Bias in Composite Milk Samples with Unequal Milking Intervals

Milk samples from a herd with milk intervals approximating 14-h nights and 10-h days were used to examine potential bias in measurements with composite samples. Six consecutive milkings were weighed and sampled individually. Composite samples for a day were determined mathematically from the data. C...

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Bibliographic Details
Published in:Journal of dairy science 1994-07, Vol.77 (7), p.1917-1921
Main Author: Hargrove, G.L.
Format: Article
Language:English
Subjects:
Animals
Bias
Biological and medical sciences
Cattle
CHOIX DE LA DATE
composite sample
CONTEO DE CELULAS SOMATICAS
ECHANTILLONNAGE
ELECCION DE LA EPOCA
False Positive Reactions
Food industries
Fundamental and applied biological sciences. Psychology
GRASA DE LA LECHE
Lactation
LAIT
LECHE
Lipids - analysis
MATIERE GRASSE DU LAIT
milk
Milk - chemistry
Milk and cheese industries. Ice creams
milking interval
MUESTREO
NUMERATION CELLULAIRE SOMATIQUE
ORDENO
PROTEINAS DE LA LECHE
PROTEINE DU LAIT
RENDEMENT LAITIER
RENDIMIENTO LECHERO
Time Factors
TRAITE
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Description
Summary:Milk samples from a herd with milk intervals approximating 14-h nights and 10-h days were used to examine potential bias in measurements with composite samples. Six consecutive milkings were weighed and sampled individually. Composite samples for a day were determined mathematically from the data. Composite samples with equal amounts from a.m. and p.m. milkings gave fat percentage measurements that were .07% above the true daily measurement. Using the milking interval to determine the portion of sample from each milking reduced this bias to –.02%. Protein percentage and SCC were satisfactory with equal sampling (mean bias of .01% and 7, respectively) but were improved slightly with milking interval sampling regimen (mean bias of .00% and 1, respectively). Fat yields were determined with equal portions, milking interval portions, and two plans available from DHIA, namely, alternate component sampling and alternate a.m.-p.m. Based on mean deviation from true fat yield, alternate a.m.-p.m. was as accurate as alternate component sampling, but variations were greater with alternate a.m.-p.m.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(94)77134-4