Residual feed intake (RFI), defined as the difference between an animal's actual feed intake and expected feed intake over a specific period, is an inheritable character of feed conversion efficiency in dairy cows. Research has shown that a lower RFI could improve the profitability of milk production. This study explored variation in RFI by comparing the differences in body size, milk performance, feeding behavior, and serum metabolites in 29 Holstein cows in mid lactation. The cows were selected from a total of 84 animals based on their RFI following feedlot tests. Selected cows were ranked into high RFI (RFI > 1 SD above the mean, n = 14) and low RFI (RFI < 1 SD below the mean, n = 15). The low RFI cows (more efficient) consumed 1.59 kg/day less dry matter than the high RFI group ( P < 0.01), while they produced nearly equal 4% fat-corrected milk. The milk : feed ratio was higher for the low RFI group than for the high RFI group ( P < 0.05). The levels of milk protein ( P < 0.01), total solids ( P < 0.05), and nonfat solids ( P < 0.05) were also higher for the low RFI group, whereas milk urea nitrogen was lower ( P < 0.01). The daily feeding duration was shorter for the low RFI group than for the high RFI group ( P < 0.01). No significant differences were found in levels of glucose, β-hydroxybutyrate, prolactin, insulin, IGF-1, growth hormone or ghrelin, but the level of neuropeptide Y was higher ( P < 0.01) and levels of leptin and non-esterified fatty acid ( P < 0.05) were lower for the low RFI group than for the high RFI group. There were substantial differences between cows with different RFI, which might affect the efficiency of milk protein metabolism and fat mobilization.

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A highly sensitive method for the determination of arprocarb (AC), carbofuran (CF), isoprocarb (IC), and fenobucarb (FC) is proposed. The method is based on alkaline hydrolysis of the four carbamate pesticides, and the resultant hydrolysis products are reacted with 4-aminoantipyrene (AP) to give four red color products. The colored compounds are enriched and separated by cloud point extraction (CPE) method, and the coacervate phase containing the compounds is determined with a high-performance liquid chromatography (HPLC) system in the visible region. AC, CF, IC, and FC were determined on the basis of a linear correlation between the signals of the colored compounds and the concentrations of the pesticides. The method is applied to determine the four pesticides in corn samples; the limits of detection are 2.0 x 10(-4) mg L(-1) for AC, CF, and IC and 5.0 x 10(-4) mg L(-1) for FC, with recoveries ranging between 84.8 and 93.0%, at spiking levels of 5 x 10(-3), 2 x 10(-2), and 0.2 mg kg(-1), respectively.

The objective of the present study was to explore the changes in fatty acids (FAs) and minerals composition in sow milk in order to improve the knowledge about FAs and mineral requirements for piglets. The FAs and minerals composition in the sow milk samples which were collected from ten sows during a period of 16 days of lactation was analysed. The proportion of FAs in sow milk has a significant increase in C8:0, C10:0, C12:0, C14:0, C16:0, C14:1 and C16:1 FAs and the sum of saturated fatty acids (SFAs) according to the lactation period (p < 0.05). The proportion of C18:2 cis‐9,12 FA and the sum of polyunsaturated fatty acids (PUFAs) significantly decreased with the advancing of lactation (p < 0.05). The concentrations of minerals, including potassium, copper, manganese and zinc, were higher on day 1 and day 2 than those on day 13 and day 16 (p < 0.05). On the contrary, the lowest concentrations of calcium, sodium, magnesium and iron and the lowest molar calcium: phosphorus ratio emerged in colostrum (p < 0.05). In summary, our results demonstrated FAs profile and minerals concentrations were changed with lactation period. Better understanding of the changes of FAs and minerals may be valuable to swine nutritionists in the commercial industry. In addition, those results provided some meaningful information for sow's diet formulation during lactation.

A new method for determination of 16 polycyclic aromatic hydrocarbons (PAHs)-naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene-in vegetable oils was developed. Solid-phase extraction (SPE) prior to high-performance liquid chromatography with fluorescence detection could be used for all those PAHs except acenaphthylene. Acenaphthylene could be detected using a diode array detector at 228 nm. The parameters and variables that affect the extraction were investigated. Under optimum conditions: the extract reagent was centrifuged at 4 °C and evaporated. After that a SPE procedure was used for further cleanup. The limits of detection and limits of quantification were in the range of 0.01-2.35 and 0.04-7.00 μg kg(-1) in vegetable oil, respectively. The relative standard deviations were under 5%.