Paper-Lecture52 - Effects of Milk Fever, Ketosis, and...

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1999 J Dairy Sci 82:288–294 288 Received July 17, 1998. Accepted October 20, 1998. Effects of Milk Fever, Ketosis, and Lameness on Milk Yield in Dairy Cows P. J. RAJALA-SCHULTZ, *,² Y. T. GRO ¨ HN,* and C. E. McCULLOCH *Section of Epidemiology, Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853 ² Department of Clinical Veterinary Sciences, Faculty of Veterinary Medicine, PO Box 57, FIN-00014 Helsinki University, Finland Biometrics Unit, Department of Statistical Science, Cornell University, Ithaca, NY 14853 ABSTRACT The effects of milk fever, ketosis, and lameness were studied using data from 23,416 Finnish Ayrshire cows that calved in 1993 and were followed for one lactation (i.e., until culling or the next calving). Monthly test day milk yields were treated as repeated measurements within a cow in a mixed model analy- sis. Disease index variables were created to relate the timing of a disease to the measures of test day milk. Statistical models for each parity and disease in- cluded fixed effects of calving season, stage of lacta- tion, and disease index. An autoregressive correlation structure was used to model the association among the repeated measurements. The milk yield of cows contracting milk fever was affected for a period of 4 to 6 wk after calving; the loss ranged from 1.1 to 2.9 kg/d, depending on parity and the time elapsed after milk fever diagnosis. Despite the loss, cows with milk fever produced 1.1 to 1.7 kg more milk/d than did healthy cows. Milk yield started to decline 2 to 4 wk before the diagnosis of ketosis and continued to decline for a varying time period after it. The daily milk loss was greatest within the 2 wk after the diagnosis, varying from 3.0 to 5.3 kg/d, depending on parity. Cows in parity 4 or higher were most severely affected by ketosis; the average total loss per cow was 353.4 kg. Lameness also affected milk yield; milk loss of cows diagnosed with foot and leg disord- ers varied between 1.5 and 2.8 kg/d during the first 2 wk after the diagnosis. ( Key words : metabolic diseases, milk yield, repeated measures, mixed model analysis) INTRODUCTION Milk fever and ketosis are metabolic diseases of dairy cows that usually occur at the time of calving or early in lactation, respectively. Lameness, however, can occur at any time during the lactation. The literature gives conflicting results on the ef- fects of these diseases on milk yield. Dohoo and Mar- tin (5) reported that clinical ketosis and foot and leg disorders have a beneficial effect on milk yield and subclinical ketosis have a detrimental effect. Detilleux et al. (4) found milk yield to be affected by ketosis, but, despite that, the ketotic cows yielded more than their healthy herdmates. Many studies (5, 10, 13) have not found any association between milk fever and milk yield. Several statistical approaches have been used to evaluate milk losses caused by diseases. Some of the discrepancies found in the liter-
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This note was uploaded on 09/19/2011 for the course ANS 5446 taught by Professor Brown during the Spring '08 term at University of Florida.

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Paper-Lecture52 - Effects of Milk Fever, Ketosis, and...

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