"Clean, green and ethical" animal production. Case study: reproductive efficiency in small ruminants

In response to changes in society and thus the marketplace, we need a vision for the future of our animal industries, including both on-farm and off-farm activities, that is "clean, green and ethical". Using small ruminants as a case study, we describe three "clean, green and ethical" strategies that farmers could use to improve reproductive performance. The first allows control of the timing of reproductive events by using socio-sexual signals (the "male effect") to induce synchronised ovulation in females. The second strategy, "focus feeding", is based on using short periods of nutritional supplements that are precisely timed and specifically designed for each event in the reproductive process (eg, gamete production, embryo survival, fetal programming, colostrum production). The third strategy aims to maximize offspring survival by a combination of management, nutrition and genetic selection for behaviour (temperament). All of these approaches involve non-pharmacological manipulation of the endogenous control systems of the animals and complement the detailed information from ultrasound that is now becoming available. Importantly, these approaches all have a solid foundation in reproductive biology. In several cases, they are currently used in commercial practice, but there is still room for improvement through both basic and applied research. Ultimately, these "clean, green and ethical" tools can be cost-effective, increase productivity and, at the same time, greatly improve the image of meat and milk industries in society and the marketplace.     

How to improve reproductive efficacy from now in Japan? Find out the factors of late lactation to predict postpartum reproductive diseases

Reproductive efficiency and performance in dairy cattle has been declining over the last 20 years in Japan. Recently, this has resulted in serious problems in dairy herds. There have been changes in the animals themselves and in the animal's environment, e.g. the genetic potential for milk yield has improved, the herd size of dairy farms has been expanding, the housing system of dairy cattle has been changing from tie stall to free stall, and total mixed ratio (TMR) feeding systems have become widespread. It is not clear whether the animals have adapted adequately to these environmental changes. Up till now, reproductive management has been undertaken by monitoring animal performance and/or hormonal treatments, and this has resulted in acceptable reproductive performance. However, conception and pregnancy rates have continued to decline, and the calving to calving interval has continued to extend. Consequently, the average parity and the average age at culling in dairy cattle have been declining. The most common causes of culling in dairy cattle are reproductive disorders in Japan. Therefore, in future, prevention of reproductive disorders will be required for both reproductive efficiency and animal welfare. During late pregnancy and the transition from the pregnant, non-lactating state to the non-pregnant, lactating state, dramatic changes are occurring in the dam including an increase in the fetal-placental mass and calving. Thus, the demand for energy, protein and minerals by the conceptus increases, the space within the abdominal cavity and the rumen capacity decreases due to the increased volume of the conceptus, the local immunological relationship between the fetal and maternal placenta dramatically changes, and physiological homeostasis is activated to adapt to these changes. If cattle can't maintain homeostasis before calving, the incidence of reproductive diseases will be greatly increased. We have been examining reproductive, nutritional and immunological factors to predict the occurrence of reproductive disorders as early as possible and to develop strategies to prevent them. It is unlikely that all dairy farms in Japan will be able to improve reproductive performance with general advice, due to the wide variation in feeding systems and management in Japan. Therefore, specific advice needs to be tailored to each herd, based on management systems employed within each herd. We have proposed that it is important to identify common risk factors across herds, to use these factors as an index for disease control and reproductive management and finally to demonstrate the relationship between these factors and fundamental improvement of the reproductive efficiency. We propose this approach with the aim of providing a breakthrough in improving reproductive performance in dairy cattle in Japan. The focus of this review will be that such an approach is important for improvement of the reproductive efficiency in Japanese dairy cows.     

Fertility of dairy cows in Northern Ireland

A comprehensive database was established on the milk production and reproductive performance of dairy cows in 19 selected herds in Northern Ireland, varying in size, management system and genetic merit. Data were obtained for 2471 cows, 1775 of which calved in a second year, and 693 were culled from the herd for specific reasons. The estimated mean rate of heat detection (assessed by the interheat interval during the main breeding season) in all the herds was 71 per cent, with a range from 53 to 92 per cent The average conception rate to first insemination was 37.1 per cent (range 21 to 66 per cent). The average calving interval for the retained cows was 407.2 days (range 359 to 448 days). Twenty-eight per cent of the cows that calved were culled, with infertility being the largest single reason (26.8 per cent of the cows culled). There were major differences in reproductive performance between the herds, but heat detection rate, conception rate and calving interval did not appear to be affeded by a herd's genetic merit. The herds with shorter calving intervals were characterised by better heat detection efficiency (83 v 61 per cent, P<0.01), a shorter interval from calving to first insemination (74 v 97 days; P<0.05), a higher conception rate to first insemination (45 v 34 per cent, P>0.10) and a lower removal rate (23 v 37 per cent, P<0.01). Furthermore, the cows in these herds had lower body condition scores (BCS) in the dry period (3.0 v 3.3; P<0.05) but lost less body condition in early lactation (0.3 v 0.6 BCS units, P<0.05). These results show that dairy herd fertility in Northern Ireland is generally low and similar to that previously reported for England and the USA, but that in some herds changes in herd management practices improved the cows' fertility.     

奶牛产乳热影响因子及预防措施

产乳热是奶牛产犊后泌乳造成血钙水平下降而引发的营养代谢性疾病，其发生病率非常高，对奶牛健康和生产性能影响较大。产乳热增加了奶牛生育性炎症、生殖障碍和内分泌、消化等方面疾病发生的几率，对养殖业造成很大的损失。影响奶牛产乳热的因素有很多，不仅包括奶牛品种、年龄、体况评分、产乳热史等牛自身因子，也包括饲养管理层面的因素，如泌乳天数、干奶期、产犊间隔的控制及奶牛饲料营养水平的调控，还与气候、环境等外界因素相关，这些影响因子往往相互交织，增加了奶牛产乳热的预防和治疗难度。作者综述了奶牛产乳热的发病机理，分析研究了各种因子对奶牛产乳热的影响机制，并介绍了几种预防措施，主要包括对奶牛饲养环境的管理、产犊间隔和泌乳情况的控制和奶牛不同阶段饲料营养水平的调控，以期为降低奶牛产乳热提供理论依据。     

Managing the lactating sow for optimal weaning and rebreeding performance.

Management of the lactating sow influences milk production and subsequent reproduction through changes in nutrient intake. The management goal during lactation is to maximize feed intake. Decreasing the effective environmental temperature, increasing the nutrient density of the lactation diet, maintaining fresh adequate supplies of feed and water, and preventing excess weight gain during the prior gestation period will increase nutrient intake during lactation. Effective environmental temperature of the lactating sow can be maintained in the thermoneutral zone by using drip cooling, increased ventilation rates and flooring materials with superior conductive properties. Sow parity, genetics, litter size, and disease level will also influence feed intake. Management practices must account for these factors and, thus, should be tailored to individual farm situations to ensure adequate nutrient intake and prevent aberrations in subsequent reproductive performance.     

Reproductive performance of Holstein dairy cows in Iran

The objectives of the present study were to describe the current reproductive parameters of Holstein dairy cows in Iran and to determine factors which have a significant effect on reproductive performance with emphasis on high-producing dairy cows. Five large Holstein dairy herds from the major milk production areas of Iran were selected for this study. Reproduction data including parity of dam, calving date, days to first service, days open, number of services, dry period, and occurrence of diseases for cows that calved from 2004 to 2007 were collected from the herds' databases. To determine the effects of year and season of calving, disease status, level of milk production, and parity of dam on reproductive parameters, the proc-mixed procedure in SAS software was used. Overall, data about 8,204 lactation were collected for the study. Results showed that mean (±SD) days open, calving interval, and days to first service for study herds were 134 (±89), 403 (±86), and 67 (±38) days, respectively. Conception rates at the first service and the overall service-conception rate were 41.6% and 41%, respectively. The level of milk production and diseases had significant negative effects on days open and service per conception (P < 0.05); statistical analysis showed that for every 100-kg increase in milk yield, days open will increase by about 0.3 days. However, no significant effect of level of productivity was observed on days to first service. The results of this study indicate that high milk production is a risk factor for decreasing fertility in Iran, like many other parts of the world.     

Performance and limitation of two dairy production systems in the North western Ethiopian highlands

In order to characterise the dairy production systems as well as the productive and reproductive performance of dairy cows in the study area, a total of 256 and 54 dairy farms were used for survey and monitoring data collection, respectively. Based on breed, land size, feed and market accessibility, two major dairy production systems were identified: a rather specialized, urban, and a peri-urban dairy production system. Urban farmers owned larger herds but farmed less land, and sold a greater proportion of liquid milk than peri-urban farmers, who processed more milk. Purchased feed played a more important role for the feed supply of urban than peri-urban farms. Significant breed effects were found for productive and reproductive performance traits. It is concluded that improved breeding and health management, genetic improvement of local breeds and supplementation of poor quality feed resources are the key factors for enhancing productivity of dairy cows and thereby increasing family income from milk production.     

Improved knowledge about conception rates influences the decision to stop insemination in dairy cows

The conception rate in dairy cows is dependent on a number of cow factors such as days in milk and insemination number. Unfortunately, some of these factors were not accounted for in optimal insemination and replacement decision models. By using wrong estimates of the conception rate, the calculated optimal insemination and replacement policy might differ from the real optimal insemination and replacement policy. The objective of this study was to evaluate different sets of conception rates with an increasing level of accuracy to determine the insemination policy. An existing dynamic program for optimal insemination and replacement was used to compare three different scenarios in the estimation of conception rates, based on the reproductive performance of Dutch dairy cattle: (i) constant conception rate throughout lactation, (ii) conception rate dependent on parity and months in milk, and (iii) conception rate dependent on parity, months in milk and insemination number. The time step of the model was 30.4 days (1 month). The discounted future cash flow of culling a cow at each time step (replace a heifer immediately) was compared with keeping that cow under optimal future decisions. The difference between immediate culling and optimal decisions is defined as the retention pay-off. The insemination value was calculated as the difference between the future cash flow between immediate insemination of a cow and waiting one time-step. The results show that the difference in the insemination values and the optimal time to stop insemination depend on parity, lactation stage and the relative milk yield. In older cows with equal milk yields and at the same months in milk, the insemination value was lower than in younger cows. Within a parity, the insemination value was higher for cows with a higher milk yield. On individual cow level, using more accurate conception rate as input in the optimal insemination and replacement model might reduce miscalculation of the economic consequences for at least of €20-€38 per cow per year. Basing insemination decisions on less accurate input of the probabilities of conception, however, did not have an economic consequence at the herd level. In conclusion, using the appropriate conception rate as input in the optimal insemination and replacement model would increase the precise decision for the optimal time to stop insemination and hence improve the reproductive management efficacy.     

Assessment of the reproductive system of the male ruminant.

Physical examination requires very little equipment or expense and is an effective means of obtaining valuable information concerning fertility. Thorough evaluation of the reproductive system provides important information often unattainable by any other means. Disease processes, congenital abnormalities, injuries, management errors, and many other factors can be identified. No segment of the examination should be overlooked, as each part is important. The time invested in evaluating the male reproductive system is rewarded with a more complete and accurate assessment of the breeding male.     

Longitudinal observation on reproductive and lactation performances of smallholder crossbred dairy cattle in Fitche,Oromia region,central Ethiopia

A two-year longitudinal study was conducted to assess the reproductive and lactation performances of smallholder crossbred dairy cattle in Fitche, central Ethiopia. Twenty-four smallholder dairy farms were monitored and data on reproductive, breeding, lactation and management aspects of crossbred dairy cows (n = 69) were collected and analysed. Moreover, milk samples were collected and analysed for progesterone. The overall Least-squares means for calving interval (CI), calving to conception interval (CCI) and first observed oestrus after calving were 516, 253 and 141 days, respectively. Suckling significantly prolonged these intervals. The mean first onset of luteal activity (OLA) after calving was 52 days, while 67.4% (n = 43) had a delayed (>55 days) return to cyclicity after calving. Suckling and parity number significantly (p < 0.05) influenced the OLA. The mean lactation length was 54.4 weeks. The overall daily mean milk yield for the first 43 weeks of lactation after calving was 11.7 L/day. The estimated daily milk yield increased slowly and reached peak (13.8 L/day) around the 11th week post partum and declined gradually and steadily. Suckling status, season of calving and parity number significantly influenced the estimated daily milk yield. In conclusion, the present study indicated that the smallholder crossbred dairy cows in the study area had prolonged intervals to first oestrus after calving, to conception and to the next calving, and thus their reproductive performance is unsatisfactory. Delayed first onset of luteal activity (postpartum anoestrus) contributed to these extended intervals. Further detailed investigation is suggested to examine the effects of other relevant factors on the reproductive and lactation performances of smallholder crossbred dairy cows for appropriate intervention.     

Risk factors for metritis in Michigan dairy cattle using herd- and cow-based modelling approaches

A prospective study, using the Michigan portion of the National Animal Health Monitoring System, was conducted to determine disease and management factors that affect the incidence of metritis in Michigan dairy herds. A stratified random sample representing 1% of all Michigan dairy herds was observed. Data related to herd, feeding, and reproduction management, disease and environmental risk factors, and cow-based disease and reproductive data were collected monthly for a 12 month period. Cows with complete management records that were observed for at least 3 months postpartum were included in the study (85 herds, 5278 cows). A multivariate linear regression model was developed for lactational incidence of metritis by herd, and a multivariate random-effects logistic model was developed for the occurrence of metritis by cows. Significant factors associated with increased occurrence of metritis included larger herds, problem calvings, overconditioning, underconditioning, and more active reproductive management. Factors associated with reductions in metritis involved good nutritional management, and working relationships with veterinarians for disease management. Implications for the significance of these factors are discussed, with emphasis on differences in interpretation and use of results from herd and cow-based analyses.     

Risk factors associated with reproductive performance in small-scale dairy farms in Mexico

Several studies suggest that reproductive performance in small-scale dairy farms is low reducing the farms’ profitability. Therefore, identifying risk factors associated with low reproductive performance is a key step to implement an improved reproductive management program. Accordingly, the aim of the present study was to identify the main risk factors affecting the reproductive performance of cows in small-scale dairy farms. Ninety-six dairy farms were incorporated into this study, and data from 1263 lactations were collected with different events as potential risk factors. Logistic regression models were used to assess the association (odds ratio, OR) and impact (population attributable fraction, PAF) between the potential risk factors and the reproductive variables. The main risk factors associated with assisted calving were male calf and primiparous cows (OR?=?1.7, PAF?=?0.315 and OR?=?1.5, PAF?=?0.131, respectively), while for retained fetal membranes (RFM) were assisted calving and abortion (OR?=?4.5, PAF?=?0.440 and OR?=?8.1, PAF?=?0.239, respectively). The main risk factors for days to first service over 70 days in milk were low body condition score at calving (BCS?≤?2.5) and primiparous cows (OR?=?2.2, PAF?=?0.285 and OR?=?1.4; PAF?=?0.096, respectively), while for days open over 110 days in milk were low BCS at calving (BCS?≤?2.5) and primiparous cows (OR?=?1.7, PAF?=?0.213 and OR?=?1.4; PAF?=?0.096, respectively) The main risk factor for non-pregnant cows at first service was RFM (OR?=?1.7; PAF?=?0.059). In conclusion, assisted calving, male calf, BCS?≤?2.5 and RFM were the main risk factors associated with reduced reproductive performance in small-scale dairy farms in tropical and subtropical regions of Mexico.

     

An economic assessment of twin births in British dairy herds.

The effect of twinning on the subsequent health, production and reproductive performance of dairy cattle was studied by analysing the data derived from 19,755 calvings which occurred during three years on 37 farms. The data formed part of the database of a veterinary practice operating the DAISY dairy cow recording scheme for its dairy farmer clients. The average twinning rate was 2.5 per cent. For first calf heifers the rate was 0.9 per cent, and the rate increased with increasing parity to over 5 per cent for cows calving for their sixth and subsequent lactations. Although they produced more milk than their contemporaries, twin-bearing cows suffered an increased incidence of retained placenta and vulval discharges and their calving to conception interval was extended by 33 days. Furthermore, 35 per cent of these cows were culled compared with 21 per cent of their contemporaries. The benefit of having more calves for sale was reduced owing to 15 per cent of them being born dead. It is calculated that producing twins resulted in an average loss of income of 74 pounds/cow, a deficit of 15 per cent compared with cows having single calves.     

Disease, production and culling in Holstein-Friesian cows: IV. Effects of disease on production

The effects of common clinical and two subclinical disease conditions (mastitis and ketosis) on milk production and reproductive performance in Holstein-Friesian cows were investigated in a two and a half year study. The data used were from 1315 lactation records and results from tests performed on 6241 composite milk samples.

Path analyses were used to estimate the direct and indirect impact of disease on days to conception, milk production in a standard 305 day lactation and milk production per day. Indirect effects accounted for a large percentage of the total effect of some diseases on production. The path coefficients were quite sensitive to the units used to measure production, with deviation from the herd average being the preferable measure. These units controlled confounding due to herd level variables. Effects identified by the path analyses were substantially different from those determined on the basis of unconditional associations between diseases and production parameters.

Subclinical mastitis and the reproductive diseases (most of which were subclinical in nature) were found to have the greatest detrimental impact on milk production per day. Several disease conditions had a beneficial effect on milk production and this was attributed to the therapy provided to cows affected with these conditions. All conditions related to reproductive performance had a detrimental effect on days to conception.     

Reproduction performance and management of dairy cattle

Internationally, reproductive performance of dairy cattle is declining. Under the low production, pasture-based and seasonal calving system used in New Zealand, reproductive performance is also declining, but remains higher than for many other industries. The seasonal calving system requires a high level of reproductive performance to ensure a 365 day inter-calving interval. About 80% of cows are detected in oestrus and inseminated in the first 3 weeks of the seasonal breeding programme and have a conception rate of 55% to 65% to this first insemination. This results in approximately 75% and approximately 90% of cows being pregnant by 6 weeks and by the end of the breeding programme, respectively. However, reproductive performance is declining due to multiple factors including increasing herd size, reduced oestrus detection sensitivity and specificity, declining body condition score at calving and increased rate of body condition score loss postpartum. Continuing selection for increased milk production is also having negative effects on reproduction. The mechanisms by which high production and negative energy balance are reducing reproductive performance are becoming better understood. However, practical solutions for the problem are challenging for veterinarians and consultants, especially given the consumer preference for less interventions.     

The complex relationship between welfare and reproduction in cattle

Using reproduction parameters as indicators for cattle welfare has limitations and, at best, these parameters should only be viewed as indirect indicators of welfare. On a farm level, measures such as fertility rates emphasize biological performance of the herd but fail to consider the welfare of individual animals. Even on an individual level, the relationship between reproductive effectiveness and animal welfare is complex. Good reproductive performance does not automatically signify good welfare, as domestication and targeted breeding programmes have led to prioritization of high productive and reproductive performance in most modern farm animal species. In this review, we synthesize literature regarding cattle husbandry, reproduction, welfare and their multidimensional relationships. We argue that practices such as artificial insemination or the use of sexed semen may provide potential welfare advantages as these practices reduce the risk of disease transmission and injury or enable selection of specific beneficial traits. Furthermore, they may offer a solution to current practices jeopardizing welfare, such as the management of surplus bull calves in the dairy industry. Conversely, the animals’ ability to perform natural behaviours such as oestrous expression, an aspect arguably contributing to welfare, is often limited on commercial farms; this limitation is particularly evident in housing systems such as tie stalls where movement is restricted. Moreover, common management practices such as oestrus manipulation may lead to negative attitudes in citizens who often regard naturalness as important element of animal welfare.     

Reproductive performance measures among Thoroughbred mares in central Kentucky,during the 2004 mating season

Reason for performing study: To improve efficiency at the farm level, a better understanding of how farm management factors impact reproductive performance is important. Objective: To assess reproductive efficiency and effectiveness among Thoroughbred mares in central Kentucky. Methods: A cohort of 1011 mares on 13 farms in central Kentucky was followed during the 2004 mating and 2005 foaling season. Information on farm level practices was collected via interviews with farm managers. Reproductive records were collected for each mare mated to obtain information on mare characteristics. The influence of mare age and status (maiden, foaling, barren) on Days 15 and 40 post mating pregnancy rates, foaling rates and total effective length of the mating season were assessed. The influence of stallion book size on reproductive performance measures was also examined. Results: Per season pregnancy rates on Days 15 and 40 post mating and live foal rate were 92.1, 89.3 and 78.3%, respectively. Per cycle rates for the same time periods were 64.0, 58.3 and 50.8%. There were no significant associations between stallion book size and reproductive performance outcomes. The mean s.d. interval from the beginning of the mating season to the last mating of the mare was 36.5 ± 26.1 days. Conclusions: Mare age had a significant impact on efficiency of becoming pregnant, maintaining pregnancy and producing a live foal. Overall, fertility did not decrease among stallions with the largest book sizes. Total interval length of the mating season can be reduced if managers ensure maiden and barren mares are mated at the beginning of the season and foaling mares are mated at the earliest oestrus after acceptable uterine involution has been achieved. Potential relevance: Measures identified in the study can be used by owners, farm managers and veterinarians to improve mare reproductive performance and identify parameters to assist with the implementation of effective culling practices.     

Possible causes and treatment strategies for the estrus and ovulation disorders in dairy cows

The reproductive performance of dairy cows has declined, along with an increase in their milk yield. First-service conception rates in lactating dairy cows are often lower than 50%. The precise detection of estrus is an important factor in the reproductive management of dairy cows for successful fertilization and pregnancy. However, estrus expression has been decreasing in modern dairy cows, affecting the detection rate of estrus. In addition to estrus, a high incidence of ovulation disorders affects the fertility of dairy cows. To address these problems, it is necessary to understand the changes in the endocrine functions that underlie estrus and ovulation disorders, and to develop effective treatment strategies. Recent studies have revealed that neurokinin B and neurokinin 3 receptor signaling play important roles in the regulation of the secretion of gonadotropin-releasing and luteinizing hormones, suggesting a potential clinical avenue for the stimulation of gonadal function. In this review, I have discussed the problems in estrus and ovulation disorders in modern dairy cows as well as the possible applications of neurokinin 3 receptor agonists in the treatment of these disorders.     

A case study of improving milking cow performance and milking system performance with using a flow simulator

Efforts to improve dairy performance have been focused on increasing milk productivity of cows through improved feeding systems and genetic potential. However, methods for evaluating milking system performance based on milk productivity have not yet been established. Milking system performance was evaluated by measuring the claw vacuum at five flow rates (1.9–8.7 kg/min) produced using a flow simulator for a single eight‐swing milking parlor with a high‐line system. Based on these results, a double eight‐parallel milking parlor with a low‐line system was installed and tested. Farmers can take data obtained from evaluations of milking system performance into account for future management decisions, such as renewing the milking system. By renewing the milking system, average milking productivity, somatic cell linear score (LS) of bulk milk, and LS of each cow were significantly improved in the year after installing the new system (p < .01). In addition to checking conventional milking systems, this novel diagnostic method using a flow simulator can be used for checking new installations and also for proposing renovations.