Effect of nematode infections on growth performance of calves after stabling on commercial dairy farms

Growth performance of calves was assessed on 32 farms during winter housing. Nematode infection was measured by antibody titres, pepsinogen values, and faecal examinations. Half of each herd was treated with ivermectin after stabling. Treatment significantly increased growth rate by an average of +0.059 kg day-1 (P less than 0.01). The effect of treatment varied among herds from -0.078 to +0.210 kg day-1. Only a few of the infection parameters correlated weakly, but positively, to the effect of treatment on growth performance per herd. Untreated control groups showed very different growth rates among herds, ranging from 0.250 to 0.936 kg day-1. This was strongly correlated to several infection parameters. Groups with the highest values for the infection parameters gained approximately 50 kg less over a 4-month period during winter housing than groups with the lowest values for those infection parameters.     

Effect of anthelmintic treatment of second-year cattle on growth performance during winter housing and first lactation yield

The effect of nematode infections on growth performance during winter housing and on first lactation yield was investigated in heifers on 69 farms. Half of each herd was treated with albendazole after housing, which resulted in significantly reduced egg output, antibody titres against Ostertagia and Cooperia, and pepsinogen values compared with the untreated control groups. Albendazole-treated groups gained on average 0.007 cm day-1 heart girth (i.e. 0.05 kg day-1) more than control groups during the housing period (P less than or equal to 0.10), varying from -0.060 to +0.137 cm day-1 among herds. Albendazole-treated heifers produced 195.4 kg milk per 305-day lactation more than untreated heifers (P less than 0.01). Per herd, the mean milk yield response to treatment was +313.8 kg milk (P less than 0.01), varying from -876 to +1950 kg. Milk production of untreated heifers increased by 10.5 kg milk kg-1 extra body weight, adjusted for age, measured after the second grazing season (P less than 0.05). This suggests that nematode infections occurring in the first 2 years of life negatively influence milk production by reducing weight gains and hence body weight at calving.     

Effect of naturally occurring nematode infections on growth performance of first-season grazing calves

Liveweight of calves on 89 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection during the grazing season. There were significant between-herd variations in antibody titres against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus as well as in pepsinogen values. All but six herds (93.1%) had gastrointestinal nematode infections, as measured by faecal egg counts in September. Faecal samples of 17 herds (19.3%) contained lungworm larvae in September. Liveweight of calves per herd deviated from -68.1 kg to +84.1 kg from the age-adjusted population mean after their first grazing season. Growth performance up to the time of liveweight measurements was significantly correlated negatively with several serological and parasitological parameters. Data could be fitted by means of both linear and segmented curvilinear regression. Antibody titre against Cooperia spp. and gastrointestinal nematode egg output measured in September accounted for 3.1% (P less than 0.10) and 6.7% (P less than 0.05), respectively, of the variation in growth performance among herds. Certain infection parameters, when combined, accounted for 9.2% of this variation; these were antibody titre against Cooperia spp. and larval counts for both gastrointestinal nematodes and lungworm. Adding certain management factors to these infection parameters resulted in a model explaining 27.6% of the observed variation in growth performance among herds. These factors were supplementary feeding, lungworm vaccination, anthelmintic treatment at housing, date of housing and herd age.     

Effect of nematode infections and management practices on growth performance of calves on commercial dairy farms

Liveweight of calves on 86 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection estimated in October and December. There were significant between-herd variations in all the serological infection parameters measured. On average 20.5 larvae per gram faeces (geometric mean) were found in October. Faecal samples of 20.5% of the herds contained lungworm larvae. Liveweight of calves deviated per herd from -59.8 kg to +52.2 kg from an age-adjusted population mean after their first grazing season. Growth performance was significantly related negatively to several serological and parasitological parameters. Data were fitted by means of both linear and segmented curvilinear regression. By combining infection parameters 19% of the variation in growth performance among herds could be explained. Infection parameters involved were antibody titre against Cooperia spp., egg output and lungworm larval count. It was found that antibody titres were significantly correlated positively to herd age, while pepsinogen values and egg output were negatively correlated to age. Combining supplementary feeding and anthelmintic treatment during the grazing season with the infection parameters into one model explained approximately 30% of the observed variation in growth performance among herds. It was shown that these findings were consistent with those of a similar study conducted on the same farms a year earlier, although there were clear differences between the years. Finally, significant positive relations were found between the levels of exposure to nematode parasites within farms between two consecutive years.     

Effect of naturally occurring nematode infections in the first and second grazing season on the growth performance of second-year cattle

Antibody titres against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus as well as pepsinogen values, reflecting exposure to nematode infection, differed significantly among herds of second-year cattle on 87 farms. Faecal examinations revealed that gastrointestinal nematode infections were present in all herds. Similar results were found in yearling-herds on the same farms a year earlier. Liveweight of yearlings per herd deviated from -64.7 kg to +94.4 kg from an age-adjusted population mean after the second grazing season. This mean herd weight deviation was significantly related negatively to antibody titre against Ostertagia spp. (linear regression, P less than 0.05; segmented curvilinear regression, P less than 0.01) and to antibody titre against Cooperia spp. (segmented curvilinear regression, P less than 0.05), both measured in the second grazing season. Antibody titre against Ostertagia spp. measured in the first grazing season, when yearlings were calves, was significantly correlated positively to age-adjusted body weights at the end of the second grazing season. The results suggested that immunity built up during the first year had a positive effect on growth performance in the second year, but that on average the acquired immunity was insufficient to prevent reduced weight gains in the second grazing season.     

Serum pepsinogen levels to monitor gastrointestinal nematode infections in cattle revisited

The serum pepsinogen level is widely accepted as a useful parameter for monitoring gastrointestinal nematode infections in first-season grazing calves. However, several aspects, with possible implications for its practicality and the way to use the pepsinogen test, have received little attention to date. The objectives of this study were to evaluate (1) the reproducibility of a pepsinogen assay; (2) the required sample size for a reliable diagnosis and (3) the compliance to and effect of advice based on pepsinogen levels determined in year one on the nematode infection levels in the next generation of calves. Despite a high repeatability of the pepsinogen assay within the reference lab, the reproducibility between different labs was poor. There was more variation in pepsinogen levels between herds than between animals within a herd, suggesting that it is most useful to make a herd level diagnosis. Sample size calculation indicated that sampling seven animals sufficed to obtain a reliable indication of calf groups of up to 40 animals. Eighty-two herds were followed-up over two consecutive years and 39 (48%) had followed the advice that was formulated based on pepsinogen levels. Thirty-nine percent of the herds were advised to reduce the intensity of chemoprophylaxis. Samples from animals of those herds showed a higher pepsinogen level in the second year, but none of them had a mean pepsinogen level that is considered excessive. It is concluded that pepsinogen determination at housing from a limited number of animals can contribute to the design of the anthelmintic control strategy in the next year and a more targeted use of anthelmintics. However, more efforts are needed to harmonize the assay between veterinary diagnostic labs.     

Effect of husbandry methods on seropositivity to African swine fever virus in Sardinian swine herds

Multiple logistic regression was used on serological data collected in the context of the Sardinian African swine fever (ASF) eradication program from pig farms in the province of Nuoro, Sardinia. The monthly percentage of ASFV-positive herds decreased significantly from October 1994 through March 1996 (P < 0.001). The farm-level risk of seropositivity to African swine fever virus (ASFV) was higher in free-range farms than in partial-confinement farms (odds ratios (OR) varied between 4.9 in October 1994, and 5.7 in March 1996, P < 0.001). The risk of infection for total-confinement farms was one-fifth of the risk for partial-confinement farms in October 1994 (OR = 0.2, P < 0.001), whereas in March 1996, the estimated OR was 0.57 and not significant (upper confidence limit = 1.1). The maintenance of ASFV in Sardinia was primarily associated with free-range pig farms. The natural logarithm of the number of pigs tested per visit in a farm was positively associated with the risk of herd seropositivity (OR = 2.6, P < 0.001).     

Factors associated with circulation of pseudorabies virus within swine herds

Data were collected from 104 Minnesota swine farms quarantined for pseudorabies virus (PRV) infection. Each herd was serologically evaluated for the presence of antibodies to PRV in finishing pigs. Herd management practices, swine housing design, and disease profiles were described for each farm. Multiple logistic regression analysis was used to determine which factors were associated with circulation of PRV in the finishing pigs of farrow-to-finish farms. Sixty-seven (64%) of the herds had no serologic evidence of PRV circulation in the finishing section, whereas 37 herds (36%) contained at least one PRV seropositive finishing pig. The odds of a given finishing herd being seropositive for PRV were 2.85 times higher if the finishing pigs were housed in confinement (P = 0.01), 2 times higher if Actinobacillus (Haemophilus) pleuropneumoniae was a clinical problem in the herd (P = 0.03), 1.36 times less for each year that passed since the herd quarantine was issued (P = 0.01), 1.74 times higher if clinical signs of PRV were reported (P = 0.04), and 1.52 times higher if animal protein was included in at least one of the rations (P = 0.08).     

Effect of anthelmintic treatment of dairy cattle on milk production related to some parameters estimating nematode infection

On 31 farms, blood samples were taken from adult dairy cattle in September 1985, when pastured, and in November-December 1985, when stabled, to assess serum pepsinogen levels and level of nematode antibody titres. Faecal samples taken in September were examined to establish the presence of parasites by means of egg counts and larval identification. During the stabling period, dry cows were either treated with ivermectin or with a placebo in alternate sequence of expected calving date. As a result, 285 cows were treated with ivermectin while 242 cows served as controls. Anthelmintic treatment resulted in a significant increase in the 305-day milk production of 205.1 kg (P less than 0.01). Fat and protein percentages were not significantly influenced by anthelmintic treatment. There was a significant between-herd variation in nematode antibody titres and in pepsinogen values. The mean herd milk-production response to treatment correlated positively with the mean herd Ostertagia antibody titre measured in September 1985 (r = 0.364, P less than 0.05).     

Economics of a dry-cow anthelmintic drenching programme for dairy cows in New Zealand. Part 2. Influence of management factors and other herd characteristics on the level of response

The results of a series of trials conducted on 47 seasonal supply dairy farms in the southern North Island of New Zealand, which indicated a statistically significant overall production response of 2.24 kg milkfat/cow/lactation following a 2-treatment dry-cow anthelmintic drenching programme (Bisset et al., 1987), were subjected to further analyses in an attempt to identify any management factors or herd characteristics which may have influenced the levels of production response to treatment in individual herds. The management factors examined included calf drenching practices, types of grazing system, mean pre-calving condition of the herds, and 'nutritional status' of the herds over the milking season. The influence of herd quality, herd size and geographical location were also examined. Considered separately, only calf drenching practice had a significant influence on the level of herd response to treatment. Increases in milkfat production/cow due to the treatment programme were significantly greater (P less than 0.05, t-test) on farms where calves had received a minimal number of drench treatments (less than or equal to 2) between weaning and the end of March (mid-autumn) (+5.32 kg/cow/lactation, P less than 0.01) (= 108.2 l milk), than on farms where calves had received regular 3-4 weekly treatments over the same period (+0.42 kg/cow/lactation, N.S.) While none of the other factors, considered in isolation, appeared to significantly influence the production response of herds, observations on possible interactive effects suggested that the grazing system employed was probably of importance in so far as it determined the level of exposure of cows to calf-contaminated pasture. Thus, the greatest mean response to the treatment programme occurred in herds where cows were overwintered on areas grazed during the milking season by calves which had received less than or equal to 2 drench treatments from weaning until the end of March (+5.95 kg milkfat/cow/lactation, P less than 0.01).     

Milk yield increase after anthelmintic treatment of dairy cattle related to some parameters estimating helminth infection

On 81 farms blood samples were taken from adult dairy cattle, on pasture in October 1986 and after stabling in December 1986, to measure antibody titres against the nematodes Dictyocaulus viviparus, Cooperia spp. and Ostertagia spp., and the trematode Fasciola hepatica, and serum pepsinogen values. Faecal samples, collected in October, were examined to confirm the presence of parasites by means of egg counts and larval identifications. From December until the end of the stabling period, dry cows were either treated with albendazole or left untreated in alternate sequence of calving date. Treated cows produced 132.9 kg milk per cow per lactation more than untreated cows (P less than 0.01). Fat and protein percentage were not significantly influenced by anthelmintic treatment. The mean herd milk yield response to treatment varied from -889 to +1231 kg milk per cow per lactation. There was a significant between-herd variation in antibody titres against nematodes and in pepsinogen values. However no significant correlations between these parameters and the mean herd milk yield response to treatment were found.     

A field evaluation of Nobi-Vac atrophic rhinitis vaccine

A field trial was carried out with Nobi-Vac AR vaccine in 11 swine breeding herds. One herd suffered from severe B. bronchiseptica (BB+) rhinitis in piglets, while no clinical Atrophic Rhinitis (AR) was observed. Ten herds were described as AR problem herds, because clinical AR was observed for at least 1 year in spite of the fact that medication of sows and piglets was carried out and adequate housing and management systems were available in most herds. BB+ was isolated in 9 of these 10 farms and the AR pathogenic P. multocida (PM+) in all these farms. The trial started when piglets were born of sows which had been vaccinated 3 times. All piglets between 7 and 10 weeks old were examined clinically for AR. Nasal swabs from 20 pigs on each farm were screened bacteriologically for BB+ and PM+ every other month. A severe reoccurrence of AR was found in 2 of the 10 AR problem farms. In these 2 herds the 'all in-all out' system was not applied in farrowing and weaning houses. In the 8 other AR problem herds the percentage of pigs with AR decreased significantly below the average level of 1% per year. The percentage of pigs infected with BB+ and PM+ also decreased significantly. PM+ was significantly related to the percentage of clinical AR piglets. Seasonal effects contributed to a minor extent to the percentage of AR piglets. After 2.5 years of this trial PM+ could not be isolated during the last 12 months in six of the remaining AR problems herds. The conclusion is that Nobi-Vac AR vaccination of the sow gave protection against clinical AR in piglets on those farms (80%) which provided adequate housing and management systems.     

Field evaluation of test-and-removal and vaccination as control measures for pseudorabies in Missouri swine.

Eighteen Missouri swine herds were serologically monitored to determine the efficiency of two methods for the control of pseudorabies. A serum neutralization test-and-removal procedure was effective in ten of ten herds using this method. Vaccination procedures were less reliable. Virus still circulated in five of eight vaccinated herds and a thorough epidemiological evaluation of herd status was impossible. Titers caused by vaccination could not be distinguished from those by natural infection. Vaccination also was carried out in three seronegative herds. Antipseudorabies virus titers in these herds ranged from negative to 1:16 two to three months postvaccination. A majority of the sows in these herds responded with low 1:2 or 1:4 titers following vaccination. A direct comparison of "test and removal" farms and farms that used vaccination was not possible because of the differences between the two groups of farms.     

Point source exposure of cattle to Neospora caninum consistent with periods of common housing and feeding and related to the introduction of a dog

Eight dairy herds with evidence of post-natal transmission of Neospora caninum were used to test the hypothesis of a point source exposure by a retrospective analysis of the housing and feeding of infected age-groups. The first N. caninum-associated abortion or birth of N. caninum-seropositive offspring from the post-natally infected age-group was considered as the first indication of the infection. In seven of the eight dairy herds, a point source exposure to N. caninum of the infected age-groups was found during a limited period of common housing and feeding. In all herds studied, the analysis indicated that the cattle had been infected shortly before the first abortions occurred. In all, except one herd, the post-natal infection was more directly related to housing than to feeding. Therefore, it appeared that the feed was contaminated in the feeding alley. In one herd, the total mixed ration was found to be the probable path of infection. In all farms studied, a new dog (young, adult dog or litter) had been introduced within a period of 1.5 years prior to the first indication of N. caninum infection in the cattle. As there was evidence in all herds of vertical transmission of neosporosis for years, it is hypothesized that the newly introduced dog was infected with N. caninum by materials from already infected cattle and subsequently transmitted the infection to other cattle by shedding of oocysts.     

A field evaluation of Nobi®‐Vac Atrophic Rhinitis vaccine

Summary

A field trial was carried out with Nobi‐Vac AR vaccine in 11 swine breeding herds. One herd suffered from severe B. bronchiseptica (BB+) rhinitis in piglets, while no clinical Atrophic Rhinitis (AR) was observed. Ten herds were described as AR problem herds, because clinical AR was observed for at least 1 year in spite of the fact that medication of sows and piglets was carried out and adequate housing and management systems were available in most herds. BB+ was isolated in 9 of these 10 farms and the AR pathogenic P. multocida (PM+) in all these farms.

The trial started when piglets were born of sows which had been vaccinated 3 times. All piglets between 7 and 10 weeks old were examined clinically for AR. Nasal swabs from 20 pigs on each farm were screened bacteriologically for BB+ and PM+ every other month.

A severe reoccurrence of AR was found in 2 of the 10 AR problem farms. In these 2 herds the ‘all in‐all out’ system was not applied in farrowing and weaning houses. In the 8 other AR problem herds the percentage of pigs with AR decreased significantly below the average level of 1% per year. The percentage of pigs infected with BB+ and PM+ also decreased significantly. PM+ was significantly related to the percentage of clinical AR piglets. Seasonal effects contributed to a minor extent to the percentage of AR piglets.

After 2.5 years of this trial PM+ could not be isolated during the last 12 months in six of the remaining AR problems herds.

The conclusion is that Nobi‐Vac AR vaccination of the sow gave protection against clinical AR in piglets on those farms (80%) which provided adequate housing and management systems.     

Toxigenic type D Pasteurella multocida in New South Wales pig herds—prevalence and factors associated with infection

Between March and July 1987, a study was undertaken to determine the prevalence of and factors associated with toxigenic type D Pasteurella multocida infection in New South Wales pig herds. Toxigenic type D P. multocida was isolated from the nasal cavities of pigs in one (2%) of 50 randomly selected herds. Toxigenic isolates were also recovered from 2 (8%) of a separate group of 25 herds that had purchased pigs from a known infected piggery in South Australia (herd SA). Snout abnormalities were present in 9.4%, 3.2% and 1.8% of grower pigs in the 3 affected herds. Isolation of toxigenic P. multocida was significantly associated (p less than 0.0001) with the occurrence of clinically affected pigs in the herd. Purchase of at least 5 pigs from herd SA was associated with an elevated risk (p less than 0.05) of isolation of toxigenic P. multocida.     

Herd-level risk factors for Cryptosporidium infection in dairy-goat kids in western France

We conducted a cross-sectional study of risk factors for herd-level kid positivity for Cryptosporidium parvum oocysts in dairy-goat farms (Deux-Sèvres, western France). From January to March 2003, faeces from a convenient sample of 879 5- to 30-day-old goat kids from 60 herds were examined microscopically after staining with carbol fuschin. Oocyst shedding was scored semi-quantitatively (0 to 4+) allowing us to obtain a cumulative score per herd. Standardized questionnaires with information about management practices were collected in each farm. We found positive kids in 32 of 60 herds (53.3%) and in 142 animals out of 879 (16.2%). We used logistic regression for two risk-factor model: (1) simple positive (case: herd score > or = 1+, at least one positive kid in the herd, versus control: herd score=0), (2) strongly positive (case: overall herd score > or = 3+ versus control: herd score <3+). Risk factors associated with simple positive herds were period of sampling compared to the peak of births (After versus Before, OR=4.2, 95% CI 1.2, 15.3) and practice of kid grouping by age or weight (Yes versus No, OR=4.4, 95% CI 1.0, 19.1). Risk factors associated with strongly positive herds were period of investigation (February/March versus January, OR=12.7, 95% CI 2.1, 76.6), exposure to graminaceous plants in forage (OR=11.6, 95% CI 1.7, 81.0) and type of ventilation in the goat premises (Vertical versus Wind effect, OR=14.7, 95% CI 2.1, 106.1). No important association was found between kid-management practices and herd positivity. These results suggest a major role of the environment of kids during their first hours of life in the adult-goat premises regarding the transmission of C. parvum infection.     

THE ECONOMIC EFFICIENCY OF A VETERINARY PREVENTIVE MEDICINE AND MANAGEMENT PROGRAM IN VICTORIAN DAIRY HERDS

SUMMERY: This paper reports the major results of a 4-year controlled study of the impact of a dairy herd health and management program on dairy farms. The aim of the project was to conduct a practical preventive medicine program which could be operated by practising field veterinarians to assess the economic value of the program. The analysis of performance involved 59 program farms which received the program and 47 surveillance farms which did not receive the program. Each group commenced with 80 farms. A comparison of indices reflecting the efficiency of production showed relative gains for program herds when compared to surveillance herds and these differences were significant for the indices of butterfat per hectare (P=.001) and butter fat per man (P=.005) but not for butterfat per cow (P=.455). The indices of financial efficiency showed significant improvements in program farms when compared with surveillance farms in the standardised change in gross margin per hectare (P=.001), per man (P=.003) and per cow (P=.007). On a mean whole-farm basis, the program gave an improvement in gross margin of 23.58, 65.56 and 90.30 per hectare in the second to fourth years respectively of the project when compared with performance in the first year. Mean intercalving intervals were significantly shorter in program than surveillance herds throughout the project (P=.013). The proportion of cows calving within 8 weeks of the start of the calving season increased from 68.5% to 74% in program herds and from 72% to 73% in surveillance herds, but there was no significant difference (P=.101) between groups in this change. The standardised change in bulk milk cell count was greater in program herds than surveillance herds, but the quarter infection prevalence of surveillance herds. which was only measured in the final year of the project, was significantly lower than the prevalence measured at the same time in program herds. It was concluded from this study that the dairy health and management program tested in this study represents a highly profitable investment for dairy farmers.     

Prevalence and risk factors for intestinal parasite infection in goats raised in Nakhon Pathom Province,Thailand

The objectives of this study were to determine the prevalence and risk factors for intestinal parasite infection in goats raised in Nakhon Pathom Province. Fecal samples from 190 goats in 12 herds were collected per rectum. Questionnaires focusing on the general information about the farm and farmers, and management practices on farms were completed. Modified McMaster counting technique was performed to detect eggs of intestinal parasites. Each egg found was classified into three groups of parasites based on its characteristics. Individual and herd prevalence were calculated. Multiple logistic regressions were performed to analyze risk factors of infection. Herd prevalence of intestinal parasite infection was 100%, while individual prevalence was 79.47%. Strongyle group was the most common intestinal parasite found in this study. Moniezia spp. (8/190) and Trichuris spp. (1/190) were also found. The average number of eggs found was 1,176 eggs per gram of feces. Risk factors for intestinal parasite infection were housing system, deworming interval, and type of goat in herd. Goats housed in groups had higher infection rates compared with goats housed individually (odds ratio (OR) = 6.34; P value = 0.009). Goats in herds in which anthelmintic drugs were administered in intervals of greater than 3 months were more likely to become infected with intestinal parasites (OR = 33.07; P value <0.001). Goats in herds that kept only dairy goats were less likely to become infected than herd that kept only meat goats or kept both dairy and meat goats (OR = 46.20 and 8.75; P value <0.001 and 0.011, respectively).     

The effect of ivermectin treatment of late pregnant dairy cows in south-west Victoria on subsequent milk production and reproductive performance

SUMMARY A total of 498 dairy cows in 5 predominantly pasture-fed herds were allocated to pairs. One cow in each pair was treated with a single dose of ivermectin during the dry period. Treated and untreated cows were managed as a single group throughout the trial. Most cows calved between 45 and 115 days after treatment. When data from all herds were pooled, treated cows produced an extra 74 L of milk over the first 100 days of the subsequent lactation (95% confidence interval 20 to 128). Means were greater among treated groups relative to untreated groups in all 5 herds. However, when analysed individually, differences were statistically significant (P < 0.05) in 1 herd only. Over the complete lactation, mean milk volume for treated cows was 86 L greater than for untreated cows (95% confidence interval of difference -57 to 229; P = 0.24). Untreated cows produced 2473 L and 5883 L for the first 100 days of lactation and for the complete lactation, respectively. Milk production responses to treatment did not vary significantly with parity, body condition score, previous production index, calving date category or with plasma pepsinogen concentration or faecal egg count at the time of treatment. Faecal egg counts and plasma pepsinogen concentrations were low at the start of the study. The interval from calving to conception was 4.8 days less in treated cows (95% confidence interval 1.2 to 8.2) relative to untreated cows when data from all 5 herds were pooled. Differences within individual herds were not statistically significant.