Date of this Version
Published in Proceedings, Western Section, American Society of Animal Science (2008) 60: 85-88.
Effects of providing differing levels of harvested feed during postweaning development and subsequent winters on reproduction, BW, BCS, and calf BW were evaluated in heifers produced over a 7-yr period from dams fed levels of harvested feed from Dec to March that were expected to be marginal (MARG) or adequate (ADEQ), based on average quality and availability of winter forage. Heifers were either fed to appetite (CON) or restricted fed at 80 % of that consumed by CON on common BW basis (REST) for 140-d period from about 2 mo after weaning to 1 mo before breeding. Heifers were managed together through breeding until Dec when they were separated so CON could be fed adequate harvested feed and REST could be fed marginal levels of harvested feed until 2 to 3 wk before start of calving in March. Cows remained in their treatment through subsequent winters until removed for failure to reproduce or wean a calf. Percent of heifers becoming pregnant and remaining at start of 2nd breeding season was not influenced by dam or heifer treatments (P > 0.23; total df = 631). Retention to start of 3rd breeding was less (P = 0.01) in REST (58 %) than CON (69 %). Interaction of dam and cow treatments (P < 0.07) influenced retention to 4th and 5th breeding. Retention to 4th breeding was less (P < 0.1) for REST cows from ADEQ dams (46 %) than the other dam by cow treatment groups (57 to 62 %). Retention to 5th breeding was less for REST cows from ADEQ dams (39 %; P < 0.01) than REST cows from MARG dams (66 %); with CON cows from MARG (50%) or ADEQ dams (51 %) being intermediate. Weight and BCS at start of each breeding was 10 kg and 0.10 BCS less (P < 0.01) for REST than CON cows. At start of 3rd, 4th and 5th breeding, cows from MARG dams were 15 to 24 kg heavier (P < 0.01) than cows from ADEQ dams. Calves from REST cows and MARG granddams were lighter (P < 0.01) at birth and weaning by 1.0 and 6.9 kg, respectively, than calves from the other groups (interaction P <0.06). Productivity of cows managed on 2 levels of harvested feed inputs was influenced by the level of harvested feed provided to their dams; greatest feed input did not maximize long term retention.