This is a summary of activities conducted by the Dairy Science Department as part of an Extension-Research integrated proposal addressing two primary priorities:
1) Improving Fertility in Agricultural Animals
2) Preventing and Controlling On-Farm Disease
Our overall objective was to improve the reproductive efficiency of dairy cows using an interdisciplinary team approach to identify and remove barriers to reproductive success by linking outcomes of basic and applied research with an innovative farmer responsive extension program. These priorities were addressed through the five specific objectives of the proposal described below. The combination of internationally recognized, research-based state specialists, effective county-based extension agents, numerous and diverse commercial dairy farms, state-of-the-art laboratory and computational resources at the University of Wisconsin-Madison, and an established track record of effective, collaborative research and outreach activities within the Dairy Science Department made Wisconsin uniquely positioned to achieve these objectives.
This proposal was the top-rated proposal and was funded for a total of $1,000,000 over a 5-year period.
Objective 1 was to c
haracterize the contributions of specific management factors to the variation we observe between farms in dairy cow fertility. In the first study, we used 324,373 breeding records from 26 commercial farms to predict the outcome of an individual insemination event from information about the health, production and reproductive information for the corresponding herd, cow and service sire. We were able to predict the outcome (pregnant or non-pregnant) correctly 72.3% of the time in first lactation cows and 73.6% of the time in second and later lactation cows. Several early postpartum health disorders ranked among the top 10 factors affecting insemination outcomes, including incidence of mastitis, retained placenta, ketosis, lameness and displaced abomasum, indicating the critical importance of transition cow health with respect to reproductive success. In the second study, we carried out a cost-benefit analysis of alternative breeding strategies and tried to determine whether it would be cost effective to breed only the subset of eligible cows with high likelihood of conception, rather than the entire pool of eligible cows. We tested our model in three commercial herds with 3,197 cows that were eligible for breeding. Overall conception rate was 43% for these cows, but prior to breeding we were able to identify a subset of 1,886 “highly fertile” cows that subsequently had a 66% conception rate when inseminated. This led to a gain in profit of $16,656, or $5.21 per eligible cow. This approach can be extended easily to target highly fertile subsets of cows or heifers within the herd that would be good candidates for sexed semen or expensive semen from genetically elite sires.
Objective 2 of the proposal was to determine the impact of specific nutritional components on reproductive performance of lactating dairy cows. The nutrition-reproduction subprojects included: Farm survey (n=50) of dietary nutrient composition relationships with measures of reproductive performance; Farm records survey (n=648) of relationship between milk fat:protein ratio and pregnancy per AI first AI; Relationship between postpartum changes in body weight or body condition score and reproductive performance; Changing insulin through feed restriction or propylene glycol drench on reproductive performance; Feeding rumen-protected choline to transition cows and effects on reproductive performance; Feeding rumen-protected methionine and effects on reproductive performance. Results of two feeding trials with rumen-protected methionine were as follows: Methionine supplementation increased milk protein but did not alter embryo production or development; Methionine supplementation of the dam during early embryo development altered gene expression in the embryo; Methionine supplementation numerically increased pregnancy per AI by 5.8%-units in multiparous cows; Methionine supplementation reduced pregnancy loss in multiparous cows. Research on methionine supplementation effects on reproduction will continue.
Objective 3 of the proposal was to determine associations between occurrence and severity of clinical (CM) and subclinical mastitis (SM) during a defined breeding risk period (BRP, 3 d before to 32 d after artificial insemination) on pregnancies per artificial insemination (P/AI) at first service. Dairy cows (n = 3,144) from 4 Wisconsin herds were categorized based on the occurrence of 1 or more CM or SM events during and before the BRP: 1) Healthy, 2) Mastitis before BRP, 3) SM during BRP, 4) Chronic SM 5) CM during BRP, or 6) Chronic CM. Clinical mastitis cases were categorized based on etiology (Gram-negative, Gram-positive, and no growth) and severity (mild, moderate, or severe). Compared to healthy cows, the odds of pregnancy were 0.56, 0.67 and 0.75 for cows experiencing Chronic CM, CM or SM during the BRP, respectively. Thus, the occurrence of mastitis during the BRP decreased the likelihood that a cow would become pregnant after first service. The occurrence of chronic SM was not associated with reduced probability of P/AI at first service. Compared to healthy cows, the odds of pregnancy were 0.71 and 0.54 for cows experiencing mild or moderate-severe cases of CM during the BRP, respectively. The odds of pregnancy for cows experiencing CM caused by Gram-negative or Gram-positive bacteria during the BRP were 0.47 and 0.59, respectively. The occurrence of CM that resulted in no growth of bacteria in cultured milk samples was not associated with reductions in P/AI at first service. Regardless of etiology, microbiologically positive cases of CM with moderate or severe symptoms were associated with substantial reductions in P/AI1. We concluded from this study that etiology, severity and timing of CM were associated with decreases in the probability of pregnancy at first AI. Severity of the case was more important than etiology; however, regardless of etiology microbiologically negative cases were not associated with reduced probability of pregnancy.
Objective 4 was to evaluate the economic impact of reproductive management strategies on overall dairy farm economic sustainability under a variety of management scenarios. A series of simulation models were developed and used to calculate the impact of reproductive efficiency. A first model indicated, in general, for a commercial herd in Wisconsin, that 100% timed artificial insemination (TAI) programs were superior to 100% estrus detection (ED) programs and that adding ED to the 100% TAI programs was only beneficial if the ED conception rate (CR) was comparable or better than the one of the TAI CR. Another model that evaluated the economic value of individual cows demonstrated that there is a large economic opportunity of performing individual cow reproductive management in addition to herd-level protocols. A follow-up study included the development of a large daily Markov chain model to perform economic analysis of reproductive programs with a level of detail like never before. This model was used to quantify the economic value of improving the 21-d pregnancy rate (PR) and evaluate a series of specific commonly used reproductive programs that included the combination of TAI with ED. Moreover, this model has become a user-friendly decision support tool that is heavily used for industry consultants and dairy farmers alike to assess the economic value of reproductive management changes. The tool is openly available at the University of Wisconsin Dairy Management Website (DairyMGT.info: Tools: Reproduction). Further, the concept of whole herd value was introduced as the weighted average of individual cow values according to herd’s reproductive performance, which indicated a strong interaction between reproductive program’s efficiency and milk productivity supporting the notion that reproductive programs should be designed according to herd and individual cow productivity. Later, using adjustments of models previously developed, the economics of using blood chemical earlier pregnancy tests were studied. Results indicated that the major advantage of earlier chemical pregnancy diagnosis tests lies in the fact that these can substantially decrease the interbreeding interval between inseminations, which has large economic impacts that could outweigh the possible extra costs and inaccuracies of the earlier tests. In general, it was found that blood chemical tests would be worthwhile if their sensitivity are greater than or equal to 95%, their specificity are greater than or equal to 93%, and the herd’s earlier pregnancy loss (<40 d pregnancy) is lower than 9%.
Objective 5 is the extension aim of this proposal which we entitled Repro Money. Repro Money is an extension program offered to Wisconsin dairy farmers that wanted to improve reproductive performance of their dairy herd. This farmer-directed team-based approach consisted of 4 meetings during a 6 to 8 month period. The goal was to help dairy farmers best utilize their personnel and advisers in a coordinated way to improve reproductive performance and profitability. Data from all farms that enrolled and completed the program (n = 13) between Fall 2010 and Summer 2012 were included in this analysis. These farms averaged 385 cows (range = 67 to 850) with a rolling herd average of 12,524 kg/cow per year (range = 21,350 to 32,000 kg). Financial and management data were obtained with the aid of a guided situation assessment, action plan, and goal setting tool. Data were analyzed before and after participating in the program to evaluate the program’s impact on enhancing reproductive performance and herd profitability. After finishing the program, number of days in milk decreased 6 d (0 to 43), insemination risk increased 3% (53% to 56%), conception risk increased 3% (38% to 41%), and the 21-day pregnancy rate increased 3% (19 to 22%) among these herds. These improvements were estimated to yield an average economic gain of $55/cow per year with a total economic gain of $177,185/yr for the participating farms. This amount is expected to increase due to future additional improvements and management changes to be implemented using the program principles because 70% of participating farms decided to continue with regular meetings after finishing the program. All 13 farms that finished the program were highly satisfied with the outcomes with 85% of farms achieving the goals set, which included increasing the 21 d pregnancy rate, increase conception risk, and decreasing days to first AI. The 3 most important management changes that resulted from participating in the Repro Money Program were to perform better recordkeeping, focus on transition cow management, and improve use of synchronized breeding protocols.