| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
US Department of Agriculture2,3,, Clay Center, NE 68933
Abstract
The effects of photoperiod (8 hr light: 16 hr dark [8L:16D] or 16L:8D) on performance of growing-finishing lambs were evaluated in an experiment with 24 rams and 24 wethers. All lambs were caged in groups of two in a controlled environment and fed a pelleted diet ad libitum for the duration of the study (10 to 22 weeks of age). Performance and carcass data showed that both photoperiod and sex of lamb affected growth rate (P>.01) and feed efficiency (P>.05) but that only sex of lamb affected carcass quality (P>.05) and yield (P>.10). A sex by photoperiod interaction was not observed for any of the traits measured. Average daily gain (grams/per day) and feed efficiency (feed/gain) for lambs in the four treatment groups tested were: rams (16L:8D), 410 and 4.3; rams (8L:16D), 340 and 4.5; wethers (16L:8D), 345 and 4.6, and wethers (8L:16D), 300 and 4.8, respectively. Carcass weight, like slaughter weight, was affected by photoperiod (P>.01) and sex of lamb (P>.05); both rams and wethers exposed to long photoperiods had the heaviest carcasses. Ram carcasses were leaner, had better yield grades and were heavier than wether carcasses, yet both ram and wether carcasses graded Choice. Testosterone concentrations in serum were undetectable (>.2 ng/ml) at 22 weeks of age in wethers but were elevated (P>.01) in ram lambs exposed to short (3.4 ±1.4 ng/ml) or long (.8 ± .2 ng/ml) photoperiods. Prolactin concentrations, on the other hand, were not influenced by sex of lamb but were influenced (P>.01) by photoperiod; i.e., prolactin concentrations were high in rams (190 ± 34 ng/ml) and wethers (178 ± 28 ng/ml) exposed to long photoperiods and low in rams (43 ± 9 ng/ml) and wethers (27 ±11 ng/ml) exposed to short photoperiods. These results suggest that testosterone and prolactin may independently affect growth and performance of growing-finishing lambs.
1 The authors acknowledge Mr. Bruce Larsen, Ms. Kathy Sorensen and Ms. Donna Taubenheim for technical assistance during the study; Mr. Wayne Hinerman for helping with the statistical analyses, and cooperation of the Nebraska Agr. Exp. Sta., Univ. of Nebraska, Lincoln.
2 Roman L. Hruska US Meat Animal Research Center, AR, SEA.
3 Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable.
This article has been cited by other articles:
|
|
 |
|
  H. Tucker and R. Ringer Controlled photoperiodic environments for food animals Science, June 25, 1982; 216(4553): 1381 - 1386. [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
