Differences in lactation curve parameters and milk yield responses between artificially induced and naturally calved cows milked in an automatic milking system

Despite advances in artificial induction of lactation (AIL) protocols, they do not perfectly mimic the hormonal patterns of natural pregnancy. Recent studies show improved milk yield (MY) responses; however, comparisons of lactation curve parameters between AIL and naturally calved (NC) cows often do not extend beyond 305 days in milk (DIM). Thus, this study aimed to compare MY responses and lactation curve parameters between AIL and NC cows milked in an automated milking system (AMS). Data from 38 Holstein cows (19 AIL and 19 NC) were analyzed, focusing on the 305 DIM period. Wood’s lactation curve model was used to analyze individual data, followed by analysis of variance and orthogonal contrasts for mean comparisons. AIL cows had lower initial MY (8.2 L) and peak MY (31.3 L) compared to NC cows (17.3 L and 40.5 L, respectively). Persistency was similar between AIL (0.0039) and NC cows (0.0034). AIL cows produced 22% less milk overall (8239 L) compared to NC cows (10,521 L), whereas DIM peak did not differ. In practice, even though AIL cows yield about 80% of the milk produced by NC cows during their lactation, inducing lactation is justifiable in an AMS, as it enables substantial milk yields by AIL cows.