Omission of dry period and effects on the subsequent lactation curve and on milk quality around calving in Italian Holstein cows

Abstract

The aim of this study was to investigate the effect of dry period omission on subsequent milk production over a whole lactation and the effect on milk quality around calving. Seventeen Italian Friesian cows, homogeneous for milk yield and parity, were managed either with a traditional dry-off period of 55 d (CTR group; n=8) or continuously milked up to parturition (CON group; n=9). Milk yield was recorded daily from 75±7 d before expected calving date to the end of subsequent lactation to fit the lactation curve. Before parturition milk samples were collected at −70 d, −60 d, and −55 d for CTR and CON groups and at −40 d, −30 d, and −7 d for CON cows. After calving, six milk samples were taken from 1 d to 90 d from both groups and analyzed for fat, protein, lactose, MUN and somatic cells. Body weight (BW) and body condition (BCS) were obtained 7 times from −55 d before expected calving to 90 d after calving. The omission of the dry period modified the shape of lactation in CON cows that reached the peak 10 d earlier and producing −5.5 kg/d than CTR. Over a 305 d period, the milk yield reduction was of −2241 kg in CON group. The higher amount of milk produced before calving, i.e., 560 kg of milk in 52 d of mean pre-partum period, did not compensate the milk yield reduction after a continuous lactation. Milk quality was unaffected by the omission of dry period after calving, and animals in both lactation groups showed a similar decreasing trends over time for fat and protein, and increasing trends for lactose and MUN. Somatic cell score remained greater (4.54 vs 3.40) in CON than in CTR cows after calving.No different BW or BCS changes were observed for both groups after calving. We conclude that despite the absence of great differences in milk quality, the complete omission of the dry period in cows reduce significantly the milk yield, suggesting no economical benefit from this management strategy.