Evaluación del grano de lupino (Lupinus Angustifolius) como suplemento en la recría de terneros ofrecido en comederos de autoconsumo: efecto sobre el pH y cinética de fermentación ruminal de terneros pastoreando verdeos de invierno

The experiment was conducted at the Intensive Meat Production Unit (UPIC) of the Dr. Mario A. Cassinoni Experimental Station (EEMAC), belonging to the University of the Republic (UDELAR), Faculty of Agronomy, located in the department of Paysandú, Uruguay. The objective was to evaluate the effect of lupin grain supplementation and the method of supply, daily at 1% of body weight (BW) and ad libitum self-feeding, on the degradation kinetics of lupin and forage, as well as on ruminal fermentation and animal behavior. Three steers, born in the spring of 2022 and aged between 1 and 2 years at the time of the experiment, with an average initial body weight of 310 ± 3 kg, fitted with ruminal fistulas, were used. The animals were randomly assigned to treatments using a three-period Latin square design, so that each steer received all experimental treatments. Each period lasted two weeks: one week for adaptation and one week for evaluation. The forage consisted of ryegrass (cultivar Bill Max, Gentos®), with an average availability of 8,137.6 ± 3,033.2 kg of dry matter (DM)/ha and an average height of 44 ± 10.7 cm during the experimental period. Grazing was carried out in weekly strips. The treatments were: T1 (control), ryegrass grazing with a forage allowance of 2.5% of BW without supplementation; T2, daily supplementation with lupin grain at 1% of BW; and T3, ad libitum supplementation. In all treatments, DM intake, behavior, in situ degradability, in vivo DM digestibility, ruminal pH, and ammonium (NH₄⁺) concentration were evaluated. Significant differences were observed in total dry matter intake (DMI), with higher values in the supplemented treatments. Regarding degradability, differences were detected in parameters “a” and “b” of the Ørskov and McDonald (1979) model, where lupin and corn showed significantly higher values than forage. Likewise, NH₄⁺ concentration was higher in the supplemented treatments. No statistical differences were recorded in ruminal pH or in dry matter digestibility (DMD) and organic matter digestibility (OMD).