The quality of colostrum of Murciano-Granadina goats was studied to establish the 27 transition period and the time when milk can be marketed. Forty-three dairy goats were 28 used, 19 primiparous (15 single births; 4 multiple births) and 24 multiparous (10 single 29 births; 14 multiple births). Samples were collected every 12 h during the first week 30 postpartum. Physico-chemical parameters and somatic cell count were determined. 31Analysis of variance with repeated measures was used to study the effect of different 32 factors: postpartum time, litter size, lactation number, their interactions and production 33 level on colostrum. 34 Postpartum time had a significant effect on all parameters studied, which decreased 35 along the first week of lactation, while lactose, pH and conductivity increased. Based on 36 these results, colostrum secretion takes place until 36 hours postpartum (hpp). In 37 relation to other factors of variation studied, the lactation number influenced (P <0.05) 38 most colostrum components, while the litter size only affected (P <0.05) the pH value, 39 protein and lactose content. The production level influenced only the protein and dry 40 matter contents, with an inverse relationship. Milk produced during the period between 41 36 and 96 hpp is considered transition milk, which should not be commercialized. After 42 4 days postpartum (96 hpp) milk could be marketed, ensuring that composition does not 43 present a risk in the dairy industry. 44
The presence of drug residues in ewe's milk samples can be determined by microbial assays. The main limitation of these tests is the large number of false-positive results associated with them. False-positive results can be explained by the interaction of certain substances naturally existing in ewe's milk with the growth of the microorganism used in the test. In this study, milk chemical composition (fat, protein, lactose, total solids), somatic cell counts (SCCs), free fatty acid concentrations, and lactoperoxidase system components were determined in order to investigate their influence on the rate of false-positive results for the BRT and Delvotest microbiological inhibitor tests. Milk samples were obtained after morning milking of Manchega ewes at 15, 30, 45, 60, 75, 90, 105, 120, and 135 days after parturition. The animals did not receive any kind of treatment or medicated feed throughout the experiment. The false-positive rates for BRT and Delvotest were 3.75 and 2.4%, respectively. When the logistic regression model was applied, the percentages of total solids for positive samples were significantly different from those for negative samples (16.90 versus 18.42% for BRT, 16.05 versus 18.45% for Delvotest), while the SCC logarithmic transformation was significantly higher for the positive samples than for the negative samples (5.38 versus 5.11 log units for BRT, 5.32 versus 5.11 log units for Delvotest). Moreover, Delvotest-positive samples exhibited thiocyanate concentrations higher than those of Delvotest-negative samples (8.18 mg/liter versus 6.85 mg/liter). Further analyses are needed to confirm the possible presence of antimicrobial residues in this particular type of milk sample.
This article presents a microbiological system composed of a "BT" bioassay (Beta-8 lactams and Tetracyclines) and a "QS" bioassay (Quinolones and Sulfonamides). The 9 "BT" bioassay contains spores of Geobacillus stearothermophilus, bromocresol purple 10 and cloramphenicol in a culture medium (incubation time: 2.45 h), while the "QS" 11 bioassay uses spores of Bacillus subtilis, trifenyltetrazolium -toluidine blue and 12 trimethoprim in a suitable culture medium (incubation time: 5.5 h). The detection 13 capability (CC β ) of 27 antimicrobial agents in ovine milk were determined by logistic 14 regression models. Thus, the "BT" bioassay detects amoxycillin, ampicillin, penicillin 15 "G", cloxacillin, oxacillin, cephalexin, cefoperazone, ceftiofur, chlortetracycline, 16 oxytetracycline, tetracycline, neomycin, gentamicin and tylosin, while "QS" bioassay 17 detects: ciprofloxacin, enrofloxacin, marbofloxacin, sulfadiazine, sulfadimethoxine, 18 sulfamerazine, sulfamethazine, sulfamethoxazole, sulfathiazole, erythromycin, 19 lincomycin and spiramycin at levels close to their respective Maximum Residue Limits. 20The simultaneous use of both bioassays detects a large number of antibiotics in milk 21given each method's adequate complementary sensitivity. 22
The effects of vacuum level and overmilking on udder health were studied in ewes. Vacuum levels of 36 and 42 kPa were assigned to two groups of 23 Manchega ewes in a crossover study design with two experimental periods of 5 wk for each. Moreover, for each ewe, one teat was overmilked 1.5 to 2 min at all milkings during these 10 wk. The milking machine used had a midlevel milkline and pulsation was fixed at 180 cycles per min and a pulsation ratio of 50:50. Bacterial exposure of all teats was increased by dipping them in a suspension of Staphylococcus simulans at eight milkings of each period. New intramammary infections (IMI) were not significantly affected by the vacuum level used (18 and 23% of ewes infected, at 36 and 42 kPa, respectively) or application of overmilking (9 and 11% of half udders infected without and with overmilking, respectively). Likewise, neither factor significantly affected the somatic cell count (SCC) of the milk. Teat thickness changes after milking varied significantly due to the presence of overmilking (-13.6 and -7.4%, in teats not overmilked and overmilked, respectively) but were not affected by vacuum level. At no time were any lesions or variations visibly noted in the teat walls or orifice. So, in this work we were unable to demonstrate that the vacuum and overmilking levels assayed, both used with a pulsation rate of 180 cycles/min, have an important effect on the state of udder health in the short term. Furthermore, it was also observed that, in absence of IMI, the two factors studied did not cause irritation of any kind in the gland that might influence the SCC of the milk.
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