The role of mineral supplementation on the incidence of bovine reproductive conditions in communal areas around Mafikeng of the North West Province

Abstract

The aim of this study was to determine the metabolic characteristics of bovine presenting with reproductive conditions in order to establish important predictors for their incidence in communal farms in the Mafikeng District Municipality in South Africa. To achieve that, the current study evaluated concentrations of serum minerals, biochemical parameters and reproductive hormones along with the management of the cows that presented with abortion, dystocia, vaginal prolapse, retained placenta and downer cow syndrome. This research was conducted in Mafikeng by following up cases of reproductive conditions brought to the North West University (NWU) Dale Beighle Animal Health Centre. A convenient sampling method was used in the collection of blood samples from cows presenting with reproductive conditions during ambulatory trips to different communal farms. A total of one hundred and eighty two (182) cases were attended to and blood samples from cows presenting with retained placenta (n=13), abortion (n=69), downer cow syndrome (n=34), dystocia (n=50) and vaginal prolapse (n=16) were collected. Additional to that, a structured questionnaire was administered to assess the management issues in the different affected herds, for which 135 farmers were interviewed on each reproductive condition or case attended. Furthermore, for confirmation of data, a controlled study on the effect of mineral supplementation during pregnancy was run on an identified farm which previously had presented several reproductive conditions among its animals. In this study, 12 pregnant cows were chosen and divided into two groups: a control and an experimental group with six cows in each. A randomly selected sample of primiparous and multiparous cows aged between 3-5 years, with body weight between 347 and 540 kg and parity of 1 to 2 were assigned to the control (non-supplemented) or experimental group (supplemented). The cows in the experimental group were supplemented, at 6-week intervals, from mid- to late gestation with MULTIMIN™+ Se +Cu at 1ml/45 kg BW and Calci 50 p.i. at 100-150 ml/500kg BW dosage. Blood samples were collected before the experiment and after every six weeks when supplements were given. Sample analysis for minerals, serum metabolites and hormones were performed using the Inductively Coupled Plasma Mass Spectrometer (ICP-MS), IDEXX Catalyst and ELISA kits, respectively. The data were statistically analysed using SPSS version 25 to calculate frequencies and descriptive statistics. Pie charts were used to summarise the responses for each variable in the questionnaire. The Chi-square test of association was used to determine the possible association between the occurrence of the reproductive conditions and the various attributes of the cows as well as the farm management practices. A two-stage cluster analysis was used to segment the animals based on the variables associated with the reproductive conditions as identified by the Chi-square test. The effect of the reproductive conditions on the serum biochemistry, hormonal and mineral profiles of affected animals was estimated by means of the Multivariate Analysis of Variance (MANOVA). A post hoc test (Tamhane T2) was used for the significant ANOVA tests, to determine the statistical significance and the magnitude of the differences in the means of each serum metabolite and mineral between pairs of reproductive conditions. The data generated from interviewing farmers showed that most communal farms were headed by males (79%), aged between 40-55 years; most had primary level of education (76%), were single (68%) and the majority had monthly income of <R1000.00. The cows which were affected by the reproductive conditions were mostly in their first parity (49%), they were from free-range farms (58%), from herds with only one annual veterinary checkup (71%) and had unknown Brucella status (100%). In this study, analysis of blood in cows with reproductive disorders revealed a significant (P<0.05) relationship between dystocia cases and high selenium (11.423 mg/L) and iron (6.701 mg/L) concentration. Cows with dystocia had significantly ((P<0.05) low mean concentrations of phosphorus (18.782 mg/L), copper (0.449 mg/L), zinc (0.440 mg/L) and iodine (2.245 mg/L). The serum metabolic profile in cows that presented with dystocia also revealed significantly (P<0.05) lower mean concentrations of urea/BUN (7.731 mmol/L), AST (201.1 U/L), creatinine kinase (325.40 U/L) and ammonia (629.38 μmol/L). The hormonal assessment in cows with dystocia showed significantly higher mean concentrations of estradiol (862.09±123.44 pg/ml), oxytocin (370.50±71.66 pg/ml), as well as lower progesterone (8.59±0.402 ng/ml). In cases of downer cow syndrome, concentrations of magnesium, selenium and iron were significantly (P<0.05) higher with respective means of 46.945 mg/L, 22.865 mg/L and 12.688 mg/L. Significant differences were seen in mean levels of urea/Bun (6.891 mmol/L), AST (167.029 U/L), ammonia (822.912 μmol/L) and creatinine kinase (320.294 U/L) which were found to be higher in downer cows. Additionally, significantly (P<0.05) lower mean progesterone (4.40±1.222 ng/ml) and higher estradiol (781.32±135.70 pg/ml) concentrations were noted in downer cows. Significantly higher levels of magnesium (40.606 mg/L), selenium (26.614 mg/L) and iron (5.383 mg/L) were seen in cows having retained placenta. The results also indicated that significantly (P<0.05) lower calcium, high AST and ammonia were noted in cows with retained placenta with mean concentrations of 1.994 mmol/L, 114.643 U/L and 898.571 μmol/L, respectively. The study also found that high prostaglandins (92.06±45.57 pg/ml) and lower progesterone (3.78±0.151 ng/ml) concentrations were significantly (P<0.05) related to incidence of retained placenta. The mean concentrations of phosphorus (27.248 mg/L), zinc (0.642 mg/L) and iron (5.119 mg/L) were significantly lower than the normal range in aborting cows. In addition, mean concentration of calcium (18.179 mmol/L), AST (113.493 U/L), ammonia (686.51 μmol/L) and creatinine kinase (395.058 U/L) were significantly (P<0.05) higher in cases of abortion. Highly significant variations were seen in aborting cows with higher estradiol (1122.99±71.99 pg/ml), prostaglandin (300.41±24.48 pg/ml), oxytocin (574.73±60.65 pg/ml) concentrations as well as lower progesterone (2.45±1.509 ng/ml). The incidences of vaginal prolapse was significantly (P<0.05) related to high selenium (25.638 mg/L) and iron (6.674 mg/L) concentrations, as well as lower concentrations of phosphorus (27.076 mg/L) and iodine (0.335 mg/L). The study also found significantly (P<0.05) lower progesterone (4.67±0.301 ng/ml) and high prostaglandins (241.84±28.35 pg/ml) concentrations in cows presenting with vaginal prolapse. In the study, all six cows in the experimental group (supplemented with MULTIMIN™ + Se +Cu and Calci 50 p.i.) during pregnancy did not experience any reproductive difficulties, whereas two of the cows from the non-supplemented group (control) presented with a retained placenta and dystocia each. The general profile of farmers in the communal areas showed older males, with low educational level and not earning more than a thousand rand per month. These characteristics play a significant role in a production process as they can limit the farmer's adoption of innovative practices due to information inaccessibility and ultimately lower the farmer's contribution to profitable livestock agriculture. The breed, parity, knowledge about brucellosis, feeding system and access to veterinary services may influence incidence of reproductive disorders. Prioritisation of veterinary services through farmer training is necessary for knowledge transfer could help reduce the occurrence of reproductive losses resulting from poor farm management practices in communal farming. The occurrences of abortion, downer cow syndrome, vaginal prolapse, dystocia and retained placenta in communally reared cows are directly related to farm management practices. The measurements of minerals and serum metabolites provide a useful index for studying potential risk related to the occurrence of reproductive conditions and are very important supportive management tools for improving production as well as minimizing animal losses in communal farms. Hormonal disproportion during pregnancy limits and hinders reproductive performance and can be the cause of reproductive disorders and reduced production. The results of this study also suggest that proper mineral supplementation during pregnancy can improve reproductive capacity by increasing the energy and nutrient content in the feed consumed. This study therefore recommends regular determination of mineral, serum metabolites, and hormone levels in expectant cows as important biomarkers for monitoring animal reproductive health. These parameters serve as good and useful indicators for reproductive conditions. In addition, this study provides a guiding tool useful in improving preventive strategies for reproductive conditions, which veterinary practitioners can use to reduce bovine losses and increase reproductive performance. It has also shown that management and adequate mineral supplementation during pregnancy reduces the risk of reproductive conditions in cows reared on natural pastures under semi-arid conditions.