The objective of this study was to examine the relationships among ruminal microbial community, rumen morphometrics, feeding behavior, feedlot performance, and carcass characteristics of Nellore cattle, classified by residual feed intake (RFI). Twenty-seven Nellore yearling bulls with an initial body weight (BW) of 423.84 ± 21.81 kg were fed in feedlot for 107 d in individual pens to determine the RFI phenotype. Bulls were categorized as high RFI (>0.5 SD above the mean, n = 8), medium RFI (±0.5 SD from the mean, n = 9), and low RFI (<0.5 SD below the mean, n = 10). At harvest, whole rumen content samples were collected from each bull to evaluate ruminal microbial community, including bacteria and protozoa. The carcass characteristics were determined by ultrasonography at the beginning and at the end of the experimental period, and behavior data were collected on d 88. As a result of ranking Nellore bulls by RFI, cattle from low-RFI group presented lesser daily dry matter intake (DMI), either in kilograms (p < 0.01) or as percentage of BW (p < 0.01) than high-RFI yearling bulls, resulting in improved gain:feed (G:F). However, variables, such as average daily gain (ADG), final BW, hot carcass weight (HCW) and other carcass characteristics did not differ (p > 0.05) across RFI groups. The eating rate of either dry matter (DM )(p = 0.04) or neutral detergent fiber (NDF) (p < 0.01) was slower in medium-RFI yearling bulls. For ruminal morphometrics an RFI effect was observed only on keratinized layer thickness, in which a thinner layer (p = 0.04) was observed in low-RFI Nellore yearling bulls. Likewise, Nellore yearling bulls classified by the RFI did not differ in terms of Shannon’s diversity (p = 0.57) and Chao richness (p = 0.98). Our results suggest that the differences in feed efficiency of Nellore bulls differing in phenotypic RFI should be attributed to metabolic variables other than ruminal microorganisms and epithelium, and deserves further investigation.
Feed additives used in finishing diets improve energy efficiency in ruminal fermentation, resulting in increased animal performance. However, there is no report evaluating the effect of BEO associated with exogenous α-amylase in response to increased starch content in feedlot diets. Our objective was to evaluate increasing levels of starch in the diet associated with a blend of essential oils plus amylase or sodium Monensin on performance, carcass characteristics, and ruminal and cecal morphometry of feedlot cattle. 210 Nellore bulls were used (initial body weight of 375 ± 13.25), where they were blocked and randomly allocated in 30 pens. The experiment was designed in completely randomized blocks in a 3 × 2 factorial arrangement: three starch levels (25, 35, and 45%), and two additives: a blend of essential oils plus α-amylase (BEO, 90 and 560 mg/kg of DM, respectively) or sodium Monensin (MON, 26 mg/kg DM). The animals were fed once a day at 08:00 ad libitum and underwent an adaptation period of 14 days. The diets consisted of sugarcane bagasse, ground corn, soybean hulls, cottonseed, soybean meal, mineral-vitamin core, and additives. The animals fed BEO35 had higher dry matter intake (P = 0.02) and daily weight gain (P = 0.02). The MON treatment improved feed efficiency (P = 0.02). The treatments BEO35 and BEO45 increased hot carcass weight (P < 0.01). Animals fed BEO presented greater carcass yield (P = 0.01), carcass gain (P < 0.01), rib eye area gain (P = 0.01), and final rib eye area (P = 0.02) when compared to MON. The MON25 treatment improved carcass gain efficiency (P = 0.01), final marbling (P = 0.04), and final subcutaneous fat thickness (P < 0.01). The use of MON reduced the fecal starch% (P < 0.01). Cattle-fed BEO increased rumen absorptive surface area (P = 0.05) and % ASA papilla area (P < 0.01). The MON treatment reduced the cecum lesions score (P = 0.02). Therefore, the use of BEO with 35 and 45% starch increases carcass production with similar biological efficiency as MON; and animals consuming MON25 improve feed efficiency and reduce lesions in the rumen and cecum.
This study, conducted at São Paulo State University feedlot, Dracena campus, Brazil, had the objective to evaluate the effect of ranking Nellore bulls according to residual feed intake (RFI) on feedlot performance and rumen morphometric variables. Twenty-seven 18-mo-old Nellore bulls (425.5 ± 20.1 kg) were randomly allocated in 27 pens (one animal per pen) and fed for 107 days. The multiple step-up diets program consisted of ad libitum feeding of diets with the concentrate level increasing from 70% to 86% concentrate. At harvest, rumen epithelium samples were collected from cranial for rumen morphometric measurements. The RFI was calculated by the difference between the predicted DMI values [DMI = (0.0544*BW0.75) + (2.9659*ADG)] and observed DMI. Then, Nellore bulls were distributed into RFI groups: High (0.5 SD above the mean; n = 8), Medium (±0.5 SD of the mean; n=9) and Low (0.5 SD below the mean; n = 10). Low-RFI Nellore bulls improved (P = 0.04) G:F when compared to High- and Medium-RFI animals (0.142 vs. 0.125 and 0.130; respectively); however, no significant RFI grouping effect was observed for ADG (P = 0.54), final BW (P = 0.54), HCW (P = 0.27), dressing percentage (P = 0.24), final LM area (P = 0.87), final 12th rib fat (P = 0.82), final P8 fat thickness (P = 0.67) and final marbling (P = 0.82). Regarding rumen morphometrics, High-RFI Nellore bulls had larger (P = 0.09) rumen absorptive surface area than Low- and Medium-RFI animals (43.31 vs. 32.95 and 31.27; respectively), which was associated to the greater (P = 0.01) DMI presented by High-RFI animals (10.2 vs. 9.1 and 9.0 for Medium- and Low-RFI Nellore bulls; respectively). Nevertheless, no significant RFI grouping effect was observed for number of papillae (P = 0.28) or mean papillae area (P = 0.61). Thus, Low-RFI Nellore bulls improved feed efficiency without promoting any positive effects on carcass traits and rumen morphometrics.
The objective of this study was to evaluate the effect of adding monensin into high-concentrate diets based on either finely-ground or high-moisture corn during the transition from adaptation to finishing diets on ruminal pH of cannulated Angus and Nellore steers. Four 30-mo-old Nellore and four 30-mo-old Angus steers were divided (± 550 kg) into two 4 x 4 Latin squares, where each square was composed by animals from same breed, and randomly submitted to a 2 x 2 factorial arrangement of treatments as follows: T1) Finely-ground corn + monensin; T2) Finely-ground corn; T3) High moisture corn + monensin; T4) High-moisture corn. Periods were divided as follows: 14 days of adaptation diets and 18 days of finishing diet (80% concentrate). The study lasted 149 days, including three 7-d washout intervals. The rumen pH was assessed continuously via data loggers on days 4, 8, 12, 16, 20, 24 and 28. Interactions between breed and days were observed for DMI (P = 0.02) and pH duration below 5.6 (P = 0.01), where Angus steers had greater DMI and spent a longer time below 5.6 than Nellore animals on days 12, 16, 20, 24 and 28. The addition of monensin decreased (P = 0.01) DMI on days 16, 20, 24 and 28. Regarding pH duration and area below 5.6, an interaction between breed and corn was observed (P = 0.001), in which Angus steers fed finely-ground corn spent a longer time (416 min/day) and had a larger area (224.6 min x pH units/day) below 5.6 than animals from other treatments. For mean pH, steers consuming high-moisture corn had higher pH (6.45 vs. 6.29); and an interaction was observed (P = 0.03) between breed and monensin, where monensin addition decreased pH for Angus (5.96 vs. 6.18), but not for Nellore steers (6.68 vs. 6.63). The feeding of monensin and finely-ground corn did not positively impact rumen pH of Angus steers.
This study, conducted at São Paulo University feedlot, Dracena, Brazil, was designed to evaluate the effect of adding either high-moisture corn, calcium salts of fatty acids (CSFA), or organic Zn+Cr on feedlot performance and carcass traits of Nellore cattle fed for 112 days. One-hundred fifty 18-mo-old Nellore bulls (404±24kg) were used and initially ranked, according to sires’ information, into groups of high and low EPD. Secondly, cattle were blocked by weight and randomly allocated to 30 pens (n = 5/pen), which were randomly assigned to the following 2x2 + 1 arrangement of treatments: Finely-ground corn, High-moisture corn, Finely-ground + CSFA, High-moisture corn + CSFA, and High-moisture corn + CSFA + Zn (90 ppm) and Cr (0.45 ppm). All diets contained 25 ppm of monensin. On day 0, one animal per pen was randomly selected to be slaughtered for baseline purposes. The replacement of finely-ground by high-moisture corn increased (P < 0.05) final BW (585 vs. 573 kg), ADG, HCW (321 kg vs. 315 kg) and decreased (P < 0.01) DMI (9.7 vs. 10.1 kg). Likewise, the addition of CSFA increased final BW, ADG (1.62 vs. 1.50 kg), and HCW (321 vs. 314 kg). The addition of Cr+Zn led to increased (P = 0.02) dressing percentage. No treatment effect was observed on final marbling (P > 0.55). It was observed interactions between treatments and EPD for G:F (P = 0.02) and final 12thrib-fat thickness (P = 0.03), where cattle from low-EPD groups needed high-moisture corn, CSFA and organic Zn+Cr to improve G:F and increase fat deposition; however, animals from high-EPD groups required only high-moisture corn. The adding of either high-moisture corn, CSFA, or organic Zn+Cr improved feedlot performance of Nellore cattle, and its effects seemed to be more effective in animals from low-EPD groups.
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