Metabolizable amino acids and energy requirements of Nellore and crossbred Angus × Nellore bulls fed rations of different crude protein concentrations

Growth rate of cattle depends on their genetic makeup and nutrient intake. Moreover, increased growth rate may lead to increased amino acid (AA) requirements. Therefore, we evaluated the AA content of the empty body and estimated the net AA and energy requirements of purebred and crossbred beef bulls fed rations of different dietary CP concentrations. We performed a comparative slaughter experiment with 24 Nellore and 24 Angus × Nellore (A × N) bulls (8 months; initial shrunk BW: Nellore = 208.0 ± 12.78 kg; A × N = 221.9 ± 14.16 kg). Eight bulls (four Nellore and four A × N) were designated as the reference group, eight bulls (four Nellore and four A × N) were fed to maintenance level and 32 bulls (16 Nellore and 16 A × N) were fed ad libitum. The 32 bulls fed ad libitum were distributed using a completely randomized design in a 2 × 3 factorial scheme with two genetic groups (Nellore or A × N) and three dietary CP contents (100, 120 or 140 g CP/kg DM), being four groups with five bulls and two groups with six bulls. The experimental period lasted for 224 days. There were no interactions (P ≥ 0.056) between the dietary CP contents and genetic groups for any of the response variables. The dietary CP contents did not affect (P ≥ 0.062) the AA content in the empty body (g/kg empty BW [EBW]), with exception for Tryptophan (P = 0.027, linear effect). The dietary CP contents did not affect (P ≥ 0.051) AA content in the empty body (g/100 g of CP), with exception for Alanine (P = 0.013) that responded quadratically to dietary CP increase. The equations to estimate the net Lysine (Lys) and Methionine (Met) requirements (g/100 g of CP) were: Lys = 5.1 × EBW^0.0594 and Met = 1.7 × EBW^0.0255. Metabolizable Lys and Met to metabolizable energy (ME) ratios decreased as bulls EBW increased. Also, the metabolizable protein to ME ratio decreased as bulls EBW increased. In conclusion, the present study provides useful information regarding net and metabolizable requirements of AA of purebred and crossbred beef bulls. In the future, after the validation of the equations, these results can be used to calculate the AA requirements for growth of purebred and crossbred beef bulls. Nevertheless, it is important to highlight that the small sample size was one limitation of this present experiment.     

Reducing protein content in the diet of growing goats: implications for nitrogen balance,intestinal nutrient digestion and absorption,and rumen microbiota

Reducing dietary CP content is an effective approach to reduce animal nitrogen excretion and save protein feed resources. However, it is not clear how reducing dietary CP content affects the nutrient digestion and absorption in the gut of ruminants, therefore it is difficult to accurately determine how much reduction in dietary CP content is appropriate. This study was conducted to investigate the effects of reduced dietary CP content on N balance, intestinal nutrient digestion and absorption, and rumen microbiota in growing goats. To determine N balance, 18 growing wether goats (25.0 ± 0.5 kg) were randomly assigned to one of three diets: 13.0% (control), 11.5% and 10.0% CP. Another 18 growing wether goats (25.0 ± 0.5 kg) were surgically fitted with ruminal, proximate duodenal, and terminal ileal fistulae and were randomly assigned to one of the three diets to investigate intestinal amino acid (AA) absorption and rumen microbiota. The results showed that fecal and urinary N excretion of goats fed diets containing 11.5% and 10.0% CP were lower than those of goats fed the control diet (P < 0.05). When compared with goats fed the control diet, N retention was decreased and apparent N digestibility in the entire gastrointestinal tract was increased in goats fed the 10% CP diet (P < 0.05). When compared with goats fed the control diet, the duodenal flow of lysine, tryptophan and phenylalanine was decreased in goats fed the 11.5% CP diet (P < 0.05) and that of lysine, methionine, tryptophan, phenylalanine, leucine, glutamic acid, tyrosine, essential AAs (EAAs) and total AAs (TAAs) was decreased in goats fed the 10.0% CP diet (P < 0.05). When compared with goats fed the control diet, the apparent absorption of TAAs in the small intestine was increased in goats fed the 11.5% CP diet (P < 0.05) and that of isoleucine, serine, cysteine, EAAs, non-essential AAs, and TAAs in the small intestine was increased in goats fed the 10.0% CP diet (P < 0.05). When compared with goats fed the control diet, the relative richness of Bacteroidetes and Fibrobacteres was increased and that of Proteobacteria and Synergistetes was decreased in the rumen of goats fed a diet with 10.0% CP. In conclusion, reducing dietary CP content reduced N excretion and increased nutrient utilization by improving rumen fermentation, enhancing nutrient digestion and absorption, and altering rumen microbiota in growing goats.     

Nitrogen partitioning and isotopic discrimination are affected by age and dietary protein content in growing lambs

It is difficult to separate an age-dependent fall in nitrogen use efficiency (NUE; N balance/N intake) in growing ruminants from a progressively decrease in animal protein requirements over time. This study examined the effect of dietary protein content on N partitioning, digestibility and N isotopic discrimination between the animal and its diet (Δ¹⁵N_animal-diet) evaluated at two different fattening periods (early v. late). Twenty-four male Romane lambs (age: 19 ± 4.0 days; BW: 8.3 ± 1.39 kg) were equally allocated to three dietary CP treatments (15%, 17% and 20% CP on a DM basis). Lambs were reared with their mothers until weaning, thereafter housed in individual pens until slaughter (45 kg BW). During the post-weaning period, lambs were allocated twice (early fattening (30 days post-weaning) and late fattening (60 days post-weaning)) to metabolic cages for digestibility and N balance study. When diet CP content increased, the average daily gain of lambs increased (P < 0.05) while the age at slaughter decreased (P = 0.01), but no effect was observed on feed efficiency (P > 0.10). Diet CP content had limited effect on lamb carcass traits. Higher fibre digestibility was observed at the early v. late fattening period (P < 0.001). The N intake and the urinary N excretion increased when diet CP content increased (P < 0.001) and when shifting from early to late fattening period (P < 0.001). Faecal N excretion (P = 0.14) and N balance (P > 0.10) were not affected by diet CP content. Nitrogen digestibility increased (P < 0.001) as the diet CP content increased and on average it was greater at late v. early fattening period (P = 0.02). The NUE decreased (P = 0.001) as the diet CP content increased and as the lamb became older (P < 0.001). However, the age-dependent fall in NUE observed was lower at high v. low dietary CP content (CP × age interaction; P = 0.04). The Δ¹⁵N_animal-diet was positively correlated (P < 0.05) with N intake (r = 0.59), excretion of faecal N (r = 0.41), urinary N (r = 0.69) and total manure N (r = 0.64), while negatively correlated with NUE (r = −0.57). Overall, the experiment showed NUE was lower in older lambs and when lambs were fed high diet CP content, and that Δ¹⁵N_animal-diet was a useful indicator not only for NUE but also for urinary N excretion, which is a major environmental pollution factor on farm.     

Evolution of viscera and muscle fractional protein synthesis rate in lean meat selected hybrids and castrated Duroc pigs fed under moderate crude protein restriction

Differences in producing performance and organoleptic meat characteristics among pig genotypes and/or producing types are widely known. These parameters are also subjected to the animal’s development, feeding and management. Detailed knowledge of the effects of production phase (PP), pig producing type (PT), dietary protein availability and their interactions on nutrient digestibility, nitrogen balance and protein metabolism is essential information to improve precision feeding techniques. The experiment was a 2 (PP) × 2 (PT) × 2 (diet) factorial design conducted with 32 male pigs, 16 entire F2 pigs progeny of Pietrain sires and Duroc × Landrace dams, and 16 castrated purebred Durocs belonging to two production phases (growing: 29.5 ± 3.19 v. fattening: 88.6 ± 6.26 kg BW), and assigned to one of two dietary CP levels, either standard (SP: 17% in growing and 15% in fattening) or low (LP: 15% in growing and 13% in fattening). Viscera and muscle fractional protein synthesis rates (FSRs; %/day) were conducted through a single infusion of 15% L-[ring-²H₅]-phenylalanine, with subsequent blood sampling from 12 to 40 min, and sample collection of liver, duodenum, biceps femoris and longissimus dorsi skeletal muscles after sacrifice. Fattening animals acquired a greater feed ingestion capacity, average daily gain (P < 0.01) and apparent ileal digestibility, whereas growing pigs showed higher FSRs in both viscera (duodenum and liver) and in longissimus dorsi. F2 pigs showed higher average daily gain, nitrogen retention rates and FSR in liver and longissimus dorsi (P < 0.01). Nevertheless, apparent ileal digestibility in all essential amino acids was lower in F2 compared with Duroc pigs (P < 0.05). Protein metabolism was barely influenced by dietary CP content, although animals fed LP registered the lowest apparent ileal digestibility for CP and also for most of the essential amino acids compared with SP-fed pigs. This information may reveal differences in amino acid requirements between both PTs, with Duroc pigs receiving excess of dietary amino acids.     

Nutritional value of whole date waste and evaluating its application in ostrich diets

Although date waste products have been used as an alternative feed source in the diets of poultry for a long time, there is no quantitative information available regarding date waste used in ostrich diets. Therefore, two experiments were performed to evaluate the feeding value of whole date waste (WDW) as a feed ingredient in ostrich diets. In the first experiment, apparent metabolizable energy corrected to zero nitrogen balance (AMEn) of WDW was determined using 12 young ostriches (6 months old). The treatments included a reference diet and a test diet consisting of 60% of the reference diet and 40% of WDW. The AMEn of the WDW determined by total collection was 3 216 kcal/kg. In the second study, four groups of eight growing ostriches (seven month old), with almost similar BW (60.4 ± 1.6 kg), were individually housed in outdoor paddocks of ≈ 24 m² and were tested from 7 to 9 months of age. The groups were fed four isocaloric (2 420 kcal of AMEn/kg) and isonitrogenous (16.4% CP) diets containing 0, 10, 20, and 30% WDW. The results demonstrated that there were no significant differences among treatments in average daily feed intake, average daily gain, feed conversion ratio, and apparent total tract digestibility coefficients of DM, organic matter, energy, ether extract, ash, nitrogen-free extract, calcium, and phosphorus. In contrast, birds fed 0, 10, and 20% WDW diets had similar CP digestibility and this was significantly (P < 0.001) higher than that of birds on 30% WDW diet. The least crude fibre digestibility (P = 0.003) was also observed in birds fed 30% WDW diet. Blood RBC count, lymphocyte percentage, glucose concentration, and glutathione peroxidase activity increased linearly (P < 0.01), whereas heterophil percentage and heterophil-to-lymphocyte ratio decreased linearly (P = 0.002), in response to dietary inclusion of WDW. It can be concluded that WDW can be incorporated into the diets of ostrich chicks at levels of up to 30% without compromising growth performance. These results also suggest that WDW could be used as a feed ingredient for growing ostriches to improve stress-related variables and antioxidant status.     

Effects of feed form and energy levels on growth performance,carcass yield and nutrient digestibility in broilers

Feed form is well recognized to improve broiler performance, specially by increasing feed intake (FI). However, when different diet energy levels are used, the results differ in the literature. Therefore, this experiment was conducted to evaluate the influence of feed form and dietary metabolizable energy (ME) levels on broiler performance, carcass yield and on the digestibility of DM, CP, starch and gross energy. In total, 1152 male Cobb 500 broilers were evaluated between 35 and 47 days. The birds were distributed according to a completely randomized design in a 2 × 4 factorial arrangement, consisting of two feed forms (mash or pellet) and four ME levels (12.73, 13.06, 13.40 or 13.73 MJ/kg), totaling eight treatments with eight replicates of 18 birds. Broilers fed the lowest ME level presented the lowest weight gain (WG) and worst feed per unit gain (P < 0.01). Metabolizable energy intake increased (P < 0.01) with progressive increments of ME, which, however, did not affect caloric conversion (CC, P > 0.05). Pelleted diets promoted higher FI, WG, ME intake (P < 0.01) and better feed per unit gain and CC (P < 0.05) compared with mash. In mash diets, increasing dietary ME levels promoted a linear increase in WG (P < 0.01) and reduced feed per unit gain (P ≤ 0.05), but did not affect FI (P > 0.05). In pelleted diets, on the other hand, increasing ME levels linearly reduced FI (P < 0.05) and feed per unit gain (P < 0.01). Broilers fed pelleted diets presented higher abdominal fat deposition than those fed mash (P < 0.05). Increasing ME levels reduced the coefficients of ileal apparent digestibility of DM (P < 0.01) and total starch (P < 0.05) but did not affect the digestibility of other evaluated nutrients. The digestibility of all nutrients was lower when pelleted diets were fed compared with mash. Increasing inert material inclusion in the diets at the expense of soybean oil to reduce dietary ME levels promoted higher pellet durability index values (P < 0.05) and the percentage of fines (P < 0.01). Overall, the results suggest that pelleted diets promote better broiler performance because they increase FI, since the digestibility of dietary fractions is reduced. Chickens consuming low-energy pelleted diets may increase FI to compensate for energy deficit. In contrast, broilers fed mash diets may have reached their maximum intake capacity and did not regulate FI by changing feed energy density. When feeding pelleted diets, dietary energy reduction should be considered to reduce feed costs and to improve the carcass quality of broilers.     

Increased dietary protein for lactating sows affects body composition,blood metabolites and milk production

Hyper-prolific sows nurse more piglets than less productive sows, putting a high demand on the nutrient supply for milk production. In addition, the high production level can increase mobilization from body tissues. The effect of increased dietary protein (104, 113, 121, 129, 139 and 150 g standardized ileal digestible (SID) CP/kg) on sow body composition, milk production and plasma metabolite concentrations was investigated from litter standardization (day 2) until weaning (day 24). Sow body composition was determined using the deuterium oxide dilution technique on days 3 and 24 postpartum. Blood samples were collected weekly, and milk samples were obtained on days 3, 10 and 17 of lactation. Litter average daily gain (ADG) peaked at 135 g SID CP/kg (P < 0.001). Sow BW and back fat loss reached a breakpoint at 143 and 127 g SID CP/kg (P < 0.001). Milk fat increased linearly with increasing dietary SID CP (P < 0.05), and milk lactose decreased until a breakpoint at 124 g SID CP/kg and 5.3% (P < 0.001) on day 17. The concentration of milk protein on day 17 increased until a breakpoint at 136 g SID CP/kg (5.0%; P < 0.001). The loss of body protein from day 3 until weaning decreased with increased dietary SID CP until it reached a breakpoint at 128 g SID CP/kg (P < 0.001). The body ash loss declined linearly with increasing dietary SID CP (P < 0.01), and the change in body fat was unaffected by dietary treatment (P=0.41). In early lactation (day 3 + day 10), plasma urea N (PUN) increased linearly after the breakpoint at 139 g SID CP/kg at a concentration of 3.8 mmol/l, and in late lactation (day 17 + day 24), PUN increased linearly after a breakpoint at 133 g SID CP/kg (P < 0.001) at a concentration of 4.5 mmol/l. In conclusion, the SID CP requirement for sows was estimated to 135 g/kg based on litter ADG, and this was supported by the breakpoints of other response variables within the interval 124 to 143 g/kg.     

Common vetch varietal differences in hay nutritive value,ruminal fermentation,nutrient digestibility and performance of fattening lambs

In some lower rainfall regions of the world (300–750 mm), common vetch (Vicia sativa L., hereafter referred to as vetch) has been shown to have yields competitive with alternate crops and provide high-quality hay for ruminant diets, but there are few studies of vetch performance as a livestock feed, or of vetch varietal differences in livestock feeding value. This study evaluated vetch varietal differences in hay nutritive value, ruminal fermentation properties, nutrient digestibility, nitrogen retention and animal performance in fattening lambs consuming a diet comprising 20% vetch. Fifty male Hu lambs with an initial BW of 17.7 ± 0.27 kg and 2–3 months of age were assigned randomly into five groups of 10 lambs, and each allocated one of five dietary treatments for 67 days (10 days of adaptation and a 57 day experimental period). All diets contained 30% maize stover, 50% concentrate, and with a different forage source (on an as-fed basis): 20% alfalfa hay (Control), 20% vetch 333A (C333A) hay, 20% vetch Lanjian No. 1 (CLJ1) hay, 20% vetch Lanjian No. 2 (CLJ2) hay, or 20% vetch Lanjian No. 3 (CLJ3) hay. Hay CLJ3 had greater contents of ash, CP, ether extract, in vitro organic matter digestibility and metabolizable energy, and lower cell wall contents (P < 0.05) than those of C333A and CLJ1 hays, but similar to the CLJ2 hay (P > 0.05). Compared to the Control diet, the CLJ2 and CLJ3 diets resulted in greater (P < 0.05) final BW, average daily gain, total tract apparent digestibility of CP and NDF, and nitrogen balance, both when expressed as g/day and relative to nitrogen intake, while animal performance when fed diets with C333A or CLJ1 diet did not differ (P > 0.05) from the Control diet. No differences (P > 0.05) were observed between dietary treatments with respect to average daily feed intake, ruminal pH, total volatile fatty acid contents and molar proportions of acetate, butyrate, valerate, isobutyrate, and isovalerate, or total tract apparent digestibility of DM, organic matter, and ADF. The feed efficiency of tested feeds ranked CLJ3 = CLJ2 > CLJ1 > Control with C333A intermediate between CLJ1 and Control. In summary, considering hay quality, nutrient digestibility and animal weight gain, performance as a ruminant feed of hays from recently released vetch cultivars Lanjian No. 2 and Lanjian No. 3 was superior to the older cultivar C333A and the alfalfa control.     

Replacing soybean meal with flax seed meal: effects on nutrient digestibility,rumen microbial protein synthesis and growth performance in sheep

Flax seed meal (FSM) is rich in various nutrients, especially CP and energy, and can be used as animal protein feed. In animal husbandry production, it is a long-term goal to replace soybean meal (SBM) in animal feed with other plant protein feed. However, studies on the effects of replacing SBM with FSM in fattening sheep are limited. The aim of this experiment was to study the effects of replacing a portion of SBM with FSM on nutrient digestibility, rumen microbial protein synthesis and growth performance in sheep. Thirty-six Dorper × Small Thin-Tailed crossbred rams (BW = 40.4 ± 1.73 kg, mean ± SD) were randomly assigned into four groups. The dietary treatments (forage/concentrate, 45 : 55) were isocaloric according to the nutrient requirements of rams. Soybean meal was replaced with FSM at different levels (DM basis): (1) 18% SBM (18SBM), (2) 12% SBM and 6% FSM (6FSM), (3) 6% SBM and 12% FSM (12FSM) and (4) 18% FSM (18FSM). The rams were fed in individual pens for 60 days, with the first 10 days for adaptation to diets, and then the digestibility of nutrients was determined. There was no significant difference in DM intake, but quadratic (P < 0.001) effects on the average daily gain and feed efficiency were detected, with the highest values in the 6FSM and 12FSM groups. For DM and NDF digestibility, quadratic effects were observed with the higher values in the 6FSM and 12FSM groups, but the digestibility of CP linearly decreased with the increase in FSM in the diet (P = 0.043). There was a quadratic (P < 0.001) effect of FSM inclusion rate on the estimated microbial CP yield. However, the values of intestinally absorbable dietary protein decreased linearly (P < 0.001). For the supply of metabolisable protein, both the linear (P = 0.001) and quadratic (P = 0.044) effects were observed with the lowest value in the 18FSM group. Overall, the results indicated that SBM can be effectively replaced by FSM in the diets of fattening sheep and the optimal proportion was 12.0% under the conditions of this experiment.     

The effect of CP concentration in the diet on urea kinetics and microbial usage of recycled urea in cattle: a meta-analysis

In ruminants, urea recycling is considered an evolutionary advantage. The amount of urea recycled mainly depends of the nitrogen (N) intake and the amount of organic matter (OM) digested in the rumen. Because recycled N contributes to meeting microbial N requirements, accurate estimates of urea recycling can improve the understanding of efficiency of N utilization and N losses to the environment. The objective of this study was to evaluate urea kinetics and microbial usage of recycled urea N in ruminants using a meta-analytical approach. Treatment mean values were compiled from 25 studies with ruminants (beef cattle, dairy cows and sheep) which were published from 2001 to 2016, totalling 107 treatment means. The data set was analyzed according to meta-analysis techniques using linear or non-linear mixed models, taking into account the random variations among experiments. Urea N synthesized in the liver (UER) and urea N recycled to the gut (GER) linearly increased (P<0.001) as N intake (g/BW^0.75) increased, with increases corresponding to 71.5% and 35.2% of N intake, respectively. The UER was positively associated (P<0.05) with dietary CP concentration and the ratio of CP to digestible OM (CP:DOM). Maximum curvature analyses identified 17% dietary CP as the point where there was a prominent increase in hepatic synthesis of urea N, likely due to an excess of dietary N leading to greater ammonia absorption. The GER:UER decreased with increasing dietary CP concentration (P<0.05). At dietary CP⩾19%, GER:UER reached near minimal values. The fraction of UER eliminated as urinary urea N and the contribution of urea N to total urinary N were positively associated with dietary CP (P<0.05), both reaching values near the plateau when dietary CP was 17%. The fractions of GER excreted in the feces and utilized for anabolism decreased, whereas the fraction of GER returned to the ornithine cycle increased with dietary CP concentration (P<0.05). Recycled urea N assimilated by ruminal microbes (as a fraction of GER) decreased as dietary CP and CP:DOM increased (P<0.05). The efficiency of microbial assimilation of recycled urea N was near plateau values at 194 g CP/kg DOM. The models obtained in this study contribute to the knowledge on N utilization, and they could be used in feeding models to predict urea recycling and thus to improve formulation of diets to reduce N losses that contribute to air and water pollution.     

Standardized ileal digestibility of amino acids in eight genotypes of barley fed to growing pigs

To determine chemical composition, physical characteristics and standardized ileal digestibility (SID) of CP and amino acids (AA) in eight current hulled barley genotypes, an experiment with growing pigs has been conducted. These genotypes included Yool, Campanile, Lomerit, Travira, Anisette, Canberra, Metaxa and Fridericus. Growing barrows with an average initial BW of 30±2 kg were surgically fitted with simple T-cannulas at the distal ileum, and allotted to an 8×9 Youden square design with eight periods of 6 days each and nine pigs. Barley was the sole dietary source of CP and AA. On average, the eight genotypes contained on as-fed basis 10.7% CP, 15.2% total non-starch polysaccharides (NSP), 17.1% NDF and 4.1% β-glucan, and had a mean test weight (TW) of 72.2 kg/hl. The SID of CP in the barley genotypes varied from 69% to 74%, and was greater (P<0.01) for genotypes Travira, Anisette and Metaxa compared to Yool and Campanile. Standardized ileal digestibility of Lys, Met and Trp (P<0.05) but not of Thr differed between genotypes. Moreover, barley genotypes differed in their standardized ileal digestible content (cSID) of CP and AA. Furthermore, SID and cSID of CP and most AA linearly decreased (P<0.05) with increasing NDF and total sugar content. Standardized ileal digestibility of CP and some AA and cSID of CP and most AA decreased linearly with increasing TW (P<0.05). Additionally, SID and cSID of CP and AA of most barley genotypes were lower when compared to tabulated values. In conclusion, a comprehensive database on chemical composition and SID of CP and AA in eight current barley genotypes has been made available. However, as present SID values are lower compared to feed tables, adjustments are required to minimize the risk of overestimating the actual protein value of barley for pigs.     

Influence of dietary fibre on nutrient digestibility and energy utilisation in growing pigs fed diets varying in soluble and insoluble fibres from co-products

The co-products from the industry are used to reduce costs in pig diets. However, the co-products used in pig diets are limited because of a high fibre content which is not digested by endogenous enzymes and is resistant to degradation in the small and large intestines. The aim of this study was to investigate digestibility of nutrients and energy, and energy utilisation in pigs fed diets with various soluble and insoluble dietary fibre (DF) from co-products. The experiment was performed as a 4 × 4 Latin square design (four diets and four periods) using four growing pigs (66.2 ± 7.8 kg) surgically fitted with a T-cannula in the end of the small intestine. The pigs were fed four experimental diets: low-fibre control (LF), high-fibre control (HF), high-soluble fibre (HFS) and high-insoluble fibre (HFI) diets. The apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of ash, organic matter, CP, fat, carbohydrates, starch and non-starch polysaccharides (NSP) divided into cellulose and soluble and insoluble non-cellulosic polysaccharide residues were measured using chromic oxide as marker. The recovery of total solid materials, organic matter and total carbohydrates in ileal digesta in pigs fed the HF and HFS diets was higher than in pigs fed LF and HFI, whereas recovery of organic matter and total carbohydrates in faecal materials in the HFS diet was lowest (P < 0.05). AID of organic matter, total carbohydrates and starch was lowest for HFS diet (P < 0.05). ATTD of organic matter and CP was higher for LF diet compared with other diets (P < 0.05), whereas total NSP, cellulose and non-cellulosic polysaccharides residues were highest for HFS diet (P < 0.05). Lactic acid in ileal digesta was influenced by dietary composition (P < 0.05) whereas neither type nor level of DF affected short chain fatty acids. The digestible energy, metabolisable energy, net energy and retained energy intake were similar among diets without influence of DF inclusion (P > 0.05). The metabolisable energy:digestible energy ratio was lower when feeding the HFS diet because of a higher fermentative methane loss. Faecal nitrogen and carbon were positively correlated with DM intake and insoluble DF in the diets (P < 0.05), but nitrogen and carbon (% of intake) were similar among diets. The present findings suggest that high-DF co-products can be used as ingredients of pig diets when features of DF are considered.     

Effects of supplementing a CP-reduced diet with rumen-protected methionine on Fleckvieh bull fattening

The objective of this study was to evaluate the effect of supplementing a CP-reduced diet with rumen-protected methionine on growth performance of Fleckvieh bulls. A total of 69 bulls (367 ± 25 kg BW) were assigned to three feeding groups (n = 23 per group). The control (CON) diet contained 13.7% CP and 2.11 g methionine/kg diet (both DM basis) and was set as positive control. The diet reduced in CP (nitrogen) (RED) diet as negative control and the experimental RED + rumen-protected methionine (MET) diet were characterised by deficient CP concentrations (both 9.04% CP). The RED + MET diet differed from the RED diet in methionine concentration (2.54 g/kg DM vs. 1.56 g/kg DM, respectively) due to supplementation of rumen-protected methionine. Rumen-protected lysine was added to both RED and RED + MET at 2.7 g/kg DM to ensure a sufficient lysine supply relative to total and metabolisable protein intake. Metabolisable energy (ME) and nutrient composition were similar for CON, RED, and RED + MET. Bulls were fed for 105 days (d) on average. Individual feed intake was recorded daily; individual BW was recorded at the beginning of the experiment, once per month, and directly before slaughter. At slaughter, blood samples were collected and carcass traits were assessed. Reduction in dietary CP concentration reduced feed intake, and in combination with lower dietary CP concentration, daily intake of CP for RED and RED + MET was lower compared with CON (P < 0.01). Daily ME intake was reduced in RED and RED + MET compared with CON (P < 0.01). Consequently growth performance and carcass weights were reduced (both P < 0.01) in both RED and RED + MET compared with CON. Supplemental rumen-protected methionine was reflected in increased serum methionine concentration in RED + MET (P < 0.05) as compared to RED but it did not affect growth performance, carcass traits and serum amino acid (AA) concentrations, except for lysine which was reduced (P < 0.01) compared to CON and RED. In conclusion, bulls fed RED or RED + MET diets were exposed to a ruminal CP deficit and subsequently a deficit of prececal digestible protein, but methionine did not appear to be the first-limiting essential AA for growth under the respective experimental conditions.     

Evaluation of protein supplementation for growing cattle fed grass silage-based diets: a meta-analysis

The objective of this meta-analysis was to develop empirical equations predicting growth responses of growing cattle to protein intake. Overall, the data set comprised 199 diets in 80 studies. The diets were mainly based on grass silage or grass silage partly or completely replaced by whole-crop silages or straw. The concentrate feeds consisted of cereal grains, fibrous by-products and protein supplements. The analyses were conducted both comprehensively for all studies and also separately for studies in which soybean meal (SBM; n=71 diets/28 studies), fish meal (FM; 27/12) and rapeseed meal (RSM; 74/35) were used as a protein supplement. Increasing dietary CP concentration increased (P<0.01) BW gain (BWG), but the responses were quantitatively small (1.4 g per 1 g/kg dry matter (DM) increase in dietary CP concentration). The BWG responses were not different for bulls v. steers and heifers (1.4 v. 1.3 g per 1 g/kg DM increase in dietary CP concentration) and for dairy v. beef breeds (1.2 v. 1.7 g per 1 g/kg, respectively). The effect of increased CP concentration declined (P<0.01) with increasing mean BW of the animals and with improved BWG of the control animals (the lowest CP diet in each study). The BWG responses to protein supplementation were not related to the CP concentration in the control diet. The BWG responses increased (P<0.05) with increased ammonia N concentration in silage N and declined marginally (P>0.10) with increasing proportion of concentrate in the diet. All protein supplements had a significant effect on BWG, but the effects were greater for RSM (P<0.01) and FM (P<0.05) than for SBM. Increasing dietary CP concentration improved (P<0.01) feed efficiency when expressed as BWG/kg DM intake, but decreased markedly when expressed as BWG/kg CP intake. Assuming CP concentration of 170 g/kg BW marginal efficiency of the utilisation of incremental CP intake was only 0.05. Increasing dietary CP concentration had no effects on carcass weight, dressing proportion or conformation score, but it increased (P<0.01) fat score. Owing to limited production responses, higher prices of protein supplements compared with cereal grains and possible increases the N and P emissions, there is generally no benefit from using protein supplementation for growing cattle fed grass silage-based diets, provided that the supply of rumen-degradable protein is not limiting digestion in the rumen.     

Effect of decreasing dietary crude protein in fattening calves on the emission of ammonia and greenhouse gases from manure stored under aerobic and anaerobic conditions

Dietary strategies can potentially help to reduce nitrogen (N) emissions and decrease the environmental impact of beef production. This study aimed to evaluate the effects of dietary crude protein (CP) concentration on animal performance, N excretion, and manure N volatilisation of finishing Holstein animals. In a first study, 105 Holstein bulls (BW 344 ± 2.6 kg; age 252 ± 0.9 days) were allocated to eight pens to evaluate the effect of two treatments (medium (M) and low (L), which contained CP 14.5% and 12% on a DM basis, respectively) on performance, and results confirmed that dietary CP decrease did not impair animal growth. In a second study, N excretion study, 24 Holstein heifers (BW 310 ± 5.3 kg; age 251 ± 1.4 days) were distributed randomly depending on the initial BW to three treatments (high (H), M, and L, which contained CP 17%, 14.5% and 12% on a DM basis, respectively). Based on N excretion, urinary N excretion was greater (P < 0.001) in H than in M and L diets, but no differences in faecal N excretion were observed among treatments. A third study with in vitro assays under aerobic and anaerobic conditions was designed to analyse gaseous emissions (volatilisation of N and carbon, C) during the storage stage of manure. Manure, faecal and urine samples, mixed at a ratio of 1:1 (wet weight), were collected during the N excretion study (manure-H, manure-M, manure-L). Under aerobic conditions, manure-M and manure-L showed a delay of 4–5 days in manure ammonia emission compared with manure-H (P < 0.01). Total N content was lower (P < 0.01) in manure-L compared with manure-M and manure-H, but N volatilisation (percentage relative to initial N) in manure-L and manure-M was greater (P < 0.01) than in manure-H. In contrast, the anaerobic N volatilisation was 20 times greater in manure-M and 10 times greater in manure-H compared with manure-L. Under aerobic and anaerobic conditions, the emission of C, as C-CO₂ and C-CH₄, was greater in manure-L than in manure-H and manure-M. Therefore, the decrease of dietary CP concentration from 17% to 14.5% and 12% is an efficient strategy to reduce urinary N excretion by 40%, without impairing performance, and also to reduce manure N losses through ammonia volatilisation under anaerobic conditions. However, a dietary CP content of 14.5% resulted in less environmental impact than a CP content of 12.8% when also considering manure emissions under aerobic or anaerobic conditions.     

Carbohydrases and phytase with rice bran,effects on amino acid digestibility and energy use in broiler chickens

Protein sources from cereals are used in broiler diets, usually in order to reduce feeding costs. However, their efficient use in poultry diets is limited by the level of fiber whose compounds are resistant to digestion in the small intestine; due to this sugars are not digested by endogenous poultry enzymes. The aim of this study was to determine the effect of multi-carbohydrase (MC) and phytase (Phy) on the total retention of nutrients, retention of apparent metabolizable energy corrected for nitrogen (AME_N) (trial 1) and apparent and standardized ileal digestibility of amino acids (trial 2) of rice bran (RB). A total of 245-day-old male broilers (Cobb 500) was distributed at 21-day-old in a completely randomized design in a 2 × 2 + 1 (0 and 200 mg/kg MC; 0 and 50 mg/kg Phy, and basal diet – BD) factorial arrangement of treatments, to give seven replicates and seven birds per replicate. The BD based on corn (trial 1) and cornstarch and casein (trial 2) was used only to determine the coefficients of retention of nutrients and energy, and coefficients of digestibility of amino acids of the RB. The test diets were made by mixing BD and RB 7 : 3 wt/wt basis. There was interaction (P<0.05) between MC × Phy for DM, nitrogen and AMEN, retention and no interaction (P>0.05) for ash, calcium, phosphorous and NDF was observed. Enzymes interacted (P<0.05) on standardized ileal digestibility of arginine, histidine, leucine, methionine, phenylalanine, threonine, valine, aspartic acid, glutamic acid, proline and serine. Dietary combination of MC and Phy resulted in higher (P<0.05) standardized digestibility of arginine, histidine, methionine and threonine relative to single enzyme supplementation or control diet without enzymes. Enzyme isolated inclusions in the diets improved (P<0.05) standardized digestibility of methionine. The supplementation of carbohydrases and Phy in RB will improve the nitrogen, energy and amino acids utilization for broiler chickens.     

Relationship between the amino acid release kinetics of feed proteins and nitrogen balance in finishing pigs

In current nutrition requirements of swine, although the protein diets are formulated based on the ileal digestibility of protein and amino acid (AA), there is a difference in nitrogen utilisation among various protein diets, which might be related to the AA release kinetics. To evaluate the relationship between AA release kinetics of feed proteins and nitrogen balance in finishing pigs, pigs were fed diets based on casein (CAS) or corn gluten meal (CGM) at normal or low-protein concentrations, and the AA release patterns were assessed. A 2 × 2 full factorial experimental design was used. 24 pigs (Duroc × Landrace × Yorkshire) with an initial weight of 67.0 ± 1.8 kg were randomly assigned to consume a normal-protein casein-based diet (N.CAS, 10% CP), normal-protein corn gluten meal-based diet (N.CGM, 10% CP), low-protein casein-based diet (L.CAS, 8.5% CP), or low-protein corn gluten meal-based diet (L.CGM, 8.5% CP) for 14 days (n = 6 per group; pigs housed and fed separately). The low-protein diets were associated with a more rapid release of AAs in the early stages of gastric digestion than the normal-protein diets. The N.CAS and L.CAS diets were associated with a peak AA release at approximately 4 h during trypsin digestion, whereas N.CGM and L.CGM were at approximately 16 h. The N.CAS diet was associated with the least dispersed release curves and lowest synchronisation indexes, implying that it was associated with the best AA release synchronism, whereas the L.CGM diet was on the contrary. The nitrogen intake (NI), faecal nitrogen, urine nitrogen (UN), total nitrogen, net protein utilisation and apparent biological value (ABV) of protein of pigs fed the L.CAS or L.CGM diets were lower than those fed the N.CAS or N.CGM diets (P < 0.05). Notably, there was a difference in NI (P < 0.05) and trends with respect to UN and ABV (0.05 < P < 0.1), but no differences in retained nitrogen or apparent nitrogen digestibility between pigs fed the N.CAS or L.CAS diets and those fed the N.CGM or L.CGM diets. Pigs fed the N.CAS or N.CGM diets had higher serum concentrations of UN than pigs fed the L.CAS or L.CGM diets (P < 0.05), but there were no differences in serum total protein, albumin, triglyceride, glucose, alanine transaminase, or aspartate aminotransferase between the groups. In addition, there was an interaction between protein level and protein source on serum globulin (P < 0.05). Therefore, the diet with a better AA release synchronism can improve protein utilisation efficiency in finishing pigs and to reduce environmental pollution.     

Rubber seed oil and flaxseed oil supplementation alter digestion,ruminal fermentation and rumen fatty acid profile of dairy cows

Rubber seed oil (RO) that is rich in polyunsaturated fatty acids (FA) can improve milk production and milk FA profiles of dairy cows; however, the responses of digestion and ruminal fermentation to RO supplementation in vivo are still unknown. This experiment was conducted to investigate the effect of RO and flaxseed oil (FO) supplementation on nutrients digestibility, rumen fermentation parameters and rumen FA profile of dairy cows. Forty-eight mid-lactation Holstein dairy cows were randomly assigned to one of four treatments for 8 weeks, including basal diet (CON) or the basal dietary supplemented with 4% RO, 4% FO or 2% RO plus 2% FO on a DM basis. Compared with CON, dietary oil supplementation improved the total tract apparent digestibility of DM, neutral detergent fibre and ether extracts ( P < 0.05). Oil treatment groups had no effects on ruminal digesta pH value, ammonia N and microbial crude protein ( P > 0.05), whereas oil groups significantly changed the volatile fatty acid (VFA) profile by increasing the proportion of propionate whilst decreasing total VFA concentration, the proportion of acetate and the ratio of acetate to propionate ( P < 0.05). However, there were no differences in VFA proportions between the three oil groups (P > 0.05). In addition, dietary oil supplementation increased the total unsaturated FA proportion in the rumen by enhancing the proportion of trans-11 C18:1 vaccenic acid (VA), cis-9, trans-11 conjugated linoleic acid (CLA) and α-linolenic acid (ALA) ( P < 0.05). These results indicate that dietary supplementation with RO and FO could improve nutrients digestibility, ruminal fermentation and ruminal FA profile by enhancing the VA, cis-9, trans-11 CLA and ALA composition of lactating dairy cows. These findings provide a theoretical basis for the application of RO in livestock production.     

Digestibility and utilisation of diets composed of wet distillers' solids or soyabean meal and supplemented with liquid lysine product for growing pigs

A digestibility and balance trial was carried out to study the nutrient digestibility and utilisation of protein and energy in wet distillers' solids derived from barley or soyabean meal. Eight growing pigs (30–72 kg liveweight) were used in an 8 × 6 cyclic change-over experimental design, in which eight experimental diets were arranged 2 × 2 × 2 factorially. The corresponding factors were the protein source (wet distillers' solids (DS) or soyabean meal (SBM)), protein supply (130 or 162 g crude protein (CP) kg⁻¹ dry matter (DM)) and liquid lysine product supplementation.DS and SBM contained 565 g and 485 g CP kg⁻¹ DM, respectively, and the respective lysine contents in CP were 39 g and 64 g per 160 g N. The liquid lysine product contained 527 g CP kg⁻¹ DM and lysine in CP 193 g per 160 g N.No differences were found in the total tract digestibility of the nutrients or energy among diets composed of DS or SBM without lysine supplementation. Those diets with liquid lysine product supplementation, however, had opposite effects on the digestibility of the diets composed of the different protein sources. Lysine supplementation improved the digestibility of ash (P < 0.001), ether extract (P < 0.05) and crude carbohydrates (CCH) (P < 0.05) in diets composed of DS and adversely impaired the digestibility of organic matter and CCH (P < 0.05) in diets composed of SBM. The calculated digestibility of CP and gross energy were respectively 91.2% and 88.3% in SBM and 90.2% and 85.0% in DS. The digestible and calculated net energy contents were respectively 18.16 MJ kg⁻¹ DM and 10.73 MJ kg⁻¹ DM for SBM and 19.31 MJ kg⁻¹ DM and 10.40 MJ kg⁻¹ DM for DS.The pigs on the diets composed of DS had higher total (P < 0.001) and urea (P < 0.01) nitrogen (N) excretion in urine and lower daily retention of N (P < 0.001) than the pigs on the diets composed of SBM. The liquid lysine product supplementation of the diets decreased the total and urea N excretion in urine (P < 0.001) and improved the daily N retention (P < 0.001). With lysine supplementation, the protein utilisation of the diets composed of DS was improved to the level of the diets composed of SBM. No differences were observed in the utilisation of energy among the diets composed of different protein sources.It is concluded that DS is highly digestible, but its protein is efficiently utilised only with lysine supplementation.     

Cashew nut meal as feed supplement for lambs

Cashew nut meal (CNM) is widely used in tropical countries due to the high protein and energy levels; therefore, it has potential to be an alternative feed supplementation for livestock. Our objective was to evaluate the use of CNM as feed supplement for lambs. Twenty-four lambs were divided into a randomized block design with four treatments, starting with a diet control of Tifton 85 (Cynodon spp.) hay and CNM as a supplement at three different levels representing 6, 12, and 18% of the total mixed ration (TMR) provided. There were evaluated intake (g/day and g/kgBW^0.75); the digestibility of DM and nutrients; nitrogen balance; and ingestive behavior. The CP and ether extract (EE) intake (g/day) as well as DM, and organic matter (OM) intake (g/kgBW^0.75) were influenced by supplementation with CNM in a positive linear increase (P < 0.05). The digestibility of DM, OM and NDF increased according to the levels of CNM up to 12% and markedly decreased at the higher level (P < 0.05). The EE and CP digestibility raised according to the CNM levels (P < 0.05) and consequently increased the nitrogen retention resulting in a positive nitrogen balance. The protein and energetic characteristics of CNM show that it can be used as an alternative supplementation to low-quality forages for lambs. However, its use as a single supplement ingredient above 7% on total mixed ration may reduce fiber digestibility.