Nutritional and reproductive management considerations in the beef female

Ewing, Kylie Paige

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https://hdl.handle.net/2142/124333 Copy

Description

Title

Nutritional and reproductive management considerations in the beef female

Author(s)

Ewing, Kylie Paige

Issue Date

2024-04-20

Director of Research (if dissertation) or Advisor (if thesis)

Shike, Daniel W

Doctoral Committee Chair(s)

Shike, Daniel W

Committee Member(s)

• Berger, Larry L
• McCann, Joshua C
• Meteer, William T

Department of Study

Animal Sciences

Discipline

Animal Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• tall fescue
• stockpile
• grazing management
• cover crops
• cow performance
• feed value
• heifer development
• reproduction
• target mature body weight
• age

Abstract

Minimizing feed costs and optimizing reproductive success are key to maximizing profitability in beef cow-calf operations. One strategy used to reduce feed costs is the use of stockpiling to extend the grazing season. A major challenge of stockpile implementation is having adequate acreage to set aside while simultaneously grazing cattle. Alternative feedstuffs, such as mechanically harvested cover crops, are also of interest to producers, particularly when traditional feedstuffs are expensive or difficult to source. However, little data has evaluated the feed value of mechanically harvested cover crops fed to beef cattle. For cow-calf producers, heifer reproductive performance is also key to maximizing profitability. Understanding the implications of heifer age, body weight, and the interaction of age and weight at breeding on subsequent performance is vital. The objective of this dissertation was to evaluate the effects of a spring and fall stockpiling system, mechanically harvested cover crops, and heifer age and body weight at breeding on relevant response variables such as forage biomass and quality, system economics, cow body condition and reproductive performance, as well as calf performance. The objective of the 1st study was to compare the effects of tall fescue grazing systems utilizing either rotational grazing only or rotational grazing and spring and fall stockpiling on beef cow body condition and reproductive performance, calf pre-weaning performance, forage characteristics, and system economics. Over 2 years, multiparous, fall-calving cows (n = 360/year; BW = 600 ± 64 kg; gestation = 113 ± 9 d) were randomly assigned to 1 of 2 treatments; 1) rotational grazing only (CON) and 2) rotational grazing and spring and fall stockpile grazing (SP). Control pastures were divided into eight (6.1 ha; rotated every 5 d) paddocks. A complete rotation through CON paddocks was defined as a grazing round. Twenty-five percent of SP pastures (12.1 ha) were stockpiled for the initial 120 d with the remaining 75% rotationally grazed (36.3 ha; rotated every 6-7 d). Starting in early August, 50% (24.2 ha) of the pasture was stockpiled. Strip-grazing (moved every 2-3 d) was utilized when grazing stockpiled forage in SP pastures. Cows grazed for 25 more (P < 0.01) d in SP compared with CON, resulting in a subsequent reduction (P < 0.01) of hay fed per cow in SP compared with CON (59 vs. 347 kg, respectively). Cow BW did not differ at trial end (P = 0.13) however, BCS was greater (P < 0.01) in CON than SP (5.3 vs. 5.1, respectively). No differences (P ≥ 0.18) were observed in TAI pregnancy rate or overall pregnancy rate between treatments. At mid to low urea price points, SP had greater cost savings ($5.53 to $11.72/hd) compared with CON, regardless of hay costs. Overall, utilization of a spring and fall stockpiling system had minor impacts on cow performance but increased grazing days and reduced stored feed use, with the potential to decrease winter feed costs. The objective of the 2nd study was to evaluate the effects of rye or triticale with or without crimson clover on forage yield and quality, gestating beef female performance, as well as in situ degradation kinetics. In experiment 1, four cover crop treatments were randomly assigned to plot (0.49 ha/plot; 6 plots/trt) in a 2×2 factorial design. Treatments included cereal rye or triticale with or without crimson clover and were mechanically harvested for silage at the end of May. Forage yield was not different (P ≥ 0.64) between cereal types or with crimson clover inclusion. Crimson clover inclusion tended (P = 0.07) to increase CP (8.0% vs 7.4%, respectively). Neutral detergent fiber and ADF were greater (P < 0.01) in rye compared with triticale. Crimson clover inclusion decreased (P < 0.01) NDF compared with monocultures. In experiment 2, a 2 × 2 factorial arrangement plus 1 was used to determine in situ degradation kinetics of the 4 cover crop silages from experiment 1, as well as alfalfa hay. In 2 blocks, duplicate Ankom bags were inserted simultaneously into 2 steers with removal at 0, 2, 4, 6, 8, 16, 24, 48, and 96 h. Dry matter and OM effective ruminal degradation (ERD) were greater (P ≤ 0.01) for cover crops compared with alfalfa. Although there were differences in cover crop DM, CP, NDF, and ADF this did not result in differences (P ≥ 0.23) in ERD for DM, OM, or NDF between cereal types or with clover inclusion. In experiment 3, spring-calving cows and heifers (n = 105; BW = 633 ± 100 kg; gestation = 198 ± 17 days) were randomly assigned to 1 of 5 treatment diets in a 42-d feeding trial. Four diets were based on cover crops (60% inclusion) from experiment 1, with an additional control diet (HayTMR; 85% alfalfa hay and 15% modified wet distillers grains). All treatments were limit-fed based on diet formulation to meet maintenance requirements of HayTMR (NASEM, 2016). Final BCS, and BCS change were not different (P ≥ 0.29) between treatments. Female final BW and BW change were greater (P < 0.01) in cover crop treatments compared with HayTMR. Final BW and BW change did not differ (P ≥ 0.46) between cereal type or with inclusion of crimson clover. These data suggest the cover crops evaluated have greater feed value than late-bloom alfalfa hay and may be used as an alternative feedstuff replacement for late-bloom alfalfa in mid-to-late gestation beef cow diets. The objective of the 3rd study was to evaluate the effects of age, body weight, and the interaction of age and body weight at breeding on heifer reproductive performance as well as subsequent parity performance. Heifers (2 cohorts; total n = 326; BW = 310 ± 29 kg) were artificially inseminated (AI) at 1 of 2 dates (14 d apart) but were otherwise managed similarly throughout the duration of data collection. Data were collected through 2 parities. Post-hoc, heifers were classified based on percent mature body weight (MBW) at breeding (LoMBW, < -0.5 SD from mean; AvgMBW, ± 0.5 SD from mean; or HiMBW, > 0.5 SD from mean) and age at breeding (YgAGE, < -0.5 SD from mean; AvgAGE, ± 0.5 SD from mean; or OldAGE, > 0.5 SD from mean) and individual analyses were conducted. The OldAGE and YgAGE heifers were then split by BW (heavy, Hvy; or light, Lite) and the interaction of age and body weight (OldHvy, OldLite, YgHvy, YgLite) at breeding was analyzed. The LoMBW heifers (50% of MBW) had reduced (P < 0.01) overall pregnancy rate compared with AvgMBW and HiMBW heifers (56% and 61% of MBW, respectively). The YgAGE heifers had reduced (P ≤ 0.03) AI conception and overall pregnancy rates compared with AvgAGE and OldAGE heifers. There were no differences (P = 0.29) observed in AI conception or overall pregnancy rates for OldHvy or OldLite heifers. However, in young heifers’ weight impacted reproductive performance, with a tendency for greater (P = 0.10) AI conception rate and greater (P = 0.05) overall pregnancy rates in YgHvy compared with YgLite heifers. These data indicate that fertility may be compromised in heifers developed to less than 56% of MBW as well as young heifers (≤ 425 d of age). Additionally, BW appears to be a more important factor in determining reproductive success in young heifers compared with older heifers (≥ 436 d of age). Ultimately, incorporation of spring and fall stockpiling into a rotational grazing system enabled implementation of stockpiling while utilizing the same number of acres as a rotationally grazing only system. This system had minor effects on cow and calf performance but reduced stored feed use and may reduce stored feed costs. Data from study 2 suggest that the cover crop silages evaluated, are an adequate alternative feedstuff replacement for late-bloom alfalfa hay when fed to gestating beef cows. Study 3 results indicate that 1) heifers should be developed to ≥ 56% of MBW by breeding 2). reproductive success may be enhanced if older (≥ 436 d at breeding) heifers are kept as replacements 3). young (≤ 425 d at breeding) heifers likely require additional supplementation to attain greater BW prior to breeding and increase probability of reproductive success.

Graduation Semester

2024-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2024 Kylie Ewing

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