No abstract

A large pen feedlot study was conducted to evaluate response of yearling steers fed novel sources of rumen-protected folate (RPFA) and cobalt (cobalt pectinate; Co-PECT) on plasma levels of vitamin B12 and folate, growth performance and carcass characteristics. A total of 2,100 steers (initial BW = 381 ± 45.2 kg.) were enrolled in the study at the time of randomization with 2,091 steers started on treatment diets following transition to the finishing diet. A generalized randomized block design with sampling error (GRBD) with two treatments and 15 pen replications per treatment (5 blocks x 6 pens/block; 30 pens total with 70 steers/pen) were evaluated with pen serving as the experimental unit. A control (CON) treatment consisted of the standard finishing diet while the test diet consisted of the standard finishing diet providing 3.0 mg∙kg -1 DM of RPFA and 1.0 mg∙kg -1 DM total supplemental cobalt with approximately half coming from Co-PECT (TEST). Blood samples were collected from 60 randomly selected steers at study initiation and prior to shipping for plasma B12 and folate measurement. Data were analyzed with the model including fixed effects of treatment, block, and treatment within block interaction. Live growth performance was not affected by treatment; however, carcass-adjusted performance and hot carcass weight were numerically improved by TEST in 3 of the 5 blocks (treatment x within block interaction, P ≤ 0.03) of cattle. Plasma levels for both folic acid and vitamin B12 were extremely low at study initiation and increased over the course of the feeding period. Feeding TEST increased (P < 0.01) plasma B12 levels compared to CON by the completion of the trial; however, mean levels would still be considered marginal. Plasma folate was lower (P < 0.05) in TEST steers at the beginning of the study, with no difference between treatments by the time cattle were shipped. Results suggested that cattle coming into the feedlot may be of low or marginal status in both plasma folate and vitamin B12. While status of folate and B12 improved in both CON and TEST with days on feed, providing RPFA and Co-PECT further helped improve vitamin B12 status; although, overall levels remained low, which may have affected the overall response to RPFA. Additional research is required to better understand the role of B vitamin supplementation for growing-finishing feedlot and develop methods for assessing status and improving potential responses.

Feedlot efficiency increases as technologies are adopted and new feed ingredients, especially byproducts, become available and incorporated into diets. Byproduct availability increased in response to the renewable fuels standard of 2005, creating substantial amounts of feedstuffs best used by ruminants. Cereal grains have been partially replaced with human-inedible byproducts, as they provide comparable levels of energy in cattle diets. To evaluate the effects of changes in diet and feedlot production practices on net protein contribution (NPC) and human-edible protein conversion efficiency (HePCE) across time, a deterministic NPC model was used. NPC was assessed for the feedlot industry using lot level production data from 2006 to 2017 for eight commercial feedlots. Ingredient and nutrient composition was collected for a representative starter and finisher diet fed for each year from each feedlot. NPC was calculated by multiplying human-edible protein (HeP) in beef produced per unit of HeP in feed by the protein quality ratio (PQR). Systems with NPC >1 positively contribute to meeting human protein requirements; NPC < 1 indicates competition with humans for HeP. NPC was regressed on year to evaluate temporal change in NPC. Feedlots were categorized as increasing NPC (INC; slope > 0) or constant NPC (CON; slope = 0) according to regression parameter estimates. Four feedlots were categorized as INC and four were CON. The rate of change in PQR was similar for CON and INC (P ≥ 0.79), although rates of change among INC and CON differed for byproduct and cereal grain inclusion (P ≤ 0.01) across years evaluated. Feedlots categorized as INC reduced HeP consumed by 2.39% per year, but CON feedlots did not reduce HeP consumed each year (0.28%). Cattle received and shipped by INC were lighter than those in CON feedlots (P < 0.01). Across years, INC produced more HeP (20.9 vs. 19.2 kg/hd) than CON (P < 0.01), and both feedlot types tended to improve HeP gained over time (0.1 kg per year; P = 0.10). Differences in slope over time for INC and CON were observed for conversion efficiency of HeP (P < 0.01). NPC increased 0.027 units per year for INC (P < 0.01) and was 0.94 in 2017. NPC by the feedlot sector improved from 2006 to 2017, decreasing the amount of human-edible feeds required to produce more high-quality protein from beef.

Net protein contribution (NPC) of the beef value chain has been evaluated and it has been demonstrated that the beef value chain positively contributes to NPC; however, the specific role of growth-enhancing technologies has not be evaluated. To compare effects of technology on NPC baseline, performance data from 8 commercial feedlots located in the Texas panhandle (n = 6) and Kansas (n = 2) were used to create 8 scenarios: 1) no technology (NT), 2) ionophore (ION), 3) implant (IMP), 4) beta-agonist (B), 5) ionophore and implant (ION+IMP), 6) ionophore and beta-agonist (ION+B), 7) implant and beta-agonist (IMP+B), and 8) ionophore, implant and beta-agonist (I+I+B). An IMP×B interaction was observed for human-edible protein conversion efficiency (HePCE) and NPC (P ≤ 0.03). Implants and beta-agonists increased HePCE and NPC compared to NT (P < 0.01), and IMP+B was greater than combined effects of IMP and B. Ionophore scenarios had greater HePCE and NPC compared to NT (P < 0.01). Interactions for ION×IMP and IMP×B were observed for NPC of beef value chain (P < 0.03), but an ION×B interaction was not observed (P = 0.07). All technology scenarios were lower than NT for NPC (3.21 vs 3.74, respectively; P < 0.01) because HePCE for the beef value chain was reduced when cattle were fed longer in the technology scenarios. Interactions for ION×IMP, IMP×B, and ION×B were observed for enteric CH4 production feedlot cattle (P ≤ 0.03), and a three-way interaction was observed for enteric CH4 production of the beef value chain (P < 0.01). All technologies reduced enteric CH4 produced per kg of HePg compared to NT (P < 0.01). Net protein contribution should be balanced with other indicators of sustainability for a representative understanding of technology impacts on sustainable beef production.

Crossbred beef steers (n = 2,420; 357 ± 16 kg BW) were used to evaluate the effects of supplemental trace mineral sources on the performance and carcass characteristics on feedlot cattle. Steers were housed in 20 pens (120–125 steers per pen) with 10 pens per treatment. Supplemental trace mineral treatments (100% DM) consisted of: control: 8.3 mg/kg of Cu (100% CuSO4), 83.4 mg/kg of Zn (64.1% ZnSO4/35.9% Zn amino acid complex), and 28.7 mg/kg of Mn (100% MnSO4); hydroxy: 8.3 mg/kg of Cu (100% basic Cu chloride), 82.9 mg/kg of Zn (100% Zn hydroxychloride), and 19.3 mg/kg of Mn (100% Mn hydroxychloride). Steers were fed trace mineral treatments for 158 d and harvested at a commercial abattoir. Data were analyzed as a randomized complete block design with pen as the experimental unit. There were no differences between treatments in DMI, ADG, feed:gain, final BW, or mortality (P ≥ 0.38); however, morbidity tended (P = 0.06) to be greater for hydroxy than control (3.44 or 2.20%, respectively). Hot carcass weight, dressing percentage, marbling score, and longissimus muscle area were unaffected (P ≥ 0.28) by treatment, though backfat tended (P = 0.07) to be greater for hydroxy compared to control (1.55 or 1.51 cm, respectively). Distributions of quality grades were not different (P ≥ 0.14) with the exception of increased (P = 0.01) Prime carcasses in control compared to hydroxy (2.57 or 1.18%, respectively). Distributions of yield grades 2, 3, and 4 were not different (P ≥ 0.17) between treatments, though percentage of carcasses assigned 1 was reduced (P = 0.01) and 5 was increased (P = 0.05) in hydroxy compared to control. These data indicate steers fed 100% hydroxychloride trace minerals perform similiarly to steers fed CuSO4, MnSO4, and a ZnSO4/Zn amino acid complex combination.