Subacute ruminal acidosis reduces sperm quality in beef bulls

Breeding bulls are commonly fed high-energy diets, which may induce subacute ruminal acidosis (SARA). In this experiment, 8 Santa Gertrudis bulls (age 20 ± 6 mo) were used to evaluate the extent and duration of effects of SARA on semen quality and the associated changes in circulating hormones and metabolites. The bulls were relocated and fed in yards with unrestricted access to hay and daily individual concentrate feeding for 125 d before SARA challenge. Semen was collected and assessed at 14-d intervals before the challenge to ensure acclimatization and the attainment of a stable spermiogram. The challenge treatments consisted of either a single oral dose of oligofructose (OFF; 6.5 g/kg BW) or an equivalent sham dose of water (Control). Locomotion, behavior, respiratory rate, and cardiovascular and gastrointestinal function were intensively monitored during the 24-h challenge period. Rumen fluid samples were retained for VFA, ammonia, and lactate analysis. After the challenge, semen was then collected every third day for a period of 7 wk and then once weekly until 12 wk, with associated blood collection for FSH, testosterone, inhibin, and cortisol assay. Percent normal sperm decreased in bulls dosed with OFF after the challenge period (P < 0.05) and continued to remain lower on completion of the study at 88 d after challenge. There was a corresponding increase in sperm defects commencing from 16 d after challenge. These included proximal cytoplasmic droplets (P < 0.001), distal reflex midpieces (P = 0.01), and vacuole and teratoid heads (P < 0.001). Changes in semen quality after challenge were associated with lower serum testosterone (P < 0.001) and FSH (P < 0.05). Serum cortisol in OFF bulls tended to be greater (P = 0.07) at 7 d after challenge. This study shows that SARA challenge causes a reduction in sperm quality sufficient to preclude bulls from sale as single sire breeding animals 3 mo after the event occurred

A mechanistic model of small intestinal starch digestion and glucose uptake in the cow

The high contribution of postruminal starch digestion (up to 50%) to total-tract starch digestion on energy-dense, starch-rich diets demands that limitations to small intestinal starch digestion be identified. A mechanistic model of the small intestine was described and evaluated with regard to its ability to simulate observations from abomasal carbohydrate infusions in the dairy cow. The 7 state variables represent starch, oligosaccharide, glucose, and pancreatic amylase in the intestinal lumen, oligosaccharide and glucose in the unstirred water layer at the intestinal wall, and intracellular glucose of the enterocyte. Enzymatic hydrolysis of starch was modeled as a 2-stage process involving the activity of pancreatic amylase in the lumen and of oligosaccharidase at the brush border of the enterocyte confined within the unstirred water layer. The Na+-dependent glucose transport into the enterocyte was represented along with a facilitative glucose transporter 2 transport system on the basolateral membrane. The small intestine is subdivided into 3 main sections, representing the duodenum, jejunum, and ileum for parameterization. Further subsections are defined between which continual digesta flow is represented. The model predicted nonstructural carbohydrate disappearance in the small intestine for cattle unadapted to duodenal infusion with a coefficient of determination of 0.92 and a root mean square prediction error of 25.4%. Simulation of glucose disappearance for mature Holstein heifers adapted to various levels of duodenal glucose infusion yielded a coefficient of determination of 0.81 and a root mean square prediction error of 38.6%. Analysis of model behavior identified limitations to the efficiency of small intestinal starch digestion with high levels of duodenal starch flow. Limitations to individual processes, particularly starch digestion in the proximal section of the intestine, can create asynchrony between starch hydrolysis and glucose uptake capacity

EPR and X-ray Crystallographic Characterization of the Product-Bound Form of the Mn\u3csup\u3eII\u3c/sup\u3e-Loaded Methionyl Aminopeptidase from \u3cem\u3ePyrococcus furiosus\u3c/em\u3e

Methionine aminopeptidases (MetAPs) are ubiquitous metallohydrolases that remove the N-terminal methionine from nascent polypeptide chains. Although various crystal structures of MetAP in the presence of inhibitors have been solved, the structural aspects of the product-bound step has received little attention. Both perpendicular- and parallel-mode electron paramagnetic resonance (EPR) spectra were recorded for the MnII-loaded forms of the type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs in the presence of the reaction product l-methionine (l-Met). In general, similar EPR features were observed for both [MnMn(EcMetAP-I)]−l-Met and [MnMn(PfMetAP-II)]−l-Met. The observed perpendicular-mode EPR spectra consisted of a six-line hyperfine pattern at g = 2.03 (A = 8.8 mT) with less intense signals with eleven-line splitting at g = 2.4 and 1.7 (A = 4.4 mT). The former feature results from mononuclear, magnetically isolated MnII ions and this signal are 3-fold more intense in the [MnMn(PfMetAP-II)]−l-Met EPR spectrum than in the [MnMn(EcMetAP-I)]−l-Met spectrum. Inspection of the EPR spectra of both [MnMn(EcMetAP-I)]−l-Met and [MnMn(PfMetAP-II)]−l-Met at 40 K in the parallel mode reveals that the [Mn(EcMetAP-I)]−l-Met spectrum exhibits a well-resolved hyperfine split pattern at g = 7.6 with a hyperfine splitting constant of A = 4.4 mT. These data suggest the presence of a magnetically coupled dinuclear MnII center. On the other hand, a similar feature was not observed for the [MnMn(PfMetAP-II)]−l-Met complex. Therefore, the EPR data suggest that l-Met binds to [MnMn(EcMetAP-I)] differently than [MnMn(PfMetAP-II)]. To confirm these data, the X-ray crystal structure of [MnMn(PfMetAP-II)]−l-Met was solved to 2.3 Å resolution. Both Mn1 and Mn2 reside in a distorted trigonal bipyramidal geometry, but the bridging water molecule, observed in the [CoCo(PfMetAP-II)] structure, is absent. Therefore, l-Met binding displaces this water molecule, but the carboxylate oxygen atom of l-Met does not bridge between the two MnII ions. Instead, a single carboxylate oxygen atom of l-Met interacts with only Mn1, while the N-terminal amine nitrogen atom binds to M2. This l-Met binding mode is different from that observed for l-Met binding [CoCo(EcMetAP-I)]. Therefore, the catalytic mechanisms of type-I MetAPs may differ somewhat from type-II enzymes when a dinuclear metalloactive site is present

Evaluating the Effects of Rumenocentesis on Health and Performance in Dairy Cows

The objective of this study was to evaluate the effects of the rumenocentesis procedure on dairy cows by determining selected metabolic and physiological variables representing the health status. Two groups of 6 cows either underwent rumenocentesis (GA) or sham (GB) procedures. Superficial skin temperature of the rumenocentesis area was measured using infrared thermography before the procedure (-1 h), immediately after (0 h), and at 48 h, 96 h, and 20 days following rumenocentesis. Blood samples were collected at all times, except for immediately after the procedure (0 h), and selected immunologic response variables were determined. Milk yield and rectal temperatures were measured daily. Rumenocentesis did not influence the white blood cell count, haptoglobin or total protein concentrations. Electrophoretic protein fractions were not different between GA and GB treatments. Milk yield and rectal temperature were not affected by rumenocentesis. Skin temperature of the rumenocentesis region in GA group cows increased by 1.0 °C immediately after rumenocentesis and returned to baseline after 48 h where it remained constantly until the end of the study; similar to observation in GB group cows. Results of this study would suggest minimal adverse effects on cow health and production when performing rumenocentesis for the diagnosis of subacute ruminal acidosis. Additional more intensive studies addressing animal welfare issues relative to the diagnostic techniques are needed

Chemical composition and nutrient degradability in elephant grass silage inoculated with Streptococcus bovis isolated from the rumen

The objective of the present study was to assess the chemical and bromatological composition and in situ degradability of elephant grass silages inoculated with Streptococcus bovis isolated from cattle rumen. A complete randomized design was used with four treatments and six replications: elephant grass silage, elephant grass silage inoculated with 106 CFU/g Streptococcus bovis JB1 strains; elephant grass silage inoculated with 106 CFU/g Streptococcus bovis HC5 strains; elephant grass silage inoculated with 106 CFU/g Enterococcus faecium with six replications each. The pH and ammoniacal nitrogen values were lower (P<0.05) for the silages inoculated with Streptococcus bovis JB1 and HC5, respectively. The silage inoculated with Streptococcus bovis had a higher crude protein content (P<0.05) and there were no differences for the fiber contents in the silage. The (a)soluble fraction degradability, especially in the silages inoculated with Streptococcus bovis JB1 and HC5, had higher values, 30.77 and 29.97%, for dry matter and 31.01 and 36.66% for crude protein, respectively. Inoculation with Streptococcus bovis improved the fermentation profile, protein value and rumen degradability of the nutrients

Effect of yeast culture on milk production and metabolic and reproductive performance of early lactation dairy cows

<p>Abstract</p> <p>Background</p> <p>The main objective of this study was to estimate the effect of supplementation with <it>Saccaromyces cerevisiae (SC</it>) (Yea-Sacc^®1026) on milk production, metabolic parameters and the resumption of ovarian activity in early lactation dairy cows.</p> <p>Methods</p> <p>The experiment was conducted during 2005/2006 in a commercial tied-house farm with an average of 200 milking Estonian Holstein Friesian cows. The late pregnant multiparous cows (n = 46) were randomly divided into two groups; one group received 10 g yeast culture from two weeks before to 14 weeks after calving. The groups were fed a total mixed ration with silages and concentrates. Milk recording data and blood samples for plasma metabolites were taken. Resumption of luteal activity was determined using milk progesterone (P₄) measurements. Uterine bacteriology and ovarian ultrasonography (US) were performed and body condition scores (BCS) and clinical disease occurrences were recorded. For analysis, the statistical software Stata 9.2 and R were used to compute Cox proportional hazard and linear mixed models.</p> <p>Results</p> <p>The average milk production per cow did not differ between the groups (32.7 ± 6.4 vs 30.7 ± 5.3 kg/day in the SC and control groups respectively), but the production of milk fat (<it>P </it>< 0.001) and milk protein (<it>P </it>< 0.001) were higher in the SC group. There was no effect of treatment on BCS. The analysis of energy-related metabolites in early lactation showed no significant differences between the groups. In both groups higher levels of β-hydroxybutyrate (BHB) appeared from days 14 to 28 after parturition and the concentration of non-esterfied fatty acid (NEFA) was higher from days 1–7 post partum (PP). According to US and P₄results, all cows in both groups ovulated during the experimental period. The resumption of ovarian activity (first ovulations) and time required for elimination of bacteria from the uterus did not differ between the groups.</p> <p>Conclusion</p> <p>Supplementation with SC had an effect on milk protein and fat production, but did not influence the milk yield. No effects on PP metabolic status, bacterial elimination from the uterus nor the resumption of ovarian activity were found.</p