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[CA] El formatge de Tronchón és un formatge tradicional elaborat amb llet d'ovella o cabra a la zona del Maestrat (províncies de Castelló, Terol i Tarragona) que es troba dins de la marca de qualitat CV (Comunitat Valenciana). La qualitat del formatge depèn fonamentalment de la llet utilitzada com a matèria primera, així com del procés de fabricació. Per això, és important conèixer de quina manera afecten els paràmetres de qualitat de la llet a la qualitat del producte final i la seua relació amb l'eficàcia del procés d'elaboració. L'objectiu principal d'aquest estudi ha estat la caracterització del formatge de Tronchón de llet crua de cabra i la valoració de l'eficàcia del seu procés de fabricació a través del rendiment formatger i la recuperació dels principals nutrients com són el greix i la proteïna del formatge. Per a la caracterització del formatge es van emprar els resultats de 40 fabricacions de formatge de Tronchón realitzades en diferents anys a partir de llet de cabra de la raça Murciano-Granadina, en tres moments de la lactació (inici: fins al dia 80, meitat: entre els 100 i 160 dies i final: més de 160 dies). De cada fabricació es van determinar els paràmetres de qualitat de la llet (pH, composició, recompte de cèl·lules somàtiques i recompte de gèrmens totals) i del formatge (pH, composició, índex de lipòlisis, índex de proteòlisi, perfil de textura i color). També en 16 d'aquestes fabricacions es va calcular el rendiment formatger i la recuperació de greix i proteïna per poder valorar l'eficàcia del procés d'elaboració. Els resultats obtinguts indiquen que la qualitat de la llet emprada en les fabricacions de formatge de Tronchón presenta els valors habituals de la raça Murciano-Granadina i que tots els paràmetres analitzats varien significativament amb l'estat de lactació excepte el recompte de cèl·lules somàtiques. Pel que fa al formatge de Tronchón va presentar unes característiques fisicoquímiques, de duresa i color similars a la d'altres formatge, [EN] Tronchón cheese is a traditional cheese made from sheep or goat's milk in the Maestrazgo area (provinces of Castellón, Teruel and Tarragona) that is within the CV quality mark (Comunitat Valenciana). The quality of the cheese depends fundamentally on the milk used as raw material, as well as on the manufacturing process. For this reason, it is important to know how the milk quality parameters affect the quality of the final product and their relationship with the efficiency of the production process. The main objective of this study has been the characterization of the Tronchón cheese made from raw goat's milk and the evaluation of the efficiency of its manufacturing process through the cheese yield and the recovery of the main nutrients such as fat and protein in the cheese. For the characterization of the cheese, the results of 40 Tronchón cheese fabrications made in different years from goat milk of the Murciano-Granadina breed were used, at three moments of lactation (beginning: until day 80, half: between the 100 and 160 days and final: more than 160 days). For each production, the quality parameters of the milk (pH, composition, somatic cell count and total germ count) and of the cheese (pH, composition, lipolysis index, proteolysis index, texture profile and color) were determined. Also, in 16 of these productions, the cheese yield and the recovery of fat and protein were calculated to be able to assess the efficiency of the production process. The results obtained indicate that the quality of the milk used in the Tronchón cheese manufacture presents the usual values of the Murciano-Granadina goat breed and that all the parameters analyzed vary significantly with the state of lactation except the somatic cell count. As for the Tronchón cheese, it presented physicochemical characteristics, textural parameters and color similar to that of other Spanish goat cheeses with two months of maturation. Depending on the fat content of the cheese, it can be classif

[ES] La leche de cabra se destina principalmente a la elaboración de queso. En general se considera que la aptitud de la leche para su transformación en este producto lácteo depende de diferentes factores como las propiedades fisicoquímicas, composición química, calidad higiénica y comportamiento frente al cuajo. Sin embargo, la industria suele pagar la leche al ganadero, principalmente, por su contenido en grasa y proteína, ya que son los componentes que más influyen sobre el rendimiento quesero. El objetivo de este trabajo es el estudio de las propiedades de coagulación de la leche de cabra Murciano-Granadina y su relación con las variables de calidad de la leche cruda habitualmente analizadas en los laboratorios interprofesionales. Para ello, se analizaron un total de 160 muestras individuales de leche de cabra Murciano-Granadina procedentes de seis explotaciones comerciales de caprino lechero de la Comunidad Valencia. En cada muestra de leche se determinaron específicamente variables de calidad tecnológica (propiedades de coagulación, rendimiento en cuajada, extracto seco de la cuajada y contenido en grasa y proteína del lactosuero) y otros parámetros que son habitualmente analizados en la leche cruda (composición química, recuento de células somáticas, acidez de la leche). Los resultados obtenidos indican que las propiedades de coagulación de la leche se ven afectadas por la composición química y la calidad higiénica de la leche. En general, cuando se incrementa la materia seca de la leche tiende a aumentar el tiempo que tarda en iniciarse la coagulación, la rapidez de endurecimiento de la cuajada, su dureza y el rendimiento quesero. Por el contrario, el recuento de células somáticas tiene un efecto negativo sobre el tiempo de coagulación y la dureza de la cuajada, sin afectar de forma significativa al rendimiento en cuajada. Las ecuaciones de predicción de las propiedades de coagulación a partir de las características de calidad la leche presentaron unos coefi, [EN] Goat's milk is mainly used for cheese production. In general, it is considered that the technological aptitude of milk for its transformation into this dairy product depends on different factors such as physical-chemical properties, chemical composition, hygienic quality, and behavior against rennet. However, the industry tends to pay milk to the farmer mainly for its fat and protein content, as they are the main milk components affecting cheese yield. The aim of this work is the study of the coagulation properties of Murciano-Granadina goat's milk and its relationship to the raw milk quality variables commonly analyzed in the interprofessional laboratories. To this end, a total of 160 individual samples of Murciano-Granadina goat's milk from six commercial dairy goat farms in the Valencia Community region were analysed. On each milk sample technological quality variables (coagulation properties, curd yield, dry curd extract and fat and protein content in milk whey) were specifically determined as well as other parameters that are commonly analysed in raw milk (chemical composition, somatic cell count and milk acidity). Results herein indicate that the milk coagulation properties are affected by the chemical composition and hygienic quality of milk. In general, when the milk dry matter is increased tends to increase the time required to start milk coagulation, the coagulation rate, its firmness and the curd yield. In contrast, somatic cell count has a negative effect on coagulation time and curd firmness, without significantly affecting curd yield. The predictive equations of milk coagulation properties from milk quality characteristics had very low determination coefficients (R2= 0.33-0.56) so they would not be in application for practical purposes. Only curd yield could be acceptably estimated using dry matter (R2= 0.67) or useful dry extract (R2= 0.64) as predictors, or the latter in combination with the lactose content (R2= 0.70) and, in addition, the milk

[ES] El objetivo de este trabajo fue el de hallar una metodología que permitiera determinar la presencia de mamitis subclínica en el ganado caprino a partir de los análisis realizados con la Espectroscopía de Infrarrojo Medio con Transformada de Fourier (FT-MIR) en las muestras del Control Lechero Oficial. Para ello, se tomaron 540 muestras de leche de 180 cabras de raza Murciano-Granadina (360 muestras de glándula mamaria y 180 de leche ordeñada) procedentes de 7 granjas de la Comunidad Valenciana. Los animales fueron seleccionados para asegurar una elevada variabilidad en el RCS, número y mes de lactación. En las muestras de leche ordeñada se analizaron los marcadores inflamatorios lactoferrina, ¿Milk Amiloyd A¿ (MAA) y el Recuento de Células Somáticas (RCS) como estimadores de la presencia de mamitis. En las muestras de glándula mamaria se llevó a cabo un análisis bacteriológico, para determinar la presencia o ausencia de infección intramamaria. Los tres marcadores inflamatorios fueron analizados estadísticamente con objeto de identificar sus factores de variación. La lactoferrina varió significativamente con el factor granja, pero no por la presencia de infección intramamaria ni por el mes de lactación. El MAA también presentó diferencias significativas entre granjas. Además, tanto el MAA como el RCS aumentaron en los animales afectados de mamitis subclínica y en aquellos que se encontraban en un estado de lactación más avanzado. El número de lactación de las cabras no afectó significativamente a ninguno de los tres marcadores estudiados. Las calibraciones realizadas para estimar con FT-MIR el contenido de estos tres marcadores inflamatorios en las muestras del control lechero presentaron una baja precisión (coeficiente de determinación de 0,42 a 0,78; varianza explicada del 0,31 a 0,65). Por lo tanto, se concluye que, por el momento, no es posible identificar a los animales afectados de mamitis subclínica a partir de los análisis FT-MIR en las muestras del cont, [EN] The aim of this work was to find a methodology that would allow determining the presence of subclinical mastitis in goats from the analyzes carried out with Fourier Transform Mid-Infrared Spectroscopy (FT-MIR) in the Official Milk Control samples. 540 milk samples were taken from 180 goats of the Murciano-Granadina breed (360 samples from the mammary gland and 180 from milked milk) from 7 farms in the Valencian Community. The animals were selected to ensure high variability in SCR, number and month of lactation. In the milked samples, the inflammatory markers lactoferrin, "Milk Amiloyd A" (MAA) and the Somatic Cell Count (SCC) were analyzed as estimators of the presence of mastitis. Bacteriological analysis was carried out on the mammary gland samples to determine the presence or absence of intramammary infection. The three inflammatory markers were statistically analyzed in order to identify their variation factors. Lactoferrin varied significantly with the farm factor, but not due to the presence of intramammary infection or the month of lactation. The MAA also showed significant differences between farms. Furthermore, both MAA and RCS increased in animals affected by subclinical mastitis and in those that were in a more advanced lactation stage. The lactation number of the goats did not significantly affect any of the three markers studied. The calibrations performed to estimate with FT-MIR the content of these three inflammatory markers in the milk control samples showed low precision (coefficient of determination from 0.42 to 0.78; explained variance from 0.31 to 0.65). Therefore, it is concluded that, at the moment, it is not possible to identify the animals affected by subclinical mastitis from the FT-MIR analyzes in the samples of the dairy control.

[EN] The hypothesis of this experiment proposes that it could be possible to identify pregnant goats through maximum progesterone milk levels at any time in the pregnancy, and that there is an optimal moment to apply a lactation inhibitor to dry off lactating goats. The maximum progesterone concentration in milk varied depending on the season of the year, and those concentrations were similar for pregnant and non-pregnant goats, but significantly higher in the case of gestating goats with four foetuses, for which it would be possible to distinguish the pregnancy. The milk yield of goats at mating does not affect fertility until a value of at least 3250 mL/day. If using lactation inhibitors, their application up to the 10th week post-mating would be optimal for drying off lactating goats. Two of the most important problems in high-yielding dairy goat farms are early and accurate pregnancy diagnosis and the appropriate dry off of lactating does before the next kidding. The hypothesis posits that it could be possible to identify pregnant does through maximum progesterone milk levels at any time during the pregnancy, and that there is an optimal time to apply a lactation inhibitor to help dry off lactating does. Therefore, 114 Murciano-Granadina breed goats were used, from which 74 goats were inseminated at week 20 of lactation and samples of milk from pregnant and non-pregnant goats were taken at two-week intervals. The average maximum progesterone milk levels were higher outside the natural breeding season (40 degrees latitude) than in the breeding season (11.6 +/- 1.13 vs. 8.6 +/- 1.02 ng/mL), although the levels from pregnant and non-pregnant goats were similar (10.85 +/- 1.3 vs. 9.74 +/- 1.6 ng/mL), except in the case of pregnancy with four foetuses (12.5 +/- 1.3 ng/mL). Milk yield at mating does not affect fertility until a value of at least 3250 mL/day. Pregnancy started to affect milk yield up to the +7th week and was 59.9% lower in the +10th week after mating

[EN] The effect of the dietary inclusion of lemon leaves and rice straw by-products on the quality characteristics of goats' milk and cheese was evaluated. Twenty-six Murciano-Granadina goats were used in a crossover design experiment; milk from each experimental group was collected to produce 60-days matured cheeses. Fat and dry matter content was higher in milk and cheeses from the diet containing by-products; medium-chain fatty acids and total free fatty acids were lower. Triangle tests revealed significant differences in the organoleptic characteristics of the cheeses between diets. However, when sensory attributes differentiating cheeses were evaluated individually, differences did not become significant. The inclusion of lemon leaves and rice straw in balanced diets with soya oil could be beneficial, as it does not appear to adversely affect the quality of milk and related mature cheeses, contributing to the reduction of the cost of the diet and the recycling of agricultural by-products. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

[EN] The presence of antibiotics in milk destined for cheese production may affect the biological processes responsible for the formation of volatile compounds, leading to alterations in the characteristic cheese flavor expected by consumers. The aim of this study was to evaluate the effect of the presence of oxytetracycline in goat milk on the volatile profile of ripened cheeses. Traditional mature Tronchón cheeses were manufactured from raw goat milk spiked with different concentrations of oxytetracycline (50, 100, and 200 ug/kg). Cheese made from antibiotic-free goat milk was used as control. We analyzed the residual amounts of the antibiotic and the volatile profile of the experimental cheeses on a fortnightly basis during maturation using liquid chromatography tandem mass spectrometry and then solid-phase microextraction followed by gas chromatography-mass spectrometry. Our results suggested that oxytetracycline was widely transferred from milk to cheese: drug concentrations in the cheeses were 3.5 to 4.3 times higher than those in raw milk. Although the residual amounts of oxytetracycline significantly decreased during maturation (88.8 to 96.5%), variable amounts of residues remained in cheese matured for 60 d (<10 to 79 ug/kg). In general, the presence of oxytetracycline in goat milk did not affect the volatile profile of Tronchón cheeses; volatile profile was significantly modified by ripening time. Still, the presence of oxytetracycline residues in cheeses ripened for 60 d could be of great concern for public health.

[ES] La presencia de residuos de antibióticos en la leche y los productos derivados representa un riesgo para los consumidores. Límites Máximos de Residuos (LMRs) no se han fijado para los productos lácteos y la transferencia de antibióticos de la leche a la cuajada y al lactosuero durante el proceso de elaboración del queso apenas ha sido estudiada. El objetivo de esta tesis fue evaluar la transferencia de antibióticos de la leche al queso y lactosuero, así como la validación de las características de varios métodos de cribado para la detección de antibióticos en muestras de suero de leche. En el primer estudio, el objetivo fue validar un método UHPLC-HRMS multi-residuo utilizando el analizador Orbitrap ExactiveTM, para el cribado cuantitativo de antibióticos en muestras de leche, queso fresco y lactosuero de acuerdo con los criterios especificados en la Decisión 657/2002/CE de la Comisión. El estudio de distribución mediante el método UHPLC-HRMS indicó que la mayor parte de antibióticos se transfirieron principalmente de la leche a la fracción lactosuero (hasta el 85,9%) durante la elaboración de queso. Por tanto, los porcentajes de retención de antibióticos en la cuajada fueron inferiores al 50%, excepto en el caso del ceftiofur (59,7%) y la dicloxacilina (52,8%), y muy variables entre los distintos antimicrobianos. En la mayor parte de los casos, la distribución de medicamentos no se vio afectada por la concentración de antibióticos presente en la leche, y estuvo escasamente relacionada con la lipofilicidad de los antibióticos. En el segundo estudio, se evaluaron las características de diferentes métodos de detección de antibióticos en muestras de lactosuero de acuerdo con la Decisión 657/2002/CE de la Comisión. En primer lugar, la especificidad (porcentaje de falsos positivos) y la capacidad de detección (CCß) del método de detección de inhibidores Eclipse Farm provisto del dispositivo e-Reader y de los métodos de unión a receptores 3Aminosensor, Quinosensor, T, [CA] La presència de residus d'antibiòtics en la llet i els productes derivats representa un risc per a la salut del consumidor. Límits Màxims de Residus (LMRs) no s'han fixat per als productes lactis i la transferència d'antibiòtics de la llet al formatge i al sèrum durant el procés d'elaboració del formatge quasi no s'ha estudiat. L'objectiu d'aquesta tesi va ser avaluar la transferència d'antibiòtics de la llet a les fraccions formatge i sèrum, així com la validació de la resposta de diversos mètodes per a la detecció d'antibiòtics en mostres de sèrum de llet. En el primer estudi, l'objectiu va ser validar un mètode UHPLC-HRMS multi-residu utilitzant l'analitzador Orbitrap ExactiveTM, per al garbellat quantitatiu d'antibiòtics en mostres de llet, formatge fresc i sèrum, d'acord amb els criteris especificats en la Decisió 657/2002/CE de la Comissió. L'estudi de partició utilitzant UHPLC-HRMS mètode va indicar que la major part d'antibiòtics es van transferir principalment de la llet a la fracció sèrum de llet (fins al 85,9%) durant l'elaboració de formatge. Per tant, els percentatges de retenció d'antibiòtics en la quallada van ser inferiors al 50%, excepte en el cas del ceftiofur (59,7%) i la dicloxacilina (52,8%), i molt variables entre els diferents fàrmacs. En la majoria dels casos, la distribució de medicaments no es va veure afectada per la concentració d'antibiòtics present en la llet per a la producció de formatge, i va estar escassament relacionada amb la lipofilicitat dels antibiòtics. En el segon estudi, es van avaluar les característiques de diferents mètodes de detecció d'antibiòtics en mostres de sèrum d'acord amb la Decisió 657/2002/CE de la Comissió. L'especificitat (percentatge de falsos positius) i la capacitat de detecció (CCß) d'una prova d'inhibició microbiana (Eclipse Farm acoblat al dispositiu e-Reader) i d'assajos d'unió a receptors (3Aminosensor, Quinosensor, Twinsensor i Tylosensor) es van avaluar en mostres de sèrum de llet de cabra, obt, [EN] The presence of antibiotic residues in milk and dairy products poses a risk for consumer health, mainly the development of antimicrobial resistance. Maximum Residue Limits (MRLs) for veterinary drugs have not been established for dairy products. Furthermore, the transfer of antibiotics from milk to cheese and whey fractions during cheese-making has been scarcely studied and, therefore, the impact of the use of whey containing antibiotics for the manufacture of foodstuffs for human and animal consumption is unknown. The aim of this thesis was to evaluate the transfer of antibiotics from milk to cheese and whey fractions, as well as the validation of the performance of several methods to screen antibiotics in whey samples. In the first study, a multiresidue UHPLC-HRMS method using the Orbitrap ExactiveTM analyser for the quantitative screening of antibiotics in milk, fresh cheese, and whey samples was validated according to Commission Decision 2002/657/EC, using samples from three different dairy matrices (milk, fresh cheese and whey) from cows, sheep and goats. The partitioning study by UHPLC-HRMS method indicated that most antibiotics were mainly transferred from milk to whey fraction (up to 85.9%) during cheese-making. Thus, retention rates in the rennet curd fraction were lower than 50%, except for ceftiofur (59.7%) and dicloxacillin (52.8%), and very variable between drugs. In most cases, drug distribution was unaffected by the antibiotic concentration present in milk for cheese production and was poorly related to the drug lipophilicity. In the second study, the performance of different methods for screening antibiotics in whey samples was evaluated in accordance with Commission Decision 2002/657/EC, by conducting three experiments focused on commercially available screening tests, microtiter plate bioassays, and a semi-quantitative multi-plate system, respectively. Specificity (false-positive rate) and Detection Capability (CCß) of a microbial inhibitor te

[Otros] La présence de résidus d'antibiotiques dans les produits laitiers peut constituer un problème pour la santé publique et pour l'industrie laitière. Dans ce travail, nous avons évalué l'effet de la présence de néomycine dans le lait de chèvre sur la fabrication et les caractéristiques du fromage Tronchón. Les fromages ont été fabriqués, en double exemplaire, à partir du lait de chèvre cru sans antibiotiques et avec l'addition de néomycine à la limite maximale de résidu (1500 ug/kg). Nous avons étudié les changements dans les caractéristiques du fromage et la présence de résidus à différentes périodes de maturation (1, 30 et 60 jours). La durée du procédé de fabrication augmentait (48 ± 18 min) sous l'effet de la présence de néomycine dans le lait de chèvre. Concernant les caractéristiques du fromage, nous avons observé une diminution dans les valeurs de l'activité de l¿eau ainsi qu¿une réduction dans les concentrations d'acides gras libres et d'acides aminés libres dans les fromages avec l'antibiotique, en suggérant une activité biochimique mineure pendant la maturation. Nous avons aussi observé une plus grande légèreté, moins rougeur et une plus faible élasticité dans ce type de fromage. En plus, pendant la maturation, les concentrations de néomycine dans le fromage augmentaient 4,9 fois par rapport à la concentration initiale dans le lait, ce qui pourrait impliquer un risque pour la santé publique., [EN] Antibiotic residues in milk and dairy products are a potential problem for public health, and for the dairy industry. This study investigated the effect of the presence of neomycin in goat's milk on the production and characteristics of semi-hard Tronchón cheese. Cheeses were made, in duplicate, from raw goat's milk without antibiotics and with addition of neomycin at the Maximum Residue Limit (1500 ug/kg). Possible chan ges in the characteristics and the presence of antibiotic residues in the cheeses were evaluated at different time points along ripening (1, 30 and 60 days). Processing time was increased (48 ± 18 min) by the presence of neomycin in milk. Regarding cheeses, lower values of water activity as well as reduced free fatty acids and free amino-acid concentrations were detected in cheeses from milk with the antibiotic, suggesting a minor biochemical activity throughout ripening. Thus, a greater lightness and lower redness value were observed in this type of cheese, also presenting lower springiness. Moreover, high concentrations of neomycin were retained in the cheese and concentrated during ripening, leading to a concentration factor of 4.9, with respect to the initial concentration in the milk, potentially implying a risk to public health.

[EN] The aim of this study was to evaluate the transfer of the most widely used antibiotics in dairy goats from milk to cheese as well as their effect on the cheese-making process and cheese characteristics during ripening. Antibiotic-free milk was spiked individually with 7 veterinary drugs (amoxicillin, benzylpenicillin, cloxacillin, erythromycin, ciprofloxacin, enrofloxacin, and oxytetracycline) at an equivalent concentration of the European Union maximum residue limit. Spiked goat milk was used to make mature Tronchon cheeses, which were analyzed at 0, 30, and 60 d of maturation to determine pH, chemical composition, proteolytic and lipolytic activities, and color and textural properties. A sensory evaluation of 60-d ripened cheeses was carried out. Cheeses from raw antibiotic-free goat milk were made simultaneously to be used as reference. The cheese-making process was unaffected by the presence of most antibiotics evaluated. Only erythromycin and oxytetracycline significantly increased the time required for cheese production (122 +/- 29 and 108 +/- 25 min, respectively). However, variable amounts of antibiotics, ranging from 7.4 to 68%, were transferred from milk to cheese, with oxytetracycline and quinolones showing the highest retention rates. In general, antibiotic residues present in the cheeses at the beginning of maturation decrease significantly along time. Thus, beta-lactams and erythromycin residues were not detectable after 30 d of ripening. However, relatively high concentrations of enrofloxacin (148 +/- 12 mu g/kg) and ciprofloxacin (253 +/- 24 mu g/kg) residues were found in the cheeses after 60 d of maturation. The quality characteristics of the Tronchon cheeses were only slightly affected by such substances, with few significant differences in the free fatty acid concentration and color and textural properties of the cheeses. Results herein indicate that the use of goat milk containing antibiotics, such as quinolones, at the European Union maxim

[EN] Traces of antimicrobials in milk are of great concern for public health. The European Union has established maximum residue limits in milk; these, however, by themselves do not guarantee the absence of drug residues in milk and related products. Currently, very little information is available on the transfer of antibiotic residues from milk to other dairy products and their potential effect on food safety. This work evaluated the presence of antibiotic residues in pasteurized fluid milk and fresh cheeses from goat's milk containing these veterinary drugs at legal safety levels (maximum residue limits) and assessed the safety margin of these dairy products for consumers. Eight antibiotics (amoxicillin, benzylpenicillin, cloxacillin, neomycin, erythromycin, ciprofloxacin, enrofloxacin, and oxytetracycline) were selected, and three batches of fresh cheese were made from pasteurized goat's milk spiked with each of these drugs. Drug residues in milk and cheese samples were analyzed by liquid chromatography¿tandem mass spectrometry. The safety margin of goat's milk products was calculated taking into account different age groups (children, teenagers, and adults). Results showed that most antibiotics present in raw milk remained in pasteurized milk and were transferred to cheese to a high extent; retention was above 50% in most cases. The minimum safety margin in pasteurized milk was obtained for enrofloxacin, ciprofloxacin, and erythromycin for the children's group. For fresh cheese, an elevated safety margin was obtained for all antibiotics and age groups considered. However, the large amounts of antibiotics retained in the cheese might contribute to the development and spread of antimicrobial resistance. Considering the differences in milk from different species and the great variety of cheeses, it would be advisable to continue the traceability study of antibiotics in order to increase the safety margin of dairy products.

[ES] La mamitis es una enfermedad infecciosa que afecta al ganado caprino lechero y que puede ocasionar cambios físicos, químicos y generalmente bacteriológicos en la leche, así como una disminución en su producción. Uno de los principales agentes etiológicos de las mamitis caprinas es Staphylococcus aureus, el cual es importante, no solo por la gravedad de los cuadros clínicos que ocasiona en los animales, sino también por su capacidad de producir enterotoxinas termoestables que pueden estar presentes en la leche y productos derivados y causar intoxicaciones en los consumidores. Por ello, se ha planteado el presente trabajo con el objetivo de estudiar la presencia de este patógeno en la leche comercializada de las granjas caprinas de la Comunidad Valenciana, así como evaluar su efecto sobre la calidad de la leche cruda de cabra utilizada como materia prima en la industria quesera. Se analizaron un total de 120 muestras de leche de tanque procedentes de 40 explotaciones caprinas (12 en la provincia de Valencia, 18 en la de Castellón y 10 en la de Alicante; tres muestreos por explotación) para determinar su calidad comercial (composición química, recuento de gérmenes totales, recuento de células somáticas, punto de congelación y presencia de residuos de antibióticos) y la presencia de S. aureus. Los resultados obtenidos indican que la presencia de S. aureus en la leche de tanque es bastante frecuente. Este microorganismo se detectó, en al menos uno de los tres controles realizados, en el 60 % de las granjas estudiadas siendo mayor este porcentaje en la provincia de Castellón (77,8 %) que en las de Alicante (50 %) y Valencia (41,7 %). El análisis estadístico de los datos mostró diferencias significativas entre provincias para los parámetros de calidad higiénica considerados, pero no se pudo demostrar que la presencia de S. aureus tuviera un efecto negativo sobre la calidad comercial de la leche de cabra. En vista de estos resultados, sería recomendable la realización, [EN] Mastitis is an infectious disease affecting dairy goats, able to cause physical, chemical and generally bacteriological changes in milk, as well as a decrease in production. One of the main etiological agents of caprine mastitis is Staphylococcus aureus, which is important not only because of the severity of the clinical cases that it causes but also because of its ability to produce thermostable enterotoxins that could be present in milk and related products leading to food poisoning in consumers. Therefore, the aim of the present work was the study of the presence of this pathogen in marketed milk from goat farms of the Valencian Community, as well as the evaluation of its effect on the quality of the raw goat milk used in the cheese industry. A total of 120 samples of tank milk from 40 dairy goat farms (12 in the province of Valencia, 18 in Castellon and 10 in Alicante; three samplings per farm) were analyzed to determine their commercial quality (chemical composition, total germ count, somatic cell count, freezing point and presence of antibiotic residues) and the presence of S. aureus. The results obtained indicate that the presence of S. aureus in the bulk milk is quite frequent. This microorganism was detected, in at least one of the three controls carried out, in 60 % of the farms studied, being higher this percentage in the province of Castellon (77.8 %) than in Alicante (50 %) and Valencia (41.7 %). Statistical analysis of the data showed significant differences between provinces for the hygienic quality parameters considered, but could not prove that the presence of S. aureus had a negative effect on the commercial quality of the goat’s milk. In view of these results, further studies on the presence of this microorganism and its thermostable toxins in milk and derivatives would be advisable, as they could pose a risk factor for food safety., [CA] La mamitis és una malaltia infecciosa que afecta al ramat caprí lleter i que pot ocasionar canvis físics, químics i generalment bacteriològics en la llet, així com una disminució en la seua producció. Un dels principals agents etiológics de les mamitis caprines és Staphylococcus aureus, el qual és important, no sols per la gravetat dels quadros clínics que ocasiona en els animals, sinó també per la seua capacitat de produir enterotoxines termoestables que poden estar presents en la llet i productes derivats i causar intoxicacions en els consumidors. Per això, s'ha plantejat el present treball amb l'objectiu d'estudiar la presència d'este patogen en la llet comercialitzada de les granges caprines de la Comunitat Valenciana, així com avaluar el seu efecte sobre la qualitat de la llet crua de cabra utilitzada com a matèria primera en la indústria formatgera. Es van analitzar un total de 120 mostres de llet de tanc procedents de 40 granges caprines (12 a la província de València, 18 a la de Castelló i 10 a la d’Alacant; tres mostrejos per granja) per a determinar la seua qualitat comercial (composició química, recompte de gèrmens totals, recompte de cèl·lules somàtiques, punt de congelació i presència de residus d'antibiòtics) i la presència de S. aureus. Els resultats obtinguts indiquen que la presència de S. aureus en la llet de tanc és bastant freqüent. Aquest microorganisme s'ha detectat, en almenys un dels tres controls realitzats, en el 60 % de les explotacions estudiades sent major aquest percentatge a la província de Castelló (77,8 %) que a les d' Alacant (50 %) i València (41,7 %). L'anàlisi estadístic de les dades va mostrar diferències significatives entre províncies per als paràmetres de qualitat higiènica considerats, però no es va poder demostrar que la presència de S. aureus tinga un efecte negatiu sobre la qualitat comercial de la llet de cabra. Tenint en compte aquests resultats seria recomanable la realització de nous estudis sobre la presència d'

[EN] Two experiments were carried out to investigate how milking in mid-line (ML) affects the lipolysis level and milk composition in goat livestock, in comparison with low-line (LL) milking. The first experiment took place, in triplicate, on an experimental farm. For each replicate, a crossover design (62 goats, two treatments, ML and LL, in two periods each lasting 4 days) was used. Milk samples were taken daily at 0 and 24 h after milking. In the first experimental replicate, some enzymatic coagulation cheeses were made, which were assessed by a panel of tasters at 50 and 100 days of maturation. In the second experiment, the lipolysis level and composition of tank milk from 55 commercial dairy goat farms (25 ML and 30 LL) were analysed, in milk samples taken in three different weeks. The results of the first experiment showed that ML milking increased free fatty acid (FFA) concentration in raw goat's milk significantly (0.71 v. 0.40 mmol/l, respectively). However, in the milk samples taken from commercial farms the FFA concentration remained unaffected by the milking pipeline height (0.59 v. 0.58 mmol/l for ML and LL, respectively). No significant differences were found in the milk composition, nor in the sensory characteristics in the cured cheeses, which suggests that factors other than the milkline height are able to influence the level of lipolysis under commercial conditions. Therefore, ML milking should not be discouraged, provided that the correct functioning and management of the milking operation and milk storage on the farm is guaranteed.

[EN] The limited availability of drugs registered for dairy goats makes veterinarians prescribe off-label treatments with a legally established minimum safety period of seven days. The aim of this work was to verify if the exceptional use of macrolide antibiotics in dairy goats generates residues in milk and cheeses within that period. Hence, three macrolide drugs (erythromycin, tylosin and spiramycin) were administred in an in vivo experiment in dairy goats. Ripened cheeses were made from bulk milk obtained before drug administration, 24¿h after treatment, and at the end of the recommended withdrawal period. Residual amounts of erythromycin (234.9¿±¿52.7¿¿g/kg), tylosin (198.7¿±¿57.8¿¿g/kg) and spiramycin (1539.8¿±¿469.4¿¿g/kg), widely exceeding their legal maximum residue limits (MRLs) established, were detected in milk collected 24¿h after treatment, making the cheese production in most cases impossible. After the seven-day period, only spiramycin was detected in goat¿s milk (79.6¿±¿19.2¿¿g/kg) although no antibiotic residues were found in the cheeses. A withdrawal time of seven days seems suitable to guarantee milk safety after the administration of erythromycin and tylosin without any negative effects neither on the milk nor on the and cheese properties. However, given the rapid elimination of these substances, a shorter withdrawal period might be considered. For spiramycin, persisting in milk for a longer period, further studies on its pharmacokinetics in dairy goats would be recommendable to avoid a potential risk to consumer health.

[EN] The effectiveness of applying chitosan coatings containing rosemary and oregano essential oils to cheeses was analysed. Cheeses were coated by immersing the samples two or three times successively in the different formulations. The ripening indexes, water loss, fungal growth and sensory properties of the coated and noncoated cheeses throughout ripening were evaluated. The coatings both prevented weight loss and improved the microbial safety. The lipolytic and proteolytic activities were reduced in coated cheese, which is in line with the antimicrobial effect of active coatings. Sensory evaluation revealed that the cheeses double-coated with chitosan oregano oil were the best evaluated in terms of aroma and flavour.

[EN] Three batches of yoghurts were made from goat s milk with different enrofloxacin concentrations (0, 50, 100 and 150 lg/kg). Quality parameters were analysed at 1, 7, 14 and 28 days at 5 °C. Drug residues were also quantified by HPLC. Coagulation time and most yoghurt properties remained unaffected by the presence of enrofloxacin in goat s milk. However, quality parameters were affected by the storage period. 74.9 99.2% of enrofloxacin initially added to goat s milk remained in the yoghurt throughout its entire shelf life, potentially posing a risk to consumer health. Therefore, an enrofloxacin maximum residue limit in yoghurt should be established.

[EN] Raw goat milk spiked with antibiotics was coagulated with rennet, the whey separated and the transfer of 18 antibiotics from the milk to the whey was evaluated by estimating antimicrobial activity of the whey using microbial inhibitor tests. Antibiotic-free whey (negative whey) spiked with different antibiotics was used as a reference. The antimicrobial activity in whey from milk spiked with most b-lactam drugs was lower (0e40%) than that of the reference whey, suggesting that these antibiotics are mostly released from curd and transferred to the whey. However, for most non-b-lactam drugs, an 84e100% reduction in the relative antimicrobial activity in whey was obtained, indicating the higher susceptibility for retention in curd. The traceability of antibiotics through the cheese-making process will make it possible to determine whether control systems are required to prevent the negative implications of the presence of antibiotic drug residues in cheese and whey products.

[EN] Albendazole (ABZ) residues in goat's milk and their effect on the response of microbial inhibitor tests used for screening antibiotics were evaluated. A total of 18 Murciano-Granadina goats were treated with ABZ and individually milked once a day over a 7-day period. ABZ quantification was performed by high performance liquid chromatography. The ABZ parent drug was not detected. The maximum concentration of its metabolites (ABZ sulfoxide, ABZ sulfone, and ABZ 2-aminosulfone) was reached on the 1st day posttreatment (260.0 ± 70.1 mg/kg, 112.8 ± 28.7 mg/kg, 152.0 ± 23.6 mg/kg, respectively), decreasing to lower than the maximum residue limit (MRL, 100 mg/kg) on the 3rd day post treatment. Milk samples were also analyzed by microbial tests [Brilliant Black Reduction Test (BRT) MRL, Delvotest SP-NT MCS and Eclipse 100], and only one positive result was found for Delvotest SP-NT MCS and Eclipse 100. However, a high occurrence of positive outcomes was obtained for BRT MRL during 6 days post treatment, whereas ABZ residues were not detected from the 4th day post administration, suggesting that factors other than the antiparasitic agent might affect the microbial test response.

[EN] The aim of this study was to determine whether the prophylactic use of antibiotics in intravaginal sponges used for estrus synchronization in goats may result in the presence of inhibitors in milk and, therefore, of positive results by microbial screening tests. Ninetyeight Murciano-Granadina goats were used, divided into 7 groups of 14 animals. Intravaginal sponges were placed in 6 groups using 2 concentrations of 3 different antibiotics: doxycycline, oxytetracycline, and sulfathiazole- framycetin. The sponges of the control group were placed without antibiotics. Milk samples were collected daily until 7 d posttreatment and analyzed using 3 microbial tests. Positive samples were retested by specific receptor-binding assays to confirm the positive results. Vaginal status was evaluated by visual assessment of the external aspect of the sponges after removal. The microbial test response was not affected by either day posttreatment or dose of antibiotic used, except for oxytetracycline at the higher concentration. Moreover, no positive results were obtained using receptor-binding assays, suggesting that residues, if present in milk, did not exceed the regulatory (safety) levels established for these drugs. The occurrence of soiled sponges was higher in the control group. With respect to the dose of antibiotics used, no significant differences were found for the lower dose administered. However, a significant increase in the percentage of clean sponges was observed for the higher dose of doxycycline. We conclude that the prophylactic use of low doses of doxycycline, oxytetracycline, or sulfathiazole in intravaginal sponges used for synchronization of estrus helps to reduce clinical vaginitis in dairy goats and does not seem to be the cause of positive results in microbial inhibitor tests used to detect antibiotics in goat milk.

[ES] La utilización de antibióticos para el tratamiento de la mamitis y otras enfermedades de tipo infeccioso en ganado caprino lechero es una práctica generalizada actualmente. Sin embargo, la escasa disponibilidad de medicamentos registrados para esta especie hace que en muchas ocasiones, los veterinarios se vean obligados a aplicar los tratamientos de forma “extra-label”, lo que incrementa el riesgo de la presencia de residuos de antibióticos en la leche y sus derivados. El objetivo de este trabajo es verificar si el uso “extra-label” de antibióticos macrólidos en caprino lechero puede generar residuos en la leche y afectar la seguridad de productos derivados como el queso. Para ello se seleccionó un macrólido de uso habitual en caprino lechero, la tilosina, y se planteó la realización de un experimento in vivo que simulara las condiciones de su aplicación a nivel de campo y el aprovechamiento industrial de la leche procedente de los animales tratados, para la obtención de queso curado tipo Tronchón. El antibiótico residual en la leche y el queso de cabra, fue determinado por HPLC. También se realizaron análisis de tipo fisicoquímico sobre el queso a diferentes tiempos de maduración, con objeto de identificar posibles defectos de fabricación asociados con la utilización de la leche procedente de este tipo de tratamientos. La leche de cabra ordeñada tras la administración del antibiótico, presentó una concentración residual de tilosina de 198,7±57,8 µg/kg, valor muy superior al LMR establecido en la legislación para esta sustancia (50 µg/kg). Además, los quesos obtenidos a partir de esta leche, presentaron una concentración relativamente elevada de antibiótico residual a lo largo de todo el periodo de maduración (día 1: 178,9±3,3 µg/kg; día 30: 140,9±11 µg/kg; día 60: 86,85±4,74 µg/kg), así como algunas alteraciones de su calidad, principalmente relacionadas con la textura y grado de proteólisis alcanzado durante la fase de curado. Por el contrario, tras el period, [EN] The use of antibiotics in the treatment of mastitis and other infectious diseases in dairy goats is a widespread practice nowadays. However, the limited availability of drugs registered for this species is forcing veterinarians to employ the off-label treatments increasing the risk of drug residues in milk and dairy products. The aim of this work is to verify if the off-label use of the macrolide antibiotics in dairy goats can generate residues in milk affecting the safety of related products such as cheeses. For this, a macrolide drug routinely applied in dairy goats (tylosin) was selected, and the realization of an in vivo experiment that simulates the treatments done in practice as well as the industrial processing of milk from treated goats to obtain Tronchón ripened cheese was planned. Residuals amounts of antibiotics in milk and cheese were assessed by HPLC analysis. Physicochemical analysis on cheeses was also included in order to identify potential technological failures related to the use of milk from these types of veterinary treatments. After drug administration, milked goat’s milk presented a residual concentration of tylosin of 198,7±57, 8 µg/kg, exceeding the MRL legally established for this substance (50µg/kg). In addition, cheeses made from this milk, presented a relatively high concentration of antibiotic residues, throughout the period of maturation (day 1: 178, 9±3, 3 µg/kg; day 30: 140, 9±11 µg/kg; day 60: 86, 85±4, 74 µg/kg), as well as some alterations of their quality mainly related to the texture and degree of proteolysis reached during ripening. On the contrary, after withdrawal period, tylosin residues in goat's milk (10 µg / kg) were lower than the MRL established, and detectable residues was not generated in cheeses after milk processing. However, although results herein indicate that the off-label use of tylosin, in the conditions described in this work, generate a relatively low concentration of antibiotic residues in goat's milk

[EN] Cleaning and disinfection of dairy equipment is essential to ensure the hygienic quality of milk. Occasionally, some farmers use washing-up liquids and disinfectants for home use, especially when cleaning procedures are carried out manually. Residues of detergents and disinfectants in milk may interfere with the response of microbial inhibitor tests used for screening antibiotics in milk. Therefore, the aim of this study was to evaluate the interference of non-specific detergents in screening tests (BRT MRL; Delvotest SP-NT MCS; Eclipse 100) for goat s milk. Twelve replicates of eight concentrations of five washing-up liquids (0 1%) and one disinfectant (0 1%) were analysed. The results showed that the presence of washing-up liquids at concentrations of ≥1 ml/l leads to positive results in microbial tests. In particular, the product containing sodium laureth sulphate and ethanol produced the largest number of positive outcomes. The presence of disinfectant based on sodium hypochlorite did not affect the test response. The detection capabilities of microbial inhibitor tests for penicillins were also studied in milk with and without cleaning products, calculating the dose response curve with eight concentrations of amoxicillin, ampicillin, benzylpenicillin and cloxacillin, respectively. The detection limits of the screening tests for penicillins were not modified substantially by the cleaning product based on sodium laureth sulphate and ethanol. Residues of cleaning agents in milk can be avoided when specific detergents and disinfectants for milking equipment are used and good cleaning practices are applied.

[EN] The detection capability (CC beta) of some microbial screening tests currently available was calculated for sheep and goat milk in accordance with Commission Decision 657/2002/EC. The CC beta was at or below the maximum residue limit (MRL) for most beta-lactams assessed and other non-beta-lactam drugs such as neomycin, tylosin, sulfadiazine and sulfadimethoxine. However, the tests were less sensitive in the detection of most non-beta-lactam drugs such as quinolones and tetracyclines at safety levels. When individual sheep milk samples free of antibiotics were analysed, an elevated somatic cell count was related to the occurrence of non-compliant results in all the methods assessed. To guarantee the safety of milk and dairy products from small ruminants, the periodical implementation of screening tests more sensitive towards non-beta-lactam drugs would be appropriate. (C) 2014 Elsevier Ltd. All rights reserved.

Microbial inhibitor tests are widely used to screen antibiotic residues in milk; however, these tests are nonspecific and may be affected by various substances capable of inhibiting the growth of the test microorganism. The objective of this study was to determine the effect of antiparasitic drugs in goat s milk on the microbial inhibitor test response. Raw antibiotic-free milk from Murciano-Granadina goats was supplemented with eight concentrations of seven antiparasitic substances (albendazole, 10 to 170 mg/kg; closantel, 1 to 140 mg/kg; diclazuril, 8 to 45 mg/kg; febendazole, 10 to 140 mg/kg; levamisole, 40 to 440 mg/kg; diazinon, 8 to 45 mg/kg; and ivermectin, 40 to 200 mg/kg). Twelve replicates for each concentration were analyzed with three microbial inhibitor tests: BRT MRL, Delvotest SP-NT MSC, and Eclipse 100. The results were interpreted visually (negative or positive). Using a logistic regression model, the concentrations of the antiparasitic drugs producing 5% (IC5), 10% (IC10), and 50% (IC50) positive results were determined. In general, the Eclipse 100 test was less sensitive to the effect of antiparasitic substances; the inhibitory concentrations of almost all the drugs assayed were higher than those for other tests. Conversely, the BRT MRL test was most affected, with high levels of interference at lower antiparasitic drug concentrations. Closantel and diazinon interfered with all microbial tests at lower concentrations than did other drugs (IC5 ~ 1 to 26 and 12 to 20 mg/kg, respectively), and higher concentrations of levamisole and diclazuril (IC5 ~ 30 to 240 and 50 to 117 mg/kg, respectively) were required to produce 5% positive results. These findings indicate that microbial inhibitor tests can be affected by elevated concentrations of antiparasitic drugs in goat s milk.

Tesis por compendio, Goat milk is primarily destined for the production of fermented products, in particular cheese. Therefore, the control of antibiotic residues in milk is of great importance, since these could have negative repercussions on technological properties of the milk as well as on the health of consumers. In milk quality control programs, microbial inhibitor tests are widely applied to detect antibiotics during the screening stage. However, tests are non-specific and may be affected by substances other than antimicrobials which could inhibit the growth of the test micro-organism, causing false positive results. The aim of this thesis was to evaluate the interference, related to the presence of different contaminants in goat milk, on the response of microbial inhibitor tests commonly used in Spain to detect antibiotics (BRT MRL, Delvotest SP-NT MCS and Eclipse 100 tests). The influence of the physicochemical characteristics of goat milk on the false positive outcomes in microbial screening tests was also investigated. The suitability of microbial inhibitor tests for screening antibiotics in colostrum secretions was studied by analysing antibiotic-free colostrum and milk samples from forty-three Murciano-Granadina goats, collected every 12 hours during the first week post-partum. Microbial inhibitor tests were not suitable for the analysis of goat colostrum because they presented a high percentage of doubtful and positive results (up 37.2% in the 36 hours after partum). To evaluate the effect of caprine colostrum on the microbial test response, antimicrobial-free goat milk spiked with different concentrations of colostrum was analysed to calculate the inhibitory concentrations producing 5% of positive results. The highest interferences were obtained for the addition of colostrum from 12 to 24 hours post-partum and the colostrum concentrations producing 5% positive results were between 5.1 and 34.6%. The BRT MRL was the test the most affected. In another study, the interferenc

© INIA. Manuscripts published are the property of the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria SJAR is an Open Access Journal. All articles are distributed under the terms of the Creative Commons Attribution License (CC by-nc/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., [EN] The use of antibiotics to treat mastitis and other infectious diseases in dairy sheep and goats is a widespread practice nowadays that can, when not properly applied, result in the contamination of the milk supply. Spanish legislation establishes the control of the presence of antibiotic residues in sheep and goat s milk using screening methods that detect, at least, beta-lactam drugs. Microbial inhibitor tests using Geobacillus stearothermophilus var. calidolactis and specific receptor-binding assays are most widely employed for this purpose. The detection rates of screening tests routinely used in Spain have been calculated considering the frequency of use of veterinary drugs commonly applied in ovine and caprine livestock to treat and prevent mastitis as well as the test sensitivity toward these substances at safety levels. In general, the use of a single test allows detecting 62.8-82.4% of the antibiotics employed. For sheep milk, the total detection range achieved with microbial tests was significantly higher than that reached with rapid receptor tests. However, no significant differences between the two types of methods were found when goat s milk was analysed. In both types of milk, the simultaneous use of two screening tests with a different analytical basis increases the total detection range significantly,reaching values ≥ 90% in some cases (81.5-90.1% for sheep and 84.7-92.6% for goats). However, the periodical use of screening tests able to detect quinolones, macrolides or aminoglycosides would be recommended to carry out more efficient screening and ensure the safety of milk and dairy products from sheep and goats.

Receptor-binding assays to detect antibiotics in sheep milk were evaluated. Specificity of the Betastar Combo, SNAP and Twinsensor(BT) tests was optimal using inhibitor-free bulk sheep milk (99-100%), and no differences between the visual or instrumental classification were found. For individual sheep milk free of antibiotics, specificity was elevated by the Betastar Combo and SNAP tests. However, lower specificity was obtained by the TwinsensorBT test, especially in the last weeks of the lactation period. Regarding cross-reactions, interferences related to drugs other than beta-lactams and tetracyclines were not detected. Furthermore, the use of azidiol, as a preservative of milk, had no effect on the test. In all cases, the detection capability was able to detect most b-lactams and tetracyclines at or below maximum residues limits. The receptor-binding tests evaluated showed a very good performance in the detection of antibiotics in sheep milk, thus being suitable for milk quality control programmes

The suitability of different receptor-binding assays to detect antibiotics in raw goat's milk was investigated. Detection capability of most beta-lactams and tetracyclines assessed applying the Betastar Combo, the SNAP Betalactam, the SNAP Tetracycline, and the Twinsensor tests was at or below maximum residue limits established by European legislation. Regarding test specificity, cross-reactions with antibiotics other than beta-lactams and tetracyclines were not found, and no false-positive results were obtained for the Betastar Combo and the SNAP tests when bulk samples of goat's milk were analyzed. For the Twinsensor test, the false-positive rate was 1%. The performance of the Betastar Combo and the SNAP tests was practically unaffected by the milk quality parameters using individual samples of goat's milk collected at points throughout the entire lactation period (false-positive rate, <= 5%). However, a larger number of positive results were obtained by the Twinsensor test in this type of milk sample (>10%), especially in the last weeks of lactation. Interferences related to the use of the preservative azidiol were not observed in any case. Neither were any significant differences found in relation to the interpretation method (visual versus instrumental) applied. In general, the response of the Betastar Combo, SNAP, and Twinsensor tests was optimal for the analysis of bulk caprine milk; thus, they may be used to monitor milk for the presence of beta-lactam and tetracycline residues in quality control programs.

[EN] The aim of this work was to study the response of microbial tests used for the detection of antibiotics in colostrum and in colostrum-containing goats' milk. For this purpose, colostrum and milk samples were collected from 43 Murciano-Granadina goats every 12 h during the first 7 days of lactation. All samples were analysed by the microbial inhibitor tests BRT MRL, Delvotest SP-NT MCS and Eclipse 100. The results show that the tests were not suitable for the analysis of goat colostrum because they presented a high percentage of doubtful and positive results for samples of the first 24h post-partum. Only the Delvotest SP-NT MCS could be used successfully for samples from 36 h post-partum onwards, as it shows a very high specificity, while this was not obtained for BRT MRL and Eclipse 100 until 96 h post-partum. According to the logistic regression model, the occurrence of noncompliant results for these screening tests is mainly related to the high protein content of colostral secretions. Furthermore, to study the influence of the presence of colostrum on goats' milk, antibiotic and colostrum-free farm tank milk was used, to which different concentrations (n = 12) of colostrum obtained at different time points (12, 24,36 and 48 h) were added. Positive results appeared in BRT MRL for milk mixed with relatively low concentrations of colostrum collected at 12-24h post-partum (7.5-10%, respectively), while in the Delvotest SP-NT MCS and Eclipse 100 non-compliant results only occurred for milk with high concentrations (>= 35%) of colostrum for both time points. Moreover, high concentrations >= 20% of colostrum from 36 to 48 h are needed to affect the BRT MRL. Low concentrations of colostrum in milk that may cause non-compliant results can be avoided if good farming practices of identification and separation of goats at the beginning of lactation are respected. (C) 2014 Elsevier B.V. All rights reserved.

[EN] The aim of the study was to evaluate the interference of acid and alkaline detergents employed in the cleaning of milking equipment of caprine dairy farms on the performance of microbial tests used in antibiotic control (BRT MRL, Delvotest MCS, and Eclipse 100). Eight concentrations of commercial detergents, five acid (0-0.25%) and five alkaline (0-1%) were add to antimicrobial-free goat's milk to evaluate the detergent effect on the response of microbial inhibitor tests. To evaluate the effect of detergents on the detection capability of microbial tests two detergents at 0.5ml/l (one acid and one basic) and eight concentrations of four beta-lactam antibiotics (ampicillin, amoxicillin, cloxacillin and benzylpenicillin) were used. Milk without detergents was used as control. The spiked samples were analysed twelve times by three microbial tests. The results showed that the presence of acid detergents did not affect the response of microbial tests for any of the concentrations tested. However, at concentrations equal to or greater than 2ml/l alkaline detergents positive results were found in microbial tests (16.7-100%). The detection limits of the screening tests for penicillins were not modified substantially by the presence of detergents. In general, the presence of acid and alkaline detergents in goat's milk did not produce a great interference in the microbial tests, only high concentrations of detergents could cause non-compliant results, but these concentrations are difficult to find in practice if proper cleaning procedures are applied in goat dairy farms.

The Charm maximum residue limit P-lactam and tetracycline test (Charm MRL BLTET; Charm Sciences Inc., Lawrence, MA) is an immunoreceptor assay utilizing Rapid. One-Step Assay lateral flow technology that detects P-lactam or tetracycline drugs in raw commingled cow milk at or below European Union maximum residue levels (EU-MRL). The Charm MRL BLTET test procedure was recently modified (dilution in buffer and longer incubation) by the manufacturers to be used with raw ewe and goat milk. To assess the Charm MRL BLTET test for the detection of beta-lactams and tetracyclines in milk of small ruminants, an evaluation study was performed at Instituto de Ciencia y Tecnologia Animal of Universitat Politecnica de Valencia (Spain). The test specificity and detection capability (CC beta) were studied following Commission Decision 2002/657/EC. Specificity results obtained in this study were optimal for individual milk free of antimicrobials from ewes (99.2% for beta-lactams and 100% for tetracyclines) and goats (97.9% for beta-lactams and 100% for tetracyclines) along the entire lactation period regardless of whether the results were visually or instrumentally interpreted. Moreover, no positive results were obtained when a relatively high concentration of different substances belonging to antimicrobial families other than beta-lactams and tetracyclines were present in ewe and goat milk. For both types of milk, the CC beta calculated was lower or equal to EU-MRL for amoxicillin (4 mu g/kg), ampicillin (4 mu g/kg), benzylpenicillin (<= 2 mu g/kg), dicloxacillin (30 mu g/kg), oxacillin (30 mu g/kg), cefacetrile (<= 63 mu g/kg), cefalonium (<= 10 mu g/kg), cefapirin (<= 30 mu g/kg), desacetylcefapirin (<= 30 mu g/kg), cefazolin (<= 25 mu g/kg), cefoperazone (<= 25 mu g/kg), cefquinome (20 mu g/kg), ceftiofur (<= 50 mu g/kg), desfuroylceftiofur (<= 50 mu g/kg), and cephalexin (<= 50 mu g/kg). However, this test could neither detect cloxacillin nor nafcillin at or below EU-MRL (CC bet

The quality of colostrum of Murciano-Granadina goats was studied to establish the transition period and the time when milk can be marketed. Forty-three dairy goats were used: 19 primiparous (15 single births; 4 multiple births) and 24 multiparous (10 single births; 14 multiple births). Samples were collected every 12 h during the first week postpartum. Physicochemical parameters and somatic cell count were determined. Analysis of variance with repeated measures was used to study the effect of different factors: postpartum time, litter size, lactation number, their interactions, and production level on colostrum. Postpartum time had a significant effect on all parameters studied, which decreased along the first week of lactation, whereas lactose, pH, and conductivity increased. Based on these results, colostrum secretion takes place until 36 h postpartum (hpp). In relation to other factors of variation studied, the lactation number influenced most colostrum components, whereas the litter size only affected the pH value, protein and lactose content. The production level influenced only the protein and dry matter contents, with an inverse relationship. Milk produced during the period between 36 and 96 hpp is considered transition milk, which should not be commercialized. Milk collected after 4 d postpartum (96 hpp) could be marketed, ensuring that its composition does not present a risk in the dairy industry.

[ES] Se realizó la evaluación de los métodos de unión a receptores proteicos BetaStar Combo, Charm MRL BL/TET, SNAP (Betalactam, Tetracycline y Gentamicin) y TwinsensorBT en leche cruda de cabra.Se calculó la especificidad y Capacidad de Detección (CCß) para antibióticos betalactámicos y tetraciclinas También se estudió el efecto del conservante azidiol., [EN] In this study was carried out the evaluation of the methods BetaStar Combo, Charm MRL BL/TET, SNAP (Betalactam, Tetracycline y Gentamicin) y TwinsensorBT in goat raw milk. We calculate the specificity and the Detection Capability (CCß) for betalactam antibiotics and tetraciclines. We also determinate the effect of the perservative azidiol.

[EN] This article presents a microbiological system composed of a " BT" bioassay (Beta-lactams and Tetracyclines) and a " QS" bioassay (Quinolones and Sulfonamides). The " BT" bioassay contains spores of Geobacillus stearothermophilus, bromocresol purple and cloramphenicol in a culture medium (incubation time: 2.45h), while the " QS" bioassay uses spores of Bacillus subtilis, trifenyltetrazolium - toluidine blue and trimethoprim in a suitable culture medium (incubation time: 5.5h). The detection capability (CC ß) of 27 antimicrobial agents in ovine milk were determined by logistic regression models. Thus, the " BT" bioassay detects amoxycillin, ampicillin, penicillin " G" , cloxacillin, oxacillin, cephalexin, cefoperazone, ceftiofur, chlortetracycline, oxytetracycline, tetracycline, neomycin, gentamycin and tylosin, while " QS" bioassay detects: ciprofloxacin, enrofloxacin, marbofloxacin, sulfadiazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfathiazole, erythromycin, lincomycin and spiramycin at levels close to their respective Maximum Residue Limits. The simultaneous use of both bioassays detects a large number of antibiotics in milk given each method's adequate complementary sensitivity. © 2011 Elsevier B.V..

El objetivo de este estudio ha sido evaluar la influencia de la presencia de calostro en la leche de oveja sobre los métodos microbiológicos de detección de antibióticos, a fín de comprobar si la presencia de esta sustancia puede dar lugar a la aparición de resultados positivos o "no conformes" en estos métodos.