Heavy Mares Research Articles

ВЛИЯНИЕ ГРУПП КРОВИ, АЛЛЕЛЕЙ И АНТИГЕНОВ ЭРИТРОЦИТОВ НА СОДЕРЖАНИЕ ОБЩЕГО БЕЛКА В МОЛОКЕ КОБЫЛ ТЯЖЕЛОВОЗНОЙ ПОРОДЫ

In recent years, more and more attention has been paid to the study of polymorphic genetic systems of blood proteins and their application as indicators of the most objective assessment of breeding qualities of farm animals. Specification of blood groups of Russian and Lithuanian heavy breed mares was carried out according to the methodological recommendations developed by R. Μ. Dubrovskaya and I. Μ. Starodumov. The erythrocyte antigens of Α and D blood groups of horses were typed with the help of monospecific sera. By the method of family analysis, the alleles and genotypes of mares were determined according to the D blood group system. Using the Hardy-Heinberg formula, the frequencies of genes were determined by simple counting. An AM-2 analyzer was used to analyze mare milk for total protein content. The studied breeds of mares are characterized by a high occurrence frequency of Dad, Dde, Ddghm alleles. Great significance of antigenic similarity in D blood group system between the Lithuanian and Russian heavy breeds indicates genetic similarity of these breeds. The relationship between total protein content and immunogenetic parameters was determined. High protein content of Lithuanian heavy breed mares is associated with the presence of DdkDcgm genotypes; as for Russian heavy mares - genotypes DbcmDdghm. Taking into account the revealed positive relationships of immunogenetic indicators with the milk protein content of mares of heavy breeds, it is possible to recommend application of the results obtained to adjust the selection for breeding work.

Expression of oxytocin receptors is greatly reduced in the placenta of heavy mares with retained fetal membranes due to secondary uterine atony.

Fetal membrane retention can be a life-threatening condition and its incidence exceeds 50% in heavy draught mares. Although fetal membrane retention is commonly treated with repeated injections of oxytocin, based on the suggestion that it is caused mainly by secondary atony of the uterus, this treatment sometimes fails. This led us to ask if expression of oxytocin receptors differs in mares that retain fetal membranes due to secondary uterine atony. To determine whether expression of oxytocin receptors in equine placental tissues differs when heavy draught mares expel fetal membranes or retain them because of secondary uterine atony. Controlled study using archived tissues. Placental biopsies (containing the endometrium and allantochorion) were taken from 8 heavy draught mares during parturition. Four mares expelled fetal membranes shortly after foaling (control mares) and 4 mares retained them (expulsion time was >3 h from delivery). The 4 mares that retained fetal membranes had secondary atony of the uterus. The amount of oxytocin receptors was estimated by measuring the intensity of western blot bands. The presence and location of oxytocin receptors were determined by immunocytochemistry. Oxytocin receptor expression was nearly 50 times less intense in mares with placenta retention due to secondary atony of the uterus and immunocytochemical staining was barely visible. In the control mares, oxytocin receptors were found in both epithelial and endothelial cells of the placenta and staining was most intense where the endometrium contacts the allantochorion. Inadequate expression of oxytocin receptors may be a cause of uterine atony leading to fetal membrane retention.

Fertility after fetotomy: a clinical study focusing on heavy draft mares

Although fetotomy is recommended for all mares when the fetus is dead and difficult to extract, little has been written about fetotomy and heavy draft mares. This lack includes indications...

Effect of parity and physiological state on intake, milk production and blood parameters in lactating mares differing in body size

ABSTRACTVoluntary food intake, milk production and blood characteristics were measured in mares between the 3rd month before foaling and the first 5 weeks of lactation. The effect of breed during pregnancy was determined using 15 light mares and eight heavy mares (522 and 763 kg live weight (LW) after foaling respectively). The effect of parity was studied on light mares (seven were primiparous and eight were multiparous). In lactation, only four primiparous and four multiparous light mares were retained. Diet consisted of 900 g hay and 100 g concentrates per kg and was offered ad libitum. Voluntary food intake in pregnancy was higher for heavy mares than for light mares: 15·2v.10·3 kg dry matter (DM) daily. This difference was explained by differences in LW, since DM intake was the same when expressed as a fraction of LW or metabolic weight (M). Energy and nitrogen supply exceeded requirements, in the same way for light and heavy mares. No significant variations in blood measurements were observed between light and heavy mares, except for glucose. Primiparous mares ate less DM than multiparous mares in pregnancy: 9·7v.10·8 kg DM (P > 0·05), significantly so relative to LW and M. DM intake per kg LW or M depended on the parity. This difference had no effect on blood measurements, except for acetate. During lactation, no other differences in voluntary food intake were observed with regard to parity, whatever the week of lactation. Milk yield was higher for multiparous mares than for primiparous mares (16·6v.14·6 kg daily). Gross energy of milk varied according to a similar pattern, principally because of variations in fat concentration (20·2v.16·5 g/kg for multiparous and primiparous mares respectively). Energy balance was significantly more positive for multiparous than for primiparous mares.