Effects of ruminal protein degradability and frequency of supplementation on nitrogen retention, apparent digestibility, and nutrient flux across visceral tissues in lambs fed low-quality forage1

Abstract

Two experiments were conducted to determine the effect of ruminal protein degradability and supplementation frequency on intake, apparent digestibility, N retention, and nutrient flux across visceral tissues of lambs fed a low-quality forage diet. In both experiments, wethers were fed a basal diet of mature crested wheatgrass hay (4.2% CP) for ad libitum consumption plus 1 of 4 supplements: 1) a high RDP supplement provided daily (RDP-D), 2) the high RDP supplement provided on alternate days (RDP-A), 3) a high RUP provided on alternate days (RUP-A), or 4) a 50:50 mixture of the RDP and RUP supplements provided on alternate days. In Exp. 1, 12 lambs (29.9 +/- 2.7 kg initial BW) were used. Forage OM, NDF, and ADF intake were not affected by treatment. Total tract digestibilities (OM, NDF, ADF, and N) were unaffected (P >or= 0.15) by treatment. Neither protein degradability nor supplementation frequency had an effect (P >or= 0.52) on N retention. In Exp. 2, 15 lambs (34 +/- 4 kg initial BW) fitted with indwelling catheters in a hepatic vein, the hepatic portal vein, a mesenteric vein, and a mesenteric artery were used. Release of ammonia N by the portal-drained viscera (PDV) was reduced (P = 0.004) in alternate-day-supplemented lambs compared with RDP-D. Consequently, hepatic uptake of ammonia N was least (P = 0.003) in all alternate-day lambs. Alpha-amino nitrogen (AAN) release by the PDV and hepatic uptake of AAN were not affected by treatment or supplementation frequency. Additionally, hepatic output and PDV uptake of urea N were not affected by treatment. Hepatic N uptake (ammonia N + AAN) accounted for urea synthesized by the liver in all treatments; however, hepatic urea synthesis was approximately 4.5-fold less for RUP-A lambs. This suggests that the provision of AA as RUP may provide a delay in ureagenesis, thus altering the timing of N recycling.

Frequency of concentrate supplementation for grazing beef cattle

“…Those authors observed that even on the days the animals did not receive supplementation, NH 3 levels were above the 8.0 and 10.0 mg/dL of rumen fluid suggested by Detmann et al (2014) and Leng (1990) as optimal values for appropriate fermentation in tropical conditions. A lower frequency of supplementation increases the endogenous synthesis of urea to be recycled and return to the rumen environment to be used by the microorganisms, particularly on days without supplementation (ATKINSON et al, 2010). A lack of effects of lower supplementation frequency has been observed on the body retention of nitrogen compounds (MORAES et al, 2010;RUFINO, 2015), which can also explain the maintenance of the animal performance in relation to the cattle supplemented daily, as found in the current experiment.…”

Avaliação nutricional de estratégias de suplementação para bovinos de corte durante a estação da seca

“…Segundo esses autores, embora aumentos na digestibilidade total do nitrogênio contribuam para aumentar o nitrogênio retido, a maior parte desta resposta decorre da redução na excreção de NUR. Desta forma, a menor frequência de suplementação aumenta a síntese endógena de ureia para ser reciclada e retornar ao ambiente ruminal para ser usada pelos microrganismos, particularmente em dias sem suplementação (Atkinson et al, 2010). Assim, com base nesta afirmativa, se maior quantidade de NS for desviada para essa função produtiva, a excreção de NUR é diminuída.…”

Daily and alternate day supplementation of Moringa oleifera leaf meal or soyabean meal to lambs receiving oat hay

“…According to literature, SBM is higher in rumen degradable crude protein (74.9%, Cozzi et al, 1995) than MLM (48.6%, Makkar and Becker, 1996). Atkinson et al (2010) evaluated the effect of ruminal protein degradability and supplementation frequency on intake, apparent digestibility, N retention, and nutrient flux across visceral tissues of lambs fed a low-quality forage diet. They concluded that the release of ammonia N by the portal-drained viscera (PDV) was reduced in alternate-day-supplemented lambs compared with lambs receiving rumen degradable protein daily.…”