Sustitución parcial del grano de maíz por grano de arroz con cáscara en raciones de engorde de vacunos: Efecto del procesamiento y nivel de humedad del grano sobre la ganancia de peso y eficiencia de conversión

The experiment was conducted at the Intensive Meat Production Unit (UPIC) of the “Dr. Mario A. Cassinoni” Experimental Station (EEMAC) in Paysandú, Uruguay, from June 24 to October 2. The objective was to evaluate the effect of partially replacing ground corn grain in the diet with rice grain with hulls (GACC) of different processing levels and moisture content on the performance of feedlot-finished steers. Growth curves were described, and live weight gain and feed conversion efficiency were quantified for each treatment. The study involved 48 Hereford steers from the EEMAC experimental herd, born in spring 2022, with an initial average weight of 363.7 ± 17.8 kg. The animals were assigned to four blocks according to live weight and then randomly allocated to four treatments. Each treatment consisted of a total mixed ration (TMR), resulting in 16 groups of three animals each. Each group was housed in a separate pen, and each treatment was made up of four pens, each considered an experimental unit. All four TMRs had a forage-to-concentrate ratio of 20/80, differing in the type of grain (45% ground corn at 14% moisture or 45% ground GACC at 14% moisture), processing level (45% cracked GACC at 14% moisture), and moisture content (45% cracked GACC with 77% dry matter). The replacement of corn grain with rice grain with hulls in the steers' diet affected feed conversion efficiency when comparing processing level and moisture content. The feed conversion efficiency (FCE) for the TMR with ground GACC was 6.48 kg DM/kg BW, and for cracked GACC it was 6.94 kg DM/kg BW—representing a 7% improvement with smaller particle size. For the TMR with wet cracked GACC, the result was 6.36 kg DM/kg BW, showing an 8% improvement in feed conversion efficiency with higher grain moisture content. There were no significant changes in average daily gain (ADG) or dry matter intake (DMI), with averages recorded at 1.98 ± 0.09 kg/day for ADG and 3.14 ± 0.07 %BW for DMI. This indicates that, in feedlot diets, GACC could have potential as an energy source.