Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets1,2

Abstract

ABSTRACT:A feedlot growth performance experiment and 2 metabolism experiments were conducted to evaluate dietary roughage concentration and calcium magnesium carbonate in steers fed a high-grain diet. In Exp. 1, one hundred ninety-two crossbred yearling steers (320 ± 10 kg of initial BW) were fed diets based on steam-flaked corn with 0, 0.75, or 1.5% CaMg(CO 3 ) 2 . There were no effects (P ≥ 0.13) on ADG, DMI, G:F, or total water intake due to CaMg(CO 3 ) 2 . In Exp. 2, five ruminally and duodenally fistulated steers (263 ± 9 kg of initial BW) were used in a 5 × 5 Latin square design, with 5 dietary treatments arranged in a 2 × 2 + 1 factorial: 1) 3.8% dietary roughage and no CaMg(CO 3 ) 2 ; 2) 7.6% dietary roughage and no CaMg(CO 3 ) 2 ; 3) 11.4% dietary roughage and no CaMg(CO 3 ) 2 ; 4) 3.8% dietary roughage and 1.5% CaMg(CO 3 ) 2 ; and 5) 7.6% dietary roughage and 1.5% CaMg(CO 3 ) 2 . Water consumption was less (quadratic, P = 0.003) when 7.6% dietary roughage was fed compared with 3.8 or 11.4% dietary roughage. Intake of DM was not affected (P ≥ 0.16) by dietary roughage or by CaMg(CO 3 ) 2 . Poststomach and total tract starch digestion decreased (linear, P < 0.01) as dietary roughage increased. Ruminal pH tended (P = 0.08) to increase as dietary roughage increased but was not affected (P = 0.60) by CaMg(CO 3 ) 2 . In Exp. 3, DMI and ruminal pH were continuously monitored in a 6 × 6 Latin square design using 6 ruminally and duodenally fistulated Holstein steers (229 ± 10 kg of initial BW). A 3 × 2 factorial treatment structure was utilized, with factors consisting of dietary roughage concentration (4.5, 9.0, or 13.5%) and CaMg(CO 3 ) 2 inclusion (0 or 1.0%) to replace MgO and partially replace limestone. A dietary roughage × CaMg(CO 3 ) 2 interaction (P = 0.01) occurred as steers consuming 13.5% roughage, 1.0% CaMg(CO 3 ) 2 had greater DMI per meal than those consuming 4.5% dietary roughage, no CaMg(CO 3 ) 2 and 9.0% dietary roughage, 1.0% CaMg(CO 3 ) 2 . Steers consuming 13.5% dietary roughage, 1.0% CaMg(CO 3 ) 2 and 9.0% dietary roughage, no CaMg(CO 3 ) 2 had greater meal length (min/meal; P = 0.01) than steers consuming 4.5% dietary roughage, no CaMg(CO 3 ) 2 . Total tract OM digestibility decreased linearly (P = 0.01), and ruminal pH increased linearly (P = 0.01) with increasing dietary roughage concentration. Inclusion of CaMg(CO 3 ) 2 can replace limestone and MgO but did not produce ruminal pH responses similar to those observed by increasing dietary roughage in high-concentrate diets.

Advancement in Assessment and the Reassessment of the Nutritive Value of Forages

“…6). This is expected based on earlier data reporting the successful direct prediction from NIR scans to estimate intake of DM or organic matter or digestible matter (Norris et al, 1976; Ward et al, 1982; Eckman et al, 1987; Coelho et al, 1988; Lippke and Barton, 1988; Lippke et al, 1989; Coleman et al, 1999) as well as daily animal gains (Lippke et al, 1989).…”

“…al., 2004). In their assessment and assessment by others (Shenk and Westerhaus, 1994; Coleman et al, 1999; Coleman et al, 2004) the traditional contrived fractions of NVAL were shown to be well predicted through proper calibration using near‐infrared technology. Technology advancement, however, is little served by this approach as the same inconsistencies of the NVAL fractions, relative to predicting animal response, still remain.…”

“…Such back prediction based on fecal scans has been assessed by Coleman et al (1999) and has utility in obtaining information on diet quality as well as estimates of daily DMI. It remains, however, that similar spectra information as found in the fecal samples exists for any forage, be it preserved or grazed and is present in the offered feed.…”

“…Information contained in the spectra has been shown to have potential to forward predict animal responses. Based on today's advances in instrumentation (near‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, microspectrophotometry, and the more destructive technique of mass spectroscopy and pyrolysis), when applied in combination with greater data processing capabilities, reduces previously noted stumbling blocks (Coleman et al, 1999) for direct spectral prediction of animal daily responses.…”

“…Milestones leading toward technology advancement in the assessment of the “particle value” of forages are as follows: • Become knowledgeable about spectral procedures and methods that capture the chemical nature (chemometrics) of particles (Coleman et al, 1999). • Formulate a plan with the objective to capture the compositional information over the total near‐infrared spectra of plant constituents (forage, pasture, hay, silage, and ration components) for direct prediction of animal responses (Windham and Coleman, 1989). • Generate one‐on‐one discussions with individuals having specific expertise regarding forage, animal, physics, data processing, and data analysis. • Form a team of these individuals, each with unique expertise and interest, to focus on the shared common goal of spectral application to forage quality (Burns et al, 1988).…”