Tetracycline residues in meat and bone meals. Part 1: Methodology and examination of field samples

The incidence of tetracycline residues in commercially available samples of meat meals and meat and bone meals was investigated. Four different methods were used on each of the 87 samples from nine different rendering plants in Germany: examination using a screening fluorescence test; examination by high performance liquid chromatography analysis using three different extraction procedures (succinate buffer, hydrochloric acid, hydrochloric acid after sedimentation of bone particles). Tetracyclines were found in 100% of the samples by one or more of the extraction procedures. The highest concentrations found in meat meals were 2048 microgkg(-1), 1393 microgkg(-1) and 608 microgkg(-1) for oxytetracycline, tetracycline and chlortetracycline, respectively. In meat and bone meals the highest concentrations were 2295 microg oxytetracycline kg(-1) 848 microg tetracycline kg(-1) and 1274 microg chlortetracycline kg(-1). The extraction after sedimentation was the most effective of the applied extraction procedures and exposed the highest total tetracycline concentrations. The results of this investigation showed that considerable amounts of tetracyclines have to be expected in field samples. Further research has to be done on the heat stability of bound tetracycline residues.     

Validation of HPLC method of analysis of tetracycline residues in eggs and broiler meat and its application to a feeding trial

HPLC with ion-pairing chromatography and diodearray detection at 355nm was used to determine tetracycline antibiotics in eggs and broiler meat. The analytical methods were optimized and validated. The mean recovery values for oxytetracycline for eggs and for tetracycline for breast meat were 76% . The withinday precision ranged from 8.0 to 11.8% for oxytetracycline in eggs and from 6.1 to 15.5% for tetracycline in breast meat. The between-day precision was 4.8% and 5.0% respectively for oxytetracycline in eggs and tetracycline in breast meat. The limit of detection and the limit of quantitation for oxytetracycline in eggs were 2.2 and 13.0ng/g respectively. These limits for tetracycline in breast meat were 10.5 and 20.9ng/g respectively. Residue values of tetracycline antibiotics in eggs and broiler meat were determined after oral administration of medicated feed. Medicated feed with 840mg/kg oxytetracycline was provided to laying hens for seven successive days. Two days after the administration was stopped, the mean oxytetracycline residue value in the eggs was already lower than the Maximum Residue Limit (MRL)-level and reached 118ng/g. Broilers were supplied with medicated feed containing 480mg/kg tetracycline for seven successive days. Four days after the administration was stopped, the mean tetracycline residue value in breast meat decreased below the MRL and was 86ng/g.     

The effect of heat stress on thyroid hormone response and meat quality in turkeys of two genetic lines

The current study evaluated the effect of heat stress on thyroid hormone (T(3) and T(4)) response and meat quality traits in two turkey lines: a growth-selected commercial line and a genetically unimproved control line. Birds were subjected to heat stress for different durations before harvest. Commercial line had higher pH(15min), and lightness values, but lower cook loss and marinade uptake than control line during the heat stress. There was no difference in drip loss between the two lines. The T(3) concentration was positively correlated with cook loss and was negatively correlated with marinade uptake. The thyroid hormone response during heat stress was less stable in the commercial line than in the control line and the unstable thyroid hormone response in commercial turkeys caused by heat exposure might influence the consistency of meat quality. Results of this study may provide an application in selecting turkeys which yield consistent meat quality.     

The effect of transportation on the expression of heat shock proteins and meat quality of M. longissimus dorsi in pigs

This study investigates the effect of different transport times on meat quality and the correlation between meat quality and Hsp expression in M. longissimus dorsi (LD) of pigs. After transportation for 1 h, 2 h or 4 h, respectively, blood plasma creatine kinase (CK) and lactate dehydrogenase (LDH) increased. The LD meat from 1 h and 2 h transported pigs had lower initial and ultimate pH values (pHi and pHu, respectively), higher drip loss and L^∗ values compared to controls, indicating a higher likelihood of pale, soft and exudative (PSE) meat. Meat quality was lower after 2 h compared to 1 h or 4 h of transport. All four Hsps tested (alpha-B-crystalline, Hsp27, Hsp70 and Hsp90) by ELISA in the LD tissue of pigs tended to decrease after transportation. One possible mechanism resulting in poor meat quality in the LD after transport seems to be a decline in Hsp expression.     

The effect of various heat treatments on the antioxidant capacity of milk before and after simulated gastrointestinal digestion

Various reactions take place between compounds of milk during heat treatment including denaturation and aggregation of whey proteins, and formation of new complexes. In this study, the antioxidant capacities of raw, pasteurised and sterilised milk were determined both before and after an enzymatic in vitro digestion process, using a radical cation decolorisation assay. The mean values of raw, pasteurised and sterilised milk before simulated digestion were 4.02, 4.47 and 4.18 mM trolox/g, respectively, and these did not differ significantly. The antioxidant capacity of all milk types increased significantly at the end of the simulated gastrointestinal digestion, being 11.13, 12.33, 11.88 mM trolox/g for raw, pasteurised and sterilised milk, respectively.     

Application of near-infrared microscopy (NIRM) for the detection of meat and bone meals in animal feeds: A tool for food and feed safety

This paper reports on the development and validation of a method for detecting meat and bone meal (MBM) in compound feeds by near-infrared reflectance microscopy (NIRM) as an alternative in food and feed safety. A FT-NIR (Fourier transformer-near-infrared reflectance) instrument attached to a microscope was used to build up a spectral library containing reference feed particles identified as plant or animal origin, from various sources. Spectra were collected directly from particles in the NIR spectrum region (1112–2500 nm). The spectral library sample set was used to develop various discriminant models to classify spectra as MBM or plant material. The best discriminant model was obtained using partial least squares (PLS) discriminant analysis and standard normal variate and detrending (SNVD) and first derivative for spectrum pretreatment; this model had a coefficient of determination of 0.95 and a standard error of cross-validation of 0.133. The model was externally validated. The results confirmed NIRM as a valuable technique for detection of banned MBM.     

The effect of journey time and stocking density during transport on carcass and meat quality in rabbits

Four hundred and fifty hybrid commercial rabbits (half males and half females) at the end of their productive cycle (82 days old) were transported in cages (98 × 52 × 24 cm, length × width × height) at high or low density (75.5 or 49.0 kg/m² – 15 or 10 animals per cage) on an uncovered truck for 1, 2 or 4 h. Live weight before and after transport as well as slaughter data were recorded for each rabbit. A subset of 180 carcasses were evaluated for meat quality on the basis of meat pH, colour (CIELab system), cooking loss, drip loss and shear force. As a representative of the whole carcass muscle/bone ratio, the left hind leg was separated, dissected and its meat analysed in order to determine its water, protein, ash and lipid content. It was found that a longer journey significantly increases the live weight losses (3.3% vs. 2.0% vs. 1.6% for 4, 2 or 1 h, respectively; P < 0.001), as a result not only of urine and fecal losses, but also of a decrease in carcass weight (P < 0.01) during transport. Ultimate pH (pH_u) was higher and pH drop lower in rabbits transported for 4 h compared to those transported for 2 h (P < 0.05). Moreover, the meat from animals that had undergone the longest journey was more purple-red (P < 0.05), darker (P < 0.0001), and firmer when raw and showed less cooking loss than meat from those that underwent shorter journeys. Transport density did not influence any of the considered parameters and there was no interaction between transport time and density.     

The effect of using nonchlorine products for cleaning and sanitising milking equipment on bacterial numbers and residues in milk

Seven milking machine cleaning procedures which differed in the working solution content of sodium hydroxide, presence of chlorine, temperature of water, and inclusion of acid and four antimicrobial products used as sanitisers in the premilking rinse water were evaluated. The cleaning system, which incorporated a high working solution of sodium hydroxide (2525 ppm) used in cold water combined with a hot (70 °C) daily acid wash, had lower total bacterial counts (TBC) (1040 colony forming units (cfu)/mL) than the same detergent product without the addition of acid (1980 cfu/mL) (P < 0.05). Lower TBC were observed in milk and on equipment surfaces when a sanitiser was applied (P < 0.01). Trichloromethane levels in milk were higher when chlorine was used as a sanitiser (P < 0.01).     

The effect of experimental stress on sarcoplasmic reticulum Ca transport and meat quality in pig muscle

Stress before slaughter affects the meat quality of pigs and a disorder in the Ca²⁺ transport of the sarcoplasmic reticulum (SR) results in inferior meat quality. The object of this work was to determine the impact of stress on SR Ca²⁺ transport in pig muscle in animals with no mutation in the Ca²⁺ release channel. At about 80 kg live weight, pigs were stressed either by running for 4 min (n=9) or by a 5 min application of a nose snare (n=7). Immediately before and after the application of the stress, as well as 4 h after the stress, biopsy samples of the longissimus muscle were taken and the Ca²⁺ uptake of the homogenised muscle samples determined. The nose snare stress reduced the rate of Ca²⁺ uptake by 9% (P=0.02) and running by 18% (P=0.06). Uptake in samples taken 4 h after the stress was at initial levels. The pigs were slaughtered at an average live weight of 109 kg. Half the pigs were stressed just before slaughter for 5 min by the use of a nose snare. Immediately after exsanguination longissimus muscle samples were taken, Ca²⁺ uptake measured, and later standard meat quality parameters were determined. Although the stress reduced the Ca²⁺ uptake rate (61.3 vs. 46.4 nM/min per mg protein for control and stressed pigs; P=0.04), the meat quality was not significantly affected.     

The effect of growth rate during backgrounding and finishing on meat quality traits in beef cattle

The relationship between growth rate and meat tenderness was investigated in ≈7000 cattle from temperate and tropically adapted breeds, finished on either pasture or in a feedlot to one of three market weights. Growth rate was calculated from weaning to the beginning of finishing (backgrounding) and over the finishing period, for both contemporary groups and individuals within these groups. Shear force and compression of longissimus lumborum (striploin) and semitendinosus (eye round) were measured at two days ageing, and palatability of the striploin at 14 days ageing. Analyses assessed the importance of growth rate during backgrounding and finishing on both a within group and between group basis. Where significant in individual animals, increased growth rate resulted in more palatable or tender meat, but the results were not consistent between breed types, locations, or the two muscles sampled. The most consistent relationship was an increase in palatability of the striploin with increased growth rate during finishing. Increased growth rate of groups during backgrounding improved palatability consistently across breedtypes, finish and location, however most of this relationship was accounted for by difference in mean group age at slaughter.