Relationships between milk yield, quality and coagulation properties with kappa-casein (к-CN) genotypes of Bulgarian Rhodope cattle breed

  1. Mehandzhiyski1, Т. Angelova2, D. Yordanova2, J. Krastanov2

 

1Research Centre of Livestock Breeding and Agriculture, 4700 Smolyan, Bulgaria

2Agricultural Institute, 6000 Stara Zagora, Bulgaria

 

(Manuscript received 12 June 2019; accepted for publication 10 August 2019)

 

Abstract. The aim of the present study was to establish the association between different к-CN genotypes with milk yield, quality and coagulation properties in dairy cows of Bulgarian Rhodope breed. For determination of milk proteins polymorphism and its relationship with individual coagulation properties of milk and its quality, 136 milk samples from Bulgarian Rhodope dairy cows reared in 4 farms were collected. The visit to the farms and the taking of the milk samples took place between May and June 2009. Animal milk is based on daily milking on the relevant control day of the current lactation. During the morning milking, 50mL samples were collected without preservative, stored in cooling bags and analyzed in the specialized lab at the Agricultural Institute, Stara Zagora by Computerized Renneting Metter. The evaluated parameters of milk coagulation properties were: rennet coagulation time (RCT, min); curd firming time (K20, min) and curd firmness (A30, mm). Milk proteins polymorphism was identified by tissue samples collection from 136 cows. To this end, specialized pliers and marks with a vial containing desiccant were used. With this technique, the tissue sample is obtained and sealed at the time of identification of the animal. After collection, tissue samples were shipped to the University in Padova, Italy for PCR-RFLP analysis. DNA was purified using a Maxwell®16 Tissue DNA purification kit (Promega) according to the manufacturer’s instructions. Data were analyzed using descriptive statistical analysis (SYSTAT 13). The results obtained give reason to the following conclusions: The highest milk yield was established in cows from the AH genotype – 16kg, whereas the lowest value was detected in cows from the BH genotype – 12.83kg. Homozygous cows from the BB genotype produced milk with the highest fat content – 5.11%, whereas heterozygous from the BH genotype: milk with the lowest protein content – 3.16%. The cows from the AH genotypes were outlined with the lowest milk fat and protein content. The longest rennet coagulation time (RCT) was observed in АА and АН genotypes, the longest curd firming time (К20) – in genotype AH, the highest curd firmness (А30) – in the milk of cows from the AB and BB genotypes.

Variability of individual coagulation ability and qualitative composition of milk from Kalofer Longhaired goats

G. Kalaydzhiev1*, A. Vuchkov2*, T. Angelova1, D. Yordanova1, V. Karabashev1, J. Krastanov1, D. Dimov2, N. Oblakov3, S. Laleva1, Y. Popova1

1Agricultural Institute, 6000 Stara Zagora, Bulgaria
2Departmet of Animal Science, Faculty of Agronomy, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria 3Freelance scientific advisor

Abstract. The growing scientific interest in the coagulation ability of milk in leading countries in Europe and in the world, is the premise for the research carried out by us in this direction. In this study 49 individual milk samples of goats from the autochthonous breed Kalofer Longhaired were examined for coagulation ability and qualitative composition of the milk. Analysis of individual coagulation ability was made in the dairy lab of Agricultural Institute, Stara Zagora through Computerized Renneting Metter – Polo Trade, Italy. The studied phenotypic parameters defining the dynamics of the qualitative composition of milk are with average values, respectively: fat – 4.15%, protein – 3.34%, dry non-fat substitutes (DNS) – 8.84%, lactose – 4.84% and pH – 6.62. The average values of exponents are rennet clotting time (RCT) – 11.47min, curd firming time (CR) – 0.86min, and curd firmness – 27.16 mm. Coagulation ability of the milk of Kalofer Longhaired goat have good technological properties for the production of traditionally identical milk products.

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