Research Impact Highlights – Dairy
Carbon breeding index for dairy cows
Laurence Shalloo, Johnathan Herron and Donagh Berry (AGRIP)
The Economic Breeding Index (EBI) for dairy cow selection has been proven to reduce the carbon footprint per unit of milk produced. However, because of increased milk production associated with EBI selection, overall greenhouse gas emissions remains static. A sub-index within the EBI was needed that reflected overall emissions associated with individual animals, while also improving herd profit.
Research at Teagasc Moorepark led the development of a sub-index for the EBI and dairy-beef index (DBI) that’s now being used to rank dairy and beef bulls and cows on expected overall carbon emissions, and which reflects emission values on different traits within the two breeding indexes. Because the carbon sub-index is a component of the two breeding indexes, the overall index framework ensures the parents of the next generation improve profit while concurrently reflecting associated emissions.
This sub-index launched in November 2022 and is being used to select bulls and females by dairy farmers in the 2023 breeding season. All dairy animals and beef bulls for use on dairy females have a value for their expected carbon emissions, converted to an economic carbon sub-index within the overall EBI and DBI.
Clover150: reducing N on farm
Michael Egan, Michael O’Donovan and Caitlin Looney (AGRIP)
White clover can be used on-farm to reduce reliance on chemical nitrogen (N) fertiliser to grow grass, benefiting farmers through reduced costs and the environment by reducing losses to waterways and reduced emissions. In 2021, a group of 30 farmers started a five-year clover incorporation programme on their farms, aiming to reduce chemical fertiliser levels while maintaining overall grass growth, leading to an overall reduction in N surplus (potential N loss to the environment). Researchers from Teagasc Moorepark provided information on white clover management and tailored management strategies for each farmer. Clover on farm was estimated three times each year (2021 and 2022) and the group met four times a year, with an additional 12 national farm walks carried out to disseminate results.
Between autumn 2021 and 2022, the area in clover increased from 44% to 61% on programme farms, resulting in a 23% reduction in chemical N fertiliser use and a 22% reduction in purchased N surplus, reducing environmental losses and costs to farmers. Clover150 farmers shared results through local discussion groups and farm walks. In the coming years, as the clover area increases on farm, there’s greater potential to reduce the purchase and application of chemical N, while maintaining feed self-sufficiency through high grass growth levels.
A sustainable breeding strategy for dairy farms
Stephen Butler (AGRIP)
Artificial insemination is widely used in dairy farms, but traditionally resulted in equal numbers of male and female dairy calves. The fate of male dairy calves is a welfare concern, presenting a reputational risk for the dairy sector. Sexed semen — the ability to bias the sex of dairy offspring to produce 90% female calves — is a revolutionary technology for dairy farming. Teagasc-led research has identified strategies to generate replacement heifer calves using sexed semen, facilitating increased beef semen use for non-replacement calves for a more sustainable calf population.
Sexing Technologies, the global leader in sexed semen production, established a lab at Teagasc Moorepark providing a sex-sorting service to the Irish cattle breeding industry, increasing sexed semen usage in dairy herds. In 2023, up to one-third of replacement dairy heifers could be generated using sexed semen.
This allows dairy farmers to accelerate genetic gain by breeding replacement heifers from their best dams, and generate beef-cross calves from the remaining dams, improving dairy sector sustainability. The beef sires used to generate beef-cross calves are primarily early maturing breeds, resulting in reduced lifetime methane emissions compared with male dairy calves.
Contact: stephen.butler@teagasc.ie
Other contributors: ICBF, UCD, Sexing Technologies, NCBC, Munster Bovine, Progressive Genetics, Dovea Genetics.
Funding: Dairy Research Ireland, FBD Trust, Department of Agriculture, Food and the Marine, Munster Bovine, Glanbia, Meat Industry Ireland, Dairy Industry Ireland, and Ceva Santé Animale.
Impact Pathway: Technology Development & Adoption.
Reducing antibiotic usage in dairy cows
Clare Clabby, Pablo Silva Boloña, Ainhoa Valldecabres and Pat Dillon (AGRIP)
To reduce antimicrobial resistance risk, linked to antibiotic overuse, regulations require that intramammary antibiotics only be used on cows with noticeable intramammary infections. Cows not noticeably infected should be treated with internal teat sealant. Typically, cows with SCC (somatic cell count – an infection indicator) under 200,000 cells/mL are considered not infected, a guideline often used for assignment of dry cow therapy.
In exploring optimal SCC for infection detection, 2,074 cows were studied. Bacteriological results from late lactation milk samples were used to define cows as infected or uninfected. Sensitivity and specificity analysis were performed using test-day SCC to predict intramammary infection. The infection threshold was determined as 65,000 cells/mL for all cows using the last test-day SCC record 37-64 days before dry-off.
Results showed that cows below this SCC level can be treated with internal teat sealant alone at dry-off, reducing antibiotic use without losing opportunities to treat existing infections and maintaining udder health. Emphasis on hygiene is recommended at dry-off and during the dry period to ensure successful outcomes. Results have been presented to Animal Health Ireland and farmers at national conferences, and incorporated into Teagasc advisory services recommendations.
Contact: clare.clabby@teagasc.ie
Other contributors: Kerry Agribusiness and University of Limerick.
Funding: Dairy Research Ireland.
Impact Pathway: Technology Development & Adoption.