Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001
Performing Department
Stephenville-TAMU Agr Res Cntr
Non Technical Summary
Reproductive performance of lactating dairy cows has declined steeply in the past 50 years and that has been accompanied by a steady increase in average milk yield (Lucy, 2001). According to the NAHMS (2007), reproduction failure became the first cause of removal from dairy herds, representing 26.3% of all cows removed, followed by mastitis, which represented 23.0% of all cows removed (NAHMS 2007). To exemplify the cost associated with reproductive inefficiency in the TX dairy herd we will use the US annual average pregnancy rate (proportion of cows that become pregnant within a 21 d period) of 16% and the annual average pregnancy loss of 4.5% (NAHMS 2007). Considering that in TX there are 455,000 lactating dairy cows, an increase in pregnancy rate from 16 to 20% would represent additional 22,858 pregnancies per year and approximately $6,354,524, if the average value of a new pregnancy is $278 (DeVries et al., 2006). Further, if pregnancy loss was reduced from 4.5% to 2.5%, this would represent 9,919 fewer pregnancies lost every year and savings of approximately $5,505,045, if the average cost of a lost pregnancy is $555 (DeVries et al., 2006). One of the greatest limitations to reproductive efficiency across mammalian species is embryonic mortality, estimated to be 25% to 60%. In particular, early pregnancy loss is now estimated at 45% or greater in dairy cattle with the majority of embryonic losses occurring between Days 8 and 16 of pregnancy. To further exemplify the already critically low national dairy cattle pregnancy rate average of 16%, heat stress is responsible for further declines in pregnancy rates of dairy cattle during hot months throughout most of the United States. Problems of heat stress are growing in importance because continual improvements in milk yield per cow increase cow susceptibility to heat stress and because anticipated global climate change will increase the severity of heat stress. Despite its negative and growing impact on dairy farm profitability, there are few effective strategies for reducing the effects of heat stress on reproduction and milk production. The major strategy, providing elaborate housing involving shade, sprinklers, fans, etc., is capital-intensive, of limited effectiveness, and is not often feasible for small and medium-sized dairies with limited opportunity for capital investment as well as for alternative production systems such as grazing dairies. There is thus a compelling need to develop alternative approaches for reducing the summer decline in fertility. Novel strategies that offer the potential for improving dairy cattle fertility and milk production are those that are based on physiological, nutritional, and genetic manipulation of the lactating cow and for potential management strategies to modify the environment to improve overall cow comfort.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Objectives The following objectives outline an overarching research framework in which laboratory and field experiments will be planned to address interrelated key questions. In the context of understanding dairy cattle fertility and improved milk production, research activities will address the following objectives: The specific objectives are as follows: 1) Evaluate novel approaches with embryo transfer and manipulation, hormonal therapy or nutritional additives to improve fertility and milk production during summer. 2) Evaluate the efficacy of using different mechanical and (or) geothermal approaches to improve cow comfort and reduce the negative effects of heat stress. 3) Engage in technology transfer regarding novel approaches for improving fertility to dairy farmers and dairy farm personnel in English and Spanish using DAIReXNET and extension road shows. 4) Assess changes in producer behavior and seasonality of animal performance over time in response to the research and extension program using producer focus groups and data collected from individual dairies and DHIA. 5) Identify dairy heifers with superior uterine capacity and identify gene markers to allow for selection of superior uterine capacity in dairy cattle.
Project Methods
Objective 1: Using in vitro production procedures and slaughterhouse ovaries, embryos can be produced inexpensively. Timed embryo transfer allows effects of heat stress on estrus detection to be bypassed. Utilizing two commercial dairies in Central Texas, embryo transfer will be utilized versus conventional AI during summer to improve pregnancy rates. In addition, in vitro culture conditions of the embryo in an in vitro fertilization system will be modified with the addition of niacin to evaluate the effects of niacin to reduce the effects of heat stress on early growing embryos. An encapsulated niacin will be supplemented to dairy cattle to evaluate the effects of niacin on mitigating heat stress in dairy cattle. The supplementation will occur both in vivo and in vitro in order to improve both milk production and reproduction. Objective 2: Emerging technologies such as the use of heat exchangers under cow beds will improve the dissipation of stored heat within the dairy cow through conduction. Geothermal cooling technologies will be installed in a free stall barn and compared against no geothermal cooling to evaluate the cooling area in which a cow rests will reduce stored heat within the animal thereby improving production variables. Another technology to be evaluated will be the use of "Flip Fans" which calculate temperature, humidity and wind speed in order to adjust the time at which the fans come on, how much water is expelled through the misting system and to what angles the fans are placed in relation to the cows. Objective 3 and 4: Extension will play a key role in transferring science based information into understandable and applicable strategies to improve infertility. Results of past research and new experiments conducted as part of this project will be utilized to inform producers of management practices that can increase fertility in a way that maximizes profitability. Methods such as conferences, national and local websites, and producer assessments will be utilized to extend information. Objective 5: Three cooperating dairy herds with exceptional record keeping will be identified in Texas. The herd records will be used to identify and collect a blood sample from highly fertile or subfertile dairy heifers (n = 200 heifers per group for a total of 400 heifers) based on pregnancy outcome after artificial insemination (AI) during normal periods of weather, e.g. Fall and Winter as opposed to Summer. In order to be considered for this study, heifers must have a normal reproductive tract, no record of diseases in the months preceding the first artificial insemination (AI) and must be at post-pubertal age at the time of the first AI. The first AI will begin between 13 - 14 months of age on all heifers. Heifers will be detected in estrus and AI by the farms normal standard operating procedures which will be similar between farms. Highly fertile heifers will be defined as individuals that became pregnant to the first AI. Subfertile heifers will be defined as individuals that became pregnant only after the third AI which is also known as repeat breeder syndrome.