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1.
The purpose of the trial was to establish the effect of the injection of the lysozyme dimer or vitamins connected with Se on the activity of chosen antioxidant enzymes and the total antioxidant status in pregnant heifers. Examinations were carried out during winter season in one farm on 21 heifers aged 22-24 months. Between the 21st and 14st day before expected parturition, seven heifers were once i.m. injected with antioxidants (Vitamin A-600 000 i.u.; Vitamin D3-200 000 i.u.; Vitamin E-1.5 mg/kg b.w., Selenium-0.022 mg/kg b.w.), and the next seven animals with lysozyme dimer (Lydium-KLP) at a dose of 0.02 mg/kg b.w. versus 7 non-treated control animals. Blood samples were taken before injection and then in hour 24 and 72 after injection, and between, the 7th and 14th day after calving. The activity of superoxide dismutase (SOD), glutathione peroxidase (GSHpx), glutathione reductase (GSHred) and total antioxidant status (TAS) were measured by colorimetric method with the use of Randox kits. The mean value of SOD activity 21-14 days before expected calving was 704.8 +/- 294.6 U/ml of whole blood, GSHpx 59222 +/- 23699 U/l of whole blood, GSHred 110.8 +/- 22.5 U/l and TAS 0.33 +/- 0.15 mmol/l of serum. These indicators did not change in the control group with the exception of a statistically insignificant decrease in SOD activity after parturition. Statistically significant increase in blood SOD activity was noted only in the first day after injection of vitamins combined with selenium. These antioxidants also caused an insignificant increase in blood GSHpx activity in 72 hour following the injection, and in the second week after calving (statistically significant). The injection of antioxidants or lysozyme dimer did not change the activity of blood GSHred. However, an increase in the TAS was found in hour 24 (non significant) and 72 (statistically significant) following the single injection of lysozyme dimer.  相似文献   

2.
Twenty primiparous heifers were fitted intramammarily with polyethylene coils in both quarters of one random right or left udder half at 5 days after parturition. Foremilk samples were collected and udder-half milk yields were measured at the afternoon milking on days - 1, 3, 7, and 14 and on every 14th day for 8 months after the device was inserted. Three weeks after the heifers were fitted with the intramammary device, 6 were euthanatized for gross observation of devices and tissues and cytologic evaluation of the gland cistern epithelium. There were significantly fewer bacterial isolations (P less than 0.01) and less clinical mastitis (P less than 0.05) in treated quarters than in the control quarters. Coagulase-negative staphylococci were isolated at frequencies of 0 and 15.2% for treated and control quarters. The reduction in isolation frequency for treated, compared with control, quarters was less marked with other organisms. Intramammary devices in no way interfered with the milking process. Milk yields per milking were 4.2 kg for treated udder halves compared with 4.4 kg for control halves; however, this 0.2 kg difference was not significant. Mean milk somatic cell counts, as determined by electronic counter, were 34 X 10(3) and 81 X 10(3) cells/ml for control and treated quarters (P less than 0.05). Mean bovine serum albumin values were 0.160 and 0.175 mg/ml for control and treated udder halves (P less than 0.05), indicating an increased capillary permeability due to the device. Quantitative morphologic analysis of gland cisterns showed a significant (P less than 0.05) change toward a single layer of epithelial cells in treated quarters compared with a double layer in control quarters.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
The effect of teat dipping with a barrier teat dip prior to parturition on intramammary infection (IMI) and clinical mastitis during the first 5 days post-partum was investigated in a split udder trial in 149 Holstein-Frisian heifers. Their left front and right hind quarters were dipped three times weekly (i.e. Monday, Wednesday and Friday) with a barrier teat dip containing 0.1% polyvidon iodine from day 260 of gestation until parturition. The opposite quarters (right front and left hind quarter) served as untreated control. Bacteria were isolated from 52.2% of quarter milk samples collected immediately after parturition prior to first machine milking. Staphylococcus aureus and coagulase-negative staphylococci (CNS) were predominantly found in the samples (29.2 and 35.6% of the positive samples, respectively). At parturition 6.7% of the heifers showed signs of clinical mastitis and another 27.5% developed signs of clinical mastitis during the first five days of lactation. No significant differences were found between treated and control quarters regarding IMI and incidence of clinical mastitis. Teat dipping prior to parturition in primigravid dairy heifers did not improve udder health in this trial.  相似文献   

4.
Risk factors for intramammary infections caused by coagulase-negative staphylococci, contagious major pathogens and environmental major pathogens in early lactating heifers were evaluated at the herd, heifer and quarter levels. In total, 764 quarters of 191 dairy heifers in 20 randomly selected farms in Flanders (Belgium) were sampled. Quarter milk samples were collected between 1 and 4 days in milk and between 5 and 8 days in milk for bacteriological culture. Data were analyzed using multivariable, multilevel logistic regression analysis. Higher average herd milk somatic cell count (>200,000 cells/mL), not having an effective fly control strategy, contact with lactating cows prior to calving and moderate to severe udder edema prior to calving increased the odds of intramammary infections caused by contagious major pathogens. Poor heifer hygiene and lack of mineral/vitamin supplementation prior to calving were risk factors for intramammary infection caused by environmental major pathogens. Teat apex colonization with coagulase-negative staphylococci prior to calving seemed to protect quarters against intramammary infections caused by major pathogens. Poor heifer hygiene before calving, a non-clipped udder and not practicing of teat dipping prior to calving increased the odds of intramammary infection with coagulase-negative staphylococci. Although management is important in the prevention and control of intramammary infections in early lactating heifers, most variation in the prevalence of intramammary infections resided at the heifer and quarter levels, indicating that the susceptibility for intramammary infections around calving is mainly determined by heifer and quarter characteristics.  相似文献   

5.
The objective of this study was to determine risk factors for udder edema (case–control study) and to evaluate the association of udder edema in primiparous Holstein cows with their lactation performance (cohort study). Values for the first 10 test day for milk yield, fat, protein, and somatic cell counts (SCC) linear score as well as mature equivalent (ME) 305 days milk yield, fat, protein, SCC linear score, and incidences of periparturient diseases from a computerized farm recording system were compared between primiparous cows with and without udder edema. Data consisted of 118 dairy heifers with udder edema, induced for parturition, and treated with diuretics and 889 control heifers that received no treatment. Primiparous cows giving birth to male calves, were 1.72 (1.01, 3.24; 95% CI) times more likely to develop udder edema than cows giving birth to female calves. Primiparous cows calving in winter season were 3.68 (1.09, 12.5; 95% CI) times more likely to develop udder edema than cows calving in summer. For each extra 10 cm in height the odds of udder edemas was 1.23 (1.03, 1.47; 95% CI). The first test day DHIA milk yield was lower in cows that developed udder edema (3.6 kg/day) than in normal cows. However, the subsequent test days and ME measurements were not statistically different between groups. Cows with udder edema were 1.62 (1.18, 2.14; 95% CI) times more likely to develop udder edema in the second lactation than control animals. It is concluded that the gender of the offspring, calving season and height at parturition were significant risk factors for udder edema. Only milk yield on the first DHIA test day was lower in cows with udder edema than in cows without udder edema.  相似文献   

6.
Dairy heifers represent the future of a dairy herd, and are expected to freshen with a healthy and well-developed udder, capable of producing an optimal amount of high quality milk. A high proportion of heifers have infected mammary quarters at calving, with coagulase-negative staphylococci (CNS) being the most common cause. Staphylococcus aureus and environmental pathogens are also found. The aim of this paper is to summarize how intramammary infections during (late) gestation and early lactation impair the development of the mammary gland and negatively affect future udder health and milk production. Heifers calving with either subclinical or clinical mastitis are also at a higher risk to be culled in first lactation. The magnitude of the effect is most likely related to the virulence of the causative pathogen, the persistence of the infection when milk production has started, and the time of onset of infection. Histological changes in udder tissue from quarters infected with S. aureus are more pronounced than those in udder tissue from CNS-infected quarters. The longer the infections exist and the longer they persist into lactation, the larger the impact on heifers' future udder health and milk production will be. In general, CNS infections are cleared early in lactation and some studies show that CNS do not have a large impact on future milk production and udder health. Future research should elucidate to what extent pathogen-specific as well as host-related factors affect the persistence of IMI in early lactating heifers.  相似文献   

7.
Factors affecting bacteriological cure rates (BCR) and new intramammary infections (IMI) during the dry period as well as clinical mastitis (CM) during early lactation were investigated in 414 German Holstein dairy cows receiving dry cow therapy. Cows were treated with either benethamine benzylpenicillin (300,000 IU), penethamate hydriodide (100,000 IU), and framycetin sulphate (100 mg, n = 136), or cefquinome (150 mg, n = 135), or benzathine cloxacillin (1,280 mg, n = 143). Overall BCR, IMI, and CM at parturition were 86.4%, 20.7%, and 4.3%, respectively. The three antibiotic treatments differed only in BCR, with cloxacillin yielding better results than the others. Udder quarters from cows with > 4 lactations had a higher risk of IMI and CM at calving. Chronic changes in udder tissues were linked to a lower BCR and were associated with a higher risk of CM during early lactation. The risk of CM at calving was higher in udder quarters with unspecific or subclinical mastitis before drying off. In conclusion, with antibiotic dry cow therapy, age and health status of the udder appear to be major determinants of IMI and CM during the dry period and early lactation, while BCR was associated with the antibiotic type and udder tissue status.  相似文献   

8.
To study vitamin A transport in dairy cows and heifers around parturition, an enzyme immunoassay for bovine retinol binding protein (RBP) was developed and serum levels determined. Serum and liver concentrations of retinol were assayed by HPLC. Four weeks before expected calving the cows and heifers were divided into two groups each, and half of the animals received a protein supplementation during the dry period.The mean serum RBP concentration 4 weeks before calving was 42 mg l-1 for the cows and 44 mg l-1 for the heifers. The serum retinol concentrations were 0.53 mg l-1 for the cows and 0.42 mg l-1 for the heifers, and the liver retinol concentrations 0.30 mg l-1 and 0.13 mg g-1, respectively. In the groups without protein supplementation there was a significant decrease in serum RBP at sampling 1 week before parturition compared to initial values. The measurement of serum RBP may prove useful in assessment of amino acid availability in dairy cows.  相似文献   

9.
A clinical trial was conducted to determine whether prepartum intramammary pirlimycin reduces the proportion of nulliparous heifers with intramammary infection (IMI) during early lactation and improves milk production. Quarter milk samples were collected from 428 heifers, systematically allocated to treatment and control groups, 6 to 12 d before the expected calving date and 2 to 8 d after calving. At the prepartum visit, heifers in the treatment group (n = 219) received an infusion of pirlimycin hydrochloride in all 4 quarters; the control heifers (n = 209) received no infusions. Intramammary infection was detected in 69% of the heifers and 33% of the quarters before calving. After calving, the proportion of treated heifers with IMI was significantly lower than the proportion of control heifers (31% versus 45%). Staphylococcus aureus was isolated from 10% of the heifers and 3% of the quarters before calving. After calving, the proportion of IMIs due to S. aureus was significantly lower in the treated heifers than in the control heifers (5.6% versus 10%). Antibiotic treatment increased the percentage of cures and prevented new IMIs caused by gram-positive bacteria after calving. The incidence of new IMIs caused by gram-negative bacteria and yeast was higher among treated heifers than among control heifers. There was no overall effect of treatment on milk production, but there was a significant interaction effect of treatment and the interval between treatment and calving. An increase of 302 kg of milk was observed when antibiotic treatment was applied more than 1 wk before calving. Treatment did not affect the milk somatic cell count on the 1st 3 test days after calving.  相似文献   

10.
Infections were induced at the end of lactation in all udder quarters of 19 cows by the infusion of 0.2 mL of a 10-4 dilution in milk of a six hour milk culture of Staphylococcus aureus, strain 305 (A.T.C.C No. 29740). Two right or two left udder quarters were infected at 15 days and the opposite two five days before the last milking of lactation. Following the last milking all four udder quarters of eight cows were treated with 400 mg novobiocin in 10 mL of 2% aluminum monosterate in peanut oil, gelled. All udder quarters of eight other cows were treated with 50 mg novobiocin in the same vehicle and the udder quarters of three cows were treated with the vehicle only.

At calving, eight of 32 quarters treated with 400 mg novobiocin were still infected, as were 18 of 32 treated with 50 mg of novobiocin and all those quarters treated with vehicle only. Results were identical from udder quarters infected 15 and five days before drying off.

No significant differences were found between quarters in milk yield on the last day of lactation, nor the length of the dry period. An increasing number of udder quarters were infected at calving with increase in lactation age of the cow, although the small number of cows would not allow a firm conclusion. A significant difference in results was found between front and hind udder quarters, only five of 32 front quarters were infected at calving as compared to 21 to 32 hind quarters.

The method proposed was found to give essentially the same results as those from a large field trial using the same antibiotic. It should therefore be useful in evaluation trials of new antibiotic products for dry cow treatment.

  相似文献   

11.
Quarter samples (n = 6,328) of mammary secretions were collected from 160 cows during physiologic transitions of the udder to determine the frequency of isolation of mastitis-causing pathogens and the incidence of new intramammary infections (IMI) during the nonlactating period. None of the cows in the herd was infected with Streptococcus agalactiae, and the prevalence of Staphylococcus aureus was low. Cows were not treated with antibiotics at cessation of milking. A threefold increase in the percentage of quarters infected with major mastitis-causing pathogens developed from late lactation to early involution. Coliforms and streptococci other than Str agalactiae accounted for 94% of major pathogen infections. The number of quarters infected with coagulase-negative staphylococci increased slightly from late lactation to early involution, whereas the number of quarters infected with Corynebacterium bovis decreased markedly. Major pathogens caused 101 of 153 IMI at parturition and greater than 90% were caused by streptococci and coliforms. At parturition, 51 of 52 minor pathogen IMI were caused by coagulase-negative staphylococci. During early lactation, there was a marked decrease in quarters infected with major pathogens; however, the number of quarters with major pathogen IMI during early lactation was 2.3 times higher than the number of quarters infected before cessation of milking. The number of quarters with minor pathogen IMI during early lactation was the same as at parturition, but a marked decrease in quarters infected with coagulase-negative staphylococci and a marked increase in C bovis IMI developed from parturition to early lactation.  相似文献   

12.
Prevention of heifer mastitis is a key element in preventing mastitis. Since pathogenesis of heifer mastitis is not fully understood yet, combating it is arduous. The goal of this study was to examine whether the premature loss of the keratin plug of the teat canal represents an important risk factor for the development of heifer mastitis. 84 dairy heifers (German Holstein) from six high-yielding dairy herds in Northern Germany were examined between March 2005 and June 2006. Each quarter was examined clinically at least three times before calving. If the teat canal of a quarter was open, secretion samples were collected for bacteriological analysis. After calving, four quarter samples were collected during the first lactation. A rapid increase of the proportion of open teat canals was detected in the preparturition period. No teat canals were open till 80 days before parturition, while 60% of the teat canals were open at 60 days before parturition. A time-scheduled infection pattern was observed: during the days 90-61, 60-31, and 30-0 before calving, skin inhabitants (coagulase-negative staphylococci, coryneform bacteria), cow-related, and environment-related microorganisms prevailed, respectively. A total of 77% of intramammary infections encountered at parturition had established previously. No significant association between the duration of open teat canals before calving and the udder health post partum was found. However, the incidence of clinical mastitis during first lactation was influenced largely by the duration of infection ante partum and the mastitis pathogen involved. This study shows that a high proportion of teat canals already opens several months before calving and that opening of the teat canal before calving is an important factor in the aetiology of heifer mastitis.  相似文献   

13.
All the quarters in the cows with high somatic cell counts in 10 herds were treated at drying off with either 600 mg cloxacillin or 600 mg cloxacillin and 4 g of an internal teat sealant containing 65 per cent bismuth subnitrate. The quarters were sampled daily for bacteriological tests for the three days before drying off and twice after calving to establish whether they were infected. Clinical mastitis cases were monitored from drying off until 100 days after calving. The odds of a quarter being bacteriologically negative after calving or developing clinical mastitis in the first 100 days after calving were investigated by multilevel logistic regression. The quarters treated with the internal sealant and cloxacillin were significantly more likely to be bacteriologically negative in the immediate period after calving and were significantly less likely to suffer clinical mastitis during the first 100 days after calving than the quarters treated with cloxacillin alone. There was more variation between cows than between herds in the underlying risk of an infection after calving, but there was more variation between herds than between cows in the underlying risk of clinical mastitis during the 100 days after calving.  相似文献   

14.
The effect of an autogenous vaccine against Staphylococcus aureus on S. aureus prevalence and mastitis, as well as on somatic cell count (SCC), was studied in a dairy herd with a high prevalence of S. aureus. The vaccination group (n = 35; 22 cows and 13 heifers) and the control group (n = 36; 23 cows and 13 heifers) received the vaccine or a placebo, respectively, according to the following protocol: all animals: basic immunization (twice, 3 weeks apart); cows: booster dose at the time of drying off, 5 and 2 weeks before calculated calving date; heifers: booster dose 2 and 5 weeks before calculated calving date. The vaccine or the placebo was administered subcutaneously in the area of the supramammary lymph nodes. Quarter milk samples were collected monthly and subjected to SCC and bacteriological evaluation. At this time, the animals were also checked for signs of clinical mastitis. Non-clinical S. aureus mastitis diagnoses were based on udder quarter SCC and a positive S. aureus culture. In order to compare the SCC in individual whole milk samples, records from the monthly milk quality testing were evaluated. Cow and udder quarter prevalence of S. aureus intramammary infections calculated for the experimental animals and quarters, respectively, did not differ between groups. However, during the lactation period following the boostcr dose, the prevalence of S. aureus increased in both groups (P < 0.05). The cumulative incidence of various mastitis diagnoses (clinical, subclinical, latent infection) due to S. aureus on an animal basis did not differ between groups. On an udder quarter basis, the cumulative incidence of subclinical mastitis was higher in vaccinated animals than in control animals (33.8 versus 26.0%; P < 0.05). This was mainly due to a higher cumulative incidence of subclinical mastitis in vaccinated than control heifers. The SCC in composite milk samples did not differ between groups, but increased as lactation progressed. The herd prevalence of S. aureus differed considerably throughout the study period, but declined consistently to below 10% at the end of the study period. Recent herd checks revealed a prevalence of S aureus infections of < 5%. It is concluded that the autogenous bacterin tested in this study did not have the desired effect on the prevalence of S. aureus infections and mastitis or SCC. The decline in S. aureus prevalence was very probably due to other factors than specific immunization against S. aureus.  相似文献   

15.
Precise calving monitoring is essential for minimizing the effects of dystocia in cows and calves. We conducted two studies in healthy cows that compared seven clinical signs (broad pelvic ligaments relaxation, vaginal secretion, udder hyperplasia, udder edema, teat filling, tail relaxation, and vulva edema) alone and in combination in order to predict the time of parturition. The relaxation of the broad pelvic ligaments combined with teat filling gave the best values for predicting either calving or no calving within 12 h. For the proposed parturition score (PS), a threshold of 4 PS points was identified below which calving within the next 12 h could be ruled out with a probability of 99.3% in cows (95.5% in heifers). Above this threshold, intermitted calving monitoring every 3 h and a progesterone rapid blood test (PRBT) would be recommended. By combining the PS and PRBT (if PS ≥ 4), the prediction of calving within the next 12 h improved from 14.9% to 53.1%, and the probability of ruling out calving was 96.8%. The PRBT was compared to the results of an enzyme immunoassay (sensitivity, 90.2%; specificity, 74.9%). The standard operating procedure developed in this study that combines the PS and PRBT will enable veterinarians to rule out or predict calving within a 12 h period in cows with high accuracy under field conditions.  相似文献   

16.
The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.  相似文献   

17.
Heifers managed under pastoral conditions are at risk from Streptococcus uberis mastitis infections at calving. A total of 397 heifers from six farms around New Zealand were enrolled in a study to identify and enumerate S. uberis on teat-ends of heifers in the peri-partum period, and to understand the effect of teat-spraying in the pre-calving period on the prevalence and incidence of S. uberis mastitis post-calving. Heifers were randomly assigned to Control or Sprayed groups. Sprayed heifers were teat-sprayed once, three times a week (Monday, Wednesday and Friday) with a commercial iodine-based teat sanitizer, starting at 3 weeks prior to calving and ending at day of calving. Across three farms, all glands of cows in both groups were sampled at calving to determine S. uberis intra-mammary infection (IMI) prevalence. For all farms, clinical mastitis (CM) cases detected during the week after calving were sampled and submitted for bacteriological analysis. Swabbing of teat-ends of 54 heifers from one farm showed that heifers had a pre-existing S. uberis contamination averaging 610 colony-forming units per swab (cfu/swab), at 3 weeks prior to calving. At calving, teat-end contamination was 560 cfu/swab for Sprayed heifers and 1775 cfu/swab for Control heifers. Two weeks after calving, teat-end contamination was similar between both groups, at 30 cfu/swab. The prevalence of S. uberis IMI was significantly lower in the Sprayed (3.5% glands) vs. the Control (7.4%) heifers in the first week after calving. There was a trend for Sprayed heifers (3.6% heifers) to have a lower incidence of S. uberis CM compared with Control heifers (7.4% heifers). It is concluded that teat-spraying in the dry period is a management option that could contribute to controlling heifer S. uberis mastitis in the transition period.  相似文献   

18.
The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.  相似文献   

19.
Thyroxine (T4) and cholesterol concentrations and their dynamic changes and differences were studied in 20 pregnant heifers 10 days before calving until 56 days after calving. Ten control heifers were fed the feed ration for pregnant heifers according to Czechoslovak Standard CSN 46 7070. The feed ration given to another ten (experimental) heifers was fortified with 300 mg of synthetic beta-carotene per head/day within the period of five months before insemination, during pregnancy and till the 56th day after parturition. As suggested by the regression function of straight line, no obvious differences were recorded in the dynamic changes of T4 before parturition and during the first days after parturition. T4 concentrations had a generally descending tendency in both groups, the lowest values being recorded in the 48th hour in the experimental group and the 24th hour in the control. A marked increase of T4 concentrations with the values significantly higher in the control group than in the experimental group was observed between the 21st and 35th day after calving. A medium increase of cholesterol concentrations was found in the heifers given rations fortified with beta-carotene. No significant differences in cholesterol concentrations were observed between the two groups, except in the 72nd hour and the seventh day. Significant T4: cholesterol correlations were recorded in the experimental animals in the first and second hours, on the 42nd day (P less than 0.05), and in the 72nd hour (P less than 0.001); in the control group these observations were made the seventh day before calving and in the sixth hour and on the 14th, 21st and 56th days (P less than 0.05) after calving. It is inferred from the results that beta-carotene interferes with the activity of the thyroid gland and the production of its hormones, and that the increases or decreases of the activity of this gland, caused by beta-carotene, influence the metabolism of cholesterol in the body.  相似文献   

20.
This study was performed to examine the bacteriological findings in 58 mammary secretions from 15 heifers at 4-5 weeks before parturition, and to evaluate whether a high prevalence of S. aureus infection in lactating cows affects the occurrence of S. aureus infection in prepartum heifers in the dairy herd. A total of 86.7%(13/15) of the heifers and 60.3%(35/58) of quarter milk samples from the heifers were bacteriologically positive. No S. aureus isolate was detected in mammary secretions from the heifers. Coagulase-negative staphylococcus (CNS) species were predominantly detected in 54.3%(19/35) and Streptococci other than Streptococcus agalactiae were isolated from 22.9%(8/35) of the quarters. A high S. aureus prevalence in the herd may not necessarily be a decisive factor for S. aureus infection in heifers.  相似文献   

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