The use of prolonged intervals between milk weighings and butterfat tests in milk recording

Livestock Production Science, 3 (1976) 155--163 155 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

THE USE OF PROLONGED INTERVALS BETWEEN MILK WEIGHINGS AND BUTTERFAT TESTS IN MILK RECORDING

E.J. IPSEN and J.O. K J E L D S E N

Instituteof Animal Science, The Royal Veterinary and Agricultural University,Copenhagen (Denmark) (Received October 28th, 1975)

ABSTRACT Ipsen, E.J. and Kjeldsen, J.O., 1976. The use of prolonged intervals between milk weighings and butterfat tests in milk recording. Livest. Prod. Sci., 3: 155--163. Alternative methods of milk recording have been investigated. The aim of the investigation was to examine the significance of simplified and thus less expensive methods of recording. The investigation was based on Danish data from 1146 cows tested at weekly intervals at Progeny Testing Stations and 4196 lactation records from four-weekly tests by Milk Recording Societies. An increase in the intervals between milk weighings and butterfat tests resulted in a small increase in S.D. of bias; however, the bias was not significant for intervals up to 12 weeks. The results indicate that lactation records from bimonthly or trimonthly tests are reasonable alternatives to a traditional recording once a month as far as utilization of data for breeding purposes is concerned. Cases were investigated where milk weighings were fixed to 4- or 8-week intervals and the number of butterfat tests varied during lactation. The results indicate that milk weighing at 4-week intervals and butterfat tests at 12-week intervals gives approximately the same significance of production records as testing for both milk and butterfat with 8-week intervals. Recording in the first part of the lactation may cause a large part of the error of the lactation record. By correcting for length of the interval between calving and first recording it is possible to reduce the S.D. of bias. Possibilities of using butterfat tests from dairy plants were investigated. Even a reduction in butterfat tests to one per cow in each lactation combined with the herd average o f butterfat percentage from the dairy plant may give a reasonable significance in data from Milk Recording Societies.

INTRODUCTION M i l k a n d b u t t e r f a t y i e l d s are u s u a l l y e s t i m a t e d f r o m a l i m i t e d n u m b e r o f milk weighings and butterfat tests throughout lactation. Based on such estimates t h e p r o d u c t i o n d a t a h a v e t o b e c a l c u l a t e d f o r u s e o n t h e f a r m as well as o f f t h e f a r m as a b a s i s f o r b r e e d i n g , f e e d i n g a n d m a n a g e m e n t o f d a i r y c a t t l e . S i n c e m i l k y i e l d s a n d b u t t e r f a t p e r c e n t a g e are s u b j e c t t o c o n s i d e r a b l e v a r i a t i o n both day-to-day and throughout lactation the traditional opinion of estimates

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was that the longer the interval between recordings the greater the error was likely to be. Early work on this subject has been summarized by Ashton (1956). It is the aim in most countries that official testing should take place once a m o n t h in order to provide adequate data for feeding plans, a certain system of identification of animals and reasonable data to be used for progeny testing and in breeding selection programmes. In Norway it is approved that the Milk Recording Societies can reduce the number of butterfat testings to 6 a year (Westgaard, 1972). In other countries different methods have been tried in order to reduce the time the milk recorder has to spend at the farm, thus reducing the general expenses of milk recording. A paper presented by Hartmann (1971) deals with methods for optimal structuring of expenses and profit and indicates that simplified methods for recording may lead to the same or even better results than a traditional 4-week recording. Results of recent years indicate that the use of bimonthly records instead of m o n t h l y records would reduce cost without affecting the applicability of the testing results e.g. Cunningham and Vial (1968), D o l b y (1969) and McDaniel (1969). Keown and Van Vleck (1971) found that estimates of genetic gain, selecting on bimonthly or trimonthly test days, were almost as great as selecting on m o n t h l y test days by selecting on the completed 305-days lactation records. MATERIALS AND METHODS

Data were used from the Danish Progeny Testing Stations from the testing year 1969--1970 and comprised 61 sire progeny groups with 1146 cows tested at 20 stations. Distributed by breed there were 448 cows of Red Danish breed, 457 cows of Danish Friesian and 241 cows of Danish Jersey. A b o u t half of the cows had finished a 305-days lactation. At these stations the cows were kept under similar conditions for the first 304 days of the first lactation period. The milk recording was carried out on t w o consecutive days each week and covered exactly 48 hours. The butterfat percentage was tested once a week on the basis of the t w o days sampling (Nielsen and Vesth, 1971). The other part of the data used in this investigation was obtained from Danish Milk Recording Societies. In accordance with the Danish regulations for milk recording, these societies operate in "recording years" that run from October 1st to September 30th. Milk weighing and butterfat tests were carried out at least 13 times a year and each sampling period was 24 hours (National Danish Committee on Breeding and Management of Cattle, 1971). Data were collected for the years 1968--1969 and 1969--1970 and covered all tested herds and every tested c o w at four societies in the Province of Sealand. These production data included 45 herds and 3807 cows with at least one 305-days lactation. A total of 4196 lactation records were analysed. The distribution b y breed was 1228 cows from herds of R e d Danish breed, 952 cows from herds of Danish Friesians, 223 cows from herds of Danish Jerseys and 1793 lactation records from herds with more than one dairy breed.

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For each of the methods investigated the standard deviation (S.D.), the bias, the standard deviation of bias and the correlation were calculated. Data obtained in weekly tests in the material from Progeny Testing Stations and data obtained with a test interval of four weeks in the material from Milk Recording Societies were used as a basis. Prolonged intervals were selected at random. The analyses of the data were based both on individual breeds and on all breeds together. Table I shows results for Red Danish cows alone and Table II shows results for Danish Friesian cows alone but similar results have been obtained with the other two breeds. All computing work for this specific study was carried out at the Northern Europe University Computing Center, Copenhagen. RESULTS AND CONCLUSIONS

Length of interval between milk weighings (data from Progeny Testing Stations) Table I shows results for all Red Danish cows with a lactation of 305 days. In Sector A are shown results where lengths of testing intervals are equal for both milk weighing and butterfat tests. As far as S.D. of bias is concerned there is a slight increase with increase in the length of testing interval up to 16 weeks, however none of the biases are significant.

Length of interval between butterfat tests (data from Progeny Testing Stations) Table I, Sector B shows results where some of the butterfat tests are omitted and replaced by immediately preceding tests. These results indicate t h a t butterfat testing at either 8- or 12-week intervals may be possible alternatives to traditional testing methods. S.D. of bias is 3.7 kg of butterfat when testing at 4week intervals for both milk and b u t t e r f a t and it increases to 6.1 kg or 7.2 kg if the interval for butterfat testing is 8 or 12 weeks, respectively.

Length of interval between milk weighings (data from Milk Recording Societies) Table II shows results for all cows of Danish Friesian breed with a lactation of 305 days. The testing intervals used in this investigation are 4, 8, 12 and 16 weeks for both milk weighings and butterfat tests. The average n u m b e r of milk weighings during lactation varies from 11.1 to 3.0. The results show the same t e n d e n c y as illustrated with the data from the Progeny Testing Stations in Table I. As indicated in Table II there is an increase in S.D. of bias with an increase of length of testing interval. None of the bias found for intervals up to 12 weeks is significant as shown in Table II.

Length of interval between butterfat tests (data from Milk Recording Societies) The testing intervals used in this investigation are 4 weeks for milk weighing

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and 8, 12 or 16 weeks for butterfat tests. Further, a test is investigated with 8 weeks b e t w e e n milk weighing and 16 weeks between butterfat tests. Testing for milk at 4 weeks and for butterfat at 12-week intervals gives a S.D. of bias at 10.5 kg butterfat (Table II, Sector B) and testing for both milk and butterfat at 8-week intervals gives a S.D. of bias at 8.6 kg butterfat (Table II, Sector A).

Error due to the first testing period o f the lactation Previous work on this subject e.g. Johansson (1942), has indicated that a large part of the error of the whole lactation record is due to the error of the first testing of the lactation since the interval between calving and first recording varies. Recent studies by Auran {1973) have indicated that the length of the first period has the largest influence on the yield on the first and the last three to four test days and this effect might be of noticeable size when evaluating individual records. Fig. 1 shows h o w the estimated yield deviates from the real production data with an increased interval between calving and first recording. This illustration is based on data from Progeny Testing Stations. Weekly test data are used as the initial position.

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The results of this investigation confirm that recording in the first weeks of lactation may cause a large part of the error of the lactation record. The results also indicate that it is possible to reduce the S.D. of bias by using correction factors for the interval between calving and first recording.

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Results indicate an increase of significance in the case where butterfat tests from the first t w o weeks after calving are o m i t t e d and when butterfat tests are based on t w o or three samplings equally distributed during the lactation. In Table II C some details of such an investigation are shown. Three b u t t e r f a t tests at 12-week intervals according to this m e t h o d give the same significance as 4 butterfat tests according to the m e t h o d referred to in Table II Sector B.

Use o f average herd butterfat tests when calculating lactation records for individual cows Possibilities of using butterfat tests from dairy plants in the Milk Recording Societies have been investigated even though such tests are average herd butterfat and do n o t include tests for individual cows. In Table I I D results are shown from an investigation in which the butterfat percentage in milk from individual cows is based on one individual test for each c o w combined with the herd average of butterfat percentage from the dairy plant. Even with such a great reduction in the number of butterfat tests for individual cows the S.D. of bias is n o t more than 12.9 kg butterfat and the correlation between yield found by the official m e t h o d and the simplified m e t h o d of the butterfat testing is 0.95. DISCUSSION

Results from both Milk Recording Societies and Progeny Testing Stations indicate that it is possible to use simplified and less expensive methods of milk recording. The material from Progeny Testing Stations includes only first lactations; the weighing and sampling at the stations covered 48 hours and were carried o u t by specific trained personnel and so the situation in the stations is different from normal practice. The main reason for using this material is that results from weekly recording form a good basis for comparison with prolonged intervals. Preliminary data from the Milk Recording Societies used in this investigation (Ipsen and Kjeldsen, 1973) have been analysed in a study of estimation of breeding value (Madsen and Christensen, 1974). This shows that relative genetic gain is a b o u t the same whether the selection is based on monthly, bimonthly or trimonthly recording. Further, our results indicate possibilities of ranking bulls according to the yield of their daughters in cases with a simplified m e t h o d of butterfat tests. For the purposes of feeding and management of a herd it is important to have regular visits of the milk recorder. However, a system based on m o n t h l y short visits of the recorder, m o n t h l y milk weighings b y the farmer and three or four analyses of milk from individual cows at regular intervals during the lactation may give all essential information for breeding, feeding and management purposes and thus form an alternative to traditional testing methods, especially for farms with a limited number of cows.

162 ACKNOWLEDGEMENTS

The author extends his sincere thanks to the Danish Government Research Council (Statens Jordbrugs- og Veterinaervidenskabelige Forskningsr~td) for financial support to his investigation. The authors are indebted to Mr. Tage Andersen, B.Sc., Adviser to the Association of Milk Recording Societies in the Province of Sealand, and to Professor A. Neimann-S~brensen, Head of the Department of Cattle Experiments at the National Research Institute o f Animal Science, for providing data for this investigation. For preparing some of the data for statistical analysis and for valuable suggestions we should like to thank Mr. Georg Jensen, B.Sc. REFERENCES Ashton, E.D., 1956. Milk and Butterfat Recording--a World Survey. Tech. Commun. No. 3, CAB, Farnham Royal, Bucks, England, 206 pp. Auran, T., 1973. Studies on monthly and cumulative monthly milk records. Acta Agric. Scand., 23: 189--199. Cunningham, E.P and Vial, V.E., 1968. Relative accuracy of different sampling intervals and methods of estimation for lactation milk yield. Ir. J. Agric. Res., 7: 49--60. Dolby, G.R., 1969. A comparison of monthly and bimonthly production records of Queensland dairy cows. Aust. J. Exp. Agric. Anim. Hush., 9: 490--492. Hartmann, 0., 1971. Entwicklungstendenzen der Milchleistungskontrolle mit spezieller Beachtung der zlichterischen Anforderungen. Kommission f~ir Rinderproduktion der Europ. Vereinigung f/ir Tierzucht., 20 pp. Ipsen, E.J. and Kjeldsen, J.O., 1973. Ydelseskontrol med malkekvaeg. Ugeskr. for Agron. og Hort., 2: 605--608. Johansson, I., 1942. Untersuchungen tiber die Methodik der Milchleistungskontrolle. Z.Tierz. Z~Jchtungsbiol., 51: 229--278. Keown, J.F. and Van Vleck, L.D., 1971. Selection on test-day fat percentage and milk production. J. Dairy Sci., 54: 199--203. Madsen, O. and Christensen, L.G., 1974. Accuracy of estimation breeding value using simplified milk recording systems. 1st World Congress on Genetics Applied to Livestock Production, A: 585--591. McDaniel, B.T., 1969. Accuracy of sampling procedures for estimating lactation yields: a review. J. Dairy Sci., 52: 1742--1761. National Danish Committee on Breeding and Management of Cattle, 1971. Summary of Annual Report, 1971, Aarhus, Denmark, 32 pp. Nielsen, E. and Vesth, B., 1971. Afkomspr~bver reed tyre XXV. 387. Beret. fra Fors~bgslab., Copenhagen, 204 pp. Westgaard, P., 1972. Senasta Utvecklingen av Kontrollverksamheten i ~vrigt, Norge. XIII NOK-M~tet, Sverige 66--71.

RF,SUMF, Ipsen, E.J. et Kjeldsen, J.O., 1976. Enqu~te concernant le contrSle laitier et l'utilisation des r~sultats de ce contrSle, en tenant particuli~rement c o m p t e du prolongement des intervalles entre les pes~es du lait et les dosages de la mati~re grasse. L i v e s t . P r o d . Sci., 3 : 155--163 (en anglais). Une enqu~te a }t~ effectu~e ~ propos de l'application de la m~thode traditionelle de con-

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trSle laitier beurrier des vaches laiti~res, en se servant de l'intervalle classique de quatre semaines ou d ' u n mois entre les pes~es et analyses. Les auteurs ont utilis~, d ' u n e part, les donn~es de 1146 vaches test~es pour l'~preuve de la descendance dans les stations danoises, et, d'autre part, celles de 4196 lactations enregistr~es par les Soci~t~s danoises de contrSle laitier. Un allongement de la p~riode de temps entre contrSles n'a augment~ que faiblement l'~cart type de l'erreur de precision. Ces erreurs sont demeur~,es presque sans signification pour des intervalles allant jusqu'~ 12 semaines. Les auteurs en concluent que des contrSles efrectums avec des p~riodicit~s de deux ou de trois mois peuvent aboutir raisonablement l'utilisation des donn~s ainsi obtenues pour le choix des animaux d'~levage. On a examin~ les r~sultats obtenus avec des pes~es de lair effectu~es toutes les 4 ou 8 semaines compl~t~es par des nombres variables d'analyses de mati~re grasse. Avec des intervalles de pes~es de 4 semaines et des analyses de mati~re grasse faites seulement toutes les douze semaines, les r~sultats obtenus ont eu presque la mSme signification que ceux de pes~es avec analyses de mati~re grasse faites ~ intervalles de huit semaines. C'est la p~riode de contr~)le effectu~e pendant la premiere pattie de la lactation qui est responsable, lorsqu'on allonge l'intervalle des pes~es, des erreurs ainsi commises. II est possible de r~duire ces erreurs en effectuant une correction qui tient compte du temps ~coul~ entre le v$1ages et le jour du premier contrSle. Les auteurs ont ~tudi~ la possibilit~ d'utiliser pour la s~lection les dosages de mati~re grasse effectu~es dans les usines laiti~res. En r~duisant le nombre des analyses de mati~re grasse ~ un par animal, on peut, en combinant des r~sultats obtenus par le calcul des moyennes de chaque troupeau provenant des usines laiti~res, obtenir des donn~es suffisamment significatives pour pouvoir servir ~ la s~lection des vaches d ' u n troupeau.

KURZFASSUNG Ipsen, E.J. und Kjeldsen, J.O., 1976. Untersuchungen ~ber die Milchleistungspr~fungen und die Verwendung der Leistungsangaben yon MilchkUhen unter besonderer BerUcksichtigung verlKngerter Intervallezwischen dem Wiegen der Milch und der Fettuntersuchung. Livest. Prod. Sci., 3:155--163 (in Englisch). Die traditionelle Methode der Milch- und Fettproduktion yon Milchk~hen in Intervallen yon einem Monat oder vier Wochen wurde untersucht. Grundlage dieser Arbeit bildete d~nisches Material yon 1146 KUhen, die auf NachkommenprUfungsstationen untersucht wurden sowie 4196 Laktationsleistungen yon d~nischen Organisationen der MilchleistungsprUfung. Eine Vergr~sserung des Zeitabstands zwischen dem Wiegen der Milch und der Fettbestimmung fUhrte zu einem geringen Anstieg der Standardabweichung der Verzerrung. Die Verzerrung war jedoch fur Intervalle his zu 12 Wochen nicht signifikant. Hinsichtlich der Verwendung der Daten f{Ir ztlchterische Zwecke deuten die Ergebnisse darauf hin, dass Laktationsleistungen, die aufgrund zweimonatiger oder dreimonatiger Pr~fungen errechnet werden, vernUnftige Alternativen zur traditionellen, monatlichen Pr~fung bieten. Es wurden FKIle untersucht, bei denen die WKgungen der Milch auf einen Intervall von 4 oder 8 Wochen festgesetzt wurden und die Anzahl der Fettuntersuchungen wKhrend der Laktation variiert. Die Ergebnisse deuten an, dass das Wiegen der Milch im Abstand yon 4 Wochen und die Durchftlhrung der FettprUfung im Ahstand yon 12 Wochen etwa die gleiche Signifikanz der Leistungsergebnisse erbringt wie die Pr~ifung sowohl auf Milch als auch auf Fett im Abstand yon 8 Wochen. Die PrUfung im ersten Tell der Laktation kann einen grossen Teil des Fehlers der Laktationsleistung verursachen. Es ist m~glich, die Standardahweichung der Verzerrung dadurch zu vermindern, dass eine Korrektur auf die LKnge des Intervalls zwischen dem Kalbetermin und der ersten Pr~]fung erfolgt. Es wurden M~glichkeiten untersucht, Fettuntersuchungen der Molkereien zu verwenden. Selbst eine Reduzierung der Fettuntersuchung auf eine PrUfung pro Kuh in jeder Laktation in Verbindung mit dem Herdendurchschnitt des Fettgehalts der Molkerei kann eine tragbare Signifikanz der Daten der Organisationen der MilchleistungsprUfung ergeben.