Effects of concentrate supplementation strategies during the transition period and milking frequency in early lactation on seasonal winter-calving organic dairy cows

At the start of lactation, a severe energy deficiency can have negative impacts on dairy cows' performance and health. The objective of this 3 x 2 factorial study was to compare the effects of three concentrate (C) build-up strategies during transition period (C-21; C1; C+21) and two milking frequencies (M) during 1st week of lactation (once vs. twice-daily milking; M1 vs. M2) on feed intake, milk yield, energy supply, body weight, body condition score, metabolic status, health, and fertility parameters. During the three years of study, data were collected for 66 transition periods (N) from 37 individual animals (21 Holstein Friesian (HF) and 16 Austrian dual purpose Simmental animals (SI); 8 primiparous cows in each breed). Four weeks (1st Nov., +/- 57.2 days) before expected calving date the animals were allocated randomly (balanced for parity, breed, calving date, insemination index in the previous breeding season and genetic merit) to one of three concentrate supplementation strategies (C) during the transition period (C-21; C+1; C+21; N=22 group 1). Within these three C groups, half of the cows were either milked once (M1) or twice (M2) during 1st week of lactation, and from 8 DIM onwards all cows were milked twice a day. All animals were offered a high-quality forage basal diet comprising hay and grass silage from four weeks before expected calving date until 98th days in milk (DIM). In group C-21 the concentrate supplementation started 21 days (-21 days) before expected calving date and was increased (DIM -21 to -15) from 1.8 kg dry matter (DM) to 2.6 kg DM (DIM -14 to 1) until parturition; during the first 14 DIM concentrate supplementation was daily increased by 0.26 kg DM cattle(-1) from 2.6 to 5.9 kg DM and from 15 DIM onwards concentrate supply depended on actual milk yield of the individual cow. In group C+1 no concentrate was fed pre-partum, and from lactation day 1 onwards the same concentrate building up strategy and allocation was made as described for group C-21. In group C+21 the concentrate supplementation did not start until 21 DIM and from this point on the same concentrate build-upstrategy was implemented as described for group C+1, but with each phase delayed by 21 days. Pre-calving feed and net energy intake (NEL) as well as net energy balance (EB) was significantly higher in C-21 compared to groups C+1 and C+21. During the first seven weeks of lactation C+21 groups (P<0.001) showed the significant lowest NEL intake, and for energy-corrected-milk (ECM) yield a tendency (P=0.067) for an interaction between C and M was found. In C-21 and C+1, cows in M1 had significantly lower ECM yields compared to cows in groups M2 (C-21: 22.5 and 25.0 kg/d; C+1: 20.3 and 26.1 kg/d in M1 und M2, respectively); in C+21, ECM yield differed only numerically between M1 (22.1 kg/d) and M2 (23.9 kg/d). Cows in M1 showed in all C groups higher milk protein contents and higher somatic cell counts compared to M2; no significant C x M interactions were found. Within all concentrate supplementation strategies, cows in M1 showed higher EB during lactation weeks 1 to 7, within C groups the differences between M1 and M2 were significant in C-21 (C-21M1 +4.8 and -4.2 MJ NEL/d) and C+1 (C+1M1 +7.8 and -4.7 MJ NEL/d), in C+21 groups only numerical differences were found (C+21M1 -2.1 and C+21M2 -8.1 MJ NEL/d). During the first six weeks of lactation, the lowest blood glucose concentrations were detected in C+21 (2.80 in C+21M1 and 2.68 mmol/l in C+21M2). For nonesterified fatty acids concentration (NEFA) a significant interaction between C and M treatment was found (P-CxM<0.001), within C-21 and C+1 groups cows in M1 showed significantly lower NEFA concentrations compared to M2 groups, in C+21 NEFA concentration were higher in M1. The significant highest beta-hydroxybutyric acid concentrations (BHBA) were found in C+21 groups with 0.80 and 0.92 mmol/l in M1 and M2, respectively, between C-21 and C+1 no significant BHBA concentration differences were found in both milking groups. Cows in M1 require fewer veterinary treatments, were significantly earlier inseminated, but the first service conception rate and the total number of services per conception varied not significantly between groups. In conclusion, a delayed concentrate supplementation to 21 DIM (C+21) reduced energy intake and showed negative effects on EB and metabolic parameters. Once a day milking up to 7 DIM (M1) had no effect on energy intake, reduced ECM yield and improved EB and metabolic parameters in the first seven weeks of lactation. Also M1 reduced total number of veterinary treatments, led to earlier inseminations, had no effects on the other measured reproduction parameter, and increased somatic cell counts (SCC).