Compositional quality of cow’s milk and its seasonal variations in Bhutan

J Wangdi, T Zangmo¹, Karma², Mindu² and P Bhujel²

Planning and Policy Division, MoAF, Thimphu, Bhutan
jmewangdi@yahoo.com
¹ RLDC, DoL, Kanglung, Tashigang
² RNR-RDC, Jakar, Bumthang, Bhutan

Abstract

The study was undertaken to document baseline information on the compositional quality of cow’s milk and its seasonal variations in Bhutan. Majority of milk are produced by the rural farmers rearing different dairy breeds –Jersey, Brown Swiss, Mithun, Nublang, Holstein Friesian and their crossbreds. There was a significant differences (p<0.05) in the milk compositions among the different dairy breeds and their crossbreds. Likewise, a significant differences was also observed in milk composition between different seasons. Most milk components were found higher for improved cattle breeds reared in Bhutan than those reared in other countries. Milk produced in Bhutan is rich in fat, SNF and lactose.

The study recorded overall mean milk composition of 4.99 % fat, 8.59 % SNF, density of 1.028 kg/liter, freezing point of -0.571 ºC, 3.25 % protein, 5.48 % lactose and 0.67% other solids. The mean fat and protein percentages recorded were 4.74 & 3.08; 4.99 & 3.23; 5.67 & 3.65; 5.15 & 3.02; 5.53 & 3.67; 5.08 & 3.15 and 5.07 and 2.98, for BSx, Jx, Mx, LC, PJ, Nublang and HFx, respectively. The mean % lactose content was found exceptionally high in milk produced in Bhutan. However, the protein to fat ratio was observed comparatively low indicating sign of protein depression in cow’s milk produced in Bhutan.

Keywords: dairy breeds, lactose, Mithun, Nublang, protein to milk fat ratio, SNF

Introduction

Milk has been part of the human diet for millennia and is valued as a natural and traditional food. It is a nutrient dense food consumed across the globe by all age groups. Milk is generally composed of 87% water and 13% solids. The solid portions are composed of carbohydrate, fat, protein, minerals and vitamins, which has numerous functions. In many countries the fat, protein and lactose were routinely analysed as part of milk recording systems and those data were used for the breeding and genetic selection, and to some extent for the feeding evaluation (Hamann 1997). The solid content usually fat, protein and SNF determines the value of the milk for payment, and accordingly base prices for the raw milk were established between the buyer and seller in most countries. The milk components particularly protein and solid-not-fat (SNF) based milk pricing scheme are adopted for the payment to milk producers in most developed countries, placing a negative weighting on the carrier (volume) costs (Harding 1995). Yet, milk is still marketed on volume basis with less emphasis on the milk components in Bhutan. Nevertheless, at one point of time it will also become inevitable in Bhutan to introduce quality milk based payment to ensure minimum fair milk payment to milk producers.

Butter and cottage cheese dominates the markets, and less emphasis on products diversification has led to poor understanding on the important roles of milk components in Bhutan. With the growing consciousness on adverse implication of fats on human health, the dietary habits of the Bhutanese populace are changing and demand for more diversified low fat and protein based dairy products are increasing like any other countries. This changing consumption trend will compel dairy industry to produce diverse milk products to suit the consumers’ preferences and taste, which could be only attained through milk standardization. However, prior to gearing into milk standardization it has become imperative to have a basic empirical information on milk components and its seasonal variations of milk produced by different dairy breeds and their crossbreds. At this juncture such information is limited, nor are attempts made to explore and document about it. Therefore this study was conducted to understand and document baseline information on milk components and its seasonal variation of fresh raw milk produced by different dairy breeds and their crossbreds in Bhutan.

Materials and Methods

Study locations

The data were collected from migratory herders, members and non-members of dairy farmers’ groups of Tang and Chumey geog in Bumthang; Tangsiji in Trongsa; Trong in Zhemgang; Pam in Tashigang; Themnangbi in Monggar; Gelephu and Sarpangtar in Sarpang; Deothang in Samdrup Jongkhar. The data were also collected from the farmers of peri-urban dairy farms’ in Thimphu, community owned dairy farm in Tang, Bumthang and from the government owned cattle breeding farms i.e., Nublang farm in Tashiyangphu; National Brown Swiss Farm in Bumthang and National Jersey Breeding Farm in Samtse.

Animals and milk samples collection

Milk samples were randomly collected from different dairy breeds and their crossbreds i.e. Mithun cross (Mx), Jersey cross (Jx), Pure Jersey (PJ), local cattle (LC), Nublang (siri), Brown Swiss cross (BSx), Pure Brown Swiss (BS) and Holstein Friesian cross (HFx). Milk samples were collected from 40 dairy cows of different dairy breeds and their crossbreds once every month, for a period of one year from each study location (January 2013 to December 2013). All samples for the PJ and Nublang was collected from the government owned farm. The local cattle comprises of Thrabum, Doethrabum, Doebum and Datum Mithun cross comprises of Jatsham and Yangkum reared by farmers.

Milk in the container was thoroughly mixed after the complete milking, and milk samples of about 20 ml were collected from each cow in a plastic vial. Then the samples were stored in a cool box until the analysis. The samples were analyzed within 2 hours from the collection of samples using automatic ultrasonic milk analyzer (Master Eco, India). The following milk components – fat, SNF, protein, lactose, density, freezing point and added water are automatically analyzed by the instrument. Simultaneously, the readings displayed on the instrument were recorded in the data record sheet. In total, 4847 milk samples were collected and milk composition was analyzed by the extension staff, technically backstopped by the staff of the Renewable Natural Resources – Research and Development Centre (RNR-RDC), the Regional Livestock Development Centre (RLDC) and the National Dairy Development Centre (NDDC).

The data gathered were entered and organized in an Excel spread sheet, which then were exported and analyzed using GLM-multivariate software in SPSS Version 21 (Landau and Everett 2004). Post hoc test (Tukey) was conducted to compare the mean milk composition of milk produced by the different dairy breeds and its seasonal variation.

Results and Discussion

Mean milk composition and its seasonal variations

 Differences in the mean milk composition were observed both seasonally and between the dairy breeds and their crossbreds. A higher variation in fat content was observed in comparison to other milk components (Tables 1 and 2).

Fat and protein content

A significant mean difference (p<.05) was observed in % fat and protein content in milk of different cattle breeds and their crossbreds in this study. There was a significant differences (p<.05) in mean % fat content but there was no significant differences in the mean % protein content by seasons. The overall mean percent fat and protein content recorded was 4.99 % and 3.25 %, respectively. The highest % fat content was observed in Mx (5.67) and PJ (5.53) followed by LC (5.15), Nublang (5.08), HFx (5.07), Jx (4.99) and the lowest was recorded in BSx (4.74) cattle. The highest mean % protein was observed in milk of PJ (3.67) and Mx (3.65), and the lowest was recorded in HFx (2.98%) in this study. The study recorded highest mean % milk fat (5.11) during the spring months followed by the winter (5), summer (4.88) and autumn (4.80). The differences in mean fat and protein percentage between different dairy breeds and their crossbred may be attributed to different contributing factors, i.e. stage of lactation, disease, calving season, age, genetics, productivity, seasons, different management practices particularly in terms of feeding and environment. The differences may be attributed to different calving seasons – where majority of calves were found to be calved during the winter months in this study, and by the autumn months the animals have attained last stage of lactation. Fat content was reported to be high, immediately after the calving but soon begins to fall, and continues to do so for 10 to 12 weeks, after which it tends to rise again until the end of the lactation (O'Mahony 1998). The highest concentration of milk fat and protein was recorded during the early and late lactation stage and lowest during the peak milk production through mid-lactation (Looper 2014). It was also reported that the highest milk fat and protein percentages was recorded during the fall and winter, and lowest during the spring and summer season resulting mainly due to changes in both the types of feed availability and climatic conditions (Looper 2014).

SNF and lactose content

Milk is standardized based on the SNF and fat content, and accordingly base milk prices were fixed in many countries. Most developed countries have adopted protein and SNF based milk pricing scheme for the payment to producers, owing to increasing demand for protein based food and ever growing consciousness on adverse implication of fats on human health. The scheme was adopted to ensure minimum fair milk payment to milk producers. Differences in % SNF were observed among different dairy breeds and the crosses; however, there was no seasonal variation. The overall mean SNF content recorded was 8.59 % with the highest and lowest % SNF of 9.79 % and 8.27% in Mx and HFx, respectively.

The lactose content of milk was found similar across the dairy breeds and their crossbreds; but it was observed higher as compared to reports of other authors. A seasonal variation was also not observed in the lactose content. The overall mean lactose content recorded in this study was 5.48, exceptionally higher than reported by O'Mahony (1998) which was between 4.7 and 4.9%.  The milk produced in Bhutan is rich in lactose. 

Density and % added water

The specific gravity of whole cows' milk (ratio of density of milk to density of water) varies among different breeds and among cows within breed. The overall mean density of 1.028 kg/liter (range 1.023 to 1.032) was observed for the milk produced in Bhutan. The density of milk is reported to change with changes in temperature, primarily because water and fat expand as they are heated (Hurley 2010). In Bhutan, an overall mean value for added water of 0.89 % was recorded.  The management practices, particularly the remains of the rinse water in the milk container prior to milking and addition of the rinse water to the tank after the milking might have contributed to the presence of added water in milk. An awareness must be created among the milk producers on the importance of keeping milk free of added water and its repercussion to the milk producers and processors.

Freezing point of milk

The freezing point of milk is an important indicator of the milk quality. It is determined primarily to prove milk adulteration with water and to determine the amount of water added (Zagorska and Cipovica 2013). Similarly, Henno et al (2008) reported that the freezing point of milk is used as one of the quality criteria for insuring high quality milk. In this study, the overall mean base freezing point was - 0.540 ºC. The findings were found close to the average milk freezing point reported by OAANC (2005) of -0.540 ºC. OAANC (2005) reported that the freezing point of milk was affected by the freezing of milk during cooling, or addition of rinse water to the tank in most cases.

Milk protein to fat ratio

In this study, the overall mean protein to milk fat ratio estimated was 0.65 (Table 3). The findings is comparatively low in comparison to the report of Harding (1995) indicating a sign of milk protein depression of cow’s milk in Bhutan. In general, if the milk protein-to-milk fat ratio is less than 0.80, there is a problem of milk protein depression (low milk protein test) and when this ratio is greater than 1, the herd suffers from milk fat depression (low milk fat test) (Schroeder 2012). This might have resulted due to feeding of animals with low protein content feed. Thus, there is scope in enhancing milk protein content in Bhutan through feeding animals with a high protein diet.

Conclusions

• The study has established baseline information on the compositional quality of fresh raw milk and its seasonal variations among different dairy breeds in Bhutan.
  
  
• The mean lactose content was found exceptionally high. However, the protein to fat ratio was comparatively low
  
  
• There was greater seasonal variability in milk fat than for other milk components
  

Acknowledgement

The authors would like to extend sincere thanks to all the respondents, Extension Agents and the Dzongkhag Livestock Officers of the study sites; Program Directors of the Regional Livestock Development Centres, Kanglung and Zhemgang, and the National Dairy Development Centre, Yusipang; and Farm Managers of National Jersey Breeding Centre, Samtse, National Brown Swiss Farm, Boepalathang and Nublang Farm, Tashiyangphu for their unwavering support.

The authors would also like to thank all staffs and the management of RNR-RDC, Jakar for their kind supports, and the Royal Government of Bhutan for the financial supports.

References

Hamann V K 1997. Livestock Production Science (48), pp. 201-208

Harding F 1995. Milk quality. Chapman and Hall, 2-6 Boundary Row, London, UK

Henno M, Ots M, Jõudu I, Kaart T and Kärt O 2008. Factors affecting the freezing point stability of milk from individual cows, International Dairy Journal, Volume 18(2), pp. 210–215.

Hurley W L 2010. Lactation biology. Animal Sciences, Department of Animal Sciences, University of Illinois, Urbana, IL http://ansci.illinois.edu/static/ansc438/Milkcompsynth/milkcomp_density.html retrieved June 12 , 2014

Landau S and Everett B S 2004. A Hand book of Statistical Analyses Using SPSS. Boca Raton, FL Chapman & Hall/CRC.

Looper M 2014. Factors Affecting Milk Composition of Lactating Cows. Agriculture and Natural Resources, Department of Agriculture Research and Extension, University of Arkansas System. http://www.uaex.edu/publications/pdf/fsa-4014.pdf retrieved on 1/9/2014

O'Mahony F 1998. Experiences in Ethiopia. ILCA Manual No. 4, International Livestock Centre for Africa, Addis Ababa, Ethiopia. http://www.ilri.org/InfoServ/Webpub/fulldocs/ilca_manual4/Factors.htm#P36_1410 retrieved 16/6/14

OAANC 2005. Significance of Nutritional Effects on the Freezing Point of Milk.Ontario Agri-Business Association Nutrition Committee http://www.milk.org/corporate/pdf/Farmers-FreezingPoint.pdf retrieved 12 June, 2014

Schroeder J W 2012. Dairy Cow Nutrition Affects Milk Composition http://www.ag.ndsu.edu/pubs/ansci/dairy/as1118.pdf retrieved June 12, 2014

Zagorska J and Ciprovica I 2013. Evaluation of Factors Affecting Freezing Point of Milk World Academy of Science, Engineering and Technology Volume 7, pp. 02-22 http://waset.org/publications/15910/evaluation-of-factors-affecting-freezing-point-of-milk retrieved 12 June, 2014

Received 20 October 2015; Accepted 24 December 2015; Published 2 January 2016

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