The objective of this study was to estimate the value of pregnancy for dairy cows. Effects of the stage of gestation, stage of lactation, lactation number, milk yield, milk price, replacement heifer cost, probability of pregnancy, probability of involuntary culling, and breeding decisions were studied. A bioeconomic model was used, and breeding and replacement decisions were optimized. A general Holstein herd in the United States was modeled. The average value of a new pregnancy was $278. The value of a new pregnancy increased with days in milk early in lactation but typically decreased later in lactation. Relatively high-producing cows and first-lactation cows reached greater values, and their values peaked later in lactation. The average cost of a pregnancy loss (abortion) was $555. The cost of a pregnancy loss typically increased with gestation length. Sensitivity analyses showed that an increased probability of pregnancy, an increased persistency of milk yield, and a smaller replacement heifer cost greatly reduced the average value of a pregnancy. The value of a new pregnancy was negative for relatively high-producing first-lactation cows when persistency of lactation and the probability of pregnancy were increased. Breeding was delayed when the value of pregnancy was negative. Changes in milk price, absolute milk yield, and probability of involuntary culling had less effect on the value of pregnancy. The value of pregnancy and optimal breeding decisions for individual cows were greatly dependent on the predicted daily milk yield for the remaining period of lactation. An improved understanding of the value of pregnancy may support decision making in reproductive management when resources are limited.

The objective was to describe the dynamics of culling risk with disposal codes for Holstein dairy cows reported by herds enrolled in the Dairy Herd Improvement program. Dairy producers could report 1 of 9 possible disposal codes or forego reporting a code. After edits, 3,629,002 lactation records were available for cows calving between 2001 and 2006 in 2,054 herds located in 38 states primarily east of the Mississippi river. The distribution of culled cows by disposal code was estimated by parity, days after calving, pregnancy status, cow-relative 305-d mature equivalent milk yield, herd-relative 305-d mature equivalent milk yield, and season. Of all herds, 57% reported all 8 different disposal codes excluding the codes dairy purposes and reason not reported. Hazard (risk) functions were calculated by parity, from 1 to 520 d since calving for open cows and from 1 to 280 d since conception for pregnant cows. Annualized live culling rate and death rate (reported code was death) were 25.1 and 6.6%, respectively. The primary disposal code was died (20.6% of all culling), followed by reproduction (17.7%), injury/other (14.3%), and low production and mastitis (both 12.1%). The risk of culling with various disposal codes varied with stage of lactation. Died and reproduction were the most frequently reported codes for cows leaving the herd during early and late lactation, respectively. Early lactation was also a critical period for culling with the disposal codes injury/other and disease, and the risk increased with days after calving for the codes low production and reproduction. The risk of culling with the disposal code died showed the greatest seasonal pattern with increased risk of death in spring and summer. A negative association was found between annualized live culling and death rates within herds. Compared with open cows, pregnant cows had a lower risk of culling with all reported disposal codes. In addition, the risk of culling was lower in high-producing cows with all disposal codes. In conclusion, the risk for culling by disposal code varied by parity, stage of lactation, season, pregnancy status, and milk yield.

The objective of this study was to compare the economic outcome of reproductive programs using estrus detection (ED), timed artificial insemination (TAI), or a combination of both (TAI-ED) using a stochastic dynamic Monte-Carlo simulation model. Programs evaluated were (1) ED only; (2) TAI: Presynch-Ovsynch for first AI, and Ovsynch for resynchronization of open cows at 32 d after AI; (3) TAI-ED: Presynch-Ovsynch for first AI, but cows underwent ED and AI after first AI, and cows diagnosed open 32 d after AI were resynchronized using Ovsynch. Evaluated were the effect of ED rate (40 vs. 60%; ED40 or ED60), accuracy of estrus detection (85 vs. 95%), compliance with the timed AI protocol (85 vs. 95%), and milk price ($0.33 vs. 0.44/kg). Conception rate to first service was set at 33.9% and then decreased by 2.6% for every subsequent service. Abortion was set at 11.3%. Cows were not AI after 366 d in milk, and open cows were culled after 450 d in milk. Culled cows were immediately replaced. Herd size was maintained at 1,000 cows, and the model accounted for all incomes and costs. Simulation was performed until steady state was reached (3,000 d), and then average daily values for the subsequent 2,000 d were used to calculate profit/cow per year. Net daily value was calculated by subtracting the costs (replacement, feeding, breeding, and other costs) from the daily income (milk sales, cow sales, and calf sales). The ED40 models resulted in greater profits than the TAI-85 model but lower profits than the TAI-95 model. Both ED60 models resulted in greater profits than the TAI-95 model. Combining TAI and ED increased profits within each level of accuracy or compliance. Adding TAI to ED would increase overall profit/cow per year by $46.8 to $74.7 with 40% ED, and by $8.9 to $30.5 with 60% ED. Adding ED to TAI would increase profit/cow per year by $64.2 to $99.4 with 85% compliance and by $31.8 to $59.7 with 95% compliance. Although combining TAI and ED increased profits within each level of accuracy or compliance, when evaluated separately, ED60 with 95% accuracy or TAI with 95% compliance were as profitable as or more profitable than TAI-ED with low ED, accuracy, or compliance. Therefore, producers can improve their profits by combining TAI and ED as reproductive management; however, if a herd can achieve high ED with high accuracy or have high compliance with injections, using only ED or TAI might be more profitable than trying to do both.

Widespread commercial application of sexed semen is expected within the next decade because of continued improvements in fertility of sexed semen and sorting capacity. The objective of this study was to explore the potential impact of widespread application of sexed semen on the structure of the dairy industry in the United States. Historically, female offspring from all heifers and cows were needed to produce enough dairy replacement heifers to replace culled cows. The use of sexed semen allows for a decoupling of breeding decisions necessary to obtain an adequate supply of dairy replacement heifers from those needed to achieve pregnancies needed to start new lactations. Application of sexed semen allows dairy producers to select among their herds' potential dams and produce dairy replacement heifers from only the genetically superior animals. The rate of genetic progress is expected to increase, but not more than 15% of the rate of gain accomplished through sire selection achieved through conventional (nonsexed) artificial insemination breeding. The supply of dairy replacement heifers is expected to grow to meet and temporarily exceed current demand, resulting in reduced prices for dairy replacement heifers. Consequently, herd turnover rates are expected to increase slightly, and herd expansions may accelerate. The rate of consolidation of dairy farms is expected to increase. Widespread application of sexed semen may temporarily increase the supply of milk, which would result in lower milk prices. The cost of milk production will be reduced as well. Many breeding options exist for the genetically poorer cows in the herd. The optimal breeding mix depends on the value of the various kinds of calves that could be produced. More crossbred calves for beef production may be produced; however, a market for these crossbred calves is not well established. Increased specialization is expected with more dairy producers deciding not to raise their own heifers but to purchase replacements. Other dairy farms might specialize in producing genetically superior dairy replacement heifers for sale. Depending on the value of calves not raised for replacements, artificial insemination organizations might market beef conventional semen or beef male sexed semen to dairy farms. The use of sexed semen should lower the cost of progeny-testing programs and embryo transfer and enhance the value of genetic markers. Eventually, the economic benefits from the use of sexed semen will be passed on to consumers.

Lameness is a multifactorial condition with many causes. In this study, cow lifetime records were used to quantify the incidence of specific lameness-causing lesions and investigate factors associated with those lesions. Of primary interest were the effects of seasonality and the effects of thin soles (TS). Thin sole-induced toe ulcers (TSTU) occurring adjacent to the white line in the apical portion of the weight-bearing surface were distinguished from white line disease (WLD) occurring in the region of the abaxial heel sole junction. Sole (SU), heel (HU), and toe (TU) ulcers; TS; sole punctures (SP); leg injuries (INJ); and other (OTH) lesions (e.g., infectious diseases, laminitis, unclassified hemorrhage) were also considered. Data were collected from May 2004 through October 2007 and included records for 4,915 cows of which 1,861 had at least one recorded lameness event. Of these, 20% were TSTU, 20% OTH, 16% SU, 13% TS, 10% WLD, 8% HU, 6% INJ, 4% SP, and 2% TU. Annual incidence risk for lameness was 49.1%. Overall incidence rate for lameness was 1.41/1,000 cow-days, and rates for all lesions were highest in the summer. As parity increased, so did incidence rates for TS, SU, WLD, HU, and INJ. For TS, TSTU, and WLD, incidence rates were lowest in early lactation (16 to 60 DIM), whereas for SU, HU, TU, incidence rates were highest in mid lactation (61 to 150 DIM). Cox proportional hazard models for TS, TSTU, WLD, SU, HU, TU, and SP included age and year of first calving and milk production capacity. Prior/concurrent lameness events, season, parity, and stage of lactation were included as time-dependent effects. Prior/concurrent TS increased the hazard for all other lesions, particularly TSTU, and HU. Having any other prior claw lesion also increased the hazard for all lesions. Hazard was highest in summer for all lesions except TU. Stage of lactation was a significant effect in hazard of TSTU, which was lowest in mid lactation (61 to 150 DIM).

The average productive lifespan is approximately 3 to 4 years in countries with high-producing dairy cows. This is much shorter than the natural life expectancy of dairy cattle. Dairy farmers continue to cull cows primarily for reasons related to poor health, failure to conceive or conformation problems prior to culling. These reasons may indicate reduced welfare leading up to culling. Improvements in health care, housing and nutrition will reduce forced culling related to these welfare reasons. However, productive lifespan has remained similar in decades, despite large improvements in cow comfort and genetic selection for the ability to avoid culling. On the other hand, genetic progress for economically important traits is accelerating within the last decade, which should slightly shorten the average economically optimal productive lifespan. A major driver of productive lifespan is the availability of replacement heifers that force cows out when they calve. The average productive lifespan could be extended by reducing the supply of dairy heifers, which would also have benefits for environmental sustainability. Improvements in culling decision support tools would strengthen economically optimal replacement decisions. In conclusion, major factors of the relatively short productive lifespan of dairy cows are welfare-related, but other economic factors like supply of heifers, genetic progress and non-optimal decision-making also play important roles.

An optimal dairy cow culling and replacement model was developed; it included the option to delay entering heifers into the herd after cows were culled. The objective was to investigate whether leaving a slot temporarily vacant, to enter a heifer at a more favorable time of the year, could be economically advantageous when cow performance is seasonal. The goal of the optimization was therefore to maximize net return per slot per year. The model consisted of 3 modules: 1) a bioeconomic module to enter and calculate cow performance data and prices, 2) a replacement policy module based on dynamic programming to calculate optimal culling decisions for individual cows and when to enter heifers, and 3) a herd performance module based on Markov chains to calculate summary results for the herd. Results for the optimal culling policy under typical conditions in Florida showed that immediate replacement was economically advantageous throughout the year. However, for a nonoptimal culling policy, cows culled in May, June, and July would not be replaced by heifers until August. Realistic increases in seasonality or heifer prices, or lower milk prices, showed economic advantages of delayed over immediate replacement for both culling policies. The maximum advantage of delayed replacement of 486 price scenarios was 88 US dollars per slot per year; cows that left the herd in the early summer and spring were not replaced by heifers until the late summer. Delayed replacement was economically advantageous when fixed costs and net returns per slot were low and seasonality was high, which is the case for a portion of Florida dairy producers.

Genetic improvement in sires used for artificial insemination (AI) is increasing faster compared with a decade ago. The genetic merit of replacement heifers is also increasing faster and the genetic lag with older cows in the herd increases. This may trigger greater cow culling to capture this genetic improvement. On the other hand, lower culling rates are often viewed favorably because the costs and environmental effects of maintaining herd size are generally lower. Thus, there is an economic trade-off between genetic improvement and longevity in dairy cattle. The objective of this study was to investigate the principles, literature, and magnitude of these trade-offs. Data from the Council on Dairy Cattle Breeding show that the estimated breeding value of the trait productive life has increased for 50 yr but the actual time cows spend in the herd has not increased. The average annual herd cull rate remains at approximately 36% and cow longevity is approximately 59 mo. The annual increase in average estimated breeding value of the economic index lifetime net merit of Holstein sires is accelerating from $40/yr when the sire entered AI around 2002 to $171/yr for sires that entered AI around 2012. The expectation is therefore that heifers born in 2015 are approximately $50 more profitable per lactation than heifers born in 2014. Asset replacement theory shows that assets should be replaced sooner when the challenging asset is technically improved. Few studies have investigated the direct effects of genetic improvement on optimal cull rates. A 35-yr-old study found that the economically optimal cull rates were in the range of 25 to 27%, compared with the lowest possible involuntary cull rate of 20%. Only a small effect was observed of using the best surviving dams to generate the replacement heifer calves. Genetic improvement from sires had little effect on the optimal cull rate. Another study that optimized culling decisions for individual cows also showed that the effect of changes in genetic improvement of milk revenue minus feed cost on herd longevity was relatively small. Reduced involuntary cull rates improved profitability, but also increased optimal voluntary culling. Finally, an economically optimal culling model with prices from 2015 confirmed that optimal annual cull rates were insensitive to heifer prices and therefore insensitive to genetic improvement in heifers. In conclusion, genetic improvement is important but does not warrant short cow longevity. Economic cow longevity continues to depends more on cow depreciation than on accelerated genetic improvements in heifers. This is confirmed by old and new studies.