Body protein losses estimated by nitrogen balance and potassium-40 counting

Body protein losses estimated from N balance were compared with those estimated by 40K counting. Six nonlactating dairy cows were fed an adequate N diet for 7 wk, a low N diet for 9 wk, and a replete N diet for 3 wk. The low N diet contained high cell wall grass hay plus ground corn, starch, and molasses. Soybean meal was added to the low N diet to increase N in the adequate N and replete N diets. Intake was measured daily. Digestibilities, N balance, and body composition (estimated by 40K counting) were determined during each dietary regimen. During low N treatment, hay dry matter intake declined 2 kg/d, and supplement increased about .5 kg/d. Dry matter digestibility was not altered by N treatment. Protein and acid detergent fiber digestibilities decreased from 40 and 36% during adequate N to 20 and 2%, respectively, during low N. Fecal and urinary N also declined when cows were fed the low N diet. By the end of repletion, total intake, fiber, and protein digestibilities as well as N partition were similar to or exceeded those during adequate N intake. Body protein (N) loss was estimated by N balance to be about 3 kg compared with 8 kg by 40K counting. Body fat losses (32 kg) were large because of low energy digestibility and intake. Seven kilograms of body fat were regained during repletion, but there was no change in body protein.     

Influence of dry matter and nitrogen intakes on fecal nitrogen losses in cattle.

Dietary factors influencing loss of fecal nitrogen in Holstein steers have been examined in data on metabolism from forage diets. Two factors- total nitrogen and dry matter intake, accounted for a large part of the variation in fecal nitrogen. Nitrogen intak expressed as grams per kilogram dry matter intake more accurately accounted for variability in total fecal nitrogen than did nitrogen intake expressed as grams per animal per day. Data were from trials on 68 forages covering a range of nitrogen intakes and of nitrogen concentration in dry matter of forage. Correlations were .93 between total fecal nitrogen and dry matter intake, .90 between total fecal nitrogen and total nitrogen intake, and .95 between total fecal nitrogen and total fecal dry matter. However, at high and low nitrogen intake there was evidence of departure from a linear relationship. The relative usefulness of three regression analyses to estimate metabolic fecal nitrogen is discussed.     

Excretion of carbohydrates by rats fed legume seeds

A study of sugars excretion in rats after feeding with diets containing various raffinose content (0, 4, 8 and 12%) and cooked leguminous seeds (soybean, peas and beans) has been performed. It was noted, that feeding with raffinose-containing diet has no effect on sugars level in urine during 10 days of experiment. Feeding with the diets containing 8 and 12% raffinose caused highly increased excretion of this sugar and its metabolites in faeces after first 24 h. After next few days of experiment in despite of high raffinose content in diets the level of raffinose excretion in the faeces came back to the initial one. In the case of leguminous seeds feeding of rats increased excretion of sugars in faeces was observed also after 20-24 h, and was maintained on the same level during 10 days of experiment. The ratio of excreted to consumed sugars was limited to 2-5% only. It is presumed that there were stachyose and verbascose metabolites, previously identified in leguminous seeds.     

Splanchnic and mammary nitrogen metabolism by dairy cows fed steam-rolled or steam-flaked corn

Objectives were to determine net release or uptake of a-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 6; 109 +/- 9 d in milk) fed alfalfa hay-based total mixed rations (TMR) containing 40% steam-rolled or steam-flaked corn grain. The TMR were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and mesenteric or costo abdominal arteries, every 2 h for each cow and diet. Steam-flaked compared with steam-rolled corn greatly increased in vitro starch hydrolysis (56 vs. 34%). Daily intake of dry matter (18.4 +/- 0.4 kg/d), starch, N, and net energy for lactation by cows were not altered by processing corn; neither were daily yield of milk (29.1 +/- 0.7 kg/d), fat-corrected milk, nor fat-corrected milk per dry matter intake. Steam-flaking tended to increase percent milk protein (2.97 vs. 2.82%; P = 0.07), but not yield, and decrease percent lactose (4.83 vs. 4.94) but not yield. Portal and hepatic blood flows were not affected by diet, nor were net absorption of alpha-amino N and ammonia N. Steam-flaking compared with steam-rolling increased urea N cycling to portal-drained viscera (212 vs. 87 g/d) by 140%, estimated mammary uptake and extraction ratio of alpha-amino N. Flaking versus rolling of corn improved N utilization in dairy cows by increasing urea cycling to the gut and uptake of a-amino N by the mammary gland. Higher mammary uptake of alpha-amino N (78 vs. 50 g/d) by dairy cows fed steam-flaked corn tended to increase milk protein content and may explain the previously observed effects of cows fed steam-flaked versus steam-rolled corn.     

利用压缩氮气降低液态奶生产中管道损耗的探讨

为解决液态奶生产规模日益增大，生产管线越来越长，造成生产中较大损耗的问题，研究了实际生产中使用的各种介质，并提出了具体设计方案，结果表明，使用压缩氮气代替水可达到产品损耗降低。当管道中压力达到0．3MPa时，管道里的酸奶基本被顶完，方案实施的1年中，产品得率从96．5％提高到97．8％，同时增强了质量稳定性，稳定产品理化指标的目的，该方案实施投入费用的2000元，每天消耗氮气价值约30－90元。     

利用压缩氮气降低液态奶生产中管厘损耗的探讨

为解决液态奶生产规模日益增大,生产管线越来越长,造成生产中较大损耗的问题,研究了实际生产中使用的各种介质,并提出了具体设计方案,结果表明,使用压缩氮气代替水可达到产品损耗降低,当管道中压力达到0.3 MPa时,管道里的酸奶基本被顶完,方案实施的1年中,产品得率从96.5%提高到97.8%,同时增强了质量稳定性,稳定产品理化指标的目的,该方案实施投入费用约2000元,每天消耗氮气价值约30～90元.     

Splanchnic and mammary nitrogen metabolism by dairy cows fed dry-rolled or steam-flaked sorghum grain

Objectives were to determine net release or uptake of alpha-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 8, 86 +/- 8 d in milk) fed alfalfa hay-based total mixed rations containing 40% dry-rolled or steam-flaked sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in the portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries, every 2 h for each cow and diet. Steam-flaking increased in vitro rate of starch hydrolysis compared with dry-rolled sorghum (66 vs. 25%). Diet did not alter dry matter intake (18.2 +/- 0.3 kg). Daily milk yield (27.6 +/- 0.8 kg), efficiency of production, and most milk components did not differ between diets, but fat yield was reduced (0.86 vs. 0.91 kg/d) by steam-flaked sorghum, and lactose concentration was increased (4.99 vs. 4.82%). Blood flows in portal and hepatic veins did not differ between diets. Steam-flaking tended to increase urea N cycling to the gut (162 vs. 95 g/d) compared with dry-rolling of sorghum, whereas net absorption of ammonia N and alpha-amino N across portal-drained viscera were decreased. Net mammary uptake of a-amino N increased more than 20% (83 vs. 67 g/d), resulting in a higher mammary extraction ratio (15 vs. 11%) for steam-flaked versus dry-rolled sorghum. Flaking of sorghum improved the efficiency of postabsorptive N metabolism by increasing urea N cycled to the gut and alpha-amino N uptake by the mammary gland.     

Lower pregnancy losses in lactating dairy cows fed a diet enriched in alpha-linolenic acid

The objectives were to determine if a diet enriched in α-linolenic acid (ALA) would influence ovarian function, early embryo survival, conception rates, and pregnancy losses in lactating dairy cows. Beginning 28 d before breeding, Holstein cows (55 ± 22 d postpartum; mean ± SD) were assigned to diets supplemented with either rolled flaxseed (FLAX; 56.7% ALA, n = 62) or rolled sunflower seed (SUNF; 0.1% ALA, n = 59) to provide approximately 750 g of oil/d. Diets continued for 32 d after timed artificial insemination (TAI, d 0) following a Presynch/Ovsynch protocol. Barley silage- and barley grain-based TMR were formulated to meet or exceed National Research Council requirements. Metabolizable protein and net energy for lactation concentrations were similar in the 2 diets. Based upon a mean dry matter intake of 22 kg/d, cows fed FLAX or SUNF consumed > 410 g or < 1 g of ALA, respectively. Pregnancy was confirmed by ultrasound 32 d after TAI. Nonpregnant cows were placed on a second Ovsynch regimen and reinseminated 42 d after first TAI, and received oilseeds for 32 d after second TAI. Relative to prediet levels, FLAX increased the ALA content of milk by 187%. Ovarian ultrasonography was performed in 8 cows per diet; the mean diameter of ovulatory follicles was larger in cows fed FLAX compared with SUNF (16.9 ± 0.9 vs. 14.1 ± 0.9 mm), but follicle number, corpus luteum size, and plasma progesterone concentrations remained unaffected. Presumptive conception (progesterone < 1 ng/mL on d 0 and > 1 ng/mL on d 21) rates to first TAI were greater in FLAX than in SUNF (72.6 vs. 47.5%). Pregnancy losses were lower in cows fed FLAX (9.8%) compared with those fed SUNF (27.3%). Including flaxseed in the ration of dairy cows increased the size of the ovulatory follicle and reduced pregnancy losses.     

文冠果油对SD孕鼠毒性和胎鼠致畸性研究

研究文冠果油对SD孕鼠的毒性和胎鼠致畸性。以花生油为阴性对照,环磷酰胺为阳性对照,文冠果油0.92、1.83、3.67 g/kg为低、中、高剂量组,灌胃SD受孕大鼠,解剖观察孕鼠胚胎毒性指标和胎鼠生长发育指标,分析文冠果油对胎鼠外观畸形、骨骼发育和内脏、脑系统发育的影响。结果表明：文冠果油各剂量组孕鼠饮食、活动正常,未出现中毒特征。与阴性对照组相比,各剂量组孕鼠的体重没有受到影响,体重增重、子宫连胎重、体重净增重、黄体数、着床数、活胎数、吸收胎数、死胎数均无显著性差异（P＞0.05）;各剂量组胎鼠的体重、体长、外观畸形率、骨骼发育畸形率和内脏、脑系统发育畸形率也没有显著性差异（P＞0.05）。文冠果油未观察到有害作用剂量(NOAEL)为3.67 g/kg,对SD大鼠未见明显母体毒性、胚胎毒性和致畸性。     

Utilization and partition of dietary nitrogen in dairy cows fed grass silage-based diets

Data from 207 production trials (998 treatment means) were used to study the effects of animal and dietary characteristics on the efficiency of N utilization for milk protein production, and on fecal N, urinary N, and total manure N output. The average efficiency of transferring dietary N to milk N (MNE; milk N/N intake) was 277 (SD = 36.0) g/kg. Nitrogen efficiency was poorly related to milk yield. Dietary concentrations of crude protein (CP) and protein balance in the rumen (PBV) were the best single predictors of MNE. Dietary CP concentration explained variation in MNE better than did N intake. Bivariate models with PBV or metabolizable protein (MP) explained the variation better than CP alone. The effects of protein feeding parameters on MNE were consistent among data subsets from studies investigating the effects of the amount and protein concentration of concentrate supplement, silage digestibility, silage fermentation quality, or substitution of grass silage with legume silage. The model with total dry matter and N intakes as independent variables explained fecal, urinary, and total manure N output more precisely than N intake alone. The model of fecal N output suggested that the true digestibility of dietary N was 0.91, and that metabolic and endogenous N was the major component in fecal N. The proportion of urine N in manure N was strongly related to dietary CP concentration. Including the concentration of dietary carbohydrates only slightly improved the models, indicating that the most effective strategy to improve MNE and to decrease N losses in manure, especially in urine, is to avoid feeding diets with excessively high CP concentration and especially excess ruminally degradable CP.     

Reducing gaseous losses of nitrogen from cattle slurry applied to grassland by the use of additives

Losses of nitrogen (N) through ammonia (NH₃) volatilisation and denitrification were determined following the application of cattle slurry to grassland in autumn or spring. Denitrification was examined on two contrasting soils. A system of small wind tunnels was used to measure NH₃ loss and an acetylene inhibition technique for denitrification. Between 31 and 84% of the ammonium N (NH-N) applied in slurry was lost through NH₃ volatilisation. Acidifying the slurry to pH c 5.5 prior to application reduced these losses to between 14 and 57%. On a freely drained loam soil, denitrification from unacidified slurry applied in the autumn at 80 m³ ha^?1 was continuous throughout the winter, with the maximum rate of 0.91 kg N ha^?1 day^?1 occurring a few weeks after slurry application. The total denitrification losses were equivalent to about 29% of the NH-N applied for this treatment and 41% for the acidified slurry. The nitrification inhibitor dicyandiamide reduced the amount of N lost through denitrification by 70% when applied with the slurry at 25 kg ha^?1, by 55% at 20 kg ha^?1 and by 30% at 15 kg ha^?1. The nitrification inhibitor nitrapyrin did not appreciably reduce denitrification. Denitrification losses were consistently small from slurry applied to the freely drained loam soil in spring, or to a poorly drained, silty clay in autumn or spring. Neither nitrification inhibitor was of benefit in these situations.     

The effect of feeding regimen on apparent and true ileal nitrogen digestibility for rats fed diets containing different sources of protein

A standard protocol is required for carrying out routine ileal nitrogen (N) digestibility rat bioassays. The aim of this study was to determine the effects of feeding regimen on ileal N digestibility in rats fed diets containing different protein sources and chromic oxide as an indigestible marker. The experimental design was seven diets (protein‐free (PF), enzyme‐hydrolysed casein (EHC), lactalbumin (LAC), wheat gluten (GLU), fish fillets (FIS), soy protein isolate (SOY), zein) by three feeding regimens (frequent, meal, ad libitum) with 10 rats per diet. In frequent feeding, food was provided for eight 10 min periods between 09:00 and 16:00; in meal feeding, food was provided for one 3 h period at 09:00; in ad libitum feeding, food was available at all times. Rats were fed for 8 days, killed and digesta were collected from the terminal 20 cm of the ileum. The diets and freeze‐dried digesta were then analysed for N and chromium (Cr). There were statistically significant effects of feeding regimen on ileal digesta weight, ileal N/Cr ratio and apparent (AND) and true (PF TND, EHC TND) N digestibility. Mean N digestibilities, averaged over four dietary treatments (LAC, GLU, FIS, SOY), for the frequent, meal and ad libitum feeding regimens respectively were: AND, 88.8, 90.4, 85.8; PF TND, 94.9, 96.4, 97.0; EHC TND, 92.7, 94.0, 95.6. Although the N digestibilities were higher for rats on meal feeding compared with frequent feeding, the only statistically significant differences were for the lactalbumin treatment, and these were small in absolute terms. This study demonstrated that meal feeding was suitable and frequent feeding was unnecessary for most protein sources tested, and that ad libitum feeding was not ideal because of the smaller and more variable quantities of digesta collected and the more variable ileal N/Cr ratios. © 2002 Society of Chemical Industry     

Increased concentrations of liver cholesterol in rats fed lactulose

The disaccharide lactulose (beta-D-galactopyranosyl-(1-4)-D-fructofuranose) is thought to be poorly hydrolized by intestinal enzymes but is broken down by microorganisms in the colon. Thus lactulose shares with pectin similar characteristics. Lactulose is used in the food industry and in the treatment of constipation. There is preliminary evidence that dietary lactulose (5%, w/w) causes increased concentrations of serum and liver cholesterol in rats when compared with pectin. This paper describes dose-response relationships between dietary lactulose and cholesterol in either serum or liver.     

Nitrogen balance in rats fed rices differing in protein content

Nitrogen balance was studied in rats fed seven milled rice samples with 1.10 to 2.73% N dry basis. True digestibility (t.d.) of the protein ranged from 94.4 to 100.1%, biological value (b.v.) ranged from 67.9 to 75.2% and net protein utilisation (n.p.u.) from 64.2 to 75.3%. T.d. and n.p.u. were positively correlated with lysine content of rice protein (3.17 to 4.07 g/16 g of N). Utilisable N ranged from 0.83 to 1.81% and was mainly determined by N content of milled rice (r = 0.988**). A sample of brown rice had lower t.d. but higher b.v. than the corresponding milled rice. Digestibility of amino acids of milled rice protein by fae al analysis ranged from 94.1 to 100.0% in samples with 1.38 and 2.74% N dry basis.     

Effect of dietary concentrate on rumen fermentation, digestibility, and nitrogen losses in dairy cows

The objective of this experiment was to investigate the effect of level of dietary concentrate on rumen fermentation, digestibility, and N losses in lactating dairy cows. The experiment was a replicated 3 × 3 Latin square design with 6 cows and 16-d adaptation periods. Ruminal contents were exchanged between cows at the beginning of each adaptation period. Data for 2 of the diets tested in this experiment are presented here. The diets contained (dry matter basis): 52% (LowC; control) and 72% (HighC) concentrate feeds. Crude protein contents of the diets were 16.5 and 16.4%, respectively. The HighC diet decreased ruminal pH and ammonia concentration and increased propionate concentration compared with LowC. Acetate:propionate ratio was greater for LowC than for HighC. Rumen methane production and microbial protein synthesis were unaffected by diet. Dry matter intake was similar among diets, but milk yield was increased by HighC compared with LowC (36.0 and 33.2 kg/d, respectively). Milk fat percentage and yield and total-tract apparent NDF digestibility were decreased by HighC compared with LowC. More ruminal ammonia N was transferred into milk protein with HighC than with LowC. Urinary N excretion, plasma urea N, and milk urea N concentration were not affected by diet. The ammonia emitting potential of manure was similar between LowC and HighC diets. Increased concentrate proportion in the diet of dairy cows resulted in reduced ruminal ammonia concentration and enhanced ammonia utilization for milk protein synthesis. These effects, however, did not result in reduced urinary N losses and only marginally improved milk N efficiency. Increasing dietary concentrate was not a successful strategy to mitigate enteric methane production and ammonia emissions from manure.     

Analysis of caecal microbiota in rats fed with genetically modified rice by real-time quantitative PCR

The effect of genetically modified rice (GMR) on bacterial communities in caecal content was analyzed in a 90-d feeding rat model. A total of 12 groups of rats, which included male and female, were fed with the basal diets containing 30%, 50%, 70% GMR (B(1), B(2), B(3)) or 30%, 50%, 70% non-GMR (D(1), D(2), D(3)). The structure of intestinal microflora was estimated by real-time quantitative PCR (RQ-PCR) based on genus-specific 16s rDNA primers. SYBR Green was used for accurate detection and quantification of 6 kinds of major bacteria shared by humans and rats. According to RQ-PCR, the genome copies of Lactobacillus group from the cecum of male rats fed with 70% non-GMR was higher than those fed with 70% GMR and the relative abundance of Lactobacillus group also higher for group D. This result was in contrast with the E. coli subgroup, which was more numerous in proportion of group B, except D(2) and B(2) for male rats. The Clostridium perfringens subgroup was numerically more abundant in group D than group B of the same level, also except D(2) and B(2) for male rats. These results suggested that GMR had a complex effect on caecal microflora that may be related to the health of the host.