Human Milk Banking: Influence of Different Pasteurization Temperatures on Levels of Protein Sulfur Amino Acids and Some Free Amino Acids

Human milk is frequently heat‐treated in hospitals, particularly milk that is banked, to destroy contaminating bacteria and viruses, but this treatment simultaneously reduces the content of some vitamins, enzymes, and immunological and nutritional factors. This study was performed to find the optimal conditions for heat treatment. The effects of 2 pasteurization temperatures on levels of protein sulfur amino acids (methionine, cystine) and some free amino acids (taurine, glutamine, glutamic acid) in light of the oxidative instability that occurs especially during thermal treatment were examined. These substances in raw human milk and in milk treated at 56.5 °C and 62.5 °C for 30 min were compared. Samples of mature human milk from all feeds over 24 h were obtained from 13 healthy well‐nourished mothers of term infants. Each sample was divided into 3 parts: raw, treated at 56.5 °C for 30 min, treated at 62.5 °C for 30 min. The results showed that the availability of sulfur amino acids and free taurine is the same after heat treatment, whereas milk processing increased positively the levels of free glutamic acid and glutamine, but there is significance only for glutamine. The mean quantities of considered amino acids were similar in milk treated at the recommended pasteurization temperature (30 min at 62.5 °C) and at 56.5 ° for 30 min.     

Effects of dietary protein degradability and casein or amino acid infusions on production and plasma amino acids in dairy cows

Responses to daily abomasal infusions of 400 g sodium caseinate, 400 g hydrolyzed casein, or 11.3 g L-methionine plus 30.1 g L-lysine were compared in eight Holstein cows fed diets with estimated ruminal protein degradabilities of 70 and 60.%. Basal diets contained corn silage and corn with either soybean meal or 66.7:33.3 soybean meal:corn gluten meal added. Infusion with Methionine plus lysine increased milk protein content when cows fed either diet but increased milk fat content and yield only when the soybean meal diet was fed. Sodium caseinate increased milk and milk protein production and decreased milk fat percentage. Concentration of total essential amino acids, branched chain amino acids, and urea cycle amino acids were increased by the infusion of both casein sources. Methionine-lysine infusion increased plasma lysine and taurine, a metabolite of methionine, suggesting that absorbed methionine was extensively metabolized. Results demonstrate an impact of both ruminal degradability of dietary protein and form of infused protein on amino acid nutrition of lactating daily cows.     

Formaldehyde Treated Whey Protein Concentrate for Lactating Dairy Cattle

Four lactating Holstein cows were fed isonitrogenous rations of urea-corn silage and a 15% crude protein pelleted grain ration containing whey protein concentrate (34% protein) either untreated or treated with 1% formaldehyde on a protein basis. The trial design was three periods double reversal with 12 days per period during which milk and digestibility were measured the last 4 days of each period. Apparent nitrogen digestibility (%), productive nitrogen retained (milk plus retained, g/day), and dry matter digestibility were 60.0 and 53.9, 89.0 and 103.8, and 67.4 and 63.2 for cows fed untreated and treated rations. Productive nitrogen as a percent of absorbed was greater for cows fed the formaldehyde treated ration, suggesting more efficient utilization of absorbed nitrogen. Milk production, milk fat percent and yield, and 4% fat-corrected milk were greater for cows fed the treated ration. Milk fatty acid content was similar. Total daily milk nitrogen, true protein nitrogen, and casein nitrogen yields were not significantly higher for the treated ration. No differences in serum urea and rumen ammonia were major. Rumen volatile fatty acids were higher in cows fed the untreated rations at 4 and 6 h postfeeding. Differences in serum concentrations of most individual essential amino acids between tail and mammary blood were greater for cows fed the treated ration.     

福建烟叶游离氨基酸等主要含氮化合物与感官质量的关系

【目的】为明确烟叶游离氨基酸等主要含氮化合物与感官质量的关系。【方法】以烤烟品种云烟87为试验材料,测定不同施氮量和留叶数对初烤烟叶各叶位的烟碱、总氮、蛋白质、20种游离氨基酸含量的影响,通过感官质量评价分析主要含氮化合物与感官质量的关系。【结果】1）不同部位烟叶游离氨基酸总量差异显著,依次为下部叶>上部叶>中部叶;2）简单相关分析表明,总氮、蛋白质、游离氨基酸总量以及非烟碱氮占总氮含量的比例,与感官质量呈极显著的负相关关系;脯氨酸占游离氨基酸总量的比例,与感官质量呈极显著的正相关关系;3）逐步回归分析表明,在烟碱、蛋白质和20种游离氨基酸中,谷氨酸、谷氨酰胺、丙氨酸对感官质量的负面效应大于烟碱、蛋白质以及其它游离氨基酸。4）在8个处理中,施氮量127.5kg/hm2、留叶数14片/株处理的烟叶,非烟碱氮、谷氨酸、谷氨酰胺、丙氨酸含量以及游离氨基酸总量最低,感官质量较好。【结论】控制烟叶非烟碱氮含量,尤其是降低谷氨酸、谷氨酰胺、丙氨酸以及游离氨基酸总量,有利于提高烟叶品质。     

Abalone (Hariltis discus): Seasonal Variations in Chemical Composition and Textural Properties

Seasonal changes in adenosine 5′-triphosphate, total free amino acids, and total oligopeptides in abalone meat were analyzed. Levels were higher in summer and lower in winter. In both seasons, the most abundant free amino acid was taurine followed by arginine, glycine, glutamine, and glutamic acid. The largest peptide-bond amino acid was glutamic acid + glutamine. The collagen content decreased in summer and increased in winter. The breaking stress values of the meat were low in summer and high in winter, indicating that summer abalone would be more tender. Scanning electron microscopy revealed the collagen network was more compact in winter.     

Effect of level of metabolizable protein on milk production and nitrogen utilization in lactating dairy cows

The objective of this study was to investigate the effects of the level of metabolizable protein (MP) on milk production and nitrogen utilization in Chinese Holstein dairy cows. Forty multiparous dairy cows (body weight = 590 kg; days in milk = 135; average milk yield = 30.2 kg/d) were assigned to treatments randomly within groups based on days in milk and milk production. Animals were offered diets with different levels of MP: 8.3% (diet A), 8.9% (diet B), 9.7% (diet C), and 10.4% (diet D) of dry matter. The MP level in diet A was designed to meet the current Chinese National Station of Animal Production and Health guidelines, whereas that in diet D was based on the National Research Council (2001) model. The experiment lasted for 7 wk. Milk yield and milk composition (fat, protein, and lactose) were recorded, and urea nitrogen concentrations in serum, urine, and milk were measured during the experiment. Milk yield and milk protein percentage increased as the MP increased up to 9.7% of dry matter, and then leveled off. Concentrations of nitrogen in urine, serum, and milk increased linearly as the amount of MP was increased, indicating decreased efficiency of nitrogen utilization. Milk lactose percentage and total solids percentage showed no significant differences among the 4 diets. We concluded that the optimal dietary MP level was at 9.6% of dry matter for Chinese Holstein dairy cows producing 30 kg of milk per day.     

Proteolytic and lipolytic changes during the ripening of León raw cow's milk cheese, a Spanish traditional variety

Proteolytic and lipolytic changes were studied throughout ripening of five batches of León cow's milk cheese, a traditional variety made in the north of Spain. Total soluble nitrogen, non-protein nitrogen, oligopeptides nitrogen, amino nitrogen and ammonia nitrogen fractions increased slightly during the ripening process. The final values of these nitrogen fractions indicate that this cheese undergoes a very slight proteolysis as much in extent as in depth. This weak protein degradation is corroborated when the caseins and their degradation products were quantified by electrophoresis. β-Casein stayed practically intact throughout the ripening process and only 10% of α_s-casein became degraded. The content of total free amino acids increased progressively but in a slightly increased way during ripening, reaching final average values of 592 mg (100 g)⁻¹ of total solids. The most abundant free amino acid at the end of ripening was lysine, followed by leucine, glutamic acid, tryptophan, valine and phenylalanine. The acidity index of the fat values increased during ripening by a factor of 4.39. The final values of this parameter are in the range of those observed in other cow's milk cheeses ripened by bacteria. The content in total free fatty acids underwent an increase throughout ripening reaching final average values of 6669 ppm. The most abundant free fatty acid at the end of ripening was oleic acid followed by butyric and palmitic acids. The high content of short-chain fatty acids is outstanding, specially that of butyric acid.     

Supplemental Niacin for Lactating Cows Fed Diets of Natural Protein or Nonprotein Nitrogen

Thirty-two Holstein cows, 16 in early and 16 in midlactation, were assigned to four treatments: 1) soybean meal protein plus niacin; 2) soybean meal without niacin; 3) nonprotein nitrogen plus niacin; and 4) nonprotein nitrogen without niacin. Niacin dose was 6 g per day, and nonprotein nitrogen supplied 20% of total nitrogen for those treatments. Differences between treatments in milk yields were not significant, but milk persistencies tended to be highest for cows in early lactation fed niacin during wk 9 and 10 of treatment. Intakes of dry matter did not differ significantly, but cows fed nonprotein nitrogen without niacin had lowest intakes per 100 kg bodyweight. Differences between treatments in feed utilization, milk composition, bodyweight changes, plasma ammonia, rumen pH, rumen volatile fatty acids, dry matter digestibilities, nitrogen digestibilities, and retained nitrogen were not significant.     

Utilization of Starea, urea, or soybean meal in complete rations for lactating dairy cows.

Three complete rations containing 15.8% of the dry matter as crude protein were compared to a 14.5% crude protein basal ration (dry matter basis) through eight Holstein cows in a replicated 4 times 4 Latin square design. The high protein rations contained supplemental nitrogen totally from soybean meal, urea, or Starea, the latter two providing 16 and 22% of total ration nitrogen, respectively. Concentrations were mixed with wilted alfalfa-bromegrass silage and complete rations fed ad libitum. Data were collected during the last week of each 28 days. Ration had no effect on milk yield, composition of fat or protein, or apparent digestibility of dry matter, crude protein, or acid detergent fiber. Weight gains and dry matter intake were greatest with the soybean meal ration. Intake of the low protein ration was depressed. There were no significant differences between the high protein rations for efficiency of nitrogen utilization.     

Effect of rumen-protected branched-chain amino acid supplementation on production- and energy-related metabolites during the first 35 days in milk in Holstein dairy cows

Essential AA are critical for multiple physiological processes. Branched-chain AA (BCAA) supplementation has beneficial effects on body weight, lipogenesis, and insulin resistance in several species. The BCAA are used for milk and body protein synthesis as well as being oxidized by the tricarboxylic acid cycle to produce ATP during catabolic states. The objective was to evaluate the effect of rumen-protected BCAA (375 g of 27% l-Leu, 85 g of 48% l-Ile, and 91 g of 67% l-Val) with or without propylene glycol (PG) oral administration on milk production, dry matter intake, nonesterified fatty acids, β-hydroxybutyrate, and plasma urea nitrogen during the first 35 d in milk (DIM) in dairy cattle. Multiparous Holstein cows were enrolled in blocks of three 28 d before expected calving and assigned randomly to either the control or 1 of 2 treatments. The control (n = 26) received 200 g/d of dry molasses, the BCAA treatment (n = 23) received BCAA mixed with 200 g/d of dry molasses from calving until 35 DIM, and the BCAA plus PG (BCAAPG) treatment (n = 25) received BCAA mixed with 200 g/d of dry molasses from calving until 35 DIM plus 300 mL of PG once daily from calving until 7 DIM. Postpartum, dry matter intake least squares means (LSM; 95% confidence interval) were 20.7 (19.9, 21.7), 21.3 (20.4, 22.3), and 21.9 (20.9, 22.8) kg for control, BCAA, and BCAAPG, respectively. Milk yield (1–35 DIM) LSM were 41.7 (39.4, 44.0), 42.7 (40.3, 45.0), and 43.7 (41.4, 46.0) kg for control, BCAA, and BCAAPG, respectively. Energy-corrected milk LSM were 50.3 (46.8, 53.7), 52.4 (48.9, 55.8), and 52.9 (49.5, 56.4) kg for control, BCAA, and BCAAPG, respectively. Milk urea nitrogen LSM in milk for control, BCAA, and BCAAPG were 8.60 (8.02, 9.22), 9.70 (9.01, 10.45), and 9.75 (9.08, 10.47) mg/dL. Plasma urea nitrogen concentrations LSM for control, BCAA, and BCAAPG were 8.3 (7.7, 8.9), 10.1 (9.4, 10.9), and 9.6 (9.4, 10.3) mg/dL, respectively. The numbers of plasma samples classified as hyperketonemia were 77, 44, and 57 in control, BCAA, and BCAAPG, respectively. The BCAA supplementation increased plasma urea nitrogen and milk urea nitrogen, free valine concentration in plasma, and decreased hyperketonemia events during the postpartum period.     

Urea on Flaked Soybean Hulls as a Protein Replacement for Dairy Cows

In Experiment I a Latin square design was used to study the utilization of urea nitrogen adsorbed on flaked soybean hulls in normal rations of high producing dairy cows. Concentrates containing urea, urea with supplemental minerals, or soybean meal as the protein supplement were fed with corn silage and alfalfa in a total ration of approximately 17% crude protein. Both urea concentrates contained 2.7% urea. Animals fed urea and soybean had similar milk yields (28.7 and 27.9 kg/day), milk protein, and digestible dry matter intakes. Urea with mineral produced lower milk yield (25.3 kg/day), milk protein, and dry matter intakes, probably because of excessive mineral content. Urea nitrogen of plasma was similar for all three diets. Essential amino acids of plasma were lower for urea than for soybean while for urea mineral the essential amino acids were midway between the other two. In Experiment 2 a switchback design was used to compare the urea-soybean hull concentrate diet of Experiment 1 (17% crude protein) to a negative control diet consisting of its basal components without urea adjusted to 12% protein with wheat bran. Milk yield was 1.2 kg/day higher when the urea diet was fed. Perhaps due to improved urea distribution in the rumen, flaked soybean hulls with urea were effective in maintaining the feed intake necessary for high milk production.     

Varying protein content and nitrogen solubility for pluriparous, lactating Holstein cows: digestive performance during early lactation

Thirty-four pluriparous Holstein cows were used to examine effects of crude protein (15.3 vs. 13.6%, dry matter basis) and nitrogen solubility (39.7 vs. 47.9%) on digestibility, energy and protein balances, and related traits during early lactation. Cows were assigned randomly at parturition to treatments in a 2 X 2 factorial arrangement; measurements were during wk 6, 10, and 14 postpartum. Diets were protein supplements (varying in protein content and nitrogen solubility), low-protein concentrate, corn silage treated with urea at ensiling, and wilted grass silage fed individually for ad libitum intake. Reducing nitrogen solubility of diet improved energy intake and productive energy factors but resulted in no significant increase of milk yield or body tissue balances, although body fat balance tended to be higher for low-solubility diets. There was no effect on overall partition of nitrogen in the body. Digestibility of carbohydrates and protein was higher for 15.3 than for 13.6% crude protein diets, resulting in higher total digestible nutrients and digestible and metabolizable energy of dry matter. Raising crude protein in the ration decreased milk yield of cows in early lactation but generally increased body tissue balances. Concentrations of rumen ammonia and blood urea nitrogen were not influenced by nitrogen solubility; increasing dietary protein increased concentrations of both, although not enough to increase consumption of free water. Best digestive efficiency was for animals fed the ration of medium crude protein and low nitrogen solubility.     

Dietary protein oscillation: Effects on feed intake,lactation performance,and milk nitrogen efficiency in lactating dairy cows

Limited research with growing ruminants indicates that oscillating (OS) dietary crude protein (CP) concentration may improve nitrogen use efficiency (NUE). Our aim was to determine if a total mixed ration (TMR) based on OS CP (48-h phases of 13.4% and 16.5% CP, respectively) would increase NUE of lactating dairy cows compared with a static CP TMR (ST; 14.9% CP). The experiment was a randomized complete block design with 50 cows [150 ± 61 (mean ± SD) d in milk]. Cows were blocked by parity, days in milk, and milk protein yield. On average, diets were equal in composition over the total experiment. Cows were milked twice daily, and 8 milk samples were collected in each 4-d period. Each 48 h of low-CP (LP) and high-CP (HP) TMR offered to OS cows corresponded to milk collected at milkings 1 to 4 and 5 to 8, respectively. Dry matter intake (mean = 25.5 kg/d for both treatment groups); yields of milk (mean = 31.5 kg/d for both treatment groups), protein, fat, lactose, and fat- and protein-corrected milk (mean = 33.6 kg/d for both treatment groups); and milk concentration of protein, fat, and lactose did not differ between treatments. However, milk urea concentration was higher for OS compared with ST (12.2 vs. 11.3 mg/dL). Body weight, body condition score, NUE, and feed efficiency were unaffected by OS. Apparent total-tract digestibility of dry matter (695 vs. 677 g/kg), organic matter (714 vs. 697 g/kg), CP (624 vs. 594 g/kg), neutral detergent fiber (530 vs. 499 g/kg), and starch (976 vs. 973 g/kg) were higher for OS than for ST cows. Cows in OS responded transiently, and regression analysis of differences within block over time revealed changes in yield of milk (−531 g/d), milk protein (−25.6 g/d), and milk lactose (−16.7 g/d) in LP. Opposite effects were observed for yield of milk (+612 g/d), milk protein (+28.8 g/d), and milk lactose (+28.0 g/d) during HP. Changes in concentrations of milk protein (−0.050%/d), lactose (+0.030%/d), and urea (−3.0 mg/dL per day) during LP, and in milk lactose (−0.024%/d) and urea (+4.3 mg/dL per day) during HP, were observed. Milk yield, lactose yield, and protein yield were lower for OS than ST cows at the last milking of LP and at the first milking of HP. Milk urea concentration did not show such a lag and was lower in the last 2 milkings of LP, and higher in the last 3 milkings of HP, in OS compared with ST cows. Overall, performance and NUE were unaffected by OS treatment, but apparent total-tract digestibility and milk urea concentration increased, and transient effects on milk yield and composition occurred in OS cows.     

Effect of active dry yeast on lactation performance,methane production,and ruminal fermentation patterns in early-lactating Holstein cows

This study was conducted to examine the effect of active dry yeast (ADY) supplementation on lactation performance, ruminal fermentation patterns, and CH₄ emissions and to determine an optimal ADY dose. Sixty Holstein dairy cows in early lactation (52 ± 1.2 DIM) were used in a randomized complete design. Cows were blocked by parity (2.1 ± 0.2), milk production (35 ± 4.6 kg/d), and body weight (642 ± 53 kg) and assigned to 1 of 4 treatments. Cows were fed ADY at doses of 0, 10, 20, or 30 g/d per head for 91 d, with 84 d for adaptation and 7 d for sampling. Although dry matter intake was not affected by ADY supplementation, the yield of actual milk, 4% fat-corrected milk, milk fat yield, and feed efficiency increased quadratically with increasing ADY supplementation. Yields of milk protein and lactose increased linearly with increasing ADY doses, whereas milk urea nitrogen concentration and somatic cell count decreased quadratically. Ruminal pH and ammonia concentration were not affected by ADY supplementation, whereas ruminal concentration of total volatile fatty acid increased quadratically. Digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, nonfiber carbohydrate, and crude protein increased quadratically with increasing ADY supplementation. Supplementation of ADY did not affect blood concentration of total protein, triglyceride, aspartate aminotransferase, and alanine aminotransferase, whereas blood urea nitrogen, cholesterol, and nonesterified fatty acid concentrations decreased quadratically with increasing ADY supplementation. Methane production was not affected by ADY supplementation when expressed as grams per day or per kilogram of actual milk yield, dry matter intake, digested organic matter, and digested nonfiber carbohydrate, whereas a trend of linear and quadratic decrease of CH₄ production was observed when expressed as grams per kilogram of fat-corrected milk and digested neutral detergent fiber. In conclusion, feeding ADY to early-lactating cows improved lactation performance by increasing nutrient digestibility. The optimal ADY dose should be 20 g/d per head.     

Relationships between milk urea concentrations and nutritional management, production, and economic variables in Ontario dairy herds

The objectives of this study were to describe the relationships between milk urea concentrations and nutritional management, production, and economic variables in commercial dairy herds. Dairy Herd Improvement (DHI) test-day milk urea data, production data, and information on ration nutrient composition and feeding management programs were collected over a 13-mo period from 53 commercial Ontario dairy herds. Economic variables included gross milk revenue, feed costs, and income over feed costs. Herd mean milk urea concentrations had a positive relationship with dietary levels of crude protein (CP), rumen degradable protein (RDP), and rumen undegradable protein (RUP) and a negative relationship with dietary levels of nonfiber carbohydrates (NFC), forage:concentrate (F:C) ratio, NFC:CP ratio, and NFC:RDP ratio. These findings are consistent with experimental studies that used chemical methods of milk urea analysis. Herd mean milk urea concentration was not associated with feeding management (e.g., total mixed rations, component feeding, feeding frequency, or synchrony of forage and concentrate feeding). Herd mean milk urea was not associated with either mean milk yield or linear score. Herd mean milk urea had a positive relationship with feed costs per cow per day but was not associated with gross milk revenue per cow per day. Herds with a high mean milk urea concentration tended to have lower income over feed costs per cow per day. High herd mean milk urea concentrations were associated with higher feed costs per kilogram of milk fat but lower gross milk revenue and lower income over feed costs per kilogram of milk fat. The results of this study demonstrate that DHI milk urea measurements produced by an infrared test method offer a useful tool for monitoring the efficiency of nitrogen utilization in commercial dairy herds. The results also suggest that diets may be balanced to achieve greater efficiency of nitrogen utilization, lower milk urea concentrations, and lower feed costs, while still achieving high milk production. This may lead to improved income over feed costs.     

Milk production and composition of mid-lactation cows consuming perennial ryegrass-and chicory-based diets

Dry matter intakes (DMI), nutrient selection, and milk production responses of dairy cows grazing 3 herbage-based diets offered at 2 allowances were measured. The 2 allowances were 20 (low) and 30 (high) kg of dry matter (DM)/cow per day and these were applied to 3 herbage types: perennial ryegrass (PRG) and chicory (CHIC+) monocultures and a mixed sward of chicory and perennial ryegrass (MIX). The CHIC+ diet was supplemented with alfalfa hay (approximately 2 kg of DM/cow per day) to maintain dietary neutral detergent fiber (NDF) concentration and all diets were supplemented with energy-based pellets (6 kg of DM/cow per day). Holstein-Friesian dairy cows averaging 136 ± 30 d in milk were allocated to 4 replicates of the 6 treatments using stratified randomization procedures. Cows were adapted to their experimental diets over a 14-d period, with measurements of DMI, milk yield, and composition conducted over the following 10 d. Herbage DMI was lowest (12.8 vs. 14.0 kg of DM/d) for CHIC+ compared with the MIX and PRG, although total forage intake (grazed herbage plus hay) was similar (14.0 to 15.0 kg of DM/d) across the 3 treatments. Milk production, milk protein, and milk fat concentrations were not different between herbage types. Grazed herbage DMI increased with increasing herbage allowance and this was associated with increased milk protein concentration (3.23 to 3.34%) and total casein production (41.7 to 43.6 mg/g). Concentrations of polyunsaturated fatty acids in milk fat, particularly linoleic acid, were increased in milk from cows offered the CHIC+ or the MIX diets, indicating potential benefits of chicory herbage on milk fatty acid concentrations. Although feeding CHIC+ or MIX did not increase milk yield, these herbage types could be used as an alternative to perennial ryegrass pasture in spring.     

Utilization of Amide Nitrogenby the Young Rat

SUMMARY: Effects on body nitrogen gains of supplying nonessential nitrogen as glutamic or aspartic acids, as glutamine or asparagine or as wheat were investigated. It was found that nitrogen gains of rats fed diets containing only purified amino acids as the nitrogen source and relatively high levels of amide nitrogen were significantly lower than those of rats fed the same amounts of total nitrogen, all as α-amino nitrogen. However, they were significanty higher than those of rats fed the same amounts of α-amino nitrogen, but no additional amide nitrogen, indicating some effect of amide nitrogen in body nitrogen storage. Rats fed ad libitum consumed more of the glutamine-containing diet than of one containing isonitrogenous amounts of glutamic acid; analysis of covariante indicated that ad libitum-fed rats also utilized the nitrogen of glutamic acid more efficiently than that of glutamine. Addition of enough sodium bicarbonate to neutralize the hydrochlorides of dietary amino acids had no effect on utilization of amide nitrogen. No differences in nitrogen utilization were found between two groups of rats fed different levels of amide nitrogen as wheat.     

Lactational and Systemic Responses to the Supplementation of Protected Methionine in Soybean Meal Diets

Twenty-seven Holstein cows (14 primiparous and 13 multiparous) were randomly assigned to diets containing soybean meal without or with 15 g of added DL-methionine daily, provided as 50 g of ruminally protected methionine product, during wk 4 through 16 postpartum. Cows were fed a 15.3% crude protein total mixed diet of (dry matter basis) 30% corn silage, 15% alfalfa hay, and 55% concentrate mix. Yields of milk (32.9 and 35.2 kg/d), 4% fat-corrected milk (27.8 and 29.5 kg/d), and solids-corrected milk (28.5 and 30.1 kg/d) were higher for cows fed supplemental methionine. Milk protein percentage (2.99 and 3.06) was increased with supplemental methionine, while the percentage of fat (2.96 and 3.00), solids-not-fat (8.69 and 8.73), and total solids (11.67 and 11.71) were similar among diets. Dry matter intake (19.3 and 21.3 kg/d) was higher with methionine supplementation. Ruminal pH, volatile fatty acids, ammonia, and serum urea were generally unaffected by methionine supplementation. Concentrations of methionine in arterial and venous serum were elevated slightly by methionine supplementation, but the first-limiting amino acid for milk production, as calculated by several methods, was not changed.     

Ripening time estimation of Kariesh cheese

Kariesh cheese is a popular cheese in Egypt produced by acid coagulation of milk. It can be consumed fresh or after ripening. Proteolysis in cheese was measured by determining soluble nitrogen (SN), amino acid nitrogen (AAN), total amino acids (TAA) and free amino acids (FAA). SN, AAN and FAA increased during ripening. Free amino acids profile revealed in total 16 amino acids and the same distribution of free amino acids. Cheese ripening was influenced by the type of milk and the method of production. The mildly acid sweet flavour was attributed to the concentration of glutamic acid, aspartic acid, proline and valine. Linear regression analysis was carried out to estimate the ripening time of this cheese. A positive correlation between the accumulation of amino acid and ripening time was established. The highest coefficient of determination near one resulted from glutamic acid (R² = 0.99) followed by lysine (R² = 0.97–0.99), then aspartic acid (0.90–0.98). From the linear regression equation for glutamic acid, lysine, aspartic acid or proline, the ripening time of Kariesh cheese in weeks was determined as follows: Time of ripening [weeks] = mg amino acid 100 g cheese-a/b where b = slope and a = intercept of regression straight line at 0 time.     

Dilution of Cow's Milk and Egg Proteins with Glutamic Acid and the Effect on the Protein Efficiency Ratio

SUMMARY– The effect of dilution of egg proteins and cow's milk proteins with varying levels of L-glutamic acid (GA) on the growth of young rats and protein efficiency ratio of the blends was studied. Addition of glutamic acid to diets containing 8.5% to 5.0% egg proteins to maintain the nitrogen content of the diet constant at 1.6% (equal to 10% protein) did not cause any increase in the growth rate of rats as compared to that on corresponding diets without added glutamic acid. The protein efficiency ratios progressively decreased from 4.74 for 10% egg protein diet to 2.88 for 5% egg protein + 8.4% glutamic acid diet. Addition of glutamic acid to diets containing 8.5 to 5.0% milk proteins to maintain the nitrogen content of the diet constant at 1.6% level caused a significant decrease in the growth rate as compared to that on corresponding diets without added glutamic acid. The protein efficiency ratios also progressively decreased from 3148 for 10% milk proteins to 1.46 for a mixture of 5% milk proteins + 8.4% glutamic acid. The results show that both egg proteins and milk proteins contain adequate amounts of non-essential amino acids for maximum utilization of essential amino acids present in them for the growth of young rats.