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Forage impact on subsequent finishing performance of wethers

A. L. Goetsch1 and G. E. Aiken2

1E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK, and 2Dale Bumpers Small Farms Research Center, USDA, ARS, Booneville, AR

High-forage diets are often consumed ad libitum (ALI) in a growing phase, followed by ALI of concentrate-based diets (CBD) during finishing. Splanchnic tissue energy use relative to absorbed energy is greater for ALI of forage-based diets than for limited intake or ALI of CBD (Goetsch, 1998). Sainz et al. (1995) observed lower live weight gain and efficiency of feed utilization during finishing for beef steers that previously consumed forage ad libitum compared with steers given restricted access to CBD. The proportion of the finishing period during which energy use was influenced by greater liver and stomach protein mass observed at the end of the growing phase (Sainz and Bentley, 1997) is unknown. If appreciable, a short period of limit-feeding CBD after growing phase ALI of forage might avert or lessen high energy use by splanchnic tissues during finishing. Hence, objectives of this experiment were to determine effects of ALI of forage (long-stemmed alfalfa hay) or restricted intake of CBD (80% concentrate) on subsequent finishing performance with ALI of CBD. Forty-eight wethers (9 months of age; 28.6 ± .40 kg initial live weight; 16 St. Croix and 32 St. Croix × Romanov) were used in the 14-wk experiment. Treatments were ALI of CBD for 14 wk (AC); ALI of forage for 8 wk followed by 6 wk ALI of CBD (F-AC); restricted intake of CBD for 8 wk followed by 6 wk ALI of CBD (LC-AC); and 6 wk ALI of forage followed by 2 wk restricted intake of CBD then 6 wk ALI of CBD (F-LC-AC). Transitions from forage to CBD occurred in 1 wk or less. At the beginning of wk 9 and end of wk 14, shrunk body weight and body composition (via urea dilution) were determined. Factors responsible for improved performance in wk 9-14 for F-LC-AC compared with F-AC are unknown and deserved of study. Nonetheless, a more rapid decrease with time in energy use by splanchnic tissues relative to absorbed energy for F-LC-AC after forage and(or) limited CBD consumption than for F-AC after ALI intake of forage is possible, which encompasses potential influences of changes in the quantity of nutrients absorbed and physical characteristics of digesta. In conclusion, growing phase restricted intake of CBD may affect subsequent performance with ALI of CBD differently than ALI of forage. A period of restricted intake of CBD following growing phase ALI of forage could offer potential to improve later performance with ALI of CBD.

Performance by wethers during a 14-wk growing-finishing period
Treatments

Item

Week AC LC-AC F-AC F-LC-AC SE
DMI (g/d) 1-6 1465c 791a 1127b 1131b 29.2
7-8 1707c 893a 1216b 1139b 41.0
9-14 1571 1511 1443 1583 62.5
1-14 1545c 1114a 1275ab 1326b 42.4

LWG (g/d)

1-6 277b 75a 53a 59a 18.0
7-8 239c 124b 154b 27a 21.3
9-14 191a 274b 178a 289b 14.9
1-14 235c 167b 121a 153ab 11.7

LWG:DMI (g/kg)

1-6 189b 94a 47a 53a 12.5
7-8 139b 139b 126b 24a 14.6
9-14 122a 182b 123a 182b 6.8
1-14 152c 150c 95a 115b 4.9
Accretion
Protein (g/d) 9-14 16.5 19.0 16.7 17.6 2.00
Fat (g/d) 9-14 84a 151bc 115ab 168c 10.1
Energy
Kcal/d 9-14 884a 1522bc 1178ab 1674c 92.0
Kcal:Mcal MEI

9-14 194a 345b 286b 363b 21.7

DMI = dry matter intake; LWG = live weight gain; MEI = metabolizable energy intake.
a,b,cWithin a row, means lacking a common superscript letter differ (P < 0.05).
GOETSCH, A.L., 1998. Splanchnic tissue energy use in ruminants that consume forage-based diets ad libitum. J. Anim. Sci. 76, 2737.
SAINZ, R.D., DE LA TORRE, F. & MORRIS, J.G., 1995. Compensatory growth and carcass quality in growth-restricted and refed beef steers. J. Anim. Sci. 73, 2971.
SAINZ, R.D. & BENTLEY, B.E., 1997. Visceral organ mass and cellularity in growth-restricted and refed beef steers. J. Anim. Sci. 75, 1229.


 

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