TITLE:
Effect of Age at First Calving on First Lactation Milk Yield in Holstein Cows from Costa Rican Specialized Dairy Herds
AUTHORS:
Mauren Salazar-Carranza, Gloriana Castillo-Badilla, Jaime Murillo-Herrera, Frank Hueckmann-Voss, Juan José Romero-Zúñiga
KEYWORDS:
Tropics, Holstein, Production, Reproduction, Information Systems
JOURNAL NAME:
Open Journal of Veterinary Medicine,
Vol.4 No.9,
September
10,
2014
ABSTRACT: In order to determine the effect of age at
first calving (AFC) at 305-d milk yield, a historical prospective longitudinal
study of 46,029 pure specialized dairy Costa Rican Holstein animals was carried
out between 2000 and 2010. Data on purebred specialized dairy Holstein cows
enrolled in the program VAMPP Bovino 3.0 were included. Information was
analyzed by using descriptive statistics and mixed linear models. The effect of
the AFC was adjusted to the ecological zone, season of birth, year of birth,
inbreeding index, and type of parturition and parity number of the dam at
birth. The average AFC for the animals that were part of the study was 30.7 mo
(SD: 6.8, 95% CI: 30.6 - 30.7). The average total milk production in the first
lactation was5188.0 kg(95% CI: 5153.4 - 5223.2), whereas the 305-d corrected milk yield resulted in5288 kg(95% CI: 5253.7 - 5323.2). Cows
with AFC less than 26 mo and between 26.0 and 33.6 mo, produced -354.8 kg/305-d (P