Energy and protein requirements for maintenance of Texel lambs.

It can be hypothesized that the body composition characteristics of different sheep breeds affect their nutritional requirements. However, no study has yet been carried out to determine the nutritional requirements for maintenance of Texel purebred lambs, despite their growing importance in sheep meat production globally. Our objective was therefore to determine the energy and protein requirements for maintenance of Texel lambs. Thirty-four Texel lambs were used, all intact males that were weaned at 50 days old, and confined in individual pens. Two experiments were conducted, as follows. In Experiment 1, a digestibility assay was performed to determine the dietary energy value, in a 3×3 double Latin square design, in which lambs were submitted to three levels of feed restriction (0%, 55% and 70% of ad libitum feed intake). In Experiment 2, the energy and protein requirements for maintenance of Texel lambs from 21 to 40 kg BW were determined using a randomized block design, in which lambs were also submitted to three levels of feed restriction (0%, 55% and 70% of ad libitum feed intake). The requirements for net energy for maintenance (NEm), metabolizable energy for maintenance (MEm), net protein for maintenance (NPm) and metabolizable protein for maintenance (MPm) were determined. The digestibility of dry matter, energy, protein and metabolizability were similar between food restriction levels, averaging 74.4%, 75.5%, 80.3% and 0.636, respectively. The NEm determined for growing Texel lambs was 263 kJ/kg of the metabolic fasting BW (FBW), the MEm was 417 kJ/kg0.75 FBW and the efficiency of use of MEm was 0.63. In addition, the NPm was 1.24 g/day per kg0.75 FBW and the MPm was 2.98 g/day per kg0.75 FBW. The energy requirements of Texel lambs are different from those reported in the literature, possibly due to differences between breeds, diets and environmental effects, whereas the protein requirements are different from literature mainly due to methodological differences; further studies are need to address these aspects that affects the nutritional requirements for raising sheep from different breeds in different environments.

Prediction of physical characteristics of the lamb carcass using in vivo bioimpedance analysis.

The increase of sheep meat competitiveness in international markets can be attributed to the rise of the quantity and the improvement of the quality of the edible portion of sheep carcasses. Usually, carcass yield is established after the slaughter of the animals. Yet, when carcass yield is determined in vivo, it can be both a costly and subjective method. This study proposes models for predicting the physical characteristics of lamb carcass using bioimpedance analysis (BIA) in live animals. Thirty-one Texel × Ile de France crossbreed ram lambs were slaughtered at 20, 26, 32 or 38 kg of BW. Before the slaughter, values of resistance (Rs) and reactance (Xc) were collected using a single-frequency BIA equipment (Model RJL Quantum II Bioelectrical Body Composition Analyzer). Then, BIA main variables such as body bioelectrical volume (V), phase angle (PA), resistive density (RsD) and reactive density (XcD) were calculated. After slaughter, cold carcass weight (CCW), cold carcass yield (CCY), subcutaneous fat thickness (SFT), soft tissue weight (STW) and soft tissue yield (STY) were also measured. Multiple regression analyses were carried out using the physical characteristics as dependent variables and the bioimpedance values as independent variables. Predictive performance of the models was assessed using leave-one-out cross-validation. The prediction model of CCW was obtained using the V, PA and RsD (R2 = 0.97), STW through the V, RsD and XcD (R2 = 0.97), CCY by Rs, Z and XcD (R2 = 0.69), STY by V and XcD (R2 = 0.67), and SFT only for XcD (R2 = 0.84). The results indicated that BIA has the potential to predict carcass characteristics of lambs at different body masses.

Carcaça e componentes corporais de cordeiros lactentes em pastejo de azevém suplementados com leguminosa ou concentrado / Carcass and body components of suckling lambs grazing ryegrass and supplemented with legume or concentrate

O objetivo desta pesquisa foi avaliar o efeito da suplementação privativa, com concentrado ou leguminosa, sobre as características da carcaça e dos componentes corporais de cordeiros lactentes mantidos em pastejo de azevém. Foram utilizados 27 cordeiros lactentes, distribuídos nos tratamentos que corresponderam aos sistemas de alimentação: cordeiros lactentes mantidos em pasto de azevém, cordeiros lactentes mantidos em pasto de azevém e suplementados com concentrado em comedouro privativo (creep feeding) e cordeiros lactentes mantidos em pasto de azevém e suplementados com leguminosa no pasto privativo (creep grazing). O concentrado era composto por milho, farelo de soja e calcário calcítico, e a leguminosa utilizada foi o trevo-branco. O delineamento experimental foi o inteiramente ao acaso. Os resultados foram submetidos à análise de variância, e as médias comparadas pelo teste de Tukey a 5% de significância. O conteúdo do trato gastrintestinal juntamente com bile e urina e a proporção de esôfago foram maiores (P<0,05) nos cordeiros mantidos em pasto de azevém. As proporções de fígado e intestino grosso foram maiores (P<0,05) nos cordeiros suplementados com concentrado. Os sistemas alimentares testados produzem carcaças com características semelhantes. A suplementação, com leguminosa ou concentrado, altera os componentes corporais de cordeiros lactentes mantidos em azevém.(AU)

This research objective was to evaluate the effect of private supplementation with concentrated or legumes, on the carcass characteristics and body components from suckling lambs kept on ryegrass pasture. Twenty seven suckling lambs were used, with about 17 days of age and weighing 9,91±0,594kg, which were distributed in the treatments that corresponded to feeding systems: suckling lambs kept on ryegrass pasture, suckling lambs kept on ryegrass pasture and supplemented with concentrated in private feeder (creep feeding) and suckling lambs kept on ryegrass pasture and supplemented with legume in the private pasture (creep grazing). The concentrate supplement was composed by corn, soybean meal and limestone, and was supplied ad libitum. The supplementary pasture was white clover legume. The experimental design was completely randomized, where the results were submitted to analysis of variance and means compared by Tukey test at 5% of significance level. The gastrointestinal+bile+urine content and the proportion of esophagus were higher (P<0,05) in lambs kept on ryegrass. The liver and large intestine proportions were higher (P<0,05) in lambs supplemented with concentrate. The tested alimentary systems produce carcasses with similar characteristics. The supplementation with legume or concentrate cause changes in body components of suckling lambs grazing ryegrass.(AU)

Consumo e desempenho de cordeiros e borregos alimentados com dietas de alto concentrado de milho ou sorgo / Intake and performance of lambs and hoggets fed high concentrate corn or sorghum diets

Objetivou-se avaliar os consumos de matéria seca, nutrientes e desempenho na terminação de cordeiros e borregos submetidos a dietas de alto concentrado de grão de milho ou sorgo. Foram utilizados 32 animais, sendo 16 cordeiros (dente de leite) e 16 borregos (dois dentes) da raça Corriedale. As dietas eram constituídas de feno de aveia- branca (Avena sativa), grão de milho (Zea mays) ou de sorgo (Sorghum bicolor (L.) Moench), farelo de soja (Glycine Max), calcário calcítico, bicarbonato de sódio e monensina. Os cordeiros apresentaram superioridade (P≤0,05) quanto ao CMS (% do PV e g/kg PV0,75), ao CPB (kg/dia, % do PV e g/kg PV0,75), ao CEE (% do PV), ao CFDN e ao CFDA (% do PV e g/kg PV0,75), ao CNDT (% do PV), ao ganho de peso médio diário, à conformação in vivo e à conversão alimentar. Por outro lado, o CEE, o CCHT e o CCNE (kg/dia), o peso vivo inicial, o peso vivo final e o peso vivo ao abate foram superiores (P≤0,05) na categoria dos borregos. Em relação aos grãos avaliados, verificou-se maior (P≤0,05) CEE (kg/dia, % do PV e g/kg PV0,75) e menor (P≤0,05) CFDN (% do PV) e CFDA (kg/dia, % do PV e g/kg PV0,75) para os animais alimentados com dieta de alto concentrado à base de grão de milho em relação àqueles alimentados com grão de sorgo. Os cordeiros apresentam consumos relativos superiores aos borregos, porém sua resposta zootécnica é maior. O uso de dietas de alto concentrado de sorgo ou de milho proporcionou resultados semelhantes.(AU)

This study aimed to evaluate the dry matter, nutrient intake, and performance on feedlot of lambs and hoggets submitted to corn or sorghum high concentrate diets. Thirty-two Corriedale animals, being 16 lambs (milk teeth) and 16 hoggets (two teeth) were used. The diets were composed of white oat hay (Avena sativa), corn (Zea mays) or sorghum grain (Sorghum bicolor (L.) Moench), soybean meal (Glycine Max), limestone, sodium bicarbonate, and monensin. The lambs presented a superiority (P≤0.05) regarding the DMI (% of LW and g/kg LW0.75), CPI (kg/day, % of LW and g/kg LW0.75), EEI (% of LW), NDFI and ADFI (% of LW and g/kg LW0.75), TDNI (% of LW), daily average weight gain, conformation in vivo and feed conversion. On the other hand, the EEI, TCI, and NSCI (kg/day), the initial live weight, final live weight and the live weight at slaughter were superior (P≤0.05) in the hoggets category. In relation to the evaluated grains, a higher (P≤0.05) EEI (kg/day, % of LW and g/kg LW0.75) and a lower (P≤0.05) NDFI (% of LW) and ADFI (kg/day, % of LW and g/kg LW0.75) were verified for the animals fed with high concentrate diets based on corn grain in relation to those fed with sorghum grain. The lambs presented an intake relatively superior to the hoggets, however their zootechnical response is higher. The use of high concentrate diets of sorghum or corn provides similar results.

Consumo, desempenho e análise econômica da alimentação de cordeiros terminados em confinamento com o uso de dietas de alto grão / Consumption, performance and economic analysis of the feeding of lambs finished in feedlot as the use of high-grain diets

O presente experimento, conduzido no Laboratório de Ovinocultura da Universidade Federal de Santa Maria, teve como objetivo avaliar o efeito do uso de diferentes dietas de alto grão sobre o consumo de nutrientes e o desempenho de cordeiros terminados em confinamento, bem como realizar uma análise econômica da alimentação utilizada para terminação dos animais. Foram utilizados 32 cordeiros machos, castrados, da raça Texel, nascidos de parto simples e desmamados com aproximadamente 50 dias de idade. Os tratamentos foram constituídos por diferentes tipos de grãos, não processados, sendo: grão de milho, grão de aveia branca, grão de aveia preta ou grão de arroz com casca. Os animais foram abatidos quando atingiram o peso vivo de abate pré-estabelecido de 32kg, que corresponde a 60% do peso adulto de suas mães. Cordeiros alimentados com dietas de alto grão de milho apresentam maiores consumos de matéria seca, matéria orgânica, proteína bruta, carboidratos totais e de nutrientes digestíveis totais, menor consumo de fibra em detergente neutro, melhor escore de condição corporal, ganho de peso e conversão alimentar, o que leva à redução do número de dias no confinamento necessários para atingir o peso de abate. Além disso, cordeiros terminados com o uso de dieta de alto grão à base de grão de milho proporcionam melhor resultado econômico quando comparados com cordeiros terminados com as demais dietas de alto grão utilizadas neste experimento. O uso de dietas de alto grão de milho, aveia branca, aveia preta ou arroz com casca para terminação de cordeiros em sistema de confinamento é uma alternativa viável do ponto de vista produtivo. Porém, o uso de grão de milho proporciona melhores resultados produtivos e econômicos.

This experiment was conducted at the Laboratory of Sheep, Federal University of Santa Maria, and aimed to evaluate the effect of using different high-grain diets on nutrient intake and performance of lambs in a feedlot, as well as conduct an economic analysis of feeding used for termination of the animals. A total of 32 Texel breed castrated male lambs, born from a simple birth and weaned at approximately 50 days of age were used. The treatments consisted of different types of grains, unprocessed, as follows: corn grain, white oat grain, black oat grain or grain of rice in the husk. The animals were slaughtered when they reached a pre-established body weight of 32kg for slaughter, which corresponds to 60% of the mature weight of their mothers. Lambs fed diets with high corn grain have higher intakes of dry matter, organic matter, crude protein, total digestible nutrients and total carbohydrate, lower consumption of neutral detergent fiber and better body condition score, weight gain and feed conversion, which leads to reduction in the number of days in confinement needed to reach slaughter weight. In addition, lambs using high-grain diet based grain corn provide better economic results when compared with lambs with other high-grain diets used in this experiment. The use of diets high in grain corn, white oat grain, black oat grain or grain of rice in the husk for finishing lambs in feedlot is a viable alternative from a productive point of view. However, the use of corn grain provides better performance and economic results.

Características da carcaça e dos componentes não carcaça de cordeiros oriundos de parto simples ou duplo / Carcass and non-carcass traits of single and twin lambs

Um experimento foi conduzido com o objetivo de avaliar as características da carcaça e dos componentes não carcaça de cordeiros nascidos de parto simples ou duplo. Dezesseis cordeiros mestiços Texel × Ile de France, machos não castrados, foram desmamados aos 56 dias de idade e abatidos com aproximadamente 28kg de peso corporal. Imediatamente após o abate, cada componente corporal foi pesado separadamente, sendo as carcaças avaliadas após 24 horas de refrigeração a 2°C. Os cordeiros oriundos de parto simples apresentaram superioridade no peso e nos rendimentos da carcaça, além de maior área de olho de lombo. Por outro lado, proporcionalmente ao peso de corpo vazio, o rúmen é maior em cordeiros nascidos de parto duplo, o que resulta incremento da proporção de conteúdo gastrintestinal ao abate. Os resultados deste estudo indicam que, quando abatidos a um mesmo peso, cordeiros oriundos de parto simples possuem carcaças de melhor qualidade, em comparação a cordeiros nascidos de parto gemelar...

An experiment was conducted to evaluate the carcass and non-carcass traits of single and twin lambs. Sixteen Texel × Ile de France crossbred, non-castrated male lambs were weaned at 56 days of age and slaughtered at 28kg of body weight. Immediately after the slaughter each body component was individually weighed, while carcasses were evaluated after a 24h period of refrigeration at 2°C. Single lambs presented higher values of carcass weight and carcass dressing percentage. Moreover, the Longissimus muscle area was also greater for single lambs. On the other hand, as a proportion of empty body weight, rumen was greater for twin lambs, increasing their gastrointestinal content at slaughter. The results of this study indicated that at a same slaughter weight single lambs have better quality carcasses in comparison with those from twin lambs...

Características produtivas de cordeiros terminados em confinamento com dietas contendo diferentes teores de borra de soja / Productive characteristics of lambs finished in feedlot fed different levels of soybean soapstock

Avaliou-se o efeito de dietas contendo diferentes teores de borra de soja sobre o consumo de nutrientes, o ganho de peso, as características de carcaça e os componentes do peso vivo de cordeiros terminados em confinamento. Foram utilizados 25 cordeiros, machos, castrados, da raça Texel, distribuídos aleatoriamente em cinco tratamentos compostos por proporções de 0%, 2,89%, 5,77%, 8,65% ou 11,55% de borra de soja na matéria seca das dietas. Houve redução linear do consumo de nutrientes, com exceção do consumo de extrato etéreo, que aumentou linearmente. O peso vivo ao abate, o ganho de peso diário, os pesos e rendimentos de carcaça quente e fria, e os pesos de perna e de costilhar diminuíram linearmente, ao passo que as proporções de rúmen e do trato gastrintestinal, com conteúdo, bem como o conteúdo gastrointestinal, aumentaram linearmente com o aumento dos níveis de borra de soja nas dietas. A proporção de perna foi influenciada de forma quadrática. O aumento da participação de borra de soja na dieta de cordeiros em sistema de confinamento leva à diminuição do desempenho produtivo dos animais. Contudo, o lucro diário obtido por animal não é influenciado, podendo-se inferir que a inclusão de borra de soja até o nível de 11,55% da matéria seca total da dieta é uma alternativa viável para a terminação de cordeiros em confinamento.

We evaluated the nutrient intake, weight gain, carcass characteristics and the non carcass components of lambs in feedlot finishing diets containing increasing levels of soybean soapstock . We used 25 male lambs , castrated Texel , randomly distributed into five treatments consisting of proporti ons of 0 %, 2 . 89 %, 5. 77 %, 8 . 6 5 % or 11 .55 % of soybean soapstock i n the dry matter this diets. Linear reduction of nutrient intake was observed , with the exception of the consumption of ether extract , which increased linearly. The live weight at slaughter , th e daily weight gain , the weights and yields from hot and cold carcass and the weights of hindquarter and rib decreased linearly , while the p roportions of rumen and gastrointestinal tract, full and gastrointestinal tract content increased in a linear way as it increased the proportion of level this soybean soapstock in the diet. The proportion of hindquarter varied in a quadratic way. The increase in soybean soapstock in the diet of lambs in confinement system leads to decrease in productive performance of a nimals. However, the daily profit obtained per animal is not affected, and we may infer that the inclusion of soybean soapstock to the level of 11.55% of the total dry matter of the diet is a viable alternative to termination of feedlot lambs.

Glicerina bruta no suplemento e seus efeitos nas características da carcaça e nos componentes do peso vivo de cordeiros lactentes / Crude glycerin in supplement and its effects on carcass characteristics and live weight components in suckling lambs

Objetivou-se avaliar o efeito da porcentagem de glicerina bruta em suplementos sobre as características da carcaça e os componentes do peso vivo de cordeiros lactentes mantidos em pasto de azevém. Foram utilizados 32 cordeiros lactentes, distribuídos nos tratamentos: 0, 10, 20 e 30% de glicerina bruta na matéria seca, em substituição ao milho, no suplemento isoproteico (18% de PB na matéria seca) fornecido diariamente em quantidade equivalente a 2% do peso corporal. As porcentagens de glicerina bruta tiveram efeito linear decrescente sobre peso de carcaça quente, peso de carcaça fria, rendimento de carcaça quente e rendimento de carcaça fria, enquanto as perdas pelo jejum aumentaram. O peso da paleta e o peso do costilhar diminuíram, enquanto a proporção de perna aumentou com o incremento de glicerina bruta no suplemento. Na composição tecidual da paleta, observou-se que a gordura subcutânea, a gordura intermuscular e a gordura total da paleta decresceram linearmente segundo as porcentagens de glicerina bruta. Sobre os componentes do peso vivo, observaram-se diferenças nas proporções de pele, rúmen, omaso, intestino grosso, que aumentaram, enquanto a de gordura renal diminuiu linearmente. Conclui-se que o uso de glicerina bruta em até 30% em suplemento fornecido em comedouro privativo para cordeiros lactentes mantidos em pasto de azevém interfere nas características da carcaça e nos componentes corporais.

The objective was to evaluate the effect of crude glycerin levels in supplement on carcass characteristics and live weight components of suckling lambs maintained on ryegrass pasture. Thirty two suckling lambs were used and were distributed among the treatments: 0, 10, 20 and 30% crude glycerin, in replacement of corn, in the isoproteic supplement (18% CP) provided daily in amounts equivalent to 2% of body weight. The levels of crude glycerin had negative linear effects on hot and cold carcass weight, hot and cold carcass yield but an increasing effect was observed on gastrointestinal content and fasting losses. The shoulder and rib weights decreased, while the leg proportion increased with the elevation of crude glycerin use. In the tissue composition of the shoulder, it was observed that the subcutaneous fat, intermuscular fat and total fat decreased linearly according to the levels of crude glycerin. Regarding body weight components, differences were observed in the proportions of skin, rumen, omasum, large intestine, which increased, while the kidney fat decreases linearly. The use of crude glycerin in up to 30% in the supplement provided in creep feeding for suckling lambs kept in ryegrass pasture influences carcass characteristics and corporal components.

Chewing patterns and digestion in sheep submitted to feed restriction.

Two experiments were conducted to evaluate the relationship among the level of feed intake, chewing pattern, and diet digestibility in sheep fed a moderate-concentrate diet. The first experiment was conducted using six male lambs at a replicated 3 × 3 Latin square design to evaluate diet digestibility and microbial N synthesis according to the level of intake: ad libitum, or restricted to either 70 or 55% of the ad libitum intake. In the second experiment, fifteen male lambs were housed in individual stalls, in a completely randomized design, and fed one of the three levels of dry matter intake (DMI). Chewing patterns were then evaluated for 24 h using a regular 5-min interval observation technique, two times during the experimental period. Decreasing level of feed intake resulted in increased apparent digestibility of dry matter, organic matter, crude protein, and neutral detergent fibre, as well as of the true digestibility of organic matter. Total time spent eating and ruminating decreased with feed restriction. However, lambs fed at restricted levels of intake presented a higher rate of eating (g DMI/min) than those fed ad libitum, and spent more time ruminating each gram of DM (min/g DMI). In conclusion, our results suggest that a more effective chewing during rumination activity can have an important role on feed digestion in animals submitted to feed restriction.

Frequency of treatment and production performance using the FAMACHA method compared with preventive control in ewes.

The rapid escalation of anthelmintic resistance in parasites suggests the adoption of different strategies for parasite control in small ruminants instead of relying only on the use of chemicals. The integrated system of parasite control (SICOPA) program uses the FAMACHA method, which is used to separately identify sheep that are resistant/resilient or susceptible to Haemonchus contortus, or together with other management practices, such as pasture rotation or the monitoring of drug efficacy. The objective of this work was to compare two methods of parasite control in ewes. A flock of ewes (n=90) of Ile de France and Texel breeds was monitored from August 2001 to July 2003 under suppressive treatment (45-day treatment interval) and from August 2003 to July 2006 under the partial selective regimen based on FAMACHA evaluations. Fecal samples were collected for fecal egg counts (EPG) and larval identification to monitor infection during the 5-year period. After the partial selective evaluations, an average of 19% of the animals was treated each year between 2003 and 2006. The reproductive indexes of parturition (89%), birth rate (119%), lamb weight (4.1 kg) and lamb mortality (5.2%) were similar under the partial selective regimen and the previous suppressive treatment period. H. contortus was the most prevalent species, and EPG values were not statistically different across periods or among treatment regimes. The results demonstrate that the FAMACHA method allowed a large number of naturally infected ewes to be raised with reduced anthelmintic treatment without a negative impact on their reproductive indexes. It is indicated, though, that this method be applied together with other available strategies. Culling was based on clinical signs and ranged from 5.5 to 20% per year. The results suggest that an important host-specific effect may have regulated the rate of infection, expressing the resistant/resilient characteristic within the flock with an important economical benefit.

Energy requirements of Texel crossbred lambs.

Two trials were conducted to determine the energy requirements of feedlot Texel crossbred lambs. In a comparative slaughter trial, thirty 11/16 Texel x 5/16 Ile de France crossbred noncastrated male lambs, weaned at 42 d of age (16.2 +/- 2.1 kg of shrunk BW; SBW), were used. Five lambs were randomly chosen and slaughtered after 10 d of experimental management and diet adaptation (baseline group). Fifteen lambs then were fed for ad libitum intake and slaughtered at 25, 30, or 35 kg of SBW. The remaining 10 lambs were randomly assigned to 2 levels of DMI, either 70 or 55% of the ad libitum intake, and were slaughtered concomitantly with lambs of the 35 kg of SBW group. Total body N, fat, and energy contents were determined. In a digestibility trial, 6 Texel x Ile de France crossbred lambs (30.4 +/- 2.6 kg of SBW) were housed in metabolic cages and used in a replicated 3 x 3 Latin square experiment to evaluate the energetic value of the diet at different feed intake levels. Net and ME requirements for maintenance were 58.6 and 91 kcal/kg(0.75) of SBW, respectively. Consequently, partial efficiency of energy use for maintenance was 0.64. Body fat content varied from 72.7 to 125.9 g/kg of empty BW, respectively, for 13.1 and 28.2 kg of empty BW. Net energy requirements for growth of lambs at 15 and 35 kg of SBW at an ADG of 250 g were 424 and 553 kcal/d, respectively. Partial efficiency of energy use for growth was 0.47. Texel x Ile de France crossbred growing lambs used in this study showed decreased nutritional requirements than those reported by most nutritional systems.

Níveis de fibra em detergente neutro na dieta de cordeiros: consumo, digestibilidade e fermentação ruminal / Levels of neutral detergent fiber in lambs diets: intake, digestibility and ruminal fermentation

Foram utilizados oito cordeiros castrados (35,0±6,0kg peso vivo) em um delineamento duplo quadrado latino 4 ´ 4 para avaliar o efeito de quatro níveis de fibra em detergente neutro (FDN) na dieta (25, 31, 37 e 43 por cento da matéria seca (MS)) sobre o consumo e parâmetros digestivos. O consumo de nitrogênio (N) variou de forma quadrática; o de MS, matéria orgânica (MO) e energia diminuíram (P<0,05) e de FDN aumentou (P<0,01) linearmente com o aumento de fibra na dieta. A digestibilidade da FDN e do N, assim como o pH e as concentrações de peptídeos no fluído ruminal foram similares em todos os tratamentos. A digestibilidade aparente da MS, da MO e da energia, assim como as concentrações ruminais de açúcares diminuíram linearmente (P<0,01) e a síntese de proteína microbiana ruminal, as concentrações ruminais de amônia e de aminoácidos variaram quadraticamente (P<0,05) com o aumento do teor de FDN das dietas. A redução do consumo e da digestibilidade foram mais evidentes somente pela inclusão do nível mais alto de FDN (43 por cento) e, sob o aspecto nutricional, a inclusão em torno de 30 por cento de FDN representa o nível mais adequado para formulação de dietas a base de silagem de sorgo e concentrado oferecido a cordeiros confinados.

Eight castrated raw lambs (35.0± 6.0kg live weight) were used in a replicated 4 ´ 4 latin square design to evaluate the effect of four neutral detergent fiber (NDF) levels (25, 31, 37 and 43 percent of dry matter (DM)) on intake and digestion traits. Nitrogen (N) intake varied quadratically; intake of DM, organic matter (OM) and energy decreased (P<0.05) and that of NDF increased (P<0.01) as fibre level increased. NDF and N digestibility, as well as pH and ruminal concentrations of peptides were similar for all treatments. Apparent digestibility of DM, OM and energy, as well as ruminal concentrations of sugars decreased (P<0.01) and, ruminal microbial protein synthesis and ruminal concentrations of ammonia and amino acids varied in a quadratic way (P<0.05) with increased levels of NDF. The effect of NDF in decreasing intake and digestibillity was more evident only at the highest level (43 percent). The inclusion of about 30 percent NDF represents the most adequate level for sorghum silage and concentrate based diets fed to feedlot lambs.