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Title:Nutrition and management considerations for bulls and breeding females
Author(s):Henley, Parker Allen
Director of Research:Shike, Daniel W
Doctoral Committee Chair(s):Shike, Daniel W
Doctoral Committee Member(s):McCann, Joshua; Parrett, Douglas F; Canisso, Igor F
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):bull
nutrition, reproduction
heifer
Abstract:The development of bulls and breeding females to productive beef animals represents a substantial economic impact to the producer, and development can ultimately impact reproductive success and longevity within the herd. To maintain herd size and productivity, proper selection and retention of replacement females drives the sustainability of a beef cattle operation. A significant portion of the reproductive failures in cow-calf enterprises is due to the fertility of the herd bull. Thus, the objective of this dissertation was to evaluate nutritional and management strategies to optimize the development of bulls and breeding females. Research has been inconsistent on what is the ideal heifer development strategy and how it translates to fescue-based production systems. Thus, the objectives of experiment 1 were to evaluate the effect of heifer development system on body weight (BW), body condition score (BCS), fescue toxicosis symptoms, reproductive performance, and subsequent calf growth of fall-calving beef heifers. Angus × Simmental heifers [n = 399; 240 ± 20.0 kg initial BW; age = 252 ± 20 d] were stratified by BW and BCS and assigned to 1 of 12 groups in each of the two production years. Pens were randomly assigned to 4 treatments: drylot (DL) development (fed ad-libitum 90% hay and 10% DDGS on a dry matter basis), grazing endophyte-infected fescue supplemented daily (2.3 kg as-fed/heifer/d; 50:50 mix of soybean hulls and DDGS; E+/S), grazing endophyte-infected fescue and supplemented from the midpoint of treatment period until breeding (4.5 kg as-fed/heifer/d; 50:50 mix of soybean hulls and DDGS; E+/LS), and grazing novel endophyte-infected fescue with no supplementation (NE+/NS). Treatments DL and E+/S represent traditional Midwestern development strategies in contrast to the alternative strategies in E+/LS and NE+/NS. Heifers in DL had the greatest (P ≤ 0.05) BW and BCS from d 28 until d 254. Furthermore, E+/S heifers had a greater (P ≤ 0.05) BW and BCS than both E+/LS and NE+/NS from d 28 until d 168. On d 56 and 84, E+/LS heifers had lower (P ≤ 0.05) BW and BCS compared to NE+/NS, but on d 140, they switched and remained at a greater (P ≤ 0.05) BW and BCS compared to NE+/NS through the first breeding season. Drylot heifers had the greatest (P ≤ 0.05) cyclicity, percentage of mature BW at AI (66.6%), and had greater (P ≤ 0.05) AI and overall pregnancy rates compared to E+/LS and NE+/NS females. The E+/S (55%) and E+/LS (53.7%) heifers were developed to a greater (P < 0.01) percentage of mature BW than NE+/NS (49.3%). A greater (P ≤ 0.02) percentage of DL and E+/S heifers were pregnant at the end of the first breeding season (89.3 and 85.1%; respectively) compared to NE+/NS females (61.5%). In summary, DL heifers had the greatest BW and BCS at AI, percentage cycling, and AI pregnancy rate. However, this strategy did not result in differing overall pregnancy rates between DL, E+/S, and E+/LS, and there were no differences in cow milk production, rebreeding reproductive performance and calf performance between all treatments. This would suggest that DL, E+/S, E+/LS systems are all viable strategies for developing fall-born replacement beef heifers in the Midwest. Transitioning beef females from the drylot to a grazing setting is one of the most challenging times from a nutritional standpoint especially when it coincides with lush pasture growth. This can lead to cows entering a negative energy balance. The nutritional requirement for growth and lactation of the two-yr-old lactating cow makes her extremely susceptible to a nutritional insult. However, the lack of grazing experience of heifers can cause issues when first exposed to grass. Thus, the objectives of experiment 2 were to evaluate the effect of corn supplementation and age of female on body weight (BW), body condition score (BCS), artificial insemination (AI) pregnancy rate, and blood metabolites. Angus and Angus × Simmental beef females (n = 361) were blocked by location then stratified by BW and BCS and were assigned to 1 of 8 pens/location with 9-14 females/pen over two production yr. The four treatment groups were: yearling heifers receiving no supplement (CON-H); yearling heifers receiving supplement of dry rolled corn [(SUPP-H); 1.81 kg as-fed/heifer/d] for 42 d; two-yr-old lactating cow-calf pairs receiving no supplement (CON-C); and two-yr-old lactating cow-calf pairs receiving supplement of dry rolled corn [(SUPP-C); 1.81 kg as-fed / cow/d] for 42 d. Females receiving SUPP had a greater (P ≤ 0.10) BW and BCS at d 42 and BW change over the supplementation period. Control females tended (P = 0.10) to have greater serum NEFA concentrations compared to SUPP females. Cow BUN increased more (P = 0.02) from d 0 to d 12 compared to heifers, whereas, SUPP females tended (P ≤ 0.08) to have lower BUN at d 12 and d 42 compared to control females. Supplementation effects were not detected (P ≥ 0.25) for AI or overall pregnancy rate. In conclusion, there were no supplementation × age interactions excluding d 42 BCS. Supplementation regardless of female age, tended to improve d 42 BW and BW change. Cow NEFA decreased more and BUN increased more from d 0 to d 12 compared to the heifers whereas the supplemented females had lower NEFA and BUN. Even though cows tended to have greater AI pregnancy rates than heifers, supplementation did not affect AI or overall pregnancy rates. Breeding bulls across the United States are commonly fed high-energy diets by seedstock producers prior to sale, generally in the form of grain. Costs associated with feeding these diets have led producers to consider cheaper alternatives such as distillers grains with solubles. But there is no data available on the impact of coproducts on developing bulls. Thus, the objectives of experiment 3 were to evaluate the effect of distillers grains with solubles supplementation on performance and reproductive traits of bulls. Simmental × Angus bulls (n = 28) were stratified by BW (316 ± 29 kg) and sire. Pens were randomly assigned to 1 of 2 dietary treatments (3 pens/treatment): 1) 40% modified wet distillers grains plus solubles (MWDGS; DST; DM basis), or 2) corn based diet with no MWDGS (CON). Treatment × time interaction was detected (P < 0.01) for BW; however, when sliced by time, BW within each day did not differ between treatments (P ≥ 0.43). Treatment × time and treatment effects were not detected (P ≥ 0.40) for BCS, HH, hoof scores, MS and MD. Treatment effects were not detected (P ≥ 0.53) on ADG, DMI, and G:F. A treatment × time effect was detected (P < 0.01) for RF and BF. Bulls fed DST had greater RF (P = 0.01) on d 84 and greater BF (P ≤ 0.04) on d 56, 84, 112, and 175 than CON bulls. A treatment × time effect was detected (P = 0.04) for scrotal circumference (SC), which tended (P = 0.07) to be greater for DST vs. CON bulls on d 210. However, effects of treatment × time and treatment were not detected (P ≥ 0.12) for spermatic cord circumference, percent of bulls deemed as satisfactory after BSE, normal morphology, minor defects, percentage overall motility, progressive motility, and total cells. Treatment × time effect was detected (P < 0.03) for major sperm defects and proximal droplets. Bulls fed DST had a greater (P < 0.01) percentage of major defects and percentage of proximal droplets (P = 0.01) on d 140 than CON bulls. Distillers resulted in slightly fatter bulls and an increase in major semen defects at end of treatment period, but bulls recovered during the common low-energy diet and there were no differences in any other reproductive parameters. In summary, producers can properly develop fall born beef heifers in the drylot or grazing setting. Supplementing corn daily had no impact on the reproductive performance of heifers or two-yr-old lactating cows when they are grazing lush spring pasture. Finally, producers may include low S distillers grains with solubles into the diet of developing bulls up to 40% (DM basis) in order to reduce ration cost without negative effects on long-term reproductive performance.
Issue Date:2019-12-18
Type:Thesis
URI:http://hdl.handle.net/2142/107839
Rights Information:Copyright 2020 Parker Henley
Date Available in IDEALS:2020-08-26
Date Deposited:2020-05


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