INDILACT - Individually adapted lactations lengths

Today a one year calving interval and a short lactation period, is recommended. The recommendations are based on 30 years old information and do not take into account individual variations between cows. In this project 20 large dairy herds are included. We gain information from the individual cows in each herd related to milk yield, fertility and health and validate the tools as predictors of cows which benefit from an extended lactation.

In this project, we are studying cows that are calving for the first time, primiparous cows, as these young animals generally have a more persistent lactation curve. In a sister project (Indilact II), extended calving intervals for second parity cows are also being studied.

In Part 1, cows in each herd were randomly assigned to have either an extended lactation, approximately 16 months, or a traditional lactation length aiming for about 12 months. 

In Part 2, we investigated how to utilize the information available during the early period after calving, such as milk production, genetic potential, and possibly diseases, to determine whether the cow should be inseminated early (resulting in a traditional calving interval) or whether insemination should be delayed for an extended calving interval.

The results we have obtained so far show that primiparous cows with extended calving intervals maintain their daily milk production per day in the calving interval, have better fertility, without negative impacts on health. Extended calving intervals may therefore be an alternative strategy that increase flexibility and resilience in high-producing dairy herds.

Further studies are planned to investigate long-term effects and to further develop predictors for which cows and farms this strategy may be best suited.

Scientific publications:

• Edvardsson Rasmussen, A., Holtenius, K., Båge, R., Strandberg, E., Åkerlind, M., Kronqvist, C., 2023. A randomized study on the effect of extended voluntary waiting period in primiparous dairy cows on milk yield during first and second lactation. Journal of Dairy Science 106, 2510–2518. https://doi.org/10.3168/jds.2022-22773
• Edvardsson Rasmussen, A., Båge, R., Holtenius, K., Strandberg, E., von Brömssen, C., Åkerlind, M., Kronqvist, C., 2023. A randomized study on the effect of an extended voluntary waiting period in primiparous dairy cows on fertility, health, and culling during first and second lactation. Journal of Dairy Science 106, 8897–8909. https://doi.org/10.3168/jds.2023-23470
• Edvardsson Rasmussen, A., Holtenius, K., Båge, R., Strandberg, E., Åkerlind, M., Kronqvist, C., 2024b. Customized voluntary waiting period before first insemination in primiparous dairy cows. Effect on milk production, fertility and health. Journal of Dairy Science. https://doi.org/10.3168/jds.2023-24593
• Edvardsson Rasmussen, A., 2023. Extended voluntary waiting period before first insemination in primiparous dairy cows: effects on milk production, fertility, and health. Acta Universitatis Agriculturae Sueciae. https://doi.org/10.54612/a.2skeendcfv

Popular science puplications:

• Edvardsson Rasmussen, A., 2024. "Ökad fruktsamhet med förlängt kalvningsintervall", Forskningsnytt djur mars 2024: https://www.slu.se/okad-fruktsamhet
• Edvardsson Rasmussen, A., 2023. "Bibehållen mjölkproduktion vid förlängt kalvningsintervall för förstakalvare", Forskningsnytt djur oktober 2023: https://www.slu.se/Forlangt-kalvningsintervall
• Karlsson, L., 2024. Så lyckas du med senarelagd inseminering [WWW Document]. Husdjur. URL https://etidning.husdjur.se/shared/spread/husdjur-2024-03-27-p24-25/aUM1aGSg (accessed 4.3.25).
• Grimstedt, L., 2024. Förlängt kalvningsintervall ger bättre fruktsamhet [WWW Document]. Tidningen Husdjur. URL https://husdjur.se/ovrigt/2024/forlangt-kalvningsintervall-ger-battre-fruktsamhet/ (accessed 3.6.24).
• Edvardsson Rasmussen, A., 2025. Förlängda kalvningsintervall. Ladugårdsförmannen 2-2025, s. 26–29.

Project manager:

Anna Edvardsson Rasmussen, Avdelningen för reproduktion, Institutionen för kliniska vetenskaper, SLU

Project group:

• Anna Edvardsson Rasmussen, anna.edvardsson.rasmussen@slu.se, (SLU)
• Kjell Holtenius (Institutionen för tillämpad husdjursvetenskap och välfärd)
• Cecilia Kronqvist (Institutionen för tillämpad husdjursvetenskap och välfärd)
• Renée Båge (Kliniska vetenskaper)
• Maria Åkerlind (Växa Sverige)
• Erling Strandberg (Institutionen för husdjurens biovetenskaper)
• Britt Berglund (Institutionen för husdjurens biovetenskaper)

Reference group:

Ann-Theres Persson, Växa Sverige, Carl Oskar Paulrud, DeLaval, Hans Stålhammar, Viking Genetics and Hans Andersson, Department of Economics, SLU