Life Sciences Commons^™

Investigation Of Breeding Objectives And Indexes-In-Retrospect, Hunter F. Valasek

Department of Animal Science: Dissertations, Theses, and Student Research

This thesis presents two projects that investigate the impacts of breeding objectives and indexes-in-retrospect within the beef cattle industry. The first project synthesized how changes due to planning horizon, breeding system, and sale endpoint in the economic breeding goal of cattle influence the relative emphasis of traits as well as the re-ranking of selection candidates. A total of three breeding systems that represent straightbred and crossbred cattle were used along with six planning horizons (2, 5, 10, 20, 30, and 50 yrs.) for both a weaning and slaughter point of sale. The combination of these different breeding objective attributes resulted …

Greenhouse Gas Emissions From Two Contrasting Beef Systems From Birth To Slaughter In Eastern Nebraska, Levi Mcphillips

Department of Animal Science: Dissertations, Theses, and Student Research

Over the last 15 years, the increase in land use for corn and soybean has come at the expense of acres of grasslands and perennial forages employed in conventional beef-production systems. Implementing alternative cow-calf production systems into existing cropping systems may be a solution for reduced land availability and reducing total greenhouse gas emissions (GHG). Therefore, GHG from a conventional (CONV) pasture-based cattle production system with cows wintered on corn residue and summer grazing of brome pasture were compared to partial-confinement system (ALT) with cows and calves in a drylot during the summer and grazing cover crops and corn residue …

Estimation Of Breed Effects And Genetic Parameters For Age At Slaughter And Days To Finish In A Multibreed Beef Cattle Population, Lindsay Upperman

Department of Animal Science: Dissertations, Theses, and Student Research

Cattle efficiency during the finishing phase is a crucial factor in determining profit in the beef cattle industry. Economically relevant traits associated with efficient production include age at slaughter (AAS) and days to finish (DtF). Selection to reduce the number of days an animal takes to reach a finish endpoint would ultimately reduce production costs, increase net profits, and result in a more sustainable production system. However, most harvested animals are from commercial herds, necessitating the use of indicator traits from seedstock animals for selection. Potential indicator traits include ultrasound measurements that could be genetically correlated to DtF traits. The …

Understanding Rumen Microbial Community Structure And Function Towards Decreasing Methane Emissions, Allison L. Knoell

Department of Animal Science: Dissertations, Theses, and Student Research

Resource use is continually being limited due to this growth, therefore, production of high-quality animal protein sources, such as meat and milk, are challenged. The rumen microbiome is extensive and serves to provide several metabolic requirements for the animal for growth. Recently, a significant amount of research is being driven towards understanding the rumen microbiome due to its large effect on metabolic requirements.

A study was conducted to replace alfalfa with nonforage fiber sources in dairy cows. It was determined milk yield and intake are maintained when nonforage fibers replace forage sources, while decreasing methane levels. Water consumption decreased when …

Interaction Of Urea With Frequency And Amount Of Distillers Grains Supplementation For Growing Steers On A High Forage Diet, Haley F. Linder

Department of Animal Science: Dissertations, Theses, and Student Research

Two studies were conducted to determine interactions of urea inclusion to a dried distillers grains plus solubles (DDGS) supplement fed at two amounts and two frequencies to steers on a high forage diet. In Exp. 1, 120 steers were fed individually for 84 d. Steers received ad libitum grass hay and 1 of 8 treatments. Supplement was fed either every day (D) or 3x/week (ALT), amount of supplement fed was 6.36 kg/week (LO) or 12.73 kg/week (HI), and contain either no urea (-U) or 1.3% urea (+U). Hay DMI and steer BW were measured. In Exp. 2, 8 ruminally cannulated …

Improving The Accuracy Of Genomic Predictions: Investigation Of Training Methods And Data Pooling, Johnna Baller

Department of Animal Science: Dissertations, Theses, and Student Research

One of the primary factors in the response to selection is the accuracy of selection. This study focused on methodologies to predict breeding values (BV) accurately within multi- and single-step genomic evaluations. Factors including cross-validation methods, dependent variables, and genotyping strategies were assessed on the accuracy of genomic BV while using multi-step prediction in real and simulated data. In both cases, random clustering led to largest estimated accuracies compared to clusters based on k-means, k-medoids, and principle component analysis, but differences in bias were not detected. Using deregressed estimated BV (EBV) to estimate SNP effects led to larger accuracies and …

Evaluation Of Protein Utilization In Low And High Protein Forage Sources And The Economic Value Of Supplementing Field Peas (Pisum Sativum) To Growing Cattle Grazing Crested Wheatgrass Pastures, Braden C. Troyer

Department of Animal Science: Dissertations, Theses, and Student Research

Field peas are widely grown in the panhandle of Nebraska; however, markets quickly become saturated. A two year experiment was conducted comparing field peas to dry distillers grains with solubles (DDGS) as a protein supplement. The objective was to establish a price producers could pay for field peas relative to DDGS. There was a significant difference in ADG due to type of supplement (P = 0.02). Field pea supplemented heifers had 10% lower ADG compared to DDGS supplemented heifers. Economically, this means if DDGS is priced at or $124.58/ 909 kg DM a producer could pay $2.89/ 27 kg, …

Attainment And Maintenance Of Pubertal Cyclicity May Predict High A4 Cows With Reduced Fertility, Sarah Nafziger

Department of Animal Science: Dissertations, Theses, and Student Research

Puberty attainment was investigated in heifers. Blood samples were collected from weaning until breeding during 6 years from heifers born in 2012-2017. Plasma progesterone concentrations ≥ 1 ng/ml were used to indicate cyclicity, and heifers were categorized into one of four puberty groups using SAS: 1) Early heifers reached puberty before March 12 and cycled continuously during the sampling period, 2) Typical heifers reached puberty on or after March 12 and cycled continuously, 3) Start-Stop heifers had at least one occurrence of progesterone ≥ 1 ng/ml but discontinued cycling during the sampling period, and 4) Non-Cycling heifers had no occurrence …

Identifying Breed Effects For Cow Mature Weight, Madeline J. Zimmermann

Department of Animal Science: Dissertations, Theses, and Student Research

Mature weight (MWT) in beef cattle has increased over the past 30 yr. In general, larger cows are costlier to maintain than smaller cows, and their profitability depends on their production environment. A wide range of beef production environments exist in the United States. There are also a variety of beef cattle breeds that can be chosen and mated to create a type of cow which will be optimally suited to excel in a given environment. However, there remains a need for tools allowing effective comparison among breeds to facilitate such decision making. Unfortunately, estimated progeny differences ( …

Evaluation Of Alpha Amylase Containing Corn On Finishing Cattle Performance And Digestibilty, Melissa L. Jolly-Breithaupt

Department of Animal Science: Dissertations, Theses, and Student Research

One digestion and four finishing trials were conducted to evaluate the effect of a new corn hybrid containing an α-amylase trait, Syngenta Enogen Feed Corn (SYT-EFC) on site and extent of digestion, ruminal fermentation parameters, and feedlot performance. Experiments utilized corn containing the enzymatic gene compared to controls, the near isoline parental corn (NEG) or commercially available corn grain (CON), processed as dry-rolled corn (DRC) or high moisture corn (HMC) in diets with dry [distillers grains plus solubles (DGS)] or wet (Sweet Bran) milling byproducts. The corn grain of the experimental diets were fed as the sole grain source, comprising …

Construction Of A Pen-Scale Methane Collection System And Dietary Strategies For Methane Mitigation From Growing And Finishing Cattle, Thomas Winders

Department of Animal Science: Dissertations, Theses, and Student Research

Methane production from ruminants has been researched for many years because it has a global warming potential 25x that of carbon dioxide, meaning that mitigating smaller amounts of methane can have a large environmental impact. Research has focused on individual animal methane measurements, but the literature lack in industry-scale measurements. For that reason, the methane barn was built to evaluate dietary strategies on pens of cattle rather than on individual animals. In order to test the methane barn capabilities, an experiment designed to produce differences in methane production was conducted. Cattle received the same growing diet, at either ad-libitum access …

Supplementation And Reproductive Strategies For Beef Females As Part Of A May-Calving Herd In The Nebraska Sandhills, Alicia Caitlin Lansford

Department of Animal Science: Dissertations, Theses, and Student Research

The objective of these 4 studies was to evaluate the effects of management decisions on reproductive performance of beef females. Experiment 1 evaluated the efficacy of a novel s.c. prostaglandin F_2a injection on estrus synchronization and pregnancy success in yearling beef heifers. Heifers receiving a 2 mL s.c. injection of Lutalyse HighCon had similar estrus response and pregnancy rates compared to 5 mL Lutalyse i.m. within 2 different estrus synchronization programs. In experiment 2, May-calving heifers and primiparous cows were allotted to receive either no supplementation or supplement (0.45 or 0.91 kg/d per animal, heifers or primiparous cows, …

Genome-Wide Association Study For The Relationship Between Temperature And Feed Intake In Beef Cattle, Robel Ghebrewold

Department of Animal Science: Dissertations, Theses, and Student Research

The interaction of livestock with the environment they live in is complex and plays a significant role in their production performance, which also depends on location and management practices. Climate change is projected to increase temperature globally. As a result, climate change will most likely aggravate the pressure from different sources of stressors on the current agricultural production system in general and in livestock specifically. Environmental conditions, such as changes in ambient temperature, can cause changes in animal behavior and performance. In general, it is believed that as ambient temperature increases, dry matter intake (DMI) of beef cattle decreases. However, …

Development Of Terminal And Maternal Economic Selection Indices In Beefmaster Cattle, Kathleen P. Ochsner

Department of Animal Science: Dissertations, Theses, and Student Research

In the design of economic selection indices, the relative importance of traits in the breeding objective is reflected by their relative economic weighting. The objective of this study was to develop two economic selection indices for Beefmaster cattle: one for a terminal production system and one for a maternal production system. The terminal index was developed assuming bulls are mated to mature cows with all resulting progeny harvested. The maternal index was developed assuming bulls are mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning.

National average prices from 2010 …

Genetic Parameters For Docility, Weaning Weight, Yearling Weight And Intramuscular Fat Percentage In Hereford Cattle, Jose A. Torres-Vazquez

Department of Animal Science: Dissertations, Theses, and Student Research

Temperament in cattle can be described as the reactivity or fear response to human handling, and it is important to beef cattle producers not only from a human safety but also due to potential correlations with other economically traits. Before a docility selection metric can be added to a genetic evaluation, any potential antagonisms with economically relevant traits should be quantified. The objective was to estimate genetic parameters, including genetic correlations, for chute score (CS), weaning weight (WW), yearling weight (YW), and intramuscular fat percentage (IMF) in Hereford cattle. Single-trait and bivariate animal models were used to estimate heritabilities and …

Feeding Condensed Distillers Solubles To Feedlot Finishing Steers And The Effects Of Feed Additives In Adaptation Diets, Marie E. Harris

Department of Animal Science: Dissertations, Theses, and Student Research

By-products from the dry-milling ethanol process can be used in cattle diets to replace corn. There is a significant interaction between corn processing methods as CCDS concentration increases in the diet. Improvements are observed for SFC in final BW, ADG, and G:F over DRC. An experiment was conducted to determine if greater concentrations of CCDS could be fed in SFC based diets and maintain or improve performance. Performance and carcass characteristics were evaluated with increasing concentrations of CCDS at 0, 9, 18, 27, or 36% in place of SFC in feedlot finishing diets. As CCDS concentration increased, DMI decreased quadratically. …

Supplementing Distillers Grains In A Yearling System As A Forage Replacement Tool With Bunk Or Ground Feeding, And Impact Of Winter Supplementation Level On Finishing Performance And Profit, Kari L. Gillespie

Department of Animal Science: Dissertations, Theses, and Student Research

The benefit of adding weight to cattle prior to entering the finishing phase through a forage-based backgrounding system has become more important with increased corn price. Further, as competition for available forage increases, the value of replacing grazed forage with a supplement such as distillers grains, also increases.

A 2-year beef systems study evaluated optimal supplementation time of distillers grains and summer forage savings with distillers supplementation. High winter level supplementation of distillers grains increased winter ADG, decreased summer ADG, and increased final live weights and HCW compared to cattle supplemented at a low supplement level designed to only meet …

The Impact Of Genetic Background On Body Temperature Regulation In Beef Cattle During Periods Of Heat And Cold Stress., Jeremy T. Howard

Department of Animal Science: Dissertations, Theses, and Student Research

Cattle are reared in environments that differ and vary greatly in climate, thus the ability to regulate body temperature across multiple environments is essential. However, inherent differences between animals do exist and can influence their response to extreme temperatures. The objectives of the current study were to model the impact of myostatin genotype (MG) on body temperature during heat and cold stress and conduct a genome-wide association study (GWAS) to better understand the genetic basis of body temperature regulation during extreme temperatures.

Crossbred steers and heifers (n= 239) with varying degrees of Piedmontese influence were fed in four groups over …

Utilization Of Corn Condensed Distillers Solubles And Forages In Management Systems For The Cow-Calf Enterprise, Jason M. Warner

Department of Animal Science: Dissertations, Theses, and Student Research

Of the annual expenses necessary to maintain a beef cow, feed and forage are the greatest and most variable. Thus, nutrition programs for cow-calf operations must be developed using economical feedstuffs that optimize cowherd performance. The corn dry-milling industry provides several feedstuffs that are often the most economical sources of energy and protein, but considerations for storage and handling are necessary. Two experiments evaluated an alternative form of storing corn condensed distillers solubles (CCDS) by applying to grass hay windrows before baling. Round bales were treated with either 0 or 20% (Exp. 1); or 0, 16, and 32% (Exp. 2) …

Evaluation Of Condensed Distillers Solubles And Field Peas For Feedlot Cattle, Anna C. Pesta

Department of Animal Science: Dissertations, Theses, and Student Research

Limited previous research has investigated feeding high levels of condensed distillers solubles (CDS) as an energy source for feedlot cattle. As an energy dense and relatively inexpensive by-product feed from ethanol production, CDS may provide another opportunity to replace high priced corn in finishing diets. Two feedlot studies and one metabolism study were conducted to evaluate the effects of feeding CDS in both corn-based diets, and in combination with other by-product feeds on cattle performance and carcass characteristics. Inclusion of up to 36% CDS, providing 9.4% dietary fat improved performance relative to a corn-based control, with the optimum level of …

Nutrient Management In Beef Feedlots And Forage Replacement With Byproduct And Crop Residues, Annie J. Doerr

Department of Animal Science: Dissertations, Theses, and Student Research

Finishing cattle performance and mass balance was evaluated with Micro-Aid was fed in diets containing wet distillers grains plus solubles (WDGS) at 35% (DM basis). Micro-Aid is a feed ingredient derived from a Yucca extract which contains saponins, and was included in the treatment diet at 1 g/hd daily in the supplement. There was no difference in performance and carcass characteristics between treatments. In the winter experiment, cattle fed Micro-Aid had a greater amount of OM and DM removed from the pen surface. Micro-Aid in the diet increased the amount of manure N and decreased N lossis in the winter. …

Animal Performance And Diet Quality While Grazing Corn Residue, Jennifer A. Gigax

Department of Animal Science: Dissertations, Theses, and Student Research

Grazing cattle on corn residue as a winter feed source has become an integral part of many Nebraska producers’ management plans. Utilizing corn residues extends the grazing season and is often more economical than grazing winter range or dry lot situations. Corn residue is high in OM and NDF, moderate in digestibility, and low in CP. Cattle grazing corn residues may need to be supplemented with a protein source to meet requirements.

The development and application of DNA technology to create new corn hybrids has improved yields with fewer inputs, leading to a continued low cost food supply for consumers. …

Fertilization And Supplementation Strategies For Steers Grazing Smooth Bromegrass Pastures, Andrea K. Watson

Department of Animal Science: Dissertations, Theses, and Student Research

Since 2004, fertilizer prices have doubled due to increases in energy prices for production and increased demand for N fertilizer due to high grain prices. This leads to questioning the cost effectiveness of increasing forage production with N fertilizer. At the same time, an increase in ethanol production creates an increase in the production of by-products of the ethanol industry, such as distillers grains. Distillers grains have been shown to be an excellent feed for ruminants both as a supplement while grazing and as part of a complete diet in the feedlot. Distillers grains provide protein, fat, and highly digestible …

Estimating Livestock Forage Demand: Defining The Animal Unit, Tonya L. Meyer

Department of Animal Science: Dissertations, Theses, and Student Research

The objective of this experiment was to evaluate the effect of a beef animal’s physiological status on forage intake. The experiment was repeated over two years with six replications of three treatments per year: cow-calf pair (CC; BW = 629 kg), dry cow (DC; BW = 503 kg), and yearling steer (S; BW = 305 kg). The cow and calf were treated as one unit, with cow BW and calf BW comprising CC BW. Calves were approximately 42 d of age and weighing 73 kg at the start of each year. Animals were housed in individual pens and fed high …