Sorting system for cattle

A method of sorting, treating, and feeding a group of bovine animals in a feed lot, the method comprising the steps of:

• a.) determining a weight of each animal, and comparing the weight of each animal with the weight of the other animals in the group;
• b.) determining an ob genotype of each animal, the ob genotype determined by whether the animal is a TT animal, homozygous with respect to the T-allele of the ob gene, a CC animal, homozygous with respect to the C-allele of the ob gene, or a CT animal, heterozygous with respect to the T-allele and the C-allele of the ob gene;
• c.) determining a back fat measurement of each animal, and comparing the back fat measurement of each animal with the back fat measurement of the other animals in the group;
• d.) dividing the animals into a plurality of subgroups wherein:
• i.) a first subgroup includes at least CC animals with comparatively less weight and back fat;
• ii.) a final subgroup includes at least CT and TT animals with comparatively more weight and back fat;
• and
• iii.) at least one intermediate subgroup includes animals with intermediate weight and back fat;
• e.) adding zilpaterol hydrochloride at a selected date prior to a slaughter date to a feed ration fed to animals only in selected subgroups, such that animals in unselected subgroups receive no zilpaterol hydrochloride;
• and
• f.) feeding each subgroup for a finishing period subsequent to the selected date and then moving the animals from the feed lot to slaughter;
• wherein all CC animals are in selected subgroups receiving zilpaterol hydrochloride, and only CT animals and TT animals are present in unselected subgroups receiving no zilpaterol hydrochloride;
• wherein CC animals, CT animals and TT animals are present in all selected subgroup receiving zilpaterol hydrochloride;
• and
• wherein the slaughter date and finishing period for each subgroup is independent of the slaughter date and finishing period for other subgroups.