Nitrogen Utilization in Ruminants Consuming High Quality Fresh Forages

Experiments were conducted to study crude protein (CP) and dry matter (DM) composition of fresh forages of different species and maturities, and to determine the effect of supplementation on forage CP and OM digestion by steers. Experiment 1, a randomized complete block (RCB) design, utilized four forages (alfalfa, bromegrass, and endophyte-free and endophyte-infected tall fescue, TF) cut at 11 dates of harvest during Spring 1994 and 1995. Forage maturity did not override the differences due to species from vegetative to reproductive stages. Fresh alfalfa (ALF) in vegetative, early bud, early flowering, and late flowering stages, and bromegrass, and endophyte free and infected TF (tillering, stem elongation, heading, and flowering stages) were evaluated for ruminal DM and CP degradation kinetics. Maturity within forage species had a greater effect than species on ruminal DM and CP degradation. Experiment 2, 168 Angus steers (246.8 $\pm$ 15.0 kg) grazed the primary growth of TF alone (C) or supplemented with 1.4 kg/d cracked corn (CC), 1.4 kg/d corn gluten feed (CGF), 2.8 kg/d CC, 2.8 kg/d CGF, or 1.4 kg/d of corn starch and corn gluten meal (CS-CGM) in a RCB design. Supplemented steers had higher (P =.03) average daily gains (ADG) than C steers (.74 vs.64 kg/d). Four Angus x Simmental steers (412 $\pm$ 20.4 kg) cannulated in the esophagus, rumen, and duodenum grazed TF (C), C + 3.1 kg/d CGF, C + 3.1 kg/d CC, or C + 1.4 kg/d CS-CGM in a Latin square design (LSD). Forage OM intakes (OMI) were lower $(P < .05)$ for steers supplemented with CC or CGF (average: 7.6 kg/d) than in C (9.7 kg/d) but total OM intake (TOMI), ruminal fermentation or OM digestion were not affected by supplements. Experiment 3, six Angus steers (338 $\pm$ 19 kg) cannulated in rumen, duodenum, and ileum were fed the following treatments indoors: ALF ad libitum (AALF), AALF and S with.4,.8, or 1.2% of BW of CC, or ALF restricted at the average level of FI of S steers (RALF), in a LSD. Forage OMI was decreased $(P < .01)$ linearly but TOMI, and total tract OM digestibility were increased $(P < .05)$ linearly by CC. Supplementation decreased $(P < .01)$ linearly CP intake and ruminal CP degradability, and increased $(P < .01)$ linearly the duodenal flows and small intestinal disappearance of amino acids. It was possible to improve CP utilization of fresh forages by using CC but not through forage maturity without decreasing forage quality.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Elizalde, Juan Carlos

Contributors dc:contributor

• Merchen, Neal R.

• Biology, Animal Physiology

Language dc:language

eng

Identifier

(MiAaPQ)AAI9904445

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83642