Milk Casein Content Research Articles

Italian and Italian-style hard cooked cheeses: Predictive formulas for Parmigiano-Reggiano 24-h cheese yield

Predicting the 24-h Parmigiano-Reggiano (PR-RE) cheese yield (CY) is relevant for controlling the efficacy of cheese-making processes, yet the existing formulas are old and need to be re-evaluated. To this aim, 119 cheese-making trials were carried out in 20 different dairies to calculate the 24-h actual CY. From a subset of 89 trials, 35 formulas for 24-h PR-RE CY were developed by applying a multiple regression analysis using up to 14 milk parameters as predictors. The formulas were validated on a second data subset (30 trials). The predictive ability was not significantly improved by increasing the predictors when a formula based on milk fat and casein contents was considered (R2 = 0.872). The formula predicted 24-h CY more effectively than the existing formulas for Italian hard cheeses. Using a database obtained from a single dairy, the predictive ability of the resulting formula was further improved.

A 2-year study on milk quality from three pasture-based dairy systems of contrasting production intensities in Wales

SUMMARYThere is an increasing interest in pasture-based dairy systems in Europe, mainly because of increasing production costs for intensive dairying. Milk is a matrix of compounds that influence nutritional and manufacturing properties, many dependent on husbandry linked to pasture-based systems (increase in pasture intake, forage : concentrate ratio, clover inclusion in swards/silages and use of alternative dairy breeds). The present study investigated the impact of three grazing-based dairy systems with contrasting feeding intensity or reliance on pasture intakes (conventional high-intensity, low pasture intake [CH], organic medium-intensity, medium pasture intake [OM], conventional low-intensity, high pasture intake [CL]) on milk fatty acid (FA) profiles, protein composition and α-tocopherol and antioxidants concentrations. The proportion of animals of alternative breeds (e.g. Jersey) and crossbred cows in the herd increased with decreasing production intensity (CH < OM < CL). Milk constituents known to be beneficial for human health, such as vaccenic acid, rumenic acid, monounsaturated FA, polyunsaturated FA, antioxidants and caseins, were elevated with decreasing production intensity (CH < OM < CL), while less desirable saturated FA were lower, although not all differences between OM and CL were significant. Omega-3 FA were maximized under OM practices, primarily as a result of higher clover intake. Increases in pasture intake may explain the higher concentrations of desirable FA while increased use of crossbreed cows is likely to be responsible for higher total protein and casein content of milk; a combination of these two factors may explain increased antioxidant levels. The higher concentrations of vaccenic acid, rumenic acid, omega-3 FA, lutein, zeaxanthin, protein and casein in OM and CL milk were found over most sampling months and in both years, reinforcing the higher nutritional quality and manufacturing properties associated with milk from these systems. A switch to pasture-based dairy products would increase the intake of milk's beneficial compounds and reduce consumption of less desirable saturated FA.

Grazing season and forage type influence goat milk composition and rennet coagulation properties

Two different types of pasture (cultivated and rangeland) and 2 different hay qualities (high and low quality) were examined for their effects on goat milk composition and rennet coagulation properties. Furthermore, the effect of dietary treatments in both the early and late grazing season was studied. As lactation stage is known to influence milk composition, the goats in the early and late grazing season were in the same lactation stage at the start of the experiment. The milk composition was influenced both by dietary treatment and season. Milk from goats on pasture was superior to those on hay by containing a higher content of protein and casein, and the goats on cultivated pasture had the highest milk yield. Casein composition was significantly influenced by forage treatment. Goats grazing on cultivated pasture had higher contents of αs1-casein and also of κ-casein compared with the other treatments, whereas goats grazing on rangeland had the highest content of β-casein. Factors such as milk yield, casein micelle size, αs2-casein, and calcium content were reduced in late compared with early season. More favorable rennet coagulation properties were achieved in milk from the early grazing season, with shorter firming time and higher curd firmness compared with milk from the late grazing season, but the firming time and curd firmness were not prominently influenced by forage treatment. The content of αs2-casein and calcium in the milk affected the firming time and the curd firmness positively. The influence of season and forage treatment on especially milk yield, casein content, and rennet coagulation properties is of economic importance for both the dairy industry and goat milk farmers.

Composition of major proteins in cow milk differing in mean protein concentration during the first 155 days of lactation and the influence of season as well as short-term restricted feeding in early and mid-lactation

A variety of proteins contributes greatly to the unique nutritional and functional quality of dairy cow milk. Particularly, milk casein content and composition have substantial influence on the processing capabilities. In the present study, milk of 23 multiparous Holstein-Friesian cows, grouped as high- (3.49 ± 0.05%; n = 11) and low-protein (3.03 ± 0.05%; n = 12) cows, was sampled approximately weekly during the first 155 days of lactation to determine the course of relative milk protein composition (α-lactalbumin; β-lactoglobulin; α-, β-, and κ-casein). Furthermore, feed restrictions by 30% of dry matter intake in early and mid-lactation as well as experimental tissue biopsies were conducted to observe their effect on milk protein composition. Milk protein composition was relatively stable and displayed similar concentration patterns throughout the experimental period between both groups. Mean relative concentrations of α-, β-, κ-casein, α-lactalbumin, and β-lactoglobulin were 34.2, 31.4, 16.0, 2.1, and 9.7% of total protein, respectively. Feed restrictions did not alter milk protein composition, whereas the season influenced α- and β-casein as well as α-lactalbumin. Further, effects were observed in both groups at times of unfamiliar stressful situations caused by taking liver or muscle biopsies. As a result, the relative concentration of β-casein increased. Therefore, acute stress factors may lead to a deviation in milk protein composition and should be avoided.  

Sequence polymorphisms at the growth hormone GH1/GH2-N and GH2-Z gene copies and their relationship with dairy traits in domestic sheep (Ovis aries)

The purpose was to analyze the growth hormone GH1/GH2-N and GH2-Z gene copies and to assess their possible association with milk traits in Sarda sheep. Two hundred multiparous lactating ewes were monitored. The two gene copies were amplified separately and each was used as template for a nested PCR, to investigate single strand conformation polymorphism (SSCP) of the 5'UTR, exon-1, exon-5 and 3'UTR DNA regions. SSCP analysis revealed marked differences in the number of polymorphic patterns between the two genes. Sequencing revealed five nucleotide changes at the GH1/GH2-N gene. Five nucleotide changes occurred at the GH2-Z gene: one was located in exon-5 (c.556G>A) and resulted in a putative amino acid substitution G186S. All the nucleotide changes were copy-specific, except c.*30delT, which was common to both GH1/GH2-N and GH2-Z. Variability in the promoter regions of each gene might have consequences on the expression level, due to the involvement in potential transcription factor binding sites. Both gene copies influenced milk yield. A correlation with milk protein and casein content was also evidenced. These results may have implications that make them useful for future breeding strategies in dairy sheep breeding.

Effect of protein supplementation on milk production and metabolism of dairy cows grazing tropical grass

The objectives of this study were to determine if midlactation dairy cows (Bos taurus L.) grazing intensively managed elephantgrass would have their protein requirement met exclusively with the pasture and an energy concentrate, making the use of protein ingredients unnecessary, as well as to determine the dietary crude protein (CP) content that would optimize the efficiency of N utilization (ENU). Thirty-three Holstein and crossbred (Holstein × Jersey) midlactation dairy cows, producing approximately 20kg/d, were grouped within breed into 11 blocks according to milk yield and days in milk. Within blocks, cows were randomly assigned to 1 of 3 treatments and remained in the study for 11 wk. The control treatment contained only finely ground corn, minerals, and vitamins, and it was formulated to be 8.7% CP. Two higher levels of CP (formulated to be 13.4 and 18.1%) were achieved by replacing corn with solvent-extracted soybean meal (SSBM). Pasture was fertilized with 50kg of N/ha after each grazing cycle and averaged 18.5% CP (dry matter basis). No differences were observed in milk yield or milk fat, protein, and casein content or casein yield. In addition, pasture intake was not different among treatments. Milk urea N increased linearly as the concentrate CP content increased. Cows fed the 8.7% CP concentrate had higher ENU. In another experiment, 4 ruminally cannulated Holstein dry cows were used in a metabolism trial designed in a 4×4 Latin square. Cows were fed the same treatments described as well as a fourth treatment with 13.4% CP in the concentrate, in which urea replaced SSBM as the main N source. Ruminal volatile fatty acid concentration and microbial synthesis were not affected by levels or sources of N in the concentrate. Ruminal NH3N content increased as the concentrate CP content increased. Inclusion of SSBM in the concentrate did not increase production and decreased the ENU of midlactation dairy cows grazing on tropical forage. Supplementation of an 8.7% CP concentrate, resulting in a diet with CP levels between 15.3 and 15.7% of dry matter, was sufficient to meet the protein requirements of such milk production, with the highest ENU (18.4%).

Effect of parity, days in milk, and milk yield on detailed milk protein composition in Mediterranean water buffalo

The effects of some nongenetic factors on milk protein fraction contents and relative proportions were estimated in 606 individual milk samples of Mediterranean water buffalo. Content of αS1-casein (CN), αS2-CN, β-CN, γ-CN, κκ-CN, glycosylated κ-CN (glyco-κ-CN), α-lactalbumin, and β-lactoglobulin was measured by reversed-phase HPLC. Relative contents of αS1-CN%, αS2-CN%, β-CN%, and κ-CN% were, respectively, 32.1, 17.1, 34.5, and 15.7%, whereas γ-CN% accounted for 0.6% of total casein content. Increasing total casein content in milk would result in a greater proportion of β-CN% at the expense of all of the other major casein fractions, especially of κ-CN%. Values of αS2-CN%, β-CN%, and γ-CN% tended to decrease with parity, although their variations were not significant, whereas αS1-CN% and glyco-κ-CN% showed the opposite trend. Contents of most protein fractions showed the typical trends observed for milk components as lactation progressed, with high contents in early lactation, a minimum in midlactation, followed by a gradual increase toward the latter part of lactation. Values of αS1-CN% increased during lactation, whereas αS2-CN% decreased. The proportion of β-CN% had its maximum value between 60 and 160d of lactation, followed by a decrease, whereas κ-CN% had its minimum value in early lactation (<60d) and remained relatively constant in the period of mid and late lactation. Glyco-κ-CN% and β-lactoglobulin% decreased in the first part of lactation, to reach their minimum values in midlactation, followed by an increase. Milk of top-producing buffaloes, compared with that of low-producing ones, had a significantly greater value of β-CN% and glyco-κ-CN%, and lower proportion of αS1-CN%. The possible effect exerted by protein genetic variants in affecting variation of milk protein fraction contents and relative proportions should be further considered to better get insight into buffalo milk protein composition.

Short communication: Factors affecting coagulation properties of Mediterranean buffalo milk

The aim of this study was to investigate sources of variation of milk coagulation properties (MCP) of buffalo cows. Individual milk samples were collected from 200 animals in 5 herds located in northern Italy from January to March 2010. Rennet coagulation time (RCT, min) and curd firmness after 30min from rennet addition (a30, mm) were measured using the Formagraph instrument (Foss Electric, Hillerød, Denmark). In addition to MCP, information on milk yield, fat, protein, and casein contents, pH, and somatic cell count (SCC) was available. Sources of variation of RCT and a30 were investigated using a linear model that included fixed effects of herd, days in milk (DIM), parity, fat content, casein content (only for a30), and pH. The coefficient of determination was 51% for RCT and 48% for a30. The most important sources of variation of MCP were the herd and pH effects, followed by DIM and fat content for RCT, and casein content for a30. The relevance of acidity in explaining the variation of both RCT and a30, and of casein content in explaining that of a30, confirmed previous studies on dairy cows. Although future research is needed to investigate the effect of these sources of variation on cheese yield, findings from the present study suggest that casein content and acidity may be used as indicator traits to improve technological properties of buffalo milk.

Effect of saccharomyces cerevisiae yeast on milk protein content and composition and serum mineral concentrations in sheep

The experiment was conducted on 26 nursing Kamieniec ewes from a breeding herd. The animals were divided into two equal groups characterized by the same litter type, age and sex of suckling lambs: I – control and II – experimental. Throughout the 70-day lactation period, both groups were fed identical diets comprising haylage of grasses and legumes, meadow hay and CJ concentrate in daily rations of: 2.80 kg haylage of grasses and legumes, 0.6 kg meadow hay and 0.6 kg CJ concentrate per ewe. Group II animals were fed the CJ concentrate with the addition of Inter Yeast S® Saccharomyces cerevisiae dried yeast in the amount of 50 g kg–1 of the concentrate. Milk was sampled during control milking runs on lactation day 28 and 70. The collected samples were analyzed to determine the content of protein, whey protein, casein, αs, β and κ casein fractions. Blood was sampled twice from the jugular vein on lactation day 28 and 70. After separation of serum, the following nutrient concentrations were determined: inorganic phosphorus (P in ), calcium (Ca) and magnesium (Mg). No significant variations were reported in the percentage share of whey proteins in ewe’s milk during the peak and towards the end of lactation. The yeast preparation had no effect on the casein content of milk. Yeast supplementation si

Morning versus afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) affects feed intake, milk yield and composition in Girgentana goats

Twenty lactating Girgentana goats were used to evaluate the effect of morning v. afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) on feed intake, milk yield and milk composition. Goats were randomly divided into two groups of ten animals, receiving 10 kg of fresh Berseem clover cut at 9.00 (AM group) or 16.00 (PM group), respectively; 500 g of concentrate was given individually to goats before offering forage. Feed intake increased (P<0·01) in the PM group (30·5 v. 25·3 g dry matter/kg body weight), associated with the different nutrient content of diets: lower crude protein but higher dry matter, neutral detergent fibre, water soluble carbohydrates (WSC) and total fatty acids in the PM-harvested forage. Milk production, protein and casein content were higher (P<0·05) in the PM group (1415 g/d, 3·25% and 2·42% v. 1277 g/d, 3·15% and 2·33%, respectively), whereas no differences between groups were detected for milk fat, lactose or urea content. Body weight slowly decreased from the start to the end of the experiment, without differences between groups. This study showed an important milk yield responses in Girgentana goats offered afternoon-cut compared with morning-cut Berseem clover, due to a marked increase in WSC in the afternoon-cut forage.

Effects of supplementation with 2-hydroxy-4-(methylthio)-butanoic acid isopropyl ester on splanchnic amino acid metabolism and essential amino acid mobilization in postpartum transition Holstein cows

The present study aimed to investigate the effects of 2-hydroxy-4-(methylthio)-butanoic acid isopropyl ester (HMBi) supplementation on splanchnic AA metabolism, essential AA (EAA) mobilization, and plasma AA status in postpartum transition dairy cows. The EAA mobilization was calculated by difference: EAA excretion in milk protein − net portal absorption of EAA or net splanchnic release of EAA. Eight Holstein cows fitted with permanent indwelling catheters in the hepatic portal vein, hepatic vein, mesenteric vein, and an artery in the dry period preceding second parturition were used in the study. Cows were randomly allocated to 1 of 4 treatments in a 2×2 factorial arrangement with factor 1: control (calcium carbonate) versus HMBi [1.5g of HMBi/kg of dry matter (DM)] and factor 2: high dietary ethanol (19g/kg of DM) versus high dietary propanol (16g/kg of DM). Only factor 1 data are presented. Treatments were administered in 4 total mixed rations and initiated on the day of parturition. Cows were sampled 14 d before expected parturition and 4, 15, and 29 d after parturition. Supplementation with HMBi tended to increase milk fat content but not fat yield, tended to impose a slower rate of decrease in milk casein content with increasing days in milk (DIM), prevented the decrease in plasma Met associated with parturition for control, reduced plasma concentration of Ser, tended to reduce plasma concentrations of Gly and His, and tended to increase hepatic uptake of Met postpartum. Cows excreted 248±18g more EAA in the milk at 4 DIM than was released from splanchnic tissues. The EAA deficiency decreased as lactation progressed and was not affected by HMBi supplementation. It was estimated that 4,700±600g of EAA from extra-splanchnic tissues were secreted in milk protein during the first 29 DIM. Extra-splanchnic EAA mobilization can be crucial to sustain milk protein yield in the postpartum transition period and HMBi is a fast-working Met source that can improve Met status of postpartum transition cows.

Effect of wheat gluten and extracted, protected soybean meal addition to the diet of cows with different beta-lactoglobulin genotypes on the composition and physical properties of milk

The effect of wheat gluten or extracted soybean meal (300 g of crude protein/head/day) on milk yield, composition and its physical properties was analysed in 53 cows of Polish Holstein-Friesian breed with different milk beta-lactoglobulin (blg) genotypes (AA, AB and BB). The addition of wheat gluten to the diet of cows with the AA and AB blg genotypes caused a significant increase in crude protein (by 0.21; &lt;I&gt;P&lt;/I&gt; ≤ 0.05, and 0.19%; &lt;I&gt;P&lt;/I&gt; ≤ 0.01), casein (by 0.15; &lt;I&gt;P&lt;/I&gt; ≤ 0.05, and 0.15%; &lt;I&gt;P&lt;/I&gt; ≤ 0.01) and dry matter content (0.3 and 0.5%; &lt;I&gt;P&lt;/I&gt; ≤ 0.05) in milk, and a significant increase in beta-casein production (0.6 g/l; &lt;I&gt;P&lt;/I&gt; ≤ 0.05, and 0.6 g/l; &lt;I&gt;P&lt;/I&gt; ≤ 0.01) and kappa-casein yield (0.3 g/l; &lt;I&gt;P&lt;/I&gt; ≤ 0.05) in the case of cows with the AA genotype. Milk acidity and electrical resistance in milk were lowered. The cows with the BB blg genotype did not show any significant changes in milk composition. The supplementation of extracted soybean meal to cows with the AB and BB blg genotype led to a significant increase in milk protein (0.26% and 0.21%; &lt;I&gt;P&lt;/I&gt; ≤ 0.01) and casein content (0.2 and 0.15%; &lt;I&gt;P&lt;/I&gt; ≤ 0.01), beta-casein production (0.60 and 0.50 g/l; &lt;I&gt;P&lt;/I&gt; ≤ 0.01) and to a decrease in kappa-casein content (by 0.7%; &lt;I&gt;P&lt;/I&gt; ≤ 0.05) in cows with the BB genotype. The production of kappa-casein increased in cows with the AB genotype (by 0.2 g/l; &lt;I&gt;P&lt;/I&gt; ≤ 0.01). In the case of all genotypes, an increase in milk active acidity and thermostability and a decrease in electrical resistance in milk were noted. It was observed that cows with different blg genotypes differently utilised the protein from given supplements for the production of individual milk components, which may be used in rationalisation of their feeding and improvement of milk content.

Yield and composition of milk from Polish Holstein-Friesian and Jersey cows in particular months of the first lactations as dependent on milk protein polymorphism (short communication)

Abstract. The experiment was performed on 121 primiparous Polish Holstein-Friesian (PHF) cows and 36 primiparous Jersey (JER) cows. The highest decrease in casein yield was noted in JER cows at 7.36 % on day 90 of lactation, 15.95 % on day 150, 26.78 % on day 210, 37.01 % on day 270 and 39.67 % on day 330. In PHF cows this decrease was substantially lower, at 4.98 %, 7.65 %, 8.72 %, 10.50 % and 16.19 % respectively. The casein content of milk from primiparous PHF cows ranged from 2.38 % (LGB – day 60) to 3.09 % (LGB BB – day 330), and it was found to be considerably lower in JER cows, varying between 2.35 % (CSN3 BB – day 30) and 3.61 % (CSN3 BB – day 210). The highest casein yield was recorded in PHF cows with the following genotypes: LGB AA (day 60), CSN1S1 BB (day 60), CSN2 AB (day 270), CSN3 BB (day 150). In JER cows the highest casein yield was noted on day 90 of lactation with respect to the following genotypes: LGB BB, CSN1S1 BC, CSN2 AA and CSN3 BB. In PHF cows the greatest effect on whey protein yield was exerted by the following genotypes: LGB AA (day 90), CSN1S1 BC (day 60), CSN2 AA (day 90); the CSN3 BB genotype influenced whey protein yield in cattle of both breeds (day 90). In JER cows the highest daily yield of whey proteins was observed on day 90 of lactation, with regard to the following genotypes: LGB BB, CSN1S1 BC, CSN2 AB and CSN3 BB.

Lactational effects of adding a fibrolytic enzyme complex to the concentrate of lactating dairy goats

Twenty-four multiparous Murciano-Granadina dairy goats in mid-lactation (wk 8 to 30) were used in a single cross-over design to evaluate the effects of supplementation with an exogenous fi brolytic enzyme preparation, characterized by cellulase and xylanase activities, on feed intake, milk yield and composition, and liveweight and body condition changes. Goats received ad libitum a basal total mixed ration composed of 65% forage and 35% concentrate. The treatments were: control (without enzyme) and experimental with enzyme (included at the recommended commercial dose of 4.7 ml/kg concentrate). Feed intake, milk yield, 4% fat corrected milk yield, and milk composition were not affected by enzyme supplementation, although milk casein content tended to decrease in the enzyme treatment. Body weight change tended to be higher with the enzyme treatment.

Feeding Soybean Oil to Dairy Goats Increases Conjugated Linoleic Acid in Milk

A total of 24 Murciano-Granadina dairy goats milked once daily throughout lactation were used to study the effects of including soybean oil (SBO) in the diet on lactational performance and milk fatty acid (FA) content, particularly conjugated linoleic acid (CLA) and trans-vaccenic acid (trans-11 C18:1, TVA). Three weeks after parturition, goats were allocated to 2 balanced groups according to lactation number, body weight, and daily milk yield, and were kept in separate pens. The experiment consisted of a 2-period (28 d each) crossover with 2 dietary treatments: control and SBO (6% as fed in the concentrate). Goats were fed dehydrated fescue (ad libitum), alfalfa pellets (0.5 kg/d), and concentrate (1 kg/d) to which the SBO was or was not added. Forage was fed in the pens, and concentrate was fed individually in 2 equal portions at milking (0900h) and in the afternoon (1700h). Final SBO content in the consumed SBO diet was 2.5% (dry matter basis). Diets were isonitrogenous (17.4% crude protein), but their total FA content varied from 2.2% (control) to 4.6% (SBO). There was no effect of SBO on dry matter intake, milk yield, energy-corrected milk, body weight, or body condition score. Compared with the control diet, feeding SBO increased milk fat content (4.57 vs. 5.24%) and yield as well as total solids content. Soybean oil had no effect on milk crude and true protein contents, but it reduced milk casein content (2.48 vs. 2.34%). Short- and medium-chain FA decreased by feeding SBO, whereas long-chain FA increased. Feeding preformed linoleic acid through SBO increased milk concentrations of linoleic, oleic, and stearic FA but reduced levels of linolenic and palmitic FA. As a consequence, feeding SBO decreased the saturated-to-unsaturated FA ratio and the atherogenicity index. Compared with the control treatment, milk contents of cis-9, trans-11 CLA (0.68 vs. 2.03%) and TVA (2.04 vs. 6.41%) in the SBO treatment increased by approximately 200%. In conclusion, feeding a moderate dose of SBO to dairy goats was a useful way to increase milk fat, CLA, and TVA contents in milk and to reduce the atherogenicity index without negative effects on intake, milk yield, and protein content.

Factors Affecting the Retention of Rennet in Cheese Curd

The coagulant retained in cheese curd is a major contributor to proteolysis during ripening. The objective of this study was to quantify the effects of several milk-related factors and parameters during cheese manufacture on the retention of coagulant in cheese curd. The amount of coagulant retained in curd was determined by its activity on a synthetic heptapeptide (Pro-Thr-Glu-Phe-[NO2-Phe]-Arg-Leu) using reversed-phase HPLC. The retention of chymosin in cheese curd increased significantly when the pH of milk was reduced at rennet addition below pH 6.1, the pH at whey drainage below pH 5.7, or the average casein micelle size in milk and when the ionic strength of milk was increased. The casein content of milk and the quantity of chymosin added to milk had no significant effect on the retention of chymosin in curd; the quantity of coagulant bound per gram of casein remained unchanged.

Is there a feeding strategy to increase milk casein content?

Because more than 60% of milk produced in Italy is transformed into cheese, milk economical value strongly depends on cheese yield. Among the factors that influence cheese yield, milk casein and fat content plays a major role: when milk is converted into Grana Padano and Parmigiano reggiano, three grams of seasoned cheese are produced from one gram of milk casein.....

Effects of dietary protein level on ewe milk yield and nitrogen utilization, and on air quality under different ventilation rates

The experiment, which lasted 53 d, was conducted during the winter (February and March) of 2004 and used 48 Comisana ewes in mid lactation. A 2 x 2 factorial design was used, with ewes receiving two levels of dietary crude protein (CP) (moderate, 16% CP v. low, 13% CP) in the dry matter (DM) and being exposed to two ventilation rates (moderate, 47 m3/h v. low, 23.5 m3/h per ewe) for each dietary treatment. Air concentrations of NH3 and of microorganisms were measured twice weekly. Milk yield was recorded daily. Individual milk samples were analysed weekly for composition and fortnightly for bacteriological characteristics. After the last milk sampling (day 49 of the study period), four animals from each group were placed in a metabolism box and their individual faeces and urine were collected for three consecutive days. Amounts of urine and faeces excreted, and urinary and faecal N outputs were measured. The 16% CP diet resulted in a lower milk casein content and a higher milk urea concentration than the 13% CP diet, as well as in a reduced gross efficiency of utilization of dietary N, a greater amount of N excreted and a higher total coliform concentration in milk. The moderate ventilation rate resulted in higher yields of milk, irrespective of CP content. Significant interactions of CP level x ventilation rate were found for the amounts of urine, of total water and of faecal N, and for mesophilic concentration in milk, the highest values being displayed by the ewes fed the 16% CP diet and exposed to the low ventilation rate. The moderate dietary CP level and low ventilation rate had a deleterious effect on air concentrations of microorganisms and ammonia. Results suggested that a reduction of dietary CP level from 16 to 13% of DM had no detrimental effect on ewe milk yield in mid lactation and could even improve some of its nutritional and hygienic characteristics. Our findings also indicate that the choice of a proper ventilation rate is critical for high efficiency of production in the lactating ewe, especially in intensively managed flocks receiving diets high in CP.

Relation among milk production and composition and blood profiles and fecal P and nitrogen in goats on rangeland

Ninety-two multiparous goats of undefined genotype (native × traditional dairy breeds) kept on rangeland were used to assess the association between blood components and fecal P and nitrogen at the beginning of lactation on milk production and composition. The stepwise regression analysis revealed that fecal P was the only significant explanatory variable positively associated with milk production ( r 2 = 0.08; P < 0.01). Goats with fecal phosphorus >0.21% produced 63.5 ± 21 kg of milk whereas does with <0.21% of this element in feces produced 54.3 ± 18 kg per lactation. Milk yield at the beginning and middle of lactation and total milk production per lactation was not related to serum glucose, urea, creatinine, cholesterol, total proteins, P, Ca, Mg, Cu, Mg and Zn concentrations at the beginning of lactation. Fecal P, determined by the forward set-up selection, showed also the greatest contribution to the variability in milk fat content ( r 2 = 0.10; P < 0.01), milk protein percentage ( r 2 = 0.06; P < 0.05), milk casein content ( r 2 = 0.06; P < 0.05), and lactation length ( r 2 = 0.12; P < 0.01). It was concluded that metabolic profiles were of no practical use to predict milk yield and composition in goats in this feed-limited environment. These results also indicate that fecal P is a significant predictor of milk yield, milk composition and lactation length of goats on rangeland.

Characteristics of Garganica goat milk and Cacioricotta cheese

A survey was carried out in four Garganica flocks (FL1, FL2, FL3 and FL4), representative of different flock management, for achieving information on the hygienic and nutritional properties of Garganica goat milk and their impact on Cacioricotta cheese quality. Bulk milk was analyzed for pH, total protein, casein and whey protein, nitrogen fractions, fat, lactose and somatic cell count (SCC). Cacioricotta cheeses were manufactured from the milk of each flock according to a traditional protocol and analyzed for pH, moisture and NaCl contents, water activity, nitrogen fractions and fat content. Plasmin and plasminogen activity were detected in milk and cheese. Skim pooled milk and pH 4.6 soluble and insoluble fractions of the cheese were analyzed using alkaline Urea-PAGE. Garganica goat milk composition was in the range reported in literature for this breed. Somatic cell counts were higher ( P < 0.001) and protein and casein contents lower in the FL2 and the FL3 than in the FL1 and the FL4 flocks. No differences were found among flocks in the electrophoretic profile of milk. Marked changes were observed in cheese composition across flocks. A higher number of bands was detected in the Urea-PAGE of pH 4.6 soluble fractions from FL1 and FL4 cheeses compared to FL2 and FL3 cheeses together with a higher percentage of nitrogen fractions from casein degradation. SCC was correlated negatively with milk protein and casein contents and with cheese fat content. Marked changes observed in milk and cheese composition suggest that more definite rules of flock management and milk processing are required for improving and standardizing Cacioricotta cheese quality. Results also indicate that the control of sanitation of housing and milking procedures is critical for optimizing the nutritional and hygienic characteristics of Garganica goat milk and proteolysis occurring in Cacioricotta cheese during ripening.