California Dairy Research Articles

Financial Analysis of Alternative Treatments for Clinical Mastitis Associated with Environmental Pathogens

For two large California dairy herds with twice daily milking, 171 infected quarters of lactating cows with mild clinical mastitis were randomly assigned to one of three treatment groups. Group A (50 cows) was treated with 62.5mg of intramammary amoxicillin every 12h for three milkings. Group C (50 cows) was treated with 200mg of intramammary cephapirin every 12h for two milkings. Group O (71 cows) was treated with 100 U of intramuscular oxytocin every 12h for three milkings. Clinical cure rates did not differ among treatment groups. The cost per episode of clinical mastitis was higher ($54.47) for group C than for groups A ($38.53) or O ($34.88). Group O had a higher incidence of relapse (41%), and a greater percentage of group O cows (65%) experienced an additional mastitic event in the enrolled lactation than did cows in groups A and C. Treatment had no effect on the mean number of nonsalable milkings (24.7) associated with mastitis in the lactation interval subsequent to enrollment on the trial. Twenty-two percent of the cows accrued more than 30 nonsalable milkings and produced 55% of the total nonsalable milkings associated with mastitis. There was no treatment effect on total milk production, fat production, or time to removal of the enrolled cows from the herd.

Survey of Intramammary Infections in Dairy Heifers at Breeding Age and First Parturition

A survey was conducted to determine and contrast prevalence of IMI in nulligravid and primigravid dairy heifers pre- and postpartum. Contrasts were made to evaluate the risk factors of location of dairy, trimester of gestation, and season of sampling on IMI. Twentyeight dairies in California, Louisiana, Vermont, and Washington were studied. Lacteal secretions were collected aseptically from heifers at breeding age (8 to 19 mo) from one side of the gland and again at 4 d postpartum from all quarters. Of the quarters sampled, 65.6% prepartum and 64.0% postpartum were free of IMI. The percentages of quarters with IMI from coagulase-negative staphylococci or Staphylococcus aureus IMI were 27.1 and 9% prepartum and 21.8 and 2.9% postpartum. Staphylococcus aureus IMI were most prevalent in Louisiana during the months other than summer. Location, herd, and season significantly influenced prevalence of IMI. The prevalence of IMI was greatest during the last trimester of pregnancy, ranging from 49.2% in the winter to 36.8% in the summer. The significant effects of herd location and season suggest that management variables influence prevalence of heifer IMI. Because prevalence of IMI was greatest during the last trimester of pregnancy compared with prevalence during earlier stages of pregnancy, the heifer may be most susceptible to this disease during this period of first gestation.

Secular and Seasonal Trends of Neospora Abortion in California Dairy Cows

This study was undertaken to determine if the proportion of dairy cow abortions attributable to Neospora sp. infection increased or occurred in a seasonal cycle during a 6-yr period. Abortions caused by Neospora sp. were tallied for all fetuses submitted to the Tulare branch of the California Veterinary Diagnostic Laboratory between January 1985 and December 1990. Regression analysis of 221 cases of Neospora among 762 fetuses submitted showed a weak increasing secular trend (P = 0.053, r2 = 0.05), with predicted monthly proportions at the beginning and end of the 6 yr of 0.16 and 0.33, respectively. Using a Kolmogorov-Smirnov-type statistic, comparison of the 12-mo distribution of Neospora sp. cases and a hypothetical distribution of cows at risk of aborting found about 16% of variation in cases was attributable to season (P < 0.01). More cases were found in winter than in summer and early fall. Results indicate that Neospora sp. abortion in California dairy cows is not new or recently emerging and that seasonally related factors influence some of the risk of abortion. Results suggest that Neospora sp. has contributed to the high dairy cow abortion rate for many years, and that seasonally varying exposures may predispose to transmission or recrudescence of infection.

Flight activity and response to carbon dioxide of Culicoides variipennis sonorensis (Diptera: Ceratopogonidae) in southern California.

Adult Culicoides variipennis sonorensis Wirth & Jones were collected using miniature suction traps during 12 nights in October and November at a southern California dairy. Traps were baited with carbon dioxide at a constant release rate of 300, 1,000, or 3,000 ml/min or with 1.3 kg of dry ice. The release rate of CO2 from the dry ice in the laboratory declined from 1,486 ml/min during the first 2 h to 303 ml/min after 10-12 h. Nulliparous and parous females responded in a similar and positive manner to increasing CO2 release rates. An automatic interval suction trap baited with CO2 was used to assess diel host-seeking periodicity. Peak host-seeking activity occurred 0-3 h after sunset, when the trap collected up to 170 females or 103 males per hour. Average peak time of collection during the dusk period was 45 min after sunset. Although numbers were lower, parity was higher in the middle of the night. A smaller, secondary peak of activity occurred near sunrise.

Quantity and Economic Importance of Nine Selected By-products Used in California Dairy Rations

Food processing representatives, brokers, nutritionists, livestock producers, and trade associations were surveyed to quantify 9 by-products used for feeding livestock during 1992 in California. The commodities were almond hulls, dried beet pulp, wet brewers grains, wet citrus pulp, pressed citrus pulp, wet corn gluten feed, corn gluten meal, whole cottonseed, and rice bran. The 9 byproducts contributed over 2.5million tonnes and about 27% of the total feed concentrate moved within California during 1992. Market value of these 9 byproducts was almost .25 billion dollars. Whole cottonseed accounted for about 31% of the total tonnage of these 9 byproducts and provided about 66% of the total CP and 53% of the total NEL of these 9 by-products. The by-products were more valuable as energy sources than CP sources compared with NEL from corn and CP from soybean meal, respectively. Calculations of milk production, based on the CP content or NEL content of the by-products, showed that these 9 by-products could have contributed sufficient CP or NEL for over 31% of the milk produced in California during 1992. Ration formulations demonstrated that the economic value of by-products changed with feedstuffs available and, in general, would be used in rations over a range of market prices.

Octenol fails to lure stable fly to insecticide

A study was designed to determine whether blue targets were attractive to stable flies, whether octenol, a natural component of cow breath, enhanced attraction, and whether treating these targets with insecticide might enhance stable fly control. Blue cylindrical cloth targets treated with insecticides attracted resting stable flies in Southern California dairies. Octenol did not increase this attraction to the targets. Targets did not result in fewer flies in treated dairies, possibly due to insecticide resistance in these flies and the relatively small proportion of flies attracted.

Prevalence of salmonellae in cattle and in the environment on California dairies

Summary Milk samples were collected from all lactating cows on 60 dairies (mean number of cows/dairy, 584; range, 66 to 2,834) randomly selected from 701 California dairies enrolled in the Dairy Herd Improvement Association program. Samples were tested, by means of an elisa, for antibodies against Salmonella serogroup B, C1, and D1 antigens (somatic antigens 01, 4, 6, 7, 9, 12). Blood samples were collected from all cows with positive results and tested for serologic evidence of exposure to salmonellae. Samples for bacteriologic culture (pooled feces from 20 randomly selected calves, swabs of wet areas and feces from calf pens and dairy hospital pens, drag swab sample from wastewater lagoon, and samples of feed components) were also collected from all 60 dairies. Seven (11.7%) of the 60 dairies each had 1 sample that yielded Salmonella organisms (3 S typhimurium, 1 S dublin, 1 nonmotile Group D salmonella, 1 S derby, and 1 S oranienberg). Five of the Salmonella isolates came from the hospital pens and 2 came from calf pens. Thirty-three dairies did not vaccinate cattle against salmonellosis, and of these, 24 (72.7%) had ≥ 1 seropositive cow (titer ≥ 200), and 20 (61 %) had ≥1 persistently seropositive cow (titer for each of 2 blood samples collected ≥ 60 days apart was ≥ 200). Of the 27 dairies that did vaccinate cows against salmonellosis, 24 (89%) had ≥ 1 seropositive cow, and 21 (78%) had ≥ 1 persistently seropositive cow. We concluded that studies that use of bacteriologic culture of fecal and environmental samples to determine the percentage of dairies with Salmonella-infected cows may underestimate the true percentage.

For wages and benefits, bigger dairies may be better

California recently surpassed Wisconsin as the nation's number-one dairy state. To be productive, California's dairies rely heavily on hired labor. However, wages and benefits offered to dairy employees are highly variable. Herd managers and milers earn more on larger dairies. Union employees out-earn their non-union counterparts in wages and benefits. Although managerial treatment of employees is not highly variable, some practices such as team training or providing continuing education may influence herd productivity. Well-trained employees may increase herd productivity through improving disease detection and prevention, and increasing the effectiveness of breeding and nutrition programs.

Financial analysis of a clinical trial comparing simple estrus detection with estrus detection after prostaglandin-based appointment breeding in a commercial dairy herd in California, USA

An economic analysis of the outcomes from a clinical trial on dairy cow reproduction was performed. The trial compared two prospective cohorts from a California dairy herd of 670 cows: (1) a cohort of 56 cows initially treated with prostaglandin-F2α and appointment inseminated at 72 and 96 h post-treatment, followed in 7 days by estrus detection based breeding (PT); (2) a cohort of 53 cows that was managed strictly for estrus detection based breeding (HD). There were no significant differences between the cohorts for days in milk at conception, services per conception, or time to events. The economic analysis consisted of three parts: (1) a partial budget analysis of the two breeding strategies; (2) a deterministic decision analysis of the two practices; (3) a stochastic evaluation of the strategies. Both the deterministic and stochastic analyses used time value of money calculattions PT insemination cost the farm approximately $32 compared with an HD cost of approximately $17. However, the costs of getting the average animal pregnant were approximately respectively. Expected monetary values were $588 and $707 for PT and HD strategies, respectively. The stochastic decision analysis evaluated risks and return over 1000 simulations. It suggested that in 73% of cases an HD strategy will produce expected monetary values $170 more than the PT strategy, in 10% of cases the two will be within 4% in yield, and in 17% the PT strategy will yield $95 more than an HD program. Sensitivity analysis suggested that conception rates to estrus detection based breedings are not likely to alter the decision. However, conception rates to the appointment breeding program in conjunction with the elapsed time postpartum when the decision to breed is implemented and estrus detection rates can cause the PT strategy to be optimal. Situations where this might occur are discussed.

Efficacy of Intramammary Antibiotic Therapy for Treatment of Clinical Mastitis Caused by Environmental Pathogens

For three California dairy herds with bulk tank SCC <200,000/ml, twice daily milking, and no mastitis vaccine, 254 quarters with mild clinical mastitis were randomly assigned to three groups. Group A (n = 74) was treated with 62.5mg of intramammary amoxicillin every 12h for three milkings. Group C (n = 75) was treated with 200mg of intramammary cephapirin every 12h for two milkings. Group O (n = 105) was treated with 100 units of intramuscular oxytocin every 12h for two or three milkings. Aseptic pretreatment quarter samples revealed 94 (37%) coliforms, 65 (26%) environmental streptococci, 34 (13%) other bacteria, and 61 (24%) with no isolate on bovine blood agar plates. Contagious pathogens were not isolated. Clinical cure (return of quarter and milk to normal) and bacterial cure (absence of primary pathogen isolated pretreatment) were assessed at milking 8 and d 20 after initial treatment. No difference existed in clinical (67.6, 67.7, or 66.7%) or bacterial (43.9, 55.0 or 49.1%) cure rate among groups. Clinical cure rates did not differ when quarters were grouped by etiology, but clinical cure rates for quarters with pathogens other than streptococci or coliforms were lower in group O.

Isolation of multiple Salmonella serovars from a dairy two years after a clinical salmonellosis outbreak

Summary Samples were obtained for bacteriologic culturing of salmonellae from cows and calves on, and the environment of, a large California dairy that used free-stall housing and a flush system for manure handling. Two years previously, the dairy had an outbreak of clinical salmonellosis in the lactating herd; however, since that time, it had not had problems with clinical salmonellosis. On the basis of mean annual milk production per cow, this dairy was consistently ranked in the top 25% of dairies in the area enrolled in the Dairy Herd Improvement Association. Results of bacteriologic culture of 76% (108/142) of environmental samples and 48% (639/1,339) of fecal samples were positive for salmonellae. Eighty-two percent of the isolates were serovar C1, subclassified as Salmonella montevideo, and 17% were serovar E. Results of bacteriologic culture of 85% of samples of recycled flush water being pumped into the free-stall alleys were positive, as were results of bacteriologic culture of 78% of samples of herd bulk milk filters, 97% of fecal samples collected from calves being fed nonsalable milk, and 25% of fecal samples collected from cows at the time of breeding. These findings suggest that freedom from clinical salmonellosis and comparatively high measures of herd performance do not indicate the absence of salmonellae from a premises, and that hardy infectious agents transmitted by ingestion of feces can become established in the environment of modern free-stall dairies that use recycled water in their manure flush systems.

Summary of Conclusions from a Consensus Panel of Experts on Health Attributes of Lactic Cultures: Significance to Fluid Milk Products Containing Cultures

A panel of experts sponsored by the California Dairy Research Foundation was convened on January 31, 1992 to discuss the effect of the consumption of lactic cultures on human health. The panel was composed of 10 scientists with diverse applicable specialties. Topics discussed included lactose digestion, diarrheal diseases, chronic kidney disease, cancer, adherence, immune system stimulation, cholesterol reduction, constipation, and safety. Legitimacy of health claims and research needs for these areas were determined. The panel noted the promising results in the areas of positive effects of ingestion of lactic cultures on lactose digestion, some diarrheal illnesses, small bowel overgrowth associated with chronic kidney disease, and reduction of fecal enzymes that may play a role in colon cancer. However, additional research is necessary to confirm the effects in all of these areas. A coordinated research effort between microbiologists and clinicians is essential for the most effective research to ensure the choice of best available strains, the best conditions of analysis, and the best clinical models.

Effects of a high-density intramammary device on mammary glands, production, and reproductive performance in dairy cows

Summary A clinical field trial was undertaken to determine the influence of an intramammary device (imd) on environmental mastitis and production. On 4 central California dairies, 200 Holstein first-lactation cows were randomly assigned to 2 groups. Cows in the treatment group were fitted with an imd, and cows in the control group were not. The incidence of clinical mastitis for the 2 groups was determined during the study period. Bacteriologic monitoring at intervals over 2 lactations (lactation 2 and through 60 days of lactation 3) was used to determine the incidence of subclinical infection. In addition, data were collected to determine whether the groups differed in milk production, butterfat production, postmilking and test-day somatic cell counts, and reproductive efficiency. Total milk production and butterfat production over the 2 lactation periods did not vary significantly between the groups. Also, the groups did not differ in calving-to-conception interval, duration of lactation, calving interval, and calving-to-first service interval. Cows with imd were significantly less likely to develop clinical mastitis (5% vs 13%) than control cows. The imd did not appear to affect subclinical infection rates (minor pathogens only) except at day 300 of lactation 2 and at day 10 of lactation 3, when prevalence was greater in the cows with imd. The minor pathogens were predominately (80%) coagulase-negative staphylococci. It was unusual to have coagulase-negative staphylococci in the same quarter at 2 consecutive samplings, prompting the speculation that during lactation, the duration of coagulase-negative staphylococci infection is short (resolves without intervention). However, new infections developed in other quarters, thus maintaining a consistent quarter prevalence throughout the lactation. The imd induced a significant increase in postmilking somatic cell count, compared with results from control cows, and test-day somatic cell count had a more modest increase in cows with imd, compared with previous studies.

The association between antibody titres against Campylobacter fetus and milk production efficiency in dairy cattle.

The association between serological evidence of exposure to Campylobacter fetus and milk production performance was studied in 178 lactating cows from three California Dairy Herd Improvement Association herds using a cross-sectional study design in December 1986. ELISAs were used to determine the antibody titres against Campylobacter fetus, Haemophilus somnus and Leptospira hardjo, which were classified as either negative or positive. The status of a cow as negative or positive against C. fetus and H. somnus represents the serological evidence of natural exposure to the corresponding bacteria. However, the status against L. hardjo was assumed to be the level of vaccinal titre against this organism since all the cows studied had been vaccinated against this agent. The data on demographic and productivity variables relating to the current lactation of the cows were obtained from Dairy Herd Improvement Association individual cow records for December 1986. Four measures of milk production efficiency for the current lactation were used. The status against L. hardjo and other covariates suggested by previous studies were included in modelling the relationships of interest. Stepwise multiple linear regression was used to study the adjusted relationship of C. fetus with each measure of milk production efficiency. Multivariate analyses revealed that the adjusted relationships of C. fetus with the test-day's milk production, the extended 305-day milk production and the relative value of milk production were not significant (p > 0.1). However, after adjusting for possible covariates, C. fetus-positive cows had an average of 7.43% lower mature equivalent milk production than C. fetus-negative cows (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Randomized field trial to determine the effects of oral selenium supplementation on milk production and reproductive performance of Holstein heifers

Summary: A field trial was conducted to measure differences in performance between selenium-supplemented and nonsupplemented heifers on a 1,200-cow California dairy. One hundred seventeen 19- to 27-month-old Holstein heifers were randomly assigned to treatment (n = 59) and control (n = 58) groups. A federally approved, commercially available, sustained-release intraruminal selenium bolus was administered to each heifer in the treatment group. Blood samples were taken from treated and control animals to assess selenium values before and after bolus administration and again after introduction to the milking ration. Production data were obtained from an on-farm computerized record system for each heifer during her first lactation. Mean blood selenium concentrations in treated heifers were higher than those in control heifers from posttreatment day 30 until after calving. Data analyzed in midlactation and late lactation indicated no significant differences between treated and control groups in somatic cell count, days not pregnant, total milk produced, or times bred.

The association between antibody titres against Campylobacter fetus and reproductive efficiency in dairy cattle.

The relationship between the antibody titres against Campylobacter fetus and various indices of reproductive efficiency was studied in a cross-sectional study of 178 dairy cows from three California Dairy Herd Improvement Association herds. Blood samples were collected from the lactating cows during December 1986. Enzyme-linked immunosorbent assays were used to determine the antibody titres of the cow against Campylobacter fetus, Haemophilus somnus and Leptospira hardjo and were classified as either negative or positive. The status of a cow as either negative or positive against Campylobacter fetus and Haemophilus somnus represents serological evidence of natural exposure to the corresponding bacterial agents. However, the status against Leptospira hardjo was assumed to reflect a vaccinal titre since all the cows studied had been routinely vaccinated against this organism in September 1986. The data on demographic and reproductive parameters pertained only to the current lactation of the cows and were obtained from Dairy Herd Improvement Association individual cow records of December 1986. Five indices of reproductive efficiency were used, namely the recent calving interval, the calving-to-conception interval, the calving-to-last-service interval, the number of services per conception, and the number of services since last calving. The serological status against Haemophilus somnus, Leptospira hardjo and other covariates suggested by the results of previous studies were included in modelling the relationships of interest. Stepwise multiple linear regression analyses were carried out to study the adjusted relationship of Campylobacter fetus with each measure of reproductive efficiency. Multivariate analyses revealed that the adjusted relationship for Campylobacter fetus with all five measures of reproductive efficiency was non-significant (p > 0.05). Among the covariates, Leptospira hardjo had a strong and independent relationship with recent calving interval, the unstandardized partial regression coefficient being -0.77. The possible biological mechanisms of these associations are discussed.

Risk factors associated with the incidence of seroconversion to caprine arthritis-encephalitis virus in goats on California dairies

Summary Incidence of seroconversion to caprine arthritis-encephalitis virus (caev) was determined for 1,194 goats on 11 dairies, using 2 repeated annual herd tests for caev. Current life table methods were used to compare age-specific incidence of seroconversion for pasteurized milk-raised and unpasteurized milk-raised goats. Logistic regression models were used to determine the risk factors associated with caev seroconversion, and to estimate odds ratios for seroconversion for various factor levels. Goats raised by unpasteurized milk-feeding methods were 2.5 to 6.7 times more likely to seroconvert than were goats raised by pasteurized milkfeeding methods, depending on the method of comparison. Similarly, 61.6 to 85.0% of seroconversions in yearling goats possibly were attributable to unpasteurized milk feeding. Among yearling goats, caev seroconversion was associated with feeding method, breed, and source of goat (herd of origin) when the effect of dairy was considered. In addition to the 6.7 times greater risk of seroconversion for unpasteurized milk-raised goats, yearling goats of the Saanen and Toggenburg breeds were 2.2 and 3.3 times, respectively, more likely to seroconvert than were Alpine yearling goats. Yearling goats purchased from another source were less likely to seroconvert than were yearlings raised on the dairy where they were studied. Among goats &gt; 1 year old, age was associated with risk of seroconversion. Goats that were 3 years old or were ≥ 4 years old were 1.7 and 3.2 times, respectively, more likely to seroconvert than were 2-year-old goats, when adjusted for effect of dairy. The effects of dairy were significant (P ≤ 0.001) in yearling and older goats.

Cohort study of natural transmission and two methods for control of caprine arthritis-encephalitis virus infection in goats on a California dairy

Summary A prospective observational cohort study of 361 dairy goat kids was conducted to compare 2 methods of controlling caprine arthritis-encephalitis virus infection under commercial dairy conditions. To compare effectiveness of feeding kids pasteurized milk vs serologic testing and segregation in addition to pasteurized milk feeding, goats were monitored up to the age of 30 months by use of monthly agar gel immunodiffusion testing. Survival analysis methods were used to determine whether age at seroconversion differed between the 2 groups. Significantly lower rates of seroconversion were observed in the segregated group (P &lt; 0,001), compared with the nonsegregated group. Of 193 goats in the pasteurized milk-only group, 146 (75.6%) seroconverted within the 30-month study period, whereas infection was detected in 39 (23.2%) of 168 goats in the test/segregated group. Nonsegregated goats were 3.37 times more likely to seroconvert by 24 months of age, and 70.3% of seroconversions by 24 months of age could be attributed to nonsegregation. For age-specific intervals beyond 180 days of age, 70 to 100% of seroconversions could be attributed to lack of segregation. Cohort life tables for age at seroconversion were reported for each group. Type of colostrum fed, sex, and weaning group (season) were not significantly associated with age at seroconversion. Saanen goats had lower age-specific risk of seroconversion in the nonsegregated group alone and overall. Non-Saanen goats were 1,5 times more likely to seroconvert than were Saanen goats, when adjusted for a possible confounding effect of weaning group. Results indicate that pasteurized milk feeding and routine test and segregation would be a substantially more effective means of control of the disease in dairy goat herds than would pasteurized milk feeding alone.

Prospects for Salmonella Control in Cattle

Salmonella infections appear to be increasing in animals and humans at a time in history when many other infectious diseases are being satisfactorily controlled (I). There have been large and well publicized outbreaks of human salmonellosis (2-5), and an increase in the number of isolations reported from both animals (6) and humans (7). While there are over 2200 serotypes of Salmonella recognized, the good news is that 5 or 6 serotypes consistently cause most of the problem in cattle. These serotypes are S. typhimurium, ,S. dublin, S. newport, S. montevideo, and S. anatum. A recent survey employing serologic methods found that over 70% of dairies in California had evidence of Salmonella infection (8). In order to examine the prospects for control of Salmonella in cattle, one must try to understand why this high prevalence rate of Salmonella infection exists

Weed seed in dairy manure depends on collection site

Dairy manure collected for 2 years from various sites in seven Central California dairies was found to contain viable weed seed. Weed seed Contamination Was most Severe when manure was taken from dry COW pens and liquid manure sedimentation handling facilities. Composting did not eliminate all viable weed seed.