Publication history: Accepted - 11 December 2021; Published online - 3 February 2022.A diverse range of grassland-based milk produc-
tion systems are practiced on dairy farms in temper-
ate regions, with systems differing in relation to the
proportion of grazed grass, conserved forages and
concentrates in diet, calving season, duration of hous-
ing, cow genotype, and performance levels. The current
study was conducted to examine performance within
diverse grassland-based systems of milk production
under experimental conditions. This study examined 4
milk production systems over 3 successive lactations
(20 cows per system during each lactation). With win-
ter calving-fully housed (WC-FH), Holstein cows were
housed for the entire lactation and offered a complete
diet consisting of grass silage, maize silage, and con-
centrates [approximately 50% forage on a dry matter
(DM) basis]. With winter calving-conventional (WC-
Con), Holstein cows were housed and offered the same
diet from calving until turnout (late March) as offered
with WC-FH, and thereafter cows were given access to
grazing and supplemented with 5.0 kg of concentrate/
cow daily. Two spring-calving systems were examined,
the former involving Holstein cows (SC-H) and the lat-
ter Jersey × Holstein crossbred cows (SC-J×H). Cows
on these systems were offered a grass silage-concentrate
mix (70% forage on a DM basis) until turnout (late
February), and thereafter cows were given access to
grazing supplemented with 1.0 kg of concentrate/
cow per day. The contributions of concentrates (3,080,
2,175, 722, and 760 kg of DM/cow per lactation),
conserved forages (3,199, 1,556, 1,053, and 1,066 kg
of DM/cow per lactation), and grazed grass (0, 2,041,
2,788, and 2,692 kg of DM/cow per lactation) to total
DMI (6,362, 5,763, 4,563, and 4,473 kg of DM/cow per
lactation) with WC-FH, WC-Con, SC-H, and SC-J×H,
respectively, varied considerably. Similarly, milk yield
(9,333, 8,443, 6,464, and 6,049 kg/cow per lactation),
milk fat content (44.9, 43.3, 42.8, and 49.0 g/kg), and
milk protein content (34.6, 34.9, 33.6, and 36.3 g/kg)
differed between systems (WC-FH, WC-Con, SC-H,
and SC-J×H, respectively). The higher milk yields with
the WC systems reflect the greater concentrate inputs
with these systems, whereas the greater milk fat and
protein content with SC-J×H reflect the use of Jersey
crossbred cows. Crossbred cows on SC-J×H produced
a similar yield of milk solids as Holstein cows on SC-H.
Cows on WC-FH ended the lactation with a greater
body weight (BW) and body condition score than cows
on any other treatment. While Jersey crossbred cows
on SC-J×H had a lower BW than Holstein cows on
SC-H, cows on these 2 systems were not different for
any of the other BW, body condition score, or blood
metabolite parameters examined. Cows on WC-FH had
a greater interval from calving to conception, a greater
mastitis incidence, and a greater locomotion score than
cows on the spring calving systems. Whole-system
stocking rates and annual milk outputs were calcu-
lated as 2.99, 2.62, 2.48, and 2.50 cows/ha, and 25,706,
20,822, 15,289, and 14,564 kg of milk/ha, with each
of WC-FH, WC-Con, SC-H, and SC-J×H, respectively.
Gross margin per cow was highest with WC-Con, gross
margin per hectare was highest with WC-FH, and gross
margin per kilogram of milk was highest with SC-J×H.
This study demonstrated that diverse grassland-based
milk production systems are associated with very dif-
ferent levels of performance when examined per cow
and per hectare.This work was funded by the Department of Agriculture and Rural Development in Northern Ireland (DAERA), and by AgriSearch (farmer levy)
