The products from the sea represent an important economic activity for countries that have extensive coastlines. However, in the last decade, shrimp culture has developed exponentially throughout the world, more than any other livestock production sector.
According to the National Fisheries Institute, approximately 79 % of the total shrimp catch in Mexico is from the Mexican Pacific, with Sinaloa accounting for 46.9 % of the national production, and of this, a large part of the production is exported to the United States of America such as frozen shrimp with head and peeled shrimp, for a value of 286 million dollars (SAGARPA 2016).
The shrimp cleaning process generates losses of more than 20 % of the product weight. It is estimated that the cleaning wastes generated during the industrial benefit of shrimp reaches 60 thousand tons per year, currently becoming an environmental problem in the region (Domínguez 2017).
According to Jafari et al. (2012), the shrimp wastes formed by the carapace, telson, cephalothorax and residual meat, resulting from industrial processing, constitute a natural source of protein, minerals, chitin and rich in carotenoids pigments. Elements that have made possible to take full advantage of this waste in monogastric animals feeding. However, they have been little studied in ruminant species.
The experiment was carried out at the facilities of the zootechnical post and the laboratories of Facultad de Agronomía de la Universidad Autónoma de Sinaloa, located at km 17.5 of Culiacán-El Dorado highway in Culiacán city, Sinaloa, Mexico.
The ruminal degradability was determined through the nylon bag technique described by Mehrez and Orskov (1977) and the effective degradability by McDonald (1981), considering a fractional passage rate from the rumen and speed of 2 and 4 %. For the incubation of the sample four bulls from Brown Suisse breed were used with a weight of 700 ± 25 kg of live weight and fistulated in rumen fed with commercial concentrate (2 kg anim. day -1), forage of Sudan grass (Sorghum sudanense), water and mineral salts ad libitum. The introduction of the bags was in triplicate and in reverse order (72, 48, 24, 18, 8, 4, 0h) to then collect all at the same time. The hour 0 was carried out in a bain-marie at 39 °C. A total of 84 bags were used and each one (17 x 4 cm) contained 5 grams of sample with a particle size of 2 mm and a porosity of 50 μm. To the total waste, a proximal chemical analysis was determined before and after the incubation (dry matter, organic matter, crude protein, crude fiber, ash and metabolizable energy) according to AOAC (2005).
The results of degradation during the incubation kinetics were analyzed by analysis of variance and the Duncan test (1955) was applied to establish differences between means. All the data were processed using the statistical package INFOSTAT (Di Rienzo 2012). The NEWAY EXCEL program was used to determine the parameters of the degradation model (Chen, 1997).
Table 1 shows that shrimp meal shows high content of organic matter (OM), a fraction that influences on the amount of substrate available for the fermentation of ruminal bacteria and with the possibility of extending the degradation of the supplement with the inclusion of shrimp waste meal (SMS). The OM values reached are within the range established by the literature that ranges from 67 % to 80 % (Carranco et al.2017). However, they are higher than those obtained by Estrada et al. (2017) for blue crab meat waste meal (53 %) and similar to those of fish meal (74 %) proposed by Cabello et al. (2013) and less than the giant squid (91 %) evaluated by Calvo et al. (2016).
Similarly, it is observed that ash with a value of 24.79 % and ME with 10.05 MJ are in the range of values considered adequate, according to the literature for shrimp waste meal (Espinosa-Chaurand et al. 2015).
On the other hand, the crude protein was the nutrient that was found in higher proportion in the meal of shrimp waste with 53.39 %. Value slightly higher than those reported in the literature which ranges from 30.07 to 50.06 % (Salas-Duran et al. 2015 and Carranco et al.2017). This difference could be attributed to the area of production and capture, season of the year, climate, age and species of shrimp. However, Salas-Duran et al. (2015) mentioned that the amount of heads and cephalothorax in the shrimp waste meal is a factor that varies the percentage of protein, since a higher number of heads increases the values, while higher number of cephalothorax decreases it. In comparison with other waste meals from the sea, there is similarity with fish meal (Cabello et al. 2013). However, they are higher than those reported by Estrada et al. (2017) for blue crab meat, but lower than those contributed by the giant squid meal Calvo et al. (2016). When analyzing the parameters of degradability (table 2) it was observed that the value of the soluble fraction (a=17.24 %) made possible the rapid disappearance of the potentially degradable fraction (a+b= 83.87 %) and the shorter time of ruminal incubation, which shows the existence of highly fermentable substrate, able to ensure from the beginning the degradative activity of ruminal microorganisms. Although, the value of the insoluble fraction, but degradable potential (b = 66.63 %) of the DM in rumen contributed with more than half of the fraction a+b. On the other hand, it was observed that both the fraction ¨b¨ and ¨a + b¨, shows resistance to the microbial attack of food in the rumen, favoring, that part of the supplement be subsequently digested in the intestine.
When comparing these values with those of other supplements with inclusions of animal meals, it was observed that with the inclusion of fish meal in a concentrate Aguirre et al. (2017) reported that the fraction a (20.42), fraction b (37.12) and “a+b” (57.54), were lower than those of this study. However, they are similar to those evaluated by Ramírez and Giraldo (2017) for a supplement composed of Kikuyo grass (Penisetum clandestinum) and castor bean cake as a protein source.
The degradation rate (2 % h) obtained in this study corresponds to foods of medium quality, but lower than the evaluated supplements, which could be related to the chitin in shrimp wastes and the time required by ruminal microorganisms to degrade it (Piloni 2008). On the other hand, the ruminal turnover rates that oscillate in 64 and 60 % show their nutritional quality and the value of their use in dairy cows.
It is concluded that the parameters reached of dry matter degradation confirm the possibility of using the supplement with the inclusion of 30 % of the shrimp waste in ruminant animals feeding, although the degradability of the rest of the nutrients should be characterized and carry out field tests with animals in production.