Effects of Polyurethane Coated Urea Supplement on In vitro Ruminal Fermentation, Ammonia Release Dynamics and Lactating Performance of Holstein Dairy Cows Fed a Steam-flaked Corn-based Diet

Abstract

Three experiments were conducted to investigate the effects of polyurethane coated urea on in vitro ruminal fermentation, ammonia release dynamics and lactating performance of Holstein dairy cows fed a steam-flaked corn-based diet. In Exp. 1, a dual-flow continuous culture was run to investigate the effect of polyurethane coated urea on nutrient digestibility, rumen fermentation parameters and microbial efficiency. Three treatment diets with isonitrogenous contents (13.0% CP) were prepared: i) feedgrade urea (FGU) diet; ii) polyurethane coated urea (PCU) diet; and iii) isolated soy protein (ISP) diet. Each of the diets consisted of 40% steam-flaked corn meal, 58.5% forages and 1.5% different sources of nitrogen. PCU and FGU diets had significantly lower digestibility of NDF and ADF (p<0.01) than the ISP diet. Nitrogen source had no significant effect (p = 0.62) on CP digestibility. The microbial efficiency (expressed as grams of microbial N/kg organic matter truly digested (OMTD)) in vitro of the PCU diet (13.0 g N/kg OMTD) was significantly higher than the FGU diet (11.3 g N/kg OMTD), but comparable with the ISP diet (14.7 g N/kg OMTD). Exp. 2, an in vitro ruminal fermentation experiment, was conducted to determine the ammonia release dynamics during an 8 h ruminal fermentation. Three treatment diets were based on steam-flaked corn diets commonly fed to lactating cows in China, in which FGU, PCU or soybean meal (SBM) was added to provide 10% of total dietary N. In vitro NH 3 -N concentrations were lower (p<0.05) for the PCU diet than the FGU diet, but similar to that for the SBM diet at all time points. In Exp. 3, a lactation trial was performed using 24 lactating Holstein cows to compare the lactating performance and blood urea nitrogen (BUN) concentrations when cows were fed PCU, FGU and SBM diets. Cows consuming the PCU diet had approximately 12.8% more (p = 0.02) dietary dry matter intake than those consuming the FGU diet. Cows fed the PCU diet had higher milk protein content (3.16% vs. 2.94%) and lower milk urea nitrogen (MUN) concentration (13.0 mg/dl vs. 14.4 mg/dl) than those fed the FGU diet. Blood urea nitrogen (BUN) concentration was significantly lower for cows fed the PCU (16.7 mg/dl) and SBM (16.4 mg/dl) diets than the FGU (18.7 mg/dl) diet. Cows fed the PCU diet had less surplus ruminal N than those fed the FGU diet and produced a comparable lactation performance to the SBM diet, suggesting that polyurethane coated urea can partially substitute soybean meal in the dairy cow diet without impairing lactation performance.

Slow-release urea in supplement fed to beef steers

“…Blood urea nitrogen concentration was lower for lactating dairy cows fed SRU and soybean meal than RU. Probably, more urea was produced in the liver and then excreted in urine for the cows consuming RU (Xin et al 2010). Digestibility coefficients for DM and its fraction along with TDN of diets are presented in Table 4.…”

Utilização de ureia encapsulada de liberação lenta na alimentação de vacas em lactação

“…Não foram encontradas diferenças no pH, na produção total e proporção molar dos ácidos graxos voláteis. (HUNTINGTON et al, 2006;GOLOMESKI et al, 2006;TAYLOR-EDWARDS et al, 2009;HIGHSTREET et al, 2010;INOSTROZA et al, 2010;PINOS-RODRÍGUEZ et al, 2010;XIN et al, 2010). No entanto, as concentrações de N-NH 3 nos tratamento com ureia de liberação lenta e com proteína isolada de soja continuou declinando.…”

“…Portanto, a sincronização entre a liberação de N-NH 3 ruminal e disponibilidade de energia pode ter sido melhorado, conseqüentemente resultando em maior síntese de proteína microbiana. Xin et al (2010) avaliaram os efeitos da ureia em liberação lenta na concentração de ácidos graxos voláteis em vacas leiteiras alimentados com dietas a base de milho floculado. Foram utilizadas três dietas experimentais isoprotéicas (13,0% PB): i) ureia convencional (0.6% na MS); ii) ureia de liberação lenta (revestida com poliuretano) (0,6% MS); e iii) proteína de soja isolada.…”

“…Guidi (1999) Como os AGCCs são obtidos principalmente a partir da fermentação de carboidratos provenientes da dieta (FIRKINS et al, 2007), as suas concentrações refletem se está ou não ocorrendo interferência das ureias, tanto convencional como de liberação lenta, na fermentação ruminal (XIN et al, 2010). Como seus valores foram alterados podemos concluir que a inclusão das ureias (U, UE1 e UE2) interferiu de forma negativa (menor produção total de ácidos graxos de cadeia curta), quando comparada a dieta sem inclusão de ureia na fermentação ruminal.…”

Substituição do farelo de soja por fontes de nitrogênio não-protéico em bovinos Nelore

“…A utilização de uréia de liberação lenta in vivo apresenta uma taxa mais lenta de liberação de nitrogênio amoniacal do que a uréia e pode efetivamente modular as concentrações de nitrogênio amoniacal quando substituído por uréia (Huntington et al, 2006;Golomeski et al, 2006;Taylor-Edwards et al, 2009;Cherdthong et al, 2010;Highstreet et al, 2010;Inostroza et al, 2010;Pinos-Rodríguez et al, 2010;Xin et al, 2010).…”