With the replacement heifer breeding season quickly approaching, South Dakota State University animal science specialist Julie Walker and SDSU beef reproduction specialist George Perry advise that beef producers should pay more attention to post-breeding replacement heifer management.
To begin, replacement heifers should have a body condition score of 5 or 6 and range between 55% and 65% of their mature weight.
Research conducted at SDSU provides some insight on the importance of post breeding management, especially following artificial insemination, Perry and Walker write:
"Previous research (Perry et al., 2013) has indicated that moving drylot-developed heifers to spring forage immediately after AI adversely affected ADG and AI conception rates. However, after 27 days of grazing there was no difference in ADG between heifers developed in a drylot and heifers developed on forage."
More research (Salverson et al., 2009) reported that when replacement heifers were moved from drylot to range, they lost weight (3.5 lbs/day) during the first week whereas range-developed heifers gained weight (2.0 lbs/day).
Perry and Walker note that heifers' grazing skills and dietary habits are acquired early in life, and this learning is important to develop the motor skills necessary to harvest and ingest forage.
They recommend that animals are allowed to increase their consumption of grazed forage to meet nutrient needs.
ON PAGE 2: Research - grazing replacement heifers after breeding >>
Grazing replacement heifers post-breeding
Two studies were conducted at SDSU to determine the impact of adaptation to grazing on weight change and activity when replacement heifers were moved to spring forage and whether supplementing heifers when moved to pasture following AI improved pregnancy success.
Perry and Walker explain:
Experiment 1 was conducted to investigate if heifer development management could impact grazing behavior. Sixty-nine drylot developed heifers were randomly allotted to one of two treatments: 1) heifers remained in the drylot, or 2) heifers were moved to graze spring forage during 42 days.
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Daily activity was measured by steps per day. Heifers that were grazing spring forage took more steps per day compared to heifers in the drylot. However, following being moved to spring pasture, heifers that remained in the drylot increased activity compared to those with previous experience grazing spring forage. This is significant because energy requirements increase with activity. (See results below)
In the second experiment, 301 drylot-developed heifers were synchronized with the 7-d CIDR protocol. Heifers were either moved to pasture at AI, or moved to pasture and supplemented (5 lbs per head per day of DDGs).
Supplementation increased pregnancy success compared to non-supplemented replacement heifers (76% and 61%, respectively). The results show that post breeding management can affect performance and activity, the specialists note.
"Management options that provide an adaption period for heifers prior to the breeding season or supplementation when heifers are moved to pasture can allow for increased reproductive efficiency," they wrote.
Adapted from: Replacement Heifers Post Breeding Management, SDSU iGrow