Applied Animal Science最新文献

Objective

The objective of Exp. 1 was to evaluate the effects of adding urea to modified distillers grains with solubles (MDGS) when supplemented to growing steers and in Exp. 2 to evaluate whole corn as an alternative to dried distillers grains with solubles (DDGS) for growing steers grazing cornstalk residue.

Methods and Materials

In Exp. 1, 120 crossbred beef steers (initial BW = 244 kg, SD = 19 kg) grazed corn residue for 72 d. Treatments were a 2 × 2 factorial arrangement of MDGS inclusion (1.4 or 2.3 kg/d) and urea inclusion (0 or 0.05 kg/d). Residue diet samples were collected to determine CP, in vitro organic matter disap- pearance (IVOMD) and digestible organic matter (DOM). Steers were individually supplemented daily. Data were analyzed using the MIXED procedures of SAS. In Exp. 2, 75 crossbred steer calves (235 kg, SD = 3.5) grazed corn residue for 86 d. Treatments were arranged in a ran- domized complete block design, which included (1) a non- supplemented control, (2) whole corn, (3) whole corn with urea in a molasses carrier (corn/mol/urea), (4) DDGS, and (5) 60% SoyPass + 40% soybean meal (SoyPass/ SBM). Supplements were designed to be isocaloric. Data were analyzed using the GLIMMIX procedures of SAS. Results were considered significant at P ≤ 0.05.

Results and Discussion

No MDGS × urea inter- actions were observed for growth performance (Exp. 1). Steers supplemented with 2.3 kg MDGS had greater ADG than those supplemented with 1.4 kg MDGS (1.05 kg/d vs. 0.83 respectively). Urea level did not affect ending BW or ADG. The IVOMD and DOM of the grazed residue decreased linearly and quadratically, respectively, as the grazing progressed as expected, but CP was not different. In Exp. 2, nonsupplemented calves lost weight (0.08 kg/d) Calves receiving whole corn had greater gains (0.14 kg/d) than the nonsupplemented calves but less than corn/ mol/urea (0.24 kg/d). The DDGS and SoyPass/SBM had greater gains than the other treatments, but were not dif- ferent from each other (0.60 and 0.67 kg/d, respectively).

Implications and Applications

These data suggest adding RDP when supplementing MDGS is unnecessary and that feeding whole corn, even with a source of NPN to supply RDP does not result in similar performance as feeding DDGS or SoyPass/SBM.

Objective

The objective was to evaluate the effect of days on feed (DOF) on performance and carcass characteristics of crossbred beef × dairy heifers.

Materials and Methods

Beef × dairy heifers (n = 3,765; initial BW = 508 ± 8.55 kg) were blocked by arrival date and lot (n = 6 blocks at feedyard 1 and n = 7 blocks at feedyard 2) and randomly assigned to 1 of 4 DOF treatments of 323, 344, 362, or 385 when administered a Revalor-200 (200 mg of trenbolone acetate [TBA] and 20 mg of estradiol [E₂]) on d 265.

Results and Discussion

Dry matter intake was not affected by DOF, whereas final BW increased linearly from 593 to 655 kg. As DOF increased, ADG and gain: feed decreased quadratically. Hot carcass weight, LM area, calculated YG, and marbling score increased linearly as DOF increased. Across the 63-d serial slaughter period, hot carcass weight increased 0.67 kg/d. Dressing percentage and backfat thickness increased in a quadratic manner across DOF. Further, QG and YG distribution increased linearly as DOF increased. Liver abscess prevalence or severity did not increase with DOF.

Implications and Applications

Results of this study indicate that extending DOF by 63 d led to increased BW, hot carcass weight, LM area, marbling, YG, and QG but poorer ADG and feed conversion efficiency for beef × dairy crossbred heifers.

Objective

Our objective was to evaluate how a particular zeolite-based flow agent affected ergot alkaloid digestion and physiological markers associated with fescue toxicosis.

Materials and Methods

Twenty-four steers (226 ± 27.6 kg) were used to test effects of enhanced zeolite-based flow agent (KALLSIL, Kemin Industries, Des Moines, IA) on ergot-like alkaloid digestion. Treatments were control (E+) or enhanced zeolite inclusion (E+Z; 2 g/kg, DM basis). Steers were limit-fed diets (1.8% of BW, DM basis) containing 465 μg of ergovaline/kg of DM. Rectal temperature and respiration rate were recorded daily at 0700 and 1200 h from steers in a room kept at 18.5°C ± 0.33°C, 32.6% ± 2.19% relative humidity. Blood was collected on d 1, 7, 14, and 21 to measure prolactin. On d 21 prolactin stores were measured following infusion of thyrotropin- releasing hormone (TRH; 1 μg/kg BW). Feces and urine were collected every 8 h from d 17 to 20, with 2-h advancement daily for digestibility, N balance, and recovery of ergot-like alkaloids.

Results and Discussion

Digestion and N balance were not affected by treatment. Zeolite did not affect fecal recovery of ergovaline. Serum prolactin declined over time. Serum prolactin was greater in steers fed E+Z. Following TRH infusion, prolactin was numerically greater for E+Z. Rectal temperatures and respiration rates were not affected by E+Z.

Implications and Applications

Under the conditions of this experiment, addition of this particular zeolite-based feed additive had minimal impact on ergot alkaloid recovery and physiological markers associated with fescue toxicosis.

Purpose

This literature review explains current understanding of the mechanisms by which branched-chain volatile fatty acids (BCVFA), historically termed isoacids, can improve fiber digestibility, microbial protein production, and either milk production or production efficiency.

Sources

Peer-reviewed literature and ADSA abstracts were the primary course of information reviewed.

Synthesis

Although traditionally included in isoacid supplements with the 3 BCVFA, the straight-chain valerate does not warrant being included. Because of the high concentration of its precursor leucine in corn protein, isovalerate is less likely to be needed than 2-methylbutyrate and isobutyrate. If conditions are not amenable for BCVFA assimilation into microbes, particularly if ruminal ammonia is deficient, more supplemental BCVFA are available for postruminal metabolism. Isovalerate is likely metabolized primarily in the rumen epithelium, whereas isobutyrate and 2-methylbutyrate are likely metabolized in the liver or peripheral tissues. If BCVFA improve fiber degradability, typically by 3 to 5 percentage units, a more balanced consortium of ruminal microbes should improve efficiency of microbial protein production so long as ruminal nitrogenous precursors are adequate.

Conclusions and Applications

Increased acetate production from improved fiber digestibility is thought to increase milk fat production, particularly in multiparous cows. In primiparous cows, the acetate from improved fiber degradability might be diverted to body weight gain. Milk production efficiency responses of 5% to 10% have been recorded with optimum doses of BCVFA and adequate rumen-degraded protein supply.

Objective

This study evaluated the effects of feeding lubabegron fumarate compared with ractopamine hydrochloride in beef × dairy crossbred steers fed a corn-based diet in western Canada.

Materials and Methods

Beef × dairy (Limousin × Jersey) crossbred steers (n = 760, initial BW = 530.0 ± 34.7 kg) were randomly allocated 80 d before slaughter to 1 of 2 experimental groups. A total of 20 replicates were allocated to the study, with each replicate comprising 1 pen from each experimental group (for a total of 40 pens) and 19 steers per pen. Pen was the experimental unit. Experimental groups consisted of either lubabegron fumarate (Experior 10, Elanco Canada Limited, Mississauga, Canada) fed at a target level of 3.5 mg/kg diet DM for 56 d before slaughter (EXP) or ractopamine hydrochloride (Optaflexx 100, Elanco Canada Limited) fed at a target level of 250 mg/steer daily the last 28 d before slaughter (RAC).

Results and Discussion

Steers in the EXP group had lower DMI, greater carcass weight, and greater DP compared with steers in the RAC group. Steers in the EXP group had greater ADG and G:F on both a carcass weight and live weight basis compared with steers in the RAC group. Steers in the EXP group also had a greater proportion of YG Canada 1 carcasses, a lower proportion of QG Canada Prime carcasses, increased LM area, and a lower overall marbling score compared with steers in the RAC group.

Implications and Applications

Feeding lubabegron fumarate increased feedlot performance, the proportion of YG Canada 1 carcasses, and LM area, but decreased the proportion of QG Canada Prime carcasses and overall marbling score compared with feeding ractopamine hydrochloride. Magnitude of improvement in G:F was greater on a carcass weight basis than on a live weight basis.

Objective

This study compared weight gain and fecal egg count of heifers grazing native or introduced warm- season mixed-grass pasture.

Materials and Methods

Sixty fall-born, spring- weaned Angus crossbred heifers (8.5 mo old; 242 ± 26.9 kg) in each of 2 yr (2022 and 2023) were randomized to one of six 2.02-ha pastures (5 heifers/ha and 3 replicates per pasture type) of either native grass (NAT; predominately big bluestem [Andropogon gerardi Vitman]) or introduced mixed grass (WSMG; bermudagrass [Cynodon dactylon (L.) Pers.], crabgrass [Digitaria spp.], and foxtail [Setaria spp.]). Heifers grazed 84 d beginning the last week of May and were weighed every 28 d. Fecal samples were collected from each heifer toward the beginning and end of grazing for strongyle egg enumeration. Forage mass and nutritive value were assessed each time the cattle were weighed.

Results and Discussion

Forage mass and nutritive values differed for each year and pasture type. The NAT pastures had greater forage mass, lesser CP, and greater detergent fiber levels than WSMG. Season-long ADG differed by pasture type and year, with ADG being 0.22 kg/d greater in 2022 and 0.11 kg/d greater in 2023 for NAT. A forage system by sample day interaction in 2023 but not 2022 occurred with fecal egg counts.

Implications and Applications

At a fixed stocking rate, heifers continuously grazing native grasses dominated by big bluestem out gained heifers grazing mixed introduced warm-season grasses heavily infested with foxtails.

Objective

Our objective was to determine the inter- relationship between rumen health dynamics and animal growth and development characteristics of growing and finishing steers receiving virginiamycin (VM). A companion article was published previously (Rivera et al., 2024).

Materials and Methods

A total of 120 Angus-crossbred steers (304 ± 27 kg) were assigned randomly to 1 of 20 pens equipped with a Calan gate feed system from which animals within a pen received VM (240 mg/d) or not as follows: no VM (T₀₀₀); VM in the last 50 d (T₀₀₁); VM for the last 100 d (T₀₁₁); VM in the first 50 d (T₁₀₀); VM in the first 100 d (T₁₁₀); and VM for 150 d (T₁₁₁). At slaughter, the 9th to 11th rib section was collected from the right side of each animal’s carcass to estimate carcass and empty body composition. Data were analyzed using a random coefficients model with the pen as a random effect and animals within treatment as the subject.

Results and Discussion

Dry matter intake was less for T₁₁₁ compared with T₀₀₀; however, ADG was not different. Thus, VM improved G:F. The T₀₁₁ had greater DMI compared with T₁₁₀, which resulted in greater ADG with no difference in G:F. Apparent total-tract NDF digestibility was greater for T₁₁₁ than T₀₀₀, which was confirmed by an improved diet growth-adjusted ME for T₁₁₁ than T₀₀₀. The T₀₁₁ tended to have a greater carcass and final shrunk BW than T₁₁₀. Ether extract content of the 9th to 11th rib section tended to be decreased for animals that consumed VM regardless of the period or length of feeding, resulting in a tendency to have less empty body fat content.

Implications and Applications

In this experiment daily inclusion of VM during the overall feeding phase increased feed energy utilization, and its withdrawal during the end of the finishing phase (T₁₁₀) decreased DMI and ADG. Continuous VM feeding enhanced fiber digestion and energy utilization, likely due to it promoting ruminal health.

Objective

One objective of this study was to determine the nitrogen-corrected apparent metabolizable energy (AME_n) content of tannin-free red/bronze, white/tan, and US No. 2 varieties of grain sorghum fed to Northern Bobwhite quail; the determinations were done when the quail were 6 and 11 wk of age. Our other objective was to evaluate the effects of AME_n on growth performance.

Materials and Methods

The AME_n content of red/ bronze, white/tan, and US No. 2 grain sorghum varieties was determined using a dextrose control diet as the standard, fed to 200 mixed-sex Northern Bobwhite quail. Weekly measures of mean BW and feed consumption were used to calculate BW gain, feed intake (FI), and feed conversion ratio (FCR). Analyses were based on a 2 × 4 factorial treatment design with age (grower and finisher phases) and grain types (corn-dextrose, red/bronze, white/tan, and US No. 2) defining the treatments. Cage was the experimental unit, with data analyzed using JMP Pro version 16 (SAS Institute Inc., Cary, NC).

Results and Discussion

The interaction between the diet and age effect was not significant for any of the variables assessed. Mean AME_n values of modern grain sorghum varieties for Northern Bobwhite quail at 6 wk of age were determined as 3,683 (red/bronze), 3,604 (white/ tan), and 3,625 (US No. 2) kcal/kg. At 11 wk of age, the determined AME_n values were 3,502 (red/bronze), 3,486 (white/tan), and 3,522 (US No. 2) kcal/kg. Age had a significant effect across AME_n, BW gain, FI, and FCR. Surprisingly, AME_n decreased with age, and sorghum varieties showed a greater FI versus the control diet. White/tan and US No. 2 sorghum reported a greater FCR than the control. The reduction in AME_n with age might reflect a complex interplay of physiological, dietary, and environmental factors in Northern Bobwhite quail, where further research for optimizing nutrition and management practices is warranted.

Implications and Applications

The findings revealed a comparable AME_n level among sorghum types and corn. This study aligns with the shared goals of wildlife conservation and agricultural sustainability, confirming tannin-free sorghum as a potential energy source to enhance the Northern Bobwhite quail habitat and breeding.

Purpose

Alfalfa inclusion rates in dairy cow diets are decreasing, often with a concomitant increase in corn silage. This article discusses how soy-based ingredients fit into diets containing lower levels of alfalfa and higher levels of corn silage.

Sources

The data and conclusions in this review are derived from peer-reviewed journal articles.

Synthesis

In many areas, corn silage is becoming the primary forage in dairy diets by replacing alfalfa. Replacing alfalfa with corn silage increases the need for supplemental protein. Soy ingredients are efficient sources of MP. The RDP fraction in soy is almost exclusively amino nitrogen, which is efficiently used by microbes, and the RUP is highly digestible. As the concentration of alfalfa decreases and the concentration of soy protein increases, less CP should be needed to meet the MP requirements. As corn silage replaces alfalfa, negative responses to greater starch concentrations increase. Soyhulls are highly digestible and contain little starch, which makes them a good replacement for starch in diets high in corn silage and low in alfalfa. Diets with little or no alfalfa that include soy products can produce similar amounts of milk and milk components using less starch and CP than diets with greater amounts of alfalfa.

Conclusions and Applications

As corn silage replaces alfalfa in diets, more supplemental protein will be needed, but often diet CP concentrations can be reduced when much of the supplemental protein derives from soy. Dietary starch concentrations should be reduced with low- alfalfa diets because of increased risk of acidosis. Replacing some of the starch with soyhulls reduces acidosis risk.

Objective

Our goal was to determine whether admin- istration of Fusobacterium necrophorum ssp. necrophorum into the jugular or portal vein will induce liver abscesses in preruminant calves.

Materials and Methods

The study was performed as 2 experiments according to the inoculation site: jugu- lar vein or hepatic portal circulation. Experiment 1 was performed in 18 calves randomly assigned to receive intra- jugular infusion of saline (CONIV), or 10⁷ (FUSOIV7), 10⁹ (FUSOIV9), and 10¹¹ (FUSOIV11) of F. necrophorum. In experiment 2, 20 calves were assigned to receive intrapor- tal infusion of saline or 10⁶ (FUSOPV6), 10⁸ (FUSOPV8), and 10¹⁰ (FUSOPV10) of F. necrophorum. Blood samples were collected on d 0, 1, 3, 5, 7, and 14 for hematology. Calves were slaughtered 14 d after inoculation and exam- ined for liver gross pathology.

Results and Discussion

Neither model produced liver abscesses. However, in experiment 1, inoculation increased monocyte counts in FUSOIV11 calves versus CONIV, FUSOIV7, and FUSOIV9 on d 3 and 5 postchal- lenge. The neutrophil-to-lymphocyte ratio was greater for FUSOIV11 than CONIV and FUSOIV9 on d 7 postchallenge. In experiment 2, inoculation increased monocyte and neutrophils counts in the FUSOPV8 group compared with calves in other groups.

Implications and Applications

Contrary to previ- ous reports, intraportal and intrajugular inoculation with F. necrophorum did not produce liver abscesses in preru- minant calves. Further research is necessary to explore alternative methodologies to use preruminant calves in experimental disease models for liver abscesses in cattle.