Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2010
Publication Date: 6/24/2010
Citation: Norman, H.D., Wright, J.R., Hubbard, S.M. 2010. Relationship of reason for lactation termination with genetic merit of Holsteins in the United States. Journal of Dairy Science. 93(E-Suppl. 1):594-95(abstr. W29). Interpretive Summary:
Technical Abstract: Reasons that producers report to 4 dairy records processing centers for why individual cows exit the herd (lactation termination codes) were examined for 6.2 million US Holsteins with lactation records that ended in 2007 and 2008 to determine their relationship to genetic merit. The most frequent termination reasons were lactation ended normally and cow stayed in the herd (68%), cow died (5%), and cow was sold for low production (4%), reproductive problems (4%), or mastitis (4%) or for dairy purposes (3%); 9% of lactations had no reason specified. For cows with normally ended lactations, mean predicted transmitting ability (PTA) and standard deviations (SD) were 135 ± 271 kg for milk, 5 ± 10 kg for fat, 4 ± 8 kg for protein, 2.95 ± 0.38 for somatic cell score (SCS), 0.8 ± 1.4 mo for productive life (PL), 0.1 ± 0.9% for daughter pregnancy rate (DPR), and net merit (NM) was $115 ± 132; corresponding means and SD for parent averages (PA) were 117 ± 219 kg milk, 4 ± 8 kg fat, 4 ± 6 kg protein, 2.95 ± 0.37 SCS, 0.6 ± 1.3 mo PL, 0.1 ± 0.9% DPR , and $98 ± 111 NM. Mean PTA and PA for all yield traits and PL as well as NM generally were lower for cows that did not end their lactations normally; lowest means were 18 kg for PTA milk, 1 kg for PTA fat, 1 kg for PTA protein, 0.2 mo for PTA PL, $37 for NM, 74 kg PA milk, 3 kg PA fat, 2 kg PA protein, 0.3 mo for PA PL, and $62 for NM for cows sold for low production and -0.2% for PTA DPR and -0.1% for PA DPR for cows sold for reproductive problems. Cows that aborted had the highest mean PTA for all yield traits (159 kg for milk, 5 kg for fat, and 5 kg for protein) and PA milk (125 kg). For SCS, PTA and PA were highest for cows with normally ended lactations and lowest (2.80 for PTA SCS and 2.81 for PA SCS) for cows that died; cows sold because of mastitis had mean PTA SCS of 2.91 and mean PA SCS of 2.90. Across termination categories, SD were similar for each trait except SCS. In general, cows with lactations that ended normally were genetically superior for all traits except SCS.