No abstract

We evaluate the effect of the weaning strategy (WS; early, 130 ± 21 d vs normal, 187 ± 20 d) and backgrounding management (BGM) on growth, carcass characteristics, and relative mRNA expression in the longissimus muscle (LM) of beef steers. One hundred and twenty Angus × SimAngus-crossbred steers (body weight (BW) = 130 ± 11.2 kg) were used in a randomized complete block design. Steers, blocked by age and BW, were randomly assigned to 1 treatment (2×2 factorial). Treatments consisted of early weaned (EW) or normal weaned (NW) steers subsequently backgrounded (BG) on either a forage-based (FB) or concentrates-based (CB) diet. The EW steers (d 0) were ad libitum-fed a grain-based diet for 49 d until nursing calves were NW. Steers were ad libitum-fed either a FB diet for 214 d or a CB diet for 95 d afterward. Steers were finished on a high grain diet until harvested at an estimated constant 12 th rib fat thickness (1.5 cm). Expression of mRNA in the LM was measured over time. Data were analyzed using PROC MIXED in SAS. The EW steers were heavier (P ˂ 0.01) at the beginning of the backgrounding and finishing period. When the finishing phase began, steers FB were heavier (P ˂ 0.01) than CB steers. There was a tendency for a WS × BGM interaction (P = 0.08) for final BW, where NW-FB steers were heavier than the steers on the other 3 treatments, which do not differ between them. In the finishing phase, steers BG on a FB diet had greater dry matter intake and ADG, but lower gain to feed ratio (P ˂ 0.01). There was a WS × BGM interaction (P = 0.03) for days on feed (DOF) in the finishing diet, where backgrounding steers in a FB diet decreased DOF required to reach the harvesting target among EW steers, but not within NW steers. No interactions or treatment effects (P ≥ 0.17) were detected for marbling score (MS). For ZFP423, EW steers showed a greater mRNA expression on d 112 and a lower expression on d 255 than NW steers (P ˂ 0.01). In d 57, steers BG on a CB diet presented a greater DLK1 mRNA expression than steers BG on a FB diet, whereas in d 255, this was inverted (P ˂ 0.01). For C/EBPD mRNA expression, a tendency for a WS × BGM interaction was observed (P = 0.06), where a greater expression of C/EBPD was observed in steers BG on a FB diet among EW steers, but not within NW steers. In this study, early grain feeding followed by different backgrounding management does not support MS improvements of beef carcasses.

To evaluate the effect of supplementing beef cattle with a ruminal probiotic consisting of native rumen microbes (NRM; Chordicoccus furentiruminis, Prevotella albensis, and Succinivibrio dextrinosolvens) on methane (CH4) emissions, growth performance, carcass characteristics, and plasma metabolites, Angus × SimAngus-crossbred steers (n = 32; 8 per pen) and heifers (n = 48; 12 per pen) with an initial body weight (BW) of 353 ± 64 kg were used in randomized complete block design. Cattle were blocked by sex and BW and randomly assigned to 1 of 2 treatments (2 pens per treatment). Treatments consisted of diets offered for ad libitum intake with (NRM) or without (CON) the inclusion of the ruminal probiotic. Cattle were fed a growing diet for 49 d followed by a ground corn-based diet for 124 ± 27 d until reaching the targeted final BW (635 kg for steers and 590 kg for heifers). Methane emissions were estimated using the GreenFeed system (n = 12 per treatment) prior to trial commencement (baseline; period 1), and on three (2, 3, and 4), and two (5 and 6) different sampling periods throughout the growing and finishing stage, respectively. All data were analyzed using the PROC MIXED procedure of SAS. For CH4 production (g/d), there was a tendency for an NRM supplementation × period interaction (P = 0.07) where cattle-fed diets with NRM had lower production of methane in periods 3 and 4. Including NRM in the diet decreased CH4 yield (g/kg of dry matter intake (DMI)) by 20%. For CH4 emission intensity (g/kg of average daily gain (ADG)), an interaction (P < 0.01) of NRM supplementation × period occurred. In periods 2 and 3, cattle-fed diets with NRM inclusion had lower CH4 emission intensity than CON cattle. During the 84-d period when all cattle were still on the finishing diet, feeding NRM increased (P = 0.02) ADG and tended to increase (P = 0.10) DMI. At the end of the 84-d period, cattle-fed NRM tended to be heavier (P = 0.06) than CON cattle. Cattle supplemented with NRM required less (P = 0.04) days on feed to reach the targeted final BW. No differences (P ≤ 0.11) were detected for gain-to-feed ratio and carcass characteristics. Cattle-fed NRM had greater abundance of uncultured rumen bacteria that may improve rumen digestion when fed a high grain diet and potentially promote the reduction of enteric CH4 production. Results from this study suggest that daily administration of NRM may be a strategy to mitigate methanogenesis and improve the growth performance of beef cattle.

One-hundred twenty crossbreed steers (initial body weight (BW) 566 ± 42 kg) were used to evaluate the interaction of protein source (PS) and non-roughage NDF content (NRFC) in finishing diets of feedlot cattle fed free-choice hay on performance and carcass characteristics. Steers were stratified by BW and randomly assigned to 8 pens (2×2 factorial) and fed for 104 ± 10 d. Four dietary treatments were investigated: 1) distillers’ dry grains with solubles (DDGS) and a low NRFC (DLF), 2) DDGS and a high NRFC (DHF), 3) soybean meal (SBM) and a low NRFC (SLF), 4) SBM and a high NRFC (SHF). Free-choice grass hay and concentrates were offered in a different bunk. Data were analyzed as a randomized complete block design. Do to the confounded effect of PS and protein intake, a linear regression was used to evaluate the effect of protein intake in growth performance. For gain to feed ratio (G:F) an interaction tended to occur (P = 0.10) between PS and NRFC. Steers on the DHF treatment had a lower G:F compared with SLF and SHF. Feeding SBM increased (P = 0.05) final BW, tended to increase (P = 0.06) average daily gain (ADG), and decreased (P = 0.05) hay intake (HI) compared with steers fed DDGS. There was a positive association (P ˂ 0.01) of crude protein intake with ADG and FBW. Dietary NRFC did not change (P ≥ 0.3) final BW, ADG, DMI, and HI. Protein source did not affect (P ≥ 0.16) hot carcass weight (HCW), longissimus muscle (LM) area, dressing, 12th rib fat thickness, or marbling score (MS). No differences were detected between NRFC for dressing, HCW, LM area, or MS (P ≥ 0.18); but diets with greater NRFC decreased (P = 0.03) the 12th rib fat thickness. Steers in the SHF treatment presented the lesser kidney-pelvic-heart fat compared with the remaining treatments (PS×NRFC interaction, P = 0.04). Soybean meal inclusion/increase in protein intake improved growth performance of feedlot steers compared with DDGS, despite protein intake meet the protein requirement. Increasing the NRFC did not affect growth or HI but decreased feed efficiency of steers fed DDGS.

The objective was to evaluate the effect of adding an exogenous glucoamylase (GA) enzyme to a finishing diet on in vitro digestion and performance of feedlot cattle. Experiment 1 evaluated 3 levels of added enzyme (0, 0.24, and 0.72 GA enzyme units) and 2 corn particle sizes (2 and 4 mm) in a 7 h in vitro batch culture fermentation. No interactions were observed (P > 0.10). Addition of GA increased (P < 0.01) in vitro dry matter disappearance by 9%. A smaller corn particle increased (P < 0.01) in vitro dry matter disappearance by 11%. In Experiment 2, Angus × Simmental steers (N = 105; BW = 340 ± 39 kg) were blocked by weight and assigned to 15 pens. Pens were randomly assigned to one of 3 treatments: control (CON) diet with no added enzymes, low inclusion of GA (122 enzyme units/kg DM; LGA), or high inclusion of GA (183 enzyme units/kg DM; HGA). Steers were fed a basal diet consisting of 60% dry rolled corn, 17.5% modified distillers grains with solubles, 12.5% corn silage, and 10% of a corn-based supplement on a DM basis for 139 d. Inclusion of GA did not affect (P ≥ 0.24) final BW, DMI, or ADG overall for the 136 d feeding period. Steers fed HGA had increased (P = 0.02) G:F compared with LGA and CON with least square means of 0.213, 0.194, and 0.197, respectively. Inclusion of GA did not affect (P ≥ 0.19) carcass traits including HCW, 12th rib fat thickness, yield grade, longissimus muscle area, or marbling score. Overall, results suggest inclusion of exogenous glucoamylase enzyme increased in vitro dry matter disappearance in batch culture and improved feed conversion of the finishing diet fed to feedlot steers at 0.381 g enzyme protein/kg DM.

The objective of this study was to evaluate the effect of increasing quantity of soy-hulls in diets of feedlot cattle offered free-choice hay on finishing performance, roughage intake, and carcass characteristics. Sixty heifers and 54 steers, Angus*Simangus-crossbreds, were used in a randomized complete block design. Cattle were stratified by sex and weight and randomly assigned to 1 of 12 pens. Treatment 1 consisted of 5% soy hulls (SH; 5%SH), 70% cracked corn (CC), 15% dry distiller grains with soluble (DDGS), 10% mineral supplement (SUP). Treatments 2 (10%SH) and 3 (15%SH) included an additional 5% and 10% SH in place of CC, respectively. Hay was offered ad libitum and separate from the concentrates in different bunks, both concentrate and forage were fed in GrowSafe units. Data were analyzed as a complete block design and mean differences in group means were determined using polynomial contrast [lineal (L) and quadratic (Q)]. There was a quadratic effect of soy hull inclusion on final body weight (fBW) and concentrate intake (Q-P ˂ 0.05); 5%SH and 15%SH had a greater fBW and concentrate intake compared to those fed 10%SH. Gain to feed ratio was not affected by treatments (L-P ≥ 0.33). There was a linear effect of SH on hay intake (L-P ˂ 0.05) with cattle fed 5%SH consuming less hay than those fed 15%SH. There was no effect on ribeye area, yield grade, or backfat (L-P ≥ 0.35; Q-P ≥ 0.14). Hot carcass weight tended to quadratically respond to dietary treatments (Q-P < 0.10), while marbling score tended to be linearly decreased by increased SH inclusion (L-P = 0.09). Kidney-pelvic-heart fat was linearly decreased by increased SH inclusion (L-P ˂ 0.05). Results indicate that non-roughage NDF from by-products can effectively contribute to a reduction of roughage utilization in feedlot diets without compromising growth performance or carcass characteristics.

Sixty Angus × SimAngus-crossbred steers (body weight (BW) 279 ± 16 kg) were used to evaluate the effect of calcium salts of palm oil inclusion (CPO) and amount of feed offered (AFO) on plasma glucose-dependent insulinotropic polypeptide (GIP) concentration and its association with energy metabolism and marbling score (MS) in feedlot steers. Steers were blocked by BW and gain to feed (G:F) and randomly assigned to individual feedlot pens. Treatments (2×2 factorial) consisted of ad libitum-fed steers without (ANF) or with (AWF) the inclusion of CPO or restricted-fed steers (85% of the ad libitum intake of ANF) without (RNF) or with the inclusion of CPO (RWF). After weaning, steers were adapted to individual pens and fed a corn silage-based diet for 30-d and subsequently placed in a ground corn- (GC) based diet. Diets were given ad libitum or at 85% of the ANF intake and with or without CPO. After 59 d on the finishing diet, all steers had ad libitum access to the finishing diet until harvest. Measurements of CO2 emission and O2 consumption to estimate respiratory quotient (RQ) were taken (n = 9/ treatment). Correlations between plasma GIP and insulin concentrations and RQ were analyzed. A linear regression was performed to evaluate the association of plasma GIP and MS. All data were analyzed using the PROC MIXED procedure of SAS. During the first 103 d of the trial, there were AFO × CPO interactions (P ≤ 0.01) for BW, dry matter intake (DMI), average daily gain (ADG), and net energy for maintenance (NEm) intake. Ad libitum-fed steers without CPO presented the greatest DMI among dietary treatments and had greater BW and ADG compared with steers in the RWF and RNF treatments. After all steers had ad libitum access to dietary treatments, steers that were previously restricted showed a 30% and 19% increase (P ≤ 0.01) in ADG and G:F, respectively. There was a 3-way interaction time × CPO × AFO (P = 0.04) for plasma GIP concentration. There was no correlation (P = 0.96) of GIP with RQ, while insulin demonstrated marginal significance for a positive (P = 0.07) and negative (P = 0.08) correlation with plasma GIP and RQ, respectively. There was no association (P = 0.30) between GIP and MS. These data indicate that GIP secretion results from an interaction between CPO and energy intake depending on the time relative to feed intake, that GIP might indirectly regulate energy metabolism through insulin secretion, and that GIP does not appear to be associated with MS.

To evaluate the effect of supplementing feedlot cattle with native rumen bacteria (NRB; Prevotella albensis, Succinivibrio dextrinosolvens, and Chordicoccus furentiruminis) in growth performance, carcass characteristics and gas emissions, Angus × SimAngus-crossbred (body weight (BW) 353 ± 64 kg) steers (n = 32) and heifers (n = 48) were used in randomized complete block design. Cattle stratified by BW were randomly assigned to 4 pens (2/treatment) and fed a corn silage-based diet for 49 d (backgrounding) followed by a ground corn-based diet for 84 d (finishing). When reaching desired finished BW, cattle were harvested. Diets were offered ad libitum and with (WNB) or without (CON) the inclusion of NRB feed supplement. Measurements of CH4 emissions were taken using the GreenFeed system (n = 12/ treatment). All data were analyzed as a mixed procedure (Table 1). There was a treatment (P ≤ 0.05) effect for CH4 emissions yield [g/kg dry matter intake (DMI)] and intensity [g/kg average daily gain (ADG)] during the growing period. Including NRB in the diet during growing, decreased CH4 emissions yield and intensity by 13.5% and 29%, respectively. During the first 84-d period on the finishing diet (d133), feeding NRB increased (P = 0.02) the ADG and tended to increase (P = 0.10) DMI. At d133, cattle fed NRB tended (P = 0.06) to be heavier than cattle in the CON treatment. Days on feed (DOF) was 9 days longer for CON animals than those of WNB animals (P = 0.04). No other differences (P ≥ 0.25) were detected throughout the experimental period and no differences (P ≥ 0.11) were observed in carcass characteristics. Results from this study indicate that feeding NRB decreased methane yield and intensity in the backgrounding period, improved finishing performance of beef cattle, and decreased DOF