Hoard’s Dairyman
DAIRY CATTLE
FERTILITY DAIRY CATTLE FERTIITY
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DAIRY CATTLE
FERTILITY
© 2020 Copyright by W.D. Hoard & Sons Company All rights reserved. No part of this book may be reproduced or used in any form or by any means, electronic or mechanical, including photocopying, recording or by an information or storage retrieval system, without permission in writing from the publisher. Address inquiries to: W.D. Hoard & Sons Company Book Department P.O. Box 801 Fort Atkinson, WI 53538-0801 USA www.hoards.com Tel: 920-563-5551 Printed in the United States of America ISBN: 978-0-9960753-3-6 Library of Congress Control Number: 2020903580 Book design and layout by: Todd Garrett Art Director Hoard’s Dairyman Katelyn Allen Publications Editor Hoard’s Dairyman Book editing and proofing by: Corey Geiger Managing Editor Hoard’s Dairyman
Kelly Wood Editorial Assistant Hoard’s Dairyman
Aisha Liebenow Special Publications Manager Hoard’s Dairyman
Jeffrey S. Stevenson Dept. of Animal Sciences & Industry Kansas State University
CONTENTS
Chapter 1: Economic losses from reproductive inefficiency . . . . . . . . . . . . . . . . . . .7 Michael Overton, D.V.M., M.P.V.M., Elanco Animal Health
Chapter 2: The bull’s reproductive role . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Bo Harstine, Ph.D., Select Sires, Inc.
Chapter 3: The cow’s reproductive role . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 K. June Mullins, M.S., Virginia Tech
Chapter 4: Control of reproductive processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Jack H. Britt, Ph.D., North Carolina State University
Chapter 5: The sperm meets the egg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 Rocio Melissa Rivera, Ph.D., University of Missouri
Chapter 6: Genetics of fertility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 Chad Dechow, Ph.D., The Pennsylvania State University
Chapter 7: Diseases of reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Jocelyn Dubuc, D.V.M., D.V.Sc., University of Montreal
Chapter 8: Gestation and calf development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 Eduardo de Souza Ribeiro, Ph.D., University of Guelph
Chapter 9: Calving time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 Gustavo M. Schuenemann, D.V.M., M.S., Ph.D., The Ohio State University
Chapter 10: Health of fresh cows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65 Stephen LeBlanc, D.V.M., D.V.Sc., University of Guelph
Chapter 11: The first insemination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69 J. O. Giordano, D.V.M., M.S., Ph.D., Cornell University; and M. L. Stangaferro, D.V.M., M.S., Ph.D., Cornell University
Dairy Cattle Fertility • 3
CONTENTS
Chapter 12: Breeding your own cows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Joseph C. Dalton, Ph.D., University of Idaho
Chapter 13: Fertility programs for lactating dairy cows . . . . . . . . . . . . . . . . . . . . . . . 77 Richard Pursley, M.S. Ph.D., Michigan State University
Chapter 14: Breeding heifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Ricardo C. Chebel, D.V.M., M.P.V.M., University of Florida
Chapter 15: Methods for pregnancy diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Paul M. Fricke, Ph.D., University of Wisconsin-Madison
Chapter 16: Reproductive technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Ronaldo L. A. Cerri, D.V.M., Ph.D., University of British Columbia; and Jeffrey S. Stevenson, M.S., Ph.D., Kansas State University
Chapter 17: Troubleshooting your reproductive program . . . . . . . . . . . . . . . . . . . . . 103 Luís G. D. Mendonça, D.V.M., M.S., Kansas State University
Chapter 18: Using bulls on the farm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Fabio Lima, D.V.M., Ph.D., University of California-Davis
Chapter 19: Feeding for improved fertility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Felipe C. Cardoso, D.V.M., M.S., Ph.D., University of Illinois
4 • Dairy Cattle Fertility
FOREWORD
R
eproduction is a central part of every dairy herd from both an economic and a management perspective. Perhaps even more than any other aspect of the dairy industry, reproductive management has seen tremendous growth scientifically and technologically in recent decades. Dairy producers have a wide array of decisions to make and tools to utilize when creating valuable pregnancies for the future of their herd. It is with these needs in mind that we are pleased to present this updated edition of Dairy Cattle Fertility. Previous versions of the book have featured contributions from a number of talented specialists, making this an important title in the Hoard’s Dairyman bookstore for over 50 years. The first edition, authored by Harold D. Hafs and Louis J. Boyd, was released in 1964. A 1996 revision was organized by Ray L. Nebel, assistant professor of reproductive physiology and reproductive management extension specialist at Virginia Tech, who went on to become a reproduction solution specialist with Select Sires. Jeffrey S. Stevenson, professor of reproductive physiology at Kansas State University, and W. S. Swecker, D.V.M., of the Virginia-Maryland College of Veterinary Medicine, assisted Nebel with that edition. Hoard’s Dairyman first partnered with the Dairy Cattle Reproduction Council (DCRC) on a 2007 update of the book, an effort led by Nebel as well as Ellen Jordan, a professor and dairy extension specialist at Texas A&M University. We are grateful for DCRC’s continued support in the edition here. This current book would not be possible without the expertise of Jeffrey S. Stevenson, who seamlessly coordinated the industry-leading authors you will meet in the following pages. We trust that all readers will find this latest edition of Dairy Cattle Fertility to be useful and insightful in an ever-changing dairy world. -Hoard’s Dairyman
Dairy Cattle Fertility • 5
CHAPTER 1
Economic losses from reproductive inefficiency D
airy production systems depend on timely production of a pregnancy that leads to calving and the initiation of lactation. Dairy producers place a high priority on achieving high reproductive performance and in terms of metrics that are closely followed. The herd’s reproductive performance is probably the second-highest priority metric next to how much milk cows are producing. For most dairy veterinarians, reproductive herd visits have been the cornerstone of their business for many years. Good reproductive efficiency is truly one of the keys to a more profitable dairy. Virtually any dairy producer can tell you about one of their favorite cows that had to be culled because of “infertility.” Loss of a valuable cow to reproductive failure is a costly problem for many reasons. However, many cows that are culled because of failure to become pregnant are likely not truly sterile; they simply ran out of service opportunities. Consider the following hypothetical example. A population of 200 cows known to be fertile is exposed to a reproductive management program that “magically” results in a conception risk of 50 percent (for example, services per conception of 2.0), service after service. After four services, 12 animals will still be open and 188 will be pregnant. In this example, the 12 that are still not pregnant will be culled as open, infertile cows, but if they were provided with one more service opportunity, assuming the same conception risk as before, six more would get pregnant, leaving six as “infertile.” In reality, achieving 50 percent conception risk for every insemination does not occur. Rather, the probability of conception given an insemination will vary based on many factors including cow health, semen quality, timing of insemination, semen placement, and many additional factors including the proportion of the population at risk that is truly sterile. Sterility, however, is usually a very small contributor to reduced fertility at the herd level. A heifer or cow would be considered sterile if it was biologically impossible for
her to conceive. A freemartin heifer with incomplete development of her reproductive tract and a cow that had experienced a severe infection of her reproductive tract that leads to an inability to deliver an egg from the ovary to the uterus are two examples of truly sterile animals. While dairy heifers usually have greater fertility than lactating cows, the incidence of true sterility, however, is likely greater in heifers than in cows because of freemartinism. Lactating cows have already calved at least once, and thus any sterility issues in cows are the result of trauma at calving or postcalving infection. In both cases, economic losses occur, but culling is just one part of the total losses.
Cost of infertility Regardless of the cause of infertility, the impact on the dairy is significant. Before discussing the losses associated with poor reproductive performance, perhaps it is useful to define good performance and to use this definition as the basis for explaining the sources of economic loss. Good reproductive efficiency may be defined as the creation and maintenance of pregnancy in an efficient and timely manner at the stage of lactation that optimizes profitability. Good reproductive management, coupled with good young stock management and proper culling decisions, yields a more-than-sufficient supply of replacements (assuming that conventional dairy sires are used). This allows the herd to achieve and maintain an efficient stage of lactation (range of days in milk, or DIM, for cows) to produce high levels of milk, reduces the risk of producing fat cows, and supports more rapid genetic progress. High reproductive performance also allows greater overall management flexibility in areas such as culling decisions, sire selection (selection emphasis on certain traits, sex-sorted semen, or strategic use of beef semen), and selection of the voluntary waiting period (VWP). Note that good reproductive efficiency is not simply getting cows
Chapter 1 • 7
10 • Chapter 1
attention, she is very likely to stay in the herd, even though it is likely a bad economic decision and a lost opportunity to replace her with a better heifer. In contrast, if this lower value cow aborts, she will be culled, resulting in a more positive economic decision for the dairy in that she will be replaced with another heifer that represents a significant predicted upgrade in value for that slot in the dairy.
Reproductive success and profitability The relationship between reproductive performance and herd profitability depends on many variables including, but not limited to, the following: milk price, replacement heifer cost, market (cull) cow value, calf value, culling timing, breeding window, insemination risk, conception risk, semen cost, and rate of genetic gain. The value of reproductive change is most commonly evaluated by comparing two programs under a set of economic conditions. Profit from reproductive program change is described as the difference between revenues and costs. For example, when comparing Program A (with a 21-day PR of 18 percent) to Program B (with a 21-day PR of 23 percent) and the same VWP, the greater reproductive performance in Program B is predicted to result in more milk produced per cow per day as a result of a shift in the DIM for a typical cow in this scenario.
Milk is far and away the largest source of revenue resulting from improving reproductive performance, but two other sources of revenue are calf income and market (cull) cow income. Assuming that the baseline culling risk in the herd stays the same, however, market cow revenue could be positive or negative, depending on the timing of culling decisions (market cow weight and value). Initially after improving reproductive performance, fewer cows may be culled, but over time, with a greater culling risk because of increased replacement heifer pressure, market cow revenue may increase. In terms of costs, numerous variables should be considered. When reproductive performance improves and milk per cow climbs, marginal feed for lactating cows will go up. With a more rapid turning of the calving cycle, cows will spend proportionately more of their lifetime in the dry period, thus, there can be greater transition cow costs and fresh cow expenditures. Replacement cost also will vary and move directionally opposite to the market cow revenue already discussed. Breeding and labor costs may climb or fall, depending on whether the improved performance occurred because of more insemination intensity only, an improvement in conception risk, or both. In addition, there is often an additional investment cost associated with improving reproductive performance aside from the normal daily management costs such as the
Figure 2. Predicted economic returns from increasing 21-day PR $450
Economic Value ($)
improved reproduction in the lactating herd, and these heifers survive to calve themselves, then greater pressure is created in the replacement pipeline. Then, in the absence of selling heifers or herd expansion, culling risk in the adult herd must increase. Another point to mention regarding the topic of reproductive efficiency is pregnancy loss. Very early embryonic loss (loss of a pregnancy between conception and about 17 days of gestation), late embryonic loss (the loss of a pregnancy between approximately 17 and 42 days of gestation), and abortion (loss of a pregnancy between 42 and 260 days of gestation) are all forms of pregnancy loss. The true economic impact of embryonic loss, especially early embryonic losses, are very difficult to estimate because most of them go undetected or are observed as lower-than-expected conception risk. Abortion, on the other hand, results in a much more significant economic impact because most cows that abort are further along in their gestation and lactation and are likely to be culled as open cows. Costs of abortion vary based upon the value of the cow, the potential value of the conceptus, and the timing of the abortion. If we consider the case of a commercial herd using conventional, average service sires, the predicted values of abortion are now more a function of the lost value of the cow that results from being culled as an open cow, depending on when in lactation the abortion occurred and at what stage of gestation. If abortion occurs at 45 days of gestation in a cow that was inseminated at 80 DIM, she still has an opportunity to become pregnant again. In contrast, if abortion occurs at 200 days of gestation, she will be culled. Under current economic conditions and above average reproductive performance, abortion losses may average about $1,000 to $1,400, but the range could be from about $1,000 to more than $5,000. You may be wondering, “How can an abortion have a negative cost?� As discussed previously, not all cows have sufficient economic value to deserve to stay in the herd long enough to produce a calf. If one of these cows with a very negative economic value becomes pregnant because of management in-
$400 $350 $300 $250 $200 $150 $100 $50 $0 10% 12% 14% 16% 18% 20% 20% 22% 24% 26% 28% 30% 32%
21-day PR $14.00
$16.00
$18.00
$20.00
$32.00
Across a range of milk prices indicated by each colored line, further improving 21-day PR will provide diminishing economic returns.
Table 2. Predicted profit from increasing 21-day PR
21- day pregnancy risk
Milk price, $/cwt $14
$16
$18
$20
$22
10%
Referent
Referent
Referent
Referent
Referent
12%
$68.20
$80.32
$92.43
$104.55
$116.67
14%
$50.45
$59.53
$68.61
$77.69
$86.77
16%
$36.10
$42.72
$49.35
$55.97
$62.59
18%
$27.46
$32.61
$37.77
$42.92
$48.07
20%
$17.81
$21.26
$24.71
$28.15
$31.60
22%
$12.01
$14.48
$16.95
$19.42
$21.89
24%
$7.18
$8.77
$10.36
$11.96
$13.55
thing, but there is also risk involved with making changes. For a herd that is already at 28 percent PR and receiving $18 per cwt. for milk, the value of improving to 30 percent PR is less than $4 per cow per year, but the loss to be realized if a management change actually causes PR to drop from 28 percent to 26 percent is more than $8 per cow per year. So, the goal should be to increase the herd’s reproductive performance, but once the herd achieves a high PR, perhaps the focus should be on reducing the risk of falling back rather than striving for even higher levels.
26%
$5.97
$7.27
$8.57
$9.86
$11.16
28%
$3.96
$4.84
$5.71
$6.59
$7.46
30%
$2.55
$3.16
$3.77
$4.38
$4.99
Value of days open
32%
$1.68
$2.07
$2.46
$2.85
$3.24
The concept of using days open as a way of comparing and evaluating reproductive performance sounds logical and appealing, but on closer consideration, many issues become apparent. Many consultants like to use estimates for the cost of “an extra day open” in evaluating different potential reproductive programs, but this presents big challenges. First, similar to the preceding work on the value of improving 21day PR, the cost per day open has a curvilinear shape with increasing cost per day as the days open increase. Assuming that the optimal days open for a herd is 110, extra days open of 112 or 115 may be less than 50 cents per day in loss, but days open more than 200 can easily range from $2.50 to $5 per day, depending on the value of milk and other key economic inputs. Second, days open is a very biased metric; it indicates how long it took the pregnant cows to become pregnant but indicates nothing about the cows that have not yet, or never will, become pregnant. Days open has been used here for explanation and illustration purposes but should never be used as the metric for measuring and monitoring herd-level reproductive performance.
At various milk prices, further increasing 21-day PR will provide diminishing profits.Univer-
sity
implementation of a timed A.I. program, installation and use of an activity system, or some other approach. A critical point to remember when considering the value of reproductive changes is that profit gains follow the law of diminishing returns. In other words, gains are greater when improvements are made from a very low starting point, but the exact value will vary depending on economic conditions. For example, the gain from improving reproductive performance from 16 to 18 percent PR is much larger than improving from 26 to 28 percent PR, assuming that VWP and all else are equal. Figure 2 and Table 2 both illustrate the diminishing returns associated with improving 21-day PR. In this example, the different curves represent the predicted value of change for varying milk prices, but in each case, the curvilinear shape persists. This example is for a herd producing 27,000 pounds (305-day mature equivalent basis) with $17 per cwt. milk, a 60-day VWP, a market cow value of 55 cents per cwt., lactating feed cost of 12 cents per pound of dry matter, dry cow
feed costs of $2.75 per day, newborn calf values of $200 for heifers and $50 for bulls, a replacement heifer cost of $1,800, labor cost of $15 per hour, a cost per A.I. service of $21, and an annual nonfeed transition management cost of $300, including the predicted cost of fresh cow disease. Table 2 shows that within a specific milk price range (single column of values), the profit associated with improving PR by 2 percentage points decreases in value as the starting level of reproductive performance increases. For example, at $16 milk, improving from 16 to 18 percent PR is associated with an increased profit of $32.61 per cow. However, the same two-point change from 26 percent to 28 percent is only worth $4.84 per cow. As the price of milk increases, the value of change increases, but follows the same pattern of diminishing returns. There is another important point to remember regarding the value of changing PR results. Producers and consultants alike are constantly striving to improve herd performance. Generally, this is a good
READ MORE ABOUT IT De Vries, A. 2006. Economic value of pregnancy in dairy cattle. J. Dairy Sci. 89:3876-3885. De Vries, A. 2007. Economics of the voluntary waiting period and value of a pregnancy. Pages 1-10 in Dairy Cattle Reprod. Counc. Conf. Proc., Denver, CO, Dairy Cattle Reprod. Counc., New Prague, MN. Overton, M., and V. Cabrera. 2017. Monitoring and quantifying value of change in reproductive performance. Pages 549-564 in Large Dairy Herd Management, 3rd ed. D. K. Beede, ed. American Dairy Science Association, Champaign, IL.
Chapter 1 • 11
CHAPTER 13
Fertility programs for lactating dairy cows Richard Pursley, M.S., Ph.D., Michigan State University
F
ertility of lactating dairy cows decreased significantly during the past 50 years. Fertility of heifers remained steady during that period. The modern, high-producing, lactating dairy cow may lack sufficient progesterone in circulation to maintain fertility levels similar to heifers. Fertility programs that systematically utilize GnRH and PGF for the first artificial insemination (A.I.) increase concentrations of progesterone and manipulate the age and size of ovulatory follicles in cows. These hormonal manipulations raise pregnancies per A.I. and reduce the chance for twinning. This chapter will describe a complete reproductive management program utilizing fertility programs for first A.I. and resynchronization programs for repeat services.
First A.I. fertility programs It is critical for dairy profit to initiate a reproduction program that controls time to first A.I. and enhances fertility of lactating dairy cows. Utilizing fertility programs allows for control of first A.I. in all cows at the most profitable stage of lactation (approximately 75 to 81 DIM). First A.I. fertility programs utilize ovsynch technology (Figure 1). It is important to induce ovulation after
the first GnRH treatment of ovsynch to maximize success of the program. Estrous cycles in cows must be presynchronized before ovsynch to ensure they are in a stage of the estrous cycle that enhances the probability of ovulation to GnRH. Presynchronization strategies aim to manipulate cycling cows to start ovsynch in most cows between Days 5 and 9 of the estrous cycle. There are currently three fertility programs that yield greater pregnancy rates compared with A.I. following a standing estrus: Presynch-11 (or 10), Double Ovsynch, and G6G (Figures 2A, 2B, and 2C, respectively). Cows that respond to the presynchronization injections of PGF and GnRH and the first GnRH
of ovsynch have significantly greater progesterone concentrations, greater control of the age of the ovulatory follicle, and a greater probability of a pregnancy. These cows also have fewer double ovulations and chances for twinning resulting from a greater exposure to progesterone during follicular wave development between the first GnRH and PGF treatments of ovsynch. Approximately 15 to 20 percent of cows do not have complete CL regression following the final PGF of ovsynch. This may limit the fertility potential of these programs despite the beneficial impact of greater pregnancy rates, especially in multiparous cows. It is clear that adding a second PGF eight to 24 hours follow-
Figure 1. Ovsynch program Sun
Mon
Tues
Wed
Thurs
PGF2α (am)
GnRH (pm)
A.I. (am)
Fri
Sat
GnRH
PGF2α (am)
56 hours
16 hours
A standard seven-day ovulation synchronization (ovsynch) program that uses gonadotropin-releasing hormone (GnRH) to induce ovulation and prostaglandin F2α (PGF) to cause the death of the corpus luteum (CL) before a fixed-time insemination.
Chapter 13 • 77
