Project Number: 1265-31000-096-01
Project Type: Specific Cooperative Agreement

Start Date: Sep 03, 2003
End Date: Aug 31, 2008

Objective:
Develop updated and more accurate factors to allow estimation of total daily milk, fat, and protein yields and somatic sell count (SCC) from milk weights and samples collected once or twice per day. A secondary objective is to account for management effects; possibly including milking interval, milking time, frequency of milking, geographic location, age and parity of cow, stage of lactation, breed, production level, and management system; that may influence the relationship between one or two milkings and daily yields, percentages, or SCC.

Approach:
Concerns remain in the US dairy industry about the use of the existing factors to estimate daily yield of milk, fat, and protein from single tests (or two tests for herds milked three or four times per day). These are commonly referred to as the AM-PM Factors. Additionally, time of day at which samples are collected is known to affect fat percentage and yield, to a lesser extent milk yield, but not protein. Factors currently used are based on limited and old records. Only limited information exists in literature about time of day effects on SCC. The cooperator, working closely with USDA-AIPL and National Dairy Herd Improvement Association (NDHIA) and other cooperating milk testing organization affiliates, will work to secure individual milking samples for all milkings of representative dairy herds on multiple days. Resulting data will be assembled into a database and combined with the small numbers of records that may already exist. The cooperator will work with USDA-AIPL to secure and verify the accuracy of collected data and will develop a data file of usable records to support research on AM-PM factors. In addition, the cooperator will develop programs to derive appropriate adjustment factors to estimate daily milk yield from single milking yields of milk, fat, and protein, while accounting for management factors that may affect the accuracy of estimating daily yield. A similar approach will be utilized to standardize SCC for milking intervals and time of collection. The impact of milking frequency on resulting AM-PM factors to standardize for milking interval may be increasingly important as more dairy herds move to frequent milking (4 times per day, especially for cows in early lactation) or irregular milking intervals (automatic milking systems). Bulk tank milk samples will be collected to determine their ability to assist in estimation of daily production when milk samples are not present for individual cows. Furthermore, the cooperator will work closely with USDA-AIPL and NDHIA to ensure that resulting factors to predict total daily milk, fat, and protein production are appropriate for use on all records collected throughout the US and incorporated in the national genetic evaluation system.