On the modern commercial dairy farm, maintaining consistent milk production every day of the year is key to sustaining consistent cash flow for the business.
However, doing so can be challenging since a cow’s milk production peaks early in her lactation and slowly diminishes during the months following. This means cows produce less revenue as the lactation progresses. So, for a dairy to maintain consistent milk production, cows in the herd must be evenly spaced at different stages of lactation with a certain percentage being fresh, a certain percentage being midlactation and a certain percentage being at the end of lactation and ready to dry off — in other words, a constant cycle of cows entering the herd, completing a lactation and drying off.
Dairy cows have a gestation period of about nine months. The modern dairy industry strives for herds to maintain a calving interval of 12 to 13 months for optimal lifetime milk production and revenue generation — meaning the cow freshens and produces large quantities of milk for 100 days or more before she conceives the next pregnancy, continuing with milk production until the seventh month of gestation at which time she’s dried off for the remaining two months before giving birth and starting the cycle all over again. The challenge faced by dairy farmers is getting cows bred in a timely fashion to not fall behind in the important calving interval.
Throughout the dairy industry, conception rates in dairy cows have been on the decline since the 1980s. Although on many dairy farms poor fertility is directly the result of poor heat detection and or poor insemination techniques, reduction in conception rates is increasingly blamed on the stress that comes with higher milk production along with a cow’s living environment — cow comfort and housing. More recently, research indicates that genetics may be playing a larger role in poor fertility as bulls are being selected and cows are being bred for milk production traits at the expense of fertility.
Most research on why conception rates are dropping has focused on a cow’s increased milk production with the belief that, as milk production increases, a cow experiences more biological stress that negatively impacts follicular development and strong estrous cycles. The stresses and strains of high milk production have put dairy cows in a precarious position. Anything such as metabolic disease, inadequate nutrition or poor housing will tip cows off balance, thus disrupting hormonal equilibrium, reducing estrus intensity and bulling activity.
One researcher wrote, “An essential question that must be addressed is whether or not modern dairy cows are inherently less fertile or if their infertility is simply a function of their level of milk production and nutrient partitioning. The current perspective is that infertility in modern high producing dairy cows is secondary to negative energy balance caused by high milk production during early lactation.”
It’s difficult to determine since there’s a paucity of research on whether the decline in fertility is a result of larger herd sizes and the inability of management to keep up with the work of getting cows bred on time. Other research contradicts the previous supposition, finding that large and small herds are experiencing declines in conception, suggesting that larger herd size is not the primary factor in declining fertility.
Clearly, there are two major concerns in the decline of pregnancy rates in dairy herds: (1) Failure to identify estrus correctly, which is primarily a management issue on dairy farms and (2) a biological reduction in fertility within dairy breeds possibly caused by genetic selection that focuses more on milk production as opposed to fertility — or cows are simply not as fertile as they once were. Although most dairy farmers would agree that pursuit of improved genetics and lifetime milk production for their cows is desirable, the process of getting their cows bred continues to be a challenge.
Dairy cows are able to conceive all year long, and they have an estrus cycle about every three weeks at which time they ovulate and release a number of eggs. Until the middle of the 20th century, cows were bred “naturally” with bulls as dairy farms were smaller in size, and genetic selection was not yet a major concern — cows just needed to get pregnant to remain productive. Dairy farmers made sure they had a couple of bulls on hand to get the job done and replaced them periodically to avoid too much in-breeding.
Since the 1950s, technologies have been developed for semen collection and storage and artificial insemination (AI) has become the method of choice for the vast majority of dairy farms today. In a very short period of time, the dairy industry has done away with bulls and “natural breeding.” Now with AI, the onus of getting cows bred falls squarely on the dairy farmer and the management team. This is where competent dairy management comes in. The failure of cows getting bred — meaning there’s no sperm to fertilize an egg when a cow ovulates — is at the heart of whether an AI program on a dairy is successful.
The dairy farmer’s job is to make sure the cow is inseminated in a timely manner before the eggs expire in the uterus. To be sure, monitoring estrus — also known as “watching for heats” — is labor intensive on all dairies. The larger the dairy, the more labor that must be devoted to making sure cows get bred. Cows that are missed cannot be bred again for three weeks. Reductions in reproduction efficiencies have resulted in lengthening of lactations and the allimportant calving interval which, as it increases, has a profound, negative impact on a dairy’s net income.
Fortunately for dairy farmers, cows have the homosexual trait of “bulling,” which is the prime indication that they’re cycling and soon to ovulate. In increasingly more cases, however, cows may have ovarian cysts causing them to engage in the bulling activity even when not ovulating. In other cases, cysts will cause a cow to remain silent. To prevent wasting semen or the excessive use of drugs on these cows, dairy farmers must incorporate an aggressive reproduction program in cooperation with their veterinarians to monitor ovarian health.
At the Fort Hill Dairy Farm in Thompson, Connecticut, Herdsman Spike Zajak noted that it’s continually becoming more difficult to get cows bred in his herd. The dairy has been milking about 200 cows for many years that average between 24,000 and 25,000 pounds of milk per cow. The average days to conception for the herd is just over 100 days and the average services per conception (SPC) is 2.7 — a number that has barely moved in many years. The average days-in-milk (DIM) seldom climbs above 170, however, which means there’s a consistently steady flow of fresh cows coming into the herd with very few cows ever seeing a lactation of more than 365 days.
Interestingly, in the days before recombinant bovine somatotropin (rBST) fell out of favor, attention to the SPC was much less of a concern since rBST was able to keep cows milking for many months whether pregnant or not. Many dairy farms allowed DIM in the herds to increase so long as the milk price and feed costs were favorable. Although this product aided the dairy farmer in keeping cows profitable for longer periods of time, it allowed them to start the slide down that slippery slope of sloppy breeding management.
Zajak noted that with the management tools available for improving reproduction on the dairy, including selection of sires based on genomics, the job doesn’t get any easier. While more than one-third of his herd conceives with one or two services, that still leaves twothirds of the herd requiring over three services for a conception.
Zajak’s heat detection protocol includes observation of cows bulling along with copious record-keeping and an aggressive timed AI program for cows that do not show heats. At Fort Hill every cow is considered a source of revenue and is expected to pay its way. Since discontinuing rBST, cows no longer have the luxury of milking two years while never getting bred back.
Zajak noted that various factors contribute to low fertility but agreed that it’s primarily stress that comes from high milk production that keeps cows from conceiving. He noted that it’s usually the highest producing cows in the herd that take longest to get bred back. The dairy has also been using bulls that are being selected based upon genomic traits as opposed to the traditional proven sires with many hundreds of daughters already milking. Zajak has data to back up the trend in his herd that many of those nonproven sires being used on his dairy have poorer conception rates than proven sires having a history of milk in the tank. Although he’s not openly criticizing the move toward trait selections via genomics, he’s watching the trends since the genomic semen is costing more money.
Many dairies have gone from visual detection of cow activity and estrus to marking tail heads with chalk or adhesive patches in an effort to better identify cows in heat — but it’s something that still has to be done daily. Timed synchronizing programs with the administration of hormones have become popular in herds in which heat detection is poor or for those cows that never seem to show a strong heat. In some herds conception is improved with timed AI, but research data still suggests that conception rates do not get much above 50 percent even when cows are synchronized. More recently, new technology has emerged: electronic activity monitors that record cows’ movements that are highly correlated to estrus.
One aspect of heat detection that’s well known is that cows are much more active during estrus as they go about bulling. The high correlation of increased activity and estrus can be monitored electronically via transponder and computer and a list of cows with increased activity outside the normal range can be generated daily for the dairy management team.
Dairyman Greg Peracchio, along with his father and uncle, milks about 260 cows at Hytone Dairy Farm in Coventry, Connecticut. Peracchio shared that heat detection has long been the single biggest challenge with breeding. Cows can come in heat any time of the night and day and the family simply didn’t have the manpower to effectively monitor for heats around the clock. Consequently heats were often missed or cows were being bred too late.
When activity monitors became available from the local DeLaval dealer, Peracchio decided to give some of them a try, initially installing them on some fresh cows and removing them after the cow was bred. The collar was reprogrammed and placed on another cow. That eventually proved to be more work than expected and he finally purchased them for all the cows, which now wear them full time.
According to Peracchio, breeding efficiencies with the activity monitoring system has dramatically improved. He’s using much less semen. After three years of using the technology, he has faith in the system and when the computer tells him that a cow has increased activity the previous day, Peracchio can be extremely confident that the cow is in heat. He just has to go into the pen, locate and breed her. Daily heat monitoring is nearly a thing of the past.
As is so often the case with dairy farms, management styles vary with size herd and availability of the workforce. What is certain: most dairy farmers will acknowledge that timely heat detection, getting cows bred and keeping the herd’s calving interval at an optimal level is a continual challenge and at times very frustrating. Everyone knows the drill — from the 9-year-old to the 90-year-old — keep an eye out for heats. Cows that don’t get bred won’t get pregnant. What’s critical, however, is that dairy farms closely monitor the breeding program, reacting and initiating solutions and programs, including use of new technologies that will improve breeding and avoiding long and unprofitable lactations.