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Nine Holstein cows fitted with rumen cannulas and indwelling catheters in splanchnic blood vessels were used to study the effects of supplementing AA on milk lactose secretion, whole-body rate of appearance (WB-Ra) of glucose, and tissue metabolism of glucose, lactate, glycerol, and β-OH-butyrate (BHBA) in postpartum dairy cows according to a generalized randomized incomplete block design with repeated measures in time. At calving, cows were blocked according to parity (second and third or greater) and were allocated to 2 treatments: abomasal infusion of water (n=4) or abomasal infusion of free AA with casein profile (AA-CN; n=5) in addition to the same basal diet. The AA-CN infusion started with half the maximal dose at 1 d in milk (DIM) and then steadily decreased from 791 to 226 g/d from DIM 2 to 29 to cover the estimated essential AA deficit. On DIM 5, 15, and 29, D[6,6-(2)H2]-glucose (23.7 mmol/h) was infused into a jugular vein for 5h, and 6 blood samples were taken from arterial, portal, hepatic, and mammary sources at 45-min intervals, starting 1h after the initiation of the D[6,6-(2)H2]glucose infusion. Trans-organ fluxes were calculated as veno-arterial differences times plasma flow (splanchnic: downstream dilution of deacetylated para-aminohippurate; mammary: Fick principle using Phe+Tyr). Energy-corrected milk and lactose yields increased on average with AA-CN by 6.4 kg/d and 353 g/d, respectively, with no DIM × treatment interaction. Despite increased AA supply and increased demand for lactose secretion with AA-CN, net hepatic release of glucose remained unchanged, but WB-Ra of glucose tended to increase with AA-CN. Portal true flux of glucose increased with AA-CN and represented, on average, 17% of WB-Ra. Splanchnic true flux of glucose was unaltered by treatments and was numerically equivalent to WB-Ra, averaging 729 and 741 mmol/h, respectively. Mammary glucose utilization increased with AA-CN infusion, averaging 78% of WB-Ra, and increased gradually as lactation advanced. Net portal, hepatic, splanchnic, and mammary fluxes of lactate, glycerol, and BHBA were not affected by AA infusion. Increasing the supply of AA in postpartum dairy cows elevated the WB-Ra of glucose without affecting the true liver glucose release. The greater WB-Ra of glucose with abomasal AA infusion seemed to originate mainly from greater true portal-drained viscera release of glucose. Glucose utilization by the portal-drained viscera was unaffected by abomasal AA infusion, but the exact mechanism behind the greater true portal glucose release could not be assessed in the current study. The increased mammary glucose uptake was in line with the increased milk lactose yield. In early postpartum lactation, the demand for AA seems to be so high that even with increased AA supply, cows have metabolic priorities for AA other than hepatic gluconeogenesis., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Nine Holstein cows with rumen cannulas and indwelling catheters in splanchnic blood vessels were used in a generalized randomized incomplete block design with repeated measures to study the effect of increased early postpartum AA supply on splanchnic and mammary AA metabolism. At calving, cows were blocked according to parity (second and third or greater) and allocated to 2 treatments: abomasal infusion of water (CTRL; n=4) or free AA with casein profile (AA-CN; n=5) in addition to a basal diet. The AA-CN infusion started with half of the maximal dose at the calving day (1 d in milk; DIM) and then steadily decreased from 791 to 226 g/d until 29 DIM. On 5, 15, and 29 DIM, 6 sample sets of arterial, portal, hepatic, and mammary blood were taken at 45-min intervals. Over the whole period, increasing AA supply increased milk (+7.8 ± 1.3 kg/d) and milk protein yields (+220 ± 65 g/d) substantially. The increased milk yield was not supported by greater dry matter intake (DMI) as, overall, DMI decreased with AA-CN (-1.6 ± 0.6 kg/d). Arterial concentrations of essential AA were greater for AA-CN compared with CTRL. The net portal-drained viscera (PDV) release of His, Met, and Phe was greater for AA-CN compared with CTRL, and the net PDV recovery of these infused AA ranged from 72 to 102% once changes in DMI were accounted for. The hepatic removal of these AA was increased equivalently to the increased net PDV release, resulting in an unaltered net splanchnic release. The net PDV release of Ile, Leu, Val, and Lys tended to be greater for AA-CN, and the net PDV recovery of these infused AA ranged from 69 to 73%, indicating increased PDV metabolism with AA-CN. The fractional hepatic removal of these AA did not differ from zero and was unaffected by the increased supply. Consequently, the splanchnic release of these AA was approximately equivalent to their net PDV release for both CTRL and AA-CN. Overall, greater early postpartum AA supply increased milk and milk protein yields substantially based on increased mammary AA uptake. The PDV metabolism of branched-chain AA and Lys were increased, whereas it seemed to be unaffected for other essential AA when the intestinal AA supply was increased. On a net basis, the liver removed more group 1 AA (His, Met, Phe, and Trp) for anabolism and catabolism when the early postpartum AA supply was increased. Thus, increasing the postpartum AA supply increased splanchnic and mammary consumption of AA; hence, the protein deficiency persisted., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

A stereotaxic apparatus for access to the lateral brain ventricle of Holstein cows was constructed. This apparatus permits topographic orientation on the head of an anesthetized cow that has been placed in right lateral recumbency. After assessing the XY-plane in parallel to the frontal bone, correct coordinates in reference to the skullcap were adjusted. The lateral brain ventricles were accessed by drilling holes perpendicular to the XY-plane. The subsequent surgical implant of a tailor-made cannula guide enabled the repeatable placement of a catheter. This permanent catheter allowed the frequent withdrawal of cerebrospinal fluid from and injections into cerebral ventricles of nonanesthetized dairy cows. This method is critical for elucidating the role of central hormones, metabolites, and electrolytes in the regulation of diverse physiological processes and for the study of neuropathological disorders in cows., (Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Two dairy cows fitted with rumen cannulas and closed T-shaped duodenal cannulas were utilized to examine duodenal cannula function and indigestible marker performance. Cows were fed one of two mixed diets and hay separately twice daily. Diets contained sources of supplemental protein that differed in expected rate of ruminal degradation. Duodenal DM flow was estimated with the indigestible markers, Cr-mordanted cell wall, Yb-soaked whole crop oat silage, and Co-EDTA. Duodenal DM flow using Co-EDTA was 49% higher than that estimated by reference to Cr-mordanted cell wall; Yb estimated an intermediate flow. Results are interpreted to suggest that the system developed to estimate duodenal digesta flow was not completely successful. However, qualitative assessment indicates that results are substantially better than those previously observed with simple gutter-type T-piece duodenal cannulas. Application of biological tests to the results suggests the failure of the system was not a result of cannula failure per se but due to the method of indigestible marker administration. Cows fed rumen-degraded proteins (slow versus rapid) had higher rumen nonammonia N pools, a trend for higher forestomach fiber fermentation, and a trend for lower forestomach digestion of N. These results are consistent with current knowledge of the influence of slowly degraded proteins on rumen fermentation.

Six steers with rumen cannulas and exteriorized carotid arteries were fed chopped alfalfa, orchardgrass, or tall fescue hay in ambient temperatures (18 and 32 degrees C) using a factorial arrangement of forage and temperature with repeated measurements. Arterial blood, venous blood, and rumen fluid were sampled for VFA at 0, 2, 4, and 7 h after forage was offered. Rate of digestion of plant cell wall was determined by in vitro methods. Rate of ingesta and particulate passage was determined by 144Ce marker. Volatile fatty acid concentrations in blood plasma and rumen fluid were not related to forage voluntary intake. Voluntary forage intake was related to calculated ruminal disappearance of cell wall (r2 of .94). Elevated ambient temperature, 32 degrees C, depressed voluntary forage intake but did not increase ruminal or blood VFA concentrations.

An inexpensive blood sampling system is described that includes a remote alarm triggered by a decrease in rate of blood withdrawal. Additional modifications include design of a reliable sampling catheter and of a method for quickly and atraumatically replacing clogged catheters. This system has been used to collect continuous, integrated blood samples every 15 min for up to 72 h from cows. The alarm system is also useful for monitoring any flow in which minimum rate is critical, e.g., for column chromatography.

A soft rumen cannula for sheep was made with two kinds of silicone rubber and a polyethylene plug. The design of molds is simple and the materials can easily be obtained. The elasticity of the cylindrical part of the cannula controlled leakage of rumen contents to a minimum, and the moderate hardness of the flange prevented loss of contents from the rumen. The cannula could be used repeatedly and functioned well for over 4 yr. The cannula was easily pushed into the rumen, and the collection of whole digesta was accomplished easily by hand. A small amount of sampling with pipette could be achieved through the punched opening without removing the inner polyethylene plug.

Use of a diagnostic ultrasonography unit in the placement of hepatic vein catheters is described. Diagnostic ultrasound proved to be a safe and rapid means of identifying the hepatic venous circulation. It provided a clear visual guide in an otherwise blind surgical procedure and allowed for a precise determination of catheter placement. Thus, the method could be used to advantage in other types of catheterizations. Use of ultrasonography reduced the duration of surgery by 50 to 75%, thereby minimizing the risks associated with long-term general anesthesia and reducing recovery time.

A useful approach of the study of nutrient absorption and metabolism is in vivo measurement of blood flow across portal-drained viscera and liver, and flux of bloodborne metabolites, successful application of the approach requires correct placement of chronic catheters in appropriate blood vessels. Additionally, catheters must stay patent long enough to allow the animal to recover from surgery and to complete an experimental protocol. This paper describes surgical techniques to install chronic catheters in mesenteric veins, the hepatic portal vein, and an hepatic vein of cattle. Techniques for access to arterial blood are described also. Materials, equipment, and supplies required for surgery, blood sampling, and blood flow determination are described. Commercial sources of supplies are suggested. Blood flow is measured by downstream dilution of para-aminohippurate, which is infused into a mesenteric vein. Examples of blood flow data for three types of cattle are provided.

Polyethylene intramammary devices were removed from six infected and four uninfected mammary quarters of seven lactating cows and examined by scanning electron microscopy. Infecting organisms included Corynebacterium bovis, coagulase-negative staphylococci, and an unidentified fungus. Intramammary devices from infected quarters had amorphous material adhering to large areas of the polyethylene. Large numbers of inflammatory cells and microorganisms were found concentrated within the material. Devices from uninfected quarters had less amorphous material with few adhering inflammatory cells. The amorphous material appeared to be restricted to abraded surfaces of the polyethylene. Milk somatic cell counts in stripping milk of quarters infected with Corynebacterium bovis and coagulase-negative staphylococci before and 3 wk after removal of intramammary device averaged 1.2 X 10(6) and .2 X 10(6)/ml, respectively. Results suggest that increased cell counts of infected quarters containing intramammary devices were associated with microbial colonization of the amorphous material.