Associations between age at first calving and subsequent performance in Irish spring calving Holstein-Friesian dairy cows.

摘要: Abstract Little is known about the association between age at first calving and subsequent performance in seasonal dairy production systems where grazed grass constitutes majority of basal diet. The objective this study was to quantify, using Irish national database, milk production, performance, fertility survival grazing, seasonal-calving Holstein–Friesian cows. Median from a population 196,120 animals varied 751 764 days across years 2000 2006, inclusive while ranged 660 days 1156 days. A frequency distribution revealed large peak coinciding with approximately 24 smaller 36 months age. Associations were undertaken on 6338 50,786 animals. First lactation 305-day yield milk, fat protein decreased almost linearly by 55.5 kg, 0.6 kg 2.3 kg, respectively for each month earlier calving. Although heifers younger time had greater likelihood requiring some assistance there no risk severe Age associated second, third, fourth fifth parity sixth parity; 24 months generally greatest odds older parities 3 years having lower odds.