3.1. Choice of Data
Field data on birth weight, and calving performance for purebred Friesian Holstein cattle were obtained from the Dairy Industry or department of animal breeding, which is responsible for the Friesian Holstein dairy recording scheme. In total, the available calving data included information on calving traits for 3000 calves born from 2001 to 2004, and the weight data included information on birth weight for 2500 Friesian Holstein calves born from 2001 to 2004. Records where the calf was the result of embryo transfer or not embryo transfer single born were excluded from the analyses, as were observations of calves with cows older than 168 mo of age. Observations on birth weight outside the accepted range of 18 to 75 kg were discarded. The majority of discarded observations were excluded because of too small herd-year contemporary groups. After these edits, the final data set included information on calving traits for 2700 Friesian Holstein calves and on birth weight for 2200 Friesian Holstein Dairy.
Data Structure
Relationship information dated back to animals born in the late 1990s. The identities of cow and sire were known for 100% and close to 100%, respectively, of all calves with observations. The identity was also known for more than 98% of maternal grandsires and grandcowes of all calves with observations. Records of parity number were not available and had to be calculated from the full data set. If a cow was older than 44 mo at the birth first recorded calf, the observation was grouped with those from later parities. In the data average ages of cows at first and later parities 24 mo and 60 mo, respectively for Friesian Holstein. The age of the cow at first parity was grouped as 20 to 25, and 26 to 30, and 31 to 35, and 36 to 44 mo of age, and for later parities, the classes were less than 42 to 54, 55 to 66, 67 to 78, and 79 to 168 mo of age at calving. Four season of calving (November to February, March and April, May and June, and July to October) were used in the analyses. Birth herd–yerd contemporary groups were small, with the median size ranging from four records for Friesian Holstein, three records. The ratios of numbers of male and female calves in first and later parities, respectively, were 0,97 and 1,06.
Field data on birth weight, and calving performance for purebred Friesian Holstein cattle were obtained from the Dairy Industry or department of animal breeding, which is responsible for the Friesian Holstein dairy recording scheme. In total, the available calving data included information on calving traits for 3000 calves born from 2001 to 2004, and the weight data included information on birth weight for 2500 Friesian Holstein calves born from 2001 to 2004. Records where the calf was the result of embryo transfer or not embryo transfer single born were excluded from the analyses, as were observations of calves with cows older than 168 mo of age. Observations on birth weight outside the accepted range of 18 to 75 kg were discarded. The majority of discarded observations were excluded because of too small herd-year contemporary groups. After these edits, the final data set included information on calving traits for 2700 Friesian Holstein calves and on birth weight for 2200 Friesian Holstein Dairy.
Data Structure
Relationship information dated back to animals born in the late 1990s. The identities of cow and sire were known for 100% and close to 100%, respectively, of all calves with observations. The identity was also known for more than 98% of maternal grandsires and grandcowes of all calves with observations. Records of parity number were not available and had to be calculated from the full data set. If a cow was older than 44 mo at the birth first recorded calf, the observation was grouped with those from later parities. In the data average ages of cows at first and later parities 24 mo and 60 mo, respectively for Friesian Holstein. The age of the cow at first parity was grouped as 20 to 25, and 26 to 30, and 31 to 35, and 36 to 44 mo of age, and for later parities, the classes were less than 42 to 54, 55 to 66, 67 to 78, and 79 to 168 mo of age at calving. Four season of calving (November to February, March and April, May and June, and July to October) were used in the analyses. Birth herd–yerd contemporary groups were small, with the median size ranging from four records for Friesian Holstein, three records. The ratios of numbers of male and female calves in first and later parities, respectively, were 0,97 and 1,06.
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