Monthly and seasonal evaluation of dietary nutrients and their relationships with blood and milk parameters in lactating dairy cows

Abstract

Monthly and seasonal variations among dietary, blood and milk parameters and their interrelationships were investigated during the lactation period in Holstein dairy cows in order to determine reliable dietary indices that could be useful in the studies related to milk yield improvement. Samples were prepared monthly, up to 11 months of lactation and were analyzed by the current laboratory methods using appropriate kits. Mean monthly and seasonal comparison of the dietary, blood and milk values were different among sampling times (p<0.05). The overall mean for dietary energy (ME), crude fiber (CF), moisture, ash, phosphorus (DP), calcium (DCa), ether extract (EE) and crude protein (CP) were 1.38 Mcal/KgDM, 20.4%, 42.8%, 5.5%, 0.34%, 0.76%, 2.39% and 10.2%, respectively. Correlations were found between dietary DP/Ca (r=-0.73), DP/EE (r=0.67), DP/ash (r=0.79), DP/moisture (r=0.84), DP/ME (r=0.60), Ca/ash (r=0.95), Ca/moisture (r=-0.64), and DCa/moisture (r=-0.93). Correlations among dietary, blood, and milk parameters revealed different relationships with the most important correlations between DP and blood parameters, and CP with blood and milk parameters. Among blood parameters glucose, BHB, SK, AST, GGT, neutrophils and lymphocytes. Milk parameters: Mg, Ca, and lactose showed the strongest relationships with dietary parameters. In conclusion, the dietary, blood and milk values were different during the lactation months and seasons. Dietary CP, Ca and DP could be applied as relevant indices in studies related to milk production improvement in dairy herds

Relationships among Macro-Minerals, Other Selected Serum Markers of Bone Profile and Milk Components of Dairy Cows During Late Lactation

“…The significant and positive correlations between serum TP and MP (r=0.452), as well as between serum albumin and MP (r=0.449) obtained in our studies show a clear metabolic and structural relationship between blood and milk proteins. The significant and positive correlation between total serum protein and milk protein was also noted by other authors on the level r=0,23, (p<0.01), but they did not compare albumin, specifically (Nozad et al, 2012). Other authors reported that they compared serum albumin with milk protein with insignificant result (r=0.107), but they tested cows in different lactation periods with different statuses (Djokovic et al, 2019).…”

“…These relationships may also apply to milk, where our results showed significant positive correlations between serum Mg and MP, and, as a consequence, significant positive correlations between serum Mg and FDM. Interestingly, in other studies performed during different lactation periods in cows, other authors recorded a significant positive correlation between blood magnesium and blood protein at r=0.36 (p <0.01), but did not record a significant correlation between serum magnesium and protein in milk (Nozad et al, 2012). However, in other studies of cows, also during various lactation periods, there were no significant correlations between magnesium and serum protein or between magnesium and serum albumin, and also none between serum magnesium and protein in milk (Djokovic et al 2019).…”

“…However, during particular life phases such as peripartum, and particularly lactation, female mammals have to adapt to physiological demands and adaptation, thus the comparison with established reference intervals becomes complicated (Arfuso et al, 2016, Fiore et al 2017. Relationships between contents of biochemical metabolites in blood and milk in highly productive dairy cows are important not only during transition or early lactation period but also during other stages of milk such as mid-lactation and late-lactation when the daily values of milk are also high (Nozad et al, 2012, Djokovic et al, 2019, Mordak et al, 2020.…”