Effects of feeding canola meal or wheat dried distillers grains with solubles as a major protein source in low- or high-crude protein diets on ruminal fermentation, omasal flow, and production in cows.

The objective of this study was to determine the effects of feeding canola meal (CM) or wheat dried distillers grains with solubles (W-DDGS) as the major source of protein in diets varying in crude protein (CP) content on ruminal fermentation, microbial protein production, omasal nutrient flow, and production performance in lactating dairy cows. Eight lactating dairy cows were used in a replicated 4×4 Latin square design with 29-d periods (21 d of dietary adaptation and 8 d of measurements) and a 2×2 factorial arrangement of dietary treatments. Four cows in 1 Latin square were ruminally cannulated to allow ruminal and omasal sampling. The treatment factors were (1) source of supplemental protein (CM vs. W-DDGS) and (2) dietary CP content (15 vs. 17%; DM basis). Diets contained 50% forage and 50% concentrate, and were fed twice daily at 0900 and 1600 h as total mixed rations for ad libitum intake. Dry matter intake and milk yield were unaffected by dietary treatments; however, milk yield in cows that were fed CM was numerically greater (+1.1 kg/d) when compared with cows fed W-DDGS. Feeding CM increased milk lactose content compared with feeding W-DDGS. Milk urea nitrogen and ruminal NH3-N concentrations were greater in cows fed the high-CP compared with those fed the low-CP diet. The rumen-degradable protein supply was greater in cows fed the high-CP when compared with those fed the low-CP diet when diets contained CM, whereas rumen-degradable protein supply was lower in cows fed the high-CP when compared with those fed the low-CP diet when diets contained W-DDGS. Total N flow at the omasal canal was not affected by diet; however, omasal flow of NH3-N was greater in cows fed CM when compared with those fed W-DDGS. The rumen-undegradable protein supply was greater in cows fed the low-CP when compared with those fed the high-CP diet when diets contained CM, whereas rumen-undegradable protein supply was lower in cows fed the low-CP when compared with those fed the high-CP diet when diets contained W-DDGS. Omasal flow of fluid-associated bacteria was greater and that of particle-associated bacteria tended to be greater in cows fed CM when compared with those fed W-DDGS; however, omasal flow of total microbial nonammonia N was unaffected by dietary treatment. Omasal flows of threonine and tryptophan were greater, whereas that of histidine and lysine tended to be greater in cows fed CM when compared with those fed W-DDGS. Our results show that when dairy diets are formulated to contain 15 or 17% CP, CM or W-DDGS can be used as the major source of protein and achieve similar levels of milk production.

Blood concentrations of D- and L-lactate in healthy rabbits.

OBJECTIVES: To determine whole blood and serum concentrations of l-lactate and serum concentrations of d-lactate in healthy rabbits and compare three methods of analysis for l-lactate measurement. METHODS: Prospective study using 25 rabbits. Concentrations of whole blood l-lactate were measured using a portable analyser and a blood gas analyser. The remainder of the sample was allowed to clot for centrifugation. Serum was stored at -20°C for determination of l- and d- lactate by high-performance liquid chromatography. RESULTS: d-lactate values by high-performance liquid chromatography were 0 · 17 ± 0 · 08 mmol/L. l-lactate values were 5 · 1 (±2 · 1) mmol/L by high-performance liquid chromatography, 6 · 9 (±2 · 7) mmol/L with the portable analyser and 7 · 1 (±1 · 6) mmol/L with the blood gas analyser. No significant difference (P > 0 · 05) was found between the two analysers. Significant difference existed between serum l-lactate values obtained by high-performance liquid chromatography and the whole blood values obtained with the blood gas analyser (P < 0 · 01) and portable analyser (P < 0 · 05). CLINICAL SIGNIFICANCE: Serum concentrations of d-lactate in healthy rabbits are in the range of those of other mammals. l-lactate values in healthy rabbits are higher compared with other mammals. Good correlation was found between the portable and blood gas analysers for whole blood l-lactate measurement in healthy rabbits.

Serum D-lactate concentrations in cats with gastrointestinal disease.

BACKGROUND: Increased D-lactate concentrations cause neurological signs in humans with gastrointestinal disease. HYPOTHESIS/OBJECTIVES: To determine if serum D-lactate concentrations are increased in cats with gastrointestinal disease compared to healthy controls, and if concentrations correlate with specific neurological or gastrointestinal abnormalities. ANIMALS: Systematically selected serum samples submitted to the Gastrointestinal Laboratory at Texas A&M University from 100 cats with clinical signs of gastrointestinal disease and abnormal gastrointestinal function tests, and 30 healthy cats. METHODS: Case-control study in which serum D- and L-lactate concentrations and retrospective data on clinical signs were compared between 30 healthy cats and 100 cats with gastrointestinal disease. Association of D-lactate concentration with tests of GI dysfunction and neurological signs was evaluated by multivariate linear and logistic regression analyses, respectively. RESULTS: All 100 cats had a history of abnormal gastrointestinal signs and abnormal gastrointestinal function test results. Thirty-one cats had definitive or subjective neurological abnormalities. D-lactate concentrations of cats with gastrointestinal disease (median 0.36, range 0.04-8.33 mmol/L) were significantly higher than those in healthy controls (median 0.22, range 0.04-0.87 mmol/L; P = .022). L-lactate concentrations were not significantly different between the 2 groups of cats with gastrointestinal disease and healthy controls. D-lactate concentrations were not significantly associated with fPLI, fTLI, cobalamin, folate, or neurological abnormalities (P > .05). CONCLUSIONS AND CLINICAL IMPORTANCE: D-lactate concentrations can be increased in cats with gastrointestinal disease. These findings warrant additional investigations into the role of intestinal microbiota derangements in cats with gastrointestinal disease, and the association of D-lactate and neurological abnormalities.