First Lactation Performance and Herd Life

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Abstract
Records of artificially sired cows of 5 breeds having up to 5 or more lactations were divided into 4 groups according to 1st-lactation deviations from herd-mate average. The average deviation for each group in each of 4 succeeding lactations was greater than for the group which was below it in the 1st lactation. The fraction of cows having subsequent records was also greater for the groups highest in 1st-lactation deviations. The pattern was similar for all breeds. The Holstein results showed that more of the high producers (Group 1) in the 1st lactation had 2nd records than the low producers (Group 4)- 82 vs. 61%. More than twice as many had at least 5 records - 32 vs. 15%. The high producers in the 1st lactation not only continued to outproduce their lower-producing lst-lactation mates but also had a substantially longer herd life. These results do not substantiate the claim often made, that high producers in the 1st lactation burn themselves out and leave the herd at an early age. Actually, these cows appear to stay longer and produce more than their lower-producing lst-lactation mates.

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