Nutrition of Coryneform Bacteria from Milk and Dairy Sources

S ummary . Growth requirements were determined for 112 cultures of coryneform bacteria including strains of Corynebacterium bovis, C. ulcerans and C. lacticum ; in general they were quite distinctive. Of 42 C. bovis strains all had an unsaturated fatty acid requirement fulfilled in chemically defined media by Tween 80, and, but for an atypically nonureolytic strain, all utilized ammonia and urea nitrogen. Whereas vitamins were unessential for the majority of C. bovis. 18 strains failed to grow in the absence of nicotinic acid; however, for 11 of these Casamino Acids replaced nicotinic acid in supporting growth. Thirteen C. ulcerans strains from aseptically drawn milk, as well as two Type Culture strains (NCTC 7907 and 7908) from the human throat required amino acid nitrogen sources, nicotinic acid, pantothenate and biotin. Some nutritional heterogeneity was shown by 46 strains collectively described as C. lacticum obtained from market milk, milk products and dairy utensils; nevertheless the nutritional differences between the groups of these strains correlated broadly with other distinguishing properties. A group of 9 markedly caseolytic strains required amino acid nitrogen sources, thiamine and biotin, whereas a second group of 30 strains, some utilizing inorganic nitrogen sources, required thiamine and pantothenate, with or without biotin. The remaining C. lacticum strains together with a number of unidentified strains from similar sources were generally slow growing and had widely differing growth requirements.     

Prevalence in Bulk Tank Milk and Epidemiology of Campylobacter jejuni in Dairy Herds in Northern Italy

Thermotolerant Campylobacter spp. are frequently the cause of human gastroenteritis and have assumed more importance in Italy following the increased consumption of raw milk. Our objectives were to determine the prevalence and genotypes of Campylobacter spp. in dairy herds and to investigate the possible sources of bulk milk contamination. Bulk milk from dairy herds (n = 282) was cultured for Campylobacter spp. and Enterobacteriaceae. At three Campylobacter jejuni-positive farms, bovine feces, pigeon intestines, milk, and water points were also investigated. Isolates were identified by PCR and genotyped using multilocus sequence typing (MLST). C. jejuni was detected in 34 (12%) bulk milk samples. The strains belonged to 14 sequence types, and the most common clonal complexes were CC-21, CC-48, and CC-403. No association was demonstrated between the presence of C. jejuni and high levels of Enterobacteriaceae in bulk milk. At the three farms examined, C. jejuni was isolated from bovine feces (25/82 [30.5%]), pigeon intestines (13/60 [21.7%]), bulk milk (10/24 [41.7%]), and water points (4/16 [25%]). MLST revealed lineages that were common between milk and bovine feces but distinct between cattle and pigeons. In one herd, C. jejuni with the same genotype was isolated repeatedly from bulk milk and a cow with an udder infection. Our results showed a high prevalence of C. jejuni in bulk milk and suggested that udder excretion, in addition to fecal matter, may be a route of bulk milk contamination. MLST analysis indicated that pigeons are probably not relevant for the transmission of C. jejuni to cattle and for milk contamination.     

Cubicle Refusal in Norwegian Dairy Herds

In order to survey the behaviour of choosing the alley area instead of a cubicle as a lying place (cubicle refusal), a questionnaire was sent to the 273 dairy farms in Norway known to keep cows in cubicle housing systems. Sixty-six percent of the farmers contacted were included in the study. The median herd size was 18 cows (range 7–118). More than 85% of the herds had sheds providing one or more cubicles per cow. The mean herd occurrence of cubicle refusal was 6%, but showed great variation (range 0–55%). Regression analysis showed a significant association between rearing heifers in slatted floor pens and an increased cubicle refusal occurrence (p = 0.02, R² = 0.05), while herd size, use of litter, or cubicle-to-animal ratio were not found to be associated with cubicle refusal. The practice of rearing heifers in slatted floor pens accounted for about one half of the observed cubicle refusal (etiologic fraction = 0.51).     

Antibodies Against Staphylococcus Aureus Nuclease in Bulk Milk As An Indicator of Mastitis in Dairy Herds

Titres of staphylococcal antinucleases and cell counts in bulk milk samples were compared as indicative criteria of the mastitis situation in dairy herds. The correlation coefficients between the prevalence rate of mastitis and the antinuclease titre and cell count, respectively, were of the same order of magnitude. The incidence of clinical mastitis showed a better correlation to the antinuclease titre than to the cell count. When cell counts and antinuclease titres were combined a more reliable selection of herds with a possible mastitis problem was achieved. The antinuclease test is consequently recommended as a supplement to cell counting when screening bulk milk.     

Management of Calving in Norwegian Cubicle-Housed Dairy Herds

Sixty of the 65 dairy farms with cubicle houses in the Norwegian county of Oppland were included in a field study of the management of calving in 1990. The farmers recorded the location of the cow when giving birth, farmer presence and whether assistance was given during calving, occurrence of suckling, and time after birth when cow and calf were separated. Such data were recorded for a total of 1125 calvings. About 10% occurred on pasture, while 78% of the remaining calvings took place in the cubicle-equipped section. Thirteen percent calved in a calving pen, the remaining cows being tethered at the time of calving. Thirty-two percent of the calvings took place in houses lacking a calving pen altogether. Farmers were present during 41% of the calvings. Suckling most frequently occurred after pasture calvings, and was least frequent after calvings within the cubicle-equipped section of the cowhouse. Injuries to the calf caused by trampling or contact with fittings etc. were rare, and no more common in association with calving in the cubicle-equipped section than with calving taking place with the cow isolated from the rest of the herd. All calves were removed from their dams within 24 h after birth.     

Urea and Biuret as Nitrogen Sources for Rhizobium Spp.

Ability to utilize urea as nitrogen source proved to be universal in 80 fast and 40 slow growing strains of Rhizobium spp. from 23 genera of host plants, and also in 10 strains of Agrobacterium radiobacter. Rhizobium meliloti (32 strains) as well as A. radiobacter constantly failed to utilize biuret. Most rhizobia from other host plants (with 8 exceptions among 88) were able to use biuret as a somewhat suboptimal source of nitrogen, which was generally assimilated at a slower rate than urea and rarely resulted in the same amount of growth, particularly in the fast growing strains; in exceptional cases and mostly among the slow growing strains biuret appeared slightly superior to urea. Adaptation experiments showed that urease occurred as a constitutive enzyme in Rh. leguminosarum , while the biuret decomposing enzyme appeared to be inducible.     

Calf Diseases and Mortality in Swedish Dairy Herds

A survey of the mortality and morbidity affecting calves during the first 3 months of life was carried out. Results are reported from 131 herds with altogether 5,050 calvings. These herds kept individual calf cards for all calves born. The incidences of abortions and stillborn calves were 0.6% and 3.6%, respectively. During the period 0-90 days the mortality and morbidity were 2.6% and 11.0%, respectively. The frequencies of enteritis and pneumonia in calves were 7.2% and 0.8%. Mortality and morbidity were influenced by breed, season, age of the dam and time of first colostrum. The frequencies of abortions, stillborn calves, mortality and morbidity varied considerably between herds. Herd factors influencing mortality and morbidity during different periods of time were: herd size, yield, zero-grazing, whether the calf was allowed to feed by suckling, the design of the calf pens, and previous incidence of infectious enteritis in the herd. On average, both mortality and morbidity in calves were low, though in certain herds, temporarily high frequencies were registered.     

Ketosis in Norwegian Dairy Herds — Some Epidemiological Associations

Ketosis data from the Health Card System, and interview data regarding feeding, housing, management and care were the basis for an epidemiological study in 306 Norwegian dairy herds. Management and care were studied by means of an overall care index. The index was based on 20 questions which provided information about the general standard of management and care. Care was the factor having the most pronounced effect on the treatment rate of ketosis. Highest rates were seen in herds with a high standard of management and care, and lowest rates were seen in herds with a low standard. Most ketosis was found in the mountain valley districts Nord-Østerdal/Gudbrandsdal and Valdres, and least in the lowland coastal district Rogaland. The treatment rate decreased with increasing herd size, and with increasing number of different feedstuffs used. Extra provision of feed concentrates between the morning and evening chores was associated with a lower treatment rate. Also associated with a lower treatment rate was the participation by the farmer’s wife in the daily chores.     

Blood Selenium Associated with Health and Fertility in Norwegian Dairy Herds

A survey of blood selenium (Se) concentrations in Norwegian Red heifers and dry period cows was conducted to reveal possible association to management, feeding, health and fertility. Selenium contents were determined in 254 herd blood samples consisting of pooled samples from individual non-lactating animals from herds in 5 counties. The Se concentrations showed a normal distribution with mean 0.09 μg Se/g blood, with a standard deviation (SD) of 0.05, and ranged from 0.02 to 0.23 μg/g, with 50 % of the samples being between 0.06 and 0.11 μg/g. The herds with Se concentrations below 0.06 μg/g were smaller (21.4 ± 8.7 cow-years) than those with Se levels above 0.11 μg/g (27.5 ± 14.1 cow-years) (P < 0.01), but there were no differences in milk yield, incidence of replacement, proportion of animal culling, amount of concentrate or grass silage as percentage of energy consumption between the groups. Treatment registration records showed a tendency that more animals in the low Se herds were treated for all the diseases included in this investigation (64.8 animals per 100 cow-years) than those in the high Se herds (57.5 per 100 cow-years), while no such differences were revealed for individual disorders. There was, however, a significant difference in bulk milk somatic cell counts (BMSCC) between low and high Se herds, their values being 137 000 and 155 000 cells/ml, respectively. This difference was significantly influenced by herd size. Furthermore, a total of 4 916 lactations were analyzed from individual health and fertility recordings, including 2 934 first lactations and 1 982 later lactations. The present study revealed a reduced incidence of disease treatment with increased Se concentrations from 0.02 to 0.23 μg Se/g blood. In this regard, there seemed to be an optimum of 0.10 to 0.15 μg Se/g for all types of mastitis treatments summarized, and for treatment of retained placenta. Thus, herd Se concentrations below and above these values was connected with increased probability for sum mastitis and retained placenta, reflecting the effect of the quadratic term of Se. The cow (composite) milk somatic cell count (SCC) was lower in lactations from low Se herds than in high Se herds with a marked SCC increase in the Se concentration interval from 0.11–0.13 μg/g blood. In conclusion, heifers and dry period cows in Norway are low in blood Se content and there seems to be a positive association between increased blood Se concentration pre partum and decreased incidence of mastitis, ovarian cysts and anoestrus/silent oestrus post partum.     

The Influence of Urea and Other Nitrogen Sources on Growth Rate of Scots Pine Seedlings

The growth rate and water content of urea-fed seedlings of Pinus silvestris L. were compared with those of nitrate-and ammonium-fed seedlings grown in continuously renewed nutrient solutions, in which the hydrolysis of urea to ammonia and carbon dioxide was minimized. The growth rate of seedlings grown in an ammonium nutrient solution, in an urea nutrient solution and in a nitrate nutrient solution was about 90 per cent, 75 per cent and 60 per cent, respectively, of that of seedlings grown in a mixture of ammonium and nitrate. Seedlings with urea as the sole nitrogen source developed very severe chlorosis of the needles, the old roots were dark-coloured, the whole root system was very fragile, and the lateral roots of the third order were missing. Urea-grown seedlings had the highest nitrogen contents, closely followed by the ammonium and the ammonium + nitrate seedlings. The lowest nitrogen level was in nitrate seedlings. The low growth rate and the chlorosis of urea-fed seedlings were suggested to be the result of a hydrolysis of urea inside the root, causing an increase in pH and an accumulation of ammonia in the root.     

Assessment of Early Postpartum Reproductive Performance in Two High Producing Estonian Dairy Herds

Early postpartum (6 weeks) ovarian activity, hormonal profiles, uterine involution, uterine infections, serum electrolytes, glucose, milk acetoacetate and blood urea nitrogen (BUN) levels were studied in 2 Estonian high producing dairy herd with annual milk production of 7688 (Farm A) and 9425 (Farm B). From each farm 10 cows, with normal calving performance were used. Blood samples for the hormonal (PGF_2α-metabolite, progesterone) analyses were withdrawn. On day 25 PP blood serum samples were taken for the evaluation of metabolic/electrolyte status. On the same day estimation of milk acetoacetate values was done. The ultrasound (US) was started on day 7 PP and was performed every 3^rd day until the end of experiment. Uterine content, follicular activity and sizes of the largest follicle and corpus luteum were monitored and measured. Vaginal discharge and uterine tone were recorded during the rectal palpation. Each animal in the study was sampled for bacteriological examination using endometrial biopsies once a week. Two types of PGF_2α-metabolite patterns were detected: elevated levels during 14 days PP, then decline to the basal level and then a second small elevation at the time of final elimination of the bacteria from the uterus; or elevated levels during first 7 days PP, then decline to the basal level and a second small elevation before the final elimination of bacteria. Endometritis was diagnosed in 5 cows in farm A and in 3 cows in farm B respectively. In farm A, 5 cows out of 10 ovulated during experimental period and in 1 cow cystic ovaries were found. In farm B, 3 cows out of 10 ovulated. In 3 cows cystic ovaries were found. Altogether 40% of cows had their first ovulation during the experimental period. Three cows in farm A and 5 cows in farm B were totally bacteria negative during the experimental period. The most frequent bacteria found were A. pyogenes, Streptococcus spp., E. coli., F. necrophorum and Bacteroides spp. The highest incidence of bacteriological species was found during the first 3 weeks in both farms. All animals were free from bacteria after 5^th week PP in farm A and after 4^th week in farm B respectively. Serum electrolytes and glucose levels were found to be within the reference limits for the cows in both farms. No significant difference was found between farms (p > 0.05). Low phosphorus levels were found in both farms. Significant difference (p < 0.05) was found in BUN levels between farms. In both farms milk acetoacetate values were staying within the reference range given for the used test (<100 μmol/l). The uterine involution and bacterial elimination in the investigated cows could consider as normal but more profound metabolic studies could be needed to find reasons for later resumption of ovarian activity. Some recommendations to changing feeding regimes and strategies should also be given.     

BVDV and BHV-1 Infections in Dairy Herds in Northern and Northeastern Thailand

Bulk milk samples from 220 dairy herds were collected at 9 public milk collection centres in the northeastern and northern Thailand, and a subset of 11 herds was selected for individual testing. The samples were tested for presence of antibodies to BVDV and BHV-1 using an indirect ELISA. The results from the bulk milk testing demonstrated a moderate level of exposure to BVDV and BHV-1 (73% and 67%, respectively). However, the low proportion of herds with high BVDV antibody-levels (13%) and the low within-herd seroprevalence of BVDV and BHV-1 in the 11 herds (24% and 5%, respectively), particularly among the young stock (15% and 0%, respectively), demonstrated a low prevalence of active BVDV infection and a low rate of reactivation of latent BHV-1. The presence of a self-clearance process was also indicated by the results from the individual testing. Moreover, a surprisingly low prevalence of BVDV and BHV-1 antibody-positive herds at one of the milk centres was found. This centre was established 5–10 years before the others. Our impression is that this reflects the self-clearance process, where consecutive replacement of imported infected animals without further spread has resulted in a nearly total elimination of the infections.     

Staphylococcal and other Bacterial Species Associated with Intramammary Infections in Danish Dairy Herds

Four thousand six hundred forty– five quarter milk samples from 1179 cows from 20 commercial dairy herds were examined in order to determine the prevalence of bacterial species. A total of 859 isolates from 839 (18.1%) culture positive samples could be assigned to 34 different species and subspecies. Diagnostics of staphylococcal species was based on conventional procedures able to differentiate between all 36 species and subspecies presently acknowledged. Staphylococcus aureus was found in 10.2% of the samples and was the most common species isolated. Streptococcus dysgalactiae (1.6%) and Streptococcus uberis (1.4%) were the second and third most common species isolated. Seventeen different coagulase negative staphylococcal species (CNS) were found in 4.1% of the samples. The most frequently isolated CNS were S. epidermidis (1.3%), S. chromogenes (1.0%) and S. simulans (0.7%). Isolates of S. aureus were phage typed, and isolates of S. epidermidis were investigated by phage typing, antibiogram typing, and biotyping. A total of 378 (79.9%) isolates of S. aureus could be typed by phages, assigning them to 18 different phage types. However, 6 phage types accounted for 92.1% of the typable isolates. One to 2 phage types predominated within each herd. Eleven (18%) isolates of S. epidermidis could be typed by phages, assigning the isolates to 3 different types. Biotyping of S. epidermidis produced a total of 8 different types, the most common accounting for 29.5% of the isolates. A total of 6 different antibiogram types were observed among all isolates of S. epidermidis. Resistance towards penicillin (36.1%), tetracycline (9.8%) and streptomycin (9.8%), were recorded in the isolates of S. epidermidis. However, 35 (57.4%) of the isolates were susceptible to all 12 antibiotics tested.     

Arcobacter butzleri,Arcobacter cryaerophilus,and Arcobacter skirrowii Circulation in a Dairy Farm and Sources of Milk Contamination

Even though dairy cows are known carriers of Arcobacter species and raw or minimally processed foods are recognized as the main sources of human Arcobacter infections in industrialized countries, data on Arcobacter excretion patterns in cows and in milk are scant. This study aimed to identify potentially pathogenic Arcobacter species in a dairy herd and to investigate the routes of Arcobacter transmission among animals and the potential sources of cattle infection and milk contamination. A strategy of sampling the same 50 dairy animals, feed, water, and milk every month for a 10-month period, as well as the sampling of quarter milk, animal teats, the milking environment, and animals living on the farm (pigeons and cats), was used to evaluate, by pulsed-field gel electrophoresis (PFGE), the characteristic patterns in animals, their living environment, and the raw milk they produced. Of the 463 samples collected, 105 (22.6%) were positive for Arcobacter spp. by culture examination. All the matrices except quarter milk and pigeon gut samples were positive, with prevalences ranging from 15 to 83% depending on the sample. Only three Arcobacter species, Arcobacter cryaerophilus (54.2%), A. butzleri (34.2%), and A. skirrowii (32.3%), were detected. PFGE analysis of 370 isolates from positive samples provided strong evidence of Arcobacter circulation in the herd: cattle likely acquire the microorganisms by orofecal transmission, either by direct contact or from the environment, or both. Water appears to be a major source of animal infection. Raw milk produced by the farm and collected from a bulk tank was frequently contaminated (80%) by A. butzleri; our PFGE findings excluded primary contamination of milk, whereas teats and milking machine surfaces could be sources of Arcobacter milk contamination.     

Housing, Feeding and Management of Calves and Replacement Heifers in Swedish Dairy Herds

A questionnaire was sent to 1500 randomly selected dairy herds in Sweden, asking for general information about the herds, including routines from birth to first calving and also routines at breeding, calving and during the grazing period. Fifty-eight percent of the questionnaires were returned. The preweaned calves were kept in individual calf pens in 68% and in group housing systems in 28% of the herds. Pens with slatted floors were the main housing system for replacement heifers from weaning to breeding, and tie stalls from breeding to first calving. Whole milk was used in 44% and milk replacements in 42% of the herds. The calves received, as a median, 2.5 litres of milk per meal and 2 meals per day. The median age at weaning was 8 weeks. Age was the single most common criteria used for deciding both weaning and breeding time. The median age when the heifers were first turned out to pasture was 6 months. Prophylactic anthelmintic treatment was used by 65% of the herds. The most common diet for replacement heifers before calving was a combination of grain, hay and silage.