Meat Production in a Feedlot System of Zebu—Holstein Steers and Heifers with Dairy Genetics: Productive and Biological Analyses

The aim of this study was to evaluate the productive and biological efficiency of steers and heifers from dairy genetics in a feedlot system in terms of meat production. Twenty-four steers and 24 heifers at 10 monthes of age, (3/4) Zebu × (1/4) Holstein were utilized. They were distributed over four feedlot times, 30, 60, 90, and 120 days with four replications for each sex, and were slaughtered at the end of each period. The productive and biological analyses were performed through comparative slaughter to determine the body composition. Heifers presented with greater intakes (P<0.05) of dry matter in grams per kg of body weight. Steers presented with a greater (P<0.05) final empty body weight, carcass gain, cold carcass weight, and meat proportion in the carcass; however, heifers presented with a greater subcutaneous fat thickness (P<0.05) and, consequently, a greater (P<0.05) fat proportion in the carcass. We conclude that steers are more efficient in their productive performance than heifers in a feedlot. For the finishing carcass fat cover, heifers need 90 days in the feedlot. The net energy requirements for maintenance are 67 kcal/EBW0.75/d, and the net requirements of energy (NEg) and protein (NPg) for gain can be estimated by the following equations: NEg(Mcal/d)=0.067×EBW0.75×  EBG1.095 and NPg=162×EBG-5.62×RE for the two sexes

Metabolizable Protein: 1. Predicting Equations to Estimate Microbial Crude Protein Synthesis in Small Ruminants

Microbial crude protein (MCP) produced in rumen could be estimated by a variety of protocols of experimental sampling and analysis. However, a model to estimate this value is necessary when protein requirements are calculated for small ruminants. This model could be useful to calculate rumen degradable protein (RDP) requirements from metabolizable protein (MP). Then, our objective was to investigate if there is a difference in MCP efficiency between sheep and goats, and to fit equations to predict ruminal MCP production from dietary energy intake. The database consisted of 19 studies with goats (n = 176) and sheep (n = 316), and the variables MCP synthesis (g/day), total digestible nutrients (TDN), and organic matter (OM) intakes (g/day), and OM digestibility (g/kg DM) were registered for both species. The database was used for two different purposes, where 70% of the values were sorted to fit equations, and 30% for validation. A meta-analytical procedure was carried out using the MIXED procedure of SAS, specie was considered as the fixed dummy effect, and the intercept and slope nested in the study were considered random effects. No effect of specie was observed for the estimation of MCP from TDN, digestible Organic Matter (dOM), or metabolizable energy (ME) intakes (P &gt; 0.05), considering an equation with or without an intercept. Therefore, single models including both species at the same fitting were validated. The following equations MCP (g/day) = 12.7311 + 59.2956 × TDN intake (AIC = 3,004.6); MCP (g/day) = 15.7764 + 62.2612 × dOM intake (AIC = 2,755.1); and MCP (g/day) = 12.7311 + 15.3000 × ME intake (AIC = 3,007.3) presented lower values for the mean square error of prediction (MSEP) and its decomposition, and similar values for the concordance correlation coefficient (CCC) and for the residual mean square error (RMSE) when compared with equations fitted without an intercept. The intercept and slope pooled test was significant for equations without an intercept (P &lt; 0.05), indicating that observed and predicted data differed. In contrast, predicted and observed data for complete equations were similar (P &gt; 0.05)

Intestinal digestibility of amino acids and use of 15N and purine bases for quantification of microbial protein synthesis in purebred and crossbred zebu cattle fed different dietary crude protein levels

O objetivo desse estudo foi avaliar o efeito dos grupos genéticos e níveis dietéticos de proteína bruta (PB) sobre o consumo, os locais de digestão dos constituintes da dieta, a excreção dos compostos nitrogenados e a absorção de aminoácidos no intestino delgado de bovinos de corte. Objetivou-se também, quantificar a síntese de PB microbiana utilizando 15 N e BP e avaliar a digestibilidade intestinal verdadeira PB total e da PB microbiana em bovinos de corte alimentados com três níveis dietéticos de PB. Oito bovinos, sendo quatro Nelore (com peso corporal (PC) médio inicial de 241,3±43Kg e 14 meses de idade) e quatro cruzados Angus x Nelore (com PC médio inicial 263,4±47 Kg e 14 meses de idade), canulados no rúmen e no íleo, foram distribuídos em dois quadrados latinos 4 x 4 sendo um para cada grupo genético. O experimento foi conduzido em quatro períodos de 17 dias, sendo 10 dias de a*RESUMO:daptação e sete dias de amostragens. As quatro dietas foram constituídas de níveis crescentes de PB: 10; 12 ou 14% oferecidas à vontade, e dieta de consumo restrito com 12% PB. As dietas foram constituídas de 50% de silagem de milho e 50% de concentrado com base na MS. Uma coleta total de fezes e urina de cada animal foi realizada durante três dias consecutivos. Posteriormente, oito coletas de digesta omasal e ileal foram realizadas em intervalos de nove horas durante três dias. Para calcular os fluxos da digesta omasal e ileal, utilizou-se o sistema de indicador duplo (Co-EDTA e FDNi) e único (FDNi), respectivamente. Para quantificar a síntese microbiana, foi realizada uma infusão contínua de 7,03 g de sulfato de amônio enriquecido com 10% de átomos de 15 N no rúmen de cada animal, em todos os períodos experimentais. As quantidades de aminoácidos (AA) absorvidas foram calculadas pela diferença do fluxo dos AA presentes no omaso e no íleo. O consumo de MS (g/Kg de PC) não foi afetado (P > 0,05) pelos grupos genéticos e níveis dietéticos de PB. De maneira geral, as digestibilidades aparentes parciais e totais dos nutrientes não diferiram (P > 0,05) entre grupos genéticos. As digestibilidades aparentes ruminais (%) da MS, MO, EE e CNF não foram afetadas (P > 0,05) pelos níveis dietéticos de PB. Os consumos e as digestibilidade totais da PB aumentaram linearmente (P 0,05). Houve efeito linear negativo (P 0,05) entre 15N e bases purinas (BP) para a eficiência microbiana. A digestibilidade da PB microbiana estimada com BP e 15 N foi próxima ao valor de 80% reportado pelo NRC e BR Corte. A digestibilidade verdadeira da PB total estimada foi de 75,4%. Os resultados indicam que os aumentos dos níveis dietéticos de PB podem potencialmente aumentar as excreções de N pelos bovinos de corte e que as digestibilidades verdadeiras dos aminoácidos são condizentes com o valor adotado pelo NRC e BR Corte. Conclui-se também que, as BP podem ser utilizadas como indicador microbiano alternativo ao 15 N e que a digestibilidade intestinal da PB microbiana no intestino delgado é de aproximadamente 80% em zebuínos.The objective of this study was to evaluate the effect of genetic groups and dietary crude levels (CP) on intake, the site of dietary constituents digestion, nitrogen excretion and absorption of amino acids from the small intestine of beef cattle. Additionally, the objective was to quantify the microbial protein synthesis using 15N and purine bases (BP) and to evaluate the true intestinal digestibility of total protein and microbial protein of beef cattle fed three dietary CP levels. Eight animals, being four Nellore (241 ± 43 kg of initial BW; 14 months) and four crossed Angus x Nellore (263 ± 47 kg of initial BW; 14 months), with ruminal and ileum cannulas were distributed into two 4 x 4 Latin squares, one for each genetic group. Four experimental periods lasting 17 d each were completed with 10 d for adaptation and 7 d for sampling. The diets had increasing levels of CP: 10, 12, or 14%, offered ad libitum, and a 12% CP fed at maintenance level. The diets contained 50% corn silage and 40% concentrate (on a dry matter (DM) basis). Total fecal and urine collection of each animal was performed for three consecutive days. A total of eight digesta samples were collected from the omasum and ileum at 9h intervals over a 3 d period. The double (Co-EDTA and NDFi) and single marker systems (NDFi) were used to calculate the digesta flow of the omasum and ileum, respectively. Continuous infusion of 7.03 g of ammonium sulfate enriched with 10 atom% 15 N was included in the rumen for each animal in all experimental periods. The quantities of absorbed amino acids (AA) were calculated by AA flow difference in the omasum and ileum. The DM intake (g.kg-1) was not affected (P > 0.05) by genetic groups or dietary CP levels. In general, the partial and total apparent digestibility of nutrients did not differ (P > 0.05) between genetic groups. The apparent ruminal digestibility (%) of DM, OM, EE, and NFC were not affected (P > 0.05) by dietary CP levels. The intake and total digestibility of CP increased linearly (P 0.05) between liquid - (LAB) and solid-associated (SAB) bacteria isolated in the omasum. There was a negative linear effect (P 0.05) between 15 N and purine bases (BP) for microbial efficiency. The digestibility of microbial CP estimated by BP and 15N was close to the value of 80% reported by the NRC and BR Corte. The total true digestibility of CP estimated was 75.4%. The results indicate that increasing dietary CP levels may potentially increase N excretion by beef cattle and that the true amino acid digestibility values are consistent with the values adopted by the NRC and BR Corte. Additionally, we conclude that BP can be used as an alternative microbial indicator to 15N and intestinal digestibility of microbial protein from small intestine is about 80% in Zebu cattle.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Performance, enteric methane production and evaluation of places for estimating the digestibility ruminal cattle fed diets based on sugar cane and corn silage performance

O presente trabalho foi desenvolvido a partir de três experimentos descritos em dois capítulos. No capítulo 1, objetivou-se no experimento 1, avaliar o perfil fermentativo de silagens de cana-de-açúcar tratadas ou não com óxido de cálcio e no experimento 2, avaliar o consumo, a digestibilidade aparente total e o desempenho de bovinos alimentados com dietas constituídas de 60% dos seguintes volumosos na base da matéria seca: silagem de milho (SM); cana-de-açúcar in natura (CIN); cana-de-açúcar in natura durante os dois períodos iniciais de alimentação e silagem de milho no período final de alimentação (CIN/SM); silagem de cana-de-açúcar não tratada (SC 0%); silagem de cana-de-açúcar tratada com 0,4% de óxido de cálcio (SC 0,4%) e silagem de cana-de-açúcar tratada com 0,8% de óxido de cálcio (SC 0,8%) na base da matéria natural. No experimento 1, foram confeccionados 15 silos experimentais, 5 por tratamento (SC0%, SC0,4% e SC 0,8%), que foram abertos após 41 dias de fermentação. A recuperação da matéria seca nas silagens de cana-de-açúcar apresentou comportamento quadrático, sendo que o valor máximo de 94,02% foi estimado nas silagens tratadas com 0,81% de óxido de cálcio. A perda por gases apresentou comportamento linear decrescente de acordo com o aumento do nível de óxido de cálcio. A população de leveduras apresentou comportamento quadrático, sendo a menor população de 3,32 ufc/g de forragem fresca estimada no tratamento de 0,39% de óxido de cálcio. No experimento 2, utilizaram-se 30 bovinos mestiços europeu-zebu, com idade entre 24 a 36 meses e peso médio inicial de 343±7,0 kg. O experimento foi realizado em delineamento inteiramente casualizado, com seis tratamentos e cinco repetições. O experimento foi dividido em três períodos de 28 dias. As digestibilidades das dietas foram avaliadas no último período experimental, utilizando-se a fibra em detergente neutro indigestível (FDNi) para estimar a excreção fecal. Os consumos de matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro corrigida para cinzas e proteína (FDNcp) e carboidratos não fibrosos (CNF) foram maiores (P<0,05) para animais alimentados com dietas à base de silagem de milho. Os animais alimentados com dietas de cana-de-açúcar in natura e CIN/SM apresentaram maior (P<0,05) consumo de MS, MO, EE, FDNcp e CNF em relação aos alimentados com dietas de cana-de-açúcar ensilada. As dietas contendo silagem de milho apresentaram menores (P<0,05) coeficientes de digestibilidade para MS, MO e CNF em comparação às dietas com cana-de-açúcar in natura. As digestibilidades da MS, MO, PB, EE, FDNcp e CNF nas silagens de cana-de-açúcar não tratadas e tratadas com 0,8% de óxido de cálcio foram similares. A dieta com silagem de cana tratada com 0,4% de óxido de cálcio apresentou menor digestibilidade da MO e FDNcp em relação às dietas de SC0% e SC0,8%. Os animais alimentados com silagem de milho apresentaram ganho médio diário superior (P<0,05) aos animais dos demais tratamentos. O ganho médio diário dos animais que receberam CIN/SM foi inferior (P<0,05) ao dos animais que receberam a silagem de milho, mas foi superior em 25,8% aos que receberam dieta contendo cana-de-açúcar. As dietas com silagem de cana-de-açúcar proporcionaram menor (P<0,05) ganho médio diário. Conclui-se que as dietas à base de silagem de milho proporcionam maiores desempenhos do que dietas à base de cana-de-açúcar in natura ou ensilada, e que a troca de volumoso no terço final é benéfica, pois aumenta o ganho em 25,8% e assim pode reduzir o tempo para alcançar um mesmo peso final e, que a utilização do óxido de cálcio reduz as perdas de matéria seca, porém os níveis utilizados não foram eficientes para alterar o consumo dos animais. No capítulo 2, objetivou-se avaliar o consumo, as digestibilidades ruminais e intestinais obtidas com amostras de digesta coletadas no retículo e no omaso e as taxas de passagem e de digestão e a produção de metano entérico em bovinos alimentados com dietas contendo silagem de milho (SM) e cana-de-açúcar in natura (CIN) ou ensilada. Foram utilizados cinco bovinos mestiços fistulados no rúmen, com idade entre 24 a 36 meses e peso vivo médio inicial de 336±16,6 kg, distribuídos em quadrado latino 5x5, sendo os cinco tratamentos compostos de dietas com 60% dos seguintes volumosos na base da matéria seca: silagem de milho (SM); cana-de-açúcar in natura (CIN); silagem de cana-de-açúcar não tratada (SC 0%); silagem de cana-de-açúcar tratada com 0,4% de óxido de cálcio (SC 0,4%) e silagem de cana-de-açúcar tratada com 0,8% de óxido de cálcio (SC 0,8%) na base da matéria natural. Para avaliar as digestibilidades, foram realizadas seis coletas de fezes e de digesta reticular e omasal, com intervalos de 12 horas, durante três dias consecutivos, utilizando-se para estimar os fluxos dos constituintes nas digestas de omaso e de retículo, o sistema de dois indicadores (FDNi, para a fase sólida e Co-EDTA para a fase líquida), sendo a produção fecal estimada com a FDNi. Para medir as taxas de digestão foram feitos dois esvaziamentos do rúmen, sendo um 4h após o fornecimento das dietas pela manhã e outro antes do fornecimento das dietas. A produção de metano foi estimada pelo método do hexafluoreto de enxofre, durante cinco dias consecutivos. Os dados foram analisados, utilizando-se o procedimento PROC MIXED do SAS. As maiores produções diárias de metano (P<0,05) foram observadas nas dietas à base de silagem de milho e cana-de-açúcar in natura em relação às dietas contendo silagens de cana-de-açúcar, mas quando expressa por unidade de produto animal, foi menor (P0,05) para estimar as digestibilidades ruminais da MS, MO, PB, FDNcp e CNF. Contudo,a digestibilidade ruminal do EE e as digestibilidades intestinais da PB e do EE diferiram (P<0,05) entre os locais de coleta. A dieta com silagem de milho apresentou a maior (P<0,05) taxa de ingestão da MS e de passagem da MS e da FDNcp e proporcionou maiores consumos aos animais. As taxas de ingestão e passagem da MS e da FDNcp foram similares nas dietas de SC 0% e SC 0,4%. A dieta de SC 0,8% apresentou taxa de ingestão e passagem da MS e FDNcp menor em relação à SC 0,4%. Conclui-se que dietas de melhor qualidade apresentam menores produções de metano por unidade de produto animal e maiores taxas de digestão e de passagem. Além disso, observa-se que a coleta de digesta no omaso apresenta melhor consistência em relação à coleta de digesta reticular.The present work was developed starting from three experiments described in two chapters. In chapter one, the first experiment, aimed on evaluate the fermentative profile of sugarcane silage treated or not with calcium oxide, the experiment two, evaluate intake, the apparent digestibility and the performance of cattle fed on to different diets constituted of 60% on the follow roughage in the dry matter (DM) basis: corn silage (CS); in natura sugar cane (INC); in natura sugar cane for the first two feeding periods and corn silage at the final feeding period (INC/CS); untreated sugar cane silage (CS 0%); 0,4% calcium oxide treated sugarcane silage (CS 0,4%) and 0,8% calcium oxide treated sugar cane silage (CS 0,8%) based on natural matter. At experiment one, were made 15 experimental silos, five per treatment (CS0%, CSO,4% and CS 0,8%), that were opened after 41 days of fermentation. The dry matter recovery on the sugar cane silage presented quadratic comportment, being the maximum value 94,02% estimated at the treated silage with 0,81% calcium oxide. The gas loss presented straight decreasing comportment according with the calcium oxide level raise. The yeast population presented quadratic comportment, being the lower population 3,32 ufc/g of fresh forage estimated at the 0,39% calcium oxide treatment. At experiment 2, was used 30 crossbred cattle Zebu-European, with 24 to 36 months and with average body initial weight 343±7,0 kg. The experiment was accomplished at completely randomized design, with 6 treatments and 5 replications. The experiment was divided in three periods of 28 days. The diets digestibility were evaluated at the final experimental period, using the indigestible neutral detergente fibrer (iNDF) to evaluate the fecal excretion. The DM intake, organic matter (OM), crude protein (CP), ether extract (EE), neutral detergente fiber (NDF) and nonfiber carbohydrates (NFC) were higher (P<0,05) for fed animals with corn silage diets. The animals fed with in natura sugar cane and INC/CS presented higher (P<0,05) DM, OM, EE, NDF and NFC intake than those fed with sugar cane silage. The diets with corn silage presented lower (P<0,05) digestibility coefficients for DM, OM and NFC than the in natura sugar cane diets. The digestibility of the DM, OM, CP, EE, NDF and NFC at the sugar cane silage untreated and treated with 0,8% calcium oxide were the same. The treated sugar cane silage diet with 0,4% calcium oxide presented lower OM and NDF digestibility than the CS0% and CS0,8% diets. The corn silage fed animals presented daily medium weight gain greater (P0,05) to evaluate the ruminal digestibility of the DM, OM, CP, NDF and NFC. However the ruminal digestibility of EE and intestinal digestibility of PB and EE differed (P<0,05) between the collects locations. The corn silage diet presented the greater (P<0,05) ingestion rate of DM, passage rate of DM and NDF and provided greater animal intake. The ingestion and passage rates of DM and NDF were similar on the CS 0% and CS 0,4% diets. The CS 0,8% diet presented ingestion and passage rate of DM and NDF lower than CS 0,4%. Concludes that the better quality diets presented lower methane production per animal product unit and greater digestibility and passage rates. In addition observed that the omasal digesta collect presented better consistency than the reticular digesta.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Intake, digestibility and nitrogen use efficiency in crossbred F1 Holstein × Zebu grazing cows

The objective of this study was to evaluate intake, digestibility and nitrogen (N) compounds use efficiency in F1 Holstein × Zebu grazing cows. Eighteen crossbred cows (six Holstein × Gir, six Holstein × Guzerat, and six Holstein × Nellore) were used in the experiment, constituting three experimental treatments in simple random samples, under the same feeding conditions. At the estimation of individual intake at grazing, titanium dioxide was used for estimating fecal excretion and indigestible neutral detergent fiber, in order to determine pasture intake. There was effect of the lactation period on nutrient intake, except for the intakes of dry matter (DM), organic matter (OM) and total digestible nutrients (TDN) in % of body weight (BW), as well as those of non-fibrous carbohydrates (NFC), in kg. The digestibility coefficients of crude protein (CP), neutral detergent fiber corrected for ash and protein (NDFap) and the contents of TDN varied in function of the lactation period, whereas the coefficients of digestibility of DM, ether extract (EE) and OM did not present such effect. The total milk production projected at 305 days of lactation for Holstein × Gir cows was superior in relation to Holstein × Guzerat and Holstein × Nellore cows. The excretion of urea into urine and of urea N into the milk and the plasma presented quadratic behavior in function of the lactation period. The utilization of the genetic group from Holstein × Zebu grazing cows does not cause alterations in intake, nutrient digestibility or nitrogen use efficiency; however, there is variation in function of the lactation period. Holstein × Gir cows presented greater accumulated production during lactation and persistence, followed by Holstein × Guzerat and Holstein × Nellore cows

Exigências de energia e proteína de bovinos castrados mestiços Holandês x Zebu alimentados com diferentes níveis de cálcio e fósforo na dieta

The aim of this study was to determine the energy and protein requirements of crossbred Holstein x Zebu steers fed with or without the supplementation of dicalcium phosphate in the diet. Thirty-two steers with an average initial body weight of 377.5 ± 49.4 kg were used, of which four were initially slaughtered to estimate the empty body weight (EBW) of the animals. Twenty-four steers were fed ad libitum and were distributed in a completely randomized design with two levels of concentrate (30 and 60 %), and diets with or without dicalcium phosphate and four steers were fed at maintenance level, so that the body weight gain was equal to zero. After 84 days the animals were slaughtered. The animal tissues were sampled, and composted by two samples, denominated by “carcass” (bone, muscle and fat) and “non-carcass” (head, limbs, blood, hide, organs and viscera) for determination of the body composition. The net energy requirements (NEm) and metabolizable energy for maintenance (MEm) were obtained while relating heat production (HP) and metabolizable energy intake (MEI); meanwhile, the net energy requirements for gain (NEg) and the net protein requirements for gain (NPg) were obtained as a function of empty body weight (EBW), empty body gain (EBG) and retained energy (RE) in EBW. The daily net and metabolizable energy requirements for maintenance were 76.90 and 119.36 kcal/EBW0.75, respectively. The net energy requirements for gain can be obtained by the following equation: NEg = 0.0568±0.0025 × EBW0.75 × EBG1.095. The efficiencies of use of metabolizable energy for maintenance and gain are 64.4 and 29.68 %, respectively. The metabolizable protein requirements for maintenance are 4.14 g/BW0.75. The net protein requirements for gain can be obtained through the following equation: NPg = 236.36±30.06 × EBG - 19.84±6.14 × RE. We recommend the use of the equations obtained in this experiment to calculate the energy and protein requirements of crossbred Holstein x Zebu steers.Objetivou-se determinar as exigências nutricionais de energia e proteína para bovinos castrados mestiços Holandês x Zebu alimentados com ou sem suplementação inorgânica de cálcio e fósforo na dieta. Foram utilizados 32 animais mestiços Holandês × Zebu, machos, castrados, com peso corporal (BW) médio inicial de 377,5 ± 49,4 kg, dos quais quatro foram abatidos inicialmente para estimar o peso de corpo vazio (EBW) dos demais, 24 alimentados ad libitum distribuídos em delineamento inteiramente casualizado com dois níveis de concentrado (30 e 60%) e dietas contendo ou não fosfato bicálcico; e quatro alimentados ao nível de mantença, isto é, para que o ganho de peso corporal fosse igual a zero. Após 84 dias os animais foram abatidos. Para determinação da composição corporal dos animais, foram constituídas duas amostras por animal, denominadas “carcaça” (óssos, musculo e gordura) e “não carcaça” (cabeça, membros, sangue, couro, orgãos e visceras). As exigências de energia líquida (NEm) e metabolizável para mantença (MEm) foram obtidas relacionando a produção de calor (HP) e o consumo de energia metabolizável (MEI), enquanto as exigências de energia líquidas para ganho de peso (NEg) e as exigências líquidas de proteína para ganho (NPg) foram obtidas em função do EBW, do ganho de peso de corpo vazio (EBG), e da energia retida (RE) no EBW. As exigências diárias de energia líquida e metabolizável para mantença de bovinos mestiços Holandês × Zebu castrados foram de 76,90 e 119,36 kcal/EBW0,75, respectivamente. As exigências de energia líquida para ganho podem ser obtidas pela equação: NEg = 0,0568±0,0025 × EBW0,75 × EBG1,095. As eficiências de uso da energia metabolizável para mantença e para ganho foram de 64,4 e 29,68%, respectivamente. As exigências de proteína metabolizável para mantença foram de 4,14 g/BW0,75. As exigências líquidas de proteína para ganho de peso podem ser obtidas através da equação NPg = 236,36±30,06 × EBG - 19,84±6,14 × RE. Recomenda-se o uso das equações obtidas nesse experimento para cálculo das exigências nutricionais de energia e proteína para novilhos cruzados Holandês × Zebu castrados

Creatinine as a metabolic marker to estimate urinary volume in growing goats

The objectives of this study were to: (1) quantify the relationship between fasting body weight (FBW, kg) and urinary creatinine excretion (UCE, mg/d) in Boer goats; (2) evaluate the urinary volume estimates obtained from creatinine concentrations in the spot samples collected at different time points; (3) compare them with the 24-h observed urine volume. Thirty growing Boer goats (18 ± 2.2 kg initial BW) were distributed in a complete randomized design. Each collection period fell on 2 consecutive days and collector funnels were used. Spot samples were collected at 0, 4, and 8 h after morning feedings. These procedures were repeated in three runs 25 days apart to obtain different FBWs. All the samples were analyzed to quantify creatinine concentrations. The relationship between UCE and FBW was established by the following equations: UCE = 17.39 x FBW, r^2 = 0.96, P 0.05). Thus both linear and allometric relationships can be used to predict UCE. The spot samples obtained at 4 h after feeding could be used to estimate urinary volume (P < 0.05) instead of at 0 or 8 h. We conclude that UCE can be a metabolic marker to the estimate urinary volume of goats when calculated according to FBW with linear or allometric mathematical relationships

Effect of phase-feeding crude protein on performance and carcass characteristics of crossbred beef bulls: an application to reduce nitrogen compounds in beef cattle diets

Beef cattle (24) with an average initial body weight of 417 ± 54 kg were assigned in a 2 × 2 factorial design with six repetitions. The factors studied were two levels of CP: 11 (low CP) or 13 % (high CP) in the initial feedlot phase (days 1–36) and in the final phase (days 37–72). After 36 days, half of the bulls fed with each level of CP were selected to reverse the CP level. No interaction was observed (P > 0.05) between the level of protein in the initial and final phases on the intake of the nutrients evaluated. There was no effect (P > 0.05) of the protein levels in the initial and final phases on intake of dry matter, organic matter, CP, non-fiber carbohydrates, and total digestible nutrients. No differences were observed among treatments (P > 0.05) for average daily gain (X = 1.99 kg/day) and carcass traits. We conclude that it is possible to feed Holstein-Zebu crossed bulls with an average daily gain of approximately 2 kg using a fixed level of 11 % CP during the entire feedlot period, and this diet is economically viable and environmentally sound

Effect of feeding strategies on weaning weight and milk production of Holstein × Zebu calves in dual purpose milk production systems

The objective of this study was to evaluate the effect of five feeding strategies on calf weaning weight, and cow milk production and composition in Brazilian Holstein × Zebu cows. A total of 60 cows and their calves were allocated to each of five treatments. Cows in treatments 1, 2 and 3 were milked for 270 days and cows in treatments 4 and 5 were milked for 180 days. Calves in treatment 1 (CON) were not supplemented with concentrate whereas calves from treatment 2 (CLPN) received 1 kg of concentrate daily from 90 to 270 days of age and calves from treatment 3 received 1 kg of concentrated from 180 to 270 days of age. Calves in treatment 4 (CCPS) were supplemented with 1 kg of concentrate from 90 to 180 days of age and calves in treatment 5 (CLPS) were supplemented with 1 kg of concentrate from 90 to 270 days of age. Calves from the CLPS treatment had greater milk and protein intakes (P < 0.05) and greater growth rate than calves from the other treatments. Our results indicate that the traditional system of feeding calves with no concentrate results in a weight gain of 600 g/day. The CLPS treatment produced calves with the highest live weight and growth rate. The nutritional strategy with restricted supply of milk for the calves with concomitantly short-term concentrate supplementation does not improve performance of calves but did increase feed costs

Effects of Static or Oscillating Dietary Crude Protein Levels on Fermentation Dynamics of Beef Cattle Diets Using a Dual-Flow Continuous Culture System

<div><p>The objective of this study was to evaluate the effects of increasing dietary crude protein (CP) levels and also comparing the effects of static versus oscillating dietary CP on ruminal nutrient digestibility, ruminal fermentation, nitrogen (N) metabolism, and microbial efficiency in beef cattle diets using a dual-flow continuous culture system. Eight fermenters (1,223 ± 21 mL) were used in a replicated 4 x 4 Latin square design with periods lasting 12 d each (8 d for adaptation and 4 d for sampling). Dietary treatments were: 1) 10% CP, 2) 12% CP, 3) 14% CP, and 4) 10 and 14% CP diets oscillating at 48-h intervals. Experimental diets consisted of 50% orchard hay and 50% concentrate. Fermenters were fed 72 g/d and solid and liquid dilution rates were adjusted to 5.5 and 11%/h, respectively. Data were analyzed using the MIXED procedure in SAS with α = 0.05. Apparent and true ruminal digestibilities of dry matter and organic matter were not affected (P > 0.05) by increasing dietary CP, nor by oscillating dietary CP. Total volatile fatty acids concentration and molar proportions of acetate, propionate, butyrate, valerate, iso-butyrate and iso-valerate were not affected (P > 0.05) by increasing or oscillating dietary CP. Ruminal NH₃-N concentration increased linearly (<i>P</i> < 0.01) in response to increasing dietary CP. Total N, non-ammonia N, and rumen undegraded protein flows did not differ among treatments or between oscillating dietary CP and static 12% CP. Microbial N and NH₃-N flows and microbial efficiency did not differ when comparing oscillating versus static CP (P > 0.05). However, there was a quadratic effect (<i>P</i> < 0.05) for these variables when dietary CP was increased. These results indicate that either ruminal microorganisms do not respond to oscillating CP levels or are capable of coping with 48-h periods of undernourishment.</p></div