Selection Practiced Among Dairy Cows. II. Total Production Over a Sequence of Lactations
نویسندگان
چکیده
منابع مشابه
Modeling extended lactations of dairy cows.
Nine mathematical models were compared for their ability to predict daily milk yields (n = 294,986) in standard 305-d and extended lactations of dairy cows of Costa Rica. Lactations were classified by parity (first and later), lactation length (9 to 10, 11 to 12, 13 to 14, 15 to 16, and 16 to 17 mo), and calving to conception interval (1 to 2, 3 to 4, 5 to 6, 7 to 8, and 9 to 10 mo). Of the nin...
متن کاملSelection of Dairy Cows for Economic Merit
Selection of dairy cows for economie merit requires the use of a model for genetic merit that involves the cross-product of the genetic values for milk and milk fa t percentage. A linear and a quadratic index are described as procedures for selection of cows, the linear index being blp.~ + bzp, and the quadratic index being blp,~ + b~_pt + b~p,n 2 + b~p, ~ + b~p.,pt where p~ and pt are the phen...
متن کاملModeling daily energy balance of dairy cows in the first three lactations.
Daily energy balance was calculated for 111 Holstein cows in their first 3 lactations, based on combinations of smoothed preadjusted phenotypic records for milk yield, feed intake, live weight, and body condition score. Two energy balance traits were defined: one based on milk yield and feed intake (EB1) and the other on live weight and body condition score change (EB2). Bessel functions (BF), ...
متن کاملEnergy balance profiles for the first three lactations of dairy cows estimated using random regression.
Daily animal solutions were predicted using random regression analysis for feed intake, milk yield, live weight, and condition score recorded on 189 cows at the Langhill Dairy Cattle Research Centre. All cows had three successive lactations. Energy balance for days 1 to 305 of each of the three lactations was calculated both from daily measures of feed intake and milk output and from weekly mea...
متن کاملGenetic profile of total body energy content of Holstein cows in the first three lactations.
Weekly total body energy content (TBEC) was calculated for 444 Holstein cows in their first 3 lactations. These calculations were based on body lipid and protein changes predicted from weekly changes in body condition score and live weight of each cow. In first lactation, cows lost TBEC during the initial 8 wk, regained it by wk 22, and continued to build up their reserves until wk 37. Cows sta...
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ژورنال
عنوان ژورنال: Journal of Dairy Science
سال: 1966
ISSN: 0022-0302
DOI: 10.3168/jds.s0022-0302(66)88106-7