Publications by authors named "Mary K Mullenix"

2 Publications

  • Page 1 of 1

Evaluation of nitrogen-delivery methods for stocker cattle grazing annual ryegrass.

Transl Anim Sci 2021 Apr 19;5(2):txab048. Epub 2021 Mar 19.

Department of Animal Sciences, Auburn University, Auburn, AL 36849, USA.

A 2-yr grazing experiment was conducted to evaluate efficacy of nitrogen (N) fertilization, interseeded legumes, and protein supplementation for N delivery to stocker cattle grazing annual ryegrass (). Each year, 90 steers (initial BW, 241 ± 13 kg) were assigned to the following N-delivery methods, with or without monensin fed in a free-choice mineral supplement as a 5 × 2 factorial arrangement of treatments: ryegrass fertilized with 112 kg N/ha (NFERT); ryegrass interseeded with crimson clover (CC, ); ryegrass interseeded with arrowleaf clover (AC, ); ryegrass plus distillers dried grains with solubles (DDGS) supplemented at 0.65% BW daily; and ryegrass plus whole cottonseed (WCS) supplemented at 0.65% BW daily. Pastures within the interseeded-clover and protein-supplementation treatments were fertilized with 56 kg N/ha at time of establishment. Steers were weighed every 28 d, and forage mass (FM, kg DM/ha) was measured concurrently using the destructive harvest/disk meter double-sampling method. Each of 30 0.81-ha paddocks was stocked initially with 3 "tester" steers, and stocking density (steers/ha) was adjusted using "put-and-take steers" based on changes in FM and steer BW in order to maintain a uniform forage allowance (FA) of 1 kg DM/kg steer BW. Grazing was discontinued on May 11, 2016 in Yr 1 and May 10, 2017 in Yr 2 following 140 and 84 d of grazing, respectively. Data were analyzed as a completely randomized design with repeated measures for which pasture ( = 3) was the experimental unit. Ionophore inclusion did not affect ( > 0.10) any variable measured. Mean FM differed ( < 0.0001) between years and among N-delivery methods ( < 0.10), and mean FA differed ( = 0.005) among N-delivery methods. Steer ADG differed among N-delivery methods ( = 0.02) and between years ( < 0.001), whereas total gain/ha differed ( < 0.0008) among N-delivery methods, but not between years ( = 0.78). Stocking density differed among N-delivery methods ( = 0.02) and between years ( < 0.0001), and grazing-days/ha differed between years ( < 0.0001) and among N-delivery methods ( = 0.001). Results indicate that supplementation with a high-protein by-product feed for cattle grazing annual ryegrass maintained ADG, total gain/ha and grazing-days/ha compared with N-fertilized annual ryegrass, and increased ADG, total gain/ha, and grazing-days over interseeded legumes.
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April 2021

Cow-calf performance, forage utilization, and economics of warm-season annual baleage in beef cattle winter feeding systems.

Transl Anim Sci 2020 Jan 9;4(1):376-384. Epub 2019 Nov 9.

Department of Animal Sciences, Auburn University, Auburn, AL.

A 52-d winter feeding trial was conducted to determine animal performance, utilization, and economics of pearl millet (PM) baleage, sorghum × sudangrass (SS) baleage, and "Tifton 85" bermudagrass (B) hay for lactating beef cow-calf pairs. Cone (C) and open-shaped (O) rings were evaluated for potential to minimize forage wastage. The experiment was a completely randomized design with a 3 × 2 factorial arrangement of treatments for each forage type × hay ring (3 cow-calf pairs per treatment; 2 replications per treatment). Animal response measures included cow body weight (BW) change and body condition score (BCS) over the 52-d trial, initial and final calf BW, and cow milk production at the midpoint and end of the study. Forage nutritive value parameters evaluated for each forage type included ash, crude protein (CP), in vitro true digestibility (IVTD), neutral detergent fiber (NDF), acid detergent fiber, and acid detergent lignin (ADL). Forage wastage was estimated for each forage × ring treatment as the percentage of the bale weight remaining in feeding rings at the time of bale replacement. An economic evaluation of the relative costs associated with production and utilization of each forage type was calculated. There were no differences ( ≥ 0.10) in cow BW change or BCS change among forage types, between ring shapes, or an interaction observed for these response variables. Proportion of waste from PM and SS baleage was greater ( < 0.10) than for B hay, although there was no forage type × hay ring interaction or differences between O and C hay ring treatments for forage waste ( ≥ 0.10, respectively). Cow milk production and calf BW gain did not differ among forage type ( ≥ 0.10, respectively); however, beef calves in pens containing the O ring feeder weighed 6 kg more ( ≤ 0.05) than calves whose dams were fed using C rings. The economic analysis implies that it is more costly to feed warm-season annual forage baleage to cow-calf pairs than dry hay, largely due to greater costs of production, lack of difference in animal performance responses, and less utilization of baleage compared with feeding bermudagrass hay in this trial.
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January 2020