Embrapa/CPPSE -São Carlos, SP, Pesquisador do CNPq.RESUMO -O gás metano possui reconhecidamente um importante papel como intensificador do efeito estufa. Pelo seu processo digestivo de fermentação entérica, os ruminantes convertem os carboidratos presentes na dieta em ácidos graxos voláteis, resultando na produção de dióxido de carbono e metano. Dessa forma, os ruminantes são reconhecidos como importantes emissores de metano ruminal para a atmosfera, sendo que a produção deste gás representa ainda perdas energéticas para os animais em relação à energia consumida. Animais consumindo dietas de baixa qualidade podem produzir mais metano por unidade de produto (carne ou leite) em relação aos animais de alta produção consumindo dietas de melhor qualidade em maiores níveis de ingestão. Resultados têm mostrado que a redução da emissão de metano pela pecuária está ligada à melhoria da dieta, à melhoria dos pastos, à suplementação alimentar, à seleção por maior potencial genético de produção e a outras medidas que reflitam na melhor eficiência produtiva, resultando em menores ciclos de produção. Palavras-chave:Fermentação ruminal, metano, produção animal, efeito estufa, ruminantes.ABSTRACT -Methane is well known as a greenhouse effect intensifier. Ruminants, during the ruminal digestive fermentation process, transform carbohydrates available in the diet to volatile fatty acids, with production of carbon dioxide and methane. Therefore, ruminants are known as important methane source to the atmosphere. Methane production also means animal losses of ingested energy. Ruminal fermentation process is driven by dry matter intake, and feed quality. Therefore, consume of low quality diets will produce more methane per product unit (milk or beef) compared to high producing animals ingesting great amounts of high quality diets. The sulphur hex fluoride gas tracer technique did allow good methane emission measurements by grazing or free managed animals. Results show that the reduction of methane emission by cattle is related to better quality diet, to improvement of forage quality of pastures, to grain inclusion in diet, to animal breeds with greater production potential, and other practices that improve production efficiency, and result in shorter production cycles. Key-words:Animal production, greenhouse effect, methane, ruminal fermentation, ruminants. IntroduçãoA interação entre os fatores de produção animal e o impacto ambiental causado pelas diversas atividades tem sido, cada vez mais, o objetivo de pesquisas relacionadas com as mudanças climáticas mundiais. Os ruminantes, devido ao processo digestivo de fermentação entérica, são reconhecidos como importante fonte de emissão de metano (CH 4 ) para a atmosfera. Além disso, a produção desse gás, que pode variar em função do sistema de alimentação, é considerada uma parte perdida da energia do alimento, refletindo em ineficiência na produção animal. Baseado em aspectos de proteção mercadológica, o Brasil, por ser detentor do maior rebanho comercial de bovinos do mundo e por utili...
This trial aimed to evaluate the fat color and myoglobin concentration of three cattle breeds, supplemented in two nutritional plans (NP) during the growing phase and finished in the intensive system on pasture or conventional feedlot. One hundred and nineteen bulls from three genetic groups: Nellore (N), ½ Angus x ½ Nellore (A) and ½ Senepol x ½ Nellore (S), were randomly assigned in two NP on growing phase: mineral (M) or concentrate (C, energy protein 0.3% BW). Following the growing phase, two replicates within each treatment were randomly assigned to one of two finishing systems: pasture (P, n = 59) and conventional feedlot (CF, n = 60). Bulls were supplemented daily with 2% BW of concentrate (16% CP and 78% TDN) and slaughtered at a commercial abattoir. Steaks from longissimus muscle (LM) between 12th and 13th ribs each animal were collected for analysis of concentration myoglobin (MYO) and subcutaneous fat were removed for color analysis (parameters: L*, a*, b*, C* and h*). The data were analyzed by ANOVA using PROC MIXED procedures in SAS 9.4, with a 3×2×2 factorial arrangement. The muscle of Nellore showed greater (P = 0.006) concentration of MYO compared to Angus, however, Senepol had values similar to Nellore and Angus (4.43, 4.03 and 4.25, Nellore, Angus, and Senepol, respectively), and the muscle of animal finished on CF had lower concentration of MYO compared to pasture (P < 0.0001; 4.55 and 3.93, P and CF). The subcutaneous fat of animals finished on pasture showed high (P < 0.05) of L*, a*, b* and C* compared to CF. Therefore, the meat quality parameters were more affected by finished systems, the meat of animals from pasture had the lighter fat and amount of yellow pigmentation, and also presented meat with greater level of myoglobin.
The objective of this experiment was to evaluate the influence of beef cattle breed, nutritional treatment, and finishing strategy (pasture vs. feedlot) on the relative abundance of mRNA associated with lipid metabolism in longissimus muscle (LM). Eighty-three uncastrated males from three genetic groups: Nellore (N), ½ Angus x ½ Nellore (A) and ½ Senepol x ½ Nellore (S), were randomly assigned to dietary treatments supplied during the growing phase. Treatments consisted of mineral supplement or concentrate supplement (0.3% BW). Following the growing phase, two replicates within each treatment x breed group were randomly assigned to one of two finishing systems (Figure 1): Pasture grazing + concentrate (PC) and Conventional feedlot (CF), both are supplemented at 2% BW/had/d (Table 1). After 209 days the animals were slaughtered, an LM sample (5.0g) was removed between 12th and 13th ribs from each animal and frozen (liquid nitrogen). The relative abundance of mRNA associated with lipid metabolism was measured by qRT-PCR. Target genes include PPARα, PPARγ, SREBP1c, SCD1, LPL, FBP4, CPT2, ACOX and ACCα. The ∆∆ Ct was used to calculate the data and analyzed using the mixed procedures of SAS for a 3×2×2 factorial arrangement of treatments. Mineral supplementation during the growing phase increased (P < 0.05) the relative abundance of mRNA of PPARα and PPARγ compared to concentrate. The relative abundance of PPARγ, SREBP1c, SCD1, FABP4, ACOX, was greater (P < 0.05) in CF compared to PC. Angus LM muscle showed greater (P < 0.05) relative abundance of SREPB1c compared to Nellore and Senepol. The muscle of Nellore and Angus had greater (P < 0.05) relative abundance of PPARα SCD1 and lower (P < 0.05) of PPARγ when compared to Senepol breed. Therefore, in this study, the conventional feedlot and Angus are more positively associated with differential expression of adipogenic genes.
The goal of this study was to evaluate the effects of different levels (10 and 13% crude protein) and protein source on ruminal fermentation of feedlot Nellore steers fed high-concentrate diets. The protein sources tested were urea, dried distillers grains (DDG) and corn gluten meal. The DDG and gluten were used as RUP sources. We used 6 cannulated Nellore steers, rumen, duodenum, and ileum arranged in 6×6 Latin square designed in factorial (2 nitrogen levels and 3 protein sources) balanced for residues. The pH was measured immediately after rumen fluid sampling at 0, 2, 4, 6, 8 and 10h after feeding. The NH3-N concentrations were determined with micro-Kjeldahl apparatus. The concentration of volatile fatty acids (VFA) was assessed by gas chromatography. Data were evaluated using the MIXED procedure of SAS, with repeated measures over time. There was no interaction between sampling time and treatments for NH3-N and pH (P > 0.05). Animals fed diets containing Urea had a higher concentration of NH3-N (20.6 mg/dL) than animals supplemented with Gluten (16.2 mg/dL) or DDG (12.7 mg / dL). There was an increase in the NH3-N concentration (P = 0.049) with the increase of the protein level 10 to 13% CP with 14.7 and 18.3 mg/dL, respectively. The ruminal pH was affected by the dietary protein level (P = 0.016), in which animals fed a level of 10% CP had a higher pH (6.80) compared to the level of 13% CP (6.43). Total and individual VFA concentration was not affected by protein levels and sources (P > 0.05). The reduction of N level and the use of RUP did not adversely affect the ruminal fermentation. Although significant differences were observed for pH, they were small and adequate for microbial protein synthesis in the rumen.
Nitrogen use efficiency (NUE) has implications for production performance, economic efficiency and for the emission of contaminants to the environment. Thus, the objective of this study was to evaluate whether high-concentrate diets with different levels (10 and 13% crude protein) and protein source can affect the NUE and nitrogen (N) excretion. The protein sources tested were urea, dried distillers grains (DDG) and corn gluten meal. Our hypothesis is that reducing the level of N in the diet associated with the use of rumen undegradable protein (RUP) could increase the NUE in high-concentrate diets. The hypotheses were tested using 6 cannulated Nellore steers, rumen, duodenum and ileum arranged in 6×6 Latin square designed in factorial (2 nitrogen levels and 3 protein sources) balanced for residues. The concentration of N in samples was analyzed using the Dumas combustion method. The statistical analysis was performed using the MIXED procedure of the statistical package SAS. The N intake and retention was not affected by level and protein source (P > 0.05). Fecal N excretion was not affected by the levels and protein sources tested (P > 0.05). However, there was effect of protein source (P < 0.001) and tendency to protein level in the diet (P < 0.10) on urinary N excretion. In the treatments containing the urea source, there was an increase in the urinary N excretion (46.8 g.dia-1) compared to the Gluten and DDG sources with 28.8 and 27.0 g of N excreted in the urine per day, respectively. The NUE was affected by the protein source (P < 0.05). Diets containing urea had lower NUE (31.8%) compared to corn gluten meal and DDG sources with NUE of 40.3 and 41.2%, respectively. Using RUP (DDG or Gluten) in high-concentrate diets can be a nutritional strategy for increase NUE and this response is partly attributable to decreased urinary N excretion.
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