Residual feed intake, body composition and fertility in yearling beef heifers

One hundred thirty-seven spring born yearling beef heifers of English breed types were used to determine the relationships between residual feed intake (RFI) and growth rate, body composition, mature size, and fertility. Heifers were housed in a drylot facility during the trial and data were collected over a two-year period (year 1, n=67; year 2, n=70). Individual feed intake, body weight (BW), body condition score (BCS ), hip height (HH), and carcass ultrasound measurements (subcutaneous rib and rump fat; RIF and RUF, respectively, longissimus muscle area; LMA, and intramuscular fat; IMF ) were collected. Individual feed intakes were expressed as kg of TDN consumed per day and were used to calculate RFI combining both years\u27 data. Heifers averaged 387.0 +/- 19.4 days of age (DOA) and 337.1 +/- 29.9 kg BW at trial initiation. Mean average daily gain (ADG) was 1.14 +/- 0.21 kg/d. A slight relationship (P \u3c 0.05) existed between RFI and both RIF and RUF (r = 0.19 and 0.17, respectively) initially and was increased (r = 0.27 and r = 0.24, respectively; P \u3c 0.01) at trial conclusion. Heifers were classified into groups (POS; mean RFI=0.74 vs. NEG; -0.73 and HIGH; mean RFI=1.06, MEDIUM; -0.01, and LOW; -1.13) based on RFI (kg TDN/d), with year of test and farm of origin included in the model as covariates. POS heifers tended to possess more RIF (P = 0.051) and ribeye area (cm2) per hundred kg of BW (LMACWT) (P = 0.078) than NEG heifers at trial initiation, while LMACWT was greater in POS heifers at trial conclusion (P \u3c 0.01). POSITIVE heifers reached puberty earlier than NEG heifers (414 vs. 427 day, respectively, P = 0.03). MEDIUM heifers exhibited less RIF and RUF (P \u3c 0.05) when compared to either HIGH or LOW at trial initiation. LMACWT was less (P 0.10) from MEDIUM females at both beginning and end of test. A negative linear relationship existed between RFI and AGE at PUBERTY (P \u3c 0.05). Each one unit increase in RFI corresponded to a reduction of 7.54 days in AGE at PUBERTY; however, no differences existed between groups in pregnancy or conception rate. Given that RFI was significantly correlated with subcutaneous fat measures and the known relationship between fatness and reproductive maturity, further investigation is warranted

Identifying Potential Sources of Variation in Residual Feed Intake in Beef Cattle

Residual feed intake (RFI) class differences in gut function and grazing intake were evaluated using 14 crossbred steer progeny of first parity dams with known RFI phenotypes and a commercially available Angus sire. Steers were housed in a drylot facility and fed a forage based complete feed ad libitum, a forage diet at maintenance (1.5% BW as fed), and a concentrate diet at maintenance in Exp. 1, 4, and 5 respectively. Voluntary DMI and solid and liquid passage rate were evaluated while grazing (Exp. 2 and 3, respectively). Plasma concentrations of albumin (ALB), urea nitrogen (UN), cholesterol (CHOL), glucose (GLU), triglycerides (TG), and VFA were assessed immediately pre- and at 3 h intervals for 12 h post-feeding as indicators of nutrient absorption in Exp. 1, 4, and 5 respectively. Rumen pH, ammonia (NH4), and VFA were evaluated 12 h post-feeding. Steers were classified as either positive (POS; n = 8) or negative ( NEG; n = 6) according to dam RFI (mean 0.46 kg TND/d; range -4.27 to 5.70 kg TDN/d). Rumen pH, ammonia, and VFA\u27s did not differ based on RFI classification (P \u3e 0.05) in any of the experiments. Plasma metabolite and VFA concentrations did not differ between RFI classes in Experiment 1 (P \u3e 0.05); however, UN was greater in POS (12.80 vs. 12.14 mg/dL; P = 0.02) steers when fed a forage diet at maintenance (Exp. 4) and greater in NEG (16.74 vs. 15.42 mg/dL; P = 0.01) steers when fed a concentrate diet at maintenance (Exp 5). Plasma valerate and butyrate (P = 0.02 and 0.02, respectively) were greater in NEG steers in Exp. 1 and 5, respectively. Evaluation of RFI group differences by collection time revealed a significant (P = 0.04) interaction of RFI and Time for TG and plasma isobutyric acid in Exp. 1. Concentrations of TG were greater (P = 0.04) in NEG steers at 3 hours after feeding but did not differ at any other time points. Plasma isobutyric acid concentrations rarely differed from zero but were greater in POS steers 6 hours post-feeding. The opposite was true at 12 hours post-feeding. No other interactions between RFI and collection time were significant. Negative RFI steers consumed numerically 8.9% less DM per day while grazing than POS steers but did not differ in voluntary DMI (P = 0.74). Liquid passage rate was greater in NEG (7.16 vs. 6.32 % marker/hour; P = 0.04) steers but solid passage rate was not different (P = 0.88). These data indicate that RFI classification may be associated with variation in the regulation and absorptive capacity of the gastrointestinal tract

Analysis of Grade Variances in Multisection Calculus Classes

The purpose of this dissertation was to explore grade variances associated with multisection calculus grades. The method for the project was quantitative examining grade distribution patterns that existed between calculus sections at a public university void of an over-arching grading policy during the case study. Results showed that different grade distribution patterns by different instructors were primarily due to student-centric characteristics. The significant findings suggest that student grades are firmly in control of students. Only when course grade averages were at the extreme did evidence suggest that instructor-centric characteristics played meaningful role in student grade determination