Impact of α-amylase supplementation on energy balance and performance of high-yielding dairy cows on moderate starch feeding

In dairy cows, exogenous α-amylase is suggested to improve starch utilization and positively affect performance and health traits linked to energy balance and fertility. In a 1-year feeding experiment, 421 cows were orally supplemented with α-amylase (treatment: 12.5 g/kg dry matter (DM) addition rate to a concentrated feed) or non-supplemented (control) on the basis of an ad libitum total mixed ration (TMR). Every cow was allocated to a high- (≥32 kg milk/day) or late-lactation group (<32 kg milk/day), in which the TMR starch content was 220 ± 20.8 g/kg DM and 183 ± 24.8 g/kg DM, respectively. The energetic effect of α-amylase supplementation seemed to be exclusively related to the high-lactation stage (5-100 days in milk) in primiparous cows, where the daily milk yield was 32 ± 0.49 versus 31 ± 0.50 kg per cow in the treatment versus control group (P < 0.05). The pluriparous cows did not benefit from the supplementation that way. In neither primiparous nor pluriparous cows, was the milk composition, the fat-to-protein ratio, the somatic cell score, the backfat thickness, serum total bilirubin, β-hydroxybutyrate and the fertility found to be systematically affected by α-amylase supplementation.

Effect of feeding 25-hydroxyvitamin D3 with a negative cation-anion difference diet on calcium and vitamin D status of periparturient cows and their calves

Holstein cows (>1 gestation) were fed 1 of 3 diets during the last 13 d of gestation (ranged from 22 to 7 d). The control diet (16 cows) was formulated to provide 18,000 IU/d of vitamin D3 and had a dietary cation-anion difference (DCAD) of 165mEq/kg (DCAD=Na + K - Cl - S). The second diet (DCAD + D) provided the same amount of vitamin D3 but had a DCAD of -139mEq/kg (17 cows). The third diet (DCAD + 25D) had no supplemental vitamin D3 but provided 6mg/d of 25-(OH) vitamin D3 [25-(OH)D3] with a DCAD of -138mEq/kg (20 cows). Diets were fed until parturition and then all cows were fed a common lactation diet that contained vitamin D3. Negative DCAD diets reduced urine pH, with the greatest decrease occurring with the DCAD + D treatment. Urinary Ca excretion was greatest for cows fed DCAD + 25D followed by cows fed DCAD + D. Urinary pH was negatively correlated with urinary excretion of Ca for cows fed DCAD + D. No such correlation was observed with the DCAD + 25D treatment because substantial excretion of urinary Ca occurred at moderate urinary pH values for that treatment. Cows fed DCAD + 25D had greater serum concentrations of 25-(OH)D3 than other treatments from 5 d after supplementation started through 7 d in milk. Concentrations of 1,25-(OH)2D3 in serum were greatest in DCAD + 25D cows starting at 2 d before calving and continued through 7 d in milk. Serum Ca concentrations 5 d before calving were greatest for cows fed DCAD + 25D, but at other time points before and after parturition treatment did not affect serum Ca. Incidence of clinical hypocalcemia was not statistically different between treatments, but cows fed DCAD + 25 had the highest incidence rate (12.5, 0, and 20% for control, DCAD + D, and DCAD + 25D). Calves born from cows fed DCAD + 25D had greater concentrations of 25-(OH)D3 in serum at birth than calves from other treatments (before colostrum consumption), but concentrations were similar by 3 d of age. Concentrations of 25-(OH)D3 in colostrum and transition milk were increased by feeding DCAD + 25D, but by 28 d in milk treatment effects no longer existed. Overall, feeding 25-OH vitamin D with a negative DCAD diet increased vitamin D status of the cow and her newborn calf but had minimal effects on calcium status and did not have positive effects on the incidence of hypocalcemia.

The degradation of arabinoxylan-rich cell walls in digesta obtained from piglets fed wheat-based diets varies depending on digesta collection site, type of cereal, and source of exogenous xylanase

The objective of the present study was to compare the ability of experimental and commercial xylanases to degrade, in vitro, the arabinoxylan (AX) fraction in digesta from 28-d-old piglets fed a wheat (Triticum aestivum)-based diet (49% wheat). Pigs were euthanized at 1, 2, 3, or 4 h after feeding; stomach and ileum contents were isolated and frozen and later used for the in vitro studies. Xylan solubilization provided information regarding the ability of the enzymes to degrade AX during the harsh in vivo conditions prevailing in the gastrointestinal tract. The hydrolytic capacity of a commercial xylanase was compared with that of an experimental xylanase using stomach digesta (pH 1.8) obtained at 4 h after feeding. Relative to the control, both enzymes increased (P < 0.001) xylan solubilization 3-fold. In the ileal digesta (1 h), xylan solubilization was increased by 36% (P < 0.001). Inclusion of arabinofuranosidases (Ara f) with xylanases increased xylan solubilization in stomach samples (P = 0. 007 and P = 0. 030) but not in ileal samples (P = 0.873 and P = 0.997). Our results illustrate clearly the importance of using different conditions and substrates when enzyme performance is studied in vitro as a prescreening tool for setting up in vivo trials.

Evaluation of a rapid-format antibody test and the tuberculin skin test for diagnosis of tuberculosis in two contrasting endemic settings

OBJECTIVE AND SETTING

We evaluated a rapid-format antibody card test and the tuberculin skin test for diagnosis of active tuberculosis (TB) in high (Cairo, Egypt) and low (St. Louis, USA) prevalence areas.

DESIGN

Prospective study of hospitalized TB patients and controls with other chest diseases.

RESULTS

Test performance varied significantly in the two study sites. The antibody test detected 87% of 71 smear-positive pulmonary TB cases (86% of smear-negative pulmonary cases and 48% of TB meningitis cases) in Egypt; specificity was 82%. The tuberculin test was highly sensitive in Egypt in subjects with pulmonary TB (100%) but not in those with meningitis (23%); specificity was 70%. The sensitivity and specificity of the antibody test in St. Louis were 29% and 79%, respectively; 50% of St. Louis TB cases and 15% of controls had positive tuberculin tests.

CONCLUSIONS

This convenient antibody card test may have value for diagnosis of patients suspected of having TB in high prevalence areas like Egypt. However, the specificity of the test is too low for it to be useful as a screening test. Our results suggest that neither the antibody test nor the tuberculin test have much diagnostic utility in low prevalence settings like St. Louis.