Physiological traits that are biologically associated with feed efficiency may be useful indicator traits residual feed intake (RFI). The objective of this study was to examine the relationships between RFI, temperament, serum hormones and serum metabolites in growing heifers. A 4 yr study (n = 114-119 heifers/yr) was conducted with Brangus heifers (Initial BW = 271 ± 26 kg) that were weaned for 25.5 ± 8.6 d prior to high roughage diet adaptation (ME = 2.0 Mcal/kg DM). Individual dry matter intakes (DMI) were measured using Calan gate feeders and BW measured at 7-d intervals during the 70-d studies. RFI was calculated as the residual from the linear regression of DMI on mid-test BW0.75 and average daily gain (ADG). Temperament scores and exit velocity (EV) were taken at 0-d. Temperament index (TI) was calculated as the average of EV and chute score. On 0-d, blood samples were collected and assayed for partial blood counts (WBC, RBC, hemoglobin, HB), metabolites (total protein, TP; glucose; creatinine; blood urea nitrogen, BUN; β-hydroxybutyrate, BHB) and hormones (cortisol; insulin-like growth hormone I, IGF-I). Across all heifers, RFI was positively correlated with DMI (0.70) and feed:gain (0.59). Heifers with low RFI (< 0.5 SD from mean RFI 0.00 ± 0.71 kg/d) consumed 16 percent less DMI and had 16 percent lower feed:gain than heifers with high RFI (> 0.50 SD from mean RFI). RFI was weakly correlated (P < 0.05) with WBC (0.15), HB (-0.11), total protein (-0.10), BUN (0.10), creatinine (-0.11) and BHB (0.13). Hemoglobin and BHB were weakly correlated with all feed efficiency traits except feed conversion ratio (FCR). No phenotypic correlation was found between cortisol and IGF-I with RFI. Temperament was not correlated with RFI. Cortisol, creatinine and glucose were moderately correlated with all temperament traits. Low TI heifers (calm) had significantly higher Final BW, ADG and DMI than high TI heifers. Calm animals had significantly lower cortisol, HB, creatinine and glucose and higher BHB. These results suggest that the temperament and serum metabolites evaluated in this study have limited utility as indicator traits for RFI in growing heifers.

MSCAGR (Animal Science) / Department of Animal Science / The study evaluated the nutritive value of orange pulp- buffalo grass (OPBG) silage as a po-tential pig feed. In experiment 1, OPBG was ensiled in 58 one-litre jars, split into Reno-zyme® enzymes (containing α-amylases and β-endo 1, 3; 1, 4 beta glucanase) (denoted OPBGE) and 18 without enzyme (denoted OPBG). Samples were collected from the lab on days 7, 15 and 30 in a three by two factorial design (period by treatment). In Experiment 2, 12 South African Windsnyer-type (SAWIP) (27.2±3.9 kg) and 12 Large White- Landrace crosses (LW x LR) (28±9.8 kg) were fed diets containing different levels of bulk-ensiled OPBG ad libitum for 30 days, in a 2 X 3 (breed by level of OPBG (control, low (15% OPBG) and high (30% OPBG))) factorial arrangement. The apparent total tract digestibility (ATTD) of the pigs was measured during week 3 of feeding. The average body gain ABG average daily feed intake (ADFI), average daily gain (ADG), average gain to feed ratio (AG: F) were measured weekly. Serum glucose (GLU) , blood urea nitrogen (BUN), creatinine (CREAT), cholesterol, (CHOL) and triglycerides (TG) were measured during week 4 of the experiment. The levels of CP, EE, NDF, water soluble carbohydrates (WSC), lactic acid (LA) and pH were different (P<0.05) for OPBGE and OPBG on day 7. However the OPBGE concentra-tions of DM, ASH, CP, NDF, HEMI, WSC, LA and pH were higher (P<0.05) compared to OPBG. The OPBGE was lower (P<0.05) on EE and ADF, compared to OPBG on day 7. The levels of DM, ASH, CP, NDF, ADF, HEMI, LA and WSC were different (P<0.05) for OPBGE and OPBG on day 30. However the OPBGE levels of DM, CP, NDF, ADF, LA and WSC were higher (P<0.05) compared to OPBG. ASH, EE and HEMI were lower (P<0.05) on day 30. There were significant diets x day interactions (P<0.05) for DM, ASH, CP, EE, NDF, ADF, HEMI, WSC, and LA, but not for pH. The aerobic stability study was inconclusive. The digestibility levels of OM and NDF were different (P<0.05) for LW x LR and SAWIP, where LW x LR ATTD on OM and NDF was higher (P<0.05) compared to SAWIP for all diets. The LW x LR ADG was higher (P<0.05) compared to SAWIP for all diets. There was a diet x breed interaction effect (P <0.05) on ADG whereby the BUN and CREAT were different (P <0.05) for LW x LR and SAWIP. The SAWIP BUN was higher (P<0.05), but the CREAT and TG were lower (P<0.05) compared to LW x LR for all diets fed. In conclusion, OPBG inclu-sion in pig feed enhanced the quality of feed, digestibility, performance and blood metabo-lites profile. / NRF