INTRODUCTION

Cavia porcellus is a rodent mammal, herbivorous with twilight habits, native to the Andean zone, made up of Bolivia, Ecuador, Colombia and Peru; where it is part of the local gastronomy (^{Sánchez et al., 2012}). In Mexico it adopts the common name of cuye or cuyo; it reproduces to be commercialized as a companion animal, because it adapts easily to confined spaces, but its food requirements are complex (^{Guevara et al., 2014}). Guinea pigs have a glandular stomach, which degrades simple carbohydrates by enzymatic action, but is a post-gastric fermenter, due to its blind degradation of complex carbohydrates through bacterial fermentation (^{Meza et al., 2014}). Therefore, your diet must contain adequate amounts of fiber; in addition to vitamin C that your body cannot synthesize due to the lack of L-gulonolactone oxidase (^{Quintana et al, 2013}).

Guinea pigs are generally fed fresh vegetables, such as cabbage, chili peppers, lettuce or carrots; sometimes they feed on hay, pasture, fresh or dehydrated alfalfa (Reséndiz ^{and Hernández, 2008}). Sometimes they feed it with diets prepared for rabbits, pigs or with mixed diets (^{Reyes et al., 2018}). But their poor diet can cause liver problems, kidney problems or conditions associated with chronic nutritional deficiencies. Therefore, balanced foods for their species meet the specific nutritional requirements capable of improving their life and the general condition of their species (^{León et al., 2016}).

The body, by receiving the appropriate nutrients, can carry out efficient metabolic maintenance processes, but if it has nutritional deficiencies, they can manifest themselves in different ways. In guinea pigs, nutritional deficiencies can be identified in their hair, measuring the stage of active growth known as anagen, due to the independence of the active follicle cycle and its duration (^{Jackson and Ebling, 1971}). Its body decreases collagen production if your intake of ascorbic acid drops for two to three weeks, because it synthesizes the coenzyme for the sub-hydroxylated collagen precursor (^{Harwood et al., 1973}; ^{Grosso et al., 2013}). By receiving a diet deficient in vitamins caused by ingredients in the diet, its hair can modify its active growth, indicating its state of health.

When balancing the food, protein, energy, minerals and vitamins are mixed in a balanced way (^{Marsanasco et al., 2011}). The variety of balanced foods for guinea pigs in Mexico is limited, both in presentations and possibly in their nutritional requirements. Developing a maintenance feed is suitable for the species, if it is pelleted, less is wasted, it is of high density, it does not allow the selectivity of the ingredients for the tastes of the animals ^{Reséndiz and Hernández, 2008}; ^{Tarrillo et al., 2020}).

Adding molasses as an energy ingredient in commercial guinea pig feed is common, due to its low cost. It is also an energetic that provides a characteristic sweet smell to improve its palatability. However, its characteristics may interact with the added Vitamin C, making it difficult to mix and distribute micro ingredients in the final product (^{Bonilla and Usca, 2015}). An alternative as an energy source can be crude soybean oil, which in addition to providing energy to the diet, contains linoleic acid and facilitates food preparation, but at higher costs compared to molasses.

Therefore, the objective of the research was to know the effect of molasses or soybean oil as energy sources, combined with two levels of vitamin C 100 mg/Kg and 300 mg/Kg of food in diets for the maintenance of Cavia porcellus .

MATERIAL AND METHODS

Capillary permanence

To know the changes in the health status of the guinea pigs, a sample of 100 hairs was taken at the beginning and end of the experiment. The sixth and eighth dorsal vertebrae were used as sampling zones, a straw and a hemostat were used to exert pressure on the base of the hair and extract it in its entirety. The samples were placed on a slide, they were hydrated, and a coverslip was placed on them to know their growth status in anagen (figure 1).

Figure 1 Guinea pig hair base extracted from the skin in Anagen at 10x 

RESULTS

There was no effect of the concentrated source of energy and level of vitamin C on the body weight of the animals during the four weeks (table 2). The addition of molasses with 100 mg of vitamin C increased (P≤0.05) the feed consumption the first week (table 3), but in the third week the consumption of feed with soybean oil and 100 mg of vitamin C (P ≤0.05). In the first and second week, the guinea pigs consumed less food (P≤0.05). During the experiment there was no mortality and the capillary permanence in its anagen state did not show differences at the end of the treatments (data not shown).

DISCUSSION

The body weight of guinea pigs is related to their race, sex, zootechnical purpose and type of food received. The ^{NRC (1995)} and ^{Morales et al. (2011)} evaluated two energy levels: 2.8 and 3.0 Mcal per kg of food in isoprotein diets, obtaining greater weight in animals by ingesting more energy. Guinea pigs do not receive an adequate diet for their physiological state, they weigh less; therefore, by eating a food suitable for your body mass, it will increase, as happened in the study, due to the effect of your previous diet. Therefore, the guinea pigs did not gain weight, they only adapted to a balanced diet; their weight gain per day was 2.5 g, an adequate gain for a maintenance diet, compared to fattening animals that gain 30 g of weight per day with adequate food.

^{Airahuacho and Vergara (2017)} report that guinea pigs used as pets should ingest less than 2.9 Mcal of ED to limit their weight gain. ^{Camino and Hidalgo (2014)} evaluated guinea pigs in fattening with different genotypes, showing their efficiency, increasing 15 g per day.

In the present study, the diet was balanced to comply only with the maintenance of the animals, therefore there were only minimal weight gains; what is emerging as a suitable food for maintenance in type B guinea pigs; animals with little muscular development, elongated triangular head, shallow body depth, ears with different sizes and nervous animals (^{Chauca, 1997}).

Food consumption is a base measure to evaluate a diet and is evidenced by the preferences of the animals. ^{Guevara et al. (2013)} used fish oil and their guinea pigs ate 41.85 to 43.71 g of food per day. In this research, the daily food consumption was 28.37 and 29.75 g with molasses and soybean oil, data that exceed those reported by ^{Quintana et al. (2013)} and similar to those of ^{Guevara et al. (2013)} who investigated that using shrub plants in the diet obtained intakes of 24.22 to 29.50 g/day. Guinea pigs can consume up to 56.96 g of food per day, as reported by ^{Morales et al. (2011)}; but ingredients suitable for guinea pigs should be used during the preparation of the diet.

The difference in food consumption can vary, due to the concentrated source of energy used in the experiment, its extra caloric effect produced by soybean oil or molasses can reduce food consumption, increase the time of ingestion in the digestive tract improving your digestion. A disadvantage of soybean oil for making guinea pig feed is its price compared to molasses. Using 3 or 4% molasses in food for guinea pigs is common, it is an adequate caloric intake and higher doses can cause the rejection of the food; furthermore, it is possible that guinea pigs may like the aroma of molasses.

Guinea pigs need vitamin C to meet their maintenance needs and to keep their health balanced. ^{León et al. (2016)} evaluated 450, 550 and 660 mg/kg of feed and conclude that 450 mg/Kg cover the requirements in guinea pigs. This amount is a high dose, compared to that used in the present study of 100 and 300 mg/kg of food without showing negative signs in the animals. It is possible that the doses of vitamin C are not adequate and the animals have lower requirements. ^{Silva and León (2015)} compared 500 to 1100 mg of vitamin C in kg of balanced food, a dose ten times higher than that used, and found greater food consumption and weight gain at 900 mg per kg of food. In the present experiment, a similar effect was presented when increasing from 100 to 300 mg of vitamin C, but only the first week.

There are different approaches to the levels of vitamin C that guinea pig feed should contain. The ^{NRC (1995)} suggests 200 mg/kg of food in balanced diets, approximate doses to those used in this study. The doses of vitamin C used in this experiment possibly did not cause apparent lesions or deficiencies in the four treatments, due to the exposure time of the guinea pigs and proper handling of the animals. ^{Mattos et al. (2003}) mention that vitamin C levels should increase according to the stress that the individual has, mainly when there are sudden changes in temperature or intense driving. ^{Guevara et al. (2014}) used 50 and 100 mg/Kg of feed without having an effect on the weight of the animals; Similar results to those reported in the present experiment at doses of 100 and 200 mg/Kg. However, ^{León et al. (2016}) evaluated 0, 450, 550 and 660 mg/kg of vitamin C with higher food consumption and weight at the 450 mg/kg dose. The ^{NRC (1995)} suggests 200 mg per kg, but they have increased the dose to 800 mg, reporting weight gain at 200 and 350 mg. The results obtained in the investigations vary due to the ingredients used to elaborate the foods that can affect the consumption of the guinea pigs and their yields.

The hair in guinea pigs has aesthetic importance because it indicates their state of nutrition and general health. ^{Vivas and Carballo (2013)} recommend vitamin C administered through food every day with doses according to its productive stage to avoid hair loss.

In the present study, no nutritional deficiencies were observed in capillary permanence in its different growth stages at the end of the experiment. This can be explained by a correct nutrition and maintenance of the organism that feeds the collagen cycle to maintain the adequate hair follicle that projects a phenotypic and genotypic capillary expression adequate to the species studied in anagen (^{Grosso et al., 2013}).

CONCLUSION

The addition of soybean oil or molasses as a concentrated source of energy combined with 100 or 300 mg of vitamin C per kg of pellet feed does not affect body weight, feed consumption or capillary permanence in guinea pigs. However, it is necessary to continue investigating the amount and type of energy used in specialized foods for the species with different doses of vitamin C.