04777naa a2200313 a 450000100080000000500110000800800410001902200130006002400390007310000160011224502970012826000090042550005710043452031120100565300160411765300200413365300310415365300190418465300210420365300320422465300150425665300150427165300120428670000200429870000170431870000160433570000170435177300950436810592272020-06-04       2018    bl uuuu     u00u1 u    #d  a030488027 a10.4206/agrosur.2018.v46n1-042DOI1 aCAZZULI, F.  aSelf-feeding improved animal performance of calves grazing native grasslands during winter on extensive livestock production systems // El auto-suministro mejoró el desempeño de terneros pastoreando campo natural diferido en invierno en sistemas ganaderos extensivos.h[electronic resource]  c2018  aArticle history: Received 30.05.2018; Accepted 29.08.2018. ACKNOWLEDGEMENTS: These experiments were financially supported by the  National  Institute  of  Agricultural  Research  (INIA  Uruguay). The authors would like to thank all field staff who worked on both experimental sites, as well as the thesis  committee  for  all  their  valuable  inputs  to  this  paper. We would also like to acknowledge the inputs made by Ignacio de Barbieri, Martín Jaurena, Zully Ra-mos and Daniela Correa. Corresponding author: Fiorella CazzuliE-mail address:fcazzuli@inia.org.uy  aSupplementing calves on deferred native grasslands during their first winter, helps overcoming the nutritive deficits which occur during this season. However, the demand of both qualification and availability of labour may restrain its adoption. The objective of this work was to evaluate calves? average daily live weight gain (ADG) and supplemental feed efficiency (SFE) as a response to self-feeding methods. Two experiments (Exp) were carried out: i) Exp A, on sandy soils with Braford calves and, ii) Exp B on basaltic soils with Hereford calves. In each experiment 40 castrated male calves were used and randomly allotted to one of two replicates of these treatments: non-supplemented control (C); everyday restricted supplementation (E); restricted self-fed supplementation delivered two times a week (RSF); ad libitum self-fed (ASF). Exp A registered lowest ADG for C (0.155 kg an-1 day-1), similar ADG between E and RSF (0.623 kg an-1 day-1 on average) and highest for ASF (1.135 kg an-1 day-1) (p <0.05). For Exp B, ADG was affected being C &#8804; E &#8804; RSF < ASF (0.158, 0.390, 0.588 and 1.319 kg an-1 day-1, respectively). SFE values were not different (p >0.05) between treatments for Exp A, even though ASF presented a 50% higher SFE (9.4) than RSF (6.2) and E (6.1). SFE was affected (p <0.05), being ASF (7.7) < E = RSF (3.9 on average). It is possible to overcome winter live weight losses through the combination of deferred native grasslands and restricted self-feeding // La suplementación de terneros en su primer invierno pastoreando campo natural diferido compensa los déficits nutricionales registrados durante esta estación. No obstante, las necesidades de calificación y disponibilidad de mano de obra puede restringir su adopción. El objetivo de este trabajo fue evaluar la ganancia media diaria (GMD) y la eficiencia de uso del suplemento (EUS) como respuesta a métodos de auto-suministro. Se realizaron dos experimentos: i) Exp A, sobre suelos arenosos utilizando terneros Braford y, ii) Exp B, sobre suelos de basalto utilizando terneros Hereford. En cada experimento se utilizaron 40 machos castrados en su primer invierno y fueron asignados al azar a una de las dos repeticiones de estos tratamientos: testigo no suplementado (T); suplementación diaria restringida (DR); suplementados restringidamente dos veces por semana mediante auto-suministro (ASR); suplementados ad libitum mediante auto-suministro (ASA). En el Exp A se registró la menor GMD para T (0,155 kg an-1 día-1), similares valores entre DR y ASR (promedio 0,623 kg an-1 día-1) y la más alta para ASA (1,135 kg an-1 día-1) (p <0,05). Para el Exp B, la GMD fue afectada, siendo T &#8804; DR &#8804; ASR < ASA (0,158; 0,390; 0,588 and 1,319 kg an-1 día-1, respectivamente). EUS no fue afectada en Exp A (p >0,05), si bien ASA presentó valores 50% superiores que ASR (6,2) y que T (6,1). En el Exp B, EUS fue afectada (p <0,05), siendo ASR (7,7) < DR = ASR (3,9 promedio). Es posible superar las pérdidas peso mediante una combinación de diferimiento de forraje y auto-suministro restringido.  aBEEF CATTLE  aGANADO DE CARNE  aINFREQUENT SUPPLEMENTATION  aNATIVE PASTURE  aPASTURAS NATIVAS  aSUPLEMENTACIÓN INFRECUENTE  aSUPLEMENTO  aSUPPLEMENT  aURUGUAY1 aLAGOMARSINO, X.1 aBOGGIANO, P.1 aSAADOUN, A.1 aMONTOSSI, F.  tAgro Sur, 2018gv. 46, no. 1, p. 29-39. DOI: https://doi.org/10.4206/agrosur.2018.v46n1-04