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Bovine milk, is considered within the human diet, as one of the most complete foods, because its high contents of essential amino acids and proteins, reason why Hernández et al.(2011), argue the importance that in the majority of countries of the hemisphere is given to the increase of productive volumes of this food, as part of the food and nutritional safety of its population.
To cover the demands of milk in Cuba, it was worked since the late 60's, in the conformation of different breeds that as primary characteristics express high performance in dairy production, in addition to rusticity to tropical conditions, good body development in grazing conditions and high resistance to diseases; the Siboney de Cuba breed, is one of the main dairy exponents obtained from this program in the country.
For Ponce et al. (2005), the good quality of milk is a necessity, regardless of production, when guarantee a safer diet for the family and consumers in general, a longer life in the sale of raw milk, better handmade products that use this product as raw material, in addition to better processes and stability in the sale of the industry.
The world trend in dairy livestock is projected to increase in production per cow and achieve higher yields in the parameters of milk quality, mainly in proteins and non-fat solids, so its quality is linked to specific standards about production conditions, commonly accepted at national and international level of mandatory compliance.
Researches carried out by different authors such as Gallardo (2003), Campabadal (2013), Gabbi et al.(2013) refers as factors which affect the quality of milk to: genetics, age, health status and lactation period of the cow, as well as milking management and season of the year; although all agree in affirming that the nutritional factors are the main responsible, not only to increase milk production, but to change its chemical composition, especially fat content.
The importance of knowing the parameters of milk quality produced in livestock systems, makes possible the decision making to attenuate the affectations in the management of quality in the whole agro-industrial chain (Rodríguez et al, 2015). These parameters according to Ponce et al.(2004), are determined by two basic aspects: the chemical composition and the hygienic-sanitary level maintained in the obtaining process, which defines its nutritional, industrial and food safety potential, so the milk that is for human consumption, must contain low number of saprophytic microorganisms, absence or very low content of pathogenic microorganisms and absence or minimum content of drug residues and contaminants.
In Cuba, according to Ponce et al.(2015), the reports on bacteriological quality in raw milk are very limited and consider the reports poor from the quantitative point of view in raw milk, despite being common at international level that the payment is made through the counting of microorganisms as a hygienic indicator in milk production.
The study of the performance of physical-chemical indicators that make up cow's milk, as well as the alterations that occur in the mammary gland during lactation and the existing relation between product quality standards and metabolic disorders that can affect it, gather increasing interest among researchers and producers, in order to avoid undesirable changes in the normality parameters established for the payment to the producer and the fulfillment of the high quality requirement of the raw material demanded by the dairy industry for better yields in the products.
Based on this problem related to the demands faced by the producer in relation to the quality of the milk it produces, the objective of this study was to evaluate in a period of 5 months the performance of the physical-chemical and microbiological parameters of Siboney de Cuba cows milk, obtained in the dairy-60"La Jibara” from the Empresa Pecuaria Genética (E.P.G.) "Camilo Cienfuegos".
Materials and Methods
The study was developed under livestock production areas of dairy -60 "La Jíbara", belonging to Unidad Empresarial de Base (U.E.B.) Corralito, from the E.P.G. "Camilo Cienfuegos", located in Consolación del Sur municipality, Pinar del Río province, Cuba. The samples collected were taken from 30 clinically healthy lactating females from Siboney de Cuba breed (randomLy divided into 2 groups of 15 individuals each) that presented different lactation periods (from 25 to 180 days), with live weights between 385 and 440 kg and average body condition 3.
The samplings were performed indistinctly at biweekly intervals (2 samplings/month to each group). They began at the beginning of September 2016 and extended until the beginning of January 2017, with the purpose of determining physical-chemical and microbiological parameters of the individual milk production in the evaluated period. The samples were always taken in the afternoon milking.
For the collection of milk sterile 500 mL bottles were used. Once filled, were sealed, identified and placed in rows at a temperature of 4 to 6 ºC. Later they were transferred to the Laboratorio de Análisis Químico "El Canal", belonging to the enterprise for their analysis. Between the collection and the analysis, an average of 3.5 hrs passed.
The collected milk was determined: density (g/mL) and temperature (ºC) by Quevenne lactodensimeter. The traces or mastitis (CMT) were calculated by the titration method using CENMAST. The methylene blue reduction time (MBRT) (h: min) and fat (g/L) were determined according to the Gerber method. The non-fat solids (NFS) (g/L) by the formula NFS = (Density/4) + (fat/5) + 0.14 and totals solids (TS) (%) through the formula TS = Fat + NFS. NC: ISO: 2446: 2003 (Fat), NC: 282: ISO: 2006 (MBRT) and NC: 6731: ISO: 2001 (TS and NFS).
During the experimental period , the cows under study remained in a total area of 85.92 ha., with feeding system based on rotational grazing, approximately 12 hours a day, in areas where botanical species predominated, Brachiaria hybrid (Mulato I) cv CIAT 36061 (4.9 ha); Pannicum maximum (Guinea likoni) (27.3 ha); Cynodon nlemfuencis (Star grass) (9.7 ha); Pennisetum purpureum (cv. Cuba CT-115) (11.2 ha.); Moringa oleifera, Titonia diversifolia and Morus alba (Protein Plants) (4.4 ha); Natural grass (19.42 ha); Saccharum officinarum L (Sugar cane) (4.0 ha) and silvopastoral system (Guinea likoni - Leucaena leucocephala) (5.0 ha). Irrigation was not used, only organic fertilization.
In the shade buildings or during the milking, fresh mixtures were offered, elaborated indistinctly according to availability, based on sugarcane (milled with more than 365 days established) or Cuba CT-115 (with around 150 days); mixed with Morera. The cut age in both cases was 90 days. For its grinding, a JF-50 mill, made in Brazil, was used. The milling made it possible to obtain particles for the sugarcane of approximately 2.0 cm in size and 1.3 cm for those of CT-115, while for the protein plants they reached between 0.5 and 1.0 cm in size.
The cows were milked twice a day, and during each milking, they were offered 1.5 kg. of mixed food that contained 200 grams of criollo concentrate per each kilogram of fresh mixtures, plus 0.45 kg of concentrate for those cows that produced more than 3 liters of milk/daily.
For the laboratory analyzes, the procedures established by the Cuban Standards were followed. The results obtained, regarding the quality of milk, were compared with the parameters fitted by the Cuban norm NC: 448-2006 illustrated here:
(±5)* indicates that the temperature cna fluctuate in ranges of 5 °C due to excess of defect at 15 °C
For the statistical analysis of the physical-chemical and microbiological parameters obtained, the simple statisticians of position (mean) and dispersion (standard deviation) were used, in addition to simple ANOVA. Duncan (1955) test was used to determine differences in physical -chemical performance of the milk, according to ranges of lactation days during the sampling. All the analysis were performed using the statistical package InfoStat version 2012 (Di Rienzo et al, 2012).
For the calculation of the estimation of prevalence of subclinical mastitis (PSM) the Ponce et al.(2005) formula was used:
Results and Discussion
The means of the physical-chemical and microbiological requirements of the evaluated milk are showed in table 1.
The average values recorded in temperature, density, fat, total solids (TS) and non-fat solids (NFS) are in the permitted ranges, as established by the Cuban standard NC 448: 2006. The methylene blue reduction time (MBRT) performed below what was established (5.30 h).
The means obtained during the study shows that fat, as an average reached 3.24 % of 3.20 % that establishes the standard. Like the TS and NFS, with 11.46 % and 8.24 g/L respectively, higher than what is established. These results are similar to those reported a few decades earlier by Ponce (1999,cit. by Castillo 2009) , who reported for fat values of 4.01 %, for TS 12.75 % and for NFS 8.74 g/L in samples taken from Siboney de Cuba females in production.
The density values found for the different samples were in the range of: 1.029 - 1.030 g/mL at 18.60 °C of temperature, which shows an adequate relation between the non-fatty solids and the water in the milk. This result is of great importance because of its influence from the economic point of view on the commercial price of milk, when not indicating adulteration by water and to be in the limit range allowed by the Cuban standard (NC: 448: 2006). Ponce et al.(2005); Toledo et al.(2010) and Rodríguez et al.(2015) agree that milk weighing 1028 g/mL or less will be penalized, due to its low density. This negatively affects the economies of the producer and to the dairy industrial plant.
In the MBRT test, 60 % of the values of the sampled milk were classified as grade (B) considered as acceptable according to the NC: 282: 2006. Only 40 % classified in grade C. These results are related with the use of good management practices and the control of hygienic-sanitary measures, mainly in the cleaning and disinfection of the mechanized milking equipment and the actions carried out in the milking routine in the productive unit (Dairy-60 “La Jibara”), which influences on the milk quality. The hygienic-sanitary quality of the highest percentage of raw milk obtained fulfill with the requirements of Buenas Prácticas Lecheras established in Programa Integral para la Mejora de la Producción y Calidad de la Leche (PROCAL) according to Ponce et al.(2004).
The concentration of fat in milk reached values of 3.24 %, higher in 0.04 % with respect to the minimum range established by the Cuban Standard (NC: 448: 2006), although below that established by Hernández and Ponce (2000) for the Siboney de Cuba herds (4.28 %). These results can be associated to the presence in the sample collection of a group of cows with lactations between 60 and 200 d (18 heads). The fat content of milk they produce is lower than that of those cows, whose lactation is at beginning or more advanced.
Another of the causes that could influence, are the variations in the climatological factors of the end of the rainy season (May 15 to October 31) and the beginning of the dry season (November 1 to May 14). In this season there were changes in the quality and quantity of the food received by the cow because of problems associated with the lack of availability of food for cattle during the dry season in Cuba. Multiple consequences are derive from these problems, related to the low productive performance in the herds, which in turn affects a consequent decrease in the percentages of fat and total solids, due to the existing proportional relation. Similar arguments to these reported Hernández and Ponce (2006) and Sánchez et al. (1996 cit. by Castillo 2009).
The milk productions that contain low fat content, according to Castillo (2009), represents a bromatological problem for the consumer, join to the economic effects it brings to the pasteurizing plant, since the yields of milk cream are reduced at the standardization moment. According to Casado and García (1985) and Alais (2003), milk fat is considered one of the parameters that vary in higher proportion.
Smith (1968) stated that one of the factors that affect the percentage of fat and non-fat solids in milk is the feeding. In this it influences the quantity and quality of the fiber supplied, as well as the proportion of the forage in the concentrate, because according to Bunting (2004) the percentage of milk fat affects the site and the degradation rate of starch, composition of fatty acids and in the case of protected fats, the degree of protection with respect to the rumen and its digestibility.
The maturity state of the ground forage and the particle size, when offered in shade buildings or during milking, can be considered a factor that produces changes in the products of ruminal fermentation, with the consequent increase of propionate and the reduction of acetate, which brings with it the decrease in the percentage of milk fat. Similar arguments refers Morales (2010), who state that finely ground forage plays an important role in maintaining or increasing the milk fat content.
Make an adequate balance of the ration, in terms of covering the nutritional requirements to produce milk, directly affects the results to expect. According to Ruíz-Albarrán (2012), not fulfilling with the protein and energy requirements in the rumen of the cow in production, becomes a limitation for milk production. Hence the need for each productive unit to have its food self-sufficiency (FSS). Therefore, that it has the necessary food base, in quantity and quality, for its herd feeding, which coincides with that of proposed by Díaz et al. (2013), Interián et al. (2013) and Alonso (2015).
The average total solids (11.46%) was very similar to the minimum value established by the referred standard (11.4 %), which could be a consequence of changes in the components of cows feeding, if it is taking into account that the sampling passed in the last weeks of the rainy period, and at the beginning of the dry season. In this period the base grass established in the unit begins to be scarce, with the consequent decrease in its quality and bromatological composition, which affects the nutritional requirements of the cow in production, as Alonso (2015) points out.
Studies conducted by Campabadal (2013) show that the decrease in total solids can affect the percentage of fat by the acetate: propionate ratio, present in an inverse proportion between milk production and solids percentage. Hence the importance of the producer knowing the impact of sudden changes has in the cow’s milk production. When this happens, it is impossible to guarantee a product with the percent of total solids that the Siboney de Cuba breed is capable of producing.
The means obtained by non-fat solids (8.24 g/L) were similar to the minimum values established by the Cuban Standard (8.20 g/L). It is estimated that these results are related to the causes mentioned above, which have to do with changes in the availability and quality of food, although they could affect others, such as the sampling and the lactation period in which the cow is , because in the group selected for the experiment there were cows with different days in lactation. These causes correspond to what Álvarez et al. (2012) and Cervantes et al. (2013), who also consider that genetics, age, health status, management at milking and the season of the year are variables that affect the milk quality.
Gallardo (2003), Morales (2010), Campabadal (2013) and Gabbi et al. (2013) coincidentally argue that, in nutrition and feeding, the ratio forage: concentrate, type of forage, fiber quality (maturity, fiber content), particle size or chopped forage, type of concentrate, dietary protein, fat addition and additives, are the main responsible, not only to increase milk production, but to modify its chemical composition and its variability, especially the fat content.
Table 2 shows the results of the mastitis diagnosis, performed on the samples by the California test, according to the Cuban Standard (NC: 118: 2001).
The results show that 11.33% of the collected samples were evident positive (++), while 24 % were weak positive (+) to subclinical mastitis, according to the classification by California Mastitis Test (CMT).
The percentage of samples analyzed, which is evident positive (++) to the presence of bovine mastitis in the primary link of production, evidences that there are sanitary violations in the productive unit Dairy-60 “La Jibara”), related to compliance in the technological discipline that establishes the milking routine. This requires the separation for prophylactic treatment of cows in production with infected quaters, which agrees with that referred by Ponce et al. (2015).
The results with traces, weak positive, and evident positive, described in table 2, were applied the formula for the prevalence of subclinical mastitis (PSM) of Ponce et al. (2005):
The PSM assessment, according to the number of individuals considered positive or negative to the analysis, is described in table 3.
The percent of samples with PSM among the cows in production evaluated can be considered high (66 %), since of the total samples collected (150) only 34 % were negative when performing the California Mastitis Test (CMT). These results indicate how compromised the quality of the milk collected during the evaluated period was found from a microbiological point of view.
The results described above correspond to those referred by Córdova (2017), when reporting for tropical conditions that of every 100 cows in milk production, it is possible to find between 60 and 76 females with affectations of subclinical mastitis (not observed with the naked eye) , to more than 50 % of the udder quarters of milking cows.
This indicates the need to performed an epizootiological study in the unit to determine the causes that can affect the subclinical mastitis problems, the degree of traces reaction of the CMT: general hygiene and milking equipment, labor stability of the milkers, correct realization of the milking routine, constant review and separation of those positive animals evident to the test, located at the end of the milking of their group. Milking should be done thoroughly, two or three times a day, without applying antibiotic treatment to correct the cause, and minimize the costly losses that occur due to the milk quality.
The CMT analyzes provide the breeder with a reliable prediction, being able to detect early cases of subclinical mastitis and take corrective measures before the disease becomes clinical, which correspond to what was proposed by De la Cruz (2011).
To obtain milk in this unit, mechanized milking is used with a technology that has been in operation for many years. Although this technology has received minimal repairs, capital repairs have not been possible. This implies that the quality of pulsator, teat cup liners, and the general functioning of the milking equipment had difficulties, which makes possible the appearance of over- milking or sub- milking problems, which prevent the total content of the udder from being emptied, which causes productive losses; in addition to the consequent release of somatic cells that cause inflammation in the nipple canal and the appearance of subclinical mastitis disorder in the female. This corresponds to what was described by Novoa (2003), Ponce (2004), Cuayla (2010) and Coronel et al. (2011).
In the statistical analysis of the physical-chemical parameters of milk, according to the range of lactation days during the study (table 4), highly significant differences were found (p <0.0001), only for fat and TS in milk of cows in production.
Table 4 Result of the physical-chemical parameters of milk according to the range of lactation days passes during the study of the cows in production
a, b, c, d, eDifferent lettres in the same rows differs to P<0.05 according to Duncan (1955)
Lactation stage:
(1) Early (0 a 100 d).
(2) Middle (100 a 200 d) (3) Late (200 a 300 d).
The results for the density differed (P <0.05) in the milk collected in the period of 150 to 200 d of lactation, and the one obtained in the interval of 201 to 250 d at the moment of the sampling with respect to the remaining intervals. For fat, all the evaluated intervals differed among themselves (P <0.05), with the exception of the lipid contents recorded in those that had up to 100 and those that had 251 to 300 d of lactation, with the same performance in the intervals when evaluating t.
The results of fat performance and the differences shown can be related to the values reached at the beginning of lactation, when fat concentrations are higher, due to the formation of colostrum, according to Morales (2010). These concentrations decrease during the first two months of lactation, and tend to increase slowly and gradually, and as the end of lactation progresses and approaches.
Another factor that could influence on the changes in fat percentage, according to ranges of days of lactation pass by, can be related to a variation in the type of fatty acids in milk, when there is a predominance of short chain fatty acids or intermediate in the first half of lactation. These results correspond to those described by Morales (2010).
As described in figure 1 (Anon 2009), the fat increases progressively as the interval of lactation days passes, after 100 d post parturition (middle stage), to reach high concentrations after 220 d of lactation.
The same happens with the TS performance. The results achieved increase progressively, as the intervals of lactation days increase as lactation progresses, recording values from 12.04 to 12.08. This corresponds to that described by Blanco (2014), Jaimes et al. (2015) and Alaniz (2015), who maintain that while milk production is reduced with the advance of lactation, the concentrations of non-fat solids, fat and total solids in milk increase.
Conclusions
The reference values and normality thresholds for the composition and physical-chemical properties of the milk evaluated in the dairy “60” La Jibara “are in the ranges allowed by the Cuban standard, although they do not reach the standards described for Siboney de Cuba breed. This is associated with the quality and quantity of food the cow received and the lack in the availability of the food produced during the dry season in Cuba, which affects the metabolic health conditions at the rumen level and in the synthesis processes and secretion of the mammary gland. The methylene blue reduction time was below the standard established. However, 60% of the values of the sampled milk were classified as grade B. High percentage of samples with prevalence of subclinical mastitis was found, which considerably reduces the quality of milk produced and the clinical state of the udder of the females in production. The values of density, fat and NFS, when evaluating the milk produced as lactation proceeds, showed differences (P <0.05), associated to the lactation stage and to the values reached at the beginning and end of lactation.
