Dietary CP Research Articles

Nitrogen balance in dairy cows fed low-nitrogen diets based on various proportions of fresh grass and maize silage.

To ensure sustainable and efficient production, dairy farms must reduce their environmental impacts and nitrogen losses, which are sources of pollution, while increasing their feed self-sufficiency. Grass-based dairy systems, frequently combine fresh grass with maize silage when grass is scarce or during dietary transitions. However, the effects of combining fresh grass and maize silage on cow performance and N excretion are poorly known. This study aimed to quantify the effects of increasing the proportion of maize silage in a fresh grass diet on cow N flows and metabolism, in the context of grass-based dairy systems. Four proportions of maize silage in a fresh grass diet (objectives of 0, 17, 34 and 51% DM of maize silage) were investigated. The experiment was performed in a 4×3 Latin square design using eight lactating cows during three 3-week periods. DM intake (DMI), milk yield, faeces and urine outputs, and their N concentrations were measured for each cow. The fresh grass CP concentration was lower than planned (106±13.0g/kg DM). This resulted in very low dietary CP concentration, which decreased from 108 to 86g/kg DM when maize silage in the diet increased from 0 to 51% DM, respectively. DM intake and milk yield both decreased linearly by 3.3kg/day from 0 to 51% DM of maize silage in the diet. Thus, N intake decreased linearly by 100g/day from 0 to 51% DM of maize silage in the diet. The N concentration of milk was highest for the diet with 0% DM of maize silage. Nitrogen excreted in faeces and urine decreased linearly by 29 and 23g/day, respectively, from 0 to 51% DM of maize silage in the diet. The low dietary N concentration resulted in low ruminal NH3-N concentrations (8mg/L, on average) and urinary urea excretion (down to 8% urea N in urinary N). Increasing the proportion of maize silage in an unusually low-N grass diet, without protein-rich concentrates, induced highly N-deficient diets with minimal N losses in faeces and urine but large and unsustainable decreases in DMI and milk yield.

The influence of non-bound amino acid inclusions and starch-protein digestive dynamics on growth performance of broiler chickens offered wheat-based diets with two crude protein concentrations

The primary objective of this study was to investigate the influence of high and low inclusions of non-bound amino acid (NBAA) in standard and reduced-crude protein (CP), wheat-based diets on growth performance in broiler chickens. Dietary treatments were formulated to either 210 or 180 g/kg CP. The 210 g/kg CP diets contained either 12.1 or 21.1 g/kg NBAA and 180 g/kg CP diets contained either 44.0 or 55.5 g/kg NBAA. The formulations also generated different dietary starch:protein ratios which impacted on starch-protein digestive dynamics. Each of the four dietary treatments were offered to 7 replicates of 15 birds housed in floor pens from 14 to 35 days post-hatch or a total of 420 male Ross 308 chickens. Growth performance, relative abdominal fat-pad weights, breast muscle and leg shank yields were determined. Ileal starch and protein (N) digestibility coefficients, disappearance rates and starch:protein disappearance rate ratios were defined. Apparent ileal digestibility coefficients and disappearance rates of 16 amino acids were determined at 35 days post-hatch and free concentrations of 20 amino acids in systemic plasma were determined at 34 days post-hatch. The transition from 210 to 180 g/kg CP diets depressed weight gain by 11.3% (1742 versus 1964 g/bird) and FCR by 10.4% (1.606 versus 1.455), although both parameters were subject to treatment interactions. The treatment interaction (P < 0.001) observed for FCR was because high NBAA inclusions significantly improved FCR by 4.17% (1.424 versus 1.486) in birds offered 210 g/kg CP diets, but significantly depressed FCR by 3.36% (1.632 versus 1.579) in 180 g/kg CP diets. A quadratic relationship (r = 0.860; P < 0.001) between dietary NBAA inclusions and FCR was detected, which indicated that when NBAA inclusions exceed 18.5 g/kg efficiency of feed conversion deteriorated. However, a multiple linear regression (r = 0.913; P < 0.001) was detected for FCR where both NBAA inclusions and analysed dietary starch:protein ratios were significantly (P < 0.001) related to FCR. This relationship indicates that growth performance of broiler chickens offered wheat-based diets is strongly influenced by dietary NBAA inclusions coupled with dietary starch:protein ratios and consideration is given to the possible underlying mechanisms.

Effects of L-arginine, guanidinoacetic acid and L-citrulline supplementation in reduced-protein diets on bone morphology and mineralization of laying hens.

The alterations in feed ingredients and the nutrient matrix to produce reduced-protein diets may affect bone morphology and mineralization in laying hens. This study was implemented to determine the effects of L-arginine (Arg), guanidinoacetic acid (GAA), and L-citrulline (Cit) supplementation to Arg-deficient reduced-protein diets on bone morphology, strength, and mineralization status of laying hens. Individually housed Hy-Line Brown laying hens were evenly distributed to five dietary treatments with 25 replicates per treatment from 20 to 40wk of age. Treatments consisted of a standard protein diet (17% crude protein, SP), a reduced-protein diet deficient in Arg (13% crude protein, RP), and RP supplemented with Arg (0.35% Arg, RP-Arg), GAA (0.46% GAA equivalent to 0.35% Arg, RP-GAA), or Cit (0.35% Cit equivalent to 0.35% Arg, RP-Cit) to reach the Arg level of SP diets. Birds fed the SP diet had similar bone weight, ash, length, width, Seedor index, breaking strength, and serum mineral concentration, but higher toe B level (P<0.001) compared to those fed the RP diet at wk 40. Birds fed the SP diet consumed more but also excreted more K and B compared to those fed the RP diet (P<0.01). Birds fed the SP diet had lower Cu digestibility (P=0.01) and higher B retention (P<0.01) compared to those offered the RP diet. Supplementation of Arg, GAA, and Cit to the RP diet increased relative femur weight and length (P<0.001). Citrulline supplementation also increased relative tibia and femur ash, and Zn digestibility (P<0.05). Supplementation of GAA to the RP diet decreased serum Ca, P, and Mg levels, decreased tibia Fe and Mg levels and toe Mg level, but increased Al, Fe, Zn, and Mn digestibility (P<0.05). The current findings demonstrated the capacity of laying hens to adapt to low mineral intake by increasing mineral utilization. Overall, bone morphology and breaking strength, and serum mineral level in laying hens were not influenced by dietary CP levels. Dietary Arg, GAA, or Cit supplementation were effective in improving bone morphology and mineralization in laying hens fed Arg-deficient RP diets.

Nitrogen efficiency in cows fed red clover- or alfalfa-silage-based diets differing in rumen-degradable protein supply

Nitrogen pollution is an important issue in modern agriculture. For the dairy industry, increasing the efficiency of milk protein production may reduce the environmental impact of commercial farms. Optimal N utilization can be achieved by combining forage and concentrate varying in their degradability in the rumen. The aim of this study was to gain insight into the fate of dietary N as affected by forage type and rumen-degradable protein supply in lactating dairy cows, with an emphasis on milk N efficiency. Four rumen-fistulated Holstein cows were used in a 4 × 4 Latin square design balanced for residual effects. Four treatments consisting of a 2-by-2 factorial arrangement of alfalfa silage (AL) or red clover (RC)-based diets designed to satisfy 100 (rumen-degradable protein (RDP)-100) or 85% (RDP-85) of rumen degradable protein demand, by varying the amounts of ground and steam-flaked corn grain, as well as non-treated and heat-treated soybean meals. Dietary CP concentrations were greater in diets based on AL as compared with RC (P < 0.01). Kinetics of in sacco N disappearance revealed that the rapidly disappearing fraction was lower with RC than with AL diets, and this difference tended to be more pronounced for RDP-85 than RDP-100 (interaction, P = 0.06). On the contrary, slowly disappearing N fraction and fractional rate of disappearance were greater for RC as compared with AL diets (P < 0.01). Reducing RDP from 100 to 85% of requirements increased the slowly disappearing N fraction, but decreased the rapidly disappearing fraction and the fractional rate of disappearance of N (P < 0.01). Intakes of DM and N were lesser with RC compared with AL, and these differences were more pronounced with RDP-85 than with RDP-100 (interaction, P ≤ 0.04). As a proportion of N intake, fecal excretion tended to be greater (P = 0.09), whereas urinary excretion was lower (P = 0.04) with RC than with AL diets. Milk yield (tendency; P = 0.07) and total N secreted in milk were reduced (P < 0.01) with RC compared with AL diets. Feeding RC increased milk N efficiency (g of milk N/ kg of N intake) as compared with AL, and this difference tended to be of greater magnitude for RDP-85 than RDP-100 (interaction, P = 0.06). In conclusion, combining forage and concentrate of different CP degradability can improve milk N efficiency in dairy cows.

Efficacy of Best Prelay Diet on Production Performance of White Leghorn Layers Fed with Different Layer Diets

Background: Feeding high nutrient density best prelay diet (BPD) 2-3 weeks before egg production is beneficial and may allow to reduce layer diet nutrient density. Methods: Total 180, 16-week-old White Leghorn pullets were assigned to six-layer feeding strategies (kcal ME per kg/%CP/%Ca) during 19-40 weeks. Treatments were T0 (BIS control-2600/18.0/3.0), T1 (2500/18.0/3.0), T2 (2500/18.0/4.0), T3 (2500/17.0/4.0), T4 (2500/16.0/4.0) and T5 (2500/15.0/4.0). These layers were fed with same BPD (2700/18.0/2.5) during 16-18 weeks. Performance parameters were recorded during the study. Result: Feeding BPD did not influence pullets (16-18 woa) CaI, PI and MEI. The 3.0% layer Ca (T0 and T1) decreased (p less than 0.01) CaI than 4.0% (T2 to T5) and layer diet CP reduction from 18.0 to 15.0% decreased PI but 2500 or 2700 kcal ME/kg layer diet did not affect MEI (19-40 woa). BPD did not support 16 or15% layer diet CP (T4 and T5) but allowed to reduce CP (T3) by 1.0% (18.0 to 17.0%) to support production. BPD (2700/18.0/2.5) with BIS (2007) layer diet in T0 (2600/18.0/3.0) is the best combination for supporting BWG without affecting FC and improving EN, HDEP, FCDE, EFPR and PEI in layers.

The effect of oregano essential oil on Feed Passage Syndrome in broilers: 2. Assessment under a challenge model

Feed Passage Syndrome (FPS) in broilers is a multifactorial condition characterized by wet excreta and decreased feed efficiency, which can be triggered by various contributing factors. Alternatives to antimicrobials, including phytogenics, are being studied to control this process. This study assessed oregano essential oil (OEO) in broilers subjected to a FPS challenge model. Three treatments (negative control, neomycin-fed positive control, and OEO-fed group) were included. All treatments were challenged with reused litter, inoculums of Eimeria spp. and Clostridium perfringens, and excess dietary CP. OEO-fed birds showed improved performance, better excreta characteristics, lower frequency of congested mucosa, reverted hyperplasia of the bursa of Fabricius, better antioxidant status, and higher breast and carcass weights and dietary protein and energy efficiencies. The OEO treatment was shown to influence the growth pattern of the broilers. In conclusion, the OEO showed positive effects in broilers challenged with a FSP model.

Effect of dietary crude protein levels on feed intake and nutrient digestibility of Wagyu crossbred cattle

The objective of the experiment was to determine the suitable crude protein level on feed intake and digestible nutrient value of Wagyu crossbred cattle from 13 to 20 months of age. The research included 2 experiments. Experiment 1: five male Wagyu x Zebu crossbred cattle (12.2±0.56 months of age and average live weight of 179±24.2 kg, Mean±SD). Experiment 2: five male Wagyu x Zebu crossbred cattle (16.7±1.05 month’s old and live weight of 276±22.0 kg). Two experiments were Latin square design (5x5) with 5 treatments and 5 periods (21 days per period). The treatments were different crude protein levels at 210, 245, 280, 315, and 350 g per 100 kg live weight (LW) corresponding to CP210, CP245, CP280, CP315, and CP350 treatments, respectively. The basal diet was commercial concentrate (1.2 kg/day), fresh Elephant grass (5.0 kg/day) and ad libitum rice straw. While soybean meal was used to adjust the dietary CP level per 100 kg LW in diets. The result showed that increasing nutrient consumption and metabolism energy (P&lt;0.05) but reduced fiber intakes (P&gt;0.05) by increasing crude protein levels. Experiment 1: the CP digestibility was highest (P&lt;0.05) of CP350 (72.8%) treatment compare to CP210 (58.8%) treatments, while the CP280 (67.2%) treatment was not significant (P&gt;0.05) with CP245 (62.9%) and CP315 (71.7%) treatments. Experiment 2: the highest CP digestibility (P&lt;0.05) of CP350 treatment as compared to CP315, CP280, CP245, and CP210 treatments (80.2, 77.4, 73.1, 70.5, and 65.0%, respectively). As a result, increasing CP levels per 100 kg BW could rise nutrients digestibility and digestible value for Wagyu crossbred cattle. The level of 245 g CP per 100kg live weight in Wagyu crossbred cattle diet from 13 to 20 months of age could be recommended for application.

Lactational performance effects of supplemental histidine in dairy cows: A meta-analysis

The objective of this meta-analysis was to examine the effects of supplemental His on lactational performance, plasma His concentration and efficiency of utilization of digestible His (EffHis) in dairy cows. The meta-analysis was performed on data from 17 studies published in peer-reviewed journals between 1999 and 2022. Five publications reported data from 2 separate experiments, which were included in the analyses as separate studies, therefore resulting in a total of 22 studies. In 10 studies, His was supplemented as rumen-protected (RP) His; in 1 study, 2 basal diets with different dHis levels were fed; and in the remaining experiments, free His was infused into the abomasum (4 studies), the jugular vein (3 studies) or deleted from a mixture of postruminally infused AA (4 studies). The main forages in the diets were corn silage in 14 and grass silage in 8 studies. If not reported in the publications, the supplies of dietary CP, metabolizable protein (MP), net energy of lactation, and digestible His (dHis) were estimated using NRC (2001). An initial meta-analysis was performed to test the standard mean difference (SMD; raw mean difference of treatment and control means divided by the pooled standard deviation of the means), that is, effect size, and the corresponding 95% confidence interval (CI) in production parameters between His-supplemented groups versus control. Further, regression analyses were also conducted to examine and compare the relationships between several response variables and dHis supply. Across studies, His supplementation increased plasma His concentration (SMD = 1.39; 95% CI: 1.17-1.61), as well as DMI (SMD = 0.240; 95% CI: 0.051-0.429) and milk yield (MY; SMD = 0.667; 95% CI: 0.468-0.866), respectively. Further, milk true protein concentration (MTP; SMD = 0.236; 95% CI: 0.046-0.425) and milk true protein yield (MTPY; SMD = 0.581; 95% CI: 0.387-0.776) were increased by His supplementation. Notably, the increase in MTP concentration and MTPY were 3.9 and 1.3 times greater for studies with MP-deficient (according to NRC 2001) diets compared with studies with MP-adequate diets. The regression analyses revealed that production parameters (DMI, MY, and MTPY) responded in a nonlinear manner to increasing His supply. Further, we detected a difference in the magnitude of change in MTPY and plasma His concentration with the level of His supply and between His supplementation methods, being greater for infused His compared with RPHis. Lastly, a linear and negative relationship between EffHis and the ratio of total digestible His to net energy for lactation supply was observed, indicating an important interaction between dHis and energy supply and EffHis (i.e., utilization of dHis to support protein export). Overall, these analyses confirm His as an important AA in dairy cattle nutrition.

Colour Stability, Fatty Acid Profile, and Lipid Oxidation in Meat Stored in Modified Atmosphere Packaging from Light Lambs Fed with Concentrate with Carob Pulp (Ceratonia siliqua L.).

There is a growing interest in using by-products rich in polyphenols, such as carob pulp (Cp, Ceratonia siliqua L.), as a dietary source of antioxidants for animals. This study assesses the effects of including Cp in lambs' diet and meat display time (0, 7, 9, and 11 days) in modified atmosphere packaging on meat colour, fatty acid (FA) composition, tocopherol levels, and lipid oxidation values in the Semimembranosus muscle of 40 light lambs. The lambs were fed with concentrates supplemented with increasing Cp levels (0, 150, and 300 g/kg) for 45 days before slaughter. Metmyoglobin (MMb) and malondialdehyde (MDA) contents increased linearly with display time (p < 0.05), regardless of diet (p > 0.05). At 11 days of display, MMb (28 ± 0.8%) and MDA (0.6 ± 0.1 mg MDA/kg of meat) contents remained within the acceptable limits. The α-tocopherol content was lower in the 30% Cp group and meat (p < 0.05). Total saturated and monounsaturated FA contents (934 ± 64 and 823 ± 65 mg/100 g of meat, respectively) did not differ significantly among the groups. However, the meat from lambs fed with 30% Cp showed reduced levels of branched-chain FAs, while polyunsaturated FAs increased (p < 0.05) compared to the control lambs. The inclusion of Cp in the lamb's diet, up to 30%, did not lead to meat deterioration and improved certain quality parameters, including a healthier FA profile. These findings highlight Cp's potential as an alternative antioxidant source in animal diets.

Dietary crude protein reductions in wheat-based diets with two energy densities compromised performance of broiler chickens from 15 to 36 days post-hatch

This study was designed to investigate the impacts of 2 energy densities (13.0 and 12.5 MJ/kg ME) in wheat-based diets with 3 tiers of CP concentrations (210, 190, and 170 g/kg) on the performance of broiler chickens. The parameters assessed included growth performance (15-36 d posthatch), carcass traits, nutrient utilization, starch-protein digestive dynamics, apparent ileal amino acid digestibility coefficients, and the free amino acid and ammonia (NH3) concentrations in systemic plasma. Also, the feasibility of substituting soybean meal with canola meal in 190 g/kg CP diets was investigated. The dietary CP reduction from 210 to 170 g/kg significantly compromised weight gain by 12.4% (1,890 vs. 2158 g/bird) and FCR by 5.33% (1.501 vs. 1.425). The 0.5 MJ energy density reduction compromised FCR by 3.25% (1.525 vs. 1.477; P=0.013) in birds offered 170 g/kg CP diets. Reducing dietary CP and energy densities interactively influenced (P=0.027) apparent metabolizable energy (AME) and nitrogen corrected metabolizable energy (AMEn) (P=0.022) such that reducing dietary CP increased these parameters but reducing dietary energy densities decreased AME and AMEn. The 150 g/kg canola meal inclusion with the elimination of soybean meal displayed some promise. Dietary CP reductions (and increased nonbound amino acid inclusions) linearly associated with increased plasma ammonia (NH3) concentrations (r=-0.607; P=0.010) and plasma NH3 was linearly related to depressed weight gains (r=-0.565; P=0.018). The association of dietary non-protein-bound amino acid (NPBAA) inclusions and elevated plasma NH3 concentrations have profound implications for the successful development of reduced-CP, wheat-based broiler diets.

Effects of dietary niacinamide and CP concentrations on the nitrogen excretion, growth performance, and meat quality of pigs.

Reducing the dietary CP concentration in the formulation of low-protein diets without adverse effects on animal growth performance and meat quality remains challenging. In this study, we investigated the effects of nicotinamide (NAM) on the nitrogen excretion, growth performance, and meat quality of growing-finishing pigs fed low-protein diets. To measure the nitrogen balance, we conducted two trials: in nitrogen balance trial 1, four crossbred (Duroc×Landrace×Large White) barrows (40±0.5kg BW) were used in a 4×4 Latin square design with four diets and periods. The diets consisted of a basal diet+30mg/kg NAM (a control dose), basal diet+90mg/kg NAM, basal diet+210mg/kg NAM, and basal diet+360mg/kg NAM. In nitrogen balance trial 2, another four barrows (40±0.5kg BW) were used in a 4×4 Latin square design. The diets consisted of a basal diet+including 30mg/kg NAM (control), basal diet+360mg/kg NAM, low-protein diet+30mg/kg NAM, and low-protein diet+360mg/kg NAM. To measure growth performance, two trials were conducted. In growth performance trial 1, 40 barrows (37.0±1.0kg) were randomly allocated to one of four dietary treatments (n=10 per group), whereas in growth performance trial 2, 300 barrows (41.4±2.0kg) were randomly allocated to one of four dietary treatments, with each dietary treatment conducted in five repetitions with 15 pigs each. The four diets in the two growth performance trials were similar to those in nitrogen balance trial 2. Supplementing the diet with 210 or 360mg/kg NAM reduced urinary nitrogen excretion and total nitrogen excretion and increased nitrogen retention comparted with the control diet (P<0.05). Compared with the control diet, the low-protein diet with 360mg/kg NAM reduced faecal, urinary, and total nitrogen excretion (P<0.05) without affecting nitrogen retention and average daily gain (P>0.05). Pigs fed the low-protein diet with 360mg/kg NAM showed a decreased intramuscular fat content in the longissimus thoracis muscle when compared with pigs fed the control diet (P>0.05). Our results suggest NAM as a suitable dietary additive to reduce dietary CP concentration, maximise nitrogen retention and growth performance, and decrease fat deposition in pigs.

Growth Performance of Live Fish Feed: Artemia salina in Different Supplemental Feeds in Aquarium Culture

Artemia is an excellent live feed for newly hatched fish and crustaceans gained a unique position in the aquaculture system. Brine shrimp is a non-selective filter feeder, so different locally available source feeds should be evaluated as potential food source for their control mass culturing. The experiment was carried out to study the effect of different supplement feeds on the growth performance of Artemia at Central Fisheries Promotion and Conservation Centre, Baalaju, Kathmandu from December 2021 to February 2022. The experiment was carried out in complete randomized design (CRD) with four treatments, each treatment consisting four replications. Four treatments consist different combination of supplement feed i.e., T1: (spirulina + rice bran), T2: (soyabean + rice bran), T3: (Mustard oilcake + rice bran), T4: (Yeast + rice bran). All supplement feed contains 25% CP and feed diet was supplied by 2% of body weight. In terms of growth and yield performance parameters, significant effect was recorded on average length, individual weight and total biomass. Also, significant effect was recorded on survivability and density. However, no significant effect was recorded on CP content of Artemia biomass. T1 recorded the maximum average length (8.7±0.21 mm), individual weight (0.0028±0.0001 gm), and biomass (1.79±0.069 gm/L) whereas lowest average length (7±0.08 mm), individual weight (0.0013±0.0002 gm) and biomass (0.61±0.005 gm) was recorded in T4. Also, T1 recorded the maximum density (633.8±3.62), and survivability (70.8±0.5) whereas lowest density(467.9±4.26) and survivability (58.0±1,71) found in T4. Hence it can be concluded that the combination of spirulina and rice bran was best supplement diet and can be applied in the cultivation of Artemia for best growth performance and biomass Production in aquarium condition.

Assessing chamomile and marjoram meals as feed additives on growth indices and haematological parameters of Nile tilapia (Oreochromis niloticus) reared under biofloc system

First report on using chamomile (Matricaria chamomilla) flower meal [CFM] and marjoram (Origanum majorana) leaves meal [MLM] as dietary supplements in low-protein fish diets on Nile tilapia (Oreochromis niloticus) reared in a bio-floc system. The experiment consisted of 6 groups in triplicates, where the first (T1) and second (T2) groups were fed diets containing 25 and 20% protein, respectively, without any additives. In contrast, the rest of the groups were fed a 20% protein diet, adding CFM at rates of 1% (T3) and 2% (T4) or MLM at rates of 1% (T5) and 2% (T6). The fish were initially weighed 18.44 g ± 0.38 (S.E.) and randomly stocked in 18 experimental tanks at six fingerlings in a water volume of 40 litres (150 fish/m3). Molasses was used as a carbon source with a carbon-to-nitrogen ratio of 16:1 in the treatments fed 20% protein; 12:1 in the treatments provided 25% protein. Feeding was done twice daily, six days a week, at a rate of 3% of body weight for 42 days. Water quality was within the desirable tilapia growth and health limit regarding temperature (23.20 - 24.70 °C), pH (8.43 - 8.65), dissolved oxygen (5.5 - 6.1 mg/L), and NH3 (0.03–0.051 mg/L). Fish fed on a 20% CP diet containing 1% CFM had the highest values in all growth indicators, followed by 2% CFM and 1% MLM then T1 and T2 groups. Blood analysis showed variation (P ≤ 0.05) among groups, and T3 had the highest levels of hemoglobin (Hb), hematocrit (Hct), and red blood cells (RBCs) followed by T5 then T4, T2, while T6 and T1 were the least. In conclusion, using chamomile or marjoram as a feed supplement maximizes the benefits of using the bio-floc system, especially in a lack of water resources and poor protein feeds. Nile tilapia growth and hematological parameters were the best with a 1% chamomile (M. chamomilla) supplement under a biofloc system.

Effects of Amount and Profile of Amino Acids Supply on Lactation Performance, Mammary Gland Metabolism, and Nitrogen Efficiency in Holstein Dairy Cows.

To evaluate the effects of amount and profile of amino acid (AA) on milk protein yield (MPY), mammary metabolism, and efficiency of nitrogen use (ENU), ten cows were used in 5 × 5 replicated Latin squares and fed a positive control (16.1% crude protein-CP) or two lower CP diets (14.6 and 13.2%) with or without essential AA (EAA) infusion. The EAA solutions provided predicted limiting EAA in each treatment and were continuously infused into the abomasum of the cows. Milk production and MPY were not affected by treatment (mean 35.4 kg/d and 1.03 kg/d, respectively). Efficiency of nitrogen utilization was increased as dietary CP decreased but was not affected by EAA infusion (p < 0.01). Energy-corrected milk production was increased by EAA infusion into 13.2% CP, but not into 14.6% CP diet (p = 0.09), reaching the positive control value. Infusions increased mammary affinity for non-infused EAA (Ile, Phe, Thr, and Trp), allowing the same MPY despite lower arterial concentrations of these AA. Higher arterial concentrations of infused EAA did not increase their mammary uptake and MPY (p = 0.40; p = 0.85). Mammary metabolism did not fully explain changes in N efficiency, suggesting that it might be driven by less extramammary catabolism as AA supply was reduced.

Hempseed meal as a feedstuff in the diet of growing meat rabbits

Though currently not approved in the USA as an agricultural animal feed ingredient, our objective was to determine the effects of hempseed meal replace- ment of traditional CP sources in the diet of growing meat rabbits on intake, growth performance, and visceral organ weights. Pelleted rations were formu- lated in which hempseed meal replaced alfalfa meal and soybean meal at 4 levels (CON, LOW, MED, and HIGH, representing 0, 25, 50, or 75% of the ration CP, respec- tively). Weaned Californian rabbits (n = 64) were pen fed (4 rabbits per pen, 2 pens per treatment) in each of 2 periods for 35 d. After feeding, rabbits were slaughtered via cervical dislocation. Dry matter intake was great- est (P < 0.05) from LOW, followed by MED and then CON, and was least (P < 0.05) from HIGH. Similarly, total weight gain and ADG were greatest (P < 0.05) from LOW (1,230 g and 35.1 g/d, respectively), followed by MED (1,163 g and 33.2 g/d, respectively) and then CON (1,067 g and 30.5 g/d, respectively), and were least (P < 0.05) from HIGH (725 g and 20.7 g/d, respectively). There was a quadratic response (P = 0.03) of treatment for DM digestibility, whereby DM digestibility decreased by 10% from CON to LOW before increasing by 14% with HIGH. Results suggest that hempseed meal may be included in the ration of growing meat rabbits (once legally approved) at low concentrations (25% of dietary CP) for enhanced production.

A step toward a biofloc system with no‐carbon addition: Increasing dietary lipid level enhances the water quality and body chemical composition without affecting tilapia health status

AbstractA 70‐day experiment was carried out to evaluate biofloc system operation with no carbon addition by manipulating dietary protein and lipid levels for Nile tilapia (Oreochromis niloticus) cultivation. Three treatments were conducted; Control treatment (C; fed on a 30% crude protein [CP] diet supplemented with 3% vegetable oil [VO] + addition of external carbon source [ECS] in rearing tank), low protein–low lipid treatment (LPLL; fed on 23% CP diet supplemented with 3% (VO) + no addition of ECS) and low protein–high lipid treatment (LPHL; fed on 23% CP diet supplemented with 9% VO + no addition of ECS). The C treatment recorded the highest values (p &lt; 0.05) in terms of final body weight (FBW), specific growth rate, floc volume, total suspended solids, and ammonia nitrogen. No significant differences were observed between C and LPHL treatments regarding FBW and protein efficiency ratio. The liver sections of LPHL treatment showed better values for histological alteration index compared to the control. It could be concluded that applying a biofloc system with no carbon addition using LPHL diets may afford better water quality conditions, limit the environmental impact and decrease dietary costs with limited effect on fish performance.

84 Relationships between feed protein fractions and the hindgut microbiome in the exercising horse

The effect of dietary protein on the microbiome in the horse has limited data. In this study, 16 horses (averaging 606 kg BW) were used to evaluate the effect of protein source (forage, F, or forage and concentrate, FC) on hindgut microbiome. Horses were fed grass hay (timothy/orchardgrass). Those in the FC groups were also fed concentrate (Legends Growth, Southern States) at a ratio of 30:70 concentrate to forage. Horses consumed 2.44, 2.26 and 3.19 g CP/kg BW/d respectively for the F, FC(low and high CP) groups. Diets were fed for 14 wk. Horses participated in light exercise (1–2 h/d, 5 d/wk). Forage, concentrate and fecal samples were collected every 2 wk. Forage and concentrate samples were analyzed for CP, ADICP (acid detergent insoluble protein) and NDICP (neutral detergent insoluble protein). Fecal samples were analyzed for bacterial community abundance (PCR and sequencing). Statistical analysis of fecal communities was done using the Krustal-Wallis analysis and correlations determined using Slidewrite Plus. At the phylum level, there were positive linear correlations between the amount of daily CP from forage (g/kg BW/d) for both the F and FC groups for Proteobacteria (r = 0.54, P < 0.05), and Firmicutes (r = 0.55 and 0.7 respectively, P < 0.05). There was a positive linear correlation between ADICP and Proteobacteria for the FC groups (r = 0.8, P < 0.05). There was a linear correlation with Firmicutes (r = 0.59 and 0.82 respectively, P < 0.05), and quadratic correlations withBacteroidetes (r = 0.58 and 0.8 respectively, P < 0.05) and Tenericutes (r = 0.59 and 0.92 respectively, P < 0.05) for the FC and F groups with abundances increasing then decreasing for Bacteroides and vice versa for Tenericutes. For NDICP, there was a positive linear correlation with Firmicutes (r = 0.62, P < 0.05) and Proteobacteria (r = 0.52, P < 0.05) for the FC groups and for Fibrobacteres (r = 0.95 and 0.89 respectively, P < 0.05), while Bacteroides (r = 0.57 and 0.8 respectively, P < 0.05) as well as Tenericutes (r = 0.62 and 0.94 respectively, P < 0.05) had quadratic correlations with abundances decreasing then increasing for Bacteroides and vice versa for Tenericutes for FC and F groups. Nitrogen is needed in the hindgut for the microbiome and the changes observed in the Firmicutes and Fibrobacteres support this. In swine, excess dietary CP changed the microbiome that negatively affect gut health. This study suggests N has importance to the hindgut microbiome but also that excessive protein may impact the microbiome as well. Changes in the microbiome in horses due to diet which may affect fiber digestibility, gut and host health warrant further investigation in the horse.

Effects of dietary protein concentration and degradability on performance, carcass characteristics, net energy utilization, and metabolizable protein balance of finishing beef heifers receiving 0 or 400 mg of ractopamine hydrochloride

This study evaluated the effects of feeding beef cattle finishing diets with greater than 14.0% dietary CP and with or without ractopamine hydrochloride (RH) on growth performance, carcass merit, net energy utilization, and metabolizable protein balance. Heifers (n = 525) were assigned to 48 pens in a generalized complete block design, and pens of cattle were assigned randomly to 0 or 400 mg of RH/animal per day and 3 CP treatments in a 2 × 3 factorial arrangement (n = 8 pens/treatment) fed for 35 d before slaughter. Dietary protein treatments were steamflaked corn-based diets containing 13.9% CP, 8.9% RDP, and 5.1% RUP (CON); 20.9% CP, 14.4% RDP, and 6.5% RUP (High RDP); or 20.9% CP, 9.7% RDP, and 11.2% RUP (High RUP) on a DM basis. No RH × CP interactions were observed. Final BW, ADG, water disappearance, DMI, and G:F were not different among CP treatments. Dressing percentage was greater for cattle fed High RDP than for those fed High RUP, but other carcass outcomes did not differ. The MP balance was greatest for High RUP, intermediate for High RDP, and least for CON. Cattle receiving 400 mg of RH had greater final BW, ADG, G:F, and hot carcass weight. The LM area was greater and KPH was less for 400 versus 0 mg of RH. Carcass-adjusted final BW, ADG, and G:F were greater for cattle consuming 400 mg of RH. Cattle fed 400 mg of RH had greater performance-adjusted and observed:expected NEm and NEg. The MP balance was less for 400 versus 0 mg of RH. Dietary CP requirements were greater for cattle fed 400 compared with 0 mg of RH but did not exceed the CP supplied by CON, High RDP, or High RUP. Feeding greater than 14.0% CP does not negatively affect performance or carcass characteristics of finishing cattle, and the absence of interactions between CP and RH suggests that RH does not increase CP requirements above those provided in a typical finishing cattle diet.

Ruminal tissue uptake of amino acids in Holstein cows when supply of nutrients within the rumen differs

Characterisation of amino acid (AA) use by the ruminal vein-drained viscera (RDV) has not been assessed in vivo in dairy cattle, and thus, the extent of ruminal AA use from arterial and postabsorptive blood supplies is unclear. Understanding the complete use of AA by the splanchnic bed may lead to alternative feeding programmes that maximise animal N efficiency. The objective of this work was to determine how different nutritional manipulations affect RDV net appearance and apparent affinity for arterial AA in lactating dairy cattle. Data from two arterio-venous (A-V) difference studies, that used a common set of multicatheterised lactating Holstein cows, assigned to different nutritional treatments, were used to assess ruminal metabolism. Study 1 consisted of three dietary treatments at calving [an alfalfa-glucogenic diet, a glucogenic diet (GLCG), or a ketogenic diet (KETO)] to investigate the effects of dietary nutrients and increasing intake postpartum on RDV metabolism of AA at −14, +4, +15, and +29 days relative to calving (DRTC). Study 2 consisted of two dietary levels of CP (17 or 13%) and three ruminal buffers (ammonia, butyrate, and control) to investigate the level of dietary CP and ruminal fermentation products on RDV metabolism of AA. Blood was collected at 9, 20, and 30 min after buffer administration. Regardless of dietary nutrients or fermentation products present in ruminal fluid, net RDV uptake was positive for most AA, excepting Asp, Cys, Glu, and Ser, which were consistently negative. The general positive net uptakes indicate that any AA potentially absorbed from the rumen were not adequate to meet apparent needs. Ruminal plasma flow and net RDV uptake of Trp, Ala, Gly, and Pro increased linearly with increased DRTC. Feeding KETO or GLCG diets increased ruminal plasma flow, and net RDV uptake of Thr and Gly. Feeding high CP diets increased ruminal uptake of Leu, Phe, and Val. The increased AA uptakes were partially driven by increased plasma flow, however, tissue affinity as reflected in clearance rates also increased or tended to for Met, Trp, Ala, Gly, Pro, and Tyr suggesting that changes in RDV uptake were regulated and not due solely to mass action. In conclusion, splanchnic tissue bed responses to dietary and washed rumen conditions were in part driven by changes in RDV nutrient demand and metabolic activity. The adaptive responses alter the fraction of absorbed AA utilised for non-productive purposes and thus the efficiency of conversion of those AA to product.

The influence of dietary protein concentration on digestive enzyme activities, growth, and body composition in juvenile bullseye snakehead (Channa marulius).

The bullseye snakehead (Channa marulius) is considered as an affordable and robust freshwater fish for farming in Asia. However, there is limited knowledge on the species' full nutritional requirements to date with extensive gaps in our knowledge and particularly in precision aspects of protein requirements. Therefore, a three-month feeding trial was conducted under semi-intensive farming conditions to determine the protein requirement of bullseye snakehead using test diets containing 40 (P40), 45 (P45), 50 (P50), and 55% (P55) crude protein levels. The growth performance results revealed that the 55% dietary protein group (P55) had the highest final mean weight (14.09 g fish-1), and net weight gain (12.82 g fish-1). When compared to other dietary treatments, the final weight (R2 = 0.921), and weight gain (R2 = 0.913), displayed a linear increasing trend as dietary protein is raised. The lowest FCR was observed in 50% (1.94±0.01) and 55% (1.97±0.01) CP diet groups compared to dietary treatments. Further analysis has shown that the body protein content also significantly increased as dietary protein was raised to 55%. Although, a reverse trend was found in body lipid levels with increasing protein in the diet. The incremental dietary protein also elevated proximal intestinal protease activity but decreased amylase and lipase activity. The overall essential and non-essential amino acids levels of snakehead fillet muscle reflected an increase in dietary protein. Overall, this study has shown that the fish fed a diet with 55% crude protein attained the highest growth performance and nutrient profile of the whole fish when compared to other dietary treatments tested. It would appear we did not obtain the maximum potential for growth under the present experimental conditions due to the upper protein constraint of 55% in the diet. Further quantitative studies are suggested.