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1.
In recent foot and mouth disease outbreaks, many healthy animals have been culled to prevent disease transmission. Emergency vaccination is discussed as an alternative to culling of unaffected animals. A spatial and temporal Monte–Carlo simulation model was used to compare preventive culling and emergency vaccination. Different outbreaks are described using additional influence factors such as airborne spread, farm density, type of index-case farm and delay until establishment of the control strategies. The fewest farms were infected establishing a combined strategy including a 1 km preventive culling and 1–10 km emergency vaccination zone around each outbreak farm. Taking the number of culled and vaccinated farms into account, vaccination around the first diagnosed farm combined with the baseline strategy (culling of outbreak farms, protection and surveillance zone, contact tracing) is to be preferred. In the present study, emergency vaccination was an effective control strategy especially in densely populated regions. 相似文献
2.
为揭示宁夏地区荷斯坦牛后备牛在周岁前的健康问题和淘汰情况,收集了2013—2020年宁夏地区12 个规模化牧场的后备牛出生记录、健康问题记录和淘汰记录,统计了后备牛周岁前发生的主要健康问题,重点分析了后备牛腹泻和肺炎的发生情况随后备牛月龄和自然月份的关系;此外,还分析了后备牛周岁前的淘汰情况,以及淘汰风险与后备牛月龄和自然月份的关系。宁夏地区的荷斯坦牛中,腹泻和肺炎是后备牛在周岁前最易发生的健康问题,占所有健康问题的75%。后备牛腹泻集中发生在2月龄以内的犊牛中,肺炎病例在周岁前的各生命阶段中均有分布,总体上随着后备牛月龄的增加而减少。不同自然月份中,后备牛腹泻和肺炎的发生情况存在较大差异,腹泻在1~2月发生较多,肺炎在1~6月发病较多,冬季是宁夏地区规模化牧场健康管理的重点季节。周岁前的后备牛淘汰时,其平均淘汰日龄为160.21±110.00 天;随着后备牛月龄的增加,后备牛淘汰风险逐渐降低;不同自然月份中,8~12月淘汰的后备牛较多。结果揭示了宁夏地区荷斯坦牛后备牛周岁前的健康事件和淘汰发生情况,为该地区规模化牧场的后备牛管理提供了有用信息。 相似文献
3.
Yoko HAYAMA Takehisa YAMAMOTO Sota KOBAYASHI Norihiko MUROGA Toshiyuki TSUTSUI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2016,78(1):13-22
The characteristics of a livestock area, including farm density and animal species,
influence the spread of foot-and-mouth disease (FMD). In this study, the impact of
livestock area on FMD epidemics was examined using an FMD transmission model. For this
simulation, three major livestock areas were selected: the 2010 FMD epidemic area in Japan
as the baseline area (BS), a cattle and pig mixed production area (CP) and a cattle
production area (C). Simulation results demonstrated that under the 24-hr culling policy,
only 12% of epidemics among 1,000 simulations were abated within 100 days in the CP area,
whereas 90% of the epidemics ceased in the BS area. In the C area, all epidemics were
successfully contained within 100 days. Evaluation of additional control measures in the
CP area showed that the 0.5-km pre-emptive culling, even when only targeting pig farms,
raised the potential for successful containment to 94%. A 10-km vaccination on day 7 or 14
after initial detection was also effective in halting the epidemics (80%), but accompanied
a large number of culled or vaccinated farms. The combined strategy of 10-km vaccination
and 0.5-km pre-emptive culling targeting pig farms succeeded in containing all epidemics
within 100 days. The present study suggests the importance of preparedness for the 24-hr
culling policy and additional control measures when an FMD outbreak occurs in a densely
populated area. Considering the characteristics of the livestock area is important in
planning FMD control strategies. 相似文献
4.
An outbreak of foot and mouth disease (FMD) could seriously impact Australia's livestock sector and economy. As an FMD-free country, an outbreak would trigger a major disease control and eradication program that would include the culling of infected and at risk animals (‘stamping out’), movement restrictions and zoo-sanitary measures. Additional control measures may also include pre-emptive culling or vaccination. However, it is unclear what disease strategy would be most effective under Australian conditions and different resource levels. Using a stochastic simulation model that describes FMD transmission between farms in a livestock dense region of Australia, our results suggest that using current estimates of human resource capacity for surveillance, infected premises operations and vaccination, outbreaks were effectively controlled under a stamping out strategy. However, under more constrained resource allocations, ring vaccination was more likely to achieve eradication faster than stamping out or pre-emptive culling strategies. 相似文献
5.
In this study, we determined culling and mortality in adult breeding rabbits on 130 commercial farms in Spain during 2000-2005. The median size of the farms was 595 does (minimum to maximum: 131-5500 does). The median culling age per doe was 14.9 months old and 6 kindlings. The median monthly removal risk (MMR) in does was 9.3%, with 3.4% dead and 5.7% culled (including euthanized does). The MMR was negatively correlated with the degree of intensification of the reproductive rhythm (r=-0.37), age at first mating (r=-0.31) and kindling interval (r=-0.36). The MMR in males was 5.8% (1.2% dead and 4.2% culled or euthanized). Our estimation of the causes of culling does was based on a population of 82,352 does, 50,834 of which were culled or euthanized. The highest causes, calculated using the median of the monthly cumulative incidence (MCI), were 1.3% low productivity (0.9% infertility and 0.4% other causes), 0.5% mastitis, 0.5% poor body condition and 0.3% sore hocks. The causes of culling males were estimated based a population of 6514 males, 5313 of which were culled. The highest causes were 2.0% MCI low productivity (0.9% infertility and 0.5% no libido); 0.3% abscesses, 0.3% sore hocks and 0.2% poor body condition. The mortality and culling risks after first kindling were 8.7% and 7%, respectively. The highest risks of mortality and culling in does occurred during the first three kindlings, but remained stable thereafter. The gestation stage affected mortality; the risk of mortality per day increased as pregnancy progressed. There was a bimodal distribution with a peak of dead females between days 10 and 15 of gestation (0.1-0.2% mortality risk per day (MD)) and another larger peak between days 25 and 33 (0.3% MD). In 1046 on-farm necropsies performed on females we found alterations of the respiratory and digestive tracts compatible with being causes of death in 29.4% and 27%, respectively. 相似文献
6.
Knauer M Karriker LA Baas TJ Johnson C Stalder KJ 《Journal of the American Veterinary Medical Association》2007,231(3):433-436
OBJECTIVE: To determine the accuracy of sow culling classifications reported by lay personnel on commercial swine farms. DESIGN: Retrospective cohort study. ANIMALS: A convenience sample of 923 sows from 8 conventional, farrow-to-wean farms that followed standard operating procedures. PROCEDURES: Sows were examined at slaughter, and lesions were recorded. Individual production records were reviewed to determine the farm-reported reason for culling the sows, and criteria were developed to assess the accuracy of recorded culling classifications. RESULTS: For 209 of the 923 (23%) sows, the farm-reported culling classification was judged to be inaccurate. The culling code was considered to be inaccurate for 62 of 322 (19%) sows reportedly culled because of old age, 48 of 172 (28%) sows reportedly culled because of failure to conceive, 31 of 90 (34%) sows reportedly culled because of poor body condition, and 23 of 73 (32%) sows reportedly culled because of poor farrowing productivity. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that for commercial swine farms, farm-reported culling code classifications were frequently inaccurate. This degree of inaccuracy may cause severe limitations for studies that rely on farm-reported assessments of clinical conditions. 相似文献
7.
Over a 4-year period, the annual number of culled sows in 9 Danish herds averaged 54.8 per cent of the year-sows and the number of culled sows in per cent of total number of farrowings averaged 25.8 (Table I). -- The culling rate varied considerably from herd to herd within the same year and from year to year (Tables I and II); however, the average annual culling rate for all the herds only presented small variations (Table II). The average number of litters reared per sow before culling was 3.6. The culling rate was higher in pedigree herds than in commercial herds, and it was highest in the small pedigree herds (Table III). The hygiene level in the herds and the introduction of new female breeding stock did not influence the culling rate (Table IV). A proportionally lower percentage of the sows was culled in herds where the dry and pregnant sows were housed in stalls and/or were tethered, as compared to herds where these sows were housed in pens (Table V). -- The culling rate in the age groups of sows with less than 8 farrowings remained at approximately the same level (Table VI). The main reason for culling was infertility problems, which were recorded in 41.4 per cent of the culled sows, while 16.7 per cent of the sows were culled because their litters were poor and/or small (Table VII). The mortality rate among the culled sows was 11.9 (Table VII), and the main causes of death were chronic pyogenic infections, which occurred in 25.5 per cent of the fatal cases (Table VIII). Certain aspects concerning the recording and calculation of culling rates in the different herds are discussed and it is emphasized that the culling rate per se may not have any direct relationship to the productivity in the herd. 相似文献
8.
The development of a simulation model, "JohneSSim", was part of a research program aimed at designing a national Johne's disease control program for The Netherlands. Initially, the focus was mainly directed towards different compulsory "test-and-cull" strategies. However, the results from the JohneSSim model showed that eradication of Johne's disease based on such strategies would not be possible within 20 years and that it was also economically unattractive. However, improved calf management seemed to be more effective in reducing the prevalence within the same time period. Simulation of a strategy using an "ideal test" (80% sensitivity in all infected animals) showed a considerably faster decrease in prevalence. However, this strategy proved to be economically unattractive because of the high culling rate of (young) test-positive animals. The simulation model was also adapted to study beef cow herds. However, the results indicated that none of the strategies were able to reduce the mean true prevalence to almost zero for such herds. Only strategies based on "separation of calves and adult animals" proved to significantly reduce the prevalence but such a strategy is unpractical and uneconomic for Dutch beef cow herds. Due to this finding and the relative low number of Dutch beef cow farms, first priority has been given to the development of a Johne's disease control program for dairy farms. Based on the results of the "JohneSSim" model, the new national voluntary Johne's disease control program for dairy, Paratuberculosis Program Netherlands (PPN), started in September 2000. The PPN is based on a stepwise improvement of calf hygiene, with little dependency on "test and culling". The model results indicated that, if dairy farmers consistently carried out the necessary management adaptations, PPN considerably decreased prevalence and that it was economically more attractive than any previous plans. 相似文献
9.
The study describes the profiles of culled cows in order to assess the possible contribution to economic losses due to health disorders. Data regarding dates of birth, final calving and culling, parity at culling, milk yield at the two first test-days of the final lactation and reason(s) for culling were collected in a 5-year survey, carried out from 1989 to 1994 in 84 commercial Holstein farms in western France. Polytomous logistic regression was used to assess the relationship between parity, calving-to-culling interval, milk yield and eight groups of primary culling reasons (i.e. udder disorders; infertility or reproductive disorders; lameness or foot/leg defects; emergency culling reasons; other health disorders; low milk yield; sales for dairy purpose; and other voluntary culling reasons). Out of a total of 5133 culled cows, the proportions of culls, for each of these groups of reasons, were 12.4, 28.4, 2.7, 3.9, 4.6, 16.7, 5.9, and 25.4%, respectively. Cows culled for udder disorders left the herd earlier in lactation and were more frequently at parities 4–6 than cows culled for voluntary reasons. In contrast, cows culled for infertility were younger and culled later within lactation. They were also higher yielding cows than those culled for other reasons. Cows culled for lameness were similar to those of the voluntarily culling group. Cows culled for emergency reasons were more frequently younger cows in early lactation. Cows culled for other health disorders left the herd early in lactation, but at a higher parity than the voluntarily culled cows. These results suggest that most of the culls related to health could be contributing to economic loss. However, special priority should be given to reduce culling for reproductive problems, which is the most costly exit reason. 相似文献
10.
A Weibull mixed survival model was used to study the effect of a change in the housing system on length of productive life (LPL) in dairy cows. The data set included records on 71,469 Swiss Brown cows in 1674 farms in eastern and central Switzerland. About 36% of the records were right-censored. The observation period lasted from January 1, 1988 to May 1, 2001. During this period, 517 farms changed their housing conditions from a tie-stall barn to a loose housing system. Besides a random time-dependent effect of herd–year–season, the model included fixed effects of housing system, lactation number and stage of lactation, within herd and parity production level (all time-dependent), and age at first calving (time-independent). All effects had a significant effect on LPL at a level of p < 0.001. Cows in loose housing systems showed the lowest risk ratios of being culled (0.93) compared to the reference system tie-stall barn (1.00). The highest relative culling rate (1.09) was observed within the changing period from tie-stall barn to loose housing system. Within the first three lactations, the relative culling risk increased stepwise with lactation stage. The hazard slightly increased from first until lactation number 8 and higher. The relative culling rates were highest (2.22) for cows yielding less than 90% compared to herd-mates of the same lactation number, whereas the lowest risk ratios were estimated for animals yielding more than 110% compared to their reference group (0.64). When heifers were older than 3 years at first calving, there was a tendency towards a higher relative culling risk (1.06). 相似文献
11.
Helminth infection, species diversity (proportion of each species in the community), species number, intensity of infection and anthelmintic resistance were investigated in 16 dairy-goat farms of south-western France. The aim of the study was to estimate which breeding management factors may affect diversity and intensity of infection. Anthelmintic resistance was investigated because this factor may modify composition of nematode communities. Farm history and breeding management were recorded by means of a questionnaire. Natural and experimental infections were compared to determine which strategy was the best to estimate diversity index and number of species from nematode community of a whole herd. A total of 17 species of helminths, among which 14 nematodes, one cestode (Moniezia spp.) and two trematodes (Paramphistomum daubneyi and Dicrocoelium lanceolatum) were recovered in the 26 necropsied culled goats. One culled goat worm burden represented conveniently species number but not species diversity (Shannon index) of parasite community harboured in the whole herd. Experimental sheep infection with larvae from pooled faeces of 15 goats was the best strategy to estimate species diversity in farms. Diversity could be predicted from the number of farms from which goats originated at constitution of the herd, the duration of goat winter withdrawal from pastures, and intensity of infection. Anthelmintic resistance was correlated with the number of farms of origin, area of permanent pastures and intensity of infection. The strategy adopted for the herd constitution was a critical step as species diversity and risk of anthelmintic resistance increased with the number of farms of origin. Intensity of infection was negatively correlated with species diversity. This suggested that more diverse communities were better controlled by the host, in agreement with the widespread statement that diversity would beget stability. 相似文献
12.
Busani L Valsecchi MG Rossi E Toson M Ferrè N Pozza MD Marangon S 《Veterinary journal (London, England : 1997)》2009,181(2):171-177
In 1999-2000, Italian poultry production was disrupted by an H7N1 virus subtype epidemic of highly pathogenic avian influenza (HPAI). The objectives of the present study were to identify risk factors for infection on poultry farms located in regions that had the highest number of outbreaks (Veneto and Lombardia) and the impact of pre-emptive culling as a complementary measure for eradicating infection. A Cox regression model that included spatial factors, such as the G index, was used. The results confirmed the relationship between risk of infection and poultry species, production type and size of farms. The effectiveness of pre-emptive culling was confirmed. An increased risk of infection was observed for poultry farms located near an infected farm and those at altitudes less than 150m above sea level. The measures for the control and eradication of AI virus infection need to consider species differences in susceptibility, the types of production and the density of poultry farms in the affected areas. 相似文献
13.
Noordegraaf AV Jalvingh AW de Jong MC Franken P Dijkhuizen AA 《Preventive veterinary medicine》2000,44(1-2):21-42
Several countries within the EU have successfully eradicated bovine herpesvirus type I (BHV1), while others are still making efforts to eradicate the virus. Reintroduction of the virus into BHV1-free areas can lead to major outbreaks - thereby causing severe economic losses. To give decision-makers more insight into the risk and economic consequences of BHV1 reintroduction and into the effectiveness of various control strategies, we developed the simulation model InterIBR. InterIBR is a dynamic model that takes into account risk and uncertainty and the geographic location of individual farms. Simulation of a BHV1-outbreak in the Netherlands starts with introduction of the virus on a predefined farm type, after which both within-farm and between-farm transmission are simulated. Monitoring and control measures are implemented to simulate detection of the infection and subsequent control. Economic consequences included in this study are related to losses due to infection and costs of control. In the simulated basic control strategy, dairy farms are monitored by monthly bulk-milk tests and miscellaneous farms are monitored by half-yearly serological tests. After detection, movement-control measures apply, animal contacts are traced and neighbour farms are put on surveillance. Given current assumptions on transmission dynamics, we conclude that a strategy with either rapid removal or vaccination of infected cattle does not reduce the number of infected farms compared to this basic strategy - but will cost more to control. Farm type with first introduction of BHV1 has a considerable impact on the expected number of secondarily infected farms and total costs. To limit the number of infected farms and total costs due to outbreaks, we suggest intensifying the monitoring program on farms with a high frequency of cattle trade, and monthly bulk-milk testing on dairy farms. 相似文献
14.
Cows are culled at a relatively low age, which causes considerable economic loss. The annual culling rate in the Netherlands has increased from 18.8 per cent in 1951 to 25-30 per cent of the average number of cows in more recent years. The productive life is now about 3.5 years. On the thirty farms of the program group and thirty-one farms of the control group, the main reasons for culling were reproductive failure followed by mastitis and teat injuries. About 60 per cent of culling was due to health problems, the other 40 per cent to low productive capacity, old age, poor workability etc. The annual culling rate varied per farm per year but also per month. The moment of culling in the current lactation, the slaughter value and the age differed per reason. The calculated loss of forced replacement consists of reduction in both production prior to culling and slaughter value. Additionally, there is an idle production period due to lack of an immediate replacement. The biggest loss is caused by lost future income. There was a considerable difference per farm in the loss caused by culling for health problems. A low culling rate due to health problems was associated with longer longevity and a relatively lower loss. Tangible effects due to changes in the farm culling policy may not be evident for some years. The reduction in loss of culling in the program farms compared with the controls was small because the duration (2 1/2 years) of the herd health and management program was too short.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
15.
Classical swine fever (CSF) outbreaks may result in huge economic losses to countries with densely populated pig areas (DPLAs). The EU minimum control measures require depopulation of infected farms, movement restrictions, zoning and surveillance (EU Minimum strategy). Emergency vaccination is authorised for DPLAs although the EU Minimum strategy plus culling in a 1-km ring around infected premises is preferred. Nonetheless, vaccination in a 2-km ring has been found equally effective as 1-km ring culling using stochastic modelling. Alternatives control measures (e.g. antiviral agents, in particular small molecule inhibitors of the CSFV replication) are being explored. Hence, the present study was set up to simulate inter-herd CSFV spread when antiviral molecules are supplemented to pig feed in a 1-km ring around infected farms. The effectiveness of the antiviral strategy for containing CSF outbreaks was compared to six other control scenarios including the EU Minimum strategy, the EU preferred policy for DPLAs and the use of 2-km ring vaccination. The InterSpread Plus model was adapted to the 2006 Belgian pig population and outbreak simulations were performed with a fast spreading CSFV strain entering a DPLA in Belgium. Four out of the seven control strategies resulted in outbreaks that were controlled by the end of the simulation period (i.e. 365 days). The distributions of the number of infected herds and the duration of the predicted outbreaks for these four control strategies were not different. This is the first report investigating CSF outbreak containment using antiviral molecules. Although antiviral supplementation was not found to perform any better than some other conventional strategies, such as pre-emptive culling and emergency vaccination, it might be worthwhile considering it further as additional tool in a response to CSF outbreaks. 相似文献
16.
Records of length of productive life, from first farrowing to culling, of 16,464 Large White purebred sows from SUISAG were studied using survival analysis. The major aims of the study were to model the risk of culling within parity and to assess the influence of exterior traits, such as the number of teats or feet and leg scores, on culling. Culling was concentrated at the first day after each farrowing or at the first day after weaning. Weaning itself was mostly between 21 and 49 d after farrowing, with an average weaning age of 35 d. Because of the definition of culling date used, there was practically no risk of culling from these periods. The culling rates at different periods suggested a modeling of the baseline hazard function within parity instead of over the entire productive life of the animals. A piecewise Weibull function and a simple graphical method to validate its adequacy were proposed for sow longevity analysis. The risk of culling increased with older parities (P < 0.001) and with decreasing litter size at weaning (P < 0.001). The exterior traits analyzed (number of teats, and feet and leg scores, on a scale from 1 to 7) had a moderate effect on the risk of culling compared with other factors but were still influential on survival, productive life expectancy, and annual replacement rate. Sows with less than 13 good teats had 1.35 times greater risk of being culled than sows with more good teats (P < 0.05). Sows with an X-O rear leg score of 2 had 1.4 times greater risk of being culled than sows with an intermediate score of 4 (P < 0.05). Sows at the optimum score of 4 for the size of inner claws of the rear leg had 0.83 times less risk of being culled (P < 0.01) than sows with scores of 2 and 3. Furthermore, when a phenotypic index for feet and legs was used to group these variables, the effect was highly significant (P < 0.001). Therefore, a means to improve longevity is through phenotypic selection of replacement gilts based on exterior traits: gilts with 13 or less good teats or with extreme feet and leg scores should be culled. From a genetic point of view, sows with the best value in the current index for exterior traits had a lower risk of culling (P < 0.01), and therefore, it is possible to obtain a response for sow longevity via indirect selection for exterior traits. From 1999 to 2003, the trend has been to eliminate extreme animals on exterior traits. This may partly explain the improvement of sow length of productive life longevity from 560 d in 2000 to nearly 710 d in 2003 observed in the data set. 相似文献
17.
Survival analysis of factors affecting culling early in the productive life of Holstein-Friesian cattle in Kenya 总被引：1，自引：0，他引：1
Holstein-Friesian cattle raised in tropical environments pose a challenge due to genotype by environment interactions which may lead to higher rates of involuntary culling and reduce profit margins obtainable. This study assessed factors influencing culling within the first three parities of Holstein-Friesian cattle raised on four large-scale farms in Kenya using a Cox proportional hazard model. Differences in length of productive life (LPL) due to differences in area of origin of sires were also assessed in an attempt to determine possible adaptations by specific genotypes to the Kenyan environment. Environmental effects of herd, year-season, parity, sire area of origin, milk yield class and stage of lactation all significantly affected LPL. Daughters of sires born in Kenya tended to have a higher risk of being culled compared to those from other countries. Part of this higher risk was linked to a higher culling of low-producing cows. Further analyses and possibilities for the inclusion of LPL in selection criteria for sires to be used in Kenya should be encouraged. 相似文献
18.
Salmonella enterica subsp. enterica-serotypes lead to periodically increased morbidity and mortality in cattle herds. The bacteria can also lead to serious infections in humans. Consequently, Denmark has started a surveillance and control programme in 2002. The programme focuses on Salmonella Dublin which is the most prevalent and most persistent serotype in the Danish cattle population. A field study in 10 dairy herds with persistent Salmonella infections was carried out over three years to gain experience with control procedures including risk assessment, targeted control actions and test-and-cull procedures. From autumn 2003 until end of 2006 quarterly milk quality control samples from all lactating cows and biannual blood samples from all young stock above the age of three months were tested using an indirect antibody ELISA. The most recent and previous test results were used to categorise all animals into risk groups. These risk groups and all individual ELISA-results were communicated to the farmers as colour-coded lists four to six times per year. Farmers were advised to manage the risk of Salmonella transmission from cattle with repeatedly high ELISA results (flagged as "red") or cows with at least one recent moderately high ELISA result (flagged as "yellow") on the lists. Risk management included, e.g. culling or separation of the cows at calving. We analysed culling decisions using two models. For heifers a hierarchical multivariable logistic model with herd as random effect evaluated if animals with red and yellow flags had higher probability of being slaughtered or sold before first calving than animals without any risk flags. For adult cows a semi-parametric proportional hazard survival model was used to test the effect of number of red and yellow flags on hazards of culling at different time points and interactions with prevalence in the herd while accounting for parity, stage of lactation, milk yield, somatic cell count and the hierarchical structure of the data with animals clustered at herd level. This study illustrates how investigation of culling decisions made by herd managers when they have access to test-status of individual animals and overall apparent prevalence during control of an infection can lead to useful new knowledge. Overall herd managers were more likely to cull cattle with increasing number of yellow and red flags than animals with no flags. However, cattle were more likely to be culled with yellow and red flags during times with low or medium high within-herd seroprevalence than at times with high seroprevalence. These results are valuable knowledge for modelling and planning of control strategies and for making recommendations to farmers about control options. 相似文献
19.
Schneider Mdel P Strandberg E Emanuelson U Grandinson K Roth A 《Preventive veterinary medicine》2007,80(2-3):179-192
The interaction of the effects of pregnancy status and veterinary-treated clinical mastitis on culling in Swedish dairy cattle was analyzed with survival analysis. The data were from 978,780 cows with first calvings between 1988 and 1996. Four breeds (Swedish Red and White (SRB), Swedish Friesian (SLB), Swedish Polled Breed and Jersey) were included in the analysis, together with the SRB x SLB crossbreds. Length of productive life was defined as the number of days between first calving and culling or censoring (end of data collection). The model (Weibull proportional hazard) included the interaction of parity by pregnancy status by veterinary-treated clinical mastitis, peak test-day milk-yield deviation within herd-year-parity, age at first calving, year by season, region, breed, herd production level, and the random effect of herd. The effects of pregnancy status and veterinary-treated clinical mastitis were modeled as time-dependent covariates. The lactation was divided into five stages during which a veterinary-treated clinical mastitis and culling might occur and in which the pregnancy status was assumed to be known and culling could occur. Open cows had a pronounced effect on culling: they had a very high risk of being culled in all lactations, and it was even higher if they were treated for mastitis in early lactation. For pregnant cows, the later they got pregnant during the lactation, the greater their risk to be culled. The risk associated with cases of veterinary-treated clinical mastitis remained important throughout the lactation. 相似文献
20.
《畜牧与生物技术杂志(英文版)》2017,(4)
Background: The aim of the study was to analyze the lifetime and culling reasons for boars used in insemination centers(AI centers).Methods: The data collected from 355 culled boars from 1998 to 2013 included: age at start of semen collection,boar herd life, culling reason, daily gain and lean meat content, and number of ejaculates not meeting sales requirements after dilution. Culling reasons were divided into 7 groups: low semen value(LSV), low or lack of libido(LL), leg problems(LP), infectious diseases(ID), old age(OA), reduced demand for semen from the given boar(RD),and others(OT).Results: The most common culling reasons for boars were LSV(23.7%) and RD(22.5%). It was observed that the lowest daily gains were noted in boars culled due to OA. Boars culled due to OA and RD were maintained in production for the longest time(over 1000 d), for LSV and ID retention was about 700 d, and due to LL below 400 d. The survival probability was over 0.9 until 1.5 yr, and just over 0.2 until 4 yr. The highest relative frequency was observed in the 36 ~(th) and 42 ~(nd) mo of life(over 16%). Hazard risk analysis revealed a more than 10 times higher risk of culling in the case of LL, ID or OT, in comparison to OA.Conclusions: The results can be used as a direct point of reference for the identification of emerging problems in AI boar exploitation and the development of an appropriate culling policy in AI centers. 相似文献