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Knowledge of the profile of amino acids of the rumen-undegradable protein can help in the formulation of diets to provide amino acids that complement microbial protein as well as supply amino acids, which are most limiting for milk production. Three non-lactating cows fitted with rumen cannulas were used to determine the effect ofin siturumen degradation on crude protein and amino acid profile of rumen-undegraded protein of feedstuffs. The obtained values of rumen degradability of crude protein with significant difference (P< 0.001) between feeds ranged from 20.3 to 76.3% (mean 62.0 ± 17.9%) and values of total amino acids ranged from 30.9% in corn gluten meal to 83.8% in corn gluten feed (mean 67.5 ± 16.4%). Anin vitromodified 3-step method was used to determine intestinal digestibility. Intestinal digestibility of undegraded protein varied from 54.5 ± 1.4% in raw soybean to 95.2 ± 1.0% in corn gluten feed. The absorbable amino acid profile of rumen-undegraded protein for each feedstuff was compared with profiles of the original feedstuff and the rumen-exposed undegraded protein. Absorbable lysine (9.3 ± 1.1 g/kg of crude protein) was higher in products of soybean and sunflower cake. Corn gluten feed and meal supplied more absorbable methionine (3.6 ± 0.6 g/kg of crude protein). This study showed that the digestibility factor of crude protein and amino acid based onin situandin vitromethods for thermal treatment of protein feeds can be used in models to optimize the amino acid nutrition of dairy cows and expand knowledge about rumen degradability and ileal digestibility of amino acids in feedstuffs.

The aim of this study was to investigate the relationship between concentration of non-esterified fatty acid and ketone bodies in blood of dairy cows, and to evaluate these concentrations for the detection of prevalence of subclinical ketosis. The second aim was to compare the concentration of β-hydroxybutyric acid determined by an electronic handheld meter Precision Xtra® with serum concentration of β-hydroxybutyric acid analysed in laboratory with izotachometric and photometric method, respectively. Blood samples were collected from jugular vein 4–6 h after morning feeding in three groups of Holstein cows (n = 909) according to the lactation phase from 51 different herds with similar husbandry characteristics. High lipomobilization (non-esterified fatty acid ≥ 0.35 mmol·l-1, mean concentration 0.34 ± 0.15 mmol·l-1) was detected in 30.3% of antepartum cows, while increased concentrations of β-hydroxybutyric acid (≥ 1.0 mmol·l-1, prevalence of subclinical ketosis) were detected in 18.5% and 14.1% of the early lactation and mid lactation cows, respectively. The correlation coefficient (r = 0.84, P < 0.001; r = 0.93, P < 0.001) was found between measurements of whole blood β-hydroxybutyric acid of 60 and 38 dairy cows determined with the Precision Xtra® test and plasma or serum β-hydroxybutyric acid concentration determined by isotachophoresis and photometrical method, respectively. Our results show that the monitoring of changes in the blood concentration of β-hydroxybutyric acid in high-yielding cows in the early postpartum period by the electronic handheld meter Precision Xtra® may be effective in reducing the incidence of ketosis and health problems associated with ketosis in dairy cattle herds.