As the global competition among dairy farms for the natural resources (e.g. land, feed, water) in... more As the global competition among dairy farms for the natural resources (e.g. land, feed, water) increases, it is getting more and more vital to use the resources available as efficiently as possible. The improvement of herd health management, that is, the reduction of prevalence of major diseases in dairy farms, such as mastitis and reproductive disorders, and, that of their deteriorating effects on production parameters (less output from the same amount of input) and consequently the greater profitableness can greatly contribute to successfully run a dairy, thus, to the preservation of jobs generating disposable income in the rural areas. Additionally, in many regions there is lack of manure in the plant production, therefore, from the point of view of environmental protection, the sustainable milk production giving manure with the highest value would also be very important. Several methods and practices have been developed in order to help herd managers reduce the detrimental effec...
The routine monitoring of the efficiency of reproductive programs is necessary in large-scale dai... more The routine monitoring of the efficiency of reproductive programs is necessary in large-scale dairy herds in the 21 st century. The importance of the economic evaluation of these programs is increasing, as well, since many thousands of euros are spent on reproductive management on a farm. However, different interpretations of reproductive indices cause difficulties among professionals when comparing the parameters of their farms to that of another dairy. Last, but not the least, proper and uniform interpretation of these parameters is a prerequisite in performing correct economic evaluations. Some indices (e.g. calving interval) are classically used for monitoring some aspects of cows' fertility, however they are less adequate to evaluate the reproductive performance of a farm as a whole. Moreover, variations can be observed in the calculation approaches of certain reproductive parameters among herds, and the figures may be further biased due to the exclusion of some group of animals or the use of a hormonal synchronization program. In this study, the authors present the main reproductive indices from a practical point of view and a more comprehensive way of calculating the indices is shown. The advantages and disadvantages of each parameter are also discussed. Special attention is paid to the possible errors which may lead to the miscalculation and misinterpretation of the parameters.
Poor estrus expression is one of the major reasons of reproductive inefficiency on large dairy fa... more Poor estrus expression is one of the major reasons of reproductive inefficiency on large dairy farms. Farm managers usually try to overcome this difficulty by using various estrus detection aids (e.g. pedometers, accelerometers, tail chalk), however, each method has its own limitations. Estrus detection aids generally lead to increased heat detection rate, better timing of inseminations relative to the time of ovulation, and ultimately, improved pregnancy rate. Some studies, however, did not find any benefit from the use of estrus detection aids, which is explained by (1) using the same rules on when to start inseminating heifers and cows as prior to the introduction of the new technology, and (2) by the widespread use of hormonal synchronization protocols that can potentially mask the effect of estrus detection aids. Economic outcome of the investment into estrus detection aids depends on the circumstances of the farm, although the reduction of labour cost can usually be expected. Despite efforts made towards the development of new estrus detection technologies, due to the high prevalence of anovular cows hormonal protocols are still required.
The aim of our study was to investigate the association of per os calcium supplementation with th... more The aim of our study was to investigate the association of per os calcium supplementation with the occurrence of animal health disorders in a large Hungarian dairy herd. The treatment of cows consisted of two per os calcium boluses on the day after calving. The probability of insemination, culling, mastitis, uterine disorders, and lameness were compared in the treated (n=168) vs. control cows (n=136) within 60 days in milk. Data were analysed by logistic regression. Cows that received calcium boluses were 8.09-times more likely to be inseminated (P<0.0001) and 0.34-times less likely to be culled (P=0.001) within 60 days in milk. Treated cows had reduced odds of developing mastitis (odds ratio, OR=0.50, P=0.0387) and lameness (OR=0.15, P=0.005) compared to their control herdmates. Per os calcium boluses can improve animal health in early lactation in high producing dairy cattle.
Article history: Abstract The aim of this study was to survey the milk yield, milk quality and mi... more Article history: Abstract The aim of this study was to survey the milk yield, milk quality and milking technology on Hungarian large-scale (>50 cows) dairy farms and to evaluate the possible impact of milking parlour type on milk production and quality (somatic cell count). The survey was performed by using a questionnaire on 377 Hungarian dairy farms in 2017. Farms were categorized according to their milking parlour types (herringbone, parallel, carousel and others). The average SCC on the Hungarian dairy farms was high (405,199 SCC/ml). Farms using herringbone milking system had the lowest milk quality (429.240 SCC/ml) and milk yield (27.01 kg/day). The type of milking parlour had an impact on milk quality (p=0.05) and milk yield (p=0.03).
Q fever is a disease of high zoonotic potential, but interest in its causative agent is rather lo... more Q fever is a disease of high zoonotic potential, but interest in its causative agent is rather low although it causes some public health problems in Hungary. The prevalence of Q fever is highly variable by country. The main reservoirs of the disease are the same domestic ruminant species everywhere, but the epidemiological profile depends on the features of the specific reservoir. The aim of this large-scale study was to demonstrate the importance of Q fever in different species as a possible source for human infection in most regions of Hungary. A total of 851 serum samples from 44 dairy farms, 16 sheep flocks, 4 goat farms and 3 zoos located in different parts of Hungary were tested. The presence of antibodies to Coxiella burnetii was surveyed in dairy cattle (n = 547), goats (n = 71), sheep (n = 200) and zoo animals (n = 33). The animal species tested in Hungary showed different seroprevalence values of C. burnetii infection. Seropositivity by the enzyme-linked immunosorbent assa...
Asian-Australasian Journal of Animal Sciences, 2019
Objective: The aim of our study was to determine the associations of heifer reproductive performa... more Objective: The aim of our study was to determine the associations of heifer reproductive performance with survival up to the first calving, first-lactation milk yield, and the probability of being culled within 50 days after first calving.Methods: Data from 33 large Holstein-Friesian commercial dairy herds were gathered from the official milk recording database in Hungary. The data of heifers first inseminated between January 1, 2011 and December 31, 2014 were analyzed retrospectively, using Cox proportional hazards models, competing risks models, multivariate linear and logistic mixed-effects models.Results: Heifers (n = 35,128) with younger age at conception were more likely to remain in the herd until calving, and each additional month in age at conception increased culling risk by 5.1%. Season of birth was related to first-lactation milk yield (MY1; n = 19,931), with cows born in autumn having the highest milk production (p<0.001). The highest MY1 was achieved by heifers that...
The aim of the research was to evaluate the milk quality in the automatic milking system (milking... more The aim of the research was to evaluate the milk quality in the automatic milking system (milking robot) and milking parlor. The somatic cell count is the indicator of inflammation in the udder. If milk ejection is inhibiting, inflammation develops in the udder. Stress is one of the reasons to inhibit milk ejection. As a result the somatic cell count increases but the milk yield decreases. The stress level is higher for primiparous compared with multiparous. The milk yield was significantly greater in the milking robot milked cow milk (28.5±0.60 kg). The somatic cell count was significantly greater in the parlor milked cow milk in the 1 st (319.0±90.69 thousand per ml) and 2 nd (119.0±26.46 thousand per ml, p < 0.05) recordings. The milk yield was not significantly different in the multiparous group. The milk fat and protein contents were greater in the parlor group. The somatic cell count of the multiparous group was significantly greater in the 3 rd recording (146.0±43.92 thousand per ml, p < 0.05). Linear type traits of udder were not different-neither primiparous nor multiparous. Milk ejection was not affected by the linear type of the udder. The stress factor which is responsible for elevated somatic cell count could be the environment factor.
The aim of our study was to quantify the effect of twinning and stillbirth on the main reproducti... more The aim of our study was to quantify the effect of twinning and stillbirth on the main reproductive parameters, and to estimate the resulting economic loss on large-scale commercial dairy farms. The data of 3.660 calvings that occurred on five large Hungarian Holstein-Friesian farms in 2016 and 2017 were analysed retrospectively. Information about twin calvings, stillbirths and uterine treatments were gathered. The main reproductive indices (i.e. calving to conception interval-CCI, services per conception-SPC, and first service conception risk-CR1) were calculated based on cow-level data. Statistical analyses were performed by using linear and logistic regression, and Dunnett-test. The economic losses related to twinning and stillbirth were estimated by partial budget analysis (1 EUR = 320 HUF). Overall, twinning and stillbirth occurred in 4.1 % and 6.9 % of the calving events. Twinning was more likely, whereas stillbirth was less likely in multiparous cows (odds ratio [OR]: 4.18 and 0.64, P<0.0001 and P=0.0015, respectively). Following twin calving, CCI and SPC were increased by 12.8 days and by 2.8, respectively, whereas CR1 was reduced by 7.1 percentage points. Twinning caused an estimated loss of 50.4 EUR/case. The analysed reproductive parameters were not impaired after stillbirth. Although, the reduction of calf number and the excess semen usage led to 112.5 EUR estimated loss per stillbirth case, on average. Twinning and stillbirths are significant sources of economic loss on dairy farms, therefore, their prevalence should be reduced.
As a result of the increase in herd size and the intensification of production, the complexity of... more As a result of the increase in herd size and the intensification of production, the complexity of reproductive management has been growing in dairy herds. The aim of our study was to examine the associations of management practices and reproductive performance in Holstein cows on large commercial dairy farms. Management practices applied to cows were surveyed between 22 May and 6 November 2015 in 34 large Holstein-Friesian dairy herds in Hungary. Individual data of 23 784 cows that calved between 1 January 2014 and 31 December 2014 in the surveyed herds were gathered. Associations between the management practices and the reproductive parameters were analyzed by mixed effects models. Regarding heat abatement we found that ventilation with sprinklers was associated with the shortest breeding interval (P<0.01), the shortest calving to conception interval (P<0.01), and the highest odds of being pregnant by 200 days in milk (P<0.01). Solely ventilation showed similar (P>0.05)...
The role of management functions in successful enterprise performance, 2016
The aim of this study is to assess the average values of the most commonly used reproductive indi... more The aim of this study is to assess the average values of the most commonly used reproductive indices, to introduce more recent parameters for measuring reproductive performance and to suggest reference values for the latter, based on a survey carried out in Hungary. Data were collected from February to May 2015, and altogether 12,723 cows were included from 21 herds in six counties. Average values of the conventional indices were: SP: 160 days, SPC: 4.27 and CR1: 22%. The SP, SPC and CR1 were much poorer than the former reference values even in the best herds. It was proven that PR is suitable for a quick review of the reproductive performance; therefore this parameter is advised for routine use in dairies. In this study, cPR was introduced as a novel parameter that is destined for overcoming inaccuracies stemming from Hungarian culling policy. Suggested reference values of the more recent parameters are: PR: 9.4%, cPR: 18%. %PORP is preferable to %Preg, since it applies only to the reproductive proportion of the herd, and its value is not influenced by the seasonal changes (calving, culling) to such a great extent and for such a long time. The use of some relevant parameters (PR, cPR, CR1, SP, %PORP) is enough for the daily routine, but in-depth analysis is required when the reproductive performance is diminishing.
The authors quantified the production and economic losses caused by left displaced abomasum (LDA)... more The authors quantified the production and economic losses caused by left displaced abomasum (LDA) in a Hungarian 930-cow dairy herd between 1 January 2012 and 31 December 2014. Decision analysis was also performed regarding the profitability of the left flank abomasopexy. Losses were quantified by a partial budget model based on the performance of 178 LDA-positive cows, whereas the postoperative production of 166 cows was included in the decision analysis. The average annual prevalence of LDA was 6.6%, being highest in the first lactation. LDA-positive cows produced 303 kg less milk throughout their lactation and 1339 kg less milk annually than the control group. The LDA significantly deteriorated the cows' reproduction (p < 0.0001); the calving interval was 58, the lactation 50 days longer, respectively, and the LDA-positive cows required 1.29 more inseminations and additional 57 days to conceive. Average losses related to LDA summed up to 612 EUR per case on average. Increa...
The authors reviewed the factors related to the accuracy of the early pregnancy diagnosis methods... more The authors reviewed the factors related to the accuracy of the early pregnancy diagnosis methods used on dairy farms, and summarized the results of the studies on the production and economic consequences of early pregnancy diagnosis. Transrectal ultrasonography and pregnancy-associated glycoprotein tests allow for accurate diagnosis about one week earlier than rectal palpation. Therefore, the breeding interval can be shortened and days open can be reduced. However, a drawback of the early diagnosis is that a larger proportion of the naturally occurring pregnancy losses is observed. Since iatrogenic pregnancy loss is more costly than the increase in the number of open days, it is important to use a diagnostic method with high sensitivity and negative predictive value. The economic advantage of early pregnancy diagnosis is higher in herds with poor reproductive performance. Higher cost per day open and larger herd size result in shorter payback time of the investments in early pregnancy diagnosis methods.
As the global competition among dairy farms for the natural resources (e.g. land, feed, water) in... more As the global competition among dairy farms for the natural resources (e.g. land, feed, water) increases, it is getting more and more vital to use the resources available as efficiently as possible. The improvement of herd health management, that is, the reduction of prevalence of major diseases in dairy farms, such as mastitis and reproductive disorders, and, that of their deteriorating effects on production parameters (less output from the same amount of input) and consequently the greater profitableness can greatly contribute to successfully run a dairy, thus, to the preservation of jobs generating disposable income in the rural areas. Additionally, in many regions there is lack of manure in the plant production, therefore, from the point of view of environmental protection, the sustainable milk production giving manure with the highest value would also be very important. Several methods and practices have been developed in order to help herd managers reduce the detrimental effec...
The routine monitoring of the efficiency of reproductive programs is necessary in large-scale dai... more The routine monitoring of the efficiency of reproductive programs is necessary in large-scale dairy herds in the 21 st century. The importance of the economic evaluation of these programs is increasing, as well, since many thousands of euros are spent on reproductive management on a farm. However, different interpretations of reproductive indices cause difficulties among professionals when comparing the parameters of their farms to that of another dairy. Last, but not the least, proper and uniform interpretation of these parameters is a prerequisite in performing correct economic evaluations. Some indices (e.g. calving interval) are classically used for monitoring some aspects of cows' fertility, however they are less adequate to evaluate the reproductive performance of a farm as a whole. Moreover, variations can be observed in the calculation approaches of certain reproductive parameters among herds, and the figures may be further biased due to the exclusion of some group of animals or the use of a hormonal synchronization program. In this study, the authors present the main reproductive indices from a practical point of view and a more comprehensive way of calculating the indices is shown. The advantages and disadvantages of each parameter are also discussed. Special attention is paid to the possible errors which may lead to the miscalculation and misinterpretation of the parameters.
Poor estrus expression is one of the major reasons of reproductive inefficiency on large dairy fa... more Poor estrus expression is one of the major reasons of reproductive inefficiency on large dairy farms. Farm managers usually try to overcome this difficulty by using various estrus detection aids (e.g. pedometers, accelerometers, tail chalk), however, each method has its own limitations. Estrus detection aids generally lead to increased heat detection rate, better timing of inseminations relative to the time of ovulation, and ultimately, improved pregnancy rate. Some studies, however, did not find any benefit from the use of estrus detection aids, which is explained by (1) using the same rules on when to start inseminating heifers and cows as prior to the introduction of the new technology, and (2) by the widespread use of hormonal synchronization protocols that can potentially mask the effect of estrus detection aids. Economic outcome of the investment into estrus detection aids depends on the circumstances of the farm, although the reduction of labour cost can usually be expected. Despite efforts made towards the development of new estrus detection technologies, due to the high prevalence of anovular cows hormonal protocols are still required.
The aim of our study was to investigate the association of per os calcium supplementation with th... more The aim of our study was to investigate the association of per os calcium supplementation with the occurrence of animal health disorders in a large Hungarian dairy herd. The treatment of cows consisted of two per os calcium boluses on the day after calving. The probability of insemination, culling, mastitis, uterine disorders, and lameness were compared in the treated (n=168) vs. control cows (n=136) within 60 days in milk. Data were analysed by logistic regression. Cows that received calcium boluses were 8.09-times more likely to be inseminated (P<0.0001) and 0.34-times less likely to be culled (P=0.001) within 60 days in milk. Treated cows had reduced odds of developing mastitis (odds ratio, OR=0.50, P=0.0387) and lameness (OR=0.15, P=0.005) compared to their control herdmates. Per os calcium boluses can improve animal health in early lactation in high producing dairy cattle.
Article history: Abstract The aim of this study was to survey the milk yield, milk quality and mi... more Article history: Abstract The aim of this study was to survey the milk yield, milk quality and milking technology on Hungarian large-scale (>50 cows) dairy farms and to evaluate the possible impact of milking parlour type on milk production and quality (somatic cell count). The survey was performed by using a questionnaire on 377 Hungarian dairy farms in 2017. Farms were categorized according to their milking parlour types (herringbone, parallel, carousel and others). The average SCC on the Hungarian dairy farms was high (405,199 SCC/ml). Farms using herringbone milking system had the lowest milk quality (429.240 SCC/ml) and milk yield (27.01 kg/day). The type of milking parlour had an impact on milk quality (p=0.05) and milk yield (p=0.03).
Q fever is a disease of high zoonotic potential, but interest in its causative agent is rather lo... more Q fever is a disease of high zoonotic potential, but interest in its causative agent is rather low although it causes some public health problems in Hungary. The prevalence of Q fever is highly variable by country. The main reservoirs of the disease are the same domestic ruminant species everywhere, but the epidemiological profile depends on the features of the specific reservoir. The aim of this large-scale study was to demonstrate the importance of Q fever in different species as a possible source for human infection in most regions of Hungary. A total of 851 serum samples from 44 dairy farms, 16 sheep flocks, 4 goat farms and 3 zoos located in different parts of Hungary were tested. The presence of antibodies to Coxiella burnetii was surveyed in dairy cattle (n = 547), goats (n = 71), sheep (n = 200) and zoo animals (n = 33). The animal species tested in Hungary showed different seroprevalence values of C. burnetii infection. Seropositivity by the enzyme-linked immunosorbent assa...
Asian-Australasian Journal of Animal Sciences, 2019
Objective: The aim of our study was to determine the associations of heifer reproductive performa... more Objective: The aim of our study was to determine the associations of heifer reproductive performance with survival up to the first calving, first-lactation milk yield, and the probability of being culled within 50 days after first calving.Methods: Data from 33 large Holstein-Friesian commercial dairy herds were gathered from the official milk recording database in Hungary. The data of heifers first inseminated between January 1, 2011 and December 31, 2014 were analyzed retrospectively, using Cox proportional hazards models, competing risks models, multivariate linear and logistic mixed-effects models.Results: Heifers (n = 35,128) with younger age at conception were more likely to remain in the herd until calving, and each additional month in age at conception increased culling risk by 5.1%. Season of birth was related to first-lactation milk yield (MY1; n = 19,931), with cows born in autumn having the highest milk production (p<0.001). The highest MY1 was achieved by heifers that...
The aim of the research was to evaluate the milk quality in the automatic milking system (milking... more The aim of the research was to evaluate the milk quality in the automatic milking system (milking robot) and milking parlor. The somatic cell count is the indicator of inflammation in the udder. If milk ejection is inhibiting, inflammation develops in the udder. Stress is one of the reasons to inhibit milk ejection. As a result the somatic cell count increases but the milk yield decreases. The stress level is higher for primiparous compared with multiparous. The milk yield was significantly greater in the milking robot milked cow milk (28.5±0.60 kg). The somatic cell count was significantly greater in the parlor milked cow milk in the 1 st (319.0±90.69 thousand per ml) and 2 nd (119.0±26.46 thousand per ml, p < 0.05) recordings. The milk yield was not significantly different in the multiparous group. The milk fat and protein contents were greater in the parlor group. The somatic cell count of the multiparous group was significantly greater in the 3 rd recording (146.0±43.92 thousand per ml, p < 0.05). Linear type traits of udder were not different-neither primiparous nor multiparous. Milk ejection was not affected by the linear type of the udder. The stress factor which is responsible for elevated somatic cell count could be the environment factor.
The aim of our study was to quantify the effect of twinning and stillbirth on the main reproducti... more The aim of our study was to quantify the effect of twinning and stillbirth on the main reproductive parameters, and to estimate the resulting economic loss on large-scale commercial dairy farms. The data of 3.660 calvings that occurred on five large Hungarian Holstein-Friesian farms in 2016 and 2017 were analysed retrospectively. Information about twin calvings, stillbirths and uterine treatments were gathered. The main reproductive indices (i.e. calving to conception interval-CCI, services per conception-SPC, and first service conception risk-CR1) were calculated based on cow-level data. Statistical analyses were performed by using linear and logistic regression, and Dunnett-test. The economic losses related to twinning and stillbirth were estimated by partial budget analysis (1 EUR = 320 HUF). Overall, twinning and stillbirth occurred in 4.1 % and 6.9 % of the calving events. Twinning was more likely, whereas stillbirth was less likely in multiparous cows (odds ratio [OR]: 4.18 and 0.64, P<0.0001 and P=0.0015, respectively). Following twin calving, CCI and SPC were increased by 12.8 days and by 2.8, respectively, whereas CR1 was reduced by 7.1 percentage points. Twinning caused an estimated loss of 50.4 EUR/case. The analysed reproductive parameters were not impaired after stillbirth. Although, the reduction of calf number and the excess semen usage led to 112.5 EUR estimated loss per stillbirth case, on average. Twinning and stillbirths are significant sources of economic loss on dairy farms, therefore, their prevalence should be reduced.
As a result of the increase in herd size and the intensification of production, the complexity of... more As a result of the increase in herd size and the intensification of production, the complexity of reproductive management has been growing in dairy herds. The aim of our study was to examine the associations of management practices and reproductive performance in Holstein cows on large commercial dairy farms. Management practices applied to cows were surveyed between 22 May and 6 November 2015 in 34 large Holstein-Friesian dairy herds in Hungary. Individual data of 23 784 cows that calved between 1 January 2014 and 31 December 2014 in the surveyed herds were gathered. Associations between the management practices and the reproductive parameters were analyzed by mixed effects models. Regarding heat abatement we found that ventilation with sprinklers was associated with the shortest breeding interval (P<0.01), the shortest calving to conception interval (P<0.01), and the highest odds of being pregnant by 200 days in milk (P<0.01). Solely ventilation showed similar (P>0.05)...
The role of management functions in successful enterprise performance, 2016
The aim of this study is to assess the average values of the most commonly used reproductive indi... more The aim of this study is to assess the average values of the most commonly used reproductive indices, to introduce more recent parameters for measuring reproductive performance and to suggest reference values for the latter, based on a survey carried out in Hungary. Data were collected from February to May 2015, and altogether 12,723 cows were included from 21 herds in six counties. Average values of the conventional indices were: SP: 160 days, SPC: 4.27 and CR1: 22%. The SP, SPC and CR1 were much poorer than the former reference values even in the best herds. It was proven that PR is suitable for a quick review of the reproductive performance; therefore this parameter is advised for routine use in dairies. In this study, cPR was introduced as a novel parameter that is destined for overcoming inaccuracies stemming from Hungarian culling policy. Suggested reference values of the more recent parameters are: PR: 9.4%, cPR: 18%. %PORP is preferable to %Preg, since it applies only to the reproductive proportion of the herd, and its value is not influenced by the seasonal changes (calving, culling) to such a great extent and for such a long time. The use of some relevant parameters (PR, cPR, CR1, SP, %PORP) is enough for the daily routine, but in-depth analysis is required when the reproductive performance is diminishing.
The authors quantified the production and economic losses caused by left displaced abomasum (LDA)... more The authors quantified the production and economic losses caused by left displaced abomasum (LDA) in a Hungarian 930-cow dairy herd between 1 January 2012 and 31 December 2014. Decision analysis was also performed regarding the profitability of the left flank abomasopexy. Losses were quantified by a partial budget model based on the performance of 178 LDA-positive cows, whereas the postoperative production of 166 cows was included in the decision analysis. The average annual prevalence of LDA was 6.6%, being highest in the first lactation. LDA-positive cows produced 303 kg less milk throughout their lactation and 1339 kg less milk annually than the control group. The LDA significantly deteriorated the cows' reproduction (p < 0.0001); the calving interval was 58, the lactation 50 days longer, respectively, and the LDA-positive cows required 1.29 more inseminations and additional 57 days to conceive. Average losses related to LDA summed up to 612 EUR per case on average. Increa...
The authors reviewed the factors related to the accuracy of the early pregnancy diagnosis methods... more The authors reviewed the factors related to the accuracy of the early pregnancy diagnosis methods used on dairy farms, and summarized the results of the studies on the production and economic consequences of early pregnancy diagnosis. Transrectal ultrasonography and pregnancy-associated glycoprotein tests allow for accurate diagnosis about one week earlier than rectal palpation. Therefore, the breeding interval can be shortened and days open can be reduced. However, a drawback of the early diagnosis is that a larger proportion of the naturally occurring pregnancy losses is observed. Since iatrogenic pregnancy loss is more costly than the increase in the number of open days, it is important to use a diagnostic method with high sensitivity and negative predictive value. The economic advantage of early pregnancy diagnosis is higher in herds with poor reproductive performance. Higher cost per day open and larger herd size result in shorter payback time of the investments in early pregnancy diagnosis methods.
Uploads
Papers by István Fodor