Milk Nitrogen Research Articles

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 = 590kg; days in milk = 135; average milk yield = 30.2kg/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 30kg of milk per day.

Machine milking management and milk nitrogen fractions in primiparous ewes

Little work has been carried out on management techniques to reduce stress of first machine milking in ewes. The aim of this work was to evaluate the effect of milking parlour training before weaning on sheep milk yield and milk protein fractions. One week before weaning, an experimental group (EG) was introduced into the machine milking parlour and hand-milked once a day, to adapt them to the new environment and noise of the milking machine, while a control group (CG) was hand-milked once a day in a traditional fold parlour until weaning. After weaning, both groups were machine milked, separately, twice a day in the milking parlour. Milk yield and nitrogen fractions were recorded for the first 10 days of machine milking. Differences between samplings within group were observed for all parameters considered. Only on the first day of machine milking, differences between groups occurred for total nitrogen, total protein and casein. Higher content of nitrogen fractions in the milk of EG was due to its lower milk production. In fact, daily production of nitrogen fractions was higher in CG than in EG. High variability for most parameters was observed during the first 5 days of machine milking in both groups. A week of training to machine milking parlour was not enough to reduce the negative effects of weaning and machine milking stresses on primiparous ewes. (interaction?)

Application of a Coagulating Preparation Obtained with Rhizomucor Miehei N in Cheese-Making

Studies were carried out to determine the suitability of a coagulating preparation, Rhizomucor proteinase, obtained from Rhizomucor miehei for production of Camembert, Edam and Cheddar cheeses. While analyzing the cheese-making process, it was found that the obtained preparation could be used in the production of high quality cheeses without the need for changing the established technological parameters. In cheeses produced with Rhizomucor proteinase, proteolysis and lipolysis was more intense than in renin cheeses - whi ch has a beneficial effect on cheese sensory properties. Lower utilization of milk nitrogen compounds and fat encourages further studies into the application of the obtained preparation in combination with other coagulating enzymes.

Concentrações de nitrogênio na dieta, no sangue e no leite de vacas lactantes no período pós-parto

Foram utilizadas 24 vacas leiteiras em um delineamento em blocos casualizados com o objetivo de comparar três tratamentos compostos por dietas isoenergéticas, distintas quanto aos teores de proteína bruta (PB): P100 = 100%, P130 = 133% e P166 = 166% das exigências descritas pelo NRC (1989). Os acréscimos de PB foram obtidos como equivalentes protéicos mediante adição de uréia pecuária. Semanalmente, coletaram-se amostras dos alimentos, do leite e do sangue dos animais, desde os 30 dias anteriores até os 60 posteriores ao parto. As produções de leite e o peso das vacas foram registrados semanalmente. As concentrações de nitrogênio uréico foram determinadas nas amostras de leite (NUL) e de plasma (NUP). As produções médias de leite, por vaca e por dia, foram iguais a 12,4; 13,3; e 13,4 kg nos tratamentos P100, P133 e P166, respectivamente, aumentando de forma linear com o emprego de maiores quantidades de equivalente protéico nas rações. As concentrações de NUP e NUL, em mg/dL, aumentaram linearmente com o incremento de equivalente protéico nas dietas, segundo as equações Y= 16,83 + 0,202 X e Y= 13,73 + 0,219 X, respectivamente. A correlação entre valores de NUP e NUL foi significativa, indicando que tanto os valores de NUP quanto os de NUL podem servir como indicadores das quantidades dietéticas de proteína degradável no rúmen, em vacas lactantes, e que valores mais elevados de equivalente em PB resultam em maiores produções de leite.

Incremento en la proteína no degradable en rumen de vacas lecheras: 2. Efectos sobre utilización y excreción del nitrógeno

SUMMARY Eight confined lactating cows at mid lactation fed diets based on silages were used in an incomplete Latin square design to evaluate the effects of increasing rumen undegradable protein (RUP) on nitrogen utilization and excretion. Four diets were used. Diets designed as A1 and B1 had, on a DM basis, 45% pasture silage and 20% alfalfa haylage, while diets A2 and B2 had 38% permanent pasture and 27% alfalfa silage. Diets A and B differed mainly on the level of RUP. Diets A were formulated accepting up to a 20% RUP deficit and included soybean meal, while B diets covered 100% of estimated RUP requirements, using fish meal as a protein source. In spite of causing a lower N intake (P < 0.05), diets higher in RUP (B diets) resulted in similar milk production. Productive N (secreted as milk nitrogen plus N in daily gain, expressed as g day–1 and as g kg–1 of N intake) was improved significantly (P < 0.05) in higher RUP diets. Faecal and urinary N excretion were also lower (P < 0.05 and P < 0.01, respectively) in these diets. Intake N used in productive functions was higher in B diets (P < 0.01). The relationship productive N v/s intake N and excreted N (faeces plus urine) per litre of milk produced, and productive N v/s excreted N were all improved with B diets. These data indicate that correcting a RUP deficit of high silage diets with fish meal, increased the efficiency of the use of N for productive functions and decreased potential contamination through a reduced N excretion.

Effects of pre‐feeding of a corn silage‐based supplement on the feed intake, milk production and nitrogen utilization of grazing dairy cows

ABSTRACTFour Holstein cows were used to determine the effect of timing of the feeding of a corn silage (CS)‐based supplement on the feed intake, milk production and nitrogen utilization of grazing dairy cows. The cows were fed the supplement 2 h before grazing (pre‐grazing) or immediately after grazing (post‐grazing). Cows were grazed for 5 h per day under a rotational grazing system. There was no difference in the herbage and total feed intake between treatments. The milk protein yield for pre‐grazing tended to be higher than that for post‐grazing, whereas the milk yield did not differ between treatments. The total nitrogen intake for pre‐grazing tended to be higher than that for post‐grazing (P = 0.06). There was no difference in the urinary nitrogen output between treatments, whereas the proportion of urinary nitrogen output : total nitrogen intake for pre‐grazing tended to be lower than that for post‐grazing (P = 0.06). The milk nitrogen output and nitrogen retention for pre‐grazing tended to be higher than that for post‐grazing (milk nitrogen, P = 0.06; nitrogen retention, P = 0.05). Nitrogen utilization of grazing dairy cows was improved by feeding a CS‐based supplement before grazing.

Mare milk nitrogen fractions during lactation and determination by reversed-phase HPLC of the major whey proteins

The aim of this research was to describe the changes of the nitrogen fractions in milk of Haflinger nursing mares and in particular to determine the whey protein content and distribution, and their evolution throughout the first 6 mo of lactation. Samples were collected by hand-milking on days 4, 20, 40, 60, 80, 120, 150 and 180 post-partum. Nitrogen fractions were determined by Kjeldahl on 80 samples from 10 mares, while HPLC separation of whey proteins was conducted on 40 samples from 5 mares. The total N, casein N, and true whey protein N contents showed a statistically significant decrease from day 4 to day 40, and then remained unvaried. In general, the nitrogen distribution of mare’s milk significantly changed between day 4 and day 20 and then remained almost unchanged until day 180 (except for the day 150 value, which showed a statistically significant increase for CN × 100/TN). β-Lactoglobulin and serum albumin contents showed a marked reduction, of 27 and 45.5%, respectively, between day 4 and day 20, and then remained unchanged; α-lactalbumin and immunoglobulins contents had a reduction of 24.7 and 38.3%, respectively, between day 4 and day 20, and another decrease between day 20 and day 40, of 20 and 32.8%, respectively. All whey proteins, expressed as a percentage on the total sum of the four whey proteins considered, did not vary significantly during lactation. However, the sum on the two whey proteins of mammary gland origin (β-Lg + α-La) increased between day 4 and day 20 by 6.3%, and between day 20 and day 40 by 3.8%; the sum of the whey proteins of blood origin (SA + Ig) showed an opposite trend, with a decrease by 14.5% between day 4 and day 20 and by 11% between day 20 and day 40. Key words: Mare’s milk, lactation stage, whey protein distribution, reversed-phase HPLC

Effects of mixtures of red clover and maize silages on milk production and Nitrogen utilisation by dairy cows

Legumes are important to sustainable agriculture because of their N fixing ability and consequent reduced reliance on increasingly scarce oil resources. Our previous studies showed consistently higher intakes and milk yields when red clover silage replaced grass silage in dairy cow diets (Dewhurst et al., 2003). However, the increased intakes of a forage which contains higher levels of N led to a reduction in the efficiency of conversion of feed N into milk N (g/g) from around 0.25 to 0.20 or less. Maize silage has similar high intake characteristics, but its low N content and considerable starch content suggest that it would be highly complementary to red clover silage in terms of N-use efficiency. This study evaluated production and efficiency responses to mixtures of red clover and maize silages in comparison with perennial ryegrass silage.

Feeding Lactose Increases Ruminal Butyrate and Plasma β-hydroxybutyrate in Lactating Dairy Cows*,†

Ruminal fermentation of lactose increases molar proportions of butyrate, which is metabolized by the ruminal epithelium to β-hydroxybutyrate (BHBA). To determine the effects of dietary whey, and specifically lactose, on concentrations of ruminal and blood volatile fatty acids (VFA) and blood BHBA, 8 Holstein and 4 Brown Swiss multiparous cows (210±33 d in milk) were blocked by breed and randomly assigned to one of three 4×4 Latin squares. Treatments were control (CON; 7.1% of dietary dry matter [DM] as cornstarch), liquid whey (WHEY; 9.4% of diet DM) containing 70% lactose on a DM basis, low lactose (LOLAC; 7.1% lactose), or high lactose (HILAC; 14.3% lactose). Diets contained 53% forage as corn silage, alfalfa hay, and grass hay (DM basis) and a corn and soybean meal-based concentrate. Average dietary percentage of crude protein and energy density (Mcal/kg net energy for lactation) were 16.8 and 1.47, respectively. Feeding lactose increased DM intake. Milk production and composition were not affected by diet with the exception of decreased urea nitrogen in milk from cows fed lactose. Greater proportions of ruminal propionate were observed in cows fed CON relative to those fed WHEY and LOLAC. Increasing dietary lactose increased proportions of ruminal butyrate and decreased acetate and branched-chain VFA. Concurrent with the increase in ruminal butyrate concentrations, there was an increase in plasma BHBA as lactose in the diet increased. Concentrations of VFA in plasma were not affected by diet with the exception of the branched-chain VFA, which were increased in cows fed LOLAC compared with WHEY. These data indicate lactose fermentation increases proportions of ruminal butyrate and plasma BHBA in lactating dairy cows; however, the observed increase in plasma BHBA is not sufficient to subject cows to ketosis.

Relationship between content of crude protein in rations for dairy cows, N in urine and ammonia release

This paper discusses the outcomes of experiments investigating the influence of the content of crude protein (CP) in dairy cow diets on nitrogen in urine and ammonia release. It compares different concepts to calculate nitrogen in urine from nitrogen intake, both from a simulation model or equations based on nitrogen intake or feed parameters such as AAT and protein balance value (PBV). The simulation model could predict the outcome roughly but, however, underestimated the milk production in alternatives with a low level of CP. This might be due to an underestimation of the microbial rumen production in these alternatives, when diets had a higher ration of super-pressed beet pulp, which has a high content of easily fermented carbohydrates. The most accurate prediction of nitrogen in urine was made by an equation based on AAT, PBV and nitrogen in milk. Ammonia release can be tripled when %CP increases from approximately 13–19%. Prediction of ammonia was more exact from CP than from N in urine, due to the effect of urine volume on the actual amount of release.

Rice increases productivity compared to other carbohydrate supplements in dairy cows grazing kikuyu ( Pennisetum clandestinum), but not ryegrass ( Lolium multiflorum), pastures

The effect of four carbohydrate supplements on the productivity of dairy cows grazing short rotation ryegrass ( Lolium multiflorum) or kikuyu ( Pennisetum clandestinum) pastures were assessed. When grazing kikuyu, four groups of 20 cows (14 in early and 6 in late lactation) were matched for production and live-weight and were supplemented with 4 kg dry matter (DM)/cow day of either finely rolled barley (B), finely rolled barley sucrose mix (ratio 3:1) (BS), cracked maize (M) or finely milled rice (R), over a 35-day experimental period following a 21-day adjustment period. The production of cows in early ( P<0.001; 17.6 vs. 15.2 l milk/cow day; 516 vs. 455 g protein/cow day for cows fed R and the remainder, respectively), but not late, lactation fed rice was significantly higher reflecting the higher ( P<0.007) digestible organic matter intake of kikuyu pasture of these animals (9.4, 7.2, 7.2 and 6.4 kg/cow day, for cows fed R, BG, B or M, respectively). Cows given rice also had higher ( P<0.01) in vivo organic matter digestibility of kikuyu (69.6 vs. 61.1% for R and the remainder, respectively). Although there was no significant difference between the groups in milk nitrogen (N) (g/cow day) output as a percentage of total N intake (mean: 17.6%), milk urea concentration was significantly lower ( P<0.001; 27.9 vs. 33.6 mg milk urea/100 ml) and live-weight increased more (0.03 vs. −0.18 kg live-weight change/cow day), in cows fed rice than in the remaining groups, respectively, indicating an overall improvement in N balance. The excretion of starch in the faeces of cows fed maize (596 vs. 174 g/cow day for cows fed M and the remainder, respectively), was significantly greater ( P<0.001). When barley or rice was fed to cows grazing ryegrass pasture there was no differences in any of the response variables. The results of this study show that the milk response was greatest to rice as opposed to barley or maize, when Holstein–Friesian dairy cows grazed kikuyu. Rice also had the highest in sacco organic matter digestibility in the rumen. It was hypothesised that this increased productivity to feeding rice was due to the availability of more fermentable energy in the rumen which would result in synchronising more N available from kikuyu for the synthesis of microbial protein as compared to cows fed barley. However, there were nutrient differences between the four carbohydrate sources which may, in part, be responsible for the production responses.

MILK CONCENTRATION AND POSTNATAL ACCRETION OF MINERALS AND NITROGEN IN TWO PHYLLOSTOMID BATS

Abstract Many female bats give birth to a single large young that is weaned at about 90–95% adult size and about 70–80% adult postpartum mass. The need for young to become independent fliers as quickly as possible presumably drives this burdensome development. We considered whether minerals or nitrogen in milk could limit reproductive and developmental capacity in bats. Milk samples were collected during the course of lactation from captive Artibeus jamaicensis and Phyllostomus discolor with known-aged young. Milk mineral (calcium, magnesium, sodium, potassium, and iron) and nitrogen concentrations did not significantly change during the course of lactation, except for sodium, which decreased in A. jamaicensis. When compared with other bats, concentrations of minerals and nitrogen in milk were weakly associated with phylogeny. We calculated daily accretion rates and total amounts of minerals and nitrogen in the body of young bats for each day of development. We also present calculations of the mass of mil...

Strategies to Improve Milk Yield of Lactating Dairy Cows Fed Red Clover Silage

Two trials were implemented to explore nutritional strategies to improve lactation performance of dairy cows fed red clover silage (RCS)-based diets. In Trial 1, 18 early- to midlactation dairy cows were assigned to a replicated 3 × 3 Latin square trial design and fed diets containing forage bases of all RCS, a mixture of RCS and brown midrib corn silage (BMR), and a mixture of RCS and normal corn silage (NCS). Treatment diets were fed for 28 d and contained similar amounts of protein; treatments were formulated to be high in forage fiber so that utilization differences by the lactating cows could be expressed readily between the forage feeding schemes. Cows fed diets containing BMR and NCS consumed significantly more DM and produced approximately 1.5kg more milk than cows fed diets containing all RCS. Cows fed diets containing all RCS also produced less true protein (TP) and nonprotein nitrogen (NPN) in milk. Cows fed BMR ate more DM and NDF than did cows fed diets containing NCS, but the increased DMI did not result in improved lactation performance. In Trial 2, 16 early- to midlactation dairy cows were assigned to a replicated 4 × 4 Latin square trial design and fed RCS-based diets containing moderate (MCP; 17.9%) or high (HCP; 19.5%) levels of CP with or without 4.2% of DM as supplemental dextrose. Cows fed diets containing HCP had increased DMI and milk production when compared with cows fed MCP. In addition, cows fed diets containing HCP significantly increased the CP, TP, NPN, and solids-no-fat (SNF) content of their milk. Yield of all milk components measured was increased by diets containing HCP. Supplementing the diets of cows with 4.2% dextrose had some minor negative effects on milk casein and TP yields, but results were biologically inconclusive.Data from Trial 1 suggest that replacing RCS with BMR or NCS can improve DMI and milk yield of lactating dairy cows. Supplementing RCS-based diets with greater levels of protein (Trial 2) similarly improves DMI and milk yield of lactating dairy cows.

Nitrogenous components of human milk: non-protein nitrogen, true protein and free amino acids

This study reports the nitrogen distribution as total nitrogen, protein nitrogen, non-protein nitrogen and free amino acids in milk, from 195 healthy nursing mothers, of 1 month of lactation. The purpose was to provide data on mature breast milk with the aim of increasing the knowledge of the physiological and nutritional role of human milk. Human milk samples were collected on the 30th day of lactation from well-nourished mothers of term infants in seven pediatric centres in northern, central and southern Italy. The protein and total nitrogen levels were 12.6 g/l±2.0 and 2350 mg/l±390 respectively. The percentage of non protein nitrogen was 15% and the absolute value was 341 mg/l±76. The amount of nitrogen derived from each amino acid varied widely; the cumulative amino acid nitrogen presented a minimum of 13 mg/l and a maximum of 82 mg/l. Taurine, serine, glutamic acid and glutamine were the only free amino acids, accounting for a large proportion of the FAA in the non-protein nitrogen fraction. The sum of glutamic acid and glutamine (1430 μmol/l±489) in human milk samples represented 49% of total free amino acids.

Uterine, Ovarian, and Production Responses of Lactating Dairy Cows to Increasing Dietary Concentrations of Menhaden Fish Meal

The primary objective was to determine whether the dietary polyunsaturated fatty acids, eicosapentaenoic (EPA, C20:5, n-3) and docosahexaenoic (DHA, C22:6, n-3), present in fish meal (FM) can attenuate uterine secretion of PGF2α in response to a challenge with estradiol and oxytocin in lactating dairy cows. Cycling multiparous cows (n = 32) were fed diets containing 0 (0FM), 2.6 (2.6FM), 5.2 (5.2FM), or 7.8% menhaden FM (7.8FM). The diet consisting of 7.8FM also contained fish oil (0.28% of dietary dry matter) to increase intake of EPA and DHA. Average dry matter intake was 24.9 kg/d and unaffected by diet. Combined intakes of EPA and DHA averaged 0, 12.8, 24.1, and 54.0 g/d from the 0FM, 2.6FM, 5.2FM, and 7.8FM diets, respectively. At 30 to 34 d after initiation of dietary treatments, cows received an i.m. injection of 100μg of GnRH followed by i.m. administration of 25 and 15mg of PGF2α after 7 and 8 d, respectively. Synchronous ovulation was induced by an injection of 3000 IU of human chorionic gonadotropin (hCG) given 24h later on d 9. Subsequent luteal phase increases in plasma progesterone concentrations did not differ (0.88ng/ml per day). At 15 d after hCG injection, cows were injected with estradiol-17β (3mg, i.v.) at 0900h and oxytocin (100 IU, i.v.) at 1300h. Plasma PGF2α metabolite concentrations after oxytocin injection were reduced in cows fed diets containing FM compared with those fed 0FM. Milk production (39.1 kg/d) and concentrations of fat, protein, or urea nitrogen in milk were not affected by diet. Feeding fish meal and fish oil containing eicosapentaenoic acid and docosahexaenoic acid reduced the proportion of n-6 fatty acids and increased that of n-3 fatty acids in milk in a dose-responsive manner.

Determination of Crude Protein in Animal Feed, Forage, Grain, and Oilseeds by Using Block Digestion with a Copper Catalyst and Steam Distillation into Boric Acid: Collaborative Study

A collaborative study was conducted to evaluate the repeatability and reproducibility of an extension of AOAC Official Method 991.20, Nitrogen (Crude) in Milk, to animal feed, forage (plant tissue), grain, and oilseed materials. Test portions are digested in an aluminum block at 420 degrees C in sulfuric acid with potassium sulfate and a copper catalyst. Digests are cooled and diluted, and concentrated sodium hydroxide is added to neutralize the acid and make the digest basic; the liberated ammonia is distilled by using steam distillation. The liberated ammonia is trapped in a weak boric acid solution and titrated with a stronger standardized acid, hydrochloric acid; colorimetric endpoint detection is used. Fourteen blind samples were sent to 13 collaborators in the United States, Denmark, Sweden, Germany, and the United Kingdom. Recoveries of nitrogen from lysine, tryptophan, and acetanilide were 86.8, 98.8, and 100.1%, respectively. The within-laboratory relative standard deviation (RSDr, repeatability) ranged from 0.40 to 2.38% for crude protein. The among-laboratories (including within-) relative standard deviation (RSD(R), reproducibility) ranged from 0.44 to 2.38%. It is recommended that the method be adopted First Action by AOAC INTERNATIONAL. A lower concentration (1% H3BO3) of trapping solution was compared with the concentration specified in the original protocol (4% H3BO3) and was found comparable for use in an automatic titration system in which titration begins automatically as soon as distillation starts. The Study Directors recommend that 1% H3BO3 as an optional alternative to 4% boric acid trapping solution be allowed for automatic titrators that titrate throughout the distillation.

Orchardgrass versus Alfalfa for Lactating Dairy Cattle: Production, Digestibility and Nitrogen Balance

Jonker, J.S., Cherney, D.J.R., Fox, D.G., Chase, L.E. and Cherney, J.H. 2002. Orchardgrass versus alfalfa for lactating dairy cattle: production, digestibility and nitrogen balance. J. Appl. Anim. Res., 21: 81–92. Effects of forage fiber source on milk production, digestibility and nitrogen balance were studied for three hay forages: early bloom alfalfa (ALF), early bloom orchardgrass (OG-E) and late bloom orchardgrass (OG-L). Multiparous mid-lactation Holstein cows were used in a 3x3 Latin square design replicated four times (12 cows) for the production trial and replicated three times (9 cows) for in vivo digestibility and nitrogen balance. Cows were fed one of three isonitrogenous and isocaloric rations containing 9.5 g kg−1 NDF per kg BW from forage. Cows consumed similar quantities of NDF (14.7±0.8g kg−1 BW) and the ALF, OG-E and OG-L diets produced 29.1, 30.1 and 32.5 kg d−1 of milk, respectively. Apparent digestibility for NDF and DM was higher for the orchardgrass rations than the alfalfa based ration. Higher N intake resulted in higher N output in both urine and milk, but N excretion in feces was not different between diet treatments. Efficiency of conversion of N to milk was 25.9%. Home grown forage accounted for 78.8% of N in the ALF diets, while only 47.8% and 22.7% of N came from OG-E and OG-L, respectively. Balanced orchardgrass dairy rations can be well utilized by lactating dairy cattle and can clearly have a place in nutrient management systems, provided grass is harvested at a high yield and quality.

Feeding dairy cows for decreased ammonia emission

Greater demands will be placed on animal production in order to minimise emissions of ammonia and other wastes. Ammonia originates in the nitrogen part of faeces and urine. Thus, a good method to decrease ammonia is to reduce nitrogen residues in manure by appropriate feed rations. This was done in a study concerning the effects of decreased protein supply on ammonia release from dairy cattle manure. Rations with 14 and 19% of protein in the total dry matter ration were compared. Also, two feeding routines were included, separate feeds and a total mixed ration. The ammonia release was estimated on 24-h samples of manure (faeces and urine) from individual cows. At low protein levels, the ammonia emission decreased by 2/3 compared with the high level. No effects on milk production (mean 31 kg) or on milk composition were observed in this short-term experiment. Nitrogen efficiency, i.e. milk nitrogen in percent of consumed nitrogen, was 39% at low protein level compared with 29% at high level. Ration composition will be important in the efforts to reduce negative environmental influences resulting from milk production. The applied measuring technique seems to be a good tool in estimating the influences of diet on gaseous emissions.

The influence of applied heat treatments on whey protein denaturation

Reconstituted skim milk with 8.01% DM was standardized with 3% skim milk powder and with 3% demineralized whey powder (DWP), respectively. Gained milk samples are named as 8%, 11% and 8%+3%DWP. All samples were heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min, respectively. Untreated milk was used as control. Milk samples were coagulated by glucono-d-lactone (GDL) at the temperature of 45?C until pH 4.60 was reached. Milk nitrogen matter content decreased during heat treatments, but linear relationship between applied heat treatments and nitrogen matter decreasing was not found. Nitrogen matter content of sera gained from both untreated and heat treated milk increased with the increase of milk dry matter content and with the addition of DWP. The higher temperature of applied heat treatment, the smaller sera nitrogen matter content. Nitrogen matter content in sera obtained from untreated milk were 64.90 mg%, 96.80 mg% and 117.3 mg% for milk 8%, 11% and 8%+3.0% DWP, respectively. Sera samples obtained from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 38.70 mg% 38.30 mg% and 37.20 mg% of nitrogen matter, respectively. Sera samples obtained from milk 11% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 55.90 mg%, 52.80 mg% and 51.30 mg% of nitrogen matter, respectively. Sera samples obtained from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min had 69.50 mg%, 66.20 mg% and 66.00 mg% of nitrogen matter respectively. Distribution of nitrogen matter from untreated milk to milk sera were 12.01%, 11.14% and 17.69% for milk 8%, 11% and 8%+3.0% DWP respectively. Distribution of nitrogen matter from milk 8% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples were 6.99%, 6.72% and 6.59%, respectively. Distribution of nitrogen matter from milk 11% heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples, were 6.02%, 5.32% and 5.21%, respectively. Distribution of nitrogen matter from milk 8%+3%DWP heat treated at 85?C/10 min, 90?C/10 min and 95?C/10 min to sera samples were 9.64%, 8.66% and 8.67%, respectively. Whey protein denaturation increased with increasing of the temperature of the applied heat treatment. Denaturation was the most significant for milk sample 11%.

Effects of a Nonforage Diet on Milk Production, Energy, and Nitrogen Metabolism in Dairy Goats throughout Lactation

The objective of the experiment was to compare a silage-based control diet (C) with a nonforage diet (NF) in dairy goats throughout lactation in terms of animal performance and energy utilization. Eight Saanen goats were divided into two groups and fed C or NF, a commercial blend that included sunflower meal, cassava, coconut meal, and whole cottonseeds as the main ingredients that was characterized by a small particle size and a high crude protein content. In early, mid, and late lactation (44, 100, and 219 days in milk) the goats were individually tested for dry matter intake (DMI), digestibility, milk yield and composition, milk renneting properties, rumen and plasma parameters, and nitrogen and energy utilization (open circuit respiration chambers). During early and mid lactation, the NF fed goats had a very high DMI: 2946 and 2915 g/ d, respectively. Nevertheless, milk yield was similar for the two treatments: 4369 vs. 4342 and 3882 vs. 3841 g/d for goats fed diets C and NF during the first and second periods, respectively. Milk fat content was not statistically different between the two diets. The protein content and rheological parameters of milk were similar for the two diets. Nonprotein nitrogen and urea levels in milk of goats fed NF were significantly higher than goats fed C. Ruminal ammonia and plasma urea nitrogen were also significantly increased by diet NF, due to its high protein content. Plasma glucose, ßbeta;-hydroxybutyrate, and nonesterified fatty acids and ruminal volatile fatty acids were not influenced by dietary treatment. Dietary NF significantly decreased energy digestibility (74.5 vs. 65.8%, on average for the lactation, for C and NF, respectively) and had a significantly lower metabolizability (metabolizable energy/intake energy; 66.6 vs 58.0%, on average); however, the efficiency of utilization of metabolizable energy was unaffected by the diet. In conclusion, goats were fed a nonforage diet during the entire lactation without detrimental effect on their health and productive performance.