Udder Halves Research Articles

L’influence des conditions de travail

Forty-six Awassi sheep flocks selected by stratified random sampling were subjected to a cross-sectional study to determine the prevalence of intramammary infections, to assess the influence of flock size and parity on the prevalence of somatic cell count (SCC) and to identify major udder pathogens. Of the 3472 udder halves examined, 29.8% had over 106 SCC/ml and 0.03% had dry teats due to chronic mastitis. Flocks with 30–49 milking ewes (small flock size) were much younger (P < 0.001) than flocks with 50–99 ewes (medium) and flocks with ≥ 100 ewes (large). Pairwise analysis of the InSCC of both halves of the udders revealed significant mean differences for small and large flock size (P < 0.05), and for medium and large flock size (P < 0.001). Mean InSCC was lower (P < 0.05) in samples obtained from the left half compared with samples of the right half of the udder. Multiparous ewes had higher (P < 0.001) mean InSCC than primiparous ewes. Also, ewes with twin lambs had higher (P < 0.001) mean InSCC in the right half of the udder compared with single-lamb ewes. Samples collected in January (winter) had lower (P < 0.05) mean InSCC compared with samples collected in June. The most common organisms isolated from subclinical mastitis cases were coagulase-negative Staphylococci (17.8%), E. coli (13.6%), Streptococcus agalactiae (6.8%) and Staphylococcus aureus (6.8%). Of the 46 flocks, 20 were monitored monthly for 9 consecutive months to determine the incidence of clinical mastitis diagnosed by shepherds or/and sheep farmers with major pathogens. The incidence of clinical mastitis (expressed as the number of clinical cases per 100 ewe-months) were 2.1 ± 1.9 (SD), 1.9 ± 1.1, and 1.2 + 2.1 for small, medium and large flocks size strata, respectively. The overall population estimate was 1.7 ± 0.02 cases per 100 ewe-months. The most-common clinical isolates were S. aureus (22% of all clinical isolates) and E. coli (14.2%).

Influence of Vacuum Level and Overmilking on Udder Health and Teat Thickness Changes in Dairy Ewes

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 2min 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.

Removal of Hair Surrounding the Teat and Associated Bacterial Counts on Teat Skin Surface, in Milk, and Intramammary Infections

The effectiveness of monthly removal of hair surrounding teats on the reduction of teat skin surface bacteria, and the incidence of intramammary infection (IMI), was studied for 10 months in a dairy farm. A split udder design was used where hair was removed on one side, left or right, with the other side serving as a control. Controls and treatment sides were randomly applied in a systematic fashion to 218 cows. Standard milking time pre- and post-milking hygiene practices were applied to all udders during the trial. Collection of teat skin swab solutions preceded aseptic collection of milk samples, performed at monthly intervals, immediately prior to milking. Teat skin bacterial counts did not differ between control and treated teats. Incidences of IMI were similar for treatment when compared with control mammary quarters, as measured by total or by pathogen type. In a second study, the effect of hair removal on the bacterial content of milk was determined using 40 cows. Treatments and allocations were as described. Udder half milk, milk from both mammary quarters of each udder half, was combined and diverted into separate buckets. Buckets were thoroughly cleaned and sanitized between milkings. A portion of bucket milk was collected 24 h after removal of udder hair. The total milk bacterial counts, and counts of psychrotrophs and thermoduric organisms were not reduced by udder hair removal. Results do not suggest that removal of udder hair leads to an improvement in milk quality as determined by milk bacterial content in the herd studied.

Study on frequency, etiology and some enzymatic activities of subclinical ovine mastitis in Urmia, Iran

A total of 209 milk samples were collected from the udder halves of 178 native dairy ewes at 2 weeks after lambing until the 10th week postpartum. Those which were classified by bacterial culture and California Mastitis Test (CMT) as positive, were deemed to have glands with subclinical mastitis (SCM). The periodic prevalence rate of SCM was 39%. The most common bacterial isolates from SCM cases were coagulase negative staphylococci (41%), Bacillus cereus (33%), Staphylococcus aureus (22%) and Streptococcus spp. (4%). The mean activity of lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) were higher in milk from SCM udders than in milk from healthy udders ( P<0.01). There were no significant differences in blood serum LDH, ALP and aspartate aminotransferase (AST) of healthy and subclinical mastitic ewes. The increment in LDH and ALP in milk of udders shows the presence of tissue damage provoked by SCM. Thus, these parameters might be suitable for use in the early diagnosis of subclinical mastitis in ewes.

Udder infection and milk somatic cell count, NAGase activity and milk composition—fat, protein and lactose—in Israeli-Assaf and Awassi sheep

The present study aimed to identify the pathogens that cause subclinical udder infections in Israeli dairy sheep and evaluate their influence on milk yield and composition. Eight hundred and fifteen Israeli-Assaf and Israeli-Awassi dairy sheep were surveyed. More than half of the sheep were in their third or higher lactation (513/815 sheep) and in 14 out of 20 flocks; the sheep were in their peak (second to third month) of lactation. The percentage of bacteriological infected udders in the flocks ranged from 8.6 to 64.3%. The effect of the bacteriological infection on somatic cells count (SCC) was significant ( P>0.001). Various species of coagulase-negative staphylococci (CNS) mainly S. chromogenes and S. epidermidis, formed the main pathogen group in infected udders. Lactation number did not significantly influence either the infection rate of udder halves or the milk SCC, although the percentage of udder halves with no bacteriological findings found was higher at first lactation than at the second and third lactation. Milk yield was significantly higher in uninfected than in infected halves. Milk composition—fat, proteins and lactose—varied among flocks, with mean total protein lower in uninfected halves than in infected ones and lactose higher in uninfected than in infected halves.

Effects of Once Versus Twice Daily Milking Throughout Lactation on Milk Yield and Milk Composition in Dairy Goats

The effects of once (1X) vs. twice (2X) daily milking throughout lactation on milk yield, milk composition, somatic cell count (SCC), and udder health were studied in 32 Murciano-Granadina dairy goats. Goats were assigned at wk 2 of lactation to two treatment groups; once daily milking at 0900 (1X, n = 17), or twice daily milking at 0900 and 1700 (2X, n = 15). Milk yield was recorded weekly until wk 28, and milk composition and SCC were evaluated for each individual udder half at each milking at wk 2 and 4 of lactation and then, monthly until the end of the experiment. Once daily milking resulted in an 18% reduction in the yield of 4% fat-corrected milk compared to twice daily milking (1.61 vs. 1.95 L/d, respectively). This reduction was more marked from wk 2 to 12 than in mid and late lactation. Response to milking frequency also varied according to parity number where goats of less than four parities suffered more milk yield losses during 1X than older goats. Milk of 1X goats contained higher percentages of total solids (13.6 vs. 12.9%), fat (5.10 vs. 4.62%) and casein (2.57 vs. 2.35%) than milk of 2X goats, but milk protein percentage did not differ between treatments (3.28 vs. 3.20%). Yields of total solids, fat, protein and casein tended to be higher for 2X than 1X. Milk SCC did not differ between treatments. We conclude that application of once daily milking in Murciano-Granadina dairy goats moderately reduced milk yield without negative effects on milk composition and udder health. Losses in milk yield would be reduced if 1X is practiced during mid- or late lactation and in older goats. An increase in labor productivity and a higher farmer's standard of living is also expected.

Effect of freezing goat milk samples on recovery of intramammary bacterial pathogens

With the aim of evaluating the effect of freezing goat milk samples on recovery of intramammary pathogens, 1200 milk samples from udder halves with subclinical intramammary infection were studied. Samples (20 ml) were frozen at −20 and at −80 °C. Thawing was carried out at room temperature at 7, 14, 21, 28, 58, 118, 178, 236 and 730 days after collection and bacteriological analyses were carried out to determine the number of colony forming units/ml (CFU/ml). Mixed model statistical analysis showed that bacterial group, temperature of storage, interaction of bacterial group and temperature of storage and the interaction of bacterial group, time and temperature of storage were statistically significant effects. For coagulase negative staphylococci (CNS), least squares means of log CFU/ml recovered at −20 and −80 °C were not different. Nevertheless, for Gram negative bacilli (GNB) a significant decrease was detected in samples frozen at −20 vs. −80 °C. At both temperatures and at different times of storage, significant increases were detected between log CFU/ml of CNS and values on day zero. At −20 °C, a significant decrease in GNB recovery was detected between freezing days zero and 730. This difference was not detected when goat milk samples infected by GNB were frozen at −80 °C. The results show that frozen milk samples can be useful in goat subclinical mastitis control programs.

The Yield and Composition of Milk in Sarda, Awassi, and Merino Sheep Milked Unilaterally at Different Frequencies

Sarda (n=8), Awassi (n=8), and Merino (n=8) ewes were subjected unilaterally to once-daily milking (ODM) or twice daily milking (TDM) to test the hypothesis that the two breeds highly selected for milk production (Sarda and Awassi) would not respond as much to a change in the frequency of milking as the Merino, a wool sheep that has not been selected for dairy production. Milk composition and somatic cell count (SCC) were also assessed to determine if the changes in milking frequency affected milk quality. Milk yield was 24% and 18% lower in ODM udder halves than TDM udder halves in Sarda and Awassi breeds, respectively. The yield loss due to ODM was similar to that observed in Merino ewes (23%) and did not support our hypothesis. Fat content did not differ significantly in any breeds between ODM and TDM udder halves. Protein content was higher in the milk of ODM than TDM udder halves in Sarda and Merino ewes. The SCC was influenced by milking treatment only in the Sarda ewes, with high values observed in the milk of ODM udder halves. The same trend was observed in the Awassi and Merino breeds, but the differences were not significant. The effects on milk yield, composition, and SCC caused by ODM were completely reversed when TDM was resumed. This suggests that in sheep flocks the milk yield losses due to short-time suppression of one daily milking, for example, on festive days, are low and temporary.

Adenoviral-Mediated Transfer of a Lysostaphin Gene into the Goat Mammary Gland

As a step toward preventing and curing Staphylococcus aureus mastitis, an adenoviral-mediated gene transfer technique was used to enable mammary cells to synthesize and secrete lysostaphin, an anti-staphylococcal protein. A lysostaphin gene, modified for eukaryotic expression of the bioactive variant, Gln125, 232-lysostaphin, was inserted into a replication deficient adenovirus by homologous recombination in 293 cells. The resulting adenoviral vector containing the modified lysostaphin gene (Ad-lys) was used to infect bovine mammary epithelial cells in vitro and caprine mammary cells in vivo. A similar adenoviral vector containing the Escherichia coli gene encoding β-galactosidase (Ad-lacZ) was also evaluated. Transduction of cultured bovine cells by Ad-lacZ was confirmed by the presence of β-galactosidase in fixed cells 48h postinfection. Bovine cells transduced by Ad-lys secreted immunoreactive Gln125, 232-lysostaphin (0.8μg/ml) into media that had approximately 20% bioactivity compared with native lysostaphin. To evaluate transduction in vivo, udder halves of four nonlactating goats were exposed to 1010 plaque-forming units (pfu) of Ad-lacZ by two intramammary infusions given 48h apart. The animals were euthanized 24h later, and extensive expression of β-galactosidase was detected in cells lining the teat canals, with more moderate expression observed in adjoining mammary parenchyma. Udder halves of two other nonlactating goats were infused with 1010 pfu of Ad-lys while contralateral udder halves received Ad-lacZ. The animals were euthanized 48h postinfusion. In both animals, extensive expression of β-galactosidase was detected in Ad-lacZ exposed teats. Immunoreative Gln125, 232-lysostaphin was detectable in secretions from Ad-lys exposed glands 24h postinfusion, increasing to approximately 1μg/ml at 48h postinfusion. As with cultured bovine mammary epithelial cells, the bioactivity of goat-derived Gln125, 232-lysostaphin was approximately 20% of native lysostaphin. These results demonstrate that an adenoviral vector can be used to introduce a gene into the ruminant mammary gland, enabling the secretion of a bioactive form of lysostaphin.

Mammary Pathogens and Their Relationship to Somatic Cell Count and Milk Yield Losses in Dairy Ewes

A total of 9592 samples of half udder milk were collected monthly throughout lactation for bacteriological and somatic cell count (SCC) study from 1322 Churra ewe lactations from seven separate flocks enrolled in the recording scheme of the National Association of Spanish Churra Breeders in the Castile-León region of Spain. Statistical analyses were carried out from a mixed model with random factor half udder or ewe for repeated measures. Test of significance of fixed effects of this mixed model showed significant effects of organisms, flock, parity, lactation stage, and birth type on SCC. Special reference must be made to novobiocin-sensitive coagulase-negative staphylococci, which represented more than 50% of the isolates and which elicited SCC geometric means of around 106/ml. In addition, the analysis of 4352 monthly test-day records for milk yield, SCC, and bacteriology showed that the ewes that were uninfected and infected by minor pathogens had the lowest SCC and the highest milk yields, whereas those infected by major pathogens had high SCC and milk yield losses between 8.8 and 10.1% according to the uni- or bilateral character of the infection. Finally, ewes infected by novobiocin-sensitive coagulase-negative staphylococci elicited SCC values similar to those of infections by major pathogens and milk yield losses ranging between those caused by minor and major pathogens. As a result, emphasis should be put on prevention of subclinical mastitis, particularly mastitis caused by novobiocin-sensitive coagulase-negative staphylococci in dairy sheep herds to improve microbiological and hygienic milk quality and to minimize losses in milk yield.

Microbiological Quality and Somatic Cell Count of Ewe Milk with Special Reference to Staphylococci

A total 1502 useful half udders of 762 Churra ewes from eight herds were aseptically sampled in midlactation to study both the bacteriological isolates and the SCC of milk. Corynebacteria, enterococci, micrococci, staphylococci, and streptococci represented 11.2, 2.9, 1.4, 78.9, and 3.1% of all isolates, respectively. Within staphylococci, novobiocin-sensitive species (71.1%) were much more frequently isolated than novobiocin-resistant ones (7.8%). Staphylococcus epidermidis was the most prevalent species (53.2% of the isolates). Log SCC of uninfected half udder milk was 4.86. Isolates of novobiocin-resistant coagulase-negative staphylococci, micrococci, and corynebacteria were associated to low values of log SCC (4.85 to 5.20). In contrast, infection by novobiocin-sensitive coagulase-negative staphylococci, streptococci, and enterococci organisms was related to a sharp inflammatory response with log SCC means between 5.92 and 6.32. The species that showed the highest log SCC were Pasteurella haemolytica (7.62), Streptococcus agalactiae (7.28), and Staphylococcus aureus (6.68). High prevalence of infections by novobiocin-sensitive staphylococci together with high SCC related to such infections show a relevant role of these organisms in ewe mastitis. Consequently, implementation of staphylococcal mastitis control programs would be of great interest in dairy ewe herds to improve microbiological and hygienic quality of milk.

Effect of infectious status and parity on somatic cell count and California mastitis test in pampinta dairy ewes.

The relationship between somatic cell counts (SCC) and California mastitis test (CMT) results according to the infectious status of mammary halves and parity of Pampinta dairy ewes was evaluated. Tests were associated to bacteriological analysis and classified into three groups: uninfected (negative culture), infected by minor pathogens and infected by major pathogens. Coagulase-negative Staphylococcus (32.4%), Micrococcus spp. (32.4%), Corynebacterium spp. (5.4%), and Bacillus spp. (1.4%) were the minor pathogens isolated, while Staphylococcus aureus (27%) and Escherichia coli (1.4%) were the major pathogens isolated. A good correlation was found between the CMT and SCC, which included inflammatory and epithelial cells (r = 0.64; P < 0.0001). SCC averages for the CMT scores shown in parentheses were 223 576 (0); 245,248 (1); 397,778 (2); 1,159,109 (3) and 2,460,833 (4) cells/ml. The correlation between SCC and the infectious status of udder halves was 0.58 (P < 0.0001). The relationship between SCC and CMT profiles and infectious status studied by a discriminant analysis showed, with an accuracy of 65%, three infectious status groups. SCC arithmetic means were 244,470 cells/ml for negative culture, 1,044,100 cells/ml for minor pathogens and 2,045,652 cells/ ml for major pathogens. With the exception of 1-year-old ewes, no significant differences were observed in SCC as affected by age or parity.

Effect of intramammary infection by Staphylococcus caprae on somatic cell counts and milk composition in goats.

Since its identification by Devirese et al. (1983), Staphylococcus caprae has been frequently isolated from udder halves of goats with subclinical intramammary infection (IMI) (Contreras et al. 1995; Poutrel et al. 1996). Several different studies have demonstrated the capacity of Staph. caprae to persist throughout lactation (Poutrel et al. 1996; Contreras et al. 1997; Bedidi-Madani et al. 1998a) and during the dry period (Poutrel, 1984). Bedidi-Madani et al. (1998a) found that isolates of Staph. caprae from udders of uninfected goats express potential virulence factors (different exoproteins and slime); other researchers have occasionally isolated it from clinical cases of goat mastitis (Deinhofer &amp; Pernthaner, 1995), or from human clinical specimens associated with bone and joint infection (Vandenesh et al. 1995; Shuttleworth et al. 1997). In spite of these forms of pathogenicity, some studies have not shown significant increases in somatic cell count (SCC) of milk from goat udder halves infected by Staph. caprae (Deinhofer &amp; Pernthaner, 1995; Poutrel et al. 1996). Moreover, there is a lack of information on the effect of infection by this mammary pathogen on milk yield and composition. Knowledge of repercussions for hygiene and production would be useful in mastitis control programmes in view of the high frequency of isolation (higher than 22% of the staphylococci isolated) of Staph. caprae in dairy goat herds (Contreras et al. 1995; Poutrel et al. 1996). The aim of the present investigation was to ascertain the significance of persistent subclinical IMI by Staph. caprae on SCC, milk yield and physical-chemical parameters of Murciano-Granadina goat milk at mid-lactation.

Milk Synthetic Response of the Bovine Mammary Gland to an Increase in the Local Concentration of Arterial Glucose

Concentrations of glucose in the external iliac artery feeding one udder half of 14 midlactation Holstein cows were increased by infusion to test the following three hypotheses of mammary function: 1) that mammary glands control their blood supply to maintain intracellular energy balance, 2) that milk precursors are taken out of capillary blood according to mass action kinetics, and 3) that the rate of milk component synthesis is dependent on its precursor's uptake from blood. The first seven cows received 20g/h glucose during 10h of infusion. Arterial concentrations of glucose were locally increased by only 10%, and the iliac plasma flow was not affected by glucose infusion, so the next seven cows were given 90g/h glucose. Quantitative predictions resulting from the hypotheses were that arterial plasma flow would decrease by 32% with 90g/h glucose infusion, glucose uptakes would increase and acetate, fatty acid, and amino acid uptakes decrease, and milk protein and fat yields and percentages would decrease. Iliac plasma flow decreased 16%, half of what was predicted, which suggests that other regulatory processes besides blood flow control took part in the response. Acetate and fatty acid uptakes by the mammary glands were reduced as predicted because of the lower blood flow, but an unexpected depression in extraction of plasma triacylglycerol also contributed to the reduced fatty acid uptake. Milk fat and protein yields were not affected by the exogenous glucose, falsifying the third hypothesis that milk component secretion is a function of uptake of its precursor. Milk fat and protein percentages declined with glucose infusion because of increased lactose synthesis and secretion of water into milk.

Relationships between infection with caprine arthritis encephalitis virus, intramammary bacterial infection and somatic cell counts in dairy goats

Somatic cell counts, the bacteriological condition of the milk and antibodies against caprine arthritis encephalitis virus (cAEv) were measured monthly throughout lactation in 121 lactating goats of the Murcia- Granada...

The Role of Coagulase-Negative Staphylococcus spp. and Associated Somatic Cell Counts in the Ovine Mammary Gland

The somatic cell count (SCC) of ewes’ milk was determined by the Fossomatic method and compared with the bacteriological status of the mammary gland. Of 366 samples from uninfected udder halves, 64.5% had SCC less than 50×103 cells/ml, 81.9% had SCC less than 250×103, and 92.4% had less than 500×103 cells/ml. Of 130 bacteriologically positive samples, 91.1% had SCC more than 500×103 cells/ml and 98.8% more than 250×103. Of the examined milk samples 26.2% showed positive bacteriology during the single sampling. The most frequent pathogens isolated from the milk samples were coagulase-negative staphylococci. Considering our results, 250×103 cells/ml should be the threshold value, which could be regarded as the upper limit for normal SCC of ewes’ milk.

Udder disease etiology, milk somatic cell counts and NAGase activity in Israeli Assaf sheep throughout lactation

Bacterial pathogens causing udder infections in Israeli Assaf dairy sheep were identified and changes occurring throughout lactation were monitored to study the correlation between the contaminant and the severity of the infection, as measured by somatic cell count (SCC) and NAGase tests. A total of 159 Israeli Assaf dairy sheep on one farm, in their first (69), second (13) or third and more (77) lactations were included in this study. Udder halves were tested for bacterial condition, SCC and NAGase activity 2–3 weeks post lambing and every 4 weeks after until drying-off. At first sampling, in 60.7% (193/318 quarters) of the halves no bacterial growth (NBG) was detected. Different species of coagulase negative staphylococci (CNS) were the main pathogen group in infected udders. Streptococci were isolated from 14 halves, most of them in the two udder halves. The percent of udder infection in sheep in their third or further lactations was 2.8 greater ( P<0.05) than in that of sheep in their first lactation. During the lactation, 90.6% of the halves did not change their classification status, suggesting that most infections occur before lambing and/or during the following first few days. The arithmetic mean of SCC and NAGase of total half udder milk and samplings (during the lactation) were 1144±48×10 3 cells/ml and 49.4±2.5, respectively. The average SCC in the milk of halves classified as NBG was 321±35×10 3 cells/ml and was not significantly changed during the lactation period. In halves infected with CNS, average SCC was 1371±150×10 3 cells/ml at the first testing and increased to 2129±347×10 3 cells/ml at drying-off. No significant differences were found in SCC and NAGase activity between the different species of the CNS. The mean SCC over the types of bacteria isolated, lactation number and days in lactation was significantly different ( P<0.0001). In 4% of the halves, from all samples, SCC was above 5000×10 3 cells/ml although no bacteria were detected in their milk. The higher SCC in the CNS infected halves contrasted with the more moderate SCC found in dairy cows similarly infected, suggesting that the sheep udder has a lower resistance and an augmented immunological response against this group of bacteria. Thus, this should be considered accordingly in schemes for sheep’s milk quality payment.

Thrice-daily milking throughout lactation maintains epithelial integrity and thereby improves milk protein quality.

Cows managed for extended lactations of 16 months duration were milked on a half-udder basis twice or thrice daily, commencing in lactation week 9. Mammary epithelial integrity (assessed by milk sodium : potassium ratio) was greater in the half-udder which was milked thrice daily. This difference was evident throughout the lactation but became greater after week 41. Milk protein composition was assessed during late lactation (52+/-3 weeks). Casein number (casein as a proportion of total protein) was significantly higher in half-udders milked thrice daily, as were the relative amounts of alpha- and beta-caseins, whilst those of kappa- and- caseins were reduced. Two days of inverted milking frequency (i.e. thrice-milked udder halves now milked twice, and vice versa) only partly reversed these differences. We concluded that thrice-daily milking will help to prevent or ameliorate the usual decline in milk processing quality associated with late lactation. Part of this effect is due simply to reduced exposure to proteolytic enzymes as a result of decreased storage time in the udder, but part is due to a better maintenance of epithelial tight junction integrity as lactation advances, which restricts leakage of proteolytic enzymes from serum into milk.

Tissue distribution of benzylpenicillin after intramammary administration in the isolated perfused bovine udder.

Udders from previously healthy lactating cows were perfused with warmed and gassed Tyrode solution in vitro. Benzylpenicillin was administered in three formulations: an oily suspension with micronized particles of <10 microm diameter, an oily suspension with average particle size of 40 microm and an aqueous solution (3 million IU benzylpenicillin-potassium, volume 15 mL). The antibiotics were administered intracisternally to six front and six rear quarters each. Moreover, a dry-off-ointment (100 000 IU benzylpenicillin-potassium and 100 000 IU benzylpenicillin-benzathine, volume 7.5 mL) was tested in four udder halves. Perfusate samples were collected over 3 h. Furthermore, glandular tissue at different vertical distances from the teat base and the regional lymph node were sampled after 3 h. The determination of benzylpenicillin was performed by high pressure liquid chromatography with UV detection. With increasing distance from the teat base, the concentration of benzylpenicillin in tissue exponentially decreased. Using the aqueous solution or oily suspension that contained micronized active principle, higher concentrations were reached compared to the formulation with particle sizes of 40 microm. In udder lymph nodes, the concentration was highest after treatment with the coarse suspension. The transfer from the dry-off-ointment with benzathine-salt into perfusate was very low. These results suggest that it is possible to study tissue distribution of antibiotics in the isolated perfused bovine udder.

Effects of secretion removal on bovine mammary gland function following an extended milk stasis.

The objective of this study was to determine whether lactation function could be reinitiated after a period of extended milk stasis. Involution was induced by milk stasis in lactating Holstein cows for a period of 11 d. On d 11, one side of the mammary gland was milked twice daily for 3 d. The contralateral side remained unmilked for the 14-d experimental period. Cows were slaughtered, and mammary tissue was collected from both udder halves for further analysis. Mammary secretion volume was partially restored in the milked udder half, but reestablished milk yields were variable among cows. A partial recovery of lactation function was further indicated by elevated levels of lactose and protein profiles resembling milk in mammary secretions from the milked glands. Lactose and protein profiles from the unmilked glands were similar to those of glands undergoing involution. Lactoferrin levels were elevated in secretions from the milked and unmilked udder halves. Casein and lactoferrin synthesis by mammary explants and beta-casein and lactoferrin mRNA abundance in mammary tissues corresponded to protein profiles from milked and unmilked mammary secretions. alpha-Lactalbumin mRNA was variable but was more abundant in the milked glands compared with the unmilked glands. Lectin fluorescence microscopy for soybean agglutinin preferentially stained the apical surface of the mammary epithelial cells from the milked glands. Staining was absent in the unmilked glands and suggested resumption of lactation function in all such milked glands. These results suggest that mammary involution can be partially reversible after 11 d of milk stasis.