Bariatric surgery affects obesity-related protein requirements.

CONTEXT: Following bariatric surgery, protein deficiency intakes are reported in morbidly obese patients, whereas post-bariatric protein requirements are not specifically defined with validated method in this population. OBJECTIVE: To assess average protein requirement (APR) in obese subjects, before, 3 months and 12 months after bariatric surgery using the validated method of nitrogen balance. DESIGN AND SETTING: Prospective longitudinal study conducted in 21 morbidly obese patients (BMI 43.9 ± 1.4 kg/m2) before (M0), 3 months (M3) and 12 months (M12) after sleeve gastrectomy or Roux-en-Y gastric by-pass. An additional larger cross-sectional study was performed to validate APR before surgery in non-operated matched obese patients (n = 106). APR was evaluated at M0, M3, M12 by measuring 3 days dietary intakes together with losses of nitrogen in urine and stools. MAIN OUTCOME MEASURE: APR was defined as the mean value of protein intake required to achieve balance nitrogen equilibrium. RESULTS: Before surgery, APR in morbidly obese patients was 0.76 [95%CI, 0.66-0.92] g/kg Body Weight (BW)/d in the experimental group, and 0.74 [0.70-0.80] g/kg BW/d in the validation group. APR was 0.62 [0.51-0.75] g/kg/d at M3 and 0.87 [0.75-0.98] g/kg/d at M12, with no difference between surgical procedures. Spontaneous protein intakes were respectively 0.80 ± 0.05, 0.43 ± 0.03 and 0.71 ± 0.04 g/kg BW/d respectively at M0, M3 and M12. CONCLUSION: This study demonstrates a temporal change in protein requirement after bariatric surgery whatever the type of surgery. Spontaneous protein intakes following bariatric surgery does not cover protein requirements for most patients, suggesting that specific dietary protein recommandations have to be adapted in obese patients with bariatric surgery. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT01249326.

Osmolality of a fortified human preterm milk: The effect of fortifier dosage, gestational age, lactation stage, and hospital practices.

OBJECTIVE: The purpose of this study was to evaluate the dose-dependent effect of human milk fortifier (HMF) on the osmolality of various preterm human milks (PHMs) at different gestational and lactation stages, and with different storage and treatment conditions that are routinely used in neonatal intensive care units (NICUs). STUDY DESIGN: Twenty-four mothers who had given birth to their baby before 28 or between 29 and 31 weeks of pregnancy participated in the study after 1-2 weeks or 3-4 weeks breastfeeding after delivery. The study was a prospective, multicenter, comparative, and noninterventional study. Osmolality of fresh or pasteurized human milk stored at 4°C was measured (cryoscopy) at baseline, and 24hours after adding Suppletine® Human Milk fortifier (SHMF) at 3%, 4%, 4.5%, and 5% (w/v). RESULTS: PHM without supplementation had an osmolality (mean±SD) of 301±8 mOsm/kgH2O (n=40; 95% CI: [298; 303]). Adding 3-5% SHMF induced a linear increase of osmolality (P<0.001; r2=0.975). With 4% SHMF, the osmolality measure was 443±13mOsm/kg H2O (95% CI: [439-447]). Neither a 24-hour storage at 4°C nor pasteurization induced a modification of osmolality compared to the fresh samples. CONCLUSION: Whatever the origin and quality of milk as well as hospital practices, adding up to 4% (w/v) SHMF to PHM increases its nutritional quality and osmolality without exceeding 450mOsm/kgH2O, which is generally recognized as safe.

Soluble Milk Proteins Improve Muscle Mass Recovery after Immobilization-Induced Muscle Atrophy in Old Rats but Do not Improve Muscle Functional Property Restoration.

OBJECTIVES: Effect of 3 different dairy protein sources on the recovery of muscle function after limb immobilization in old rats. DESIGN: Longitudinal animal study. SETTING: Institut National de la Recherche Agronomique (INRA). The study took part in a laboratory setting. INTERVENTION: Old rats were subjected to unilateral hindlimb immobilization for 8 days and then allowed to recover with 3 different dietary proteins: casein, soluble milk proteins or whey proteins for 49 days. MEASUREMENTS: Body weight, muscle mass, muscle fibre size, isometric, isokinetic torque, muscle fatigability and muscle oxidative status were measured before and at the end of the immobilization period and during the recovery period i.e 7, 21, 35 and 49 days post immobilization. RESULTS: In contrast to the casein diet, soluble milk proteins and whey proteins were efficient to favor muscle mass recovery after cast immobilization during aging. By contrast, none of the 3 diary proteins was able to improve muscle strength, power and fatigability showing a discrepancy between the recovery of muscle mass and function. However, the soluble milk proteins allowed a better oxidative capacity in skeletal muscle during the rehabilitation period. CONCLUSION: Whey proteins and soluble milk proteins improve muscle mass recovery after immobilization-induced muscle atrophy in old rats but do not allow muscle functional property restoration.

L. fermentum CECT 5716 prevents stress-induced intestinal barrier dysfunction in newborn rats.

BACKGROUND: Intestinal epithelial barrier (IEB) dysfunction plays a critical role in various intestinal disorders affecting infants and children, including the development of food allergies and colitis. Recent studies highlighted the role of probiotics in regulating IEB functions and behavior in adults, but their effects in the newborn remain largely unknown. We therefore characterized in rat pups, the impact of Lactobacillus fermentum CECT 5716 (L. fermentum) on stress-induced IEB dysfunction, systemic immune response and exploratory behavior. METHODS: Newborn rats received daily by gavage either L. fermentum or water. Intestinal permeability to fluorescein sulfonic acid (FSA) and horseradish peroxidase (HRP) was measured following maternal separation (MS) and water avoidance stress (WAS). Immunohistochemical, transcriptomic, and Western blot analysis of zonula occludens-1 (ZO-1) distribution and expression were performed. Anxiety-like and exploratory behavior was assessed using the elevated plus maze test. Cytokine secretion of activated splenocytes was also evaluated. KEY RESULTS: L. fermentum prevented MS and WAS-induced IEB dysfunction in vivo. L. fermentum reduced permeability to both FSA and HRP in the small intestine but not in the colon. L. fermentum increased expression of ZO-1 and prevented WAS-induced ZO-1 disorganization in ileal epithelial cells. L. fermentum also significantly reduced stress-induced increase in plasma corticosteronemia. In activated splenocytes, L. fermentum enhanced IFNγ secretion while it prevented IL-4 secretion. Finally, L. fermentum increased exploratory behavior. CONCLUSIONS & INFERENCES: These results suggest that L. fermentum could provide a novel tool for the prevention and/or treatment of gastrointestinal disorders associated with altered IEB functions in the newborn.

Impact of Lactobacillus fermentum and dairy lipids in the maternal diet on the fatty acid composition of pups' brain and peripheral tissues.

The aim of the study was to determine the effect of maternal diets administered since day 1 of gestation and containing dairy lipids or vegetable oils differing in the supply of n-3 polyunsaturated fatty acids (n-3 PUFAs) (equilibrated or deficient) and of Lactobacillus fermentum (L. fermentum) on the docosahexaenoic acid (DHA) accretion in the pups at postnatal day 14 in the prefrontal cortex (PFC) and hippocampus (HC) for brain structures and in the liver and adipose tissue for peripheral tissues. Maternal milk fatty acid composition was also assessed by analyzing the fatty acid composition of the gastric content of the pups. DHA was higher in mice supplemented with L. fermentum than in mice in the deficient group in HC and PFC and also in liver and adipose tissue. This increase could be linked to the slight but significant increase in C18:3n-3 in the maternal milk. This proportion was comparable in the dairy lipid group for which the brain DHA level was the highest. L. fermentum may have a key role in the protection of the brain during the perinatal period via the neuronal accretion of n-3 PUFAs, especially during n-3 PUFA deficiency.

Enriched dairy fat matrix diet prevents early life lipopolysaccharide-induced spatial memory impairment at adulthood.

Polyunsaturated fatty acids (PUFAs) are essential fatty acids, which are critical for brain development and later life cognitive functions. The main brain PUFAs are docosahexaenoic acid (DHA) for the n-3 family and arachidonic acid (ARA) for the n-6 family, which are provided to the post-natal brain by breast milk or infant formula. Recently, the use of dairy lipids (DL) in replacement of vegetable lipids (VL) was revealed to potently promote the accretion of DHA in the developing brain. Brain DHA, in addition to be a key component of brain development, display potent anti-inflammatory activities, which protect the brain from adverse inflammatory events. In this work, we evaluated the protective effect of partial replacement of VL by DL, supplemented or not with DHA and ARA, on post-natal inflammation and its consequence on memory. Mice were fed with diets poor in vegetal n-3 PUFA (Def VL), balanced in vegetal n-3/n-6 PUFA (Bal VL), balanced in dairy lipids (Bal DL) or enriched in DHA and ARA (Supp VL; Supp DL) from the first day of gestation until adulthood. At post-natal day 14 (PND14), pups received a single administration of the endotoxin lipopolysaccharide (LPS) and brain cytokine expression, microglia phenotype and neurogenesis were measured. In a second set of experiments, memory and neurogenesis were measured at adulthood. Overall, our data showed that lipid quality of the diet modulates early life LPS effect on microglia phenotype, brain cytokine expression and neurogenesis at PND14 and memory at adulthood. In particular, Bal DL diet protects from the adverse effect of early life LPS exposure on PND14 neurogenesis and adult spatial memory.

Dairy fat blend improves brain DHA and neuroplasticity and regulates corticosterone in mice.

Mimicking the breast milk lipid composition appears to be necessary for infant formula to cover the brain's needs in n-3 PUFA. In this study, we evaluated the impact of partial replacement of vegetable oil (VL) in infant formula by dairy fat (DL) on docosahexaenoic acid (DHA) brain level, neuroplasticity and corticosterone in mice. Mice were fed with balanced VL or balanced DL diets enriched or not in DHA and arachidonic acid (ARA) from the first day of gestation. Brain DHA level, microglia number, neurogenesis, corticosterone and glucocorticoid receptor expression were measured in the offsprings. DL diet increased DHA and neuroplasticity in the brain of mice at postnatal day (PND) 14 and at adulthood compared to VL. At PND14, ARA and DHA supplementation increased DHA in VL but not in DL mice brain. Importantly, DHA and ARA supplementation further improved neurogenesis and decreased corticosterone level in DL mice at adulthood. In conclusion, dairy lipids improve brain DHA level and neuroplasticity.

Tolerancia y eficacia de una fórmula extensamente hidrolizada en lactantes con alergia a proteínas de leche de vaca mediada por IgE. Estudio JUNGLO (I): hidrolizado extenso de caseína / Tolerance and efficacy of an extensively hydrolyzed formula for infants with IgE-mediated cow’s milk protein allergy. JUNGLO study (part I): Extensively hydrolyzed casein formula

Objetivos: El principal objetivo de este estudio fue evaluar la tolerancia de un nuevo hidrolizado de caseína y su eficacia durante un periodo de 3 meses en lactantes diagnosticados de alergia a las proteínas de leche de vaca (APLV) mediada por IgE. Métodos: El estudio forma parte de un ensayo clínico multicéntrico, aleatorizado y doble ciego, que se llevó a cabo en 15 hospitales españoles. En este artículo se presentan los resultados del grupo de tratamiento que recibió un hidrolizado extenso de caseína, comportándose como un estudio observacional. Se incluyeron lactantes diagnosticados de APLV una vez que se confirmó con la titulación de IgE específica, con el fin de comprobar la tolerancia a la nueva fórmula en más del 97% de los niños. La principal variable de estudio fue la tolerancia a la fórmula, y se evaluó mediante una prueba de provocación realizada en el hospital. La evolución de los síntomas clínicos y del crecimiento se evaluó durante un periodo de 3 meses tras la inclusión. Resultados: Se incluyeron 25 niños y 22 niñas. Todos toleraron la introducción de la fórmula de estudio sin reacciones adversas en el primer día, lo que significa que más del 97% de los lactantes toleraron el tratamiento en el momento de su introducción (p= 0,0112). Ocurrieron tres acontecimientos adversos, a los 4, 6 y 10 días de la introducción de la fórmula, que se consideraron posible o probablemente relacionados con la misma, por lo que la tolerancia efectiva fue del 93%. Al cabo de 1 mes de seguimiento, la situación clínica de los lactantes había mejorado, con una disminución del 40,4 al 13% para los síntomas digestivos, y la desaparición total de todos los demás síntomas. El patrón de crecimiento, levemente disminuido al inicio, se normalizó o al menos mejoró a los 3 meses de tratamiento. Conclusiones: El nuevo hidrolizado de caseína se toleró en más del 97% de los lactantes, y mejora los síntomas clínicos de forma rápida en lactantes con APLV mediada por IgE, al tiempo que se mantiene un crecimiento normal (AU)

Objectives: The main objective of this study was to evaluate the tolerance of a new casein hydrolyzate formula, and its efficacy during a 3 months consumption period by infants with IgE-mediated cow’s milk protein allergy (CMPA). Methods: This study was part of randomized, double blind study performed in 15 Spanish hospitals. In the present paper the results of the arm that received an extensively hydrolyzed casein formula are reported. Full term infants aged up to 9 months were included to check that 97% of them tolerate the formula at introduction. The CMPA was confirmed by a specific IgE dosage before inclusion. An oral food challenge was made with the formula. Over 3 months, the evolution of the clinical symptoms and the growth were evaluated. Results: The 25 boys and 22 girls included tolerated the formula at introduction without any adverse reaction during the first day of formula intake, meaning that 97% of the infants tolerated the treatment at introduction (p= 0.0112). Three adverse events were reported 4, 6 and 10 days later and were considered possibly or probably related to the study formula indicating an effective delayed tolerance of more than 93% of infants. At 1 month of follow-up, the condition of the infants was greatly improved as indicated by the dramatic decrease of the digestive symptoms from 40.4% to 13%, and the total regression of all the other symptoms. The growth of the infants over 3 months showed a normal pattern, in agreement with the World Health Organization (WHO) growth references. Conclusion: This new casein hydrolyzate formula shows a rate of tolerance >97%, it is efficient to rapidly improve clinical symptoms and allows a normal growth pattern in infants with CMPA (AU)

A dairy fat matrix providing alpha-linolenic acid (ALA) is better than a vegetable fat mixture to increase brain DHA accretion in young rats.

Achieving an appropriate DHA status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how alpha-linolenic acid (ALA), provided for six weeks after weaning by different dietary fat matrix, improved brain DHA content of young male rats born from deficient-dams. The level of ALA achieved was based on the fat composition of usual infant vegetable formula. A palm oil-blend diet thus providing 1.5%ALA was compared to dairy fat-blend-based diets that provided either 1.5%ALA or 2.3%ALA, or a rapeseed oil diet providing 8.3%ALA (n-6/n-3 ratio were, respectively 10,10,5,2.5). The 1.5%ALA-dairy-fat-blend was superior to 1.5%ALA-palm-oil-blend to restore values of brain DHA, while the 2.3%ALA-dairy-fat-blend exhibited a further increase and reached the values obtained with pure rapeseed diet (8.3%ALA). Dairy-fat-blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of post-weaning rats. Providing dairy fat as well as a reduction of the LA/ALA ratio should be reconsidered to design infant formula.

A tryptophan-rich protein diet efficiently restores sleep after food deprivation in the rat.

Sleep depends on the quantity and quality of the diet. Several studies have shown that food deprivation results in a reduction in sleep duration. It has also been demonstrated that in the newborn, the supply of certain essential amino acids improves sleep through their action on the synthesis of specific neurotransmitters. The aim of the present study was to test if the quantity and/or quality of dietary protein could improve the recovery of sleep during re-feeding after caloric deprivation. Sleep parameters were compared in rats fed ad libitum, food restricted during 4 days, or reefed isocalorically after food restriction with three dietary regimens varying in terms of the amount (14% versus 30%) or quality (milk protein or alpha-lactalbumin) of protein. The results showed that sleep recovery, in particular slow-wave sleep, was improved in rats re-fed with alpha-lactalbumin. This result confirms the close relationship between feeding and sleep and suggest that alpha-lactabumin could be used to improve sleep in adult submitted to nutritional disturbances such as food restriction, shift work, Ramadan.

Controlled ruminal infusion of sodium bicarbonate. 3. Influence of infusion dose on systemic acid-base status, minerals, and ruminal milieu.

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 x 4 Latin square to monitor effects of intraruminal NaHCO3 infusion on temporal changes in ruminal and systemic acid-base status and mineral metabolism. Twice daily from 2 to 4 h postfeeding, cows were infused with 0, 110, 220, or 330 g of NaHCO3 dissolved in 3.8 L of water. All cows had access to their TMR of sorghum silage and concentrate (35: 65, DM basis) for 2 h twice daily. Ruminal fluid, blood, and urine were collected at feeding and every 30 min postfeeding for 12 h on the last day of each 14-d period. Total urine volume also was measured during this interval. Infusion of buffer increased ruminal fluid buffering capacity transiently at 4.5 h postfeeding but otherwise did not markedly affect ruminal fluid acid-base status. Systemic acid-base status was unaffected by the buffer primarily because renal excretion of base successfully reduced systemic base load. Urine volume increased in response to NaHCO3 infusion. Buffer infusion increased urinary excretion of Na, Mg, and K but decreased Ca excretion for 12 h postfeeding; Cl excretion was not affected. Buffer infusion tended to increase total VFA in ruminal fluid. Our data indicate that homeostatic mechanisms can eliminate exogenous base via the kidneys; hence, acid-base status was not perturbed by infusion of NaHCO3. The increased excretion of Mg and K with buffer infusion indicates that the dietary requirements for these minerals may be increased by NaHCO3. Although loss of Ca through the urine was reduced by buffer infusion, this reduction may indicate reduced availability of Ca to the cow. The diuresis accompanying large doses of NaHCO3 may increase dietary requirements for some minerals.

Evaluation of a system for rating edema in dairy cattle.

Our objective was to evaluate a subjective edema rating system to quantitate edema severity. Edema was evaluated with 20 nulliparous Holstein heifers from 3 wk before their expected calving date until 3 wk postpartum. Severity of udder edema was evaluated independently daily by five people throughout the 68-d experiment; a 10-point rating system (0 = no edema, 10 = severe edema) was used. One of the people developing the scoring system served as the official scorer. The accuracy of the rating system, defined as the closeness of test evaluator scores to official scores, was highest for scores 2 to 8. The precision of the system, identified by the standard error of the mean, was similar for each score in the rating system. The largest disagreement between official and test evaluator scores was evident postpartum. The large number of defined points in this rating system and the similarity between official and test scores in this study indicate the usefulness of this tool to evaluate precisely the severity of edema in dairy cattle.

Influence of calcium chloride fed prepartum on severity of edema and lactational performance of dairy heifers.

Twenty Holstein heifers in a completely randomized design were used to evaluate the effects of prepartum dietary CaCl2 on the development and regression of edema and on subsequent lactational performance. Heifers were assigned to diets containing either 2.17% limestone or 1.5% CaCl2 (DM basis) at 3 wk before expected calving date. Except for the Ca sources, diets were identical. Test diets were only fed prepartum; at calving, all heifers were offered a lactation diet for 3 wk. Severity of edema was evaluated independently by five people daily throughout the experiment; a 10-point rating system was utilized to quantify the severity of edema. Calcium chloride reduced the severity of edema, although this response was most evident during the 1st wk that this salt was fed. The beneficial effects of CaCl2 on edema prepartum disappeared postpartum, when CaCl2 was removed from the diet. Indeed, edema was higher for heifers fed CaCl2 than for those fed limestone at 2 wk postpartum. Calcium chloride reduced DMI prepartum, but, following parturition, a compensatory increase in feed intake occurred. Postpartum daily DMI averaged 1.3 kg higher for heifers fed CaCl2 than for those fed the limestone diet prepartum. Milk yield and composition were somewhat lower for heifers fed CaCl2, although this response was most evident at 1 wk postpartum. Feeding CaCl2 prepartum to prevent milk fever also may reduce the severity of udder edema prepartum and increase feed intake during early lactation.

Influence of dietary fiber and buffer value index on the ruminal milieu of lactating dairy cows.

The influence of dietary buffer value index and dietary ADF content on ruminal fluid pH, buffering capacity, and buffer value index was measured. Four lactating Holstein cows (two primiparous) averaging 72 +/- 60 DIM were used in a 4 x 4 Latin square with 3-wk experimental periods. Treatments were a 2 x 2 factorial arrangement of TMR containing two ADF concentrations (16 and 21% of DM) and two buffer value indexes (calculated from analysis of individual dietary ingredients to be -200 and 0). Milk fat content and milk fat yield tended to be increased by high ADF, and protein yield tended to increase with low buffer value index and low ADF. Although the high ADF diets increased ruminal fluid pH, they reduced buffering capacity; because the magnitude of the pH increase was greater than the reduction in buffering capacity, ruminal fluid buffer value index was increased by added ADF. The high buffer value index diets reduced ruminal fluid pH and increased ruminal fluid buffering capacity; effects on pH outweighed those on buffering capacity so that the ruminal fluid index paradoxically decreased as the dietary index increased. Ruminal fluid acetate increased and propionate decreased as ADF increased. We conclude that ruminal fluid buffer value index increases with dietary ADF, likely because of reduced ruminal concentrations of fermentation acids. Because diets with the highest index produced the lowest ruminal indexes, dietary buffer value index must be studied further before it can be included in any model purporting to predict the need for supplemental dietary buffers.

Sodium bicarbonate or multielement buffer via diet or rumen: effects on performance and acid-base status of lactating cows.

Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.

Ruminal buffers: temporal effects on buffering capacity and pH of ruminal fluid from cows fed a high concentrate diet.

In vitro characteristics of several buffers and alkalinizing agents commonly utilized to reduce ruminal acid load were evaluated. Ruminal fluid was collected from five cows consuming a diet containing concentrate and sorghum silage in a 68:32 ratio (DM basis). This fluid was incubated with either NaHCO3, a natural sodium sesquicarbonate, a multielement buffer or MgO (7.1 g/L of ruminal fluid), or no buffer for 48 h; flasks were removed and analyzed for pH, buffering capacity, and buffer value index every 12 h during the 48-h incubation. The buffer value index accounts simultaneously for alterations in pH and buffering capacity. Compared with the unbuffered control, all buffering compounds increased ruminal fluid buffer value index. However, the buffer value index separated these buffering compounds into two categories. The NaH-CO3 and sodium sesquicarbonate exhibited similar buffer value indexes; both were markedly higher than those for the multielement buffer and MgO. Although NaHCO3 and sodium sesquicarbonate each increased both ruminal fluid pH and buffering capacity sharply, the multielement buffer only increased pH and buffering capacity moderately. The increase in buffer value index for MgO primarily was due to an increase in pH. Both NaHCO3 and sodium sesquicarbonate were fully active within the first 12 h of incubation; activity of multielement buffer and MgO reached a plateau at 24 h. Compared with the multielement buffer and MgO, NaHCO3 and sodium sesquicarbonate should be more beneficial in preventing short-term postprandial increases in ruminal fluid hydrogen ion concentration; because of their slower release rates, the multielement buffer and MgO should help stabilize ruminal acid-base status, but efficacy might be reduced because of passage out of the rumen.

A buffer value index to evaluate effects of buffers on ruminal milieu in cows fed high or low concentrate, silage, or hay diets.

Our objective was to develop a buffer value index that would incorporate alterations in both ruminal fluid pH and buffering capacity as indicators of the influence of dietary buffering and alkalinizing agents on ruminal acid-base status. This index was evaluated using ruminal fluid from four lactating Holstein cows fed either sorghum silage or alfalfa hay in high or low concentrate diets. Ruminal fluid was incubated in vitro for 1, 2, 3, 4, or 5 h with no buffer or with 7.1 g of either NaHCO3, sodium sesquicarbonate, or a multielement buffer added per liter of ruminal fluid. Ruminal fluid pH was lower for diets based on high concentrate or alfalfa; buffering capacity between pH 5 and 7 was greater for high concentrate diets but was not affected by forage type. Ruminal fluid pH was higher for sesquicarbonate than for NaHCO3, the multielement buffer, or the control; however, ruminal fluid H+ concentration was similar between sesquicarbonate and NaHCO3, and both were lower than for the multielement buffer. Hydrogen ion concentration for the multielement buffer was lower than for the control. Buffering capacity was highest for NaHCO3, followed by sesquicarbonate, the multielement buffer, and the control. The buffer value index, which accounted for alterations in both H+ concentration and buffering capacity, was highest for NaCHO3, followed by sesquicarbonate, the multielement buffer, and the control. The poor response to the multielement buffer may be attributable to our relatively short incubation interval (less than 5 h). Dietary buffers increase both ruminal fluid pH and buffering capacity; both of these responses are beneficial.(ABSTRACT TRUNCATED AT 250 WORDS)

Homoacetogenic Fermentation of Cellulose by a Coculture of Clostridium thermocellum and Acetogenium kivui.

Interrelationships between methanogens and fermentative or hydrolytic bacteria are well documented; however, such cocultures do not allow a complete fermentation shift to a peculiar metabolite. We describe here a new stable association between Clostridium thermocellum and Acetogenium kivui which converts 1 mol of cellulose (anhydroglucose equivalent) into 2.7 mol of acetate.