Replacement heifer’s breeding season is quickly approaching and getting them ready strategies vary by operation. The ultimate goal however is usually the same, “getting the heifers bred” and preferably early in the breeding season. Little attention is paid however to post breeding management.
To start with heifers should be in a body condition score of 5 or 6 and range between 55 to 65% of their mature weight. Research conducted at SDSU provides some insight on the importance of post breeding management, especially following AI. 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 d of grazing there was no difference in ADG between heifers developed in a drylot and heifers developed on forage. Research conducted at the Antelope Research Station reported that when heifers were moved from drylot to range, they lost weight (3.5 lbs/d) during the first week whereas range-developed heifers gained weight (2.0 lbs/d; Salverson et al., 2009).
Heifer’s 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. Hence, it is recommended to allow animals to increase their consumption of grazed forage to meet nutrient needs. Two studies were conducted at SDSU to determine the impact of adaptation to grazing on weight change and activity when heifers were moved to spring forage (Exp. 1), and whether supplementing heifers when moved to pasture following AI improved pregnancy success (Exp. 2).
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. Daily activity was measured by pedometers (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 (Figure 1). This is significant because energy requirements increase with activity.
Figure 1. LOT heifers were moved from the drylot to forage on d 0 and GRASS heifers had been on forage for 42 days prior to d 0.
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/hd/d of DDGS). Supplementation increased pregnancy success compared to non-supplemented heifers (76% and 61%, respectively). Thus, post breeding management can affect performance and activity. 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.