Abstract
Abstract. The aims of this study were to estimate the effects of twinning and stillbirth on the lactation curve traits in Holstein cows in Iran. Data from March 2000 to April 2009 comprising of 862 109 test-day milk records corresponding to 115 805 lactations of 58 756 cows in 27 herds were used. The lowest peak and total lactation yield but the highest days in milk (DIM) until peak yield, persistency and cumulative milk yield from calving up to DIM at peak production were found during the first lactation (P<0.05). Consequential effect of stillbirth and twinning on lactation curve traits, except for the factors associated with the downward slopes of the curve, were significant (P<0.05). Stillbirth affected the 100-d, 200-d and 305-d milk yields. Cows with stillborn calves had longer days to peak yield and higher persistency, but lower peak yield, than those with live calves (P<0.05). Number of days to peak yield, the persistency and total lactation yield from calving up to peak of lactation were higher for twin birth than for single birth calvings (P<0.05). The estimated correlation between peak yield and lactation yield was high (68%) indicating that peak yield is very important in determining the lactation yield.
Highlights
Stillbirth, defined as the death of a calf just prior to, during, or within 24 to 48 h of parturition, is a major issue in dairy cow management
Variability in the quantity and quality of ration as well as physiological and health problems related to harsh environmental conditions may lead to atypical lactation curves (Rekik & Gara 2004)
Stillbirth and twinning significantly affected lactation curve traits except for the parameter associated with the downward slope of the curve (c)
Summary
Stillbirth, defined as the death of a calf just prior to, during, or within 24 to 48 h of parturition, is a major issue in dairy cow management. Increased frequency of stillbirth during last decades has been reported in several countries (Meyer et al 2000, Hansen et al 2004, Berry et al 2007, Bicalho et al 2008). There is no scientific report on the effects of twinning and stillbirth on the shape of lactation curve. The objectives of this study were to estimate the effects of stillbirth and twinning on the shape of lactation curve, and on partial and 305-d lactation performance in Holstein dairy cows in Iran.
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