- Four experiments were conducted (1961-1964) for the primary
purpose of studying the milk and milk constituent yields of dairy cows
under dry lot and pasture systems of management. The secondary
purpose was to compare the health and breeding performance of cows
under these two systems.
Ninety-eight cows of the Holstein and Jersey breeds were used.
These cows were paired on the basis of breed, age, current milk production,
previous lactation yields, days in milk, days in gestation and
udder health and were assigned randomly to the two experimental
Cows in the dry lot groups were fed grass silage and alfalfa
hay (periods I-III) or haylage (period IV) whereas, cows in the
pasture group were strip-grazing irrigated grass-legume pastures.
Both groups were also fed the same concentrate mixture twice daily.
Differences in performance between the two systems were not
significant statistically (P < 0.05) for the following criteria: (1) age
at calving (periods I, III and IV), (2) days in milk prior to experimentation
(periods I, II, and IV), (3) projected milk and milk fat
records (305 day, 2X) for all periods, (4) age adjusted (M.E.) milk
records (periods I, II and IV), (5) age adjusted milk fat records (periods I-IV), (6) complete records (periods I, II and IV), (7) complete
lactation protein records (periods II-IV) and (8) differences between
complete and incomplete projected milk and milk fat records of all
98 cows, Differences in performance were significant for the above
criteria for any of those periods not given in parentheses.
Data collected during the four experimental feeding periods
(84, 150, 150 and 68 days, respectively) on milk, PLM, protein and
milk fat yields, mastitis and reproduction showed no significant
differences (P < 0.05) between the two systems except for milk fat
yield which favored the pasture group during period III and number
of A.I. services for conception which was higher in the dry lot group
during period II. Higher levels of concentrate feeding resulted in
higher milk and milk constituent yields.
The results of these studies indicate that milk cows will perform
equally well when subjected to dry lot or irrigated grass-legume
pastures under the conditions of these experiments.