Dry matter intake observed and predicted by the nutritional systems NRC and BR-Corte for feedlot nelore heifers fed with human feed products

Abstract

We aimed to evaluate the effects of using a concentrated ration containing industrialised human food on the productive parameters of Nellore heifers in confinement, in addition to comparing the dry matter intake (DMI) observed with that predicted by the nutritional systems BR-Corte and NRC, in order to determine which system makes the most accurate predictions for heifers of the breed Nelore in feedlots. Twenty-four Nelore heifers, with an average age of 24 months and average body weight (BW) of 350 kg, were used over the 70 days of the experiment. They were randomly assigned to two treatments and housed in partially covered stalls equipped with an automatic Growsafe® Systems feeding system. Animals in the control group (CONT) received a concentrated ration containing ground corn, soybean meal, urea, and mineral nucleus. In the residual treatment (RES) group, heifers received concentrated feed containing products from the human diet. The difference between the treatments was the concentrated ration; in the control treatment, the energy source used was maize, whereas in the residue treatment, the energy sources were corn chips, coconut candies, and ground coffee. Corn silage was included as forage for both treatments. The forage:concentrate (F:C) ratio was 84:16. The predicted intake was estimated according to the nutritional systems NRC (2000, 2016) and BR-Corte (VALADARES FILHO et al., 2010, 2016). The average DMI observed of the heifers was 7.46 kg day-1. Heifers fed with human feed residue had a higher dry matter intake (DMI) and higher ether extract intake (EEI) than animals fed with the control feed. In addition, heifers that received human feed products showed a lower average daily weight gain (DWG) of 1.08 kg day-1 than animals fed the control treatment with an average DWG of 1.24 kg day-1. The predicted dry matter intake by NRC 2000 was an overestimate by 9.78 % and by BR-Corte 2010 was an overestimate by 5.5 %. The NRC 2016 and BR-Corte 2016 underestimated the intake of heifers by 18.9 % and 7.1 %, respectively. It was concluded that growing Nelore heifers fed with human feed products, with a F:C ratio of 84:16, present a higher DMI and lower growth performance and feed efficiency than heifers fed the control diet. The DMI predicting models for Nellore heifers proposed by BR-Corte are more adequate than the NRC models.