|
|
|
||
|
| |
||
|
|||
|
|
 |
Fiber Production
Effects of dietary protein level on performance of Angora and cashmere-producing Spanish goats Effects of dietary crude protein level on fiber production of Angora and cashmere-producing Spanish goats were studied in 16 yearling doelings (eight Spanish, eight Angora) for 8 weeks. Goats were housed in individual stalls and maintained at constant temperature (21C) with 9 h light and 15 h darkness each day. Goats were initially sheared, blocked by body weight (BW) and assigned to one of two dietary treatments (8 or 16% crude protein (CP)) in a 2 × 2 factorial design. Diets were isocaloric (2.9 Mcal kg -1 digestible energy (DE)) and were fed ad libitum. Dry matter intake (DMI) was similar for Angora and cashmere-producing Spanish goats. Daily DMI (612 vs 892 g day-1) and BW gain (38 vs 127 g day-1) were greater (P < 0.05) for cashmere-producing Spanish goats fed the 16% CP diet compared to 8% CP. For Angora goats, DMI (734 vs 832 g day-1) and BW gain (55 vs 116 g day-1) were also increased (P < 0.05) at the 16% CP level. Nitrogen retention (2.2 vs 8.7 g day-1) increased (P < 0.01) with dietary CP for both types of goats. Creatinine and packed cell volume were lower (P < 0.10, P < 0.01) for Angora goats. Both plasma urea nitrogen (PUN) and PUN/creatinine were increased (P < 0.001, P < 0.001) by high protein, whereas triiodothyronine and thyroxine were reduced (P < 0.01, P < 0.05); the clean mohair fleece weight of Angora goats was increased 31% (P < 0.05) with the high CP diet. Total fleece weight, down-yield, cashmere fiber length, and diameter were not affected (P > 0.05) by diet CP level for cashmere-producing Spanish goats. Increasing the diet CP level increased mohair production, diameter, and staple length, but had little effect on cashmere fiber production. Increasing dietary protein also increased DMI, BW gain, and feed efficiency in both types of goats. Top of PageThe nutritional control of the growth and properties of mohair and wool fibers: a comparative review The effect of nutrient status on the growth and properties of wool and mohair fibers is reviewed: the aim is to compare effects on sheep and Angora goats and emphasize differences between the species. Wool growth is markedly influenced by nutrition; the requirement for energy-yielding nutrients is low and the major nutrients limiting wool growth are essential amino acids, sulfur-containing amino acids being especially important. An adequate supply of Cu, Zn, folic acid, and pyridoxine is required to maintain wool growth. Both length growth (L) and diameter (D) of wool fibers respond to changes in nutrient supply such that the ratio of L:D remains approximately constant. Mohair production is influenced by nutrient supply. However, the importance of specific nutrients has not been established, apart from one study showing that mohair growth responded to parenteral supplementation with methionine. In contrast to sheep, some studies indicate that length growth of mohair fibers may not be very responsive to changes in nutrient status. The responsiveness of mohair growth (both length and diameter) to nutrient supply at different times of the year has not been reported. The energy requirement for fiber growth may be greater in goats than in sheep, but more studies are needed. Top of PageDietary protein level and ruminal degradability for mohair production in Angora goats Twenty-eight Angora goat doelings (average BW 22.1 kg) were used in a 150-d study to examine the effects of dietary CP level and degradability on mohair fiber production. A 2 × 2 factorial arrangement was instituted using conventional, solvent-extracted soybean meal (high degradability) or expelled, heat-treated soybean meal (low degradability) incorporated into low- (12%) or high- (19%) CP diets. Grease and clean mohair weights were greater (P < 0.05) in goats fed the diets containing 19% CP. Mohair fiber diameter was not affected (P > 0.10) by dietary CP level. Clean mohair weight tended (P < 0.08) to be higher in the goats fed diets containing expelled, heat-treated soybean meal. Body weight gains were not affected (P > 0.10) by CP level or degradability, whereas DMI increased (P < 0.01) with increasing CP level. Ruminal fluid pH and total VFA concentrations were not affected (P > 0.10) by diet. Ruminal ammonia N concentration increased (P < 0.05) as CP level in the diet increased, and postprandial changes in concentrations were less noticeable in the group fed expelled, heat-treated soybean meal. Plasma urea N (P < 0.001) and total protein (P < 0.01) concentration increased as dietary CP level increased. Plasma glucose was elevated (P < 0.001) 2 h after feeding in the goats fed conventional, solvent-extracted soybean meal, whereas glucagon concentrations were greater at 0 and 4 h in the group fed expelled, heat-treated soybean meal. This study demonstrates the inverse relationship between the quality and quantity of mohair fiber produced, and how fiber characteristics can be affected by dietary CP level and degradability. Top of PageForty pregnant Angora does were wintered on ad libitum bermudagrass hay with 20 does receiving one pound of a 16% concentrate supplement and the other 20 does allowed to graze a pasture mixture of wheat and ryegrass for two hours per day. The limit-grazed does consumed half the quantity of the hay as the supplemented does and consumed less dormant forage in their pastures. The supplemented does lost 6% of their body weight (BW) during the study, whereas the limit-grazed does maintained their weight. The limit-grazed does produced more clean fleece with no effect on staple length or fiber diameter. Limit-grazing of cool-season pastures improved animal performance while reducing hay and supplement requirements. Top of PageSulfate supplementation of Angora goats: metabolic and mohair responses Eight castrated male Angora goats were used in a repeated, simultaneous 4 × 4 Latin square designed experiment to evaluate metabolic and mohair responses of Angora goats to sulfate and mohair responses of Angora goats to sulfate supplementation. Goats had ad libitum access to isonitrogenous diets containing a 0.16 (basal), 0.23, 0.29, or 0.34% S (DM basis), which yielded N:S ratios of 12.7, 8.3, 6.8, or 5.5:1. Feed intakes were not affected (P > 0.20) by dietary S level. Quadratic increases (P < 0.05) to S supplementation were observed in grease and clean mohair production, grease and clean staple strength, and staple length. Mohair diameter, med fiber, kemp fiber, S, and cysteine contents were not affected (P > 0.05) by supplemental S. Averaged across the prefeeding, 2, 4, and 6 h postprandial sampling times, ruminal pH, ammonia N, total S, organic S, protein S, and plasma urea N and organic S concentrations were quadratically increased (P < 0.05) by supplemental S. Ruminal sulfate S, total sulfide S, and plasma sulfate S were linearly increased (P < 0.05) by supplemental S. Retention of N and mohair S yield exhibited quadratic increases (P < 0.05), but S retention exhibited a linear increase (P < 0.001) with increased S intake. Calculated by regression, the optimum dietary S concentration for maximum clean mohair production was 0.267% of dietary DM for a N:S ratio of 7.2:1, suggesting that the National Research Council N:S ratio of 10:1 is inadequate for Angora goats. The optimum level of digestible S was calculated to be 0.18% of the diet DM. Top of PageA review of factors leading to high fleece production in Angora compared to down-producing goats This paper describes the possible factors which lead to high fleece production in Angora (mohair-producing) goats compared to down-producing goats. In comparison to down-producing goats, Angora goats have a reduced seasonality of fiber growth; a three- to four-fold greater fiber output per unit area of skin during active growth; and a two-fold greater mean follicular fiber output during active growth. This may be associated with an improvement in the follicular efficiency for keratin production. Angora goats, in comparison to down goats, have similar feed intakes (on a metabolic liveweight basis) and efficiencies of feed digestion. Angora goats partition more nutrients to fiber growth and less to muscle than down goats. Angora goats also retain more nitrogen, have lower plasma urea concentrations, recycle urea more effectively and excrete less urea than down goats. High fleece production in Angoras may be associated with a reduced gluconeogenic capability and lower blood glucose concentrations. Top of Page |
Extension Activities | Research Activities | Other Activities Library Activities | Quiz | Search | About Us | Contact Us | Faculty & Staff Research Extension Home | Top of Page Copyright© 2000 Langston University • Agricultural Research and Extension Programs P.O. Box 730 • Langston, OK 73050 • Phone 405.466.3836 |
