INDILACT – Extended voluntary waiting period in primiparous dairy cows. Part 1: randomized controlled trial – compiled data and R–scripts with statistical calculations

The objective of the study is to investigate how an extended voluntary waiting period between calving and first insemination in primiparous cows would affect milk production and fertility during their first and second calving interval. The data is registered between August 2018 to September 2021. Data from 2 different sources. Access to these data is restricted due to the agreement with the principal owner of the data Växa Sverige. 1. Data (.txt files) from the Swedish Official Milk Recording System, operated by Växa Sverige regarding breed, calvings, inseminations, 305-d lactation yields, test-day yields, and dry-off dates from 16 farms. The inclusion criteria for the farms included herds with >100 dairy cows in production and a herd average milk production of at least 9 000 kg ECM/cow/year, a mean CI of < 14 months, and a system for daily milk yield registration. 2. Daily milk yields from the milking systems on the farms (three different types of systems: DeLaval, Lely and GEA), Excel files. Metadata available: One file with metadata, describing the data processing steps for each category of data, is provided. Also available are Code-lists for reading the data from the text files and for decoding the codes in the text files. R scripts with statistical calculations are also available. R-script with statistical methods and aggregated data used for statistical calculations for lactation 1 and 2. Raw data have been analyzed, summarized and new variables have been calculated in one Excel file per lactation from which data for the statistical calculations in R are taken. The R script needs acces to the Excel-files with summarized data to work. Linear models for calculation of: 1. 305d yield (kg + ECM), 2. Whole lactation yield (kg + ECM) 3. Milk yield per day in the first and second calving interval 4. Milk yield per day in 2 calving intervals 5. Calving interval 6. Lactation length 7. Milk yield at test milking 50-20 days before calving 8. Dry-off yield Binomial models for calculation of: 1. Dry period lenght class