Effects of crude protein concentration and degradability on performance, carcass characteristics, and serum urea nitrogen concentrations in finishing beef steers

High deoxynivalenol and ergot alkaloid levels in wheat grain: effects on growth performance, carcass traits, rumen fermentation, and blood parameters of feedlot cattle

This study was designed to assess the impacts of a mixture of deoxynivalenol (DON) and ergot alkaloids (EAs) on growth performance, rumen function, blood parameters, and carcass traits of feedlot cattle. Forty steers (450 ± 6.0 kg) were stratified by weight and randomly allocated to 1 of 4 treatments; control-low (CON-L), control-high (CON-H) which contained low or high wheat screenings that lacked mycotoxins at the same level as the mycotoxin-low (MYC-L; 5.0 mg/kg DON, 2.1 mg/kg EA), and mycotoxin-high (MYC-H: 10 mg/kg DON, 4.2 mg/kg EA) diets that included wheat screening with mycotoxins. Steers were housed in individual pens for a 112-day finishing trial. Intake was 24.8% lower (P < 0.001) for MYC steers compared to CON steers. As a result, average daily gains of MYC steers were 42.1% lower (P < 0.001) than CON steers. Gain to feed ratio was also lower (P < 0.001) for MYC steers compared to CON steers. Platelets, alanine aminotransferase, globulins, and blood urea nitrogen were lower (P ≤ 0.008), and lymphocytes, glutathione peroxidase activity (GPx), and interleukin-10 (IL-10) were elevated (P ≤ 0.002) in MYC steers compared to CON steers. Hot carcass weights and backfat thickness were reduced (P < 0.001) in MYC steers, resulting in leaner (P < 0.001) carcasses and higher (P < 0.007) meat yield compared to CON steers. Results suggest that a mixture of DON and EAs negatively impacted health, performance, and carcass traits of feedlot steers, with the majority of this response likely attributable to EAs. However, more research is needed to distinguish the relative contribution of each mycotoxin to the specific responses observed.

Nutritional Performance of Grazing Beef Cattle Supplemented with High-Protein Distillers' Dried Grain

The objective was to evaluate the effects of including high-protein distillers dried grains (HP-DDG; 430 g/CP) in supplements for beef cattle in an intensive finishing pasture system. Five Nellore bulls with an average body weight (BW) of 413.5 ± 32 kg were distributed in a 5 × 5 Latin square design. The animals were randomly allocated to Marandu palisade grass paddocks (Urochloa brizantha cv. Marandu), with 0.32 ha each. Protein-energy supplements were evaluated and formulated with different replacement levels (0, 250, 500, 750 and 1000 g/kg) of soybean meal (SBM) by HP-DDG. Supplements were offered once a day in the amount of 6.0 kg/animal. Replacing SBM with HP-DDG had no effect (p > 0.10) on the intake of total and pasture DM, OM, CP, NDFap, digestible organic matter (DOM), metabolizable protein and CP:DOM ratio. Total and pasture DM intake averaged 6.07 and 11.54 kg/day, respectively. Replacing SBM with HP-DDG reduces and increases, respectively, the intake of degradable (RDP) and undegradable (RUP) protein in the rumen (p < 0.10) with a consequent linear reduction in ruminal ammonia concentration (RAN), nitrogen excretion in urine and serum N concentration (SUN) (p < 0.10). In supplements offered in the amount of 6.0 kg animal/day, SBM can be completely replaced by HP-DDG.

Effects of protein concentration and beta-adrenergic agonists on ruminal bacterial communities in finishing beef heifers

To improve animal performance and modify growth by increasing lean tissue accretion, beef cattle production has relied on use of growth promoting technologies such as beta-adrenergic agonists. These synthetic catecholamines, combined with the variable inclusion of rumen degradable (RDP) and undegradable protein (RUP), improve feed efficiency and rate of gain in finishing beef cattle. However, research regarding the impact of beta-adrenergic agonists, protein level, and source on the ruminal microbiome is limited. The objective of this study was to determine the effect of different protein concentrations and beta-adrenergic agonist (ractopamine hydrochloride; RAC) on ruminal bacterial communities in finishing beef heifers. Heifers (n = 140) were ranked according to body weight and assigned to pens in a generalized complete block design with a 3 × 2 factorial arrangement of treatments of 6 different treatment combinations, containing 3 protein treatments (Control: 13.9% CP, 8.9% RDP, and 5.0% RUP; High RDP: 20.9% CP, 14.4% RDP, 6.5% RUP; or High RUP: 20.9% CP, 9.7% RDP, 11.2% RUP) and 2 RAC treatments (0 and 400 mg/day). Rumen samples were collected via orogastric tubing 7 days before harvest. DNA from rumen samples were sequenced to identify bacteria based on the V1-V3 hypervariable regions of the 16S rRNA gene. Reads from treatments were analyzed using the packages 'phyloseq' and 'dada2' within the R environment. Beta diversity was analyzed based on Bray-Curtis distances and was significantly different among protein and RAC treatments (P < 0.05). Alpha diversity metrics, such as Chao1 and Shannon diversity indices, were not significantly different (P > 0.05). Bacterial differences among treatments after analyses using PROC MIXED in SAS 9 were identified for the main effects of protein concentration (P < 0.05), rather than their interaction. These results suggest possible effects on microbial communities with different concentrations of protein but limited impact with RAC. However, both may potentially act synergistically to improve performance in finishing beef cattle.

Effects of Dietary Crude Protein Level of Concentrate Mix on Growth Performance, Rumen Characteristics, Blood Metabolites, and Methane Emissions in Fattening Hanwoo Steers

This study aimed to investigate the effect of varying levels of dietary crude protein (CP) on growth performance, rumen characteristics, blood metabolites, and methane emissions in fattening Hanwoo steers. Twenty-four steers, weighing 504 ± 33.0 kg (16 months old), were assigned to four dietary treatments with different CP concentrations (15, 18, 19, and 21% of CP on a dry matter (DM) basis). A linear increasing trend in the average daily gain (ADG) was observed (p = 0.066). With increased dietary CP levels, the rumen ammonia concentration significantly increased (p < 0.001), while the propionate proportion linearly decreased (p = 0.004) and the proportions of butyrate and valerate linearly increased (p ≤ 0.003). The blood urea exhibited a linear increase (p < 0.001), whereas the blood non-esterified fatty acids and cholesterol showed a linear decrease (p ≤ 0.003) with increasing dietary CP. The methane concentration from eructation per intake (ppm/kg), forage neutral detergent fiber (NDF) intake, total NDF intake, and ADG exhibited linear decreases (p ≤ 0.014) across the treatments. In conclusion, increasing the dietary CP up to 21% in concentrates demonstrated a tendency to linearly increase the ADG and significantly decrease the propionate while increasing the butyrate. The methane concentration from eructation exhibited a tendency to linearly decrease with increasing dietary CP.

Beta-Adrenergic Agonists, Dietary Protein, and Rumen Bacterial Community Interactions in Beef Cattle: A Review

Improving beef production efficiency, sustainability, and food security is crucial for meeting the growing global demand for beef while minimizing environmental impact, conserving resources, ensuring economic viability, and promoting animal welfare. Beta-adrenergic agonists and dietary protein have been critical factors in beef cattle production. Beta-agonists enhance growth, improve feed efficiency, and influence carcass composition, while dietary protein provides the necessary nutrients for muscle development and overall health. A balanced approach to their use and incorporation into cattle diets can lead to more efficient and sustainable beef production. However, microbiome technologies play an increasingly important role in beef cattle production, particularly by optimizing rumen fermentation, enhancing nutrient utilization, supporting gut health, and enhancing feed efficiency. Therefore, optimizing rumen fermentation, diet, and growth-promoting technologies has the potential to increase energy capture and improve performance. This review addresses the interactions among beta-adrenergic agonists, protein level and source, and the ruminal microbiome. By adopting innovative technologies, sustainable practices, and responsible management strategies, the beef industry can contribute to a more secure and sustainable food future. Continued research and development in this field can lead to innovative solutions that benefit both producers and the environment.

Effect of Potato Vine and Leaf Mixed Silage Compared to Whole Corn Crops on Growth Performance, Apparent Digestibility, and Serum Biochemical Characteristics of Fattening Angus Bull

This study aims to explore the different growth performances of the Angus bull on potato vine and leaf mixed silage in the early fattening period and to provide a reference animal production trial. Thirty-six 13-month-old Angus bulls were divided into three groups with 403.22 ± 38.97 kg initial body weight and fed with three different silage diets: (1) control: whole-plant corn silage as control (CS); (2) treatment 1: 50% whole-plant corn +50% potato vine and leaf silage (PVS1); and (3) treatment 2: 75% potato vine and leaf +15% rice straw +10% cornmeal silage (PVS2). After the 14 days pre-feeding, the formal experiment was carried out for 89 days. The result showed that the ash content of the potato vine and leaf mixed silage (PVS) in the treatment groups was higher than that in control group, and the ash content of PVS1 and PVS2 even reached 10.42% and 18.48% (DM%), respectively, which was much higher than that of the CS group at 4.94%. The crude protein content in silage also increased with the additional amount of potato vine and leaf. The apparent crude protein digestibility of the PVS groups was also significantly higher than that of the CS group (p < 0.05). In terms of serum biochemical indexes, blood urea nitrogen (BUN) in the experimental groups was significantly higher than in the control group (p < 0.05). Compared with PVS2, cholesterol (CHO) was significantly lower in the CS and PVS1 groups (p < 0.05). Moreover, the high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) of PVS2 were significantly higher than those of the CS and PVS1 group (p < 0.05), and daily gain (ADG) as a key production index had a significantly negative correlation with the CHO (r = -0.38, p < 0.05) and HDL-C (r = -0.40, p < 0.05) of cattle. In conclusion, PVS had higher crude protein content and ash but less starch than whole-corn silage. The PVS could replace whole-plant corn silage at the same dry matter status and did not affect the weight gain in this trial.

Effects of crude protein and neutral detergent fiber percentages in the diet of Japanese Black steers on rumen fluid properties, blood biochemical properties, and carcass characteristics

The effects of crude protein (CP) and neutral detergent fiber (NDF) percentages in the diet of Japanese Black steers on rumen fluid properties, blood biochemical properties, and carcass characteristics were examined. Twelve 13-month-old Japanese Black steers were used for this study and slaughtered at 30 months of age. Steers were assigned to a control group (n = 6) and test group (n = 6) and were fed a concentrate containing 12.9%-13.9% CP and 26.5%-29.8% NDF or 9.1%-9.6% CP and 29.9%-31.2% NDF, respectively. Lipopolysaccharide activity levels in rumen fluid were lower in the test group than in the control group. Plasma urea nitrogen concentration and activities of aspartate aminotransferase and γ-glutamyltransferase remained lower in the test group than in the control group. In contrast, plasma vitamin A concentrations remained higher in the test group than in the control group. Carcass characteristics did not significantly differ between the two groups. These results suggest that dietary CP and NDF percentages in feed for Japanese Black steers older than 13 months of age affected rumen fluid properties and blood biochemical properties, indicating a reduced load on the liver with a small effect on carcass characteristics.

Chemical Group-Based Metabolome Analysis Identifies Candidate Plasma Biomarkers Associated With Residual Feed Intake in Beef Steers

We applied chemical group-based metabolomics to identify blood metabolic signatures associated with residual feed intake in beef cattle. A group of 56 crossbred growing beef steers (average BW = 261.3 ± 18.5 kg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for period of 49 d to determine their residual feed intake classification (RFI). After RFI determination, weekly blood samples were collected three times from beef steers with the lowest RFI [most efficient (HFE); n = 8] and highest RFI and least-efficient [least efficient (LFE); n = 8]. Plasma was prepared by centrifugation and composited for each steer. Metabolome analysis was conducted using a chemical isotope labeling (CIL)/liquid chromatography–mass spectrometry, which permitted the analysis of metabolites containing amine/phenol-, carboxylic acid-, and carbonyl-chemical groups, which are metabolites associated with metabolisms of amino acids, fatty acids, and carbohydrates, respectively. A total number of 495 amine/phenol-containing metabolites were detected and identified; pathway analysis of all these metabolites showed that arginine biosynthesis and histidine metabolism were enriched (P &lt; 0.10) in HFE, relative to LFE steers. Biomarker analyses of the amine/phenol-metabolites identified methionine, 5-aminopentanoic acid, 2-aminohexanedioic acid, and 4-chlorolysine as candidate biomarkers of RFI [false discovery rate ≤ 0.05; Area Under the Curve (AUC) &gt; 0.90]. A total of 118 and 330 metabolites containing carbonyl- and carboxylic acid-chemical groups, respectively were detected and identified; no metabolic pathways associated with these metabolites were altered and only one candidate biomarker (methionine sulfoxide) was identified. These results identified five candidate metabolite biomarkers of RFI in beef cattle which are mostly associated with amino acid metabolism. Further validation using a larger cohort of beef cattle of different genetic pedigree is required to confirm these findings.

High-level dietary crude protein decreased backfat thickness and increased carcass yield score in finishing Hanwoo beef cattle (Bos taurus coreanae)

Recently, a high level of dietary crude protein (CP) has become of interest as a possible practice to improve the carcass quality of beef cattle, and its level has been increasing in the field. However, there is little scientific evidence that supports this. This study was conducted to test whether a high dietary CP level would improve growth performance, body metabolism, and carcass traits in Hanwoo beef cattle. A total of 32 Hanwoo finishing beef cattle (18 multiparous cows, six heifers, and eight steers) participated in a 12-weeks feeding trial. Two kinds of total mixed rations were prepared to contain two different CP; 156 g/kg for the control (CON) and 173 g/kg of CP for the treatment (HCP), while maintaining a similar level of metabolizable energy. The experiment was ended when more than half of the steers reached the target body weight (730 kg). Blood was collected at the end of the experiment. After harvesting, the carcass trait was evaluated at the slaughterhouse according to Korean standards. The carcass yield score and grade were also calculated based on revised criteria. Overall, dry matter intake, average daily gain, blood metabolites concentration, and the carcass traits, except for backfat thickness and the yield score, did not differ between the treatments. The HCP had lower backfat thickness than those of CON. There was no difference in the carcass yield grade, but the yield score was higher in the HCP treatment. According to the newly revised carcass grading criteria, both yield score and grade were higher in HCP than in CON. Increasing CP supply decreased the carcass’s backfat thickness without altering growth performance and body metabolism, resulting in improved yield score and grade. Therefore, feeding a high CP diet may be beneficial in the farm income, although it may also increase feed cost and nitrogen excretion to the environment.

Effects of low-crude protein diets supplemented with rumen-protected lysine and methionine on fattening performance and nitrogen excretion of Holstein steers

The objective of this experiment was to investigate the effects of low-crude protein (CP) diets supplemented with rumen-protected lysine and methionine on growth performance, nitrogen excretion, and carcass traits in Holstein steers. Steers consumed the following diets: (1) 17.2% CP on a dry-matter basis during the early period (from 7 to 10 months of age) and 14.5% CP during the late period (from 10 to 18 months of age; CON, n = 4, initial body weight [BW] 238 kg), and (2) 14.4% CP during the early period and 11.4% CP during the late period (AA, n = 4, initial BW 243 kg). The AA diet contains rumen-protected lysine and methionine. Except for CP intake, feed intake and body weight gain were not affected by dietary CP content. Total nitrogen excretion per metabolic BW tended to be lower (p < .10) in the early period and significantly lower (p < .05) in the late period with decreasing the feed CP content. Plasma urea nitrogen concentrations were lower in AA than CON. Carcass traits and total free amino acid contents of the longissimus thoracis muscle were not affected by dietary CP content. Adding rumen-protected lysine and methionine to a low-CP diet would reduce nitrogen excretion in fattening Holstein steers without affecting productivity.

Effects of dry yeast supplementation on growth performance, rumen fermentation characteristics, slaughter performance and microbial communities in beef cattle

This study aimed to investigate the effects of active dry yeast (ADY) on growth performance, rumen microbial composition and carcass performance of beef cattle. Thirty-two finishing beef cattle (yak ♂ × cattle-yaks ♀), with an average body weight of 110 ± 12.85 kg, were randomly assigned to one of four treatments: the low plane of nutrition group (control), low plane of nutrition group + ADY 2 g/head daily (ADY2), low plane of nutrition group + ADY 4 g/head daily (ADY4) and the high plane of nutrition group (HPN). Supplementation of ADY increased average daily gain compared to the control group. The neutral detergent fiber and acid detergent fiber apparent digestibility in HPN group was greater than that in control group. The propionic acid concentration in the rumen in ADY2, ADY4, and HPN groups was greater than that in control group. The Simpson and Shannon indexes in control and HPN groups were higher than that in ADY4 group. At the phylum level, the relative abundance of Firmicutes in the HPN group was higher than that in ADY4 group. The relative abundance of Ruminococcaceae UCG-002 in ADY4 group was higher than that in control and HPN groups. In conclusion, supplementation ADY 4 g/head daily shift the rumen microbial composition of beef cattle fed low plane of nutrition to a more similar composition with cattle fed with HPN diet and produce the similar carcass weight with HPN diet.HighlightsThe ADY can improve the utilization of nitrogen and decrease the negative impact on the environment in beef cattle.Cattle fed low plane of nutrition diet supplemented with ADY 4 g/head daily increased growth performance.Supplementation ADY 4 g/head daily in low plane of nutrition diet might be produced comparable carcass weight to HPN diet.

The effect of complete feed to carcass characteristics and meat quality of male Bali cattle fattened in West Timor, Indonesia

Aim:

This research aimed to know the effect of the use of complete feed on Bali cattle fattening performance seen from the carcass characteristics.

Materials and Methods:

The cattle employed in this research were 12 male Bali cattle aged between 2 and 2.5 years old based on the teeth estimation. The average initial body weight of the cattle during the research was 181.50±16.51 kg. The complete feed contained Gliricidia sepium, natural grass, ground corn, bran pollard, and rice bran which have been compiled into three types of ration of T1, T2, and T3. The T₁ ration contained standard crude protein (CP) and high energy (11% CP; 72% total digestible nutrient [TDN]), and T₂ contained medium protein and high energy (13% CP; 72% TDN), while T₃ ration contained high protein and high energy (%15 CP; 72% TDN).

Results:

The meat percentage of T2 and T3 was relatively the same, but higher than T1 (p<0.05). The bone percentage and meat: A bone ratio of T2 was higher than T1; in contrast, and T3 was relatively the same with T2 and T1 (p<0.05). The weight of slaughter, carcass percentage, and weight of meat, bone, and fat were relatively the same among the treatments.

Conclusion:

The application of complete feed with protein source from G. sepium with CP and TDN of 13 and 72%, respectively, can improve carcass percentage and meat: A bone ratio of male Bali cattle fattening. The treatments have not had a positive effect on slaughter weight (kg), hot and cool carcass weight (kg), meat and fat weight (kg), fat percentage, and non-carcass (kg).

Influence of dietary crude protein content on fattening performance and nitrogen excretion of Holstein steers

The objective was to investigate the influence of crude protein (CP) content in a fattening diet on feed intake, body weight gain, nitrogen excretion, and carcass traits in Holstein steers. Steers (initial body weight 241 ± 26 kg) consumed feed with the following CP content: (a) 17.7% during the early period (from 7 to 10 months of age) and 13.9% during the late period (from 11 to 18 months of age) (HIGH, n = 3), and (b) 16.2% during the early period and 12.2% during the late period (LOW, n = 4). The CP intake was lower in the LOW than the HIGH group. Urinary and total nitrogen excretion in the late period tended to be lower (p < .10) in the LOW than the HIGH group. However, growth performance and carcass traits were not affected by dietary CP content. Free histidine and total amino acid contents in the longissimus thoracis muscle tended to be higher (p < .10) in the HIGH than the LOW group, however, the CP contents were not affected by dietary CP content. The results of this experiment suggest that decreasing dietary CP to 16% (early period) or 12% (late period) of dry matter would reduce nitrogen excretion from Holstein fattening farms without affecting productivity.

Effect of metabolizable protein intake on growth performance, carcass characteristics, and feeding behavior in finishing steers

One-hundred thirty-two finishing steers (300 ± 2.7 kg body weight [BW]) predominately of Angus, Simmental, and Shorthorn breeding were used to study the effect of metabolizable protein (MP) intake on growth performance, carcass characteristics, and feeding behavior. Steers were stratified by initial BW across five pens and randomly assigned to one of four dietary treatments to supply an average of 626, 906, 1,209, and 1,444 g MP/d (n = 33 per treatment). Feed intake and feeding behavior were measured using radio frequency identification tags and the Insentec feeding system. For feeding behavior, a visit was defined as each time the Insentec system detected a steer at the feed bunk. A meal was defined as eating periods by intervals no longer than 7 min. Steers were fed until they reached an average BW of 598 ± 3.1 kg. Average daily gain (ADG) responded quadratically (P < 0.01) with ADG increasing in steers fed 906 g MP/d and plateauing thereafter. Dry-matter intake (DMI; kg) responded quadratically (P = 0.009) with DMI increasing with MP intake up to 1,209 g/d MP and decreasing thereafter. Gain to feed ratio (G:F) increased linearly (P = 0.04) and tended (P = 0.10) to respond quadratically, as G:F increased up to 906 g MP/d and plateaued thereafter. A quadratic response (P = 0.04 and P = 0.02, respectively) was observed for marbling score and 12th rib subcutaneous fat thickness with steers fed 1,209 g MP/d having the greatest marbling score and back fat thickness. A quadratic effect for visits and meals per day was observed (P < 0.01) with steers fed the 1,209 g MP/d treatment having the least visits and meals per day. In addition, time eating per visit responded quadratically (P = 0.05) with time increasing from 626 to 906 g MP/d. There was a linear increase (P ≤ 0.02) in time eating per meal and per day with increasing MP intake. A quadratic effect (P < 0.03) was observed for DMI per visit, meal, and minute with steers fed 1,209 g MP/d having the greatest DMI. In summary, steers fed 626 g MP/d had increased visits and meals per day. However, DMI per visit, meal, and minute were greater in steers fed 1,209 g MP/d. A day × treatment interaction (P < 0.001) was observed for plasma urea N as concentrations increased to a greater extent over time in the higher MP treatments than in the lower MP treatments. These data indicate that MP supply (from deficient to excess) influences growth performance, carcass characteristics, and feeding behavior of finishing steers.

Effect of Two Nutritional Strategies to Balance Energy and Protein Supply in Fattening Heifers on Performance, Ruminal Metabolism, and Carcass Characteristics

Latin America is an important contributor to the worldwide beef business, but in general, there are limited studies considering strategies to reduce nitrogen contamination in their production systems. The study's goal was to assess the effect of two nutritional strategies to balance energy and protein supply in fattening heifers on performance, ruminal metabolism, and carcass characteristics. A total of 24 crossbred heifers (initial body weight 'BW 'of 372 ± 36 kg) were used to create two blocks (based on live weight) of two pens each, that were equipped with individual feeders. Within each block, half of the animals were assigned to a diet based on tabular Crude Protein (CP) requirements denominated Crude Protein Diet 'CPD' but without a ruminal degradable protein balance. The other half received a diet denominated Metabolizable Protein Diet 'MPD', formulated with the metabolizable protein system, balanced for the ruminal degradable protein. Both diets had the same ingredients and as well as similar synchrony indexes (0.80 and 0.83, respectively). For nitrogen concentration in feces and urine as well as microbial crude protein synthesis, a total of 12 heifers (three per pen) were randomly selected to collect samples. The dataset was analyzed as a randomized complete block design with a 5% significance. No diet × time interaction was observed for Average Daily Gain 'ADG' (p = 0.89), but there was an effect of the time on ADG (p ≤ 0.001). No differences were observed neither for final weight, dry matter intake 'DMI', and feed conversion rate (p > 0.05). Heifers fed with CPD showed greater cold carcass weight (p = 0.041), but without differences in ribeye area, backfat thickness, pH, dressing %, and marbling (p > 0.05). Differences between diets were observed for the in vitro parameters as well as for the Total Volatile Fatty Acids 'VFA' and NH3 (p < 0.05). Total N concentrations (urine + feces) of heifers fed with MDP was lower than in those fed with the CPD (p < 0.01), but no differences were observed in microbial protein, purine derivatives, and creatinine (p > 0.05). We conclude that the combination of synchrony and the metabolizable protein system achieve greater efficiency in the use of nitrogen, without negatively affecting animals' performance or the quality of the carcass.

Effect of crude protein content and undegraded intake protein level on productivity, blood metabolites, carcass characteristics, and production economics of Hanwoo steers

Objective

This study was designed to determine how feeding diets differing in crude protein (CP) and undegraded intake protein (UIP) levels affected productivity, blood metabolites, carcass characteristics, and the production economics of Hanwoo steers.

Methods

Thirty-six Hanwoo steers (age = 8.2±0.5 mo; body weight = 254±16.1 kg) were assigned at random to one of three treatments (4 steers/pen; 3 pens/treatment): i) a low-CP diet (LP; control) containing 12.1% CP with 35.1% UIP, 12.0% CP with 36.8% UIP, and 12.9% CP with 48.8% UIP, in the growing, fattening, and finishing periods, respectively; ii) a high-CP, low-UIP diet (HPLU) containing 15.0% CP with 33.7% UIP, 14.0% CP with 35.7% UIP, and 13.1% CP with 46.7% UIP, respectively; and iii) a high-CP, high-UIP diet (HPHU) containing 15.0% CP with 45.8% UIP, 14.0% CP with 44.6% UIP, and 13.0% CP with 51.1% UIP, respectively.

Results

The treatments did not affect feed intake and growth performance, except for average daily gain during the fattening period that tended to be the lowest (p = 0.08) in the HPLU-fed steers. The feed CP conversion ratio over the entire feeding period was higher with high-CP diets. The treatments did not affect most blood metabolites; however, blood cholesterol and low-density lipoprotein concentrations during the fattening and finishing periods were the lowest in steers fed a HPLU diet. The treatments had negligible effects on cold carcass weight, yield traits including longissimus muscle area, backfat thickness, yield index, and yield grade, plus quality traits including meat color, fat color, texture, and maturity. However, marbling score and frequency of carcass quality grade 1⁺⁺ were greater in HPHU-fed steers.

Conclusion

Feeding diets with higher CP and UIP levels did not affect growth performance but tended to improve the carcass quality of Hanwoo steers, resulting in greater economic return.

Effects of Decreasing Dietary Crude Protein Level on Growth Performance, Nutrient Digestion, Serum Metabolites, and Nitrogen Utilization in Growing Goat Kids (Capra hircus)

Simple Summary

Reducing the dietary protein content could potentially reduce losses of nitrogen from ruminant farms and mitigate pressure on the protein ingredient supply. However, there is little information in the literature on the effect of low-protein diets in growing Anhui white goat kids. We demonstrated that decreasing the dietary crude protein level in Anhui white goat kids affected growth performance, improved nitrogen utilization, and reduced environmental nitrogen pollution. The key finding of this study was that a diet containing 13.4% crude protein supplied adequate protein to improve nitrogen utilization in white goat kids without any adverse effect on growth performance.

Abstract

The effects of decreasing dietary crude protein (CP) level on growth performance, nutrient digestion, serum metabolites, and nitrogen utilization in growing goat kids were investigated in the current study. Thirty-six male Anhui white goat kids were randomly assigned to one of three CP content diets: 14.8% (control), 13.4%, and 12.0% of dry matter, respectively. Diets were isoenergetic. The experiment lasted for 14 weeks, with the first two weeks being for adaptation. Results showed that the low-CP diet decreased average daily gain, feed efficiency, digestibility of dry matter, organic matter, crude protein, and fiber. No significant changes were observed in dry-matter intake. With a decrease in dietary CP level, fecal nitrogen excretion (% of nitrogen intake) increased linearly, whereas CP intake, blood urea nitrogen, urinary nitrogen excretion (% of nitrogen intake), and total nitrogen excretion (% of nitrogen intake) decreased. Serum glucose concentration decreased, while concentrations of low-density lipoproteins and non-esterified fatty acids increased with the low-CP diet. In conclusion, decreasing the dietary CP level decreased goats’ nitrogen excretion, but with restrictive effects on growth performance. A diet containing 13.4% CP is optimal for reducing nitrogen excretion without any adverse effect on growth performance of Anhui white goat kids. This concentration is 1.4% points lower than the NRC recommendations and thus is also environmentally beneficial on the input side because it decreases the use of feed (soy) protein.

The Effects of Decreasing Dietary Crude Protein on the Growth Performance, Feed Efficiency and Meat Quality of Finishing Charolais Bulls

This study aimed to evaluate the effect of decreasing dietary crude protein (CP) on the performance of finishing Charolais bulls in the Italian rearing system. Animals were fed two diets, differing only in the CP level (low protein (LP), 13.5% CP versus control (CON), 15.0% CP). Dry matter (DM) intake (DMI) and animals' weights were recorded to obtain average daily gain (ADG) and feed conversion rate (FCR). Feed and fecal samples were collected to evaluate digestibility of diet components. Daily cost of the ration (DRC), feed cost per kg of daily weight gain (CDG) and daily gross margin (DGM) were calculated to analyze the possible benefits of decreasing the protein level. Meat quality analyses were also conducted. Higher DMI (10.6 versus 10 kg/d; p < 0.05) and ADG (1.47 versus 1.36 kg/d; p < 0.05) were observed for CON. No differences in FCR or digestibility were found. Even if the DRC was lower (p < 0.05) for the LP diet (2.26 versus 1.97 €; CON versus LP), no difference was reported for CDG and DGM. Meat lightness and redness were significantly lower and higher in the LP, respectively. To conclude, the CP requirement in these rearing conditions appeared to be higher than 13.5%.

Effects of wet corn distiller's grains with solubles and nonprotein nitrogen on feeding efficiency, growth performance, carcass characteristics, and nutrient losses of yearling steers12

Wet distiller's grains with solubles (WDGS) are a common by-product feedstuff generated by the grain-ethanol industry, and it is used extensively by the cattle feeding industry. Distillers grains are typically high in protein; however, the protein in WDGS has a low ruminal degradability, and thus may result in a deficiency of RDP in the diet even when dietary CP concentrations are high. Assessment of the RDP needs in diets containing WDGS is needed to aid the cattle feeding industry in managing feed costs and potential environmental issues. To that end, we conducted 2 feeding studies to evaluate the supplemental RDP requirements of beef cattle fed steam-flaked corn-based finishing diets. In Exp. 1, 525 yearling steers (initial body weight = 373 ± 13 kg) received treatments in a 2 × 3 + 1 factorial. Dietary factors included WDGS (15 or 30% of DM) and nonprotein N (NPN; 0, 1.5, or 3.0% of DM) from urea (0, 0.52, and 1.06%). The control diet without WDGS contained 3.0% NPN (1.06% urea) and cottonseed meal. Diets were formulated to have equal crude fat concentrations. Overall gain efficiency among steers fed 15% WDGS was greatest for 1.5% NPN and least for 0% NPN (P = 0.07, quadratic), whereas gain efficiency decreased linearly (P < 0.09) as NPN increased in the 30% WDGS diets. Dressing percent was greater (P < 0.01) for the Control diet than for 15 or 30% WDGS. In Exp. 2, 296 steer calves (initial BW = 344 ± 12 kg) were fed 1 of 4 experimental diets that included a Control diet without WDGS (contained 3% NPN from urea, and cottonseed meal) and 15% WDGS diets with either 1.50, 2.25, or 3.00% NPN (0.52, 0.78, and 1.04% urea, respectively, on a DM basis). Overall gain efficiency on either a live or carcass-adjusted basis was not different among treatments (P > 0.15). Dietary NPN concentration did not influence growth performance (P > 0.21). Increasing dietary WDGS concentration resulted in decreasing (P < 0.05) diet digestibility (determined with an internal marker) and increasing (P < 0.05) N volatilization losses (determined by diet and manure N:P ratio); however, the effects of NPN level on digestibility and N losses were somewhat inconsistent across experiments. Results suggest that optimum performance for cattle fed 15% WDGS occurred when the diet contained between 1.5 and 2.25% NPN. However, no supplemental NPN was needed to support optimum performance in diets containing 30% WDGS.

Oscillating and static dietary crude protein supply. I. Impacts on intake, digestibility, performance, and nitrogen balance in young Nellore bulls

Effects of dietary crude protein (CP) supply on intake, digestibility, performance, and N balance were evaluated in young Nellore bulls consuming static or oscillating CP concentrations. Forty-two young bulls (initial BW of 260 ± 8.1 kg; age of 7 ± 1.0 mo) were fed ad libitum and were randomly assigned to receive one of six diets with different CP concentrations for 140 d: 105 (LO), 125 (MD), or 145 g CP /kg DM (HI), and LO to HI (LH), LO to MD (LM), or MD to HI (MH) oscillating CP at a 48-h interval for each feed. At the end of the experiment, bulls were slaughtered to evaluate carcass characteristics. Linear and quadratic effects were used to compare LO, MD, and HI, and specific contrasts were applied to compare oscillating dietary CP treatments vs. MD (125 g CP/kg DM) static treatment. Dry matter intake (DMI) was not affected (P > 0.26) by increasing or oscillating dietary CP. As dietary N concentration increased, there was a subsequent increase in apparent N compounds digestibility (P = 0.02), and no significant difference (P = 0.38) was observed between oscillating LH and MD. Daily total urinary and fecal N increased (P < 0.01) in response to increasing dietary CP. Significant differences were observed between oscillating LM and MH vs. MD, where bulls receiving the LM diet excreted less (P < 0.01; 71.21 g/d) and bulls fed MH excreted more (P < 0.01) urinary N (90.70 g/d) than those fed MD (85.52 g/d). A quadratic effect was observed (P < 0.01) for retained N as a percentage of N intake, where the bulls fed LO had greater N retention than those fed HI, 16.20% and 13.78%, respectively. Both LH and LM had greater (P < 0.01) daily retained N when compared with MD. Performance and carcass characteristics were not affected (P > 0.05) by increasing or oscillating dietary CP. Therefore, these data indicate that although there is no alteration in the performance of growing Nellore bulls fed with oscillating CP diets vs. a static level of 125 g CP/kg DM, nor static low (105 g CP/kg DM) and high (145 g CP/kg DM) levels; there may be undesirable increases in environmental N excretion when the average dietary CP content is increased. The results suggest that dietary CP concentrations of 105, 125 g/kg DM, or within this range can be indicated for finishing young Nellore bulls, since it reaches the requirements, reduces the environmental footprint related to N excretion, and may save on costs of high-priced protein feeds.

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

Formulating diets conservatively for minimum crude-protein (CP) requirements and overfeeding nitrogen (N) is commonplace in grain finishing rations in USA, Canada and Australia. Overfeeding N is considered to be a low-cost and low-risk (to cattle production and health) strategy and is becoming more commonplace in the US with the use of high-N ethanol by-products in finishing diets. However, loss of N from feedlot manure in the form of volatilised ammonia and nitrous oxide, and nitrate contamination of water are of significant environmental concern. Thus, there is a need to improve N-use efficiency of beef cattle production and reduce losses of N to the environment. The most effective approach is to lower N intake of animals through precision feeding, and the application of the metabolisable protein system, including its recent updates to estimation of N supply and recycling. Precision feeding of protein needs to account for variations in the production system, e.g. grain type, liveweight, maturity, use of hormonal growth promotants and β agonists. Opportunities to reduce total N fed to finishing cattle include oscillating supply of dietary CP and reducing supply of CP to better meet cattle requirements (phase feeding).

Energy costs of feeding excess protein from corn-based by-products to finishing cattle

The increased use of by-products in finishing diets for cattle leads to diets that contain greater concentrations of crude protein (CP) and metabolizable protein (MP) than required. The hypothesis was that excess dietary CP and MP would increase maintenance energy requirements because of the energy costs of removing excess N as urea in urine. To evaluate the potential efficiency lost, two experiments were performed to determine the effects of feeding excess CP and MP to calves fed a finishing diet at 1 × maintenance energy intake (Exp. 1) and at 2 × maintenance intake (Exp. 2). In each experiment, eight crossbred Angus-based steers were assigned to two dietary treatments in a switchback design with three periods. Treatments were steam-flaked corn-based finishing diets with two dietary protein concentrations, 13.8% CP/9.63% MP (CON) or 19.5% CP/14.14% MP (dry matter basis; ECP), containing corn gluten meal to reflect a diet with excess CP and MP from corn by-products. Each period was 27 d in length with a 19-d dietary adaptation period in outdoor individual pens followed by a 4-d sample collection in one of four open circuit respiration chambers, 2-d fast in outdoor pen, and 2-d fast in one of four respiration chambers. Energy metabolism, diet digestibility, carbon (C) and nitrogen (N) balance, oxygen consumption, and carbon dioxide and methane production were measured. At both levels of intake, digestible energy as a proportion of gross energy (GE) tended to be greater (P < 0.06) in ECP than in CON steers. Metabolizable energy (ME) as a proportion of GE tended to be greater (P = 0.08) in the ECP steers than in the CON steers at 2 × maintenance intake. At 1 × and 2 × maintenance intake, urinary N excretion (g/d) was greater (P < 0.01) in the ECP steers than the CON steers. Heat production as a proportion of ME intake at 1 × maintenance tended (P = 0.06) to be greater for CON than for ECP (90.9% vs. 87.0% for CON and ECP, respectively); however, at 2 × maintenance energy intake, it was not different (63.9% vs. 63.8%, respectively). At 1 × maintenance intake, fasting heat production (FHP) was similar (P = 0.45) for both treatments, whereas at 2 × maintenance intake, FHP tended to be greater (P = 0.09) by 6% in ECP than in CON steers. Maintenance energy requirements estimated from linear and quadratic regression of energy retention on ME intake were 4% to 6% greater for ECP than for CON. Results of these studies suggest that feeding excess CP and MP from a protein source that is high in ruminally undegradable protein and low in protein quality will increase maintenance energy requirements of finishing steers.

Effect of increased dietary crude protein levels on production performance, nitrogen utilisation, blood metabolites and ruminal fermentation of Holstein bulls

Objective

This study investigated the effect of dietary crude protein (CP) supplementation on nutrient intake, nitrogen (N) utilisation, blood metabolites, ruminal fermentation and growth performance of young Holstein bulls.

Methods

Twenty-one young bulls weighing 277±11.2 kg were equally divided into three groups and were offered diets formulated with low CP (LCP; 10.21% CP and 4.22% rumen degradable protein [RDP]), medium CP (MCP; 12.35% CP and 5.17% RDP) and high CP (HCP; 14.24% CP and 6.03% RDP). Yellow corn silage was used as a unique forage source and was mixed with concentrate. This mixed feed was given ad libitum to the young bulls included in the study.

Results

Results showed that CP intake, blood urea nitrogen, N intake, total N excretion and N balance increased linearly with an increase in dietary CP level (p<0.05). However, no significant difference was observed in nutrient digestibility among the bulls receiving the different diets. Ruminal pH (p<0.05) and ammonia nitrogen (NH₃-N) concentration (p<0.01) were significantly higher in the bulls receiving the MCP and HCP diets than in those receiving the LCP diet. The bulls receiving the HCP diet showed significantly higher ruminal bacterial protein level, propionate, acetate and total volatile fatty acid (TVFA) concentrations than bulls receiving the LCP diet (p<0.05). Moreover, dietary CP level exerted a significant positive effect on the final body weight, average daily gain and gain-to-feed ratio of the bulls (p<0.05).

Conclusion

High dietary CP level is optimal for achieving maximum growth and high profitability without exerting a negative effect on the physiology of growing Holstein bulls.

The effects of partial substitution of soybean with urea or slow-release urea on finishing performance, meat quality, and digestion parameters of Nellore steers

The effects of substituting ~50% of the soybeans in the diet of finishing Nellore steers with either urea (U) and/or slow-release urea (SRU) on the steer performance and meat quality were assessed in two experiments. In the first experiment, 46 Nellore steers in a 104-day experiment (Exp. 1) were fed a Control diet with U or SRU or U+SRU. In Experiment 2 (Exp. 2), digestibility and microbial protein (MCP) synthesis were assessed in four steers by using a 4 × 4 Latin square design with 21-day periods. Four corn-based diets were used in both Exp. 1 and 2. (1) Control (CTL): 0% of non-protein nitrogen (NPN). (2) U: 1.66% of NPN. (3) SRU: 1.8% of NPN. (4) U+SRU: 1.72% of NPN. In Exp. 1, final bodyweight, average daily gain, dry matter intake, Gain to Feed ratio, carcass traits and steer meat quality were not influenced by the experimental diets. In Exp. 2, the apparent digestibility was similar for all diets, and the MCP synthesis was affected by dietary treatments (P = 0.065). The NPN treatments showed 25.5% more (P = 0.03) MCP efficiency (g microbial protein/kg of total digestible nutrient content consumed) than the CTL. We conclude that the partial replacement of SBM with U, SRU or U+SRU will provide similar animal performance without negatively impacting carcass and meat quality and improve the efficiency of microbial protein synthesis in Nellore cattle.

Effect of condensed tannin extract supplementation on growth performance, nitrogen balance, gas emissions, and energetic losses of beef steers

Condensed tannins (CT) may decrease greenhouse gas emissions and alter the site of N excreted by ruminants. We evaluated the effect of top-dressing a steam-flaked corn-based finishing diet (14.4% CP and NEg 1.47 Mcal/kg) for beef cattle with a commercially available CT extract at 3 levels (0, 0.5, and 1.0% of diet, DM basis). Angus-crossbred steers ( = 27; 350 ± 32 kg initial BW) were individually fed via Calan gates for 126 d. Diet digestibility and N balance were estimated after 34 and 95 d on feed (Phase 1 and Phase 2, respectively) using titanium dioxide as a marker of fecal output and the creatinine:BW ratio as a marker for urine output. Ruminal CH and metabolic CO fluxes were measured using a GreenFeed system (C-Lock Inc., Rapid City, SD) for 2 sampling periods that coincided with fecal and urine sampling. Urine energy loss was estimated from urine N excretion, assuming all excreted N was urea. Oxygen consumption was estimated from CO production assuming a respiratory quotient of 1.05. Average daily gain (2.08, 2.14, and 2.08 kg/d for 0, 0.5, and 1.0% CT, respectively) and G:F did not differ ( = 0.88) among treatments. Starch intake and OM intake did not differ ( ≥ 0.42) among treatments during each phase. Apparent total tract starch digestibility during Phase 1 linearly decreased ( = 0.04) with inclusion of CT. Apparent total tract digestibility of OM and starch were not different among treatments ( ≥ 0.13) during Phase 2. Nitrogen intake did not differ ( ≥ 0.16) among treatments during each phase, but fecal N excretion linearly increased ( = 0.05) with inclusion of CT during Phase 1. Urinary N excretion was not different ( ≥ 0.39) among treatments during both phases, but urinary N as a proportion of total N excretion linearly decreased ( = 0.01) when CT was included in the diet during Phase 1. Retained N was not different ( ≥ 0.27) among treatments during each phase. Fluxes of CO were similar ( ≥ 0.37) among treatments during both phases. No differences ( ≥ 0.23) were observed for percentage of GE intake lost as CH (2.99, 3.12, and 3.09% in Phase 1 and 3.54, 3.55, and 4.35% in Phase 2) for 0, 0.5, and 1.0% CT, respectively. No difference ( ≥ 0.42) was observed for heat production lost as a percent of GE intake during both phases. Growth performance, gas emissions, and energetic losses were not affected by the inclusion CT in a steam-flaked corn-based finishing diet.

Effects of dietary urea concentration and zilpaterol hydrochloride on performance and carcass characteristics of finishing steers

Cattle receiving zilpaterol hydrochloride () may recycle less N and require a greater supply of RDP. This study evaluated effects of ZH on performance and carcass characteristics of steers fed diets with increasing dietary RDP concentrations supplied as urea. Steers (429 animals; BW = 423 ± 4.5 kg) were sorted into 3 blocks according to BW and assigned to 1 of 6 treatments (6 pens per treatment) in a randomized complete block design. Treatments were a 2 × 3 factorial arrangement of either no ZH or ZH (75 mg ZH per steer daily) supplemented to finishing diets containing 0, 0.5, or 1.0% urea of dietary DM. Pen weights were recorded before treatment initiation; urea was fed for 27 d, and ZH treatments were fed for 24 d with a 3-d withdrawal period. Pen weights were recorded before transporting steers to a commercial abattoir. Continuous response variables were analyzed using the MIXED procedure and categorical data were analyzed using the GLIMMIX procedure of SAS. No ZH × dietary urea interactions ( ≥ 0.14) occurred for all performance and carcass response variables. Feeding ZH for the last 27 d (included a 3-d withdrawal period) of the finishing period increased ( < 0.01) ADG, decreased ( < 0.01) DMI, and increased ( < 0.01) G:F compared with no ZH. In addition, ZH increased HCW ( < 0.01), dressing percentage ( < 0.01), LM area ( < 0.01), and decreased ( = 0.01) yield grade. Increasing dietary urea linearly decreased ( = 0.01) ADG and DMI. A tendency for a linear decrease ( = 0.10) in HCW, and a tendency for a quadratic increase ( = 0.07) in marbling score were observed as urea increased in the diet. Results indicate that cattle supplemented with ZH do not require additional RDP in the diet, and that performance and carcass characteristics were negatively affected when urea was increased in the diet.

Supplementation of cattle fed tropical grasses with microalgae increases microbial protein production and average daily gain

A series of 3 experiments were conducted to evaluate the use of microalgae as supplements for ruminants consuming low-CP tropical grasses. In Exp. 1, the chemical composition and in vitro protein degradability of 9 algae species and 4 protein supplements were determined. In Exp. 2, rumen function and microbial protein (MCP) production were determined in steers fed speargrass hay alone or supplemented with , , , or cottonseed meal (CSM). In Exp. 3, DMI and ADG were determined in steers fed speargrass hay alone or supplemented with increasing amounts of NPN (urea combined with ammonia sulfate), CSM, or . In Exp. 1, the CP content of and (675 and 580 g/kg DM) was highest among the algae species and higher than the other protein supplements evaluated, and sp. had the highest crude lipid (CL) content (198 g/kg DM). In Exp. 2, supplementation increased speargrass hay intake, the efficiency of MCP production, the fractional outflow rate of digesta from the rumen, the concentration of NHN, and the molar proportion of branched-chain fatty acids in the rumen fluid of steers above all other treatments. acceptance by steers was low and this resulted in no significant difference to unsupplemented steers for all parameters measured for this algae supplement. In Exp. 3, ADG linearly increased with increasing supplementary N intake from both and NPN, with no difference between the 2 supplements. In contrast, ADG quadratically increased with increasing supplementary N intake from CSM. It was concluded that and may potentially be used as protein sources for cattle grazing low-CP pastures.

Effect of urea supplementation on performance and safety in diets of Dorper crossbred sheep

This study was conducted to evaluate the efficacy and safety of dietary urea in sheep rations having a 50:50 concentrate:roughage ratio. Sixty-four Dorper × thin-tailed Han crossbred ram lambs with an average body weight of 30.8 (±0.02) kg were randomly divided into four groups of 16 sheep each, and each group was fed one of the following diets: a basal diet (CON), or CON supplemented with 0.5% (0.5UTM), 1.5% (1.5UTM) or 2.5% (2.5UTM) urea. Growth performance, carcass characteristics, non-carcass offals, meat quality and peptic tissue lesions were assayed. The average daily weight gains for CON, 0.5UTM, 1.5UTM and 2.5UTM were 216, 218, 200 and 170 g, respectively, with the CON and 0.5UTM groups higher than 2.5UTM group (p < 0.05). Sheep from the 2.5UTM treatment had a significantly lower dry matter intake (1.29 kg/day) than those from the CON and 0.5UTM treatments (1.42 and 1.43 kg/day, p < 0.05), and the feed conversion ratio in the 2.5UTM group was the highest (p < 0.05). Carcass characteristics, including shrunk body weight, empty body weight, hot carcass weight, dress percentage, and the absolute or relative weight (% body weight) of heart, liver, spleen, lung and kidney, were not altered by the treatments (p > 0.05). The muscular pH of 2.5UTM was higher than that of CON (5.68 vs. 5.52, p < 0.05), and shear force in 0.5UTM was lower compared with CON and 2.5UTM (p < 0.05). The anatomical structure lesions in kidneys became more serious with the increasing dietary urea concentrations, with the 2.5UTM animals showing the most severe lesions compared with CON animals. Therefore, supplementary urea as a non-protein nitrogen source for sheep should not exceed 1.5% of ration having a 50:50 concentrate:roughage ratio to ensure efficacy and safety.

Effect of dietary protein on intake, nutrients utilization, nitrogen balance, blood metabolites, growth and puberty in growing Bhadawari buffalo (Bubalus bubalis) heifers

Fifteen Bhadawari buffalo heifers of 207 ± 9.78 kg mean body weight were randomly distributed into three dietary groups to evaluate the effect of protein level on nutrient utilization, nitrogen (N) balance, growth rate, blood metabolites, and puberty. All animals were offered wheat straw-berseem diets supplemented with concentrate mixtures of similar energy (2.7 Mcal/kg) and different protein levels (14.3-22%). Animals of standard-protein group (SPG) were offered protein and energy as per requirement, while animals of low-protein group (LPG) and high-protein group (HPG) were fed 20% less and 20% more protein, respectively, than SPG. Feed dry matter (DM) and metabolizable energy (ME) intake (% body wt. and g/kg w(0.75)) were similar for all three diets; however, the crude protein (CP) and digestible crude protein (DCP) intake on percent body weight and per kilogram metabolic weight was higher (P < 0.05) in HPG than in SPG or LPG. Digestibility of CP, cellulose, and hemicellulose was higher (P < 0.05) in HPG versus LPG. Fecal N excretion was similar, while urinary N excretion was highest (P < 0.05) in HPG (74.83 g/day) compared with SPG (50.03 g/day) and LPG (47.88 g/day), which resulted in lower N retention in HPG than in the other dietary groups. Level of dietary N had no effect on blood metabolites viz. glucose, urea, and N. Digestible energy (DE) and ME contents of diets were identical, while DCP contents were higher (P < 0.05) in HPG than in LPG. Feed and nutrient (CP and ME) conversion efficiency to produce a unit kilogram weight gain was identical among the dietary groups. Dietary protein level had no effect on the heifer's weight and age at puberty. The mean growth rate of heifers at 240 days was higher (P > 0.05) in SPG (330.8 g/day) than in LPG (296.7 g/day), while the animals gained more weight in January to March months and the lowest weight in May to July months. Protein level had no effect on conception rate of heifers. Results revealed that 20% higher or less protein than the ICAR requirement had no significant (P > 0.05) on feed intake, nutrient conversion efficiency for weight gain, heifer growth, and puberty; however, 20% more protein increased urinary N loss.

Effects of Supplementing Microbially-fermented Spent Mushroom Substrates on Growth Performance and Carcass Characteristics of Hanwoo Steers (a Field Study)

This study evaluated the effect of dietary supplementation of microbially-fermented spent mushroom substrates (MFSMS) on weight gain, carcass characteristics, and economic efficiency of Hanwoo steers. Highly cellulolytic bacteria (Enterobacter spp. and Bacillus spp.) isolated from spent mushroom substrates (SMS) stacks were inoculated (1% v/v) into the SMS, which was anaerobically fermented and fed to the steers for 12.6 months during the growing and fattening periods. Growing Hanwoo steers were assigned to the control group without supplementation of Microbially-fermented SMS (MFSMS), to a treatment group with 50% of MFSMS (1/2 of the ad libitum group), and to a treatment group with ad libitum access to SMS (the ad libitum group). All the groups were fed the formulated feed and rice straw. The voluntary intake (DM basis) of MFSMS was 1.6 kg/d during the growing period and 1.4 kg/d during the fattening period. The voluntary rice straw intake decreased by 6 to 11%, but the total voluntary DMI increased by 7 to 15% with MFSMS fed. The increased DMI with MFSMS supplementation resulted in a tendency of increased (p = 0.055) live weight gain by 8 to 12% compared with the control group. At slaughtering, the supplementation of MFSMS increased (p<0.05) the ribeye area by an average of 10 cm(2). In conclusion, feeding MFSMS improved growth performance and carcass traits of Hanwoo steers and could successfully replace a part of conventional roughage such as rice straw commonly used in Asian countries.

Effects of different dietary energy and protein levels and sex on growth performance, carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle

BACKGROUND

The experiment evaluated the effect of nutrition levels and sex on the growth performance, carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle.

METHODS

During the background period of 184 d,23 steers and 24 heifers were fed the same ration,then put into a 2 × 2 × 2 factorial arrangement under two levels of - dietary energy (TDN: 70/80% DM), protein (CP: 11.9/14.3% DM) and sex (S: male/female) during the finishing phase of 146 d. The treatments were - (1) high energy/low protein (HELP), (2) high energy/high protein (HEHP), (3) low energy/low protein (LELP) and (4) low energy/high protein (LEHP). Each treatment used 6 steers and 6 heifers, except for HELP- 5 steers and 6 heifers.

RESULTS

Growth rate and final carcass weight were unaffected by dietary energy and protein levels or by sex. Compared with the LE diet group, the HE group had significantly lower dry matter intake (DMI, 6.76 vs. 7.48 kg DM/d), greater chest girth increments (46.1 vs. 36.8 cm), higher carcass fat (19.9 vs.16.3%) and intramuscular fat content (29.9 vs. 22.8% DM). The HE group also had improved yields of top and medium top grade commercial meat cuts (39.9 vs.36.5%). The dressing percentage was higher for the HP group than the LP group (53.4 vs. 54.9%). Steers had a greater length increment (9.0 vs. 8.3 cm), but lower carcass fat content (16.8 vs. 19.4%) than heifers. The meat quality traits (shear force value, drip loss, cooking loss and water holding capacity) were not affected by treatments or sex, averaging 3.14 kg, 2.5, 31.5 and 52.9%, respectively. The nutritive profiles (both fatty and amino acid composition) were not influenced by the energy or protein levels or by sex.

CONCLUSIONS

The dietary energy and protein levels and sex significantly influenced the carcass characteristics and chemical composition of meat but not thegrowth performance, meat quality traits and nutritive profiles.