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Item Influence of Plasma Nuclear Magnetic Resonance Profile, Urea-Nitrogen, Glucose and Non-Esterified Fatty Acids on Dry Matter Intake in Developing Heifers and Mature Cows(North Dakota State University, 2022) Olorunkoya, SamuelThe objective of this experiment was to determine if nuclear magnetic resonance (NMR) profiles or blood metabolites could explain dry matter intake (DMI) in developing heifers and/or mature cows in the weeks leading to breeding. A total of 335 heifers and 60 cows were fed a forage-based diet. A general linear model (GLM) was fit for DMI using fixed effects; breed, frame size, birth year. Non-esterified fatty acids (NEFA) had the greatest association with DMI (R2 ranged from 54.4% to 58.1% and 64.4% to 70.6%) in heifers and cows, respectively. The NMR profiles accounted for the smallest amount of variation (51.9% and 55.6%) for rumen metabolism and (52.0% and 55.8%) for cellular metabolism in heifers and cows, respectively. Additional exploration of how to profile NMR data is needed. The models containing NEFA accounted for high levels of variation, where fit plots indicated these predictions could be used to manage animals in distinct groups for DMI.Item The Effects of Estrus on Dry Matter Intake and Feeding Behavior in Beef Heifers of Divergent Sizes(North Dakota State University, 2020) Underdahl, Sarah RoseThe biological process of estrus in cattle is known to initiate behavioral responses as a result of fluctuations in hormones, which may alter time budgeted for feeding. The current study aimed to quantify these variations that may exist in feed intake and behaviors in the days pre and post estrus. For this study, 517 estrous cycles in crossbred beef heifers of divergent sizes were used to analyze the impact of estrus behavior on feeding behavior with or without the presence of a bull. There were few differences in estrus behavior among heifers of divergent sizes, however the presence of a bull influenced all estrus activity parameters. Our findings indicate that feed intake and behaviors were sharply decreased on the day of estrus, but returned to baseline levels the following day. Thus, decreases in feed intake and behavior may serve as an additional tool indicating the onset of estrus.Item Understanding the Relationship Between Weather Variables, Dry Matter Intake, and Average Daily Gain of Beef Cattle(North Dakota State University, 2021) Yusuf, MustaphaThe current National Academies of Sciences, Engineering and Medicine (NASEM) dry matter intake (DMI) prediction models are inadequate for DMI prediction of beef cattle in the Northern Great Plains. Four studies were conducted to account for additional variation in DMI and average daily gain (ADG) caused by weather variables. Experiment 1 and 2 had 13,895 steer-weeks observations, experiment 3 had 13,739 steer-weeks observations, and experiment 4 had 2,161 cow-weeks observations, respectively. Experiment 1 examined the influence of ambient temperature and solar radiation on DMI of beef steers. In experiment 2, 3, and 4, we examined the influence of ambient temperature, range of temperature, dew point, solar radiation, wind speed and their lags (two-week lag and monthly lag) on DMI of beef steers, ADG of beef steers, and DMI of beef cows, respectively. After adjusting for week of the year, linear and quadratic relationships of predictor variables on response variables were evaluated. In experiment 1 and 2, body weight (BW) had both linear and quadratic relationship with DMI of steers. In experiment 3 and 4, BW had a linear relationship with ADG of steers and DMI of cows, respectively. Week of the year, BW, and dietary energy density (NEm) were accounted for in the base model in experiment 1, 2 and 4 while in experiment 3, DMI was also accounted for. For the models, stepwise regression procedure was utilized. In experiment 1, ambient temperature and solar radiation interacted (P = 0.0001) and accounted for additional variation in DMI of beef steers. In experiment 2, weather variables and their interactions (P = 0.0001) accounted for additional variation in DMI of beef steers. In experiment 3, weather variables (P = 0.0001) accounted for additional variation in ADG of beef steers. In experiment 4, wind speed interacted (P <0.001) with ambient temperature and range of temperature which all accounted for additional variation in DMI of beef cows. These studies show that weather variables interact and cause variation in DMI and ADG in beef cattle. This has helped in better understanding the relationship between weather variables with DMI and ADG. This will improve the accuracy of DMI and ADG prediction equations and help beef cattle producers in managing their feed resources more efficiently.