INDILACT - Extended voluntary waiting period in primiparous dairy cows. Part 1: randomized controlled trial

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. I. Daily milk yields from the milking systems on the farms (three different types of systems: DeLaval, Lely, and GEA), Excel and CSV files. The majority of data is available, but there are holes with lacking information due to files not being sent from the farms before they were deleted from the milking systems. Variables Farm-ID, cow-ID, date and time for milking, milk yield per milking (kg). II. .txt files with information about calvings, cullings, inseminations, parentage. Registered by Farm owners, staff, and animal health staff and .txt files with information about test milkings, lactation yields and yearly yields. Registered by Farm owners, and Eurofins lab. Variables: 1. Calvings: FarmID, cow-ID, birth year, calving date, easy/difficult calving, calf sex, calf-ID, calf use, calving number 2. Parentage: FarmID, cow-ID, birth date, sex, father ID, father farm ID, birth year father, father breed, milk-index father, mother ID, mother farm ID, birth year mother, mother breed, milk-index mother, grandfather-ID, grandfather-farm ID, birth year grandfather-, grandfather-breed, milk-index grandfather 3. Inseminations: FarmID, cow-ID, insemination date, ear number used bull, pregnancy diagnosis, pregnancy diagnosis date 4. Culling: FarmID, cow-ID, in date (bought to the farm or birth), culling date, culling reason 1-3 5. test milking: FarmID, Cow-ID, birth year, Test milking date, kg milk, % fat, % protein, somatic cell count (SCC), urea, udder health cathegory 6. 305-day lactation yield: FarmID, Cow-ID, birth year, calving date, calving number, kg milk, kg fat, kg protein, farm breed mean kg fat, farm breed mean kg protein. 7. Dry-off date: FarmID, Cow-ID, dry-off date III. 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