Month, Year, and Herd Effects on Age Adjustment of First Lactation Milk Yield

Lee, A.J.

doi:10.3168/jds.s0022-0302(74)84887-3

Cited by 6 publications

(1 citation statement)

References 8 publications

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“…About 40% of variation comes from seasonal calving effects (Lee, 1973;Mao et al, 1973;Lofgren et al, 1985). To establish a common basis, the data were adjusted according to month of calving.…”

Section: Data Sourcesmentioning

confidence: 99%

Study of the Lactation Curve in Dairy Cattle on Farms in Central Mexico

Val-Arreola

Kebreab

Dijkstra

et al. 2004

Journal of Dairy Science

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Accurate knowledge of lactation curves has an important relevance to management and research of dairy production systems. A number of equations have been proposed to describe the lactation curve, the most widely applied being the gamma equation. The objective of this work was to compare and evaluate candidate functions for their predictive ability in describing lactation curves from central Mexican dairy cows reared under 2 contrasting management systems. Five equations were considered: Gaines (exponential decay), Wood (gamma equation), Rook (Michaelis-Menten xexponential), and 2 more mechanistic ones (Dijkstra and Pollott). A database consisting of 701 and 1283 records of cows in small-scale and intensive systems, respectively, was used in the analysis. Before analysis, the database was divided into 6 groups representing first, second, and third and higher parity cows in both systems. In all cases except second and above parity cows in small-scale systems, all models improved on the Gaines equation. The Wood equation explained much of the variation, but its parameters do not have direct biological interpretation. Although the Rook equation fitted the data well, some of the parameter estimates were not significant. The Dijkstra equation consistently gave better predictions, and its parameters were usually statistically significant and lend themselves to physiological interpretation. As such, the differences between systems and parity could be explained due to variations in theoretical initial milk production at parturition, specific rates of secretory cell proliferation and death, and rate of decay, all of which are parameters in the model. The Pollott equation, although containing the most biology, was found to be over-parameterized and resulted in nonsignificant parameter estimates. For central Mexican dairy cows, the Dijkstra equation was the best option to use in describing the lactation curve.

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Section: Data Sourcesmentioning

confidence: 99%

Study of the Lactation Curve in Dairy Cattle on Farms in Central Mexico

Val-Arreola

Kebreab

Dijkstra

et al. 2004

Journal of Dairy Science

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Seasonal grouping in a herd-year-season model of sire evaluation

Chauhan

Hill

1986

Anim. Sci.

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Analyses of variance were conducted using two separate random sets of data (25 158 and 24 084 records) on first-lactation, milk-production records of progeny of 69 British Friesian-Holstein proven sires in order to examine the criteria of seasonal grouping for a sire-evaluation model fitting herd-year-season as a fixed effect. Five different seasonal groupings were chosen each comprising two or three seasons with equal or unequal number of months and with different trends in production within season.The smallest herd-year × month of calving within-season interaction, smallest residual variance, largest effective number of daughters and smallest among-months, within-season variation were considered to be the appropriate criteria of seasonal grouping. None of the groupings examined satisfied all criteria. However, a small herd-year × month within season interaction and all small within-season variation would be desirable if milk records were pre-corrected for the effect of month of calving in sire evaluation, and the effective number of daughters should be large. Given this the grouping currently used in Britain (three seasons: December to March, April to July and August to November) was considered to be appropriate, although a grouping with two seasons: February to July and August to January gave similar results. The regional differences in production were observed to be large, but the region × month-of-calving interaction was small.

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Studies on Lactation Yield and Individual Test-day Yields of Swedish Dairy Cows

Danell

1982

Acta Agriculturae Scandinavica

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Month, Year, and Herd Effects on Age Adjustment of First Lactation Milk Yield

Cited by 6 publications

References 8 publications

Study of the Lactation Curve in Dairy Cattle on Farms in Central Mexico

Study of the Lactation Curve in Dairy Cattle on Farms in Central Mexico

Seasonal grouping in a herd-year-season model of sire evaluation

Studies on Lactation Yield and Individual Test-day Yields of Swedish Dairy Cows

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