A. Plascencia

Effects of preslaughter withdrawal period on response of feedlot heifers to zilpaterol hydrochloride supplementation: growth performance and carcass characteristics.

Sixty-four crossbred heifers (451 +/- 23 kg) were used in a 42-d feeding trial (4 pens per treatment in a randomized complete block design) to evaluate the influence of preslaughter zilpaterol hydrochloride withdrawal period on growth performance and carcass characteristics. Heifers were fed a diet based on steam-flaked corn (2.13 Mcal of NE(m)/kg). Treatments were 1) control, no zilpaterol supplementation; 2) zilpaterol supplementation for 30 d, drug withdrawn from the diet 3 d preslaughter (ZIL-3); 3) zilpaterol supplementation for 30 d, drug withdrawn 6 d preslaughter (ZIL-6), and 4) zilpaterol supplementation for 30 d, drug withdrawn 12 d preslaughter (ZIL-12). Zilpaterol was supplemented at the rate of 0.15 mg/kg of BW daily. Intake of DM averaged 9.2 +/- 0.26 kg/d and was not affected (P > or = 0.36) by treatment. Compared with control heifers, ZIL-3 increased (P < 0.01) carcass-adjusted ADG (59%), G:F (57%), apparent dietary NE(m) (31%), and decreased observed/expected DMI (25%). Treatment with ZIL-3 did not affect marbling score (P = 0.49) or backfat thickness (P = 0.17), but compared with the control group, increased HCW (3.6%, P = 0.03), carcass dressing percentage (3.2%, P = 0.02), LM area (6.3%, P = 0.05), and reduced trimmed fat (31%, P = 0.03). Prolonging the period of zilpaterol withdrawal preslaughter tended to decrease carcass-adjusted ADG (linear, P = 0.11), G:F (linear, P = 0.08), apparent dietary NE(m) (linear, P = 0.11), and carcass dressing percentage (linear, P = 0.11). We conclude that growth performance and carcass yield responses to zilpaterol supplementation are negatively affected by prolonging the period of zilpaterol withdrawal beyond 3 d (the required minimum withdrawal period according to label). Drug withdrawal period may be a relevant factor in explaining variation in performance response to zilpaterol supplementation in commercial feedlots.

Influence of processing method on comparative digestion of white corn versus conventional steam-flaked yellow dent corn in finishing diets for feedlot cattle

Four Holstein steers (137 ± 2 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square design to evaluate the influence of processing method on comparative digestion of white corn. Treatments consisted of a basal finishing diet containing 80% corn grain (DM basis) as 1) dry-rolled white corn (DRWC), 2) steam-flaked white corn (SFWC) with 0.36 kg/L flake density (SFWC36), 3) SFWC, 0.31 kg/L flake density (SFWC31), and 4) steam-flaked yellow corn (SFYC) with 0.31 kg/L flake density (SFYC31). Characteristics of ruminal, postruminal, and apparent total tract digestion of OM, starch, and N were similar (P ≥ 0.08) for SFYC31 and SFWC31 treatments. Decreasing flake density of white corn (from 0.36 to 0.31 kg/L) did not affect (P = 0.22) ruminal OM digestion, but increased (1.9%, P = 0.07) apparent total tract OM digestion. Compared with dry rolling, steam flaking white corn increased ruminal (9.4%, P = 0.05), postruminal (14.4%, P < 0.01), and apparent total tract OM digestion (8.2%, P < 0.01), reflecting corresponding increases in ruminal (13.3%, P < 0.01), postruminal (43%, P < 0.01), and apparent total tract (12.3%, P < 0.01) starch digestion. Apparent postruminal and apparent total-tract N digestion also were greater (6.5 and 5.6%, respectively, P = 0.04) for SFWC than for DRWC. The DE value of SFWC and SFYC diets was similar, averaging 3.39 Mcal/kg. The DE value of SFWC was greater (8.1%, P < 0.01) than that of DRWC. Ruminal pH (4 h postprandial) averaged 5.74 and was not affected (P ≥ 0.48) by dietary treatments. Compared with dry rolling, steam flaking markedly enhances the feeding value of white corn, with optimal flake density being less than 0.36 kg/L. Although white corn has greater vitreous endosperm content, characteristics of ruminal starch digestion and undegradable intake protein are similar to conventional yellow dent corn when processed to a similar flake density (0.31 kg/L). However, postruminal and apparent total tract starch digestion tends to be slightly less for flaked white corn than for yellow corn.

Influence of protein and energy level in finishing diets for feedlot hair lambs: growth performance, dietary energetics and carcass characteristics.

Forty-eight Pelibuey×Katahdin male intact lambs (23.87±2.84 kg) were used in an 84-d feeding trial, with six pens per treatment in a 2×2 factorial design arrangement. The aim of the study was to evaluate the interaction of two dietary energy levels (3.05 and 2.83 Mcal/kg ME) and two dietary protein levels (17.5% and 14.5%) on growth performance, dietary energetics and carcass traits. The dietary treatments used were: i) High protein-high energy (HP-HE); ii) High protein-low energy (HP-LE); iii) Low protein-high energy (LP-HE), and iv) Low protein-low energy (LP-LE). With a high-energy level, dry matter intake (DMI) values were 6.1% lower in the low-protein diets, while with low-energy, the DMI values did not differ between the dietary protein levels. Energy levels did not influence the final weight and average daily gain (ADG), but resulted in lower DMI values and higher gain efficiencies. No effects of protein level were detected on growth performance. The observed dietary net energy (NE) ratio and observed DMI were closer than expected in all treatments and were not affected by the different treatments. There was an interaction (p<0.03) between energy and protein level for kidney-pelvic and heart fat (KPH), KPH was higher in lambs fed high energy and high protein diet but not in high energy and low protein diet. The KPH was increased (20.2%, p = 0.01) in high-energy diets, while fat thickness was increased (21.7%, p = 0.02) in high-protein diets. Therefore, it is concluded that dietary energy levels play a more important role in feed efficiency than protein levels in finishing lambs with a high-energy diet (>2.80 Mcal/kg ME). Providing a level of protein above 14.5% does not improves growth-performance, dietary energetics or carcass dressing percentage.

Effects of feeding different levels of chromium-enriched live yeast in hairy lambs fed a corn-based diet: effects on growth performance, dietary energetics, carcass traits and visceral organ mass

Forty Pelibuey ·Kathdin lambs (35.5 � 0.4 kg) were used in a 56-day feeding experiment to assess the effects of feeding different levels of chromium-enriched live yeast (Cr-YC) on growth performance, dietary energetics, carcass traits and visceral organ mass. The Cr-YC source contained 5.5 · 10 9 colony forming units (CFU) and 0.40 mg of Cr per gram.Treatmentsconsistedofadryrolledcorn-based finishingdietsupplementedwith0,1,2or3gCr-YC/lamb.day.Total daily dosages were: 5.5 · 10 9 CFU and 0.4 mg; 1.1 · 10 10 CFU and 0.8 mg Cr, and 1.65 · 10 10 CFU and 1.2 mg Cr for supplementationlevelsof1,2or3gCr-YC/lamb.day,respectively.Therewerenotreatmentseffectsondrymatterintake.As thelevelofCr-YCsupplementationincreased,averagedailygain,gaintofeedanddietarynetenergywerelinearlyincreased, and observed/expected dry matter intake was linearly decreased. Chromium-enriched live yeast supplementation increased emptybodyweight(EBW),gastrointestinal fillandfullvisceraweight,butdidnotinfluenceorganweightsasaproportionof EBW (g/kg EBW). Cr-YC level did not affect carcass length, backfat thickness, kidney, pelvic and heart fat or body wall thickness,butincreasedhotcarcassweightandlongissimusmusclearea.Ingeneral,treatmenteffectsonpercentageyieldof wholesale cuts (tissue weight as a percentage of cold carcass weight) were small. However, Cr-YC decreased percentage flank. Chromium-enriched yeast supplementation enhances growth rate, longissimus muscle area, and dietary energetic efficiency in finishing feedlot lambs.

Effect of level and source of supplemental tannin on growth performance of steers during the late finishing phase

ABSTRACT Two trials were conducted to evaluate the effect of tannin supplementation of steers during the feedlot finishing phase. In Trial 1, 96 Holstein steers (478 ± 6.5 kg) were used to evaluate the effects of level of supplemental condensed tannin (0%, 0.2%, 0.4%, and 0.6% of dry matter basis) on growth performance. Supplemental tannin increased (6.5%, P = 0.05) weight gain, gain efficiency (5.5%, P = 0.04), and tended to increase dietary net energy (3.2%, P = 0.06). In Trial 2, 96 Holstein steers (392 ± 4 kg) were used to evaluate the effect of tannin sources on growth performance. Treatments consisted of a steam-flaked corn diet supplemented with (1) no supplemental tannin, (2) 0.6% condensed tannin, (3) 0.6% hydrolysable tannin, and (4) a blend of 0.3% condensed and 0.3% hydrolysable tannin. Tannin supplementation tended to increase average daily gain (ADG, 6.8%, P = 0.08) and dry matter intake (DMI, 4%, P = 0.04). It is concluded that tannin supplementation promotes greater DMI, and hence, ADG of steers during the finishing feedlot phase. The basis for this effect on feed intake is not certain, but is apparently independent of potential tannin effects on metabolizable protein supply. Source of supplemental tannin (condensed vs. hydrolysable) have minimal effects on overall growth performance response to supplementation.

Effect of Variation in Supplement Inclusion Rate and Laidlomycin Propionate on Growth Performance of Feedlot Cattle

Abstract Montano, M.F., Loya-Olguin, J.L., Plascencia, A., Salinas Chavira, J. and Zinn, R.A. 2010. Effect of variation in supplement inclusion rate and laidlomycin propionate on growth performance of feedlot cattle. J. Appl. Anim. Res., 37: 83–87. One hundred twelve yearling steers (364±3.4 kg) were used in a 123-d finishing trial to evaluate the interaction of laidlomycin propionate and variation in supplement inclusion rate on growth performance and carcass characteristics. Two levels of laidlomycin propionate (0 vs. 10 mg/kg) and two levels of variation in daily supplement (12 g urea, 18 g limestone, 2 g Mg02 and 5 g trace mineralized salt) inclusion rate (O vs 20% coefficient of variation) were evaluated in a 2x2 factorial arrangement. Variation was produced by altering the inclusion rate of the supplement portion of the diet to achieve a 20% CV in supplement concentration of the complete mixed, as follows: on d 1 and 5 of each week the diet contained 125% of the specified amount of supplement; on d 2, 4 and 6 the diet contained 100% of the specified amount of supplement; on d 3 and 7 the diet contained 75% of the specified amount of supplement. There were no treatment interactions (P<0.20). Variation in supplement inclusion rate decreased ADG (8%, P<0.05), gain efficiency (G:F; 5%, P<0.01), dietary NEm (2.3%, P<0.01) and dietary NEg (3.3%, P<0.01). Supplemental laidlomycin tended to increase ADG (6%, P=0.19), but did not affect (P<0.20) gain efficiency or dietary NE. There were no treatment effects (P<0.20) on carcass characteristics. It is concluded that variation in supplement inclusion may depress growth performance of feedlot cattle, attributable to reduction in both energetic efficiency and DMI.

Evaluation of isoquinoline alkaloid supplementation levels on ruminal fermentation, characteristics of digestion, and microbial protein synthesis in steers fed a high-energy diet

Four Holstein steers with ruminal and duodenal cannulas were used in a 4 × 4 Latin square design to examine the effect of daily intake of 0, 2, 4 or 6 g/steer of standardized plant extract containing a mixture of quaternary benzophenanthridine alkaloids and protopine alkaloids (QBA+PA) on the characteristics of ruminal fermentation and characteristics of digestion. The basal diet consisted of a steam-flaked corn-based finishing diet that contained 62% corn and 12% sudangrass hay and the rest of diet was composed of mainly dried distillers grains, molasses, fat, and minerals. The source of QBA+PA used was Sangrovit-RS (Phytobiotics Futterzusatzstoffe GmbH, Eltville, Germany) and supplementation levels of 2, 4, and 6 g Sangrovit-RS∙steer∙d, which represented a net daily ingestion of approximately 6, 12, and 18 mg of QBA+PA compounds, respectively. Inclusion of QBA+PA linearly increased ( = 0.04) flow to the duodenum of nonammonia N and linearly decreased ( < 0.01) duodenal flows of ammonia N. Ruminal microbial efficiency (duodenal microbial N; g/kg OM fermented in the rumen) and protein efficiency (duodenal nonammonia N; g/g N intake) were increased ( < 0.05) as the level of QBA+PA increased. There were no effects of QBA+PA supplementation on ruminal, postruminal, and total tract digestion of OM, starch, and NDF, but postruminal and total tract digestion of N increased ( < 0.01) as the level of QBA+PA increased. Digestible energy of the diet tended to increase (linear affect, = 0.09) with QBA+PA supplementation. Ruminal pH and total VFA molar concentrations were not different between treatments. Ruminal NH-N concentration linearly decreased ( = 0.02) with QBA+PA supplementation. Ruminal molar proportion of acetate increased ( = 0.04) as the supplementation level of QBA+PA increased. It is concluded that QBA+PA supplementation enhances efficiency of N utilization in feedlot steers fed a steam-flaked corn-based finishing diet. This effect was due, in part, to enhanced ruminal microbial efficiency, decreased ruminal degradation of dietary nonammonia N, and enhanced postruminal N digestion.

Effects of Combining Feed Grade Urea and a Slow-release Urea Product on Characteristics of Digestion, Microbial Protein Synthesis and Digestible Energy in Steers Fed Diets with Different Starch:ADF Ratios

As a result of the cost of grains, the replacement of grains by co-products (i.e. DDGS) in feedlot diets is a common practice. This change produces diets that contain a lower amount of starch and greater amount of fibre. Hypothetically, combining feed grade urea (U) with slow release urea (Optigen) in this type of diet should elicit a better synchrony between starch (high-rate of digestion) and fibre (low-rate of digestion) promoting a better microbial protein synthesis and ruminal digestion with increasing the digestible energy of the diet. Four cannulated Holstein steers (213±4 kg) were used in a 4×4 Latin square design to examine the combination of Optigen and U in a finishing diet containing different starch:acid detergent fibre ratios (S:F) on the characteristics of digestive function. Three S:F ratios (3.0, 4.5, and 6.0) were tested using a combination of U (0.80%) and Optigen (1.0%). Additionally, a treatment of 4.5 S:F ratio with urea (0.80% in ration) as the sole source of non-protein nitrogen was used to compare the effect of urea combination at same S:F ratio. The S:F ratio of the diet was manipulated by replacing the corn grain by dried distillers grain with solubles and roughage. Urea combination did not affect ruminal pH. The S:F ratio did not affect ruminal pH at 0 and 2 h post-feeding but, at 4 and 6 h, the ruminal pH decreased as the S:F ratio increased (linear, p<0.05). Ruminal digestion of OM, starch and feed N were not affected by urea combination or S:F ratio. The urea combination did not affect ADF ruminal digestion. ADF ruminal digestion decreased linearly (p = 0.02) as the S:F ratio increased. Compared to the urea treatment (p<0.05) and within the urea combination treatment (quadratic, p<0.01), the flow of microbial nitrogen (MN) to the small intestine and ruminal microbial efficiency were greater for the urea combination at a S:F ratio of 4.5. Irrespective of the S:F ratio, the urea combination improved (2.8%, p = 0.02) postruminal N digestion. As S:F ratio increased, OM digestion increased, but ADF total tract digestion decreased. The combination of urea at 4.5 S:F improved (2%, p = 0.04) the digestible energy (DE) more than expected. Combining urea and Optigen resulted in positive effects on the MN flow and DE of the diet, but apparently these advantages are observed only when there is a certain proportion of starch:ADF in the diet.

Influence of protein nutrition and virginiamycin supplementation on feedlot growth performance and digestive function of calf-fed Holstein steers

Two experiments were conducted to examine the influence of protein and virginiamycin (VM) supplementation on feedlot growth performance, digestion, and metabolizable AA (MAA) supply of calf-fed Holstein steers. Growth performance and dietary energetics were evaluated in 120 Holstein steers (127 ± 9 kg). During the initial 112-d feeding period, a steam-flaked corn-based diet was balanced to meet either 100% (MAB) or 87% (UREA) of MAA requirements. Diets were supplemented with or without 22.5 mg/kg VM in a 2 × 2 factorial arrangement. Subsequently (d 112 to 308), all steers received the UREA diet with or without VM. During the initial 112-d, MAB increased ADG, G:F, and dietary NE ( < 0.01). Thereafter, when all steers received the UREA diet, ADG, G:F, and dietary NE were not different ( > 0.10) across initial supplementation treatments. Overall (d 1 to 308), MAB did not affect ADG ( > 0.10) but enhanced G:F efficiency ( = 0.03) and dietary NE ( = 0.05). During the initial 112-d period and through the remainder of the experiment, VM increased G:F ( < 0.01) and dietary NE ( < 0.01). Four Holstein steers (146 ± 4 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square design to evaluate initial 112-d treatment effects on digestive function. There were no treatment effects ( > 0.10) on ruminal digestion of OM, NDF, starch, microbial efficiency, or total tract digestion of OM and NDF. The MAB increased indispensable AA flow to the small intestine ( < 0.01) and total tract digestion of N ( < 0.01) and starch ( = 0.04). Observed AA supply to small intestine was in agreement with expected supply ( = 0.96). Virginiamycin decreased ( = 0.04) nonammonia N flow to the small intestine and did not affect ( > 0.10) total tract N digestion. Extrapolating from AA supplies in the metabolism study, MAB satisfied indispensable AA requirements during the initial 112-d period, whereas the UREA diet met 73.5% and 79.2% of methionine and lysine requirements, respectively. During the subsequent periods (d 112 to 308) indispensable AA supplies exceeded theoretical requirements. We conclude that enhancements in energy utilization when diets are balanced to meet MAA requirements of calf-fed Holstein steers during the initial 112-d feedlot period remain appreciable throughout time on feed. Virginiamycin enhanced efficiency of energy utilization throughout the feedlot growing-finishing period.

Influence of feeding chromium-enriched enzymatically hydrolyzed yeast on growth performance, dietary energetics and carcass characteristics in feedlot cattle under conditions of high ambient temperature

Forty crossbred steers (245 ± 0.95 kg) were used in a 222-day feeding trial to assess the effects of a supplementation of chelated chromium-enhanced extract of enzymatically hydrolyzed yeast (Cr-EHY) on growth performance, dietary energetics and carcass characteristics in feedlot cattle finishing during high ambient temperatures. Treatments consisted of a steam-flaked corn-based diets supplemented with 0 or 0.4 g/kg of diet with Cr-EHY (0.3 g/kg of TruMax plus 0.1 g/kg of chelated Cr). Both dry matter intake (DMI) and climatic variables were measured weekly and the temperature humidity index (THI) was estimated. Daily maximal THI that exceeding a THI value of 72 was reached in 213 of the 222-day study (avg. THI = 75.24). During the initial 112-day period (including the receiving and diet transition phases), Cr-EHY increased average daily gain (ADG) (7%, P = 0.03). This effect was due to a tendency (P = 0.07) for increased DMI. There were no treatment effects on gain efficiency and dietary net energy (NE). Overall, however, there were no treatment effects on growth performance or dietary NE. Nevertheless, Cr-EHY supplementation had a modulating effect on carcass quality, decreasing carcass fat thickness (10%, P = 0.09, and increasing longissimus muscle area (7%, P < 0.01) and retail yield of boneless closely trimmed primal cuts (2%, P = 0.07). Results indicate that supplementation with a chelated chromium-enhanced extract of enzymatically hydrolyzed yeast can have beneficial effects on feed intake and daily weight gain, particularly during the initial receiving growing phase. It also appears to have a modulating effect on carcass quality, enhancing muscularity and reducing external fat. These results indicate that Cr supplementation has a modulating effect on carcass quality and may enhance DMI and corresponding ADG of feedlot cattle during periods of high ambient temperature.