Сельскохозяйственная биология, 2010, № 2, с. 18-24.

УДК 636.2.034:591.23:576.385.34

CORRELATION BETWEEN MAMMARY GLAND ACTIVITY AND FATTY DEGENERATION OF LIVER IN HIGH PRODUCTIVE COWS

E.V. Dushkin

The correlation between a dairy production and an intensity of lipid metabolism in cow’s liver at the early lactation phase, result in the lipid accumulation in a liver and mobilization of lipid reserves was discussed. An amount of fatty reserves and an ability of its usage in the condition of lactation are considered as critical factor for optimization of milk productivity, feed consumption and animal’s health. For the correction of animal state the author proposes to use the hepatoprotective preparation of Antitox.

Key words: hepatic, fatty acids, newly calved cows, feeding, milk productivity.

Mammary gland is a body with high metabolic action; it weights 70 kg and over at a peak of lactation in high yielding cows, and the amount of dry matter produced by it over lactation may be equal to a live weight of animal (1).
The animal’s energy requirements can’t be always and completely satisfied by feed nutrients supply. In early lactation, high milk productivity is provided in cows with both the feed energy and daily mobilization of 2 kg of body fatty reserves, due to metabolic processes focused on utilization of fatty acids in the mammal gland in this period (2). An intensive selection of dairy cattle for a high dairy productivity has led to the genetic productivity potential in early lactation, exceeding animal’s ability to consume enough food, which induces a negative energy balance.
In late pregnancy in cows, expenses of energy and plastic substances are determined by the rate of foetal growth; in newly calved cows - with the rate of biosynthesis and secretion of milk components, as well as with inadequate exogenous supply of nutrients and energy. The intensive usage of fatty and protein reserves to cover the deficit occurs against the background of "over-milking" of cows and significant changes in lipid metabolism. These factors affect the prospective productivity and health of high yielding cows (3).
Being a part of a reproductive cycle, lactation is closely linked to the direction of metabolism. Soon after calving, the so-called state of dominant lactation develops: the process of milk formation in the udder dominates in general metabolism. At the same time, in high yielding cows, about a half an energy costs for formation components of milk in early lactation is replaced with tissue reserves (over 300 g of protein and up to 1000 g of fat are consumed per day) (4). The intensive mobilization of reserve lipids may suppress feed consumption and inhibit the own synthesis of fat in the mammary gland, determining ketoses. The usage of reserve lipids’ energy is less efficient than the feed energy, which makes the amount of fatty reserves and an ability of its usage the critical factors for optimization of milk productivity, feed consumption and animal’s health.
Liver is a center of metabolism of fatty acids - triacylglycerols, mobilized from fatty reserves. The mammary gland as a body providing lactation, affects the rate of body lipids mobilization and synthesis in the liver of triacylglycerols (mainly low-density lipoproteins) necessary for synthesis and secretion of milk fat (5). Triacylglycerols are allocated into the blood in the form of lipoproteids, but at the insufficient protein income from the gastrointestinal tract in early lactation and / or at the forced triacylglycerols mobilization from adipose tissue, have to be deposited in liver cells causing their fatty infiltration and disfunction (6).
 In early lactation, the liver is not able to accelerate secretion of lipoproteins adequately to the intensive mobilization of lipids (7) and the insufficient feeding of animals (8). The lipid infiltration of the liver, typical for all cows, is observed before calving and in early lactation (8-11). It develops mainly due to the increase in concentrations of triacylglycerols (9), if their synthesis and secretion don’t raise in proportion to consumption from adipose tissue to be utilized in the mammary gland (8).
However, accumulation of lipids in the liver before calving doesn’t harm animal’s health, but the genetically caused fatty liver clinically manifested with the beginning of lactation may result in protein and toxic liver dystrophy. This state is also connected to changes in microflora composition in the rumen that develops at an insufficient or excessive fermentation of cellulose, proteolysis and self-poisoning by products of destruction, which is accompanied by loss in body weight and milk yields, painful joints, dysfunctions of nervous and cardiovascular systems, digestive disorders (10).
The state of lactation dominance affects the decrease of  lipogenesis in adipose tissue, and increase - in the mammal gland. The rate of fatty acid synthesis in biopsy samples of ruminants adipose tissue is higher (in 20 times and over) than in liver samples (12). This leads to the liver overload with interesterification of unesterified fatty acids (UFA) triacylglycerols,  mobilized from tissue reserves at lipolysis. In other words, at the lactation, the functional activity of mammary gland greatly exceeds the liver. Dairy production is determined by the optimal composition, balance and sources of substrates necessary for  increased biosynthesis and secretion in the mammary gland, and it also depends on a physiological abilities of organs and tissues providing lactation (digestive organs, mammary gland and adipose tissue) to cooperate to each other.
To provide the significant raise in milk productivity of dairy herd, that was proposed to import heifers from abroad, but in some farms it resulted in a high culling of imported livestock after the first calving. At present time in Russia, the number of cattle, as well as indicators of its reproduction and conservation are reducing (13).
In metabolism, nutrients distribution is controlled by mechanisms of homeostasis and gomeorezis (14). Gomeorezis is the regulation providing nutrients direction to an organ or system of organs at their maximum activity. We assume that the high productive dairy cows are distinct from less productive animals in degree of gomeoretic control by the endocrine system. Animals with unequal productivity, apparently, also differ in their ability to mobilize tissues (primarily fatty reserves) at the deficit of energy supply from feed and in their ability to change the rate of feed nutrients secretion (energy and key plastic metabolites) into the blood.
We compared the milk productivity and health of the liver (for lipid content) during the active lactation (100 days of lactation) in three groups of new-calved cows the Yaroslavskaya breed (8 cows in each group) given the diets with increased and low (15 %) content of energy and protein (respectively, II and III group) compared with the recommended (I group, a control).  That was shown (9), that the increase in energy and protein value of a diet resulted in the raise of milk productivity by an average of 12% (9). In cows fed the recommended or the enriched diet, milk yields were gradually increasing; the diet with the deficit of energy and protein affected no much increase by the end of the 3rd month of lactation (Table 1). So, energy and protein provide in early lactation significantly influences the shape of lactation chart. The amount of milk fat, produced by dairy cows in group II and in control, was steadily increasing (probably due to increase in milk yields), in group III - did not increase (due to a small increase in milk yields) (see Table 1.) and, as a result, was maximum in group II (see Table. 1).

The enriched diet (group II) also resulted in reduce of body weight loss in new-calved cows by 16.62 kg compared to control (group I), while the restricted diet (group III) enchased a cachexia by 23.13 kg (9 ). The highest content of total lipids in liver cells was observed in group III. In the 1st month of lactation, this value was 6650 mg%, which exceeded the control at 1580 mg% and in group II at 2070 mg%. The borders of liver blunting were determined: in group III - from the 13th to 9 th ribs, in control - from the 12 th to 9 th ribs, in group II - from the 12 th to 10 th. At the 2 nd month of lactation, the content of total lipids in the liver rapidly decreased in all individuals - 34.91, 32.31 and 48.87% in groups I - III, resp.. In the control group, the percussion area of lower border of the liver was restricted, in other animals – remained unchanged. In group II, stabilization of the liver size was observed in the 1 st month of lactation.
Lipid infiltration of the liver in new-calved cows caused by the energy and protein-restricted diet (9) is,  obviously, reversible to some extent. However, the restoration of liver function in late lactation may be influenced by genetic potential of productivity, lactation phase, diet composition, etc. Only in 30% high-productive cows, the fatty infiltration of the liver affects the structure and function of the liver significantly, but reversibly. Such subclinical fatty liver is connected with accumulation of fat in other tissues and organs - kidneys, adrenal glands and muscles, which causes hyperadiposity in new-calved cows and the decrease in fatness after calving (8).
After calving, the fatty infiltration of the liver cells was observed almost in all animals (mainly due to total lipids and triacylglycerols) (9), but the least expressed - in group II (Table 2), which suggests that the enriched diet inhibits mobilization of lipids from tissues and prevents fatty liver.

In biopsy samples of liver, we measured the content of total lipids and triacylglycerols (see Table. 2) - the main factions involved in synthesis of milk fat (9). It is known, that the mammary gland uses triacylglycerols brought via blood in the form of chylomicrons or lipoproteid triacylglycerols and UFA, associated with albumin (15).
In our experiments, the enriched diet provided the decrease of accumulation rate of triacylglycerols in the liver; the restricted diet caused an increase, which resulted in suppress of using the exogenous sources at formation of milk. By the 2nd month, the active mobilization of body reserves was leading to inhibition of lactation dominance .
Cytological deviations in fatty liver, such as mitochondria alterations and the expansion of endoplasmic reticulum, suggest the metabolic disturbances in hepatocytes at the acute steatosis (8).
So far, there were few experiments emphasizing the influence of organism state before calving on the occurrence of fatty liver in early lactation: the highly-fed animals are more prone to this disease due to more intensive mobilization of tissue lipids and the low activity of consumption functions, which is clinically manifested as a progressive weight loss after calving and may result in a forced culling of the animal (16).
We believe that the forced culling of animals in most of the imported livestock (mainly in the 1st month after calving), is owing to the liver pathology and degenerative changes in rumen tissues (at liver percussion, the enlargement of the low margin was established, at auscultation - hypo- and atonia of the rumen). In the blood, the raise in the content of ketone bodies and decrease - of glucose and hemoglobin were determined, as well as the rapid weight loss in all the animals (16).
The clinical diagnosis of fatty (and toxic) dystrophy of the liver was repeatedly confirmed at the forced slaughter inspection. At autopsy, the liver was yellow or grayish-yellow (clay) color, medium-dense or loose in touch, with easily squeezed fragments or releasing parts of destructed tissue observed at palpation in most cases.
The significant proportion of lipids (about 34%) brought via blood (80% the portal vein and 20% the arterial blood) are retained in the liver, and not all of them are refunded with bile in the duodenum (17 ).

To solve the problem of environmentally sound preventive and curative prepatations based on natural ingredients (18), we have developed the preparation Antitox, which performs antiseptic and anti-inflammatory action, improves and restores the lipid-carbohydrate metabolism, stimulates tissue regeneration, operates as a good antidote and antioxidant, is not an antagonist for the preparations of integrated treatment and prevention of diseases including vaccination (19).
The evaluation of preparation effects was carried out on the imported livestock - the new-calved cows (the farm “Privolye” Ltd., Slavyanskij district, Krasnodar region). The hepatic boundaries were measured: prior to treatment, the horizontal percussion (Table 3) averaged 20.6 cm, after a single use of 20 ml Antitox (10 ml subcutaneous and 10 ml intramuscular injection) daily for 6 days - 12.3 sm.  
Simultaneously, the milk yields were evaluated (see Table. 3). In all the cows, milk yields were increasing with the restriction of topographic area of lower hepatic margin, in the experiment - more expressed than in control. The distinct in milk productivity between the groups, apparently, was caused with the fact that the experimental group had the better usage of feed nutrients and less "over-milking”. The control group of cows suffered from the energy deficit - the result of slow adaptation to replacement of own reserves with feed nutrients. For the same reason, in the control group one cow was culled for signs of progressive weight loss (see Table. 3).
So, to maximize the dairy and milk fat production without compromising the health of highly-productive cows, it is necessary to cover the deficit in protein and energy in new-calved cows (by the additional feeding of carbohydrate-rich cereals and fodder root crops). We recommend the hepatoprotective preparation Antitox for preventive use. Milk productivity should be monitored as an indicator of general state of an organism and functional state of the liver, especially in the critical period in new-calved cows.

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