Vital organs and gastrointestinal tract of feedlot finished Charolais x Nellore culling crossbred cows slaughtered at different weights

The objective of this experiment was to study the development of vital organs and gastrointestinal tract Of Culling crossbred cows from the second (G2: 3/4Charolais (C) Nellore (N) and 3/4NC) and third (G3: 5/8CN and 5/8NC) generations of C x N rotational crossbreeding. Animals were feedlot finished and slaughtered with 465 (T465), 507 (T507), and 566 kg T566) of body weight (BW). At the beginning of the trial, age, BW, and body condition averaged respectively, 8.5 years, 388.6 kg and, 2.35 points. Animals were fed a 48:52 forage:concentrate ratio diet containing 12.5% crude protein and 2.99 Meal of digestible energy per kg of dry matter. Liver showed the greatest development among the studied organs. Lungs and spleen showed high development until animals reached 507 kg BW (T507) but reduced at 566 kg BW (T566). Increasing slaughter weight reduced the proportion of internal organs and gastrointestinal tract in the total BW and empty body weight (EBW). G3 animals had heavier reticulum-rumen and stomach (reticulum-rumen+omasum+abomasum) (14.29 vs. 12.30 kg and 24.43 vs. 22.28 kg, respectively) compared to G2 cows. However, when expressed as proportion of BW and EBW only the reticulum-rumen weight differed between G2 and G3 cows. The greater contribution of C in the genotype resulted in increased volume of blood and development of lungs and all vital organs together when expressed as proportions of EBW.