The effects of feeding levels on characteristics of fibers of Raeini Cashmere goats

S A Rafat and D Shodja D

Animal Science Department, Faculty of Agriculture, University of Tabriz,
P.C.51664, Tabriz, Iran
abbasrafat@hotmail.com

Abstract

Twenty-four female Raeini cashmere goats were studied for 8 months to assess the effects of feeding level and age (6 month and 18 months) on fleece growth. The trial was conducted at the Khalat-Pushan Research Station, University of Tabriz. The goats were allocated to 4 levels of feeding: maintenance (M); 0.7M, 1.4M and 1.8M. Patches of fleece from defined areas were repeatedly shorn at 4 week intervals from the right mid side of each goat. For follicle study, skin biopsy was taken monthly from the left mid side.

There was no significant effect of feeding level or age on weight of cashmere and hair per area, secondary follicle activity, cashmere length and yield. Fleece and live weight for young goats were significantly less than that of old goats. Mean cashmere diameters of patch shorn in September from goats fed M, 1.4M and 1.8M were significantly greater than that of goats fed 0.7M. Feeding more than maintenance requirements resulted in no increase in cashmere production. Average fiber diameter of cashmere in June was higher than in May. Growth rates were optimal in June and July (1.64 and 1.48 g/120 cm² /28 days, respectively). Secondary: primary ratio of follicles in all goats was 12.6.

Results showed that raising Raeini cashmere goats in East Azerbaijan climate did not change diameter and length of cashmere in comparison to Raeini cashmere goats, which were raised in Kerman province. Further work is needed to investigate the fleece production of cashmere goats in large scale and under extensive production system in East Azerbaijan.

Keywords: Cashmere, diameter, follicle, goat, maintenance, nutrition.

Introduction

Traditionally goats are indeed important in Iran especially for milk and fibers. This country has nearly 5,000,000 cashmere producing goats, which produce approximately 1500 metric tonnes of raw cashmere. So research on environmental factors which have effects on cashmere production, is very vital to the economy of the country. Raeini breed is the most productive Cashmere goat in Iran (Rafat 1998). However, there are no detailed descriptions of the effects of nutrition on cashmere characteristics in Raeini goats. There is some debate on the effects of nutrition on cashmere growth. In some studies cashmere growth does not respond to increased feed intake above maintenance. While some reviewers have concluded that nutrition does influence cashmere growth (McGregor 1998). The objective of this study was to describe the effects of feeding level on the cashmere growth of Raeini female goats at two different ages.

Materials and methods

Goats used in the study were the progeny of randomly mated population of Raeini cashmere goats, kept under intensively managed conditions since 1998.Twelve 6-month old (young) and twelve 18-month old (old) female Raeini goats were selected for use in the experiment. All goats had been run at pasture until the start of the experiment. The trial was conducted at the Khalat-Pushan Research Station, University of Tabriz. Initial live weights (± standard errors) for the young and old goats were 16.4 ± 1.22 and 29.5 ± 4.33 kg respectively. All goats were held in metabolism cages and treated with Albendazule (150 mg/20 kg body weight) initially and at 4-weekly intervals throughout the experiment. The animals were fed on commercial lucerne for 6 months (+ 2 months pre-experiment period). The goats were not permitted to mate, to avoid influence of pregnancy and lactation on cashmere growth. Maintenance requirements and near ad libitum levels of feed intake were estimated from the studies of Kloren et al (1993).Three 6-month-old and three 18-month-old female goats were randomly assigned to maintenance (M), 0.7 M, 1.4 M and 1.8 M feeding groups in a 2 (age) x 4 (level) factorial experiment. This experiment lasted 6 months (plus 2 pre-experiment period) from February to September of 2000.

Feed offered was adjusted every 2 weeks to correct for changes in live weight. Patches of fleece from defined areas (120 cm²) were repeatedly shorn at 4 weekly intervals from the right mid-side of each goat. Fleece harvested in this manner was washed in detergent, rinsed in deionized water, and oven-dried at 60^ºC for 48 h prior to weighing. Several snippets were randomly sampled from the patch fleece and dispersed in liquid paraffin on a microscope slide. Two slides prepared in this manner from each fleece were used to estimate diameters of cashmere (200 fibers) by projection microscopy. Also cashmere length, yield and fleece weight were determined. For follicle study, skin biopsy was taken monthly from left mid-side. Samples were fixed in phosphate buffered formalin for 48 hr or longer, then processed through graded concentrations of ethanol and xylol to paraffin wax. Transverse 7-8 micrometer sections of follicles were cut on a rotary microtome. Sacpic stained transverse sections were used for estimating follicle activity according to Nixon (1993).

Statistical method

Differences in measurements between treatments within sampling periods were determined using analysis of variance for a factorial design. Differences between sampling periods for cashmere traits were determined using paired t-test. Covariate analysis was not used, as there were no significant differences in measurements made on goats prior to the experiment.

Results and Discussion

The goats fed M, 1.4M and 1.8M had higher diameter of cashmere than those fed 0.7M (Table 1) (P<0.05). There was no difference (P>0.05) between old and young goats in diameter of cashmere during the experiment period. Diameter of cashmere during different months was variable.

Table 1. Effects of feeding level on cashmere diameter during experiment period. (Means ± standard deviation).
Feeding level	April	May	June	July	August	September
0.7 M#	15.67^a± 0.90	16.23^a± 0.93	17.97^a± 0.59	17.42^a± 0.85	16.50^a± 1.15	16.36^a± 1.70
M	16.30^b± 1.47	17.00^b± 0.73	17.62^a± 0.83	18.01^b± 0.70	17.41^b± 1.26	17.90^b± 1.10
1.4 M	16.01^b± 1.41	16.60^b± 1.22	18.00^b± 0.76	18.09^b± 0.83	17.78^b± 0.91	17.86^b± 0.86
1.8M	17.20^b± 0.77	17.52^b± 0.52	18.05^b± 0.74	18.33^b± 0.81	18.36^b± 0.93	18.00^b± 1.35
# M=Maintenance. ab Means within a column without superscript in common differ at P< 0.05

There was no significant effect of feeding level or age on cashmere and hair weight throughout the experiment (Table 2). Growth rates of fiber were optimal in June and July (1.64 and 1.48 g/cm²/28 days respectively), but the difference between months was not significant. There were no significant effect of feeding level or age on secondary follicle activity, cashmere length and yield. Cashmere length and the ratio of secondary: primary follicles in all goats were 6.53 cm and 12.6, respectively. Fleece weight for young goats was less (P<0.01) than that of old goats (432 versus 545 g).

Table 2 Effects of feeding level and age on the monthly growth of cashmere and hair (Means ± standard deviation, g /120cm²/28 days)
Feeding level	April	May	June	July	August	September
0.7 M^#	0.65± 0.15	1.18± 0.38	1.77± 0.36	1.35± 0.26	1.07± 0.26	0.75± 0.27
M	0.80 ± 0.34	0.92± 0.45	1.48± 0.35	1.40± 0.21	1.45± 0.26	1.23± 0.20
1.4M	0.70± 0.21	1.45± 0.11	1.75±0.09	1.72± 0.20	1.63± 0.20	1.27± 0.24
1.8M	0.82 ± 0.30	1.32± 0.64	1.57 ± 0.29	1.45± 0.20	1.55± 0.25	1.10± 0.25
Age
Young	0.85 ± 0.36	1.27± 0.50	1.68± 0.39	1.42± 0.25	1.39± 0.37	1.08± 0.30
Old	0.63± 0.34	1.17 ± 0.62	1.60± 0.43	1.54± 0.27	1.46± 0.32	1.09± 0.34
# M=Maintenance.^A Means with no superscript or with a common superscript do not differ (P > 0.05) from each other

Ash and Norton (1987), McGregor (1988) and Kloren et al (1993) have also shown that changing levels of nutrition above maintenance do not increase cashmere growth. McGregor (1988) reported that feeding below maintenance resulted in a significant reduction in cashmere growth. Norton et al (1990) and Russell (1995) showed a significant difference in cashmere production between goats fed below that for maintenance of live weight and those goats fed above maintenance. In addition, significant differences in cashmere fiber diameter were reported between goats fed to maintain live weight and those fed to gain live weight. Cashmere diameter of Raeini old goats was coarser than young goats, but the difference was not significant. This result being not similar to those of Restal and Pattie (1989) and Kloren et al (1993). The present experiment shows that cashmere diameter remains relatively constant from April to May, after which diameter increases by around 1 micrometer. Secondary follicle activity remained relatively low on all treatments until May. By June secondary follicle activity was increasing on all treatments. Further clarification of nutritional effects on cashmere growth may come from studies of fiber growth initiation and cessation intervals, the growth period and follicle shedding patterns. Both McDonald et al (1987) and Kloren et al (1993) noted changes in diameter and length during the growing cycle, raising the possibility that nutrition could act by altering the shedding patterns.

Conclusions

The results of the present experiment indicate that there was no effect of increasing the feeding level from maintenance to ad libitum on cashmere diameter, on the activity of secondary follicles or monthly fiber growth. Feeding more than maintenance requirements resulted in no increase in cashmere production. Raising cashmere goats in large scale and under extensive production system must be studied in Tabriz climate in future studies.

Acknowledgments

This experiment was contacted under financial support of Research and Technology Office of University of Tabriz.

References

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