Effect of Replacing Alfalfa Silage with High Moisture Corn on Ruminal Protein Synthesis Estimated from Excretion of Total Purine Derivatives

Abstract

Twenty-four multiparous dairy cows (eight with ruminal cannulae) were blocked by days in milk and assigned to six balanced 4 x 4 Latin squares with 21-d periods. The four diets, formulated from alfalfa silage plus a concentrate mix based on ground high moisture ear corn, contained (dry matter basis): 1) 20% concentrate, 80% alfalfa silage (24% nonfiber carbohydrate; NFC), 2) 35% concentrate, 65% alfalfa silage (30% NFC), 3) 50% concentrate, 50% alfalfa silage (37% NFC), or 4) 65% concentrate, 35% alfalfa silage (43% NFC). Soybean meal and urea were added to make diets isonitrogenous with equal nonprotein nitrogen (NPN) (43% of total N). Total urine was collected with indwelling Folley catheters for 24 h during each period. There was no effect of diet on urinary creatinine excretion (average 29 mg/kg of BW/d). There were quadratic effects of diet on total urinary ecretion of allantoin, uric acid, and purine derivatives (allantoin plus uric acid), and on ruminal synthesis of microbial N estimated from purine derivatives; maxima occurred at about 35% dietary NFC. Urinary excretion also was estimated with spot urine samples from creatinine concentration and the mean daily creatinine excretion. Daily excretion of allantoin, uric acid, and purine derivatives estimated from spot urine sampling followed the same pattern as that observed with total collection; differences between measured and estimated urine volume were significant only for 35% dietary concentrate. Spot urine sampling appeared to yield satisfactory estimates of purine derivative excretion. Maximal urea N excretion was estimated to occur at about 31% dietary NFC. Milk allantoin secretion increased linearly with concentrate and accounted for 4 to 6% of the total purine derivative excretion. Microbial yield was maximal at 35% dietary NFC, suggesting that this was the optimal level for utilization of dietary NPN from alfalfa silage and other sources.

Determining the optimal ratio of canola meal and high protein dried distillers grain protein in diets of high producing Holstein dairy cows

“…In Han et al (1992), Gonzalez-Ronquillo et al (2003) and Moorby et al (2006), lower DM intake, digestibility and milk yield could have been responsible for lower MCP production, and therefore lower AL concentrations, while very high urine volumes diluted AL concentration (mg/L) in Valadares et al (1999). However, when DM intake, milk yield and urine volumes similar to ours were reported (Vagnoni and Broderick, 1997;Reynal and Broderick, 2005), AL concentrations are consistent among studies.…”

“…concluded that the PD to CR ratio in spot urine samples correlates well with intestinal flow of microbial purines and can be used as a qualitative indicator of rumen MCP supply, independent of urine volume, thereby obviating the need for total urine collection. Even though it is accepted that CR is excreted at a constant rate on a BW basis, daily CR excretion is related to body protein mass turnover and therefore varies among cows and studies (19-29 mg/kg BW; Valadares et al, 1999;Moorby et al, 2006). Thus our estimation of differences in MCP yield from the rumen is limited to relative measurements.…”

Uso da creatinina como indicador da excreção urinária em ovinos

“…Este valor é levemente superior aos valores obtidos por YU et al (2001) em ovinos, mas estão entre aqueles normalmente verificados em bovinos (RENNÓ et al, 2000). De fato, em vários outros estudos, a dieta também não influenciou a excreção diária de creatinina por unidade de peso corporal dos animais (SHINGFIELD & OFFER, 1998;VALADARES, et al, 1999;OLIVEIRA et al, 2001;SILVA et al, 2001). No entanto, GONDA et al (1996) e YU et al (2001 observaram efeito da dieta na excreção de creatinina, por unidade de peso corporal, em vacas lactantes e em ovinos, respectivamente.…”

Inclusion of copaiba oil (Copaifera sp.) as additive in supplements for cattle on pasture

“…The daily excretions of urea-N and creatinine-N were obtained by means of the product of urea and creatinine concentrations by urinary volume within 24 hours, multiplied by 0.466 or 0.3715, corresponding to the levels of N in urea and creatinine, respectively. The microbial nitrogen synthesis (Nmic, g N d -1 ) was calculated by means of absorbed purine bases (Pabs, mmol d -1 ), according to the equation described by Chen & Gomes (1992): Nmic = (70*Pabs)/(0.83*0.134*1000); where 70 is the amount of N present in purines (mg N mol -1 ); 0.134 is the N of the Purine: total bacterial N ratio (VALADARES et al, 1999); and 0.83 is the intestinal digestibility of microbial purines. On days 0, 3, 6, 9 and 12, four hours after supplementation, blood samples were collected, totaling five samples, for subsequent serum collection.…”