C. W. Hunt

Factors affecting the feeding quality of barley for ruminants

Abstract Variation in the nutritive value of barley is well documented. Although bulk density is a convenient means of evaluating barley, it does not fully account for differences observed in animal performance from feeding different sources of barley. Recent data indicate that starch and (or) fiber content may be more reliable criteria for evaluating sources of barley. As progress has been made toward higher starch content and plumper barley, greater attention should be given to proper processing of barley before feeding. Improper processing might well negate potential improvements expected from higher-quality barley.

Effect of barley and its amylopectin content on ruminal fermentation and bacterial utilization of ammonia-N in vitro

The objective of this study was to determine the effect of variety and amylopectin content of barley on ruminal fermentation and ammonia-N utilization by mixed ruminal bacteria in vitro. Three barley varieties (WestBred Gustoe, Nebula, Baronesse) and their waxy counterparts were tested. The control grain was corn. All barley varieties were examined at three substitution levels: 25, 50, and 75% with the remaining being corn. Ammonia-N was labeled with 15 N-ammonium sulfate. Samples were collected at 0, 2, 4, 6, and 8 h. Barley inclusion enhanced (P < 0.05) propionate production and total VFA at the 75% substitution level and, at 8 h, increasing the proportion of barley in the grain mix increased (P < 0.05, linear effect) propionate concentration and decreased (P < 0.05, linear effect) acetate to propionate ratio. Across sampling points, the waxy variety of WestBred Gustoe resulted in higher (P < 0.05) fluid bacteria incorporation of ammonia-N than corn (by 7.6 and 11.9%, 25 and 75% substitution levels, respectively). At the 75% substitution level, waxy barleys resulted in an 8% higher (P < 0.01) ammonia- 15 N incorporation into bacterial N than their non-waxy counterparts. At the end-point of the incubation, barley treatments and waxy barleys had higher (P < 0.05) 15 N-enrichment of the fluid bacterial N compared with corn and non-waxy barleys, respectively. The combined (fluid- and particle-associated bacteria and protozoa) microbial ammonia-N uptake, however, was not different between corn control and treatments with barley. Results suggest that ruminal responses to barley supplementation may vary depending on its variety and starch composition and differ between fluid- and particle-associated microorganisms.

Effect of preslaughter feeding and ractopamine hydrochloride supplementation on growth performance, carcass characteristics, and end product quality in market dairy cows

An experiment was conducted in market dairy cows to determine the effect of feeding time and ractopamine hydrochloride (RAC) on growth performance, carcass characteristics, and end product quality. In 3 replicates, 9 Holstein cows per replicate (n = 27; 659 +/- 25.3 kg initial BW) culled from 3 dairies were randomly assigned to 3 treatments: 1) slaughter immediately (control), 2) feed for 90 d (NoR), or 3) feed for 90 d with RAC (312 mg.cow(-1).d(-1)) for the final 32 d (RAC). On d 0, NoR and RAC cows were placed in individual pens and fed a high concentrate diet (86% concentrate, DM basis) for 90 d before slaughter. All cows were subjectively scored for BCS and locomotion score on d 0, and NoR and RAC cows were evaluated again after 90 d. Individual DMI was recorded daily throughout the trial, and BW was collected every 14 d. Age and age x treatment did not affect (P > 0.05) any of the traits evaluated in this study. When cows fed for 90 d (NoR and RAC combined) were compared with nonfed controls, fed cows had greater (P < 0.001) final BCS, BW and HCW, lower (P < 0.001) final locomotion score, and greater (P < 0.03) dressing percentage, external fat thickness, and marbling score. Fed cows also tended to have more desirable yield grade (P = 0.08), ribeye area (P = 0.11), fat color (P = 0.09), lean maturity (P = 0.06), and quality grade (P = 0.09) compared with control cows. Warner-Bratzler shear force was not affected (P = 0.23) by feeding. However, a 12-member trained sensory panel revealed that fed cow carcasses had more desirable (P < 0.04) tenderness, juiciness, and overall acceptability than control cow carcasses. Flavor intensity also tended (P = 0.10) to be more desirable for fed vs. control cows. No difference (P > 0.10) in off-flavor was detected among treatments. Finally, there was no effect (P > 0.10) of RAC on growth performance, carcass characteristics, or end product quality. In conclusion, feeding a high concentrate diet for 90 d improved important live animal, carcass, and end product characteristics related to the quality and palatability of beef from market dairy cows; however, no effect of RAC supplementation was observed.

Relationship between residual feed intake and end product palatability in longissimus steaks from steers sired by Angus bulls divergent for intramuscular fat expected progeny difference1

ABSTRACT The relationship between residual feed intake (RFI) and end product quality was evaluated in 133 steers from 5 Angus sires with low, moderate, or high percent intramuscular fat EPD. Steers (320.1 ± 35.76 kg) were evaluated for RFI during a 70- to 84-d growing period and classified into 3 groups based on RFI: efficient (less than -0.5 SD below the mean; n = 41), marginal (±xa00.5 SD from the mean; n = 48), and inefficient (>xa00.5 SD above the mean; n = 44). There were no differences among RFI groups for ADG, BW, fat thickness, carcass weight, YG, QG, or palatability traits. Inefficient steers had greater (P

Relationship Between Quality Characteristics of Barley Grain and Digestibility in Feedlot Steers

Two hundred forty-nine samples of barley grain representing varieties from 13 growing locations were obtained to evaluate variability in nutritive value and to characterize the relationship between chemical composition and digestibility. Ranges for barley NDF, ADF, starch, bulk density (BD), and in vitro total digestibility (IVTD) were 11.8 to 25.6%, 2.2 to 8.8%, 48.2 to 72.5%, 569 to 784 g/L (44 to 61 lb/bu), and 66.7 to 85.1%, respectively. In vitro total digestibility was most closely related to NDF (r = −0.69, P < 0.001); this relationship improved when correlation was determined by variety (r = −0.81; P < 0.001) and location (r = −0.93, P < 0.001). Thirty-two steers were then adapted to a diet consisting of 80% dry-rolled barley (DM basis) from 1 of 8 divergent sources. Steers were assigned randomly to the 8 dietary treatments and in vivo digestibility was measured during 3 experiments replicated over time. Digestibility of DM, OM, and starch were not different between barley sources. Using least squares means for laboratory measures of the 8 sources of barley, NDF was negatively correlated with starch (r = −0.83, P < 0.05) and IVTD (r = −0.87; P < 0.05). Starch was positively correlated with BD and IVTD (r = 0.71 and 0.83, respectively; P < 0.05), and BD was positively correlated with IVTD (r = 0.83; P < 0.05). None of the laboratory variables measured in this study was an adequate predictor of barley digestibility from the digestive tract of feedlot steers.

Effect of Degradable Intake Protein Level on Performance of Feedlot Steers Fed Dry-Rolled Corn- or Barley-Based Finishing Diets

Abstract The effects of grain type (corn and barley) and level of degradable intake protein (DIP) on the performance of finishing steers was evaluated using 240 beef steers (BW = 381 kg) in a randomized block design with a 2 × 3 factorial arrangement of treatments, which included corn- or barley-based finishing diets formulated to contain 11.5, 12.75, or 14% CP (DM basis). Soybean meal and urea were used as the protein sources. No differences were detected ( P > 0.05) between treatments for initial BW, days on feed, or internal fat. Corn-fed steers had greater ( P P P P > 0.05) of DIP level was detected for final BW and feed conversion. A grain type × DIP level interaction was detected for DMI. As DIP level increased in the barley diet, there was a quadratic effect on DMI ( P P