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。     

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.     

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.     

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.     

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.     

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.     

Short communication: Milk urea nitrogen as a predictor of urinary nitrogen and urea nitrogen excretions of late-lactation dairy cows fed nitrogen-limiting diets

Our objectives were to assess the relationships between milk urea N (MUN), serum urea N (SUN), urine N (UN), and urinary urea N (UUN) in late-lactation cows fed N-limiting diets and compare these relationships with those previously established. Data were from a pen-based study in which 128 Holstein cows had been assigned to 1 of 16 pens in a randomized complete block design to assess the effects of diets containing 16.2, 14.4, 13.1, and 11.8% crude protein (CP, dry matter basis) during a 12-wk period. At least half of the cows in each pen were randomly selected to collect pen-level samples of serum and urine in wk 3, 7, and 11, when wk in lactation averaged 35, 39, and 43, respectively. A mixed model was developed to study the relationship of MUN with SUN, UN, and UUN. Week of lactation did not affect the relation between MUN and SUN across dietary treatments. However, we found a week × MUN interaction, suggesting that between wk 35 and 43 of lactation, UN excretion decreased from 89 to 73 g/d (?17 g/d) when MUN was 6.0 mg/dL (11.8% dietary CP) but increased from 142 to 149 g/d (+7 g/d) when MUN was 13.3 mg/dL (16.2% dietary CP). These effects were essentially due to changes in UUN excretion, which declined from 54 to 37 g/d (?17 g/d) and increased from 112 to 117 g/d (+5 g/d) when MUN was 6.0 and 13.3 mg/dL, respectively. When MUN was 11.2 mg/dL (15% dietary CP), UN and UUN excretions remained constant over time. Based on root mean squared prediction error and the concordance correlation coefficient, these data did not conform to most previously published prediction equations because of both mean and slope biases. The discrepancy could have resulted from difference in study design (cow vs. pen as experimental unit), dietary treatments (energy vs. N-limiting diets), frequency of measurement and duration of adaptation period (single measurement after 1 to 3 wk of adaptation vs. repeated measurements over a 12-wk period), method for determining urine volume (total collection vs. spot sampling), and the assay used to measure MUN. However, our data captured changes in kidney physiology that warrant further studies of long-term renal adaptation to N-limiting diets.     

Alleviation of plasma,erythrocyte and liver lipidemic-oxidative stress by thymoquinone and limonene in atherogenic suspension fed rats

In the present study, the antioxidant efficacies of thymoquinone (TQ) and limonene (LMN), two main constituents of Nigella sativa seeds, were investigated in relation to plasma, erythrocyte and liver oxidative abnormalities in hyperlipidemic Wistar albino rats. Pretreatment with 10 mg TQ or 200 mg LMN in atherogenic suspension fed rats, effectively reduced the plasma lipid peroxidation markers, conjugated diene, lipid hydroperoxide, malondialdehyde, and replenished the plasma antioxidant capacity by increasing its ferric reducing ability and 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid quenching to near normal levels and modulating the levels of reduced glutathione, enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, and erythrocyte membrane-linked ATPases to normalcy. These results demonstrate that radical scavenging/antiperoxidative efficacies of TQ were greater than LMN. Thus, these compounds, especially TQ, play an important and useful role in the preservation of plasma antioxidant status, cellular membrane structure and function of tissues, and may be used as chemopreventative food additives in the prooxidant state related disorders.     

Estimation of genetic parameters for predicted nitrogen use efficiency and losses in early lactation of Holstein cows

The objective of this study was to estimate genetic parameters of predicted N use efficiency (PNUE) and N losses (PNL) as proxies of N use and loss for Holstein cows. Furthermore, we have assessed approximate genetic correlations between PNUE, PNL, and dairy production, health, longevity, and conformation traits. These traits are considered important in many countries and are currently evaluated by the International Bull Evaluation Service (Interbull). The values of PNUE and PNL were obtained by using the combined milk mid-infrared (MIR) spectrum, parity, and milk yield–based prediction equations on test-day MIR records with days in milk (DIM) between 5 and 50 d. After editing, the final data set comprised 46,163 records of 21,462 cows from 154 farms in 5 countries. Each trait was divided into primiparous and multiparous (including second to fifth parity) groups. Genetic parameters and breeding values were estimated by using a multitrait (2-trait, 2-parity classes) repeatability model. Herd-year-season of calving, DIM, age of calving, and parity were used as fixed effects. Random effects were defined as parity (within-parity permanent environment), nongenetic cow (across-parity permanent environment), additive genetic animal, and residual effects. The estimated heritability of PNUE and PNL in the first and later parity were 0.13, 0.12, 0.14, and 0.13, and the repeatability values were 0.49, 0.40, 0.55, and 0.43, respectively. The estimated approximate genetic correlations between PNUE and PNL were negative and high (from ?0.89 to ?0.53), whereas the phenotypic correlations were also negative but relatively low (from ?0.45 to ?0.11). At a level of reliability of more than 0.30 for all novel traits, a total of 504 bulls born after 1995 had also publishable Interbull multiple-trait across-country estimated breeding values (EBV). The approximate genetic correlations between PNUE and the other 30 traits of interest, estimated as corrected correlations between EBV of bulls, ranged from ?0.46 (udder depth) to 0.47 (milk yield). Obtained results showed the complex genetic relationship between efficiency, production, and other traits: for instance, more efficient cows seem to give more milk, which is linked to deeper udders, but seem to have lower health, fertility, and longevity. Additionally, the approximate genetic correlations between PNL, lower values representing less loss of N, and the 30 other traits, were from ?0.32 (angularity) to 0.57 (direct calving ease). Even if further research is needed, our results provided preliminary evidence that the PNUE and PNL traits used as proxies could be included in genetic improvement programs in Holstein cows and could help their management.     

Body composition and serum and liver lipids in rats fed distillers' dried grains

This study examined the body composition and serum and liver lipids in weanling rats fed diets containing distillers' dried grains with solubles (DDGS) from either white wheat (WW), red wheat (RW), corn (CO) or WW fortified with essential amino acids (FWW) as a sole protein source (1.6 % N in the diet). Although the DDGS-fed groups had significantly lower body weights compared with the casein control (RC) after a 28-day feeding trial, there were no significant differences among the dietary groups in percentages of body water, protein, lipid or ash. Serum cholesterol was significantly higher in rats fed the RW diet, and serum triglyceride was higher in the RC and FWW groups compared with the other dietary groups. Liver cholesterol and triglyceride concentrations (mg g^?1 liver) were not significantly different among the five dietary groups.     

Endogenous synthesis of cis-9, trans-11 conjugated linoleic acid in dairy cows fed fresh pasture

New Zealand Holstein-Friesian cows (n = 4) were used to quantify the importance of endogenous synthesis of cis-9, trans-11 conjugated linoleic acid (CLA) via Delta(9)-desaturase in cows fed a fresh pasture diet. The experiment was a 4 x 4 Latin square design with treatments arranged in a 2 x 2 factorial. Treatments lasted 4 d and were pasture only, pasture plus sterculic oil, pasture plus sunflower oil, and pasture plus sunflower oil plus sterculic oil. Abomasal infusion of sterculic oil inhibited Delta(9)-desaturase and decreased the concentration of cis-9, trans-11 CLA in milk fat by 70%. Using the changes in cis-9 10:1, cis-9 12:1 and cis-9 14:1 to correct for incomplete inhibition of Delta(9)-desaturase, a minimum estimate of 91% of cis-9, trans-11 CLA in milk fat was produced endogenously in cows fed fresh pasture. Dietary supplementation of a pasture diet with sunflower oil increased the proportion of long chain fatty acids in milk fat; however, the increase in vaccenic acid concentration was small (18%) and there was no increase in cis-9, trans-11 CLA concentration. Overall, results show that endogenous synthesis is responsible for more than 91% of the cis-9, trans-11 CLA secreted in milk fat of cows fed fresh pasture. However, the failure of plant oil supplements to increase the concentration of cis-9, trans-11 CLA in milk fat from pasture-fed cows requires further investigation.