Ruminal peptide concentration required to optimize microbial growth and efficiency.

Abstract

Experimentation, with a single-phase continuous culture system operated at fractional dilution rates of 0.03 and 0.09 per hour and four cannulated crossbred steers (260 +/- 20 kg) used in a 4 x 4 Latin square design, was conducted to determine the level of ruminally degradable protein (RDP) that maximized microbial efficiency (MOEFF), microbial nitrogen flow, and nutrient digestibility in the rumen. Treatments consisted of increasing diet RDP levels (from 3.5 to 17.5% RDP on a DM basis). The basal diet was corn with casein or soybean meal used as the source of RDP in the continuous culture experiment and animal study, respectively. Dietary nonstructural carbohydrate (NSC) ranged from 52 to 75% on a dry matter basis. Urea was added to ensure an adequate ammonia nitrogen source for microbial growth. The RDP levels did not affect true digestibility of dry matter and organic matter, ruminal pH, particulate passage rate, or liquid passage rate in the animal study. As RDP increased, bacterial nitrogen production increased linearly (P < 0.05) only for the 0.09/h dilution rate. Microbial efficiency was not influenced by RDP level. Ruminal peptide and NH3 N concentration increased linearly (P < 0.05) as RDP increased. Based on this experimentation, 1.8 mM peptide maximized MOEFF when ammonia nitrogen was not limiting (> 2 mg/dL). We concluded from this research that the RDP requirement of NSC-fermenting bacteria was lower than that currently fed in many diets.

Ruminal dynamics of ad libitum feeding in buffalo bulls receiving different level of rumen degradable protein

“…Orskov (1992) reported maximum microbial count when ruminal NH 3 -N level ranged from 10 to 25 mg/dL. Increased bacterial mass with increasing dietary RDP (38 to 58%) has been reported by Fu et al (2001) in crossbred steers. Lowest TBC in bulls fed VHRDP diet might be attributed to inadequate supply of peptide and amino acid for their multiplication as about 100% dietary N of this diet was coming from urea (Russell et al, 1992).…”

Effect of Varying Dietary Rumen Undegraded Protein on Nutrient Intake, Nutrient Digestibility and Production Performance in Early Lactating Crossbred Cows

“…However, Griswold et al (2001) reported decreased DM digestibility in cows fed ration containing increased RUP level. By decreasing dietary RUP concentration, DM and CP digestibility increased in crossbred steers (Fu et al, 2001). The possible reason of such decreased digestibility with increased dietary RUP might be the decreased ruminal ammonia concentration with reduced rumen protein degradation which ultimately leads to decreased microbial activity.…”

Digestibilidade e balanço de nitrogênio de rações com diferentes teores de proteína degradável no rúmen e milho moído como fonte de amido em ovinos

“…Prado et al (2004), no entanto, observaram efeito linear crescente para o CDA da MS, que variou de 66,3 a 69,9% em ovinos alimentados com rações com teores crescentes de PDR e fonte de amido de alta degradabilidade ruminal (farinha de varredura de mandioca). Embora o incremento no teor de PDR das rações possa aumentar a digestibilidade da MS sem que ocorra, necessariamente, aumento na atividade microbiana, é provável que, quando a disponibilidade de PDR é aumentada na presença de uma fonte de amido de alta degradabilidade ruminal, como a farinha de varredura de mandioca, a energia mais rapidamente disponível seja suficiente para propiciar sincronização com o N liberado, ocasionando aumento na digestibilidade da MS. O contrá-rio pode ter ocorrido neste trabalho, no qual a energia pode ter sido limitante, uma vez que o incremento no teor de PDR não foi suficiente para sincronizar com a energia disponibilizada pela fonte de amido (milho) e não alterou a digestibilidade da MS. Fu et al (2001) utilizaram cultura de fluxo contínuo e avaliaram o efeito do incremento do teor de PDR (de 3,5 a 17,5% da MS) sobre a digestibilidade da MS e a síntese microbiana em dietas contendo milho como fonte energética. Estes autores também não observaram efeito dos teores de PDR sobre a digestibilidade da MS e MO e a eficiência de síntese microbiana e concluíram que os microrganismos fermentadores de carboidratos não-estruturais tiveram suas exigências de N atendidas em todos os teores de PDR.…”