Impact of Grazing Management, Monensin Supplementation and Weed Density on Beef Cow-Calf Performance and Pasture Production
Open Access
- Author:
- Duppstadt, Leanna Marie
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 20, 2018
- Committee Members:
- Jessica Williamson, Thesis Advisor/Co-Advisor
Tara Felix, Committee Member
Marvin Hall, Thesis Advisor/Co-Advisor - Keywords:
- monensin
managed grazing
pasture productivity
weed management
beef production - Abstract:
- Monensin (Rumensin 90®, Elanco Animal Health; Greenfield, IN) is a direct-fed ionophore that alters ruminal fermentation and has been shown to increase energy efficiency by altering VFA production in the rumen, resulting in improved forage utilization. This suggests that monensin has the potential to alleviate the effects of a cool-season perennial pasture “summer slump”. Weeds compete with desired forages for natural resources and can have a negative impact on livestock and pasture production. Grazing management strategies are implemented to encourage desirable forage growth and discourage the growth of undesirable species; suggesting that the implementation of rotational grazing could alleviate competition with weeds. In experiment 1, 32 spring-calving, Angus-based cow-calf pairs were stratified into pastures based on body weight (BW) and blocked by age. The study was conducted using 2x2 factorial, for 3 years (2015-2017) with 56-d grazing seasons each year. All cows were limit-fed wheat mid-based pellets with (MON; 200 mg/cow/day) or without monensin (NOMON). Treatments included 1) continuous grazing without monensin supplementation (CONT NOMON); 2) continuous grazing with monensin supplementation (CONT MON); 3) rotational grazing without monensin supplementation (ROT NOMON); and 4) rotational grazing with monensin supplementation (ROT MON). Cows in ROT were rotated every 7-d and desired forage height was maintained by put-and-take stocking. Precipitation was highest in June and July for Years 1 and 3, and lowest in Year 2. Temperatures were highest in July and August of Year 2 and this in combination with low precipitation created the ideal conditions for a true “summer slump” in PA in 2016. There were no grazing x supplement interactions, nor were there main effects of monensin inclusion or grazing management for Years 1 and 3 (P = 0.80 and P = 0.77, respectively). In Year 2, all cows lost BW and body condition score (BCS) from d 0 to 56, but cows on ROT receiving MON lost the least (grazing x supp: BW (P = 0.02) and BCS (P ≤ 0.01)).There were no main effects or interactions for carrying capacity (CC) or stocking rate (SR) in Years 1 and 3. Cows on ROT grazed pastures and cows receiving MON had greater CC and SR for grazing treatment (P = 0.07) and supplement treatment (P < 0.01) compared to CONT pastures and NOMON supplementation. In experiment 2, 32 cow-calf pairs were grazed over 2 consecutive years either ROT or CONT to determine the effects of grazing management on weeds as well as weed-forage nitrogen uptake. The amount of weeds present in ROT tended to decrease (P = 0.13) while CONT weeds remained the same. Kentucky bluegrass increased (P = 0.06) in pastures that were CONT grazed. Orchardgrass tended to decrease in CONT and increase in ROT (P = 0.14). There was a year x nitrogen content interaction (P = 0.03) with weeds having a higher percent nitrogen (N) content across both years. Weeds also had a total N content that was higher (P ≤ 0.0001) than the desired forages. During times of ample forage availability and quality, monensin appears to have no significant impact; however, during times of drought stress, monensin supplementation may benefit pasture productivity and cow performance. Managed grazing such as rotational grazing, may have the ability to increase forage quality, quantity, SR, CC and decrease the prevalence of weeds.