Benefits of forage-based heifer development and post-AI supplementation.

2010 Annual Report for LNC07-278

Project Type: Research and Education
Funds awarded in 2007: $149,026.00
Projected End Date: 12/31/2010
Region: North Central
State: South Dakota
Project Coordinator:
Dr. George Perry
South Dakota State University

Benefits of forage-based heifer development and post-AI supplementation.

Summary

The second objective determined the influence of post-AI change in nutrition on pregnancy success and embryonic loss. The percentage of heifers that had reached puberty prior to the start of the breeding season tended to be more in the feedlot developed heifers compared to the range developed heifers. However, heifers developed on range tended to have greater pregnancy success compared to heifers developed in the feedlot.

Objectives/Performance Targets

Overall Objective: Evaluate the benefits of forage-based heifer development and determine appropriate post-insemination supplementation to maximize heifer performance.

Objective 1: To determine the influence of post-AI change in nutrition on uterine environment and circulating concentrations of plasma urea nitrogen.

Objective 2: To determine the influence of post-AI change in nutrition on pregnancy success and embryonic loss.

Objective 3: To demonstrate the benefit of forage-based heifer development compared to traditional feedlot developed heifers.

Accomplishments/Milestones

Objective 1 has been completed and data has been submitted to the Midwest section of the American Society of Animal Science.

Results: Weaned heifers were developed to gain 0.454 kg/d for 6 mo either in the feedlot (LOT) or on grass (GRASS). All heifers were synchronized with a CIDR protocol and AI was performed following detection in estrus. Following AI all heifers were moved to a feedlot and each development group, LOT and GRASS, was divided into 3 groups. The groups were fed to maintain weight (MAIN; 6.4 kg hay and 0.01 kg urea/hd) or to gain weight on a diet high (HMP; 6.2 kg hay, 2.9 kg DDGS and 0.03 kg urea/hd)] or low (LMP; 8.0 kg hay and 0.8 kg DDGS/hd) in metabolizable protein. Uterine pH and blood samples were collected from a subset of each group (n=3 LOT and 3 GRASS per post-AI group) on d 0, 7, and 11 after estrus. There was no difference (P>;0.20) in Body Weight between MAIN, HMP, or LMP heifers on the day of AI (311±3.6 kg), but heifers in the HMP and LMP group weighed more (P?0.01) than heifers in the MAIN group on d 11 (344±5.5, 338±5.5 kg, and 315±7; respectively). Uterine pH did not differ (P>0.14) between LOT and GRASS heifers; however, uterine pH decreased (P<0.01) from d 7 to d 11 and was lower (P=0.03) among heifers fed HMP compared to heifers fed LMP or MAIN. There was no difference (P>0.18) between lot and grass developed heifers for blood urea nitrogen (BUN); however, there was a post-AI treatment by time interaction (P<0.01). LOT and GRASS heifers had similar (P>0.14) BUN concentrations on d 0. BUN concentrations in LMP heifers did not change from d 0 to d 7 or 11. BUN increased from d 0 to d 7 and 11 in both MAIN (P?0.04) and HMP (P<0.01). In summary, method of heifer development (LOT or GRASS) did not influence uterine pH or BUN when heifers were fed in a feedlot following AI; however, post-AI diet had an impact on both uterine pH and BUN.

Objective 2: has been completed and data is being utilized for field trial that will be completed this summer.

Results: Weaned heifers were developed from weaning to breeding either in a feedlot (n=52; LOT) or on grass (n=53; GRASS). Immediately following fixed-time AI all heifers were moved to the same pasture. Blood samples were collected from all heifers on d -23, -9, the day of AI (d 0), and d 11. Pregnancy success was determined 42 d following AI. There tended (P=0.10) to be more LOT heifers cycling prior to the breeding season (94% vs 84%), but GRASS heifers tended (P=0.20) to have greater pregnancy success (57% vs. 44%). There were effects of development (P<0.01), time (P<0.01), and development by time (P=0.02) on glucose concentrations. Glucose concentrations decreased from d 0 to d 11 in both groups. Glucose was greater (P<0.01) in GRASS compared to LOT heifers (P<0.01; 87.3 ± 1.24 and 80.2 ± 1.25 mg/dL) on d 0 but similar (P=0.43; 76.29 ± 1.24 and 74.9 ± 1.24 mg/dL) on d 11. Pregnant heifers had greater glucose than open heifers on d 11 (P= 0.04; 77.4 ± 1.24 and 73.8 ± 1.24 mg/dL) but not on d 0 (P=0.88). Concentrations of PUN were influenced by development (P<0.01) and time (P<0.01). Concentrations increased from d 0 to 11, and were greater in GRASS (12.9 ± 0.22 and 15.1 ± 0.22 mg/dL) compared to LOT (11.8 ± 0.22 and 13.6 ± 0.22 mg/dL) heifers. There tended (P=0.07) to be a development by pregnancy interaction with similar (P=0.54) PUN concentrations between LOT pregnant and open heifers, but greater (P=0.04) concentrations in GRASS open compared to GRASS pregnant heifers. Method of heifer development (LOT or GRASS) influenced both glucose and PUN concentrations with GRASS heifer having greater glucose and PUN concentrations compared to LOT heifers, and pregnant heifers tended to have greater glucose than open heifers.

Objective 3: Still needs to be completed

Impacts and Contributions/Outcomes

Recent data from our laboratory has indicated that heifers can be developed on native range, and reproductive performance can be maintained. Therefore this proposal will evaluate the cost and reproductive performance differences between heifers developed in a conventional system and ones developed on forage. Results from the first objective demonstrated that method of heifer development had no impact on uterine pH or blood urea nitrogen, but the diet that heifers were moved to following AI did impact both uterine pH and blood urea nitrogen. Therefore, method of heifer development during the winter should be decided by cost of development and how heifers will be managed after insemination. Results from objective 2 demonstrated that heifers developed in a feedlot may be more likely to have reached puberty, but when moved to grass immediately after insemination conceptions rates tended to be decreased compared to heifers developed on range over the winter.

Collaborators:

Cody Wright

cody.wright@sdstate.edu
Associate Professor
South Dakota State University
Department of Animal and Range Sciences
Box 2170
Brookings, SD 57007
Office Phone: 6056885448
Patricia Johnson

patricia.johnson@sdstate.edu
Professor
South Dakota State University
SDSU West River Ag Center,
1905 Plaza Blvd.
Rapid City, SD 57702
Office Phone: 6053942236
Jim Krantz

krantz.jim@ces.sdstate.edu
Miner County Extension Livestock Educator
South Dakota State University
Miner County Extension Service
PO Box 219
Howard, SD 57349
Office Phone: 6057724661
Julie Walker

walker.julie@ces.sdstate.edu
Associate Professor
South Dakota State University
SDSU West River Ag Center,
1905 Plaza Blvd.
Rapid City, SD 57702
Jack Davis

davis.jack@ces.sdstate.edu
Extension Farm business Educator
South Dakota State University
PO Box 397
Woonsocket, SD 57285
Office Phone: 6057964841