No abstract

The effects of acidogenic conditions, a high S level and the addition of thiamin on the rumen microbial metabolism of thiamin were investigated in vitro in a semi-continuous fermenter (RUSITEC), using a factorial design. Acidogenic conditions were obtained by simultaneously increasing the starch : cellulose ratio and the amount of solid substrate fed, and by decreasing the buffering capacity of the liquid phase of the fermenter. S in the form of sulfate was supplied at two levels, one corresponding to a control amount of S (2 g/kg dietary DM), the second to an excess (5 g/ kg DM) which is sufficient to trigger cerebrocortical necrosis (CCN) when used in vivo. Acidogenic conditions decreased the pH of the fermenters, CH4 production and cellulose digestibility, increased the short-chain fatty acid production, but had no effect on thiamin production. The high S level enhanced the production of sulfide considerably, had no effect on the microbial metabolism of energy and N, and decreased thiamin production (326 Y. 266nmoYd). The added thiamin was rapidly converted into phosphorylated compounds which largely decreased the apparent synthesis of this vitamin by the rumen microflora. The total thiamin flow was increased by added thiamin. In no case was thiaminase activity in the fermenter liquid phase significantly modified. The high level of S induced only a limited decrease of total thiamin flow. Consequently, it is unlikely that the investigated factors could be considered to be high risk factors for the thiamin-dependent CCN.

In sheep, warfarin, chlorophacinone, and bromadiolone were not degraded in the rumen but their bioavailabilities were high after oral administration; the kinetics of these compounds in sheep and other mammals are quite similar. These data suggest that the lack of susceptibility of ruminants to these anticoagulant rodenticides cannot be explained by either ruminal degradation or the specific toxicokinetics of these anticoagulants.

A semi-synthetic thiamine-free diet was used on weaned lambs to test the effect of a high sulfur level on the rumen, microbial activity and on the microbial production of thiamine. In vivo and in vitro kinetic studies, as well as the determination of the thiamine concentrations and thiaminase activity in the rumen, were performed during the 16 week experiment. A high sulfur level (0.6%) in the diet, in comparison with a normal sulfur level (0.2%), did not modify the microbial activity of the rumen with the exception of a slightly retarded decrease in the volatile fatty acid (VFA) rumen concentration. The rumen thiamine level and the thiaminase activity were not modified by the dietary sulfur level. In contrast, the rate of sulfate reduction into sulfide in the rumen increased progressively with the 0.6% sulfur diet. In conclusion, a high sulfur level (0.6%) in the diet of sheep did not modify the thiamine status of the rumen. It strongly increased the production of sulfides but an adaptation period of several weeks was required by the rumen microflora to reduce sulfate at a maximal rate. rumen / sulfur / thiamine / synthetic diet Résumé ― Effet d'un régime excédentaire en soufre sur l'activité microbienne du rumen et sur le métabolisme ruminal de la thiamine chez le mouton recevant un régime semi-synthétique dépourvu de thiamine. Un régime semi-synthétique dépourvu de thiamine a été utilisé chez l'agneau * Correspondence and reprints minasique. En conclusion un régime à 0, 6 % de soufre chez le mouton n'a pas d'effet sur la concentration ruminale de thiamine d'origine microbienne. Il provoque une très forte augmentation de la production de sulfures mais celle-ci n'est maximale qu'après une période d'adaptation de la micropopulation du rumen.

Abstract. In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of this study was to develop and validate, under physiologic and pathologic conditions, a radioimmunoassay (RIA) for bovine TSH (bTSH). Double RIA was performed with purified bTSH and specific bovine antiserum. Laboratory validation included research of minimal detection limit, accuracy, and reproducibility. The physiologic validation included a thyrotropin-releasing hormone (TRH) challenge performed on euthyroid cows and a follow-up of bTSH concentration over a 24-hour period. Furthermore, bTSH concentration was assayed in a large population of healthy dairy and beef cows to define reference interval. The pathologic validation was made by assaying bTSH and thyroid hormones on healthy and goitrous newborn calves. The minimum detection limit (MDL) for bTSH assay was 1.3 mU/ml. The recovery was 101% to 106%. The intra-and interassay coefficients of variation (CVs) ranged from 5% to 11% and 11% to 15%, respectively. The RIA covered the whole range of physiologic bTSH values, as shown by bTSH values induced by TRH-challenge. A pulsatile secretion of bTSH was observed, accompanied by a diurnal variation with lower night values than day values. Reference intervals of bTSH ranged from 1.3 to 13.0 mU/ml for beef and dairy breeds. Finally, bTSH easily discriminated goitrous newborn calves from healthy ones, leading to the definition of a cutoff value of 35 mU/ml. The bTSH assay positively reacted to physiologic and pathologic conditions. The accuracy and precision of the RIA were satisfying.

Polioencephalomalacia (P.E.M.) in ruminants is often associated with high concentrate diets and rumen acidosis; this syndrome is classically related to a disturbance of the rumen metabolism of thiamin. An in vitro model using a semicontinuous system (RUSITEC) was used to investigate the effect of pH on microbial metabolism and on production of thiamin in the rumen. These effects were tested using either a natural diet (hay/wheat) or a semi-synthetic one. Lowering the pH decreased total volatile fatty acids, methane and microbial nitrogen production. Molar proportions of VFA were modified by an increase in butyric, valeric and caproic acids. Microbial production of thiamin was comparable to in vivo synthesis but decreased when the diet was enriched with thiamin. The diet of the donors of inoculum had no effect on this metabolism. For all diets, lowering of pH did not reduce microbial production of thiamin. Thiaminase activity in the liquid phase of fermentors was very low and was not modified by pH. Thus lowering of pH in vitro, had no deleterious effect on microbial production of thiamin. Therefore, lowering of the rumen pH in acidotic conditions may not be a factor which promotes P.E.M.

A traditional process used by farmers in Chad consists in soaking slices of taro (Colocasia esculenta L. SCHOTT) in tamarind infusion, or in corn solution or in water over a 24-hour period to reduce the acridity of taro and facilitate cooking. The aim of this study was to assess the effect of traditional soaking on the in vitro digestibility of taro flour using or not using an α-amylase enzyme. The digestion without the enzyme has shown that the soaking processes improve the digestibility of taro flour (from 39.30% for the control sample to 75.11% (after tamarind infusion) and 78.67% (treatment with water) after 24 hours of soaking). Soaking over a 6-hour period and preferentially in tamarind infusion or in corn solution obtains highly digestible flour (around 95% of digestibility rate after 3 hours of enzymatic digestion).

Increased understanding of the biology of the transition period should decrease health problems and increase profitability of dairy cows » Drackley, 1999Transition dairy cows (-21d to +21d relative to calving, Drackley, 1999): a major challenge for controlling the animal's health and optimizing its zootechnical performance. The objective is to study the effect of the use of live yeasts distributed peri-partum on milk performance at the beginning of lactation and on the prevention of subclinical ketosis.RESULTS AND DISCUSSION § The cows calved on average on 01/21/2016 with a mean lactation rank of 2.11 with no difference between the Control and Live Yeast groups (P > 0.9). § Averaged milk yield during the first 3 months of lactation (Figure 1) is numerically higher for Live Yeast group (34.6 ± 7.8 kg/d) than for Control group (32.6 ± 10.2 kg/d).§ The technological quality of the milk (fat and protein contents) is not affected by the treatment during the first 3 months of lactation, which eliminates any dilution effect of milk by dietary addition of live yeast. § The BHB content of the blood at +22 days was significantly lower (P = 0.024) for the cows in Live Yeast group: 0.79 mmol/L vs. 1.41 mmol/L (Figure 2). § Blood glucose content is not affected by treatment at +8 and +22 postpartum days: 46.9 mg/100 mL, on average. § The RFS and BCS were significantly higher (P < 0.01) for cows of Live Yeast group than cows of Control group 8 days postpartum: respectively 2.81 vs. 2.10 and 2.94 vs. 2.42 (Figure 3). § First artificial insemination (AI1) for cows in the Control and Live Yeast groups were at 120 days of lactation on average, whatever the group was (P > 0.9).Peripartum supplementation with live yeast tends to improve reproductive performance, particularly the success rate at IA1 (Table 1). CONCLUSIONSq Dietary supplementation with a high dose of live yeast for transition cows induces a numerical increase in milk production at the beginning of lactation without any dilution.q High dosage of live yeast in peri-parturient dairy cows goes beyond the nutritional impact. The circulating BHB content is reduced and BCS is increased implying less lipomobilization in the first weeks of lactation, conferring prevention from subclinical ketosis and better fertility.