Increase in milk yield following eprinomectin treatment at calving in pastured dairy cattle

Gastrointestinal nematodes rarely cause signs of clinical disease in adult cattle. However, they have been shown to exert a negative impact on production in lactating animals, as seen by improved production following elimination of the worms using anthelmintics. A double blind, randomized clinical trial was performed in 28 dairy herds in Canada. The objective of the study was to evaluate the effect of treatment with eprinomectin pour-on solution (IVOMEC EPRINEX) at calving on production, in cattle that have had some exposure to pasture. Cows were randomly allocated to treatment or placebo in blocks of 10, based on calving date, and treated with eprinomectin or placebo on the day of calving.Information on milk production was obtained from all animals, as well as recorded cases of selected diseases. Milk production results from the Canadian dairy herd management system database were analysed using a mixed model with herd as a random effect and test within-cow as a repeated measurement. Test day milk yields from the first six tests after treatment were included in the model, representing a period of between 180 and 200 days in milk (dim). Treated cows produced an additional 0.94 kg of milk per day when compared to the controls over this period. The production effect was independent of calving season, age of the animal and geographical location. No effect of treatment was seen on milk composition, somatic cell count (scc) or on the selected health parameters that were recorded for all included animals.Monthly fecal egg counts (FEC) were performed for eight randomly selected animals in each herd. The observed FEC were low in this study, with a range from 0 to 419 trichostrongyle type eggs per 5g (ep5g) of feces in animals not yet treated with the anthelmintic. The average count was 9.8 and the median was 1.0. FECs dropped immediately after calving and stayed lower for at least 100 days in treated animals when compared to controls.In conclusion, gastrointestinal nematodes appear to have an effect on milk production in Canadian dairy cows that have had some degree of pasture exposure. Eliminating the present subclinical parasite burdens produced a consistent increase in milk production that can yield economic benefits for the dairy producer.     

Anthelmintic treatment of pastured dairy cattle in California

The relationship of anthelmintic treatment for subclinical gastrointestinal nematode parasitism with resultant milk production was studied on 3 California dairies where animals were maintained on a pasture-based nutritional program. All of the animals that started lactating (freshened) during a 12-month period participated in trials in which coumaphos was given as a feed top dressing to animals averaging 30 days into lactation. All of the animals that freshened during the subsequent 12-month period from 2 of the same 3 dairies participated in trials in which thiabendazole was administered at or within 2 weeks before freshening. Anthelmintic administration during 2 consecutive lactation cycles under the conditions of the present study resulted in no consistent reproducible significant changes in milk production.     

A meta-analysis of the milk-production response after anthelmintic treatment in naturally infected adult dairy cows

Meta-analysis was used to estimate the effects of anthelmintic treatment on milk production in dairy cows. The literature search included peer-reviewed journals (both full articles and abstracts), conference proceedings and theses and included documents written in English, Spanish, French, Portuguese or Italian. The study outcome was defined as the difference in milk production (kg/cow per day) between treated and untreated cows. Random effect meta-analyses were performed on 75 trials published between 1972 and 2002. The combined estimate after controlling for publication bias and/or small-study effect was of 0.35 kg/cow per day. Significant variation among studies was detected and although several variables were associated with the study outcome, they did not significantly reduce the unexplained variability among trials. Trials reporting the use of endectocides had higher milk-production response compared with trials using older anthelmintics. Similarly, whole-herd treatment trials or trials which applied the treatment in mid-lactation or strategically throughout the year had higher response compared with calving or dry-period treatment trials. Trials reporting the results as total 305-day milk production had lower response compared with trials which measured production as daily milk weight. Primiparous cows trials had lower responses compared with multiparous cows trials.     

Nematode burdens of pastured cattle treated once at turnout with eprinomectin extended-release injection

The efficacy of eprinomectin in an extended-release injection (ERI) formulation was evaluated against infections with third-stage larvae or eggs of gastrointestinal and pulmonary nematodes in cattle under 120-day natural challenge conditions in a series of five studies conducted in the USA (three studies) and in Europe (two studies). For each study, 30 nematode-free (four studies) or 30 cattle harboring naturally acquired nematode infections (one study) were included. The cattle were of various breeds or crosses, weighed 107.5–273 kg prior to treatment and aged approximately 4–11 months. For each study, animals were blocked based on pre-treatment bodyweight and then randomly allocated to treatment: ERI vehicle (control) at 1 mL/50 kg bodyweight or Eprinomectin 5% (w/v) ERI at 1 mL/50 kg bodyweight (1.0 mg eprinomectin/kg) for a total of 15 and 15 animals in each group. Treatments were administered once on Day 0 by subcutaneous injection in front of the shoulder. In each study, all animals grazed one naturally contaminated pasture for 120 days. At regular intervals during the studies, fecal samples from all cattle were examined for nematode egg and larval counts. In four studies pairs of tracer cattle were used to monitor pasture infectivity at 28-day intervals before and/or during the grazing period. All calves were weighed before turnout onto pasture and at regular intervals until housing on Day 120. For parasite recovery, all study animals were humanely euthanized 27–30 days after removal from pasture.     

Effect of a peri-parturient eprinomectin treatment of dairy cows on milk production

AIM: To quantify and economically evaluate the effect on milk production of peri-parturient treatment of dairy cows with eprinomectin. METHODS: On 3 farms in separate geographic areas of New Zealand, 849 first-calf heifers and multiparous cows were ranked and paired within parity, date of calving and expected milk production. Within pairs, cows were randomly allocated to treatment with either a commercial formulation of eprinomectin, applied at a dose rate of 500 mug/kg liveweight, or an equivalent volume of vehicle containing no antiparasitic agent and administered at the same dose volume, generally within the first week post-calving. On each farm, trial cows shared the same pasture. Over a single lactation, records were maintained of milk quantity and content. RESULTS: Trichostrongylid eggs were identified in pre-treatment faecal samples from all farms, verifying the presence of gastrointestinal parasites. Overall 25.5% of the cows sampled were positive for nematode eggs, but only 8% had counts 50 eggs per gram of faeces (epg). Daily milk volume, milk protein and milksolids (yield of milk fat + milk protein) were higher for eprinomectin-treated multiparous cows than for controls (milk volume: 20.36 l/day vs 19.76 l/day, p=0.005; milk protein: 0.700 kg/day vs 0.685 kg/day, p=0.012; milksolids: 1.613 kg/day vs 1.583 kg/day, p=0.031, respectively). The daily value of the increased production from eprinomectin-treated multiparous cows was estimated to be NZ0.034 dollar for milk fat (p=0.095) and NZ0.078 dollar for milk protein (p=0.012), equating to NZ0.104 dollars for milksolids (p=0.031), averaged over the whole lactation. No significant difference in milk production was detected between treated and control first-calf heifers. Averaged over the whole herd, the peri-parturient treatment of multiparous cows and first-calf heifers with eprinomectin increased daily milk volume and milk protein production of treated vs control cows (19.28 l/day vs 18.86 l/day, p=0.020, and 0.661 kg/day vs 0.650 kg/day, p=0.047, respectively). CONCLUSION: These data provide evidence that the use of a peri-parturient treatment of eprinomectin on multiparous cows can increase their production of fluid milk and milksolids.     

The use of an indirect Ostertagia ostertagi ELISA to predict milk production response after anthelmintic treatment in confined and semi-confined dairy herds

An indirect Ostertagia ostertagi ELISA was used in late lactation milk samples from cows in confined and semi-confined dairy herds to determine if it could predict milk production response after endectocide treatment at calving. Holstein cows from 9 dairy farms from Prince Edward Island (PEI), 5 from central Nova Scotia and 16 from southern Ontario that were participating in a clinical trial of endectocide treatment around calving were used in this study. The cows were randomly treated with either eprinomectin pour-on endectocide or a placebo solution. Milk samples were obtained from cows late in the lactation before treatment was applied. These samples were tested for antibodies to gastrointestinal nematodes (GIN) using the indirect ELISA with the results expressed as optical density ratios (ODR). Production records were obtained from a computerized database of dairy herd improvement data. Pre-calving ODR showed a seasonal pattern. They were higher in the summer and fall and lower during the winter months. Older animals had higher pre-calving ODR values compared with younger cows. Similarly, cows from semi-confined herds had higher parasite antibody levels compared with cows from confined herds. The endectocide treatment did not affect the milk production response in the overall study population. However, the interaction effect between treatment and pre-calving ODR on milk production response after endectocide treatment was significant (P = 0.02), with some evidence of positive treatment response in cows with an ODR > 0.4. The relationship between pre-calving ODR and production response appeared to be quadratic rather than linear.     

Effect of eprinomectin pour-on treatment around calving on reproduction parameters in adult dairy cows with limited outdoor exposure

The objective of this study was to investigate if treatment of cows with eprinomectin around calving had any beneficial effects on the calving to first artificial insemination interval, calving to conception interval, and number of services per conception in totally- and semi-confined dairy herds. In totally-confined herds lactating- and dry-cows were housed throughout the summer and had no access to pasture. In semi-confined herds lactating- and dry-cows had limited outdoor exposure to a small pasture or paddock but were still fed a ration that met all their nutritional requirements. The study was carried out between February 2002 and February 2003 in 35 herds (2381 cows) located in Quebec, Ontario and Minnesota (USA) participating in a larger clinical trial. The herds kept electronic reproduction records. Cows were randomly allocated to receive eprinomectin or a placebo, with treatment being administered on or close to the day of calving. Monthly bulk tank milk samples from each farm were tested with an indirect ELISA using a crude Ostertagia ostertagi antigen and these data were averaged over the study year. The optical density ratio (ODR) values were then dichotomized into high and low using a cut-point of 0.50. Treatment effects were analyzed using Cox proportional hazards survival models with herd frailty effects for calving to conception and calving to first service intervals. Aalen's linear hazards model was used to investigate time-varying effects in the Cox models. A random effects poisson regression model was used to model the number of services per conception. Other predictor variables tested in the models were lactation number, calving season, study site, peak milk production, ODR and the lactating- and dry-cow housing variables. Overall, there was no significant effect of treatment on the three indices of reproductive performance. The effect of season of calving depended on how much time had passed since calving. Presumably this effect reflected a seasonal effect at the time of breeding. Hazard of conception in younger cows was higher than in older cows. Early bred cows tended to have a higher number of inseminations per conception than those bred late. The results of the study suggested that eprinomectin treatment at calving was not beneficial to reproduction.     

Ingestive behavior of pastured crossbred dairy cows offered different supplement types

The aim of this study was to assess the effect of different supplements on the behavior variables of crossbred dairy cows that were in pasture that comprised two 4?×?4 Latin squares (four periods, four treatments, and four animals). Each experimental period lasted 15 days (10 days to adapt animals to treatments and 5 days for data collection). The animals were supplemented twice a day, with different forage (corn silage and cactus pear) and concentrate sources (soy mea + wheat meal + corn meal + cotton seed together and soy meal as a single constituent of the concentrate). A significant difference (p?<?0.10) was observed for the percentage of time spent consuming the supplement and for idleness, rumination, and bite rate at the time of supplementation. The supplement intake period was greater for the cactus pear-based supplements due to the lower dry matter content. Those based on corn silage resulted in longer rumination periods than those consisting of cactus pear; however, the opposite was observed for supplements based on the cactus, which showed higher percentages of time for idleness. The supplementation influenced the ingestive behavior of crossbred dairy cows.     

The effect of eprinomectin treatment at calving on reproduction parameters in adult dairy cows in Canada

A clinical trial was carried out in two provinces of Canada to investigate the effect of treatment with eprinomectin at calving on production parameters in adult dairy cattle in 1999-2000. One of the objectives of this study was to evaluate the impact of treatment on reproductive performance as measured by: calving-to-conception interval, calving-to-first service interval and number of services per conception. The ability of an indirect ELISA using a crude adult Ostertagia ostertagi antigen to predict response to treatment also was evaluated. All lactating cows in 20 dairy herds were allocated randomly to receive either eprinomectin pour-on or placebo at calving. Information on reproductive parameters was obtained from computerised cow records. Survival models were used to evaluate the effect of treatment on the two intervals and a Poisson model was used to evaluate the number of services to conception. A total of 549 cows were included in these analyses. A marginally significant treatment effect on calving-to-conception interval was observed (hazard ratio=1.24, P=0.06) but not on calving-to-first service interval. A significant reduction in the number of breedings to conception for treated animals also was observed with a longer effect in cows with short interval to first service. Milk samples from a subset of 109 late-lactation cows were tested for antibodies against O. ostertagi. The ELISA optical-density ratio (ODR) values obtained between 120 days before calving and drying off were categorised as high ODR (>or=0.5) and low ODR (<0.5). Among untreated animals, the hazard of conception was lower (hazard ratio=0.38, 95% CI=[0.19,0.75]) for high-ODR cows compared to low ODR cows suggesting that higher parasite burdens had an adverse effect on reproductive performance. Treated high-ODR cows had a hazard of conception equivalent to the hazard for all cows in the low-ODR group (indicating that treatment prevented the negative effect associated with these higher parasite burdens).     

Effect of a treatment with eprinomectin or trichlorfon on the yield and quality of milk produced by multiparous dairy cows

The effects of a strategic antiparasitic treatment against Hypoderma species and other parasites on the milk yield, composition, and somatic cell counts of 742 multiparous dairy cattle were investigated on 79 farms in a Hypoderma species-endemic area in western Switzerland; 357 of the cows were treated with eprinomectin, 252 with trichlorfon, and 133 were left untreated. The treatments were given between October and early December 1998, on average 53 days before calving. Milk yield, fat, protein and somatic cell counts were measured once a month until the end of lactation. Eprinomectin and trichlorfon significantly increased milk yield during the first month after treatment compared with the control cows by 2.14 (P < 0.001) and 2.50 kg per day (P < 0.001), respectively. Initially, the difference between the eprinomectin- and trichlorfon-treated animals was not significant, but the effect of eprinomectin on milk yield was persistent, whereas the effect of trichlorfon decreased significantly by 0.12 kg per day per month (P < 0.05). The somatic cell counts increased significantly slower in the treated cows than in the control cows (P < 0.05). Milk composition was not affected by the treatments.     

The effect of repeated, four-weekly eprinomectin treatment on milk production in pasture-based, seasonally-calving dairy cattle

A randomised clinical trial from the North Island of New Zealand was conducted to assess the effect of repeated anthelmintic treatment on milk production, and to assess factors that affect treatment response. Nine hundred and twenty three multiparous, lactating dairy cattle from three pasture-based, spring-calving dairy herds were enrolled in this trial. Within each herd, cattle were stratified on age and calving date, and were randomly allocated to treatment (n=319) or control (n=604) groups. The treatment group received ≥0.05mg/kg of topical eprinomectin every 28 days for eight treatments during lactation. Pooled-milk from treated cows and bulk-milk samples were obtained at each treatment and analysed with an Ostertagia antibody ELISA, expressed as optical density ratios (ODR). Bi-monthly milk data were collected and expressed as energy-corrected milk (kg/day; ECM). A linear mixed model was used to analyse ECM, with cow as the random effect. The effect of anthelmintic treatment on days from calving, and start-of-mating, to conception were analysed with Cox-proportional hazard models. ODR values ranged from 0.6 to 1.3; there were no differences in ODR between herds (p=0.12), or between pooled-milk from treated cows and bulk-milk (p=0.26). Repeated treatments had no effect on daily ECM yields (p=0.74). However, there was a significant treatment×herd interaction (p=0.03); treatment increased ECM in one herd by 0.781kg/cow/day (p=0.015), but resulted in a non-significant decrease in the other two herds. A curvilinear interaction existed between days-in-milk and treatment response (p=0.039); the greatest treatment effect occurred during mid-lactation. Previous year milk production (p=0.46) and age (p=0.11) did not influence the effect of treatment on ECM. Treatment had no effect on any reproductive parameter. In conclusion, under New Zealand pastoral conditions, anthelmintic treatment increased milk production in one herd, but had no effect in two other herds. Further work is needed to identify why this variation in gastro-intestinal parasitism occurs.     

Monensin controlled-release intraruminal capsule for control of bloat in pastured dairy cows

Monensin, a polyether ionophore antibiotic, is potentially an important agent for bloat relief in dairy cows grazing temperate legume-based pasture. A series of studies was undertaken to determine the effect of monensin, when delivered continuously in the rumen of lactating dairy cows by means of controlled-release capsules (monensin CRC). Such devices release approximately 300 mg/head/day for 100 d. A short-term pilot study made at Ruakura, New Zealand, tested monensin CRC in cows selected for high susceptibility to bloat and grazing lucerne (Medicago sativa) or red clover (Trifolium pratense). Treatment significantly reduced the incidence of bloat, while milk yield and protein yield were increased. There was no effect on fat yield. Following the pilot study, 6 large-scale field experiments involving a total of 368 lactating dairy cows, were made in Australia and New Zealand to confirm the effectiveness of monensin CRC for bloat control and to measure the effect of such treatment on milk production and composition. A severe bloat problem occurred in 2 experiments, mild bloat occurred in 2 others, while no visual signs of bloat were observed in the remaining 2 experiments. Bloat was significantly (P less than 0.05) reduced by monensin CRC treatment when data was pooled over the 4 experiments in which bloat occurred. Daily milk yield was increased in all experiments from a mean of 17.7 in untreated groups to 18.8 kg/head/day (P less than 0.05) in monensin CRC-treated cows. Protein percentage was not affected by treatment, while there was a decrease from 4.29 to 4.10% fat, although total fat yield was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Risk management of paratuberculosis in dairy herds

Risk management of paratuberculosis (Johne's disease) in a dairy herd requires an assessment of the likelihood of paratuberculosis occurring in the herd, the economic impact of paratuberculosis on the herd and an evaluation of measures that can be taken to reduce this likelihood and impact.The likelihood of paratuberculosis occurring in the herd is related to the regional herd-level prevalence of paratuberculosis and the herd management (e.g., introducing animals from other herds). The economic impact of paratuberculosis includes production losses due to subclinical and clinical cases, losses due to increased replacement of animals and costs of control measures. Furthermore, a reduction of the price of milk from infected herds might result from consumer concerns about the zoonotic potential of paratuberculosis.Measures that reduce the likelihood of paratuberculosis occurring in a herd and its impact include preventive management measures (e.g., closed herd management and an effective separation of susceptible young stock from adult cattle), test-and-cull schemes for known infected herds and quality assurance schemes for test-negative herds. Quality assurance schemes for test-negative herds, such as schemes for 'low-Map bulk milk' and 'Map-free' herds, aim at safeguarding or increasing the profitability of these herds.Keys to success of risk management of paratuberculosis include realistic expectations of the results of paratuberculosis control, quality assurance and control programmes that are appreciated by farmers and incentives for farmers to participate in such programmes.     

Visual monitoring of reproduction in dairy herds

Two complementary approaches to produce visual information from reproduction records are described and exemplified. The Event Display shows all reproductive events, over a year, for all cows in a herd, by symbols placed in an array with columns representing calendar weeks and rows representing individual cows. The Reproduction Monitor consists of graphs of insemination and pregnancy rates evaluated weekly with a Bayesian technique. These visual monitoring tools are well suited to explore temporal variation in reproductive performance, they provide a quick overview of herd performance, and they provide information about individual animals.     

Effect of eprinomectin treatment on milk yield and quality in dairy cows in South Tyrol, Italy

The effect of treatment with eprinomectin on milk yield, milk composition and somatic cell counts (SCCs) was studied in 105 dairy cows located on seven farms in South Tyrol, Italy. On each farm, half of the animals were treated with eprinomectin and the other half were used as an untreated control group. Three test day records per animal were obtained before treatment (days -117, -75 and -33) and another three test day records were obtained after treatment (days 22, 62 and 131). Test day records comprised milk yield, milk composition, SCC and days in milk. On the day of treatment, blood samples and faecal samples were taken for parasitological analysis. Cows with positive faecal egg counts yielded less milk. A significant effect of eprinomectin on milk yield was observed after treatment and was most pronounced on the second and the third test days after treatment (+1.90 kg [P=0.002] and +2.63 kg [P<0.001], respectively). Furthermore, a significant decrease in SCC was observed on the second test day after treatment.     

Field efficacy of minidosed eprinomectin against Hypoderma spp. in dairy cattle

A chemoprophylactic field trial was conducted to assess the efficacy of pour-on eprinomectin applied at the approximate dose of 50 mcg/kg to dairy cattle with naturally occurring hypodermosis. Two-hundred-eleven cattle, selected from two herds with a high prevalence of Hypoderma spp. infestation, were divided in three groups: Group A (N = 71) was treated with pour-on eprinomectin at the recommended dosage of 500 mcg/kg, Group B (N = 64) at the lower dose of 50 mcg/kg, a third group (Group C, N = 76) served as untreated control group. Treatments were performed in November-December 2002 and the animals were examined for the presence of warbles in the following April and June. No larvae emerged in the treated groups, whereas a variable number of warbles (ranging from 1 to 28) were found in control animals. Adverse reactions were not observed in any animal, and only minor side effects were observed. A larger field trial carried out in the following year (1064 treated and 131 untreated control cattle) confirmed the chemoprophylactic efficacy of minidosed eprinomectin against Hypoderma spp. Administration of eprinomectin minidoses in dairy cattle is interesting because of the low costs involved and no need for milk withdrawal.     

Epidemiological investigations of an outbreak of intestinal atresia in two Israeli dairy herds

An epidemiological investigation of an outbreak of intestinal atresia in Israeli Holstein-Friesian newborn calves showed a linkage with rectal palpation for early pregnancy diagnosis, performed less than 42 days after insemination. The odds of an exposed calf, i.e., one born to a dam that was diagnosed by early palpation as having intestinal atresia were 119.7 times higher than one born in normal control herds (95% CI; 7.4-1946.3). A total of 682 calves-at-risk was recorded from mid-1998 to mid-2000 and a total of 47 calves (6.9%) were born with intestinal atresia during this period. Two forms of intestinal atresia were recognized at post-mortem: atresia coli and atresia ilei.