Repeated Pre-Weaning Weights

The following formula refers to the case of two recordings (n = 2) of weight after birth. The procedure can be applied to any number n of recordings, noting that the reference age in this case should be comprised of the age intervals from two successive recordings, or, if this is not possible, should be closest to the last available record. The age range tolerance or limitation values should be specified by the recording organization, based on recording frequencies etc. let RA be reference age let RW be weight at reference age let DB be birth date let Dt-1 be recording date 1 let Dt-2 be recording date 2 let Wt-1 be recorded weight at date 1 let Wt-2 be recorded weight at date 2 let At-1 be age of animal at recording date 1 ( = Dt-1 - DB) let At-2 be age of animal at recording date 2 ( = Dt-2 - DB) If RA < At-1 then RW = {[(Wt-2 - Wt-1)/(At-2 - At-1)]*(At-1 -RA)} - Wt-1 If At-1 < RA < At-2 then RW = {[(Wt-2 - Wt-1)/(At-2 - At-1)]*(RA - At-1)}+ Wt-1 If RA > At-2 then RW = {[(Wt-2 - Wt-1)/(At-2 - At-1)]*(RA - At-2)} + Wt-2

Where with the exception of birth weight, there is only one weight record available after birth: let AR be reference age let WR be weight at reference age let DB be birth date let Dt be recording date t let WB be birth weight let Wt be recorded weight at date t let At be age of animal at recording date ( = Dt - DB) If AR < At then WR = [(Wt - WB)/ At]*AR + WB If AR > At then WR = {[(Wt - WB)/ At]*(AR - At)]} + Wt