回分式乳量の精度および測定時の誤差要因について
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概要
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Seven brands of milk recording jar which are being marketed in Japan were subjected to accuracy tests. Three jars from each brand were employed, totalling twenty one. Accuracy tests of the measuring scale of the jars were conducted by using water of 5,15 and 25 kg at a temperature of uncontrolled (25-27℃) and 35℃, respectively. The results indicated that the measuring scale of all the jars tested had been graduated almost correctly, if corrections were made allowing for the fact that milk has a specific gravity of 1.03. To evalute the accuracy of the scale under an actural milking situation, seven miking tests were undertaken successively on sixteen milking cows, which consisted of four morning and four evening milkings. The number of cows tested for a jar for each milking was three on average, therefore the total number of measurements for each brand ranged 62-79 times depending on the brand. Sixteen jars out of 21 jars tested fell within ±3% of the true weight, and four jars over ±3% up to ±5%, and one more than ±5%. Results on the agerage value for each brand tended to underestimate the amount of milk produced with an exception for one brand. However, only one brand had a wider variation with more than ± 3% of the true weight on average. The number of jars which had a value in more than 95% of the observations within ±5% of the true weight was two out of three in two brands, and one out of three in four brands. Sampling devices of each jar were also tested during milking tests, and it was confirmed that all sampling devices yield samples that give unbiased estimates of the true content of milk when the sample drawing is done after a complete air agitation. Several factors which might bring errors in reading the scale were discussed. It was shown, in general, the faster the milk flow rate or the higher the foam height, the less the error in reading. No relationship exisits between the foam height and the error in the reading when the effect of milk flow rate is fixed. Although a negative correlation coefficient is found between the foam height and the error, the more the foam height, the more the error is observed when the effect of milk yield per milking is fixed.
- 日本家畜管理学会の論文
- 1984-02-27
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