The Effects of Implants on the Performance of Yearling Heifers Under Different Grazing Intensities
Brian Kreft, Livestock Specialist, Central Grasslands Research Extension Center

 

Every year producers are faced with many management decisions as they prepare to process cattle and place them on summer pasture. Vaccinations, worming, implanting, fly control, and stocking rates are all management practices that must be considered and evaluated to have a profitable outcome.


Implants have been used for many years as a cost-effective and well-accepted way to increase weight gains in almost all classes of cattle. Stocking rates can greatly affect rate of gain. Overgrazing can lead to decreased animal weight gains while under-grazing will decrease gains per acre and can be expensive. The purpose of this study is to evaluate stocking rates and to determine if any interaction exists between implants and various stocking rates.


Materials and Methods


At Central Grasslands Research Extension Center, two hundred and six yearling heifers were stratified by weight and allotted to twelve different pastures with four different grazing treatments. They were light stocking (0.7 of moderate), moderate (NRCS recommended rate), heavy (1.3 of moderate), and extreme (1.6 of moderate). The heifers from each pasture were then assigned into two subgroups, implant or no implant. Each pasture was replicated three times. The heifers were weighed and condition scored on May 10, 2004. The heifers assigned to the implant group were administered Synovex H at that time. All other management treatments were the same. They were pastured for 122 days until September 9, when final weights and condition scores were collected.


Results and Conclusions


The results show that the lightest grazed pastures had the highest average daily gains (ADGs) and as the grazing intensity increased, gains decreased (Table 1). The highest ADGs were in the light grazed pasture (1.71 lbs) and lowest in the extreme grazed pasture (1.05 lbs); however these differences were not statistically significant. The implant showed a slight increase in gain (1.28 lb/day vs. 1.38 lb/day) over the non-implanted heifers, but this difference was not significant (P≥0.10). There was no grazing intensity x implant interaction (P≥0.10) and condition scores were not affected by implants.


Table 1. The effect of implants on heifers under different grazing intensities.

 

 

No Implant

Implant

Grazing Intensity

AUMs/Acre

# of Animals

ADG

Condition

# of Animals

ADG

Condition

Light

0.49

  12

1.72*

4.83

  12

1.70

4.67

Moderate

1.01

  21

1.55

4.86

  21

1.69

5.02

Heavy

1.70

  26

1.35

4.81

  27

1.45

4.87

Extreme

2.73

  43

0.99

4.37

  44

1.11

4.32

Total/Avg.

1.48

102

1.28

4.64

104

1.38

4.64

*No significant differences were found in average daily gains or condition scores due to grazing intensity or implant treatments.


NDSU Central Grasslands Research Extension Center
Home2004 Annual Report