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To achieve the increase of the productivity of herds with viable technologies of minimum external inputs and under tropical conditions, one of the strategies is to be able to determine the most suitable genotypes or breeds under different production systems or specific environmental conditions (Hernández et al. 2012). An example of this is the genotype Siboney de Cuba (5/8 Holstein and 3/8 Cebu), created to have an animal capable of adapting favorably to the warm-humid conditions prevailing in Cuba. Its adaptation and resistance is also manifested in tolerance to parasitic diseases, longevity, low mortality, high fertility and adequate birth weight. It is currently the largest synthetic breed that exists in the country's commercial and genetic dairy herds (Fraga 2015). However, the livestock of Cuba suffers a prolonged undernourish process and the management conditions are not optimal for this genotype to develop its potential. All this limits the contribution of nutrients and involves metabolic alterations that directly or indirectly affect the productive and reproductive processes (Balarezo et al.2016).
It is important, from these antecedents, to carry out studies that provide knowledge about the intermediary metabolism of dairy herds, as a tool to diagnose nutritional state and develop feeding strategies during the most critical periods of the year.
The determination of metabolic profiles allows knowing the presence of these alterations, especially in their subclinical states, reason why its use is extends in many countries. In Cuba, the studies of Viamonte et al. (2010), García et al. (2011) and Noval et al. (2016) are of interest, which relate important metabolic aspects with the health, production and reproduction of female cattle. However, there are few the researches that deal with comprehensive study of the energy, protein and endocrine metabolism in different physiological states, in relation to their nutritional requirements. The objective of this study was to evaluate the blood concentrations of glucose, cholesterol, triglycerides, total proteins and insulin- like growth factor 1(IGF-I) in lactating and dry Siboney de Cuba cows.
Where:
μ |
- constant common to all observations |
Gi |
- effect of the ith group i = 1, 2, 3 |
NPj |
- effect of the jth unit j = 2, 3, 4, 5 |
eijk |
- residual error, normal and independently distributed with zero mean and variance σe 2 |
The restrictions applied to the used models were:
Materials and Methods
Location, animals and study stage. The study was carried out in the experimental unit "Genetico 4", belonging to the Instituto de Ciencia Animal of the Republic of Cuba. A total of 52 not pregnant and multiparous Siboney de Cuba cows were used. The study was carried out during October and November 2016. The average rainfall during the period was
93.65 mm of rain, while the average temperature and relative humidity were at 23.1°C and 78 %, respectively.
Management and Feeding. The production system was developed in a semi-intensive way, with rotation of paddocks and stocking rate of 2.5 UGM hectare-1. The animals intake grasses as staple food, with predominance of Penisetum CT-115 (Cenchrus purpureum), and star grass (Cynodum nlenfuensis). Irrigation and fertilization was not applied during the experimentation period. The animals in production were supplemented at a rate of 400 grams of commercial concentrate with 16 % of CP and 11.64 MJ/ kg of DM-1 of metabolic energy, from the fourth liter of milk and fractionated in each milking. The non- lactating group intake 0.5 kg of the same supplement in a single dose in shade buildings. Mineral salt and water were offered ad libitum.
Experimental design, processing and analysis of samples. Three groups (G) of animals were made, according to the physiological state. The GI (n = 18) and GII (n = 22) dry cows and between 45 and 60 d of lactation, with live weight and average milk production of 412.5 ± 16 kg, 405 ± 21 kg and 7.3 ± 1.2 kg , respectively. The GIII (n = 16) was designed with animals higher than 150 d of lactation, with milk production and average live weight of 3.5 ± 0.9 kg and 436 ± 24 kg, respectively. The diagnosis of the genital organs was made by transrectal ultrasonography (Pie Medical® Ultrasound), with a probe (linear catheter) of 7.5 Mhz. All the animals had between two and five parturitions.
Blood samples (10 mL.) were extracted by jugular vein puncture and transported (test tubes) in refrigeration to the laboratory, where they were centrifuged at 3000 revolutions per minute (rpm) for 15 min. for obtaining the serum. The serum concentrations of glucose and total cholesterol were determined by the Oxidase/Peroxidase method, while triglycerides and total proteins were obtained from the Glycerol-3-Phosphate-Oxidase and Biuret procedure, respectively. The biochemical analyzes were performed by visible light spectrophotometry (Stardust MC 15 Semiautomatic Spectrophotometer). The determination of IGF-I was performed by radioimmunoassay, using a solid-phase gamma counter (RIA Cobra II).
Statistical analysis. The data were analyzed by means of GLM of the statistical package SAS (2007), version 9.1.3 by analysis of variance, for which a linear model of fixed effects was used. The factors studied by the model were: group (1, 2 and 3) and parturition number (2, 3, 4 and 5). The multiple comparison test of means with a level of significance for P <0.05 (Kramer 1956) was used.
Results and Discussion
The statistical analysis showed that the group effect (P <0.05) was significant for the concentration of the metabolic indicators studied (table 1). However, the same performance was not observed with the number of parturitions (P> 0.05). Studies by Hernández et al. (2011) showed that primiparous animals require higher demand of nutrients to complete their growth and maintain milk production. In this study, only multiparous cows were used, between two and five parturitions. It is possible that this condition could be the reason that the number of parturitions did not show significant effect.
The animals, between 45 and 60 d of lactation, showed lower concentrations of glucose (P =0.0001) and triglycerides (P <.0001) than those with more than 150 d of production (table 2). Similar results reported Park et al. (2011) and Fonseca et al. (2016). The high levels of production at the beginning of lactation, as well as the decrease in intake, generate an exaggerated mobilization of these intermediary metabolites towards the mammary gland, as a substrate for milk synthesis.
The dry animals showed lower concentrations of triglycerides than the cows with advanced lactations (P <.0001) (table 2). This performance does not coincide with Park et al. (2011) studies, who state that during the dry period the energy balance is generally positive, which conditions states of lipogenesis in adipose and hepatic tissue, increasing blood triglyceride concentrations. The non- lactating group (GI) showed an unfavorable body condition (2.5 pts) (Houghton et al. 1990), with deficiencies of adipose tissue in different anatomical regions of the body, which indicated that the animals did not recover from the previous lactation.
Table 2 Blood concentrations of glucose, cholesterol, triglycerides, total proteins and IGF-I in cows with different productive periods.
Means with different letters between rows differ significantly P < 0.05 (Kramer 1955).
Physiological range (Source): Research Animal Resources
The concentrations of plasma cholesterol did not show differences (P> 0.05) in the lactating groups (GII and GIII) (table 2). Similar performance was obtained by Souza and Birguel (2009), who observed stable cholesterol values from 45 d postpartum. However, both groups showed higher concentrations than non-lactating animals (P = 0.0011). Matoba et al. (2012) verified the existence of a close relation between the productive increase in dairy cows and the values of total cholesterol, weight loss and body condition. The highest cholesterol values are gradually showed during the postpartum period, which are related to a negative energy balance, because of an exaggerated mobilization of lipid body reserves, in order to compensate the energy deficit imposed by lactation. Its stability is observed once energy recovery begins, unlike other metabolism components such as glucose, which may take longer to reach stable values after parturition.
The dry animals and with more than 150 d of lactation showed higher concentrations of total proteins (P = 0.0087) with respect to the group between 45 and 60 d of production (table 2). Zambrano and Marques (2009) obtained similar results, when studying the serum and fractionated proteins from 17 to 78 d and from 110 to 153 d postpartum. Similarly, Oliveira et al. (2014) found decreased albumin at the beginning of lactation. This performance could be due to the transfer capacity to the mammary gland of protein and immunological elements for the formation of colostrum and milk later, as well as the use of glucogenic amino acids to compensate the energy deficit during the postpartum first weeks. However, when decreasing milk production and the negative energy balance, there was an increase in the concentrations of these biochemical compounds.
Cows with more than 150 d of lactation showed higher values of IGF-I (P <.0001) and ovaries with cyclic activity, with respect to dry animals and between 45 and 60 days of production. Similar results were found by Franco et al. (2014), who report that blood concentrations of IGF-I are related to nutritional state and ovarian functionality. In general, the results show that the feeding system used does not guarantee the energy demands for cows during early lactation.
It is concluded that animals in different physiological states show variations in the concentrations of some indicators of energy, protein and endocrine metabolism, mainly due to the level of mobilization of their body reserves, as a consequence of the metabolic balance between nutrients intake and required energy. It is recommended to develop feeding strategies based on the physiological stages of the productive cycle, with the objective of attenuating the metabolic imbalances and improving the productive and reproductive performance of the dairy herds in Cuba.
