Intramammary antibiotics in dairy goats : withdrawal periods and tissue tolerance

Abstract

The aim of this study was to determine withdrawal periods and tissue tolerance of intramammary antibiotics (Curaclox LC, Spectrazol Milking Cow and Rilexine 200 LC) in goats, measured in different ways, and to evaluate the effects of related factors. Method: Three experimental trials were conducted. Trial 1 and Trial 2 were conducted at the Faculty of Veterinary Science, Onderstepoort using the goat herd of the Onderstepoort Teaching Animal Unit (OTAU) (Herd A), while Trial 3 was conducted on a commercial goat dairy in the Limpopo Province of South Africa (Herd B). In addition, four goats with clinical mastitis from a smallholding close to the Faculty of Veterinary Science at Onderstepoort were studied (Herd C). This herd consisted of 13 lactating Saanen and Saanen/Toggenburg crossbred dairy goats. In all trials foremilk was stripped, teats were disinfected and a milk sample was taken from each udder half of each goat (half-milk samples). In all three trials the following milk samples were taken: two sets of half samples and a composite sample (before, during and after treatment). The California Milk Cell Test (CMCT) and conductivity measurements were performed. In Trial 3 the conductivity meter became non-functional on the second day, and thus the conductivity test was eliminated from then on. Each udder half was milked separately and milk volume was recorded. The temperature of goats was taken and recorded to identify sick animals. All goats in the treatment group were treated. In all three trials after treatment, sampling continued until SCC returned to baseline and until there were at least two consecutive negative TRIS tests for each goat, approximately 10 days. Milk production was based on the following milk production groups: low (less than 1.3L), medium (1.3L to 1.5L) and high (greater than 1.5L) daily milk production. The antibiotics used in these trials were selected for being commonly used, broad-spectrum preparations. Trial 1, a semi-synthetic penicillin based intramammary preparation (Curaclox LC, which contains 75mg sodium ampicillin and 200mg sodium cloxacillin per dose plus blue dye). Curaclox LC G2615, (Norbrook (Pharmacia AH) P.O. Box 10698 Centurion, 0046), cloxacillin 200mg, ampicillin 75mg, blue dye/ 4.5g syringe. Trial 2, a cefuroxime 250mg based intramammary product (Spectrazol Milking Cow, Schering-Plough). Spectrazol milking cow, cefuroxime, 250mg, S4 Intramammary Injection 83/594, (Schering-Plough Animal Health, P.O. BOX 46, Isando, 1600). Trial 3, a cephalexin 100mg, neomycin sulphate 100mg and prednisolone based intramammary product, Rilexine (SA) 200LC injection 83/638, (Logos Agvet (Virbac), Private bag X115, Halfway House, 1685). Curaclox LC G2615, Norbrook (Pharmacia AH), cloxacillin 200mg, ampicillin 75mg, blue dye/ 4.5g syringes. In the clinical mastitis cases (Herd C); Goat 1 was treated with Spectrazol milking cow (as above), Goat 2 was treated with Curaclox LC (as above), Goat 3 was treated with Curaclox LC in the left udder half and Goat 4 was treated with Curaclox LC in the right udder half (as above). Results: Trial 1: Curaclox LC The mean withdrawal periods for the product Curaclox LC (intramammary) as measured by Thermo Resistant Inhibitory Substances (TRIS), colour dye, Parallux testing for cloxacillin and ampicillin, on eight relatively low producing Saanen dairy goats (Trial 1) were 74h ± 19.21; 90h ± 16.97; 99h ± 9.07 and 93h ± 11.41 respectively. The withdrawal period for Curaclox LC recommended for use in cattle (72h) was significantly shorter than the withdrawal periods as measured by colour dye (P < 0.001), Parallux testing for cloxacillin (P < 0.001) and Parallux testing for ampicillin (P < 0.05) in Trial 1. There was a significant difference of withdrawal periods as measured by TRIS (P < 0.05) and colour dye (P < 0.05) between goats with and without clinical mastitis in Trial 1 Trial 3: Curaclox LC The mean withdrawal periods for Curaclox LC as measured by TRIS, colour dye, Parallux testing for cloxacillin and ampicillin, on 12 relatively high producing Saanen and Saanen-Toggenburg crossbreed dairy goats (Trial 3) were 42h ± 7.08; 65h ± 60.26; 77h ± 13.56 and 71h ± 12.65 respectively. The withdrawal period for Curaclox LC recommended for use in cattle (72h) was significantly longer than the withdrawal periods as measured by TRIS (P < 0.001) and colour dye (P < 0.001) in Trial 3. Curaclox LC: Trials 1&3 combined The mean withdrawal periods for Curaclox LC as measured by TRIS, colour dye, Parallux testing for cloxacillin and ampicillin, for Trials 1&3 combined were 59h ± 24.31; 76h ± 17.70; 87h ± 16.10 and 80h ± 16.23 respectively. The withdrawal period for Curaclox LC recommended for use in cattle (72h) was significantly longer than the withdrawal periods as measured by TRIS (P < 0.001) in Trials 1&3 combined. Trial 2: Spectrazol Milking Cow The mean withdrawal periods for Spectrazol Milking Cow (intramammary) as measured by TRIS on seven relatively low producing Saanen dairy goats (Trial 2) was 95h ± 17.23. The withdrawal period for Spectrazol Milking Cow recommended for use in cattle (60h) was significantly shorter than the withdrawal period as measured by TRIS (P < 0.001) in Trial 2. Trial 3: Rilexine 200 LC The mean withdrawal periods for Rilexine 200 LC (intramammary) as measured by TRIS on 20 relatively high producing Saanen and Saanen-Toggenburg crossbreed dairy goats (Trial 3) was 37h ± 9.94. The withdrawal period for Rilexine 200 LC recommended for use in cattle (96h) was significantly longer than the withdrawal period as measured by TRIS (P < 0.001) in Trial 3. The regression model for goats with clinical mastitis was: Withdrawal period as measured by TRIS = 30.21 + 4.692 (sampling time) + 22.11 (udder palpation) – 13.6 (floccules) – 0.00649 (volume) (R2 = 95.7%, standard error of regression = 3.41) There was great variation in Somatic Cell Count (SCC) between trials, ranging from 1928 X 103cells/mL to 9274 X 103cells/mL for infected udder halves and from 1817 X 103cells/mL to 3639 X 103cells/mL for non-infected udder halves, at the morning milking. At the evening milking SCC ranged from 1927 X 103cells/mL to 6415 X 103cells/mL for infected udder halves and from 2103 X 103cells/mL to 3304 X 103cells/mL for non-infected udder halves. SCC of udder halves with clinical mastitis ranged from 7053 X 103cells/mL to 7948 X 103cells/mL for udder halves in which bacteria could not be isolated and from 6476 X 103cells/mL to 8479 X 103cells/mL in udder halves from which bacteria was isolated. Most of the variation in SCC was unexplained. In this research all SCC values were determined using the Fossomatic 90 counter and the arithmetic means were reported. The factors valid for determining clinical mastitis were the presence of floccules in the milk and high SCC, with or without udder damage and/ or bacteria. Intramammary infection (IMI) was determined by the presence or absence of bacteria only. Conclusions and Recommendations: The variability in SCC was largely unexplained, and an increased SCC did not necessarily indicate an intramammary infection in goats, as it does in cows. Therefore further, research is required to assess SCC and all possible factors affecting it. Further research is also required to find a more reliable method for mastitis diagnosis apart from SCC, for example, NAGase. The “Goatside” tests used (California Milk Cell Tests, CMCT) and SCC on their own were not reliable methods of mastitis diagnosis and should be accompanied by microbiological tests. However, CMCT and SCC were indicators of tissue tolerance and udder irritation. Tissue irritation is considered to indicate the limit of tissue tolerance. In healthy goats Spectrazol Milking cow caused the least tissue irritation, followed by Rilexine 200 LC, and Curaclox LC. However, for goats with clinical mastitis Rilexine 200 LC caused the least tissue irritation followed by Curaclox LC; and Spectrazol Milking cow caused the most tissue irritation in goats with clinical mastitis. Withdrawal periods of healthy goats and goats with clinical mastitis also differed for each product. Further research is necessary to determine withdrawal periods and tissue irritation of different intramammary products on goats with clinical mastitis. Withdrawal period was affected by volume of milk produced, due to the dilution factor of continuous milk secretion. High producers had shorter withdrawal periods than low producers. However, treatment with intramammary antibiotics did not significantly affect the volume of milk produced. Further research is required to assess the effect of milk production volume on withdrawal periods when comparing withdrawal periods of different products. Antibiotic withdrawal periods on goat milk were different from those recommended for use in cattle for each of the products used and for the different intramammary antibiotics used. The withdrawal periods recommended for use cattle have a 24h safety margin added to the longest withdrawal period in the trial. In this research 24h safety margins were not added in the original tables. Therefore, in practice 24h safety margins should be added to all withdrawal periods in this research. Later the 24h safety margins were subtracted from the withdrawal periods recommended for use in cattle in order to obtain a rough estimate of the actual withdrawal periods in cattle. In this analysis all withdrawal periods measured by different methods for goats were significantly different from withdrawal periods recommended for use in cattle (-24h safety margin). However, in the original tables not all withdrawal periods for goats as measured by different methods were significantly different from those in cattle (with 24h safety margin). Conductivity was found to be an unreliable “Goatside” test.