The influence of diet and breed of cow on the efficiency of conversion of milk constituents to curd in cheese manufacture

The influence of diet on the efficiency of conversion of milk solids to cheese in two breeds of cow, viz. Jersey and Friesian, was examined. An increase in the efficiency of conversion of milk solids to cheese in Jersey milks produced from cows on winter diets as compared with a typical summer diet was shown to be associated with an improvement in the level of fat retention in curd. The difference in fat retention could to some extent be related to the overall fat content of the milk, the casein to fat ratio and the distribution in the size of the fat globules but these factors when considered collectively or independently could not adequately explain the differences in fat retention observed in these experiments. The level of fat retention in curd was not influenced by the thermal properties of the mik fat.     

Effects of breed,farm intensiveness,and cow productivity level on cheese-making ability predicted using infrared spectral data at the population level

Fourier-transform infrared (FTIR) spectra collected during milk recording schemes at population level can be used for predicting novel traits of interest for farm management, cows' genetic improvement, and milk payment systems. The aims of this study were as follows. (1) To predict cheese yield traits using FTIR spectra from routine milk recordings exploiting previously developed calibration equations. (2) To compare the predicted cheese-making abilities of different dairy and dual-purpose breeds. (3) To analyze the effects of herds' level of intensiveness (HL) and of the cow's level of productivity (CL). (4) To compare the patterns of predicted cheese yields with the patterns of milk composition in different breeds to discern the drivers of cheese-making efficiency. The major sources of variation of FTIR predictions of cheese yield ability (fresh cheese or cheese solids produced per unit milk) of individual milk samples were studied on 115,819 cows of 4 breeds (2 specialized dairy breeds, Holstein and Brown Swiss, and 2 dual-purpose breeds, Simmental and Alpine Grey) from 6,430 herds and exploiting 1,759,706 FTIR test-day spectra collected over 7 yr of milk sampling. Calibration equations used were previously developed on 1,264 individual laboratory model cheese procedures (cross-validation R² 0.85 and 0.95 for fresh and solids cheese yields, respectively). The linear model used for statistical analysis included the effects of parity, lactation stage, year of calving, month of sampling, HL, CL, breed of cow, and the interactions breed × HL and breed × CL. The HL and CL stratifications (5 classes each) were based on average daily secretion of milk net energy per cow. All effects were highly significant. The major conclusions were as follows. (1) The FTIR-based prediction of cheese yield of milk goes beyond the knowledge of fat and protein content, partially explaining differences in cheese-making ability in different cows, breeds and herds. (2) Differences in cheese yields of different breeds are only partially explained by milk fat and protein composition, and less productive breeds are characterized by a higher milk nutrient content as well as a higher recovery of nutrients in the cheese. (3) High-intensive herds not only produce much more milk, but the milk has a higher nutrient content and a higher cheese yield, whereas within herds, compared with less productive cows, the more productive cows have a much greater milk yield, milk with a greater content of fat but not of protein, and a moderate improvement in cheese yield, differing little from expectations based on milk composition. Finally, (4) the effects of HL and CL on milk quality and cheese-making ability are similar but not identical in different breeds, the less productive ones having some advantage in terms of cheese-making ability. We can obtain FTIR-based prediction of cheese yield from individual milk samples retrospectively at population level, which seems to go beyond the simple knowledge of milk composition, incorporating information on nutrient retention ability in cheese, with possible advantages for management of farms, genetic improvement of dairy cows, and milk payment systems.     

Composition, coagulation properties and Parmigiano-Reggiano cheese yield of Italian Brown and Italian Friesian herd milks

The authors report the results of a study aimed at the comparison of the basic chemical composition, the main protein fractions distribution, rennet coagulation properties and Parmigiano-Reggiano cheese yield of vat milk from Italian Brown and Italian Friesian herds. Parmigiano-Reggiano cheese factories which manufacture milk separately from Italian Brown herds and Italian Friesian herds were used in the study. Thirteen cheesemaking trials were performed at 10 different commercial cheese factories. The study was carried out from March to October 2003. For each cheesemaking trial in each factory, approximately 1100 kg milk from Italian Brown cows and from Italian Friesian cows were processed in parallel. The animals involved in the study came from farms with comparable management practices, size, location, number of lactation and days in milking. Each vat contained milk obtained by combining milk collected during the evening milking (partially skimmed milk by natural creaming) and the following morning milking (full-cream milk), from at least 2 dairy herds. Milk from Italian Brown cows is characterised by a higher casein content (27.1 v. 23.7 g/kg; P < or = 0.0001) than Italian Friesian cows' milk. Curd firming time (k20) of Italian Brown cows' milk was markedly lower than that of Italian Friesian cows' milk (6.6 v. 10.0 min; P < or = 0.001). This implies a higher rate of aggregation of para-casein micelles for Italian Brown cows' milk. The coagulum of Italian Brown cows' milk had better rheological properties and lower losses of fat in the cheese whey. Parmigiano-Reggiano cheese yield at 24 h was also higher for Italian Brown cows' milk, + 0.99 kg cheese for every 100 kg vat milk.     

Cheddar Cheese from Ultrafiltered Whole Milk Retentates in Industrial Cheese Making

Transporting whole milk retentates of ultrafiltration to a distant large industrial Cheddar cheese making site resulted in 16 lots of Cheddar cheese from vats containing 2,546 to 16,360 kg of cheese milk. Whole milk retentates concentrated by ultrafiltration to 4.5:1 were added to cheese milks to give mixtures concentrated 1.2:1 and 1.3:1 with approximately 20 and 30% more protein and fat, respectively, than in unsupplemented control whole milks or unsupplemented commercial reference milks.Gross composition of Cheddar cheese made from commercial reference, control, and retentate-supplemented milk generally showed no major differences. Yield increased in cheese made from retentate-supplemented milk. Yield efficiency per kilogram total solids rose in retentate cheese over controls but not among commercial reference, control, and retentate lots based on per kilogram fat or total protein. Milk components were higher in wheys from retentate cheeses, but loss of components per kilogram cheese obtained generally showed lower values in whey from retentate cheese.General quality of retentate Cheddar cheese was equal to that of reference unsupplemented commercial cheese and higher than unsupplemented control Cheddar cheeses. It appears technically feasible to ultrafilter milk at one site, such as the farm, collecting station, or specialized center, and transport it to an industrial site for Cheddar cheese making.     

Suitability of the milk of native breeds of cows from low‐input farms for cheese production,including rennet curd texture

The cheesemaking suitability of the milk of native cow breeds [Polish Red (RP) and White‐Backed (BG)] raised on low‐input farms was assessed. The milk of Polish Holstein‐Friesian cows raised in an intensive system constituted the reference group. Chemical composition, pH, rennet coagulation time, fat dispersion and curd texture were determined. The cows on the low‐input farms produced over 40% less milk, but with higher (P ≤ 0.01) fat content, shorter coagulation time by over 2 min and lower (P ≤ 0.05) fat dispersion. The curds from this milk were significantly springier, more cohesive and harder. The best milk indices were obtained for the RP cows.     

A systems comparison of once- versus twice-daily milking of pastured dairy cows

The objective of this study was to compare the effect of milking frequency (once vs. twice-daily milking) and breed (Holstein-Friesians vs. Jerseys) on milk and milk solids (MS; milk fat + milk protein), yield per cow, milk composition, somatic cell count and lactation length; cow body weight, body condition score, and reproductive performance over a 4-yr period. Total cow numbers in each herd were 30, 35, 36, and 42 for Holstein-Friesians milked once or twice daily, and Jerseys milked once or twice daily, respectively. Forty hectares of pasture were subdivided into 4 smaller pastures of 10 ha each. Stocking rates for the once-daily herds were 16.7% greater than the twice-daily herd in their respective breed. An increased stocking rate was chosen to achieve equal milk and MS per ha from the 2 milking frequencies. Annual milk, fat, protein, and lactose yields per cow were less for once-daily than for twice-daily milking. Interactions were detected between milking frequency and breed for annual milk, fat, protein, and lactose yields per cow, because Jerseys were relatively less affected by once-daily than by twice-daily milking than Holstein-Friesians. Holstein-Friesian cows milked once daily produced 31.2% less milk and 29.4% less MS per cow than their twice-daily counterparts. In contrast, Jersey cows milked once daily produced 22.1% less milk and 19.9% less MS per cow than their twice-daily counterparts. Milk per ha was 17.7 and 9% less for the once-daily Holstein-Friesians and once-daily Jersey herds, respectively, compared with their twice-daily counterparts, because the greater stocking rate for the once-daily herds did not fully compensate for the milk loss per cow. Milking once daily increased somatic cell count throughout the year in both breeds. Cows milked once daily conceived 3 d earlier, took 5 d less from calving to conception, and needed 11% fewer controlled internal drug release devices than those milked twice daily. Milking once daily is a viable milking option for New Zealand farmers who are prepared to trade-off loss of MS income for increased time to accomplish other non-milking activities.     

Additive and nonadditive genetic effects on milk production in dairy cattle: evidence for major individual heterosis

Coefficients for individual and maternal breed composition and the expected contributions of individual and maternal heterosis and breed source of cytoplasm were assigned to 42,554 primiparous Holstein-Friesian, Jersey, and crossbred cows. The individual additive genetic breed effect influenced all milk production traits. Highly significant maternal additive genetic breed effects equivalent to 3% of the mean were identified for milk yield and milk fat percentage. Individual heterosis was highly significant for milk yield and milk fat yield. A primiparous first cross cow produced 6.1% more milk and 7.2% more milk fat than the average of straightbred cows of both breeds. For milk fat yield, the individual heterosis effect was higher than the individual additive genetic breed difference between Jersey and Holstein-Friesian. A small negative maternal heterosis and a small effect of breed source of cytoplasm were estimated for milk fat percentage. Results suggest that individual heterosis is a major genetic effect for milk yield and milk fat yield. This heterosis could be utilized through a stratified breeding scheme in which high genetic merit nucleus herds maintain genetic progress in the two straightbred populations, and commercial dairy herds employ a rotational cross-breeding scheme to take advantage of both the additive genetic progress and nonadditive genetic effects.     

Effect of goat milk composition on cheesemaking traits and daily cheese production

Cheese yield is strongly influenced by the composition of milk, especially fat and protein contents, and by the efficiency of the recovery of each milk component in the curd. The real effect of milk composition on cheesemaking ability of goat milk is still unknown. The aims of this study were to quantify the effects of milk composition; namely, fat, protein, and casein contents, on milk nutrient recovery in the curd, cheese yield, and average daily yield. Individual milk samples were collected from 560 goats of 6 different breeds. Each sample was analyzed in duplicate using the 9-laboratory milk cheesemaking assessment, a laboratory method that mimicked cheesemaking procedures, with milk heating, rennet addition, coagulation, curd cutting, and draining. Data were submitted to statistical analysis; results showed that the increase of milk fat content was associated with a large improvement of cheese yield because of the higher recovery of all milk nutrients in the curd, and thus a higher individual daily cheese yield. The increase of milk protein content affected the recovery of fat, total solids, and energy in the curd. Casein number, calculated as casein-to-protein ratio, did not affect protein recovery but strongly influenced the recovery of fat, showing a curvilinear pattern and the most favorable data for the intermediate values of casein number. In conclusion, increased fat and protein contents in the milk had an effect on cheese yield not only for the greater quantity of nutrients available but also for the improved efficiency of the recovery in the curd of all nutrients. These results are useful to improve knowledge on cheesemaking processes in the caprine dairy industry.     

The manufacture of miniature Cheddar-type cheeses from milks with different fat globule size distributions

A novel 2-stage gravity separation scheme was developed for fractionation of raw, whole bovine milk into fractions enriched in small (SFG) or large (LFG) fat globules. The volume mean diameter of fat globules in SFG, LFG or control (CTRL) milk was 3.45, 4.68 and 3.58 microm, respectively. The maximum in storage modulus (index of firmness) decreased with increasing fat globule size for rennet-induced gels formed from SFG, LFG or CTRL milks. Miniature (20 g) Cheddar cheeses were manufactured using each of the 3 milks. There were no significant (P > 0.05) differences in the pH, moisture and fat in dry matter levels between cheeses made using any of the 3 milks, however, the fat content of the cheese made using SFG milk was approximately 1% lower than that of cheese made using LFG or CTRL milk in each of the 2 trials. Image analysis of confocal scanning laser micrographs of the cheeses illustrated that the star volume of fat globules in the cheeses decreased significantly (P < or = 0.05) as the size of fat globules in the milks used for cheesemaking was reduced. This indicates that it is possible to manipulate the size distribution of fat globules in Cheddar cheese by adjusting the fat globule size distribution of the milk used for cheese-making. The concentration of free fatty acids (FFA) increased in all cheeses during ripening. At 120 d of ripening, the concentration of FFA varied significantly (P < or = 0.05 and P < or = 0.001 for trials 1 and 2, respectively) with fat globule size, with cheeses made in trial 2 from LFG, SFG or CTRL milks having total FFA levels of 3391, 2820 and 2612 mg/kg cheese, respectively.     

Comparison of fatty acid content of milk from Jersey and Holstein cows consuming pasture or a total mixed ration.

Holstein (n = 19) and Jersey (n = 18) cows were used to study effects of two feeding systems on fatty acid composition of milk. Confinement cows were fed a total mixed ration with corn silage and alfalfa silage and pastured cows grazed a crabgrass (90%) and clover (10%) pasture and were allowed 5.5 kg of grain per head daily. Two milk samples were collected from each cow at morning and afternoon milkings 1 d each week for four consecutive weeks in June and July 1998. One set of milk samples was analyzed to determine fatty acid composition, and the second set was used for crude protein and total fat analyses. Data were analyzed by the general linear models procedure of SAS, using a split-plot model with breed, treatment, and breed x treatment as main effects and time of sampling and week as subplot effects along with appropriate interactions. Milk from pastured cows was higher than milk from confinement cows for the cis-9, trans-11 octadecadienoic acid isomer of conjugated linoleic acid (CLA). Also, milk from Holsteins was higher than milk from Jerseys for C16:1, C18:1, and CLA and lower than Jerseys for C6:0, C8:0, C10:0, C12:0, and C14:0. Several treatment x week interactions existed, but main effects were still important; for example, proportions of CLA in milk of grazed cows were relatively constant across weeks (0.66, 0.64, 0.64, and 0.69% +/- 0.02%, respectively), but the CLA in milk of confinement cows increased in wk 4 (0.35, 0.31, 0.31, and 0.48% +/- 0.02% for wk 1 to 4, respectively). There are potentially important differences in fatty acid composition of milk from cows consuming a warm season pasture species compared with milk from cows consuming a total mixed ration, as well as differences between Holstein and Jersey breeds.     

Cheese yield,cheesemaking efficiency,and daily production of 6 breeds of goats

Little is known about the complex process of cheesemaking at the individual level of dairy goats because of the difficulties of producing a high number of model cheeses. The objectives of this work were (1) to study the cheesemaking ability of goat milk; (2) to investigate the variability of cheesemaking-related traits among different farms; (3) to assess the effects of stage of lactation and parity; and (4) to compare 6 breeds of goat (Saanen and Camosciata delle Alpi for the Alpine type; Murciano-Granadina, Maltese, Sarda and Sarda Primitiva for the Mediterranean type) for their cheesemaking ability. For each goat (n = 560) we studied (1) 8 milk quality traits (fat, protein, total solids, casein, lactose, pH, somatic cell score, and bacterial count); (2) 4 milk nutrient recovery traits (fat, protein, total solids, and energy) in curd; (3) 3 actual cheese yield traits (fresh cheese, cheese solids, and cheese water); (4) 2 theoretical cheese yield values (fresh cheese and cheese solids) and the related cheesemaking efficiencies; and (5) daily milk yield and 3 daily cheese yield traits (fresh cheese, cheese solids, and water retained in the curd). With respect to individual animal factors, farm was not particularly important for recovery traits or actual and theoretical cheese yield and estimates of efficiency, whereas it highly influenced daily productions. Parity of goats influenced daily cheese production, whereas DIM slightly affected recovery as well as percent and daily cheese yield traits. Breed was the most important source of variation for almost all cheesemaking traits. Compared with those of Alpine type, the 4 Mediterranean breeds had, on average, lower daily milk and cheese productions, greater actual and theoretical cheese yield, and higher recovery of nutrients in the curd. Among Alpine type, Camosciata delle Alpi was characterized by greater nutrients recovery than Saanen. Within the 4 Mediterranean types, the 3 Italians produced much less milk per day, with much more fat and protein and greater recovery traits than the Murciano-Granadina, resulting in greater actual cheese yield. Within the Italian breeds, milk from Sarda and Sarda Primitiva was characterized by lower daily yields, higher protein and fat content, and greater recoveries of nutrients than Maltese goats. These results confirmed the potential of goat milk for cheese production and could be useful to give new possibilities and direction in breeding programs.     

Estimation of genetic parameters and individual and maternal breed,heterosis, and recombination loss effects for production and fertility traits of spring-calved cows milked once daily or twice daily in New Zealand

The objectives of this study were to estimate genetic parameters and individual and maternal breed, heterosis, and recombination loss effects for milk production and fertility traits of Holstein Friesian (F), Jersey (J), and crossbred Holstein Friesian and Jersey (F × J) cows milked once daily (OAD) or twice daily (TAD) in New Zealand. Data on 278,776 lactations from 30,217 OAD and 170,680 TAD milking cows across 644 spring-calving herds were available. Genetic parameters and individual and maternal breed, heterosis, and recombination loss estimates were obtained from univariate animal models. Heritability and repeatability estimates for milk production, milk composition, and fertility traits were consistent across the milking frequencies. Heritability estimates for yields of milk, fat, protein, and lactose varied between 0.21 and 0.29 in OAD and TAD. Heritability estimates for fertility traits ranged from 0.01 to 0.08 in both populations, and estimates were slightly greater in TAD than OAD milking cows. In both milking populations, individual breed effects for yields were in favor of F cows; however, maternal breed effects for yields were in favor of J dams. Jersey cows were more fertile than the F cows in both milking populations, but maternal breed effects for fertility traits were in favor of F dams. Individual heterosis effects were favorable for all traits and were consistent across milking regimens. Crossbred F × J cows had significantly shorter intervals from start of mating to first service and from start of mating to conception, and a higher proportion of 3-wk submission, 3-wk in calf, and 3-wk calving relative to the average of purebred F and J cows. Recombination loss effects were not always unfavorable for production and fertility traits, but most estimates were small with larger standard errors. Favorable maternal heterosis effects were associated with production traits in both milking systems, but maternal heterosis effects were less likely to influence reproductive performance.     

Effects of breed,feeding system,and lactation stage on milk fat characteristics and spontaneous lipolysis in dairy cows

Spontaneous lipolysis (SL) is an enzymatic reaction that leads to a release of fatty acids that can modify technological and sensory properties of milk and milk products. However, few studies have been done to assess the effect of feeding systems (FS) and breed on SL. Most of them were conducted in the 1980s and are not fully representative of cattle today. No previous study investigated the effect of cow breed at the whole-lactation scale. Thus, a trial was carried out to study the effects of 2 FS (high- and low-input FS) with 2 breeds [Holstein (HO) and Normande (NO)] during 1 entire lactation. Sixty-three cows were followed throughout 1 lactation. Cows were divided into 4 groups according to their breed and their FS. The high FS (HFS) consisted of a high-energy diet (in winter, corn silage with 30% concentrate; otherwise, pasture with 4 kg/d of concentrate) and the low FS (LFS) consisted of a low-energy diet (in winter, conserved grass with no concentrate; otherwise, pasture with no concentrate). The cows calved between January and March. Individual milk samples were collected every month from both morning and evening milkings for fat, protein, milk fat globule size, major fatty acids and proteins profiles, and SL determinations. Data were analyzed using the mixed procedure of SAS. The SL was higher in evening milks compared with morning milks. In early lactation, in evening milks, SL was higher in LFS than in HFS. No difference was shown according to the FS in mid and late lactation. Pasture was associated with low SL rate in mid lactation. The NO cows were less susceptible to SL during the entire lactation than HO cows. Finally, early and late lactation periods were identified as being more susceptible to SL, but this depended on breed and FS. During early lactation, HO cows and LFS were associated with higher levels of SL, particularly in evening milks, and, during late lactation, HO cows were associated with higher levels of SL. No intertreatment or intercow correlations (coefficient of determination <0.16) were found between SL, milk fat and protein contents, milk production, milk fat globule size, proportion of fatty acids and proteins, body condition, and weight during the entire lactation. Effects of breed, FS, and lactation stage were clearly identified and quantified. Causal mechanisms might involve energy balance and circadian secretion of milk fat globule components.     

Managing diet quality for cheddar cheese manufacturing milk. 2. Pasture v. grain supplements.

The effects of supplementing a basal diet of silage and hay with increasing amounts of harvested spring pasture, or with lupin and wheat, on the composition of milk and the consequent effects on cheese composition and yield were investigated in an indoor feeding study. Milk was collected from five groups of eight cows in mid lactation offered different diets and manufactured into Cheddar cheese on a pilot scale. Milk from cows given the lupin-wheat (LW) and the high pasture level (HP) diets produced low moisture cheese. Cheese produced with milk from cows given the control diet was high in moisture content compared with that made with milk from cows offered the LW diet. Cheese yields from the milk of cows offered the HP and LW diets were greater than from the milk of cows on the control diet, and were associated with the higher casein concentrations of these milks. Casein number was higher in milk from diets supplemented with pasture but was not an indicator of the functional properties of milk that affected cheese moisture. The proportion of beta-casein in milk from cows offered the HP diet was higher and that of gamma-casein lower than in milk from cows given the LW supplement, although cheese moisture content was similar with both diets. Milk from cows offered the HP diet had a greater inorganic P concentration than that from cows given the LW diet, although the dietary intake of P was higher for the LW diet. The significance of the effect of dietary P intake on the concentration of inorganic P in milk and hence its suitability for cheesemaking was apparent when dietary P intake was low, as shown in milk produced by cows offered the control diet.     

The effects of breed and other factors on the composition and freezing point of cow’s milk in Poland

The milk obtained from six cow breeds (Polish Holstein‐Friesian Black‐White and Red‐White, Simmental, Jersey, Polish Red and Polish Black‐White) managed in the Lubelskie region and the Bieszczady Mountains was analysed. A total of 3618 milk samples collected between 2005 and 2008 were evaluated for the total solids content, percentage concentrations of fat, protein and lactose, and the freezing point: the mean milk freezing point was ?0.538°C. The freezing point of milk was influenced by breed, successive lactations, lactation stage and the geographic region. In milk with a high urea concentration (over 300 mg/L), the increased apparent protein level caused a decrease in the milk freezing point values. The combined influence of geographic region and production season showed significant interactions for daily milk yield and total solids content (P < 0.01) and the milk freezing point (P < 0.05).     

Short communication: milk fat composition of 4 cattle breeds in the Netherlands

Milk fatty acid (FA) composition was compared among 4 cattle breeds in the Netherlands: Dutch Friesian (DF; 47 animals/3 farms), Meuse-Rhine-Yssel (MRY; 52/3), Groningen White Headed (GWH; 45/3), and Jersey (JER; 46/3). Each cow was sampled once between December 2008 and March 2009 during the indoor housing season, and samples were analyzed using gas chromatography. Significant breed differences were found for all traits including fat and protein contents, 13 major individual FA, 9 groups of FA, and 5 indices. The saturated fatty acid proportion, which is supposed to be unfavorable for human health, was smaller for GWH (68.9%) compared with DF (74.1%), MRY (72.3%), and JER (74.3%) breeds. The proportion of conjugated linoleic acid and the unsaturation index, which are associated positively with human health, were both highest for GWH. Differences in milk fat composition can be used in strategies to breed for milk with a FA profile more favorable for human health. Our results support the relevance of safeguarding the local Dutch breeds.     

A comparison of the environmental impact of Jersey compared with Holstein milk for cheese production

The objective of this study was to compare the environmental impact of Jersey or Holstein milk production sufficient to yield 500,000 t of cheese (equivalent cheese yield) both with and without recombinant bovine somatotropin use. The deterministic model used 2009 DairyMetrics (Dairy Records Management Systems, Raleigh, NC) population data for milk yield and composition (Jersey: 20.9 kg/d, 4.8% fat, 3.7% protein; Holstein: 29.1 kg/d, 3.8% fat, 3.1% protein), age at first calving, calving interval, and culling rate. Each population contained lactating and dry cows, bulls, and herd replacements for which rations were formulated according to DairyPro (Agricultural Modeling and Training Systems, Cornell, Ithaca, NY) at breed-appropriate body weights (BW), with mature cows weighing 454 kg (Jersey) or 680 kg (Holstein). Resource inputs included feedstuffs, water, land, fertilizers, and fossil fuels. Waste outputs included manure and greenhouse gas emissions. Cheese yield (kg) was calculated according to the Van Slyke equation. A yield of 500,000 t of cheese required 4.94 billion kg of Holstein milk compared with 3.99 billion kg of Jersey milk-a direct consequence of differences in milk nutrient density (fat and protein contents) between the 2 populations. The reduced daily milk yield of Jersey cows increased the population size required to supply sufficient milk for the required cheese yield, but the differential in BW between the Jersey and Holstein breeds reduced the body mass of the Jersey population by 125×10(3) t. Consequently, the population energy requirement was reduced by 7,177×10(6) MJ, water use by 252×10(9) L, and cropland use by 97.5×10(3) ha per 500,000 t of cheese yield. Nitrogen and phosphorus excretion were reduced by 17,234 and 1,492 t, respectively, through the use of Jersey milk to yield 500,000 t of Cheddar cheese. The carbon footprint was reduced by 1,662×10(3) t of CO(2)-equivalents per 500,000 t of cheese in Jersey cows compared with Holsteins. Use of recombinant bovine somatotropin reduced resource use and waste output in supplemented populations, with decreases in carbon footprint equivalent to 10.0% (Jersey) and 7.5% (Holstein) compared with nonsupplemented populations. The interaction between milk nutrient density and BW demonstrated by the Jersey population overcame the reduced daily milk yield, thus reducing resource use and environmental impact. This reduction was achieved through 2 mechanisms: diluting population maintenance overhead through improved milk nutrient density and reducing maintenance overhead through a reduction in productive and nonproductive body mass within the population.     

Responses of milk fat composition to dietary fat or nonstructural carbohydrates in Holstein and Jersey cows

Milk fat from Jersey cows contains less oleic acid (cis-C18:1) and more short- and medium-chain fatty acids than does milk fat from Holstein cows. The objective of this experiment was to determine responses in milk fat composition when Jersey and Holstein cows were fed diets either high (37% of dry matter) or low (27% of dry matter) in content of nonstructural carbohydrates (NSC) and supplemented with either 0 or 2.5% (of dry matter) of a mostly saturated fat source. Four Holstein cows and four Jersey cows were used in a Latin square design with 28-d periods; diets were in a 2 x 2 factorial arrangement. Fat supplementation decreased contents of fatty acids synthesized de novo within the mammary gland and increased contents of C18:0 and cis-C18:1. Low-NSC diets tended to increase C16:0 and to decrease C18:0, cis-C18:1, and C18:3. Despite the differences in fatty acid composition between breeds, both breeds generally responded similarly to dietary treatments. An interaction of breed and fat indicated that the content of cis-C18:1 in milk fat was increased more by supplemental fat in Holsteins than in Jerseys. Interactions of breed x fat and breed x carbohydrate type showed that the ratio of cis-C18:1 to C18:0 decreased when Jerseys were supplemented with fat but increased for Holsteins, and decreased when Jerseys were fed the low-NSC diet but increased when Holsteins were fed low NSC. The data are consistent with the hypothesis (Beaulieu and Palmquist, 1995, J. Dairy Sci. 78:1336-1344) that mammary activity of stearoyl-coenzyme A desaturase is lower in Jerseys than in Holsteins.     

Whole Milk Reverse Osmosis Retentates for Cheddar Cheese Manufacture: Cheese Composition and Yield

The impact of concentrating whole milk by reverse osmosis prior to Cheddar cheese making was studied. Heat treated, standardized, whole milk was reduced in volume by 0, 5, 10, 15, and 20% prior to Cheddar cheese manufacture. Milk solids at various milk volume reductions were 11.98, 12.88, 13.27, 14.17, and 15.05%, respectively. Permeates contained only traces of organic matter and would not create a significant by-product handling problem for a cheese plant. Solids content of the whey from cheese making increased with increasing milk concentration. Proximate compositions of reverse osmosis cheeses were comparable to control cheeses. Fat losses decreased, and fat retained in the cheese increased with increasing milk solids concentration. Improved fat recovery in the cheese was related to the amount of mechanical homogenization of milk fat during the concentration process. Actual, composition adjusted, and theoretical cheese yields were determined. Increased retention of whey solids and improved fat recovery gave cheese yield increases of 2 to 3% above expected theoretical yields at 20% milk volume reduction. Water removal from whole milk prior to Cheddar cheese manufacture gave increased productivity and cheese yield without requiring different cheese-making equipment or manufacturing procedures.     

Variation in fatty acid contents of milk and milk fat within and across breeds

The aim of this research was to study the potential for selection of cows with a higher nutritional quality of milk fat by studying the differences in fatty acid profiles within and across the following breeds: Dual Purpose Belgian Blue, Holstein-Friesian, Jersey, Montbeliarde, and non-Holstein Meuse-Rhine-Yssel type Red and White. Six hundred milk samples from 275 animals were taken from 7 herds. Several types of fatty acids in milk and milk fat were quantified using mid-infrared spectrometry and previously obtained calibration equations. Statistical analyses were made using a mixed linear model with a random animal effect. The variance components were estimated by using REML. Results showed breed differences for the fatty acid profile. The repeatability estimate obtained in the present study may suggest the existence of moderate additive genetic variance for the fatty acid profile within each breed. Results also indicated variation for each analyzed milk component in the whole cow population studied. Genetic improvement of the nutritional quality of milk fat based on fatty acid profiles might be possible, and further research and development are warranted.