Abstract
The objective of this study was to determine the effect of various milk recording methods (A4, AT4, A6, AT6) on prediction accuracy of 100, 200 and 305-day milk yield. The data used in this study were 11,430 individual test-day milk yield records collected from November 2004 to November 2006 on 813 cows reared on 15 family farms in Croatia. Milk recording was performed according to A4 and A6 milk recording method by the field officer of the Croatian Livestock Centre. From the corrected database with test-day records, two different datasets were created. The first dataset (A4; n = 7,500) included test day records collected every four weeks, while the second dataset (A6; n = 3,830) included test day records collected every six weeks. When lactation milk yields were predicted from alternative milk recording methods (AT4, AT6), daily (24 h) milk yield was estimated from single evening or morning milk yield using linear model that taken into account effect of interval between successive milkings. Lactation milk yield was calculated for three different days in milk (100, 200 and 305 days) using the Test Interval Method (TIM) that is reference method by ICAR (ICAR, 2003). Results show that the alternate milk recording method at 4-week intervals provides low bias and high accuracy of prediction of 100, 200 and 305-milk yields, while milk recording methods at 6-week intervals gives prediction of 305-milk yield with higher bias and lower accuracy.
Highlights
Milk recording provides collection of data necessary for genetic evaluation and herd management of dairy animals
When lactation milk yields were predicted from alternative milk recording methods (AT4, AT6), daily (24 h) milk yield was estimated from single evening or morning milk yield using linear model that taken into account effect of interval between successive milkings
The results shown in table 1 indicate that the differences between 100-day milk yields predicted from A4, AT4, A6 and the AT6 milk recording methods were not statistically significant (P > 0.05)
Summary
Milk recording provides collection of data necessary for genetic evaluation and herd management of dairy animals. Increased participation in milk recording and cost reduction could be achieved by extending the interval between successive milk recordings, by measuring only evening or morning record per test-day (alternative milk recording method) or by their combination. Many researchers have investigated the effect of reducing the frequency of milk recording to prediction accuracy of lactation yields. Hargrove, 1994 and Wangler et al, 1996 reported that with the extension of interval between successive recordings, the prediction accuracy decreases as well as the cost of recordings. McDaniel (1969) reported that 93% of the proportional differences between actual milk yield and milk yield predicted from monthly samples were less than 0.05 and that 100% of the proportional differences between the actual and predicted milk yield were less than 0.10. Berry et al (2005) reported that with heifers, the A8 scheme predicts on average a 305-day yield similar to A4-predicted 305-day yield
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