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Development and Evaluation of Alternate Testing Procedures for Official Records

Animal Physiology and Genetics Institute, Agricultural Research, Science and Education Administration, US Department of Agriculture, Beltsville, MD 20705

ABSTRACT

In one trial, electronic recording devices were installed on farms to monitor starting and ending times of milking. Operators also were requested to record starting and ending time for each milking. Milking intervals from these two procedures frequently (17% of the observations on one farm) deviated by an hour or more. However, deviations of milking interval were longer than 1 h on only one farm.

In a second trial, milk and fat yield measured separately for morning and evening milking on six farms were used to examine differences between yield estimated from single milking and from the total of two consecutive milkings (test day).

Deviations of test day yield estimated from single milkings were within 2 kg of the test day total in 80% of the milkings. However, a small percentage of the deviations were greater than 5 kg. Deviations other than cow or interval length appeared to be mainly random variation.

Cumulative yields based on alternating morning-evening or evening-morning samples and on morning only or evening only samples were computed and deviated from cumulative yield based on test day totals. Deviations of records initiated with a morning milking or from only morning records from test day records were consistently negative. The mean difference in cumulative yield estimated from single milkings and from test day yields for lengths of cumulative production ranged from –11 to –154 kg. Standard deviations of the difference for records based on more than four tests were between 100 and 235 kg.