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Sampling of Milk Records for Estimating Lactation Yield

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Title Sampling of Milk Records for Estimating Lactation Yield
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Creator B.S. Gill
 
Subject First system of Estimation
Second system of Estimation
 
Description Not Available
1. For assessing the progress of cattle development schemes like the key village scheme, which operate on village cattle, it is necessary to estimate objectively the average lactation yield of the animals in the scheme. Maintenance of daily silk records being prohibitive in cost, it is necessary to evolve a suitable procedure of sampling of a Group of cows as also the days in milk of the selected cows and to develop an efficient method of estimation.

2. As a first approach to the problem, the daily milk records of 41 Haryana cows collected at the Government Livestock Farm, Hissar have been examined to study how far a procedure of sampling can be recommended.


3. It was found that the average lactation period of the herd was 301 days. The average lactation yield and the average daily milk yield were 1201 pounds and 3.9 pounds respectively. The coefficient of the variation between daily yields was 25 per cent.

4. The recording of milk yield at weekly intervals would provide an estimate of a single lactation yield with a precision corresponding to a standard error of about 1.5 per cent, which would be considered reasonably satisfactory for the purpose of rational supervision. An estimate based on weekly recording cannot, however, be relied upon in cases where the lactation yield is required to be estimated with margin of error less than 3 per cent.

5. The bias in the estimate Tb, of a single lactation yield, based on systematic sample mean was found to be less than one per cent for all the intervals of recording considered.

6. The gains in efficiency of the two arithmetic estimates, Tu and Tb, farmer based on the systematic sample totals and letter on systematic sample means, were 625, 408, 180 and 911 and 579,441,236 and 160 respectively, for recording at one week, two weeks, four weeks and eight weeks.

In the light of the fact that the bias present in Tb is negligible and because the increase in efficiency over Tu increases with the interval of recording, it may be recommended that the estimate Tb may be adopted for monthly or larger intervals of recording.

7. A limited empirical study indented that there is a further gain of about 150 per cent when the knowledge regarding the lactation curve is utilised in estimating a lactation yield from systematic sample recorded at 14 day interval. However, in view of the small number of cows that has been analysed for this item of study, it is not possible to make a firm recommendation.

8. From the moon squares, between the lactation yields of the cows and between systematic sample estimates within cows the number of cows required to be selected for milk recording at given intervals for estimating the average lactation yield of herds of different sizes with percentage standard errors of proscribed magnitude was found. The number of cows required to be sampled was almost the same for a given herd size and level of precision irrespective of the interval of recording. It was found that the average lactation yield may be estimated with 5 per cent standard error by sampling about 25 cows from a small herd of size 100 and about 30 to 35 cows from herds of larger size.

9. A method of approximately estimating the variance of the estimated average lactation yield was developed. It was shown that the estimate even a alight underestimation of the variance which is less than 2 per cent for even bimonthly sampling in herds of size larger than 300. However for small or herds underestimation is likely to be higher for longer intervals of sampling.

10. With the results obtained, the plan for milk recording in a village development programme such as the key village scheme for the purpose of estimating the average lactation yield of the population in the scheme was examined. A key village block consisting of six key villages contains about 5,000 cows of breeding age. It is envisaged that a milk recorder can record yield of three cow’s morning and evening every working day. We can thus record the yields of about 75 cows at monthly intervals or of 150 cows at bimonthly intervals. It was observed that the percentage standard error of estimate of the average lactation yield of the population of breeding cows was 3.2 per cent with monthly recording and 2.3 for bimonthly recording. It seems that in oases when the object is to estimate the average lactation yield of a group cow’s bimonthly recording is to be preferred.
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Date 2018-08-27T10:25:32Z
2018-08-27T10:25:32Z
1957-01-01
 
Type Dissertation/Thesis
 
Identifier B.S. Gill (1957) , Sampling of Milk Records for Estimating Lactation Yield , Unpublished Diploma in Agricultural and Animal Husbandry Statistics, IASRI, New Delhi
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http://krishi.icar.gov.in/jspui/handle/123456789/6569
 
Language English
 
Relation Not Available;
 
Publisher ICAR-IASRI (Erstwhile IARS), New Delhi