Intake profile, milk production and energy balance of early lactation spring calving Holstein Friesian and Jersey x Holstein Friesian dairy cows in high utilisation pasture-based systems.

Early lactation is a critical period for dairy cows as energy requirements rapidly increase with the onset of lactation, however, early lactation dry matter intakes (DMI) in pasture-based systems are under-measured. The objectives of this study were 1) to measure and profile total DMI (TDMI) and animal performance of dairy cows during early lactation in a pasture-based system 2) to investigate early lactation energy balance in pasture-based systems and 3) to examine production efficiencies including TDMI and milk solids production per 100 kg bodyweight. Eighty spring-calving dairy cows were allocated to a grazing group as they calved over a 2 year period (2021 and 2022). Cows were offered a daily herbage allowance to achieve a post-grazing sward height of 4 cm with silage supplementation when necessary due to inclement weather. Total DMI was measured using the n-alkane technique over a 12 week period from 1st of February to the 23rd of April. Total DMI and daily milk yield were significantly affected by parity with both variables being greatest for third parity animals (17.7 kg DM and 26.3 kg/cow/day, respectively), lowest for first parity (13.2 kg DM and 19.6 kg/cow/day, respectively) and intermediate for second parity animals (16.8 kg DM and 24.1 kg/cow/day, respectively). Peak TDMI was reached on wk 10 for first parity animals (14.6 kg DM), wk 11 for second parity animals (19.3 kg DM) and wk 12 for third parity animals (19.9 kg DM). Parity also had a significant effect on UFL (feed units for milk) feed balance as first parity animals experienced a greater degree of negative energy balance (-3.2 UFL) compared with second and third parity animals (-2.3 UFL). Breed and parity had an effect on production efficiencies during the first 12 weeks of lactation as Jersey x Holstein Friesian cows had greater TDMI/100 kg bodyweight and milk solids/100 kg bodyweight compared with Holstein Friesian cows.

The effect of concentrate supplementation type on milk production, dry matter intake, rumen fermentation, and nitrogen excretion in late-lactation, spring-calving grazing dairy cows.

In Ireland, milk is primarily produced using a spring-calving grass-based system, with the use of concentrate supplementation mainly when pasture availability and quality are reduced. In the autumn, when cows are in late lactation, reduced pasture productivity results in reduced milk yield and altered milk composition. Nitrogen utilization efficiency also reduces as lactation progresses. Concentrate supplementation has been found to increase milk production and reduce nitrogen (N) excretion, as high-N grass is usually replaced by a lower-N supplement; however, there is a paucity of information with regard to the optimum type of supplementation in late lactation. Therefore, the objective of this research is to investigate the effect of different concentrate supplementation types, based on barley or maize, on milk production, dry matter intake (DMI), rumen fermentation, and N excretion in late-lactation, spring-calving, grazing dairy cows. Thirty-six Holstein Friesian dairy cows were blocked on days in milk (185 DIM) and balanced for parity, pre-experimental milk yield, milk composition, and body condition score. Cows were randomly assigned to 1 of 3 dietary treatments in a randomized complete block design (n = 12). The 3 treatments consisted of a perennial ryegrass-based pasture-only (PO) treatment and pasture plus either of 2 supplementary concentrates, based on barley (PB) or maize (PM). The diets were fed for a 14-d acclimatization period and then for a further 63-d experimental period. Cows offered PO had a lower daily milk yield (15.1 kg) than PB (18.2 kg) or PM (16.8 kg). Similarly, PO had lower daily milk solids yield (1.46 kg) than PB or PM (1.68 and 1.53 kg, respectively). Cows offered PB had a greater milk yield and higher fat and protein yields than those offered PM. Offering PB increased total DMI (19.5 kg) compared with PO (17.7 kg), and milk response to concentrates was also greater for PB compared with PM (1.21 vs. 0.71 kg of milk per kg of concentrate). Cows offered PB had increased N in milk compared with PO. In conclusion, concentrate supplementation based on barley or maize resulted in increased milk and milk solids yield compared with offering PO. Cows offered barley had a greater response to concentrates and increased milk and milk solids yield in comparison to maize and showed increased N partitioning in milk compared with PO. A barley-based concentrate increased total DMI compared with PO.

The effects of cereal type and α-tocopherol level on milk production, milk composition, rumen fermentation, and nitrogen excretion of spring-calving dairy cows in late lactation.

Grass-based production systems use concentrate supplementation primarily when pasture quality and availability have declined. Barley is a common concentrate ingredient; however, oat grain grows well in Ireland, is a source of lipids and fiber, and may provide an alternative to barley. The antioxidant α-tocopherol (α-TOC) plays a role in cell membrane structure, and it has the potential to improve tight junction structures of the mammary gland that deteriorate in late lactation. The objective of this research was to investigate the effect of cereal type and α-TOC level on milk yield, milk composition, rumen fermentation, and N excretion in late-lactation dairy cows at pasture and when housed indoors on grass silage. Forty-eight Holstein Friesian dairy cows were blocked on days in milk (+185 d in milk) and balanced for parity, pre-experimental milk yield, milk composition, and body condition score and assigned to 1 of 4 dietary treatments in a randomized complete block design (n = 12). The dietary treatments were control (C) base diet; base diet + barley-based concentrate + low α-TOC (350 IU/kg) (B); base diet + oat-based concentrate + low α-TOC (350 IU/kg) (O); and base diet + oat-based concentrate + high α-TOC (1,050 IU/kg) (O+T). Following a 14-d acclimation period, diets were offered for a 49-d experimental period at pasture (P1) and a 21-d experimental period indoors (P2). The base diet was grazed grass in P1 and grass silage in P2. In P2, cows on C also received 2.65 kg (dry matter) of a standard concentrate. In P1, supplementation increased milk and milk solids yield (B: 20.7 kg/d, 1.74 kg/d; O: 20.6 kg/d, 1.81 kg/d; O+T: 20.5 kg/d, 1.77 kg/d, respectively) compared with C (17.8 kg/d, 1.60 kg/d). Cows offered B had a lower milk fat (4.60%) concentration than C (5.00%) and O (4.90%). In P2, cereal type and α-TOC level did not alter milk production. In conclusion, concentrate supplementation increased milk and milk solids yield and cows offered O had a higher milk fat concentration than cows offered B. Increasing the level of α-TOC had no major effect on production parameters measured in P1 or in P2.