THE fertility performance of your dairy herd depends on several factors.
To maximize them, you must: feed your cows adequately (energy, proteins, minerals and vitamins); make sure your herd is in good health (check with your vet/farm adviser) and breed a fertile cow.
You also need to carefully plan and manage the breeding season. As breeding season approaches, cows need to be on an increasing plan for nutrition and maintaining body condition.
Grazed grass is the most economical way to feed the cow. It is essential to maximize the daily intake of grass.
Care must be taken not to overestimate grass consumption. Overestimating grass intake by 1 kg DM is equivalent to reducing concentrate feed by 1 kg.
If there is plenty of good quality grass available, the level of milk protein in the milk should also increase.
The protein level of your herd depends on the genetic potential of the herd (EBI of your cows).
If milk protein results are good and your grass pastures are good (up to 4cm), in 1400/1500 kgdm grass covers, then maintain concentrate levels.
If the protein is good and the grazing is bad, you need to reduce the concentrate level accordingly to improve the grazing. By doing this you increase the grass eaten by the cows and also get better pasture while ensuring the cows are well fed.
To meet the energy needs of a cow producing 2 kg of milk solids on 16 kg of grass dry matter, you need to feed about 2 kg of concentrates.
Grass alone at this time does not meet the cow’s needs for phosphorus, calcium, selenium, iodine and zinc. Cows also need a daily supply of cal mag to prevent grass tetany.
Dietary deficiencies of these minerals have been associated with low fertility, cystic ovaries, anoestrus, irregular or suppressed estrus, and early embryonic death.
Depending on the cow’s performance, even if her energy needs do not require concentrates, feeding 1/1.5 kg of concentrates may be one of the cheapest and, importantly, most effective ways of providing minerals before and during the breeding season. .
In 2021, the national average six-week calving rate was 67%. In a herd of 100 cows, this means that 67 cows calved in the first six weeks, including cows and heifers. April, May and June calving numbers were 12%, 7% and 2% respectively.
The reproductive cycle of the cow requires a period of rest and recovery before you can return to calve.
Identify cows calving later and any cows with problems – this group includes cows calved within four weeks of the start of the breeding season, they deserve special attention to ensure they return to calve.
This includes cows with a body condition score (BCS) of less than 2.75 on the mating start date (MSD).
By identifying cows that have had difficult calvings, milk fever, lameness, ecoli, mastitis, etc., allows you to be more aware of pre-breeding heat and seek veterinary intervention early if necessary.
Milking once a day (OAD) on cows with low SCC, late calving or lean cows, has proven to be very helpful in re-calving these cows during the breeding season. OAD milking reverses the trend of loss of body condition at the start of lactation and accelerates the resumption of their reproductive cycle. Cows under OAD have a higher conception rate at first service.
Using the once-a-day approach means that cows are usually inseminated within 50 days of calving. There are a variety of hormonal treatments available to induce heat in cows that have been calved for more than 30 days or more and without a cycle. If in doubt, talk to your veterinarian.
The start of AI is dictated by your expected calving start date. To achieve a high six-week calving rate, calve young heifers in February. Breed for sufficient replacements from cows of highest genetic merit (using EBI/Milk registration ratios). Decide which heat detection aids you will use and calculate the number of AI straws needed.
Your EBI herd ICBF scorecard can help establish the genetic strengths and weaknesses of the herd. Select a team of high EBI AI bulls that will enhance the strengths and offset the weaknesses of the herd.
Use a team of sires in equal numbers from the ICBF Active Dairy List to ensure you are making good genetic progress. Target high EBI females, typically virgin heifers, first and second calvings for the next generation of replacements.
The ICBF herd plus bull advisory tool is very useful for assigning your selected bulls to cows, based on their strengths and weaknesses. For more information on breeding, contact your Teagasc advisor.
• Pauline O’Driscoll is a dairy business and technology consultant based in Skibbereen.