Assessment of Elemental Deficiency of Crossbred Dairy Cows and Mineral Composition in Natural Feed and Nutritional Supplements in the Northern and Northwestern Provinces in Sri Lanka.

Abstract

This study assessed the elemental status of cross-bred dairy cows in small holder farms in Sri Lanka, with the aim to establish the elemental baseline and identify possible deficiencies. For this purpose, 458 milk, hair, serum and whole blood samples were collected from 120 cows in four regions of Northern and Northwestern Sri Lanka, (namely Vavaniya, Mannar, Jaffna and Kurunegala). Farmers also provided a total of 257 samples of feed, which included local fodder as well as 79 supplement materials. The concentrations of As, Ca, Cd, Co, Cr, Cu, Fe, I, K, Mg, Mn, Mo, Na, Ni, Pb, Se, V and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS). Evaluation of the data revealed that all cows in this study could be considered deficient in I and Co (18.6-78.5 µg L^-1 I and 0.06-0.65 µg L^-1 Co, in blood serum) when compared with deficiency upper boundary levels of 0.70 µg L^-1 Co and 50 µg L^-1 I. Poor correlations were found between the composition of milk or blood with hair, which suggests that hair is not a good indicator of mineral status. Most local fodders meet dietary requirements, with Sarana grass offering the greatest nutritional profile. Principal component analysis (PCA) was used to assess differences in the elemental composition of the diverse types of feed, as well as regional variability, revealing clear differences between forage, concentrates and nutritional supplements, with the latter showing higher concentrations of non-essential or even toxic elements, such as Cd and Pb.