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INTRODUCTION
Hypocuprosis in ruminants is considered to be the second most frequent mineral deficiency in grazing bovines throughout the world, second only to phosphorous 1. The deficiency of this mineral was reported in central Cuba in the soil-plant-animal axis 2. Cu deficiency was later found in 100% of soil and grass samples, and in 75 and 72% of blood serum and blood tissue samples, respectively 3,4.
High percentages of livestock with copper deficiency in blood serum were also found in the eastern provinces of Cuba 5. Studies conducted in various agro-ecosystems, which are characteristic of bovine livestock farming in the province of Villa Clara, detected a Cu deficiency in soil, grass and animals in pre-mountain and plain ecosystems; this deficit was associated with reproductive and productive problems 6.
Parenteral copper supplementation increases blood copper, daily weight gain and weaning weight in calves 7, but a separate publication states that it did not have an impact on these productive parameters, although it did increase copper serum concentrations in this bovine category 8.
Copper and zinc parenteral supplementation in growing Brahman females and males did not improve weight gain and had no impact on thoracic perimeter and haunch height 9. Conversely, the Cu injection, whether on its own or combined with Zn and Mn in calves, increased serum Cu and Zn, hemoglobin, hematocrit and weight gain levels 10.
Facing these discrepancies, it is necessary to deepen these studies using other bovine categories, sex and management and feeding systems; therefore, the purpose of this study is to assess the effect of parenteral Cu supplementation on the bio-productive behavior in intensive fattening bulls under the current Cuban livestock farming conditions.
MATERIALS AND METHODS
Experimental Design. Work was carried out in a bovine feedlot located in the province of Villa Clara in the central region of Cuba during the low rain season (November to April), between 22º 53 LN and 82º 02 LW, at an altitude of 90 to 100 meters above sea level, and during the rainy season (May to October) in which precipitation amounts to 73% of the annual 1530 mm (4.6); according to these authors, brown carbonate soils and the mixed Holstein x Zebu bovine genotype are predominant in the experimental area.
Experimental Design. 50 mixed Holstein x Zebu bulls (5/8Hx 3/8Z) were selected, all 18 to 20 months old and with a live weight of 210 to 220 kg, clinically healthy according to clinical diagnosis 11 and none of which were under medical treatment.
2 groups, each with 25 animals, were put together. Group A was the control group and Group B received a 50 mg Cu subcutaneous supplement; the first supplementation took place at the beginning of the experiment, and was repeated every 60 days until it was administered three times. The effects of injectable copper on animal blood chemistry indicators and weight gain were measured.
Management System. Animals were managed in an intensive feeding system, where they were semi-confined and remained in stables during 18 hours, from 12 m to 6 am during which corn DDGS (1.5 kg MS) was administered. Furthermore, they were offered final syrup, a mixture of 50% sugar cane forage and pre-milled CT-115, ordinary salt and water; all consumed voluntarily.
Animals were grazed during the cooler hours of the morning, at which time the confinement period facilities were cleaned, between 6 am and 12 m. Rotational time-restricted grazing was applied, using natural pastures, with a predominance of the Botriocloa-Dichantium and other less representative species.
Sample-taking and analytical processes. Blood samples were taken at the beginning of the experiment and 60 days after the last treatment, by way of jugular venipuncture. 10 ml were extracted for mineral analysis, and were then placed in sterilized and de-mineralized anticoagulant-free vacutainer tubes; they were then centrifuged at 3500 g (rpm) for 10 minutes, after which blood serum was taken, which was frozen at -10°C until the time of analysis. 5 ml of blood were taken for blood analysis, which were placed in previously sealed and sterilized test tubes with EDTA (1 mg/1ml of blood)
Zn, Fe and Cu levels in blood serum were determined using atomic absorption spectroscopy 12 on a SP-9 (PYE UNICAM) device. Blood indicators were determined on an IDEXX VetAutoread™ (IDEXX LABORATORIES VetLab ® USA) Device. All blood chemistry analyses were performed according to manufacturer´s procedures and the use of commercial kits; at the Centro de Investigaciones Agropecuarias - CIAP (Center for Agricultural and Livestock Research), Faculty of Agricultural and Livestock Sciences (CIAP), Universidad Central “Marta Abreu” in Las Villas, Cuba.
Live weight (LW) in animals was measured on a monthly basis until 180 after the first supplementation was administered, using the methodology described by Ozcaya and Bozkurt 13. Weight gain and final weight were analyzed in each animal to assess the effect of the treatment on these indicators.
The nutrient balance was carried out considering food availability, grass intake was determined according to the indications of Pérez-Infante 14, and the difference between food supplied and food rejected was used for all other food types, results were processed using the CALARC program, see 1.0 15.
Statistical Processing. A comparison of blood chemistry indicators was carried out at the beginning and at the end of the experiment, as well as weight and GMD at the different weighing times of animals between the 2 treatment groups using the t-Student test for independent samples. The Statgraphis Centurion statistical package was used for processing. See XV.II 16.
RESULTS
Figure 1 shows the nutrient balance at the beginning of the experiment; note that the food supplied at this time covers the aspired weight and live weight gain requirements. Nevertheless, there is a 104 g surplus of digestible protein of easy fermentation in rumen (PDIN).
The food that is being consumed by animals does not meet Cu requirements, with a deficit of 2.6 mg/kg MS considering that the concentration of this element in food is only 1.27 mg/kgMS (Figure 2).
Blood chemistry studies (Table 1) show that there were no significant differences between any of the indicators at the beginning of the study; yet, blood copper, hemoglobin and hematocrit increased significantly (p<0.001) in the treatment group at the end of the study when compared to the control group. Fe and Zn were not impacted by the therapy employed.
Table 1 Blood chemistry variable behavior assessed in the different treatment groups.
| Variables | Time | Groups | |
|---|---|---|---|
| Control | Treatment | ||
| Copper (µmol/L) | Initial | 11.74±1.21a | 11.63 ± 1.24a |
| Final | 11.22 ± 0.86b | 13.81± 2.21a | |
| Zinc (µmol/L) | Initial | 14.63 ± 1.82a | 14.64 ± 1.92a |
| Final | 15.72 ± 1.29a | 15.69 ± 1.44a | |
| Iron (µmol/L) | Initial | 19.07 ± 3.45a | 17.32 ± 2.88a |
| Final | 19.42 ± 2.05a | 20.71 ± 3.13a | |
| Hb (g/L) | Initial | 101.53 ± 4.74a | 103.46 ± 11.89a |
| Final | 105.3 ± 8.54b | 119.73 ± 12.32a | |
| Hto (L/L) | Initial | 0.31 ± 0.02a | 0.31 ± 0.03a |
| Final | 0.31 ± 0.01b | 0.37 ± 0.03a | |
| ab different letters in the same row indicate significant statistical differences * p<0.001 (t Student for independent samples) | |||
The weight study of bulls among the study groups (Table 2) showed that animals in the treatment group had a significant (p<0.01) increase in body weight at every weighing time when compared to the control group. Weight gain was between 4.86 and 9.56% at the various weighing times.
Table 2 Bull weight comparison (kg) between treatment groups at different sampling times.
| Time (days) | Control | Treatment | Increase % |
|---|---|---|---|
| 30 | 226.80 ± 11.12b | 237.88 ± 7.79a | 4.86 |
| 60 | 240.08 ± 11.82b | 253.36 ± 8.14a | 5.53 |
| 90 | 265.96 ± 12.92b | 281.52 ± 9.92a | 6.03 |
| 120 | 291.40 ±14.42b | 311.72 ± 11.48a | 6.87 |
| 150 | 316.96 ±16.04b | 343.88 ± 12.51a | 8.54 |
| 180 | 345.60 ± 17.24b | 378.12 ± 14.81a | 9.56 |
| ab different letters in the same row indicate significant statistical differences * p<0.001 (t Student for independent samples) |
Daily weight gain in each group is illustrated in table 3. Each weight measurement is higher (p<0.01) in the treatment group than in the control group.
Table 3 Bull GMD comparison (g) between treatment groups at different sampling times
| Time (days) | Control | Treatment |
|---|---|---|
| 30 | 373.33 ± 117a | 408 ± 54.67a* |
| 60 | 442.66 ± 64.92b | 516 ± 66.05a* |
| 90 | 862.66 ± 136.53b | 938.66 ± 72.44a* |
| 120 | 848 ± 104.5b | 1006.6 ± 103.63a* |
| 150 | 852 ± 117.8b | 1072 ± 98.92a* |
| 180 | 954.66 ± 139.73b | 1141.3 ± 111.08a* |
| Total | 722.2 ± 72.2b | 847.1 ± 57.4 a** |
| ab different letters in the same row indicate significant statistical differences (t Student for independent samples) p<0.01. ** p<0.001 |
DISCUSSION
The feedstuff provided as food meets the intended weigh and live weigh gain requirements, and exceeds the energy, PDIE, Ca and P. requirements. Nevertheless, the excess 104 g of digestible protein that is easily fermented in the rumen (PDIN), which favors sulphur concentrations in the rumen as a result of the increased microorganism activity. S is an important component for thyomolybdate formation, and is considered to be one of the main Cu antagonists 17.
In addition to the negative effects of excess PDIN, which favors the concentration of S and causes conditioned or secondary Cu deficiency, we must also add that the food that the animals are consuming does not cover Cu requirements 18, with a deficit of 2.6 mg/kgMS.
Dietary Cu concentration is only 1.27 mg/kgMS, and this amount should be greater than 5 mg/kgMS in order to maintain at least marginal concentrations of this microelement in the liver and in blood serum; furthermore, voluminous food amounts between 7 and 14 mg/kg are inadequate 18.
Blood chemistry profiles highlight the beneficial effects of parenteral Cu supplementation on these indicators, and they match results obtained in previous studies, where administering 125 mg of Cu to cows, repeating treatment at three months; increased Cu blood serum concentrations by 5 mg/kgMS 19,20. Parenteral Cu supplementation in calves increased blood copper 7 and Cu; and, on its own or in combination with Zn and Mn, it increased Cu and Zn serum levels, hemoglobin and hematocrit.
In studies conducted in Cuba, parenteral Cu administration on grazing adult dairy female bovines, increased (p<0.001) their blood serum Cu concentration, hemoglobin and hematocrit, and it benefitted their reproductive behavior, where they had higher reproductive efficiency indicators. The supplement had a protective effect on anestrous presentation and the repetition of Artificial Insemination services 3,21,22.
In the case of Fe, results are in contrast with studies conducted in Cuba on grazing adult bovine females, where parenteral Cu supplementation increased serum Fe concentrations 2,21,22. Although there is a close relationship between blood copper and Fe blood levels 1, the lack of coherence in these results may be explained because Cu was administered in this study, animals were kept in stables for 18 h, with very little contact with the soil, where bovines can consume Fe while grazing, and because this mineral, which is present in the plant, is oxidized when the plant is milled 1,23).
LW and GMD weight increases are low for the breeding system used; nevertheless, these are greater in animals that received a parenteral Cu supplementation; which indicates that the supplement administered has a beneficial effect on these indicators.
The results of this study match the results of other studies where parenteral Cu supplementation in calves GMD weight and weaning LW 8,21, and administering this microelement, alone or in combination with Zn and Mn, increased GMD weight 10. In contrast, the injectable Cu 8,23 and Cu and Zn 10 treatment did not improve weight GMD in bovines that received supplementation.
The variability in the answers found in the bibliography reviewed could be due to the initial Cu status in animals, considering that different microelement combinations and different dosages and administration frequencies were used. Soil and weather and temperature conditions; and animal age, category and sex also changed between experiments, which also had different handling and feeding systems.
All of these factors possibly had an influence on the difference found between results. Positive responses to injectable Cu treatment were reported in all deficiency ranges, but GMD weight differences were related to the seriousness of Cu deficiency and the time of year in which the study was conducted 23.
In conclusion, a 50 mg parenteral Cu supplementation increased Cu serum levels, hemoglobin, hematocrit and weight gain in fattening bulls.
