Severe feed restriction increases permeability of mammary gland cell tight junctions and reduces ethanol stability of milk

Abstract

A total of twelve lactating Jersey cows were used in a 5-week experiment to determine the effects of severe feed restriction on the permeability of mammary gland cell tight junctions (TJs) and its effects on milk stability to the alcohol test. During the first 2 weeks, cows were managed and fed together and received the same diet according to their nutritional requirements (full diet: 15 kg of sugar cane silage; 5.8 kg of alfalfa hay; 0.16 kg of mineral salt and 6.2 kg of concentrate). In the 3rd week, animals were distributed into two groups of six cows each. One group received the full diet and the other a restricted diet (50% of the full diet). In the 4th and 5th weeks, all animals received the full diet again. Milk composition and other attributes, such as titratable acidity, ethanol stability, pH, density and somatic cell count (SCC) were evaluated. Cortisol levels indicated the stress condition of the cows. Plasma lactose and milk sodium were measured to assess mammary TJ leakiness. Principal factor analysis (PFA) showed that the first two principal factors (PFs) contributed with 44.47% and 20.57% of the total variance in the experiment and, as feeding levels increased, milk stability to the ethanol test became higher and plasma lactose levels decreased, which indicates lower permeability of the mammary gland cell TJ. Correspondence analyses were consistent with PFA and also showed that lower feeding levels were related to reduced milk stability, high plasma lactose, high sodium in milk, low milk lactose (another parameter used to assess TJ permeability) and higher cortisol levels, indicating the stress to which animals were submitted. All observations were grouped in three clusters, with some of the above-mentioned patterns. Feeding restriction was associated with higher permeability of TJ, decreasing milk stability to the ethanol test.

Seasonal variation, method of determination of bovine milk stability, and its relation with physical, chemical, and sanitary characteristics of raw milk

“…Low and high ethanol stability values observed in different months, depending on the year, might be partially explained by variation in feed supply or feed quality with consequent changes in mineral composition (Tsioulpas et al, 2007;Lewis 2011;Stumpf et al, 2013;Horne, 2015). The overall low stability value observed in 2008 was probably related to the occurrence of the La Niña phenomenon, which led to shortages in rainfall, mostly on spring and summer, reducing the production and quality of feeds offered to the animals.…”

Behaviors associated with cows more prone to produce milk with reduced stability to ethanol test due to feeding restriction

“…This same affirmation can be made when correlating feeding level and milk sodium in PF analysis. Values for sodium in milk were highly variable within and between animals and mammary gland cell's tight junctions' opening might be involved in such results (STUMPF et al, 2013), which increases the inflow and/or outflow of this ion to the mammary gland. As expected, higher feeding level was followed by elevations in the stability of milk to the ethanol test in analysis.…”

“…As expected, higher feeding level was followed by elevations in the stability of milk to the ethanol test in analysis. This may be due to reduced permeability of mammary gland tight junctions in cows full fed (STUMPF et al, 2013), which can be attested by the negative correlation between feeding level and plasma lactose in PF, a reliable indicator of tight junctions opening (STELWAGEN et al, 2000).…”

“…The relation between behavior parameters and milk stability remains elusive, but mechanisms such as the increase in the permeability of mammary gland cell's tight junctions in stressed animals (STELWAGEN et al, 2000;STUMPF et al, 2013), which could be detected visually, might be a explanation for the findings and a scientific field yet to be explored.…”

“…Stability can be altered due to lactation stage (TSIOULPAS et al, 2007a), ionic calcium content in milk (TSIOULPAS et al, 2007b), alterations in the permeability of mammary gland cells tight junctions (STUMPF et al, 2013), among others. Milk stability to the ethanol test is of great importance for milk producers and dairy industries, especially in developing countries such as Brazil, Uruguay, Argentina, Taiwan and Russia since it defines milk suitability for industrial processing -milk with reduced stability is considered unsuitable and is not collected by dairies.…”