Compare and evaluate the application of ion chromatography and enzymatic colorimetry in the determination of choline in infant formula milk powder, and select a more suitable detection method for enterprise quality control.

A comparative analysis between ion chromatography and enzymatic colorimetry was conducted by using indicators such as standard curves, detection limits, precision, accuracy, uncertainty assessment and determination costs.

Both ion chromatography and enzymatic colorimetry demonstrated good linear relationships within their respective concentration ranges, with correlation coefficients (R²) of 0.999 7 and 0.999 1, respectively. The detection limits and quantification limits of ion chromatography were 0.7 mg/100 g and 2.1 mg/100 g, while those of enzymatic colorimetry were 0.9 mg/100 g and 2.7 mg/100 g. The recovery rates of ion chromatography and enzymatic colorimetry ranged were 90.7%~102.7% and 86.0%~100.6% (with the spiked amount ranging from 3 mg/100 g to 150 mg/100 g), respectively. The precision of ion chromatography (0.61%~3.83%) was superior to that of enzymatic colorimetry (1.30%~5.85%). The expanded uncertainties for ion chromatography and enzymatic colorimetry were 4.02% and 4.04%, respectively.

Ion chromatography demonstrated comparable advantages over enzymatic colorimetry in terms of sensitivity, precision and cost. It is more suitable for both qualitative and quantitative analysis of choline in infant formula and is recommended as the primary method for enterprises determination.

To establish an analytical method for determining the content of aflatoxin B₁ in cheese and milk using isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS).

After sample extraction, it was purified using an immunoprecipitation column, then concentrated by nitrogen evaporation. The content of aflatoxin B₁ was subsequently determined by LC-MS/MS after re-dissolution with the initial mobile phase.

The separation effect of the target analyte was good, and the analytical method was rapid and simple. Within the concentration range of 1 to 80 ng/mL, the samples were analyzed by sequentially injecting concentration standard solutions. The linear regression was performed using the ratio of the chromatographic peak area of aflatoxin B₁ to that of each corresponding internal standard as the ordinate and the concentration as the abscissa. The standard curve equation obtained was: Y=0.631 69-3.151 51×10^-4X, with a linear correlation coefficient (R²) of 0.999 82. The detection limit of aflatoxin B₁ in cheese samples was 0.02 μg/kg, and the quantification limit was 0.05 μg/kg, and the recovery rate ranged with spiked samples was 74.59% to 90.52%; the detection limit of aflatoxin B₁ in milk was 0.02 µg/kg, and the quantitative limit was 0.1 µg/kg, and the recovery rate with spiked samples was 79.85% to 100.63%.

This method had high accuracy, fast detection speed and excellent separation performance, and is suitable for quantitative analysis of aflatoxin B₁ content in cheese and milk samples.

This study aimed to investigate the application value of plant-derived lactic acid bacteria (LAB) in dairy cattle farming.

Using dairy cows from a specific farm as the research subjects, the trial established an experimental group (50 cows) and a control group (50 cows). The experimental group received plant-derived LAB supplemented in their concentrate feed and regular spraying of LAB in the barn and on their bodies. The effects on milk yield, health status, and farming environment were systematically analyzed.

The average daily milk yield of the experimental group reached 12.85 kg/cow/day, which was 25.86% higher than that of the control group (10.21 kg/cow/day). The incidence density of mastitis was 0.15 cases per hundred cow-days in the experimental group, 81.7% lower than that in the control group (0.82 cases per hundred cow-days). The incidence density of hoof disease was 0.23 cases per hundred cow-days in the experimental group, 54.0% lower than that in the control group (0.50 cases per hundred cow-days). The cost per unit of fresh milk was 4.198 RMB/kg in the experimental group, with an investment return rate of 1.82∶1.

Plant-derived lactic acid bacteria can significantly improve the barn hygiene conditions and enhanceheat dairy cattle' stress resistance, effectively improve the economic benefits of dairy cattle farming and possess high value for widespread application and promotion.

This research aimed to prepare soy yogurt using soybeans and milk as raw materials through fermentation technology. It systematically explored the effects of process parameters such as the ratio of soy milk to milk, the amount of sucrose added, the inoculation amount of bacteri, and the fermentation time on the product quality, in order to determine the optimal production formula.

A four-factor three-level orthogonal experimental design was adopted. By adjusting parameters such as the ratio of soy milk to cow milk, the amount of sucrose added, the inoculation amount of the bacteria, and the fermentation time, the prepared samples were evaluated for pH value, acidity, and sensory characteristics. The specific operations included: mixing the raw materials, sterilizing at 70 ℃ for 30 minutes, cooling to 43 ℃, inoculating the starter culture, and then fermenting at a constant temperature of 37 ℃.

The experiment results showed that when soy milk and cow milk are mixed in a 20∶80 ratio, 6% sucrose was added, the inoculation amount was 2%, after being sterilized at 70 ℃ for 30 minutes and then cooled to 43 ℃, the starter culture was inoculated and fermented at 37 ℃ for 9 hours, a high-quality soy yogurt with an appropriate acid and sweetness, uniform and delicate texture, good curd state, harmonious flavor and color consistent with the product characteristics could be prepared.

Through orthogonal experiments, the optimal combination of process parameters for soy yogurt was determined, namely a ratio of 20∶80 of soy milk to cow milk, a sugar addition of 6%, a bacterial inoculation amount of 2% and a fermentation time of 9 hours. This ratio scheme significantly improved the sensory quality and physicochemical properties of the yogurt, providing a scientifically feasible reference basis for home or small-scale production scenarios.

This study aimed to investigate the effects of different doses of carbetocin on the therapeutic efficacy for retained placenta, conception rate, and colostrum yield in dairy cows, in order to provide a theoretical basis for its rational clinical application in veterinary practice.

A total of 120 healthy Holstein cows were selected and randomly divided into 4 groups. The control group received an intramuscular injection of 10 mL normal saline within 10 minutes postpartum. The low-, medium-, and high-dose groups received intramuscular injections of carbetocin at doses of 250, 300, and 350 μg per head, respectively. The placental expulsion status and time, first-service conception rate, colostrum yield, and serum levels of inflammatory factors (IL-1β, IL-6, TNF-α) were observed and recorded for each group.

The results showed that as the dose of carbetocin increased, the incidence of retained placenta gradually decreased. The incidence in the medium- and high-dose groups was significantly lower than that in the control group (P < 0.05). The first-service conception rate was significantly higher in all treatment groups compared to the control group. Colostrum yield showed an increasing trend with dose, but the differences were not statistically significant. The serum levels of inflammatory factors were significantly lower in the medium-dose group compared to the control group.

This experiment indicates that carbetocin can effectively promote placental expulsion, improve the conception rate, and may reduce postpartum inflammatory responses. A dose of 300 μg per head is recommended for clinical use as an appropriate dose that balances efficacy and cost-effectiveness.

To systematically grasp the current status of key indicators for dairy cow breeding in large-scale pastures in Mudanjiang City, identify strengths and weaknesses in breeding management, and provide a scientific basis for improving regional dairy farming production efficiency and sustainable development levels.

In April 2024, a large-scale pasture in Mudanjiang City was selected as the research subject. Core data including herd structure, reproductive performance, disease incidence, culling/mortality rates, and lactation performance were collected through on-site investigation and compared with the national and Heilongjiang Province averages for the same period.

The herd structure of the pasture was relatively young but gradually stabilizing. The proportion of heifers at the beginning of the period was 29.0%, 32.2% by the end. Overall reproductive performance was at a medium level domestically. Pregnancy rates for timed artificial insemination and natural estrus were 43.9% and 39.1%, respectively. The calving interval was 382 days. Disease prevention and control achieved significant results, with low incidence rates for mammary and surgical diseases. However, obstetric diseases accounted for a high proportion (50.24%), and the incidence rate of internal medical diseases was 25.70%. The culling/mortality rate was slightly higher than the industry average. Dry cows had the highest rate (33.1%), followed by lactating cows (26.2%) and heifers (25.1%). Lactation performance had room for improvement. The average daily milk yield (29.3 kg) was higher than the national average, while the 305-day milk yield was 88 64 kg, milk fat percentage was 3.79%, and milk protein percentage was 3.32%, all lower than the national or Hei longjiang Province averages.

The pasture has foundational advantages in herd structure optimization and prevention/control of certain diseases. However, improvements are still needed in reproductive efficiency enhancement, obstetric and internal medical disease prevention/control, and lactation performance optimization. It is recommended to comprehensively enhance pasture breeding efficiency and production levels by strengthening precise reproductive management, optimizing the disease prevention and control system, scientifically adjusting feed formulations, and standardizing milking operations.