Evaluation of corn gluten meal with urea as a source of supplementary nitrogen for growing calves and lambs

Three growth trials and a metabolism study were conducted to evaluate corn gluten meal—urea (CGM—urea) combinations compared to a urea control as sources of supplementary nitrogen for growing calves and lambs fed on diets based on corn cobs.In the first growth study cattle were fed individually twice daily while in the sheep growth study and the second cattle growth study, animals were fed in groups. The average daily gain and feed conversion were similar for animals given the soya bean meal (SBM) and CGM—urea supplements. Feed intakes were similar for all treatments except for growth study 1. Nitrogen retention and dry matter and protein digestibility did not differ significantly between the SBM and CGM—urea supplemented groups. Urea consistently gave inferior results in all the experiments. These results suggest that CGM—urea combination is essentially equal to SBM in supporting growth of calves and lambs.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal, soybean meal and white flakes

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal,soybean meal and white flakes

Abstract

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Effects of dietary fish meal and soybean meal on the ovine innate and acquired immune response during pregnancy and lactation

In recent years, livestock producers have been supplementing animal diets with fish meal (FM) to produce value-added products for health conscious consumers. As components of FM have unique neuroendocrine–immunomodulatory properties, we hypothesize that livestock producers may be influencing the overall health of their animals by supplementing diets with FM. In this study, 40 pregnant ewes were supplemented with rumen protected (RP) soybean meal (SBM: control diet) or RP FM, commencing gestation day 100 (gd100), in order to evaluate the impact of FM supplementation on the innate and acquired immune response and neuroendocrine response of sheep during pregnancy and lactation. On gd135, half the ewes from each diet (n = 10 FM, n = 10 SBM) were challenged iv with lipopolysaccharide (LPS) to simulate a systemic bacterial infection and the febrile, respiratory and neuroendocrine responses were monitored over time; the other half (n = 10 FM, n = 10 SBM) of the ewes received a saline injection as control. On lactation day 20 (ld20), all ewes (n = 20 FM, n = 20 SBM) were sensitized with hen egg white lysozyme (HEWL) and the serum haptoglobin (Hp) response was measured over time. The cutaneous hypersensitivity response (CHR) to HEWL challenge was measured on ld30 (n = 20 FM, n = 20 SBM), and blood samples were collected over time to measure the primary and secondary immunoglobulin G (IgG) response to HEWL. There was an attenuated trend in the LPS-induced febrile response by the FM treatment when compared with the SBM treatment (P = 0.06), as was also true for the respiratory response (P = 0.07), but significant differences in neuroendocrine function (serum cortisol and plasma ACTH) were not observed between treatments. Basal Hp levels were significantly lower in the FM supplemented ewes when compared with the SBM supplemented ewes (P < 0.01), and the Hp response to HEWL sensitization differed significantly over time between treatments (P < 0.01). The CHR to HEWL was also significantly attenuated in the FM treatment compared with the SBM (P < 0.01); however, treatment differences in the primary and secondary IgG responses to HEWL were not observed. These results indicate that FM supplementation differentially affects the innate and acquired immune responses in pregnant and lactating sheep compared with a typical SBM diet of commercial flocks. The long-term implications of this immunomodulation warrant further investigation.     

Effects of feeding low fishmeal diets with increasing soybean meal levels on growth,gut histology and plasma biochemistry of sea bass

The aquaculture industry depends upon the development of sustainable protein sources to replace fishmeal (FM) in aquafeeds and the products derived from soybeans are some of the most studied plant feedstuffs. A key area of investigation for continuing to improve modern aquafeeds includes the evaluation of varying proportions and combinations of plant ingredients to identify mixtures that are more efficiently utilized by the fish. This study investigated the effects of increasing soybean meal (SBM) by replacing a mix of plant ingredients in low FM (20%) diets on growth, blood biochemistry profile and gut histology on European sea bass. Five isonitrogenous and isolipidic experimental diets were formulated: four diets containing increasing SBM levels (0, 10, 20 and 30%; 0SBM, 10SBM, 20SBM and 30SBM, respectively) with a low content of FM (20%) and one control diet (0% SBM; 35% FM). Diets containing SBM brought to comparable performance and protein utilization, while 0SBM had negative impact on feed conversion rate and protein utilization. Blood parameters suggested an optimal nutritional status under all feeding treatments, even though slightly decreased values were reported at increasing dietary SBM. Histology examination did not show any changes indicative of soy-induced enteritis. We can conclude that for European sea bass: (i) different blends of plant protein did not affect feed intake despite the 20% FM dietary level; (ii) the inclusion of SBM maintains optimal growth and feed utilization in low FM diets; (iii) blood biochemistry profile showed a good nutritional status under all feeding regimes; (iv) no evidence of soy-induced enteritis was reported in any group fed low FM diets. For formulation of practical diets in on-growing of European sea bass, SBM up to 30% can be successfully incorporated into feeds containing low FM inclusion.     

A combination of corn gluten and soybean meal as a substitute for fishmeal in diets of turbot (Scophthalmus maximus Linnaeus, 1758) in brackish water

This study was conducted to test the replacement of fishmeal (FM) with a combination of corn gluten meal (CGM)‐soybean meal (SBM) (at a ratio of 58 : 42, respectively) fortified with lysine, taurine and monocalcium phosphate (MCP) in turbot (Scophthalmus maximus) diets. FM as the main protein source in the control diet (FM100) was replaced in 15% decrements while increasing the combination of replacement material: 85% FM (FM85), 70% FM (FM70), 55% FM (FM55) and 40% FM (FM40). The diets were fed to triplicate groups (n = 25 per group) for 9 weeks (water temperature, dissolved oxygen, pH and salinity of 18.59 ± 0.06°C, 7.32 ± 0.02 mg L^?1, 7.73 ± 0.01 and 8.46 ± 0.04 g L^?1, respectively). Initial weight of fish was 286.1 ± 0.1 g. At the end of the experiment, growth, feed and nutrient utilization performance of fish fed FM85 and FM70 were similar to FM100, but a further increase in plant protein led to a significant reduction of these parameters. Whole body, fillet, viscera and liver nutrient compositions were not affected significantly; however, whole body lipid levels were significantly lower in fish on FM55 and FM40 than those on FM100. The fish in–fish out ratio in the diets decreased from 2.12 in FM100 to 1.00 in FM40. The results suggest that the FM level could be reduced by 30% with a combined use of CGM‐SBM supplemented with lysine, taurine and MCP.     

Plant products affect growth and digestive efficiency of cultured Florida pompano (Trachinotus carolinus) fed compounded diets

Costs of compounded diets containing fish meal as a primary protein source can be expected to rise as fish meal prices increase in response to static supply and growing demand. Alternatives to fish meal are needed to reduce production costs in many aquaculture enterprises. Some plant proteins are potential replacements for fish meal because of their amino acid composition, lower cost and wide availability. In this study, we measured utilization of soybean meal (SBM) and soy protein concentrate (SPC) by Florida pompano fed compounded diets, to determine the efficacy of these products as fish meal replacements. We also calculated apparent digestibility coefficients (ADCs) for canola meal (CM), corn gluten meal (CGM), and distillers dried grains with solubles (DDGS), following typical methods for digestibility trials. Juvenile Florida pompano were fed fish-meal-free diets containing graded levels of SBM and SPC, and weight gain was compared to a control diet that contained SBM, SPC, and fish meal. Fish fed diets that contained 25-30 percent SBM in combination with 43-39 percent SPC had weight gain equivalent to fish fed the control diet with fish meal, while weight gain of fish fed other soy combinations was significantly less than that of the control group. Apparent crude protein digestibility of CGM was significantly higher than that of DDGS but not significantly different from CM. Apparent energy digestibility of DDGS was significantly lower than CGM but significantly higher than CM. Findings suggested that composition of the reference diet used in a digestibility trial affects the values of calculated ADCs, in addition to the chemical and physical attributes of the test ingredient.     

Effects of protein sources on concentrations of hydrogen sulphide in the rumen headspace gas of dairy cows

Two Latin square design experiments investigated the relationship between hydrogen sulphide concentration in the rumen headspace gas of dairy cows and the early stages of protein degradation in the rumen. In Expt 1, three protein sources differing in rumen N (nitrogen) degradability (maize gluten feed (MGF); sunflower meal (SFM); and soyabean meal (SBM)) were used, whereas in Expt 2 four different batches of the same feed (MGF) differing in colour (CIE L*, a*, b* (CIELAB) scale) were used. After allowing the concentration of hydrogen sulphide in rumen gas to decline close to zero, a fixed amount of protein sources was offered to cows and the concentrations of hydrogen sulphide were recorded in rumen headspace gas at 30-min intervals. In Expt 1, the concentration of hydrogen sulphide showed considerable variation between protein sources, with MGF having the highest concentration followed by SFM and SBM resulting in very low concentrations. The N wash losses (zero time measurements with nylon bags) ranked the feeds in the same way, from MGF (highest; 61%) to SBM (lowest; 26%). There were marked differences in the degradation of cystine and methionine between protein sources, although the degradation of cystine was always higher than for methionine. MGF (Expt 2) led to increased concentrations of hydrogen sulphide, with peak concentrations achieved between 1 and 2 h after feeding. The concentrations of hydrogen sulphide were higher for MGF1, intermediate for MGF2 and lower for MGF3 and MGF4, agreeing with colour scale. Differences in the early stages of dietary sulphur degradation corresponded with differences in hydrogen sulphide concentrations in rumen gas. The results suggest that hydrogen sulphide concentrations in the rumen headspace gas could be useful to evaluate nutritional parameters not measured by the in sacco technique, contributing to a better understanding of the response of dairy cows to different protein supplements.     

发酵豆粕替代鱼粉和豆粕对罗氏沼虾生长、血清生化及免疫基因表达的影响

为研究发酵豆粕在罗氏沼虾饲料中的适宜用量及替代后可能造成的影响, 以含有30%鱼粉和18%豆粕的饲料为基础饲料(T0组), 分别用2% (T2组)、5% (T5组)、8% (T8组)、15% (T15组)的发酵豆粕等蛋白替代基础饲料中的鱼粉和豆粕(2﹕1), 共配制5种等氮等能的实验饲料。选用初始均重为(0.17±0.02) g的罗氏沼虾在室内水泥池网箱中进行为期64d的养殖实验。结果显示, 发酵豆粕对鱼粉和豆粕的替代量影响罗氏沼虾的生长、血清生化及免疫基因表达。随着发酵豆粕添加量的增加, 增重率和特定生长率呈先升后降的趋势, 都以T8组最高。血清中丙二醛含量、超氧化物歧化酶活力随发酵豆粕添加量的增加均呈先升后降的趋势, 各替代组丙二醛含量均显著高于对照组(P<0.05); 血清谷丙转氨酶、谷草转氨酶活性和总蛋白含量呈先下降后上升的趋势, 且替代组不同程度低于对照组; T15组Toll受体、NF-κB、HSP70转录水平表达量显著高于其他各组(P<0.05)。以上结果表明用不同水平的发酵豆粕替代鱼粉和豆粕, 显著影响罗氏沼虾的生长性能、抗氧化能力及免疫机能; 在实验条件下, 罗氏沼虾饲料中的发酵豆粕最佳使用量为8%。     

团头鲂幼鱼对不同浓度胆碱的利用率及7种常见饲料原料中胆碱生物学效价的评定

研究常见饲料原料中胆碱的生物学效价,为渔用配合饲料配制提供基础数据。试验选取团头鲂平均体重（3.50.1）g 990尾,以酪蛋白、明胶等原料配制4个氯化胆碱添加水平（0、1030、1230、1430 mg/kg）的纯合饲料,并在1030 mg/kg的基础上分别添加7种常见饲料原料（鱼粉、豆粕、菜粕、棉粕、次粉、麸皮、米糠）,使得各组配合饲料中胆碱含量为1230 mg/kg,共11组,每组3重复,饲养8周。根据肝脏胆碱沉积量和试验鱼胆碱摄食量,评定团头鲂幼鱼对不同浓度的胆碱利用率和这7种原料中胆碱的生物学效价。结果表明:在4个纯和饲料中,肝脏胆碱沉积量和增重率随着饲料胆碱水平从0到1230 mg/kg饲料的增加而显著上升（P0.05）,并在饲料胆碱水平从1230到1430 mg/kg饲料的增加而差异不显著（P0.05）;在同一胆碱水平（1230 mg/kg）的条件下,原料组的增长率均高于对照组;团头鲂幼鱼对鱼粉、豆粕、菜粕、棉粕、次粉、麸皮和米糠的胆碱生物学效价分别为87.42%、112.54%、76.84%、98.00%、95.91%、43.88%、91.5%。分析可知,团头鲂生产饲料中尚需要额外添加氯化胆碱方能满足其对胆碱的需要,实际添加量与饲料所使用的原料有关。       

Preovulatory follicular status and diet affect the insulin and glucose content of follicles in high-yielding dairy cows

Insulin and glucose may be limiting factors for ovarian function in dairy cows genetically selected for high milk yield. The effects of nutrition on the intrafollicular content of insulin and glucose were investigated in Israeli Holstein dairy cattle fed a basic total mixed ration and producing 34-39kg of milk daily. In experiment 1, carried out in 11 oestrus-synchronised cows, little variation in insulin concentration was found in plasma sampled during the luteal phase, but high variation was found in plasma sampled during the follicular phase. Therefore, in order to prevent confounding the effects of diet and of phase in cycle in the following experiments, experimental diets were fed during the luteal phase of synchronised oestrus cycles. In experiment 2, designed as Latin-Square, six cows received sequentially diets containing 17.1 (control) or 19.7% of crude protein, using two sources of supplementary protein, i.e. soyabean meal (SBM) and corn gluten meal (CGM), differing in ruminal degradability and leucine content. When dry matter intake was used as covariant, plasma insulin on day 16 was 29.5 and 26.4% higher in cows fed diets containing SBM and CGM than in the control (P<0.05). In experiment 3, 17 cows were individually fed the basic diet and then switched to isoenergetic diets containing SBM (n=5), CGM (n=6) or corn grain (CG, n=6) given from day 10 to 16 of the synchronised oestrus cycle. On the eve of day 16, and in the morning of day 17, they were administered PGF(2alpha) and the content of 26 largest follicles was aspirated by using the transvaginal ovum pick-up technique. Follicles were sorted into two classes (preovulatory and subordinate) according to oestradiol concentration and the progesterone:oestradiol ratio in follicular fluid (FF). Higher concentrations of insulin (0.282 versus 0.127ng/ml, P<0.0001) and of glucose (0.614 versus 0.386g/l, P<0.002), were found in FF from preovulatory follicles. The insulin concentration in the FF of cows fed the CG diet was 26% higher than in their counterparts fed CGM (P<0.04), SBM being intermediate. Dietary effects did not reach significance in subordinate follicles.The finding that preovulatory follicular status is associated with increased intrafollicular insulin and glucose suggests that insulin is involved in follicular maturation. The nutritional effect on intrafollicular glucose and insulin may have practical implications to optimise feeding in dairy cows during phases of the oestrus cycle.     

Feeding behavior, rumination, reticulo-ruminal fermentation and plasma volatile fatty acids, compared in goats and sheep; influence of the diet

Two-year old Alpine she-goats (n = 3) and Texel ewes (n = 3) were compared as to eating behaviour, rumination and volatile fatty acids (VFA) in rumen and blood. The animals were fed once daily with two different proportions (20 and 80%) of barley and hay. Dry matter intake was fixed at 48 g D.M/kg P0.75 per day. In similar feeding and environmental conditions, eating behaviour and rumination of goats and sheep did not differ much: the goats tended to eat faster and there were more rumination periods in the sheep. Latency time, mean duration of rumination periods, daily rumination time and circadian pattern of rumination did not differ significantly between the two species (fig. 1). With both diets we observed a higher VFA concentration and a lower acetate/propionate ratio in the rumen of the ewes; however, rumen pH was lower only in those eating the 80% barley ration (fig. 2). Blood VFA in the jugular vein did not differ between sheep and goats (fig. 3). The proportion of cereals and hay in the diets affected rumen fermentation and rumination pattern in both species. With a higher concentrate/roughage ratio, rumen and plasma VFA increased, while the pH and acetate/propionate ratio in the lumen juice, the number of rumination periods and daily rumination time decreased. When the animals were fed the 80% barley ration, there was practically no rumination in the first 9 h after the single meal. During this time, rumen pH was minimal and VFA levels in the rumen and blood were maximal.     

Candida utilis and Chlorella vulgaris Counteract Intestinal Inflammation in Atlantic Salmon (Salmo salar L.)

Intestinal inflammation, caused by impaired intestinal homeostasis, is a serious condition in both animals and humans. The use of conventional extracted soybean meal (SBM) in diets for Atlantic salmon and several other fish species is known to induce enteropathy in the distal intestine, a condition often referred to as SBM induced enteropathy (SBMIE). In the present study, we investigated the potential of different microbial ingredients to alleviate SBMIE in Atlantic salmon, as a model of feed-induced inflammation. The dietary treatments consisted of a negative control based on fish meal (FM), a positive control based on 20% SBM, and four experimental diets combining 20% SBM with either one of the three yeasts Candida utilis (CU), Kluyveromyces marxianus (KM), Saccharomyces cerevisiae (SC) or the microalgae Chlorella vulgaris (CV). Histopathological examination of the distal intestine showed that all fish fed the SC or SBM diets developed characteristic signs of SBMIE, while those fed the FM, CV or CU diets showed a healthy intestine. Fish fed the KM diet showed intermediate signs of SBMIE. Corroborating results were obtained when measuring the relative length of PCNA positive cells in the crypts of the distal intestine. Gene set enrichment analysis revealed decreased expression of amino acid, fat and drug metabolism pathways as well as increased expression of the pathways for NOD-like receptor signalling and chemokine signalling in both the SC and SBM groups while CV and CU were similar to FM and KM was intermediate. Gene expression of antimicrobial peptides was reduced in the groups showing SBMIE. The characterisation of microbial communities using PCR-DGGE showed a relative increased abundance of Firmicutes bacteria in fish fed the SC or SBM diets. Overall, our results show that both CU and CV were highly effective to counteract SBMIE, while KM had less effect and SC had no functional effects.     

Effects of excess metabolizable protein on ovarian function and circulating amino acids of beef cows: 1. Excessive supply from corn gluten meal or soybean meal

In the dairy industry, excess dietary CP is consistently correlated with decreased conception rates. However, the source from which excess CP is derived and how it affects reproductive function in beef cattle is largely undefined. The objective of this experiment was to determine the effects of feeding excess metabolizable protein (MP) from feedstuffs differing in rumen degradability on ovulatory follicular dynamics, subsequent corpus luteum (CL) development, steroid hormone production and circulating amino acids (AA) in beef cows. Non-pregnant, non-lactating mature beef cows (n=18) were assigned to 1 of 2 isonitrogenous diets (150% of MP requirements) designed to maintain similar BW and body condition score (BCS) between treatments. Diets consisted of ad libitum corn stalks supplemented with corn gluten meal (moderate rumen undegradable protein (RUP); CGM) or soybean meal (low RUP; SBM). After a 20-day supplement adaptation period, cows were synchronized for ovulation. After 10 days of synchronization, gonadotropin releasing hormone (GnRH) was administered to reset ovarian follicular growth. Starting at GnRH administration and daily thereafter until spontaneous ovulation, transrectal ultrasonography was used to diagram ovarian follicular growth, and blood samples were collected for hormone, metabolite and AA analyses. After 7 days of visual detection of estrus, CL size was determined via ultrasound. Data were analyzed using the MIXED procedures of SAS. As designed, cow BW and BCS were not different (P⩾0.33). Ovulatory follicular wavelength, antral follicle count, ovulatory follicle size at dominance and duration of dominance were not different (P>0.13) between treatments. Cows supplemented with CGM had greater post-dominance ovulatory follicle growth, larger dominant follicles at spontaneous luteolysis, shorter proestrus, and larger ovulatory follicles (P⩽0.03) than SBM cows. No differences (P⩾0.44) in peak estradiol, ratio of estradiol to ovulatory follicle volume, or plasma urea nitrogen were observed. While CL volume and the ratio of progesterone to CL volume were not affected by treatment (P⩾0.24), CGM treated cows tended to have decreased (P=0.07) circulating progesterone 7 days post-estrus compared with SBM cows. Although total circulating plasma AA concentration did not differ (P=0.70) between treatments, CGM cows had greater phenylalanine (P=0.03) and tended to have greater leucine concentrations (P=0.07) than SBM cows. In summary, these data illustrate that excess MP when supplemented to cows consuming a low quality forage may differentially impact ovarian function depending on ruminal degradability of the protein source.     

Influence of dietary acetylated peptides on fermentation and peptidase activities in the sheep rumen

The predominant mechanism of peptide breakdown by rumen micro-organisms is aminopeptidase. Thus acetylation of the N-terminus of peptides inhibits their degradation by rumen micro-organisms in short-term incubations with rumen fluid in vitro . An experiment was undertaken to determine if adaptation of the rumen microbial population would take place when acetylated peptides were fed for a prolonged period, which would enable the microbial population to break down the protected peptides and thus decrease their nutritive value. Three adult sheep, fitted with permanent rumen cannulae, received a maintenance hay/concentrate diet to which was added, at each meal, 20 g of casein enzymic hydrolysate ('peptides') or 20 g of peptides previously treated with acetic anhydride. The diets were fed for 28 d in a 3 × 3 latin square and samples were taken during the last 7 d. Fermentation products and NH₃ concentrations indicated that acetylated peptides remained less degradable than untreated peptides. There was a trend towards increased proteolytic activity with acetylated peptides, and dipeptidase activity increased by 18% and 28%, respectively, compared with untreated peptides and control treatments. Activity against N-acetyl-Ala₂ also increased when acetylated peptides were fed, but it remained only 13% of the rate of Ala₂ hydrolysis. No increase was found in the rate of ammonia production from acetylated peptides in animals receiving acetylated peptides–this rate was 26% of that found with untreated peptides–and acetylated peptides continued to persist for longer in the rumen than untreated peptides after feeding. Thus it was concluded that the rumen microbial population did not adapt to utilize acetylated peptides.     

Effects of Changes in Feed Level, Starvation, and Level of Feed After Starvation Upon the Concentration of Rumen Protozoa in the Ovine

Four rumen fistulated sheep were used in five experiments to investigate the effect of feed level upon the concentration of rumen ciliate protozoa. The sheep were fed once daily 650 g of a pelleted diet composed of corn cobs, 45%; alfalfa meal, 35%; oats, 12.5%; cane molasses, 5%; urea, 0.4%; and vitamins and minerals, 2%. The concentration of protozoa reached minimum and maximum values at 5 and 22.5 h after feeding, respectively. Thus, to estimate apparent generation rates, concentrations of protozoa were determined at 5 and 20 h postfeeding. Apparent generation rate/h = natural log of ([concentration of protozoa at 20 h divided by concentration at 5 h] divided by the time interval, [T20 to T5]). Alteration of the feed to protozoa ratio by starvation and by changing the level of feed (200 to 900 g/day) showed that as the ratio of feed to protozoa increased, generation rate increased. Measurements of liquid turnover rates in the rumen showed that turnover rate decreased as feed level decreased. Turnover rate was near zero when the sheep were starved. Small quantities of soluble substrates, added directly to the rumen of starved sheep, maintained the protozoal population when rumen turnover was minimal. Furthermore, as rumen turnover rate increased with increased levels of feed, the effect of substrate on maintaining the protozoal population was negated. Thus, at high feed levels, turnover rate may be the dominant factor controlling the establishment and concentration of protozoa in the rumen.     

Rumen fermentation,nutrient flow to the duodenum and digestibility in bulls fed calcium soaps of rapeseed fatty acids and soya bean meal coated with calcium soaps

Three Polish Friesian bulls fitted with rumen and duodenal canulas were used in a 3 × 3 Latin square experiment to study the effect of Ca soaps of rapeseed fatty acids (CSRFA) on rumen fermentation, nutrient and fatty acid (FA) flow to the duodenum, and to investigate in vivo the possibility of using CSRFA as a means of protecting soya bean meal protein against degradation in the rumen. Treatments were (1) control, no fat (2) CSRFA, at 2% of dietary DM and (3) SBM protein coated with CSRFA (CSRFA:SBM, 1:1, wt/wt), at 4% of dietary DM. The animals were fed isonitrogenous diets, containing 45% meadow hay, 10% fodder beet and 45% concentrate mixture on a DM basis. Intake was limited to 80 g DM d⁻¹ kg^−0.75. There were no treatment effects on rumen fermentation, rumen liquid turnover rate or volume, suggesting that CSRFA were inert in the rumen. A slight decrease in ammonia concentration in the rumen fluid from the CSRFA:SBM diet and the degradability data do not confirm the protection of SBM protein by CSRFA. Treatments did not affect apparent OM digestibility in the rumen, total N and NAN (non-ammonia nitrogen) flow into the duodenum or microbial protein synthesis. However, rumen degradability of protein was increased by feeding CSRFA. Feeding CSRFA significantly increased the duodenal flows of C18:0, C18:1 and total FA, but when expressed as a percentage of intake, there were no significant treatment differences. The average duodenal flow of total FA was 81.7% of intake. Extents of biohydrogenation of unsaturated FA were decreased in diets containing CSRFA. Estimated net biohydrogenation of C18:2, C18:3 and total unsaturated C18 FA of CSRFA was 43.3, 60.4 and 59.4%, respectively. Postrumen and total tract digestibility of total and individual FA were not different between treatments     

The effect of the source of nitrogen supplementation on nitrogen balance,rates of plasma leucine turnover,protein synthesis and degradation in sheep

Combined experiments of the isotope dilution method of [1-¹³C]leucine, open-circuit calorimetry and nitrogen (N) balance test were used to determine the effect of the source of N supplementation on N balance, whole body protein synthesis (WBPS) and degradation (WBPD) in sheep. The experiment was performed in a replicated 3 × 3 Latin square design. The control diet consisted of timothy hay, ground maize and soybean meal. The urea diet was the control diet supplemented with 1.5% urea. The SBM diet contained the same N and metabolisable energy as the urea diet, which was reached by changing ground maize and soybean meal weights of the control diet. Nitrogen retention was greater (p < 0.05) for the urea diet than the control and SBM diets. Plasma urea concentrations were highest for the SBM diet, followed by the urea diet, and the control diet was lowest. The WBPS and WBPD did not differ between diets, but were numerically lower for the urea and SBM diets. These results suggest that in sheep, urea supplementation influenced N retention without clear changes in WBPS and WBPD.     

Significance of quality of truly digestible protein on performance of ewes at late pregnancy and early lactation

Two trials were conducted in ewes at late pregnancy and early lactation in order to evaluate the effects of substituting the moderate degradable protein of soy bean (SBM), with a low degradable protein of corn gluten meal (CGM), accordingly that both diets were calculated to provide equal truly digestible protein (PDI). At the first trial thirty multiparous ewes were examined in an 8-week study that started at parturition. Animals were fed in groups (15 ewes), with two isocaloric-isonitrogenous-isofibrous rations. Treatments were: (A) SBM, (B) CGM. Diets were different at PDIA/PDI ratio (0.52 versus 0.63). The second trial lasted 7 weeks, 5 weeks pre partum till 2 weeks post partum. Three rations were tested by the use of 48 pregnant ewes. Ewes were allotted to three equivalent groups: (A) SBM and wheat bran, (B) CGM and corn gluten feed, (C) CGM and corn gluten feed plus additional lysine (CGML). Data from both trials were analyzed as repeated measures. CGM compared to SBM decreased milk yield and fat corrected milk (FCM) yield (2.25 and 1.98 kg of milk; 2.47 and 2.17 kg of FCM), while tended to decrease milk's protein content (5.45 and 5.36%, for the SBM and CGM group). The daily production of fat, protein and lactose were higher in SBM than in CGM. CGM ration decreased body weight (BW) gain of ewes during late pregnancy and mean birth BW of litter, and also caused a 30% increase of abortions-dead births. CGM cannot totally replace SBM, in ewes’ diets at early lactation, because of the decrease in milk yield as well as the milk's protein content, even when equal PDI is provided, due to low lysine content. This trial has extended the knowledge from cattle, that supplementation of lysine, usually the first limiting amino acid, is also crucial in ewes during pregnancy and lactation.     

四种植物蛋白对中华绒螯蟹幼蟹生长性能、氨基酸沉积率和抗氧化酶活性的影响

为了筛选适宜于养殖中华绒螯蟹幼蟹的饲料植物蛋白源,探究不同植物蛋白源饲料对幼蟹生长性能、氨基酸沉积率和抗氧化性能等方面的影响,以50%的鱼粉配制基础饲料（记为FM）,分别采用30.5%发酵豆粕、32.5%豆粕、28%棉粕和39%菜粕替代基础饲料中鱼粉总量的50%,配制成4种等氮等能的饲料（分别记为FSBM、SBM、CSM和RSM）,投喂初始体重为（0.249±0.003）g的中华绒螯蟹幼蟹8周。结果表明:（1）与FM组相比,FSBM、SBM和CSM组的增重率、特定生长率、饲料系数、蛋白质效率和蛋白质沉积率均没有显著性差异;RSM组的增重率与FM组相比差异不显著（P>0.05）,但显著低于SBM组（P < 0.05）,而其饲料系数则显著高于FM、FSBM及SBM组（P < 0.05）,蛋白质效率显著低于其他各组（P < 0.05）,蛋白质沉积率显著低于SBM和CSM组（P < 0.05）。（2）不同植物蛋白组的总必需氨基酸沉积率和FM组相比差异不显著（P>0.05）,而RSM组总必需氨基酸沉积率显著低于FSBM和CSM组（P < 0.05）。（3）与FM组相比,不同植物蛋白组蟹的血清和肝胰腺中超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-PX）活性和肝胰腺丙二醛（MDA）含量并没有显著的影响,而RSM组血清丙二醛（MDA）含量显著的高于其他各组（P < 0.05）。结果表明,在幼蟹饲料中,豆粕、发酵豆粕和棉粕替代基础配方中鱼粉的50%后并未对幼蟹的生长性能、氨基酸沉积率及抗氧化能力造成负面的影响,发酵豆粕、豆粕和棉粕可以作为替代鱼粉的适宜蛋白源,且添加水平约在30%左右。菜粕替代后降低了饲料的利用和氨基酸沉积效率,这可能是由于菜粕的蛋白质消化率低、含有相应的抗营养因子和添加水平过高所致,建议使用前应适当进行脱毒处理,并与或和其他植物蛋白配伍使用。