The potential of a short or no dry period in dairy farming: effects on udder health, metabolic health, and lactation curve characteristics

Shortening and omitting the dry period in dairy cows improves the energy balance, metabolic status and fertility in the subsequent lactation, compared with a conventional dry period of 6 to 8 weeks^(1-3) . Improvement of the energy balance after a short or no dry period is due to a reduction in milk yield in the subsequent lactation⁽¹⁾ , which is only partially compensated by additional milk in the precalving period⁽²⁾ . In addition, cows without a DP not only produce less milk, but also can have an increased somatic cell count in the subsequent lactation⁽³⁾  and an increased risk of over-fattening in mid and late lactation⁽⁴⁾ . It can be hypothesized that a reduced dietary energy level and a more lipogenic, compared with a glucogenic ration can improve lactation persistency^{(5, 6)} , and herewith increase total milk yield and reduce the chance for fattening in mid and late lactation. Moreover, to our knowledge, all studies on the effect of dry period length (DP) on udder health were carried out using dry cow antibiotics at drying off⁽³⁾ . Preventive use of dry cow antibiotics is not allowed in several European countries among which the Netherlands⁽⁷⁾ . It can be hypothesized that the increased SCC due to omission of the dry period is due to omission of the dry cow antibiotics, and not due to omission of the dry period. The aim of the current project was to optimize a management system using a shortened or omitted dry period.

Holstein-Friesian cows (N = 128) were blocked for parity, expected milk yield and SCC in the previous lactation. At drying off cows were assigned randomly to 3 treatments: 1) a 30-d DP and a STD dietary energy level [30-d DP(STD)] (n = 44), 2) a 0-d DP with the same STD dietary energy level as cows with a 30-d DP and fed a G or L ration [0-d DP(STD)] (n = 44), 3) a 0-d DP with a LOW concentrate level and fed a G or L ration [0-d DP(LOW)] (n = 42). At week 7 in lactation, cows within each transition treatment were randomly assigned to 1 of the 2 lactation diets: glucogenic or a lipogenic diet. Lactating cows prepartum (0-d DP) and up to 7 weeks in lactation received a lactation ration that mainly consisted of grass silage and corn silage (6.4 MJ net energy NE_L /kg DM). The glucogenic ration consisted mainly of corn silage and grass silage (6.5 MJ NE_L /kg DM). The lipogenic ration consisted mainly of grass silage and sugar beet pulp (6.5 MJ NE_L /kg DM). The glucogenic and lipogenic ration with a LOW dietary energy level contained more wheat straw than the rations with a STD energy level (6.1 and 6.3 MJ NE_L /kg DM, respectively). Lactating cows received 1 kg/d of standard concentrate in the milking parlor. Experimental concentrate increased between 4 DIM and 28 DIM to 8.5 kg/day for cows receiving STD energy level (30-d DP(STD) and 0-d DP(STD)), and between 4 DIM and 22 DIM to 6.7 kg/day for cows receiving the LOW energy level (0-d DP(LOW)). The experimental concentrate decreased stepwise between 92 DIM and 211 DIM to 0.0 kg/day. Cows were monitored from 5 weeks prepartum till 44 weeks postpartum. [...]