A small‐plot experiment was conducted in south‐west Ireland to investigate (i) the effects of pre‐closing regrowth interval and closing date on dry‐matter (DM) yield and sward structural and composition characteristics, during the autumn–winter and spring opening periods, and (ii) subsequent carryover effects. The study used a randomized block design with a factorial arrangement of treatments (4 closing dates × 2 opening dates) with a split plot (two pre‐closing regrowth intervals). The long pre‐closing (LPC) interval began on 9 August, and the short pre‐closing interval (SPC) started on 15 September. The autumn closing dates were as follows: 1 October (CD1), 15 October (CD2), 1 November (CD3) and 14 November (CD4). Plots were defoliated again on 1 February (EOD) or 1 March (LOD). On the LPC treatment, herbage yield increased from CD1 (2463 kg DM ha−1) to CD3 (3185 kg DM ha−1). On the SPC treatment, herbage yield was similar for CD3 and CD4, indicating a ceiling in herbage accumulation. For each 1‐d delay in closing date between CD1 and CD4, the opening herbage yield was reduced by 10 kg DM ha−1. Herbage quality decreased as the closing date was delayed; DMD and CP decreased by 0·06 and 12 g kg DM−1, respectively, between CD1 and CD4. The EOD resulted in increased leaf and decreased dead proportions over the LOD treatments. A balance between autumn CD and spring OD needs to be achieved to ensure a sufficient supply of high‐quality grass in spring.

The objective of this study was to compare the milk production, dry matter intake, and energy partitioning of autumn-calving Holstein-Friesian cows offered a high or low amount of concentrate using 1 of 2 feeding strategies. One hundred and eight autumn-calving Holstein-Friesian cows were blocked based on milk production data from wk 3 and 4 of lactation, and were divided into low-, medium-, and high-milk yield subgroups. Cows were randomly assigned to 1 of 4 treatments (n=27) in a 2×2 factorial design. Treatment factors were concentrate feeding amount, high concentrate=7.0 (Hi) or low concentrate=4.0kg of DM/cow per day (Lo), and concentrate feeding strategy, flat rate (FR) or group-fed to yield (GFY). In the GFY treatments, cows were allocated concentrate based on their milk yield in the third and fourth weeks of lactation. The lowest-yielding cows (n=9) received 5.3 and 2.3kg of DM of concentrate on the Hi and Lo treatments respectively, the highest-yielding cows (n=9) received 8.7 and 5.7kg of DM of concentrate on the Hi and Lo treatments respectively, and the average yield cows received the same amount of concentrate as the corresponding FR group (i.e., 7.0 and 4.0kg of DM of concentrate on the Hi and Lo treatments, respectively). The proportion of forage in the diet was 63% of total dry matter intake (TDMI) for the Hi treatment and 75% of TDMI for the Lo treatment. No significant interaction was noted between concentrate feeding amount and concentrate feeding strategy for dry matter intake or milk yield. Cows on the Hi treatment had a higher TDMI (18.7±0.36kg/cow per day) compared with cows on the Lo treatment (15.8±0.36kg/cow per day). The milk yield of cows offered the Hi treatment was 1.3kg/cow per day higher than the milk yield of cows on the Lo treatment (23.8±0.31kg/cow per day). Milk solids yield was 0.10kg/cow per day higher on the Hi treatment than on the Lo treatment (1.83±0.03kg of DM/cow per day). Cows on the Hi treatment had an estimated net energy demand of 18.0±0.38 UFL (unité fourragère lait)/cow per day and a net energy intake of 17.6±0.33 UFL/cow per day during the experimental period. Cows on the Lo treatment had an energy demand of 16.8±0.38 UFL/cow per day and an energy intake of 14.9±0.33 UFL/cow per day. No significant difference in TDMI, milk yield, milk solids yield, or energy balance was observed between the FR and GFY treatments. By increasing the total amount of concentrate offered, cows had higher TDMI and energy intake, which resulted in increased milk production and reduced negative energy balance and body condition score loss.

The objective of this experiment was to compare the effects of two concentrate feeding strategies offered with a grass silage and maize silage diet on the dry matter (DM) intake, milk production (MP) and estimated energy balance of autumn calved dairy cows. Over a 2-year period, 180 autumn calving Holstein Friesian cows were examined. Within year, cows were blocked into three MP sub-groups (n = 9) (high (HMP), medium (MMP) and low (LMP)) based on the average MP data from weeks 3 and 4 of lactation. Within a block cows were randomly assigned to one of two treatments (n = 54), flat rate (FR) concentrate feeding or feed to yield (FY) based on MP sub-group. Cows on the FR treatment were offered a fixed rate of concentrate (5.5 kg DM/cow per day) irrespective of MP sub-group. In the FY treatment HMP, MMP and LMP cows were allocated 7.3, 5.5 and 3.7 kg DM of concentrate, respectively. The mean concentrate offered to the FR and FY treatments was the same. On the FR treatment there was no significant difference in total dry matter intake (TDMI, 17.3 kg) between MP sub-groups. In the FY treatment, however, the TDMI of HMP-FY was 2.2 kg greater than MMP-FY, and 4.5 kg greater than LMP-FY (15.2 kg DM). The milk yield of LMP-FR was 3.5 kg less than the mean of the HMP-FR and MMP-FR treatments (24.5 kg). The milk yield of the HMP-FY treatment was 3.6 and 7.9 kg greater than the MMP-FY and LMP-FY treatments, respectively. The difference in MP between the HMP sub-groups was 2.6 kg, which translates to a response of 1.4 kg of milk per additional 1 kg of concentrate offered. There was no significant difference in MP between the two LMP sub-groups; however, MP increased 0.8 kg per additional 1 kg of concentrate offered between cows on the LMP-FR and LMP-FY treatments. The estimated energy balance was positive for cows on the LMP-FR treatment, but negative for cows on the other treatments. The experiment highlights the variation within a herd in MP response to concentrate, as cows with a lower MP potential are less responsive to additional energy input than cows with a greater MP potential. Cows with a greater MP capacity did not substitute additional concentrate for the basal forage, which indicates an additional demand for energy based on ability of individual cows to produce milk.