|Appuhamy, R - VPI & SU|
|Cassell, B - VPI & SU|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2006
Publication Date: July 9, 2006
Citation: Appuhamy, R., Cassell, B.G., Cole, J.B. 2006. Effect of mastitis and postpartum metabolic diseases on lactation persistency of Holstein and Jersey cows [abstract]. Journal of Dairy Science. 89(Suppl. 1):398(abstr. 476). Technical Abstract: The objective of this study was to investigate the effects of clinical mastitis (CM) and post-partum metabolic disease (PPMD) on persistency of milk yield (P) in Holstein (H) and Jersey (J) cows. Data consisted of daily milk yields and health events for 59 H and 27 J calving between July, 2004 and March, 2005 in the Virginia Tech herd (Blacksburg, VA). Persistency was calculated as a function of a standard lactation curve and the linear regression of a cow’s test day deviations on days in milk, and standardized. Values of P > 0 indicate greater persistency. Standard curves were calculated from the data and did not account for breed differences. 10 test day yields before 128 DIM and 10 after were used to compute P for each cow; test day DIM were the same for all cows. Milk fever and ketosis were pooled into PPMD, and two CM classes were defined: occurrences before (CM1) and after (CM2) 128 DIM. Each disease was defined as a binary trait distinguishing between cows with at least one reported case (1) and cows with no cases (0). The statistical model included fixed effects of breed and parity, with two binary variables indicating the presence (1) or absence (0) of the disease of primary interest or any other disease. Frequencies of cows with MAST1, MAST2 and PPMD were 24.5%, 25.6% and 10.5% respectively. The effect of MAST1 on P was significant and had a phenotypic correlation of -0.20 with P. Thus, cows with mastitis in the first 128 d of lactation tended to be less persistent than cows with no mastitis. Correlations of MAST2 and PPMD with P were -0.04 and 0.14, respectively, and were not significant. Breed effects were highly significant, suggesting that H and J have differently-shaped lactation curves. Parity effects were not significant, as expected, because different standard curves are used for first and later parities.