Evaluación de concentrado lechero para mejorar la eficiencia productiva de vacas lecheras y el forraje de sorgo como ensilaje

Abstract

The dairy industry in Puerto Rico is the main agricultural industry of the country, with approximately 30% of the island gross agricultural income. The cost of feed in Puerto Rico is the most important limiting factor for the dairy industry. The diet of dairy cows consists of an actuated combination of forage and concentrate. Together promote an increase in milk production. Corn or sorghum silages are sources of quality forages which are used in the diet of dairy cows. Concentrates with high energy value are commonly used to promote high milk production in cows. We carried out two experiments; the first consisted in evaluating sorghum silage as possible source of quality forage. The other with the purpose of evaluating milk production efficiency using 2 types of concentrates and 2 levels of supplementation in dairy cows consuming corn silage. In the first experiment 4 crops were evaluated using 4 varieties of sorghum and one of maize (first crops only). The four varieties of sorghum had similar data affecting pH, relative humidity (RH) and Volatile fatty acids (VFA’s) composition. The varieties had a high level of RH, (> 70 %) affecting fermentation, producing unwanted butyric acid type fermentations (concentration of butyric acid was > 0.10 %). However, the products of lactic acid obtained was in the desire concentration as well as acetic acid (> 3.00 % and < the 3.00 % respectively). It is concluded that these varieties of sorghum are of good quality and are comparable to the corn silage. In the second experiment, 12 Holstein cows where given to 2 types of concentrates; half of the cows where given high energy concentrate (CA) and the other half where given a concentrate with 50% of wheat bran (CB). At the same time they were given 2 different levels of supplementation; high supplementation (NA) and lower supplementation (NB). No significant differences were observed due to the type of concentrate, but differences were observed due to the level of supplementation. Animals consuming the NA had greater consumption of concentrate (9.27kg/d) that the animal in NB (7.19kg/d). There was no significant differences in milk production, but did in terms of productive efficiency. Animals consuming the NB were more efficient (3.50kg/d) that the animal in NA (2.71kg/d) of supplementation. Therefore, the animals in NB convert more pounds of food to milk while the animals in NA probably used the energy to gain weight instead of producing milk. Moreover, milk production CB treatment with NB (22.88kg/d) was more efficient than CB with NA (20.69kg/d). This could be applied to the high concentration of wheat bran that could had created a negative effect on CB with NB, because CB was a concentrated with 50% wheat bran. No significant differences were observed in milk composition of %PC, %fat or %total solids, which mean that neither the type of concentrate nor the level of supplementation had an effect the milk composition. However, nitrogen from urea in milk (NUM) was higher when used with CA with NA. This was probably due the high amount energy in this treatment. This experiment, suggests using a combination of CB with NB because that was a treatment of higher conversion efficiency. This reduces the cost of production, because this concentrate was 50% wheat bran which is relatively cheaper than the corn found in the high energy concentrates.