@article{blake_mcdaniel_king_1979, title={COSTS OF MILK HARVEST IN DAIRY-CATTLE - IMPLICATIONS FOR DIRECT SELECTION AND COW CULLING}, volume={62}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(79)83440-2}, abstractNote={Abstract Labor and machine costs of milking were derived from data on Holstein and Jersey cows to determine their importance for direct selection and culling. The labor cost of milking Holsteins ranged from $.16 to $.27/day for milk yields when labor was valued at $4.50/h. Machine stripping comprised about one-third of this labor cost. Effects of lactation number for labor and machine costs were small, $.05 and $.02/day, for cows of same yield and stage of lactation. Standard deviations of labor and machine costs of milking Holstein cows were $13.39 and $7.25/305-day lactation. Variation in labor or machine costs was insufficient to warrant direct selection for improved economy of milking. Parity of cow could contribute to a decision to cull in extreme cases of low production and high labor and/or machine requirements but is otherwise inconsequential.}, number={9}, journal={JOURNAL OF DAIRY SCIENCE}, author={BLAKE, RW and MCDANIEL, BT and KING, RA}, year={1979}, pages={1424–1428} }
 @article{blake_mcdaniel_king_1978, title={LABOR AND MILKING MACHINE INPUTS TO MILK HARVEST IN DAIRY-CATTLE - IMPLICATIONS FOR DIRECT SELECTION}, volume={61}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(78)83623-6}, abstractNote={Abstract Components of variance, repeatabilities, and correlations among milking labor and machine inputs, flow rate, and yield characters were derived from data on lactating Holstein and Jersey cows and provided the basis for determining efficacy of direct selection for improved milking economy. Intralactation variance components for cow were 324, 121, and 7657s 2 /milking for total labor inputs, machine stripping, and actual machine time for Holsteins. Intralactation estimates were larger than estimates among lactations. Machine stripping was the primary component of total labor input that varied among cows. Intralactation repeat-abilities for total labor inputs, machine stripping, and actual machine input for Holsteins were .29, .20, and .42. The partial correlation of average flow rate with total labor inputs holding milk yield constant was —.56, exceeding that with peak rate. Elimination of machine stripping and minimizing overmilking appeared the best means of reducing average cost of milk harvest. Culling of cows exhibiting unsuitable demands for labor and machine inputs is a more appropriate strategy for improvement than direct selection for efficiency of milking labor.}, number={4}, journal={JOURNAL OF DAIRY SCIENCE}, author={BLAKE, RW and MCDANIEL, BT and KING, RA}, year={1978}, pages={474–488} }