Studies on Monthly and Cumulative Monthly Milk Yield Records

Data were obtained from 17,968 records from 2,130 first lactations of Holstein cows calving between 1988 and 1991. The subjects were daughters of 136 sires monitored by Brazilian Breeders Association, Animal Science Institute, Department of Agriculture, a branch of the State of São Paulo. Data were divided into 10 subsets based on the number of days in milk yield. Test day milk yields (M1 to M10) and 305-day milk yield (M305) were the traits studied. These traits were adjusted for several environmental effects: class of cow age at calving, interval from calving to first test day, and herd-year-season. Restricted maximum likelihood estimates of (co)variance components were obtained from one and two-traits analysis under a sire model. Estimates of heritabilities for M ranged from 0.04 to 0.32. The highest values were found in the second half of lactation (M5 to M7). Heritability estimate for M305 was 0.32. Genetic correlations between individual test days and M305 ranged from 0.78 to 1.00. Results suggested that test day milk yields, mainly in mid-lactation, can be used instead of 305-day milk yield in genetic evaluations, because estimates of these two-trait heritabilities are nearly alike. Moreover, early selection can reduce generation intervals.
No presente estudo foram utilizados 17.968 registros de produção de leite, referentes a 2130 primeiras lactações de vacas da raça Holandesa, paridas nos anos de 1988 a 1991, filhas de 136 touros e controladas pela Associação Brasileira de Criadores (ABC). Os dados foram distribuídos em dez sub-arquivos de acordo com o número do controle (M1 a M10). As características estudadas foram: produção de leite no dia do controle (M) e produção aos 305 dias de lactação (M305), as quais foram ajustadas para os seguintes fatores de variação: idade da vaca ao parto em classes, intervalo parto-primeiro controle e subclasses de rebanho-ano-estação de parto. Os componentes de (co)variância foram obtidos a partir de análises com duas características utilizando-se o método REML, sob um modelo de touro. As estimativas de herdabilidade para as M variaram de 0,04 a 0,32 sendo os maiores valores encontrados na segunda fase da lactação (M5 a M7), enquanto que para a M305 este valor foi 0,32. As correlações genéticas entre as M e a M305 variaram de 0,78 a 1,00. Os resultados sugerem que as M podem ser utilizadas em substituição à M305 nas avaliações genéticas dos animais, visto que as herdabilidades no meio da lactação foram semelhantes à encontrada para a M305. Além disso, a seleção antecipada pode levar a uma redução no intervalo de gerações

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“…Selection of sires and dams also can affect estimates. Auran (1976) reported slightly larger estimates from data where cows were not culled.…”

Section: Resultsmentioning

confidence: 88%

“…Genetic parameters for test day yields have been estimated by several authors (Van Vleck and Henderson, 1961;Keown and Van Vleck, 1971;Auran, 1976;Danell, 1982, Swalve, 1995b, Gadini, 1997. According to these authors, selection based on some test day records is as efficient as on all.…”

Section: Introductionmentioning

confidence: 99%

Genetic parameters of test day milk yields of Holstein cows

1999

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“…Determination of the appropriate factor is based on age of cow at calving (within lactation number), season of freshening, and n. For identification, this method is estimation by cumulative ratio factor (CRF). Recently, a method extending incomplete lactation records from information on last test day has been studied (1,3,5). The prediction of 305-day equivalent is of the form:…”

Section: Methodsmentioning

confidence: 99%

“…Until recently incomplete records in the Northeast were extended to 305-day equivalents by the following formula: ^ Yms = Factor X Yn [1] where Yn is the cumulative production to day n, and ~rms is estimated production for 305 484 days. Determination of the appropriate factor is based on age of cow at calving (within lactation number), season of freshening, and n. For identification, this method is estimation by cumulative ratio factor (CRF).…”

Section: Methodsmentioning

confidence: 99%

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Sire Evaluation by Only Extended Partial Milk and Fat Records

Vleck

1981

Journal of Dairy Science

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The standard of comparison for dairy production records is the 305-day lactation, and much research has been directed to estimating 305-day milk and fat records from incomplete or in-progress records. This study was to determine the effect of several methods of extending incomplete records on sire evaluation. Complete 305-day milk and fat records of first lactations of 73,724 daughters of 1,362 artificial insemination Holstein sires processed at the New York Dairy Records Processing Laboratory were used to compute sire proofs for yield of milk and fat. Partial records of two lengths (60 to 80 days and 130 to 160 days) on the same daughters were extended by three methods, and sire proofs were computed from these six sets of extended records. Correlations between sire proofs with complete records only and sire proofs with only extended incomplete records were .93 or .94 (for milk proofs) when the length of the part record was between 130 and 160 days, regardless of the method of extension. Correlations were less (.66 to .81 for milk proofs), as expected, when the length of the part record was between 60 and 80 days.

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Phenotypic and genetic parameters of part lactation milk and fat records in polish lowland cattle

Zarnecki¹,

Ondrusz²

1979

Livestock Production Science

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Studies on Monthly and Cumulative Monthly Milk Yield Records

Cited by 19 publications

References 13 publications

Genetic parameters of test day milk yields of Holstein cows

Genetic parameters of test day milk yields of Holstein cows

Sire Evaluation by Only Extended Partial Milk and Fat Records

Phenotypic and genetic parameters of part lactation milk and fat records in polish lowland cattle

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