Effect of concentrate escalation postpartum on the shape of the lactation curve and health parameters of Norwegian dairy cattle

Afield trial testing four different concentrate escalation strategies postpartum, 0.3 kg/d, 0.5 kg/d, 0.7 kg/d, and 1.0 kg/d (concentrate amounts measured as fresh weight) was conducted in 25 Norwegian dairy herds, including 811 lactations, in the period from 1st September 2008 until 1st September 2009. Inclusion criteria were: herd size above 30 dairy cows, daily milk yield recording, unchanged production system for the past two years, and membership of the Norwegian Dairy Herd Recording System. The study population was a convenience sample of herds that matched the inclusion criteria and that contacted the project group after the trial protocol was published in the Norwegian Red Breed magazine - 'Buskap'. During the trial period, milk yield was recorded daily and body condition score was recorded once in the dry period, and every second month thereafter (total of 2-3 scores for each lactation). Production and reproduction data for the same period were obtained from the national database made available by the Norwegian Dairy Herd Recording System. Lactation curve parameters were estimated using the Wood's function for each lactation separately. The associations between lactation curve parameters, as well as the calculated 90-d milk yield, and the variables: concentrate escalation speed, parity group, maximum level of concentrates, body condition score in dry period, occurrence of mastitis cases, and somatic cell count early in lactation, were determined using a PROC MIXED analysis with a random herd statement at lactation level. The 90-d concentrates provided were estimated and their association with concentrate escalation speed, starting level of concentrates, and maximum level of concentrates were found using the same type of analyses. Differences in milk fat percentage, days open, and disease incidence between concentrate escalation strategies within parity were compared using 95% confidence limits. A significant increase in Parameter A (starting level of milk yield) occurred when a 1.0 kg/d escalation strategy was used compared with 0.3 kg/d, across all parities. Third or later parity lactation had a significantly lower Parameter B (rate of increase and peak milk yield) and C (persistency of milk yield) when using the 1.0 kg/d escalation compared with the 0.3 kg/d escalation. The 90-d milk yield did not differ significantly between concentrate escalation strategies tested. Thus, the most efficient use of concentrates was escalating with 0.3 kg/d postpartum, as evaluated by kg concentrates given per 100 kg milk produced. (C) 2011 Elsevier B.V. All rights reserved.