| Abstrakt: |
The objective of this study was to evaluate short-term intake rate (STIR) to predict DM voluntary intake (DMVI) and digestibility (DMD) in rams when offered different grass species usually grazed in semiarid Argentina. The evaluated forages were 3 warm-season grasses—fingergrass (F; Digitaria eriantha erianthacv. Irene), kleingrass (K; Panicum coloratumcv. Verde), and switchgrass (S; Panicum virgatumcv. Alamo)—at vegetative (ve) and deferred (d) stages plus 4 small grains—wheat (W; Triticum aestivum) oats (O; Avena sativa), rye (R; Secale cereale), and triticale (T)—and alfalfa hay (AH; control forage for STIR). In separate experiments, 6 Pampinta rams (56 kg mean BW) were individually fed indoors ad libitum each forage in 2 daily meals (1000 and 1600 h) for 7 d of adaptation plus 7 d of DMVI observations and total fecal collection in bags. Simultaneously, a different group of 6 rams of similar BW were used to measure STIR. This group was fed once daily at maintenance level with AH. After 4 h of fasting, the animals were allowed active consumption of each forage for a 4-min period, controlled by an independent observer standing by each ram. Both DMVI and STIR were determined by subtracting refused from offered DM. Dry matter digestibility was calculated from DMVI and feces output, and digestible DMI (DDMI) was computed as well. The range of variable means and SE across grass species were 21.2 ± 2.3 (Sd) to 127.7 ± 7.2 (O), 34.3 ± 5.8 (Sd) to 69.1 ± 2.4 (AH), and 7.7 ± 1.5 (Sd) to 63.5 ± 3.3 (AH) for DMVI (g/kg W0.75per day), DMD (%), and DDMI (g/kg W0.75per day), respectively. The association between STIR and the variables DMVI, DMD, and DDMI (n= 6 for each forage) was studied by regression against the mean STIR value. Linear regression equations describing these relationships are shown in the table. There is strong positive association between STIR and DMVI; however, when a quality factor, such as DMD alone or linked to DMVI, is included, the STIR prediction potential seems to become weaker. Other factors such as palatability and leaf:stem ratio may have an influence not determined by this study.Table 1479. |
