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ABSTRACT: The prevalence, as well as the effect of subclinical ketosis on daily milk yield, was observed using 1.299,630 test-day records collected from January 2000 to December 2005 on 73,255 Slovenian Holstein cows. Subclinical ketosis was indicated by the fat to protein ratio (F/P ratio) higher than 1.5 in cows that yielded between 33 to 50 kg of milk per day (Eicher, 2004). The ketosis index was defined in relation to the timing of subclinical ketosis detection to the subsequent measures of test-day milk yields. The effect of subclinical ketosis on test day milk yields were studied separately for each parity using the mixed model analysis. The statistical model included the fixed effect of ketosis index, calving year-month, lactation stage and random effect of animals included in the study. The prevalence peak of subclinical ketosis occurred in the first month of lactation. Subclinical ketosis had a significant negative effect on daily milk yield. Decrease in milk yield in the amount of 4.21 kg/day; 2.73 kg/day; 2.78 kg/day; 2.83 kg/day; and 3.72 kg/day in each parity were determined within 35 days after the detection of subclinical ketosis. The decrease continued in subsequent milk controls. The research results show that test-day records could be a useful tool for early detection of subclinical ketosis.
Acta Veterinaria. 01/2009;
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ABSTRACT: The objective of this study was to evaluate relationship between milk yield in the first three lactations regarding levels of milk yield in the first lactation and levels of age at the first calving. Prediction of milk yield in later lactation based on milk yield in the earlier one was also carried out. The data used in this study were 5743 lactation yields collected from 1995 to 2003. All cows finished the first three lactations. Mean value of milk yield in the first lactation was 5283.5 kg, 6033.5 kg in the second and 6338.4 kg the third one. The milk yield estimation coefficients between the first and second lactation was 1.164, between the first and third was 1.231, and 1.079 between the second and third. The levels of milk yield in the first lactation highly significant influenced the value of estimation coefficient between first three lactations, while the age at first calving influenced less significantly. Determination coefficient (R2) values for models used in prediction ranged from 0.348 to 0.396.
AGRICULTURE: Scientific and Professional Review (ured@pfos.hr); Vol.11 No.2.
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ABSTRACT: The aim of this study was to evaluate nutritional status of dairy cows based on protein and urea content in milk in respect to stage of lactation and production levels of cows. 150 000 test day records from the regular milk recording (AT4 scheme) from 01.01.2004. till 31.10.2005. was used. Based on protein and urea content in milk 21,04% of cows lower level of production (D1), 22,48% of cows middle level of production (D2) and 18,29% of cows higher level of production (D3) had satisfactory nutritional status. Satisfactory nutritional status had 13,79% of cows in first stage of lactation (S1), 16,36% of cows in middle stage (S2) and 24,75% of cows in last stage of lactation (S3).
Stockbreeding (hrvatsko-agronomsko-drustvo@zg.t-com.hr); Vol.60 No.1.
