Biomedical subjects

R A Patton

Publications and source records attributed to R A Patton.

14 recordsLinked to original sources

PubMed2006

Effect of ruminally protected methionine on splanchnic metabolism of amino acids in lactating dairy cows.

The effect of ruminally protected Met (RPM) on splanchnic metabolism was measured in 3 primiparous and 3 multiparous Holstein cows. Doses of RPM (0, 36, and 72 g/d) were tested in a replicated 3 x 3 Latin square design, over 3 consecutive 14-d experimental periods. A mixed ration was fed in 12 equal meals per d (average dry matter intake: 17.5 +/- 0.08 kg/d). Indwelling catheters were surgically implanted in the mesenteric artery and the portal and hepatic veins for blood collection, as well as in 2 distal branches of the mesenteric vein for infusion of p-aminohippurate to determine blood flow. On d 14 of each period, a temporary catheter was inserted into a mammary vein and 6 hourly blood samples were collected to determine plasma concentrations of metabolites, hormones, and their respective fluxes across the splanchnic bed and mammary glands. Yields of milk (32.8, 32.0, and 32.9 +/- 0.92 kg/d) and protein (1,028, 1,053, and 1,075 +/- 28.7 g/d) were unaffected by level of RPM. However, the true protein content in milk from primiparous cows increased linearly (2.92, 3.09, and 3.34 +/- 0.077%). The addition of RPM linearly increased the net flux of Met across the portal-drained viscera, which resulted in increased arterial Met concentrations (25, 29, and 40 +/- 1.1 microM). Although it had no significant effect on net portal and hepatic fluxes of other essential amino acids, RPM resulted in a linear increase in the total splanchnic output of Ile, Leu, Phe, and Thr. These results suggest that feeding RPM triggered a homeostatic response resulting in less utilization of certain essential amino acids through the gastrointestinal tract and liver. Net mammary uptake of Met did not change with the addition of RPM. However, mammary extraction of Met decreased in a linear fashion in response to increased arterial inflow.

Amino Acids↗

PubMed2001

Accuracy and precision of computer models to predict passage of crude protein and amino acids to the duodenum of lactating cows.

To evaluate the ability of several models to accurately and precisely predict the passage of crude protein (CP) and amino acids to the duodenum of lactating cows, we simulated data from six published studies using the 1989 National Research Council equations, the Mepron Dairy Ration Evaluator (version 1.1), the University of Pennsylvania release of the Net Carbohydrate and Protein System (version 2.12p), the Cornell Net Carbohydrate and Protein System (version 3), and CPM Dairy (version 1.0). Models overestimated the passage of CP from microbes by an average of 323 g/d, and underestimated the passage of CP from feed by an average of 874 g/d. These two errors were partially canceled when CP from microbes and feed were summed to estimate passage of total CP to the duodenum. Many dietary composition variables appeared to bias the predictions; however, the influence of any one variable was small. The efficiency of modeling was high for most predictions but was variable for predicting passage of specific individual amino acids to the small intestine depending on the model selected. These simulations indicated no obvious advantage for any model over the others tested. The models responded to changes in diets by altering the amount of protein from microbes and feed that reached the duodenum, resulting in improved accuracy of predictions of duodenal CP passage compared with simply assuming a constant value for passage of CP to the duodenum.

Amino Acids↗

PubMed2001

Prediction of crude protein and amino acid passage to the duodenum of lactating cows by models compared with in vivo data.

To determine whether statistical inferences obtained from predictions by models were similar to those of measured data from individual cows, data from six research trials published between 1989 and 1997 were simulated using the 1989 National Research Council Model, the Mepron Dairy Ration Evaluator (version 1.1), The University of Pennsylvania release of the Net Carbohydrate and Protein System (version 2.12p), The Cornell Net Carbohydrate and Protein System (version 3), and the CPM Dairy (version 1.0). Both predicted and measured protein fractions were analyzed by ANOVA and compared to determine whether statistical inferences among treatments from predictions by the models were similar to those from the measured data. The interpretations and statistical inferences of measured data did not always agree with those for predicted data. All models responded to changes in diet composition and often predicted that dietary changes would result in statistically different amounts of protein and amino acids passing to the duodenum than were observed in the measured data. The direction of predicted change among treatments for passage of nitrogen fractions to the duodenum also did not agree with the measured data a large percentage of the time. Discrepancies in ANOVA and interpretations between predicted and measured data may be due to the reduction in variation associated with modeling biological systems, associative effects of feeds not accounted for by models, inadequate equations in the models, inadequate description of feeds, or experimental error in measured data. Before model simulations of duodenal flow of crude protein and amino acids can be substituted for experimental measurements, better descriptors of main dietary effects, microbial protein production, ruminal protein degradation, and interactions among dietary factors must be developed.

Amino Acids↗

PubMed1976