Is there an Ideal Calving Interval (C.I.)?

Tuesday, August 23rd, 2016

A month ago I was challenged by my Facebook friend, Ian Crosbie, a keen dairy person from Benbie Holsteins, Saskatchewan Canada, with the question “Is there or should there be an ideal calving interval?”.

Well, I must admit that on first thought I would have quickly replied to Ian saying “Of course it is 12-13 months just like we have all been taught in agricultural school.”

But on second thought I question if there should be such a universal statement.

As it is beyond me to have the complete answer to the question I will bring forward some thoughts on the subject so breeders themselves can determine what calving interval best suits their dairy farming situation.

What Got Us to Wanting a 12-13 Month Calving Interval

Although not an all-inclusive list, here some factors that initially lead to 12-13 months being the recommended answer:

Milk cows were originally dual purpose cows, so they needed to not only produce milk but also calve on a regular, timely basis to provide replacements and beef animals.
In order to best utilize the regional forages and minimize the amount of forage that must be stored for Northern European winters, the dual purpose dairy cows were calved for the spring grasses, a cheap feed time. And they were dried off in winter time to minimize stored winter forage requirements.
Cows that did not conceive to calve the next spring were sent to slaughter in the fall and thereby their genetic impact on the breeding herd was terminated.
Very few cows, not in calf, could milk all winter and then increase production again when they were given spring grasses.
Cows produced 4,000 – 6,000 pounds in 200 to 250 days and bulls were run with the milking herd, so heat detection and timing of breeding were not issues.
Often milk processors paid a premium for summer milk so they could make their cheese and butter that were stored and sold in the winter when store prices were higher.

All these factors led to the cows calving in every spring being preferred.

Thoughts to Consider When Developing a Herd C.I. Plan

Through selection, feeding changes and husbandry changes dairy cattle and dairy farming has undergone significant changes. Here are factors to consider going forward:

USDA predicts that by 2025 confinement fed and housed cows will produce 33% more than they do today. Mature cows are predicted to produce 30,000+ pounds in 305 days.
In the future breeders will breed, feed and manage for daily and lifetime income over fed cost in addition to production of milk, fat, and protein yields.
Calving will always be the most stressful time for dairy animals
Ongoing research continues to show that 55 – 60 days is the ideal dry period
Technology will continue to replace labor on dairy farms so there will be less and less time to manage cows with problems or in times of stress.
Breeders will continue their current moves to breed and feed their herds for animals that carry more body condition (higher BCS) during the first 100 – 150 days of lactation.
Age at first calving will decrease to 18 – 20 months of age. Young first lactation cows may need to be handled separately

Have a C.I. Plan

Having a plan is always superior to taking what happens. Some choices of possible plans follow:

Milk Production Herds

For Moderate Management & Moderate Net Returns Herd
- Breed heifers using AI until 14 months of age then run a young bull with heifers
- Have voluntary waiting period of 75 days for first calvers and 50 days for later lactation cows
- Use AI for first services and run beef bulls with first calvers over 105 days in milk and cows over 90 days in milk. Sell the crossbred calves to provide a revenue stream.
- Plan and manage for a herd average 12.5 – 13-month calving interval

For Top Managed and High Net Returns Herds
- Breed heifers using AI until 13 months of age then run a young bull with heifers
- Have a voluntary waiting period of 150 days for first calvers and cows over 125 days in milk
- Use AI for first three services and run high index bulls with females milking over 175 days
- Plan and manage for a herd average 14-16 month calving interval

For Grazing Herds
- Bred heifers using AI until 14 months of age then run a young bull with heifers
- Have a voluntary waiting period of 45-50 days for all milking females
- Use AI for milking cows under 80 days in milk after than run a bull with milkers
- Schedule for 70 % of the herd to calve about two weeks before spring grass and two weeks after pasturing starts
- Plan and manage for a herd average 11.5 to 5-month calving interval

Buy Replacement for the Herds
- Buy in all herd replacements as first calvers
- Have a voluntary waiting period of 75 days
- Run a beef bull with all milkers. Sell calves for beef or beef herd replacements
- Plan and manage for a herd average 12-13 month calving interval

Breeding Stock Herds

Show Herds
- Breed heifers using AI starting at 13 months of age with some bred so they calve for the show season
- Have a voluntary waiting period of 75 – 85 days. Time some calvings for the show season
- Flush or IVF some top heifers and cows
- Market both live animals and embryos
- Use sires the have high type indexes. Be aware that some top show sires are below average for fertility and productive life
- Skinny cows will, on average, have longer calving intervals
- Potential buyers are seldom interested in progeny of herd bulls
- Calving interval will be as short as 12 months and as long as 24 months for animals flushed extensively

Top 1-5% Total Merit Herds
- IVF top heifers starting at nine months of age. Breed top 50% of heifers to elite genomic sires.
- IVF or flush top first lactation and only the elite older cows
- Implant bottom 50% of heifers and bottom 80% of milking cows.
- Market both live animals and embryos
- Use only top 1-5% sires, genomic or daughter proven. Natural sires will not have a place in the program
- There will be a wide variation in calving interval within the milking herd – majority of the time it will be 13-16 months

Herds Selling Some Breeding Stock
- Breed heifers starting at 11-12 months aiming for calving at 21-24 months.
- Have a voluntary waiting period of 80 days for first lactation and 60 days for other cows
- Sell surplus heifers and cows as herd replacements for other herds. There is not the profit in selling springing heifers that there once was. Fresh first calvers will be in There will be no demand for fresh older cows.
- Use top 10% sires, genomic and/or daughter proven
- Herd calving interval will range from 13-14 months

C.I. Mostly Management

C.I. encompasses all of management, genetics, nutrition and environment. But the key lies in management carrying out the plan.

On the genetic side sires below average for conception, daughter fertility, calving ease, daughter calving ease and, in the future, health traits should not be used in any herd. Any herd bulls used must be genomically tested in order to avoid any bull that will create calving problems.

Herd nutrition is important to fertility and calving interval, especially for heifers under one year of age and for females up to 150 days in milk.

At times breeders have been know to love cow families so much that they will tolerate delayed first calving and long calving intervals for family members. With raising replacements, the third largest dairy herd expense and every day beyond 60 days in dry pens costing $5 per day it is financially important that breeders not be soft on managing proactively for calving interval.

The Bullvine Bottom Line

There is not one answer to Is there an Ideal Calving Interval? Each breeder needs to decide for themselves. But make sure that the decision is made on an economic basis. Remember to include all lost revenue and costs incurred: days beyond 60 days dry; purchase of technology; labor; extra feed; and larger facilities.