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The objective of this study was to assess the economics of the post-weaning phase and performance of Nellore calves born to dams that received protein concentrate supplementation during the final trimester of pregnancy. This research was organized into two phases: Phase I entailed a 90-day supplementation period for the dams in the last third of their pregnancy, and Phase II spanned from the birth of the calves to their weaning at 240 days. Twenty multiparous Nellore cows, subjected to fixed-time artificial insemination (FTAI), were divided into two groups: unsupplemented (US) and supplemented (SP), each comprising 10 animals. Statistical analysis was performed using an analysis of variance and the F-test with a significance level set at 0.05, within a completely randomized design. Among the parameters examined, only the total feed cost (US = BRL41.09 vs. SP = BRL112.22, P = 0.0001), effective operating cost (US = BRL872.51 vs. SP = BRL943.64, P = 0.0001), total operating cost (US = BRL925.51 vs. SP = BRL951.64, P = 0.0001), and total cost (US = BRL925.51 vs. SP = BRL996.64, P = 0.0001) were significantly affected by protein concentrate supplementation during the last third of pregnancy. Therefore, it can be concluded that while protein concentrate supplementation in the final stages of pregnancy does not influence the performance or morphological traits of calves, it does lead to increased feed and labor expenses. However, these increases do not negatively impact economic viability rates.

ABSTRACT: In beef cattle breeding programs, various selection criteria have been proposed and employed with the aim of improving traits related to carcass composition and the quality of the final product, meat. However, the importance of genotype by environment interaction (G×E) for such traits is still not well understood. Our objectives were: 1) to investigate the importance of G×E on ultrasound carcass traits, growth and visual scores and 2) to estimate the genetic correlation of ultrasound carcass traits with growth and visual scores taking into account the G×E in Hereford and Braford cattle. A multiple-trait reaction norm model was fitted to the field records of 37,948 animals. With the exception of postweaning average daily weight gain (ADG), the G×E can lead to important changes in the ranking of estimated breeding values of sires across environments for all traits. Thus, models that consider heterogeneity of genetic variances along an environmental gradient may be considered more appropriate for genetic evaluations of animals reared under conditions similar to the present study. Based on estimates of genetic correlation, the quality of visual scores or ADG as indicators of carcass quality assessed by ultrasonography is dependent on the production environment.