age (21, 35 and 42 days of age). Abdominal fat deposition was not affected neither the proportion of carcass cuts. Gizzard weight was positively related with particle size. In the second experiment, feed with particle size of 0.337 mm led to a lower energy intake and greater gross energy excretion. Nitrogen retention was not affected by particle size.

Foram realizados dois experimentos para avaliar os efeitos da granulometria do milho das rações, expressa pelo diâmetro geométrico médio (DGM), 0,337; 0,574; 0,680; 0,778; 0,868 e 0,936mm, sobre o desempenho, o metabolismo energético e a morfologia intestinal (número e altura de vilosidades do duodeno) de frangos de corte machos, de 21 aos 42 dias de idade. No 1° experimento, partículas de 0,868 mm proporcionaram às aves maior consumo de ração, maior ganho de peso e melhor conversão alimentar. A altura das vilosidades intestinais não foi influenciada pelo DGM das dietas, mas aumentou com a idade das aves (21, 35 e 42 dias de idade). Não foi observado efeito da granulometria sobre a deposição de gordura abdominal ou sobre as proporções das partes da carcaça. O peso da moela esteve positivamente relacionado com o aumento da granulometria das dietas. No 2° experimento, as aves alimentadas com milho de 0,337 mm apresentaram menor consumo de energia metabolizável e maior excreção de energia bruta. A granulometria não influenciou na retenção de nitrogênio.

Granulometria do Milho em Rações de Crescimento de Frangos de Corte e seu Efeito no Desempenho e Metabolismo

Two experiments were carried out to evaluate corn particle size, expressed by the average geometric diameter (AGD), .0.337; 0.574; 0.680; 0.778; 0.868 e 0.936mm on performance, energetic metabolism and intestinal morphology (villi height and crypts depth of duodenum) of 21 to 42 day-old male broilers. In the first experiment, particle size of 0.868 mm showed greater feed intake and weight gain and better feed conversion. Villi height was not affected by the AGD of the diets, but increased with the broilers age (21, 35 and 42 days of age). Abdominal fat deposition was not affected neither the proportion of carcass cuts. Gizzard weight was positively related with particle size. In the second experiment, feed with particle size of 0.337 mm led to a lower energy intake and greater gross energy excretion. Nitrogen retention was not affected by particle size.

Foram realizados dois experimentos para avaliar os efeitos da granulometria do milho das rações, expressa pelo diâmetro geométrico médio (DGM), 0,337; 0,574; 0,680; 0,778; 0,868 e 0,936mm, sobre o desempenho, o metabolismo energético e a morfologia intestinal (número e altura de vilosidades do duodeno) de frangos de corte machos, de 21 aos 42 dias de idade. No 1° experimento, partículas de 0,868 mm proporcionaram às aves maior consumo de ração, maior ganho de peso e melhor conversão alimentar. A altura das vilosidades intestinais não foi influenciada pelo DGM das dietas, mas aumentou com a idade das aves (21, 35 e 42 dias de idade). Não foi observado efeito da granulometria sobre a deposição de gordura abdominal ou sobre as proporções das partes da carcaça. O peso da moela esteve positivamente relacionado com o aumento da granulometria das dietas. No 2° experimento, as aves alimentadas com milho de 0,337 mm apresentaram menor consumo de energia metabolizável e maior excreção de energia bruta. A granulometria não influenciou na retenção de nitrogênio.

Avaliação das Propriedades do Ácido Nicotínico no Desempenho e no Balanço Térmico de Frangos de Corte Durante Estresse por Calor

Four doses of nicotinic acid, added in the drinking water of broilers, were offered in order to study its effect on performance and heat production in heat stress conditions (6 h of 35° C). Doses were 15, 100, 330 and 1000 mg/L. There was no effect of dose on weight gain, feed intake, feed efficiency, water intake and rectal temperature. Slight changes due to the doses of nicotinic acid and heat stress in the blood parameters of the birds were noted. Heat production (kcal/h/metabolic weight) decreased in 100 and 1000 mg/L dose as compared to 15 mg/L dose. There was no benefit using nicotinic acid in those doses in heat stress alleviation.

Foram oferecidas 4 doses de ácido nicotínico (AN) na água de beber de frangos de corte, a fim de estudar seu efeito no desempenho e na produção de calor em condições de estresse por calor (6 h de 35º C). As doses foram 15, 100, 330 e 1000 mg/L. Não houve efeito do AN nas doses usadas para ganho de peso, consumo de alimento, eficiência alimentar, consumo de água e temperatura retal. Foram observadas algumas alterações devido ao AN e estresse por calor nos parâmetros sangüíneos das aves. A produção de calor (kcal/h/peso metabólico) diminuiu com o uso de 100 e 1000 mg/L comparados com 15 mg/L. Nas dosagens usadas não foi observado efeito benéfico do AN no controle do estresse por calor.

Avaliação das Propriedades do Ácido Nicotínico no Desempenho e no Balanço Térmico de Frangos de Corte Durante Estresse por Calor

Four doses of nicotinic acid, added in the drinking water of broilers, were offered in order to study its effect on performance and heat production in heat stress conditions (6 h of 35° C). Doses were 15, 100, 330 and 1000 mg/L. There was no effect of dose on weight gain, feed intake, feed efficiency, water intake and rectal temperature. Slight changes due to the doses of nicotinic acid and heat stress in the blood parameters of the birds were noted. Heat production (kcal/h/metabolic weight) decreased in 100 and 1000 mg/L dose as compared to 15 mg/L dose. There was no benefit using nicotinic acid in those doses in heat stress alleviation.

Foram oferecidas 4 doses de ácido nicotínico (AN) na água de beber de frangos de corte, a fim de estudar seu efeito no desempenho e na produção de calor em condições de estresse por calor (6 h de 35º C). As doses foram 15, 100, 330 e 1000 mg/L. Não houve efeito do AN nas doses usadas para ganho de peso, consumo de alimento, eficiência alimentar, consumo de água e temperatura retal. Foram observadas algumas alterações devido ao AN e estresse por calor nos parâmetros sangüíneos das aves. A produção de calor (kcal/h/peso metabólico) diminuiu com o uso de 100 e 1000 mg/L comparados com 15 mg/L. Nas dosagens usadas não foi observado efeito benéfico do AN no controle do estresse por calor.

Suplementação de Treonina em Dietas de Frangos de Corte, Variando a Energia e as Relações Energia: Proteína

Two experiments (EXP) were carried out to investigate the metabolizable energy:crude protein ratios (ME:CP) and threonine addition (Thr) in high-energy (H) (3.200kcal ME/kg) and low-energy (L) (2.900kcal ME/kg) diets, on the performance and carcass composition of male broiler chickens. The ME:CP ratios were: 139 and 160kcal/% for starter diets (1 to 21 days of age) (EXP 1) and 160 and 181kcal/% for grower diets (22 to 40 days)(EXP 2), in both energy levels, keeping Met + Cys and Lys constant. Thr was supplemented to equalize its level to the lower EM:PB ratio. All birds received a unique diet after (EXP 1) or before (EXP 2) been fed with the experimental diets. In both EXP feeding H diets resulted in better performance -weight gain (WG), feed intake (FI) and feed conversion (FC) (p 0,01) at the end of each experimental period. However, in EXP 1, birds fed with L diets during the starter period had better caloric conversion (kcal/kg) (CC) in the total period (1 to 40 days), as an indicative of accelerated growth. The lower levels of Thr (0.74 and 0.69% for H and L diets, respectively) were not limiting for birds' performance. On EXP 2, the 181 ME:CP decreased WG (p 0.08) and increased FC (p 0.01) in both energy levels. Thr was not a limiting amino acid in initial practical diets (1 to 21 days of age). On the other hand, Thr supplementation improved performance of birds at 181 E:CP (22 to 40 days) (EXP2). Thr addition did not influence carcass composition in both EXP.

Dois experimentos (EXP 1 e 2) foram conduzidos para avaliar relações energia metabolizável:proteína bruta (EM:PB) e a adição de treonina (Thr) em dietas com alta (A) (3.200kcal EM/kg) e baixa (B) (2.900kcal EM/kg) energia, sobre desempenho e composição de carcaças de frangos de corte machos. As relações energia:proteína foram 139 e 160 kcal/%, para as dietas iniciais (1 a 21 dias) (EXP 1) e 160 e 181kcal/%, para as de crescimento (22 a 40 dias) (EXP 2), nos dois níveis de energia. As dietas com ampla relação EM:PB foram suplementadas, ou não, com Thr a fim de iguala-las às dietas com menor EM:PB. Os níveis de Met+Cys e de Lys foram constantes. As aves receberam uma dieta única após (EXP1), ou antes (EXP2) do fornecimento das dietas experimentais. Nos dois EXP as dietas A proporcionaram melhor desempenho: ganho de peso (GP),consumo de ração e conversão alimentar (CA) (p 0,01), ao final de cada período experimental. Porém, no EXP 1, as aves que receberam dietas B tiveram melhor conversão calórica (CC, kcal/kg,) (p 0,01) no período total (1 a 40 dias), indicando um período de crescimento acelerado. Os níveis de Thr (0,74 e 0,69% para A e B respectivamente) das dietas com relação EM:PB ampla não foram limitantes no desempenho das aves. No EXP 2, a EM:PB 181 deprimiu o GP (p 0,08) e piorou a CA (p 0,01), nas energias A e B. Portanto, em dietas práticas iniciais, Thr não foi um aminoácido (AA) limitante. Porém, de 22 a 40 dias, a adição de Thr foi necessária, em dietas com EM:PB 181kcal/%(EXP 2). A suplementação de Thr não influenciou a composição das carcaças nos dois EXP.

Efeito da Energia, Relação Energia: Proteína e Fase de Crescimento Sobre o Desempenho e Composição de Carcaça de Frangos de Corte

Two experiments (EXP) were carried out to investigate the effects of crude protein (CP) levels reduction in high-energy (H) (3.200kcal ME/kg) and low-energy (L) (2.900kcal ME/kg) diets, on the performance and carcass composition of male broiler chickens. The CP levels were decreased to meet the following energy: protein (E:PB) ratios: 139, 146, 153 and 160 (kcal/%) for starter diets (EXP 1) and 160, 167, 174 and 181 (kcal/%) for grower diets (EXP 2), in both energy levels, keeping MET + CIS and LYS levels at the same concentration. All birds received a same diet before (EXP 2) or after (EXP 1) feeding the experimental diets. Feeding H diets resulted in better performance, but also in higher carcass fat deposition. In EXP 1, birds fed with L diets during the starter period had similar body weight gain (BWG), in the total period (1 to 42 days), than those H diets, however with better caloric conversion (kcal/kg) (CC). Also, the best CC was obtained with E:PB of 139. Lower BWG, sometimes occurred with lower levels of dietary CP, but in all experiments the CC was decreased with wider E:PB ration. In both EXP, protein utilization was improved with higher levels of dietary energy and with lower levels of dietary CP.

Dois experimentos (EXP) avaliaram os efeitos da redução de proteína bruta (PB) em dietas com alta (A) (3.200kcal EM/kg) e baixa (B) (2.900kcal EM/kg) energia, sobre o desempenho e composição de carcaças de frangos de corte machos. Os níveis de PB foram reduzidos para obter as relações energia: proteína (E:PB) 139, 146, 153 e 160 (kcal/%) para as dietas iniciais (EXP 1), e 160, 167, 174 e 181(kcal/%) para as dietas de crescimento (EXP 2), em ambos os níveis de energia, mantendo constantes os níveis de MET+CIS e LIS. Todas as aves receberam uma mesma dieta antes (EXP 2) ou após (EXP 1) o fornecimento das dietas experimentais. O fornecimento das dietas A proporcionou melhor desempenho, no entanto resultou em maior deposição de gordura nas carcaças. No EXP 1, as aves alimentadas com as dietas B apresentaram ganho de peso (GP) similar àquelas alimentadas com as dietas A no período total (1 a 42 dias), porém melhor conversão calórica (CC) (kcal/kg) (p 0,01). Foi observada também melhor CC, com relação E:PB 139. Menores níveis de PB dietética resultaram, algumas vezes, em um menor GP, porém sempre foi verificada uma pior CC nas relações mais amplas E:PB. Em ambos os Experimentos (EXP), o maior nível de energia e a redução da PB dietética melhoraram a utilização da PB consumida.