H . Galbraith Livestock Production Science 64 2000 81 –93
87 Table 6
Mean values with S.D. for fleece, fibre, wool follicle and cellular characteristics of sheep offered diets containing either 15 low or 51 high g N kg DM see text for details: modified from Hynd, 1989
N in Fleece
Fibre Fibre
Cortex Total no.
No. of No. of
diet growth
diameter length
volume of bulb
mitoses cortex cells
21 23
3 21
21 21
g N kg g day
mm mm day
10 3 mm h
cells h
produced h 15
10.5 25.3
378 7.4
909 26
8.0 S.D.
1.8 2.5
30 1.7
221 4.7
1.4 51
14.0 27.2
475 11.0
1177 35
11.3 S.D.
2.9 3.5
44 3.2
309 7.0
2.8
wool production associated with increases in the periods, whereas responses to cashmere were ob-
germinative volume of the bulb, rates of fibre tained from days 31–58 only. These responses of
elongation and proliferation of cells of the bulb. This increasing yield without affecting diameter indicate
latter response is of particular interest since it implies greater growth due to an enhanced rate of elongation
a direct local effect of nutrition supply on the for the cashmere fibre. Guard hair was not affected
mechanisms responsible for cell division, including by supplementation. The presence of significant
those at the level of the gene and or an indirect interactions indicates the generally greater response
effect involving stimuli perhaps of systemic hormon- of Angora goats to supplementation. However, the
al or more local paracrine origin. It may be con- positive response for cashmere production contrasts
cluded from these results that the effects of improved with the report by Ash and Norton 1987a who
protein nutrients are more complex than those pro- observed no response in cashmere growth to dietary
duced solely as a consequence of improved amino supplements of methionine in 3–4-year-old Aus-
acid supply for protein synthesis in the proliferating tralian Cashmere entire males live weights were not
and differentiating cortical cells which form the hair reported and when differences in total hair growth
fibre. were attributed to an increased production of guard
hair by primary follicles. This latter result for cashmere is consistent with the absence of response
3. Responses to rumen-protected methionine to improved protein supply at supra-maintenance
levels of nutrition already discussed in Section 2.3. A 3.1. Response of Angora and Cashmere goats to
possible explanation made by Ash and Norton rumen-protected methionine supplementation
1987a is that the genetic potential for cashmere production had already been met in the absence of
One disadvantage of meeting the requirement for supplementation by the low-yielding animals used in
one amino acid by means of protein supplementation their study. They also suggest, in the absence of
is the over-provision of other amino acids, the increases in blood cysteine cystine concentrations,
disposal of which places a metabolic burden on the that methionine did not readily promote the pro-
animal. With this in mind, we have studied the duction of cysteine by transulphuration in the liver
response of both Cashmere and Angora 1-year-old and kidney, but this did not appear to inhibit the
goats with initial average live weights of 52.5 and anabolic response of guard hair. This observation
47.5 kg, respectively to supplementation with rumen- may be considered in the context of subsequent
protected intestinally-available
methionine studies see Section 3.3 which suggested the pres-
ˆ Smartamine
E M, Rhone-Poulenc, Paris, France. At ence of transulphuration in the secondary hair follicle
inclusion rates of 2.5 g day, in addition to a basal of the cashmere goats.
diet containing per kg DM 9.9 MJ ME and 107 g While it is apparent that sulphur amino acid
CP, methionine stimulated Table 7 raw fibre yields metabolism is a complex process, the present re-
and fibre diameter of Angora goats in both treatment viewer draws attention to quantitative aspects of fibre
88 H
. Galbraith Livestock Production Science 64 2000 81 –93 Table 7
2
Mid-side fibre yields mg 100 cm day, proportion of cashmere and guard hair and diameter of cashmere and mohair in response to methionine supplementation modified from Souri et al., 1998a
a b
Treatment groups Significance of contrasts
CO CS
AO AS
s.e. D
G I
Days 0–30 Total raw fibre yield
42.0 53.0
96.3 141
8.0 Guard hair yield
29.0 33.0
2.4 Cashmere yield
13.0 19.0
1.7 Proportion
0.31 0.37
0.02 Diameter day 30 mm
19.7 19.2
27.6 32.9
1.9 Days 31–58
Total raw fibre yield 46.0
54.0 87.0
156 7.0
Guard hair 33.0
35.0 2.9
Cashmere 12.0
19.0 1.5
Proportion 0.27
0.35 0.02
Diameter mm day 58 18.9
19.7 28.3
32.6 1.7
a
C, Cashmere; A, Angora; O, no supplementation; S, methionine supplementation.
b
Contrast: D, diet; G, genotype; I, interaction between diet and genotype.
production in that the responses to methionine an g day with | 1.5 g day attributable to cashmere in
amino acid frequently deficient in ruminant diets e.g. which a methionine response was obtained in the
Orskov, 1992 were positively related to the nutrient study of Souri et al. 1998a. The goats in the latter
demands for synthesis of protein deposited in the study were derived from a commercial Scottish
fibre produced. For example, it is clear from the data Cashmere
breeding programme
which included
shown in Table 7 that under similar conditions of selection for yield and although the average diame-
husbandry and
nutrition a
the response
to ters of cashmere fibres exceeded the commercially
methionine was larger and b this was associated desirable value of 18 mm, they were well within the
with a greater total fibre production by Angora goats range for cashmere of 8–24 mm as described by Ash
2
than Cashmere goats e.g. 156 vs. 54 mg 100 cm and Norton 1987a.
day on methionine supplemented diets and that the The effects of rumen-protected methionine supple-
weights of secondary follicle fibre production by mentation on growth and nitrogen retention in addi-
Angora goats was eight to ten times greater. It is also tion to hair fibre characteristics were also studied in
suggested that the response in cashmere production these animals. Results are presented for the first 40
in this study was due at least partially to an in- days of the study Table 8. These showed signifi-
adequate supply of methionine cysteine from the cant positive responses to supplementation for LW
unsupplemented diets to meet the maximum potential gain, food conversion efficiency and nitrogen re-
0.75
for cashmere growth by the genotype studied. Differ- tention both mg kg LW
and g kg N intake per ences in response compared with other reports in the
day. The results suggest that methionine supple- literature may reflect differences in the potential of
mentation acted also to overcome limitations in different genotypes of goats to produce cashmere
growth of non-fleece tissues for both genotypes. e.g. Bishop, 1994 and Restall et al., 1994 and the
Although statistical significance of a genotype 3 diet degree of deficiency of the absorbed amino acid or
interaction was not obtained, there was a marked metabolites in relation to the requirement for maxi-
trend towards a greater response by Angora goats mum fibre growth. For example, the protein accre-
which did attain significance from day 40–68 of the tion in fleece in the study of Ash and Norton 1987a
study. These animals also exhibited a significantly is reported at 0.3 g day with | 0.1 g day due to
greater retention of N than Cashmere goats, reflect- cashmere. This compares with the estimated protein
ing the greater values associated with superior N 3 6.25 gain in fleece of cashmere goats of 4.4
production of total fibre by Angora goats. While
H . Galbraith Livestock Production Science 64 2000 81 –93
89 Table 8
Growth, digestive and nitrogen balance characteristics of Cashmere and Angora goats, in response to methionine supplementation day 0–40 modified from Souri et al., 1998a
a
Treatment groups Significance of
b
contrasts CO
CS AO
AS S.E.
D G
Dry matter intake DMI, g day 925
921 768
769 35.6
Live-weight gain LWG, g day 49.7
74.4 44.7
64.1 8.91
Faecal-N excretion g day 6.12
6.2 5.7
5.7 0.21
Urinary-N excretion g day 7.5
7.6 6.0
4.7 0.42
N retention g day
2.93 3.20
3.11 4.21
0.33
0.75
mg kg LW day
182 194
212 294
20.9
21
g kg
N intake day 178
187 210
290 19.8
a
C, Cashmere; A, Angora; O, no supplementation; S, methionine supplementation.
b
Contrast: D, diet, G, genotype, Interactions between diet and genotype did not attain significance.
there appears to be no other report in the literature relative partitioning was unchanged in response to
describing such responses in body and N retention to improved supply. This represents an interesting
dietary methionine, evidence for response to im- conclusion given the disproportionately high con-
proved protein nutrition in Australian Cashmeres has centration of cysteine cystine in hair fibre see Table
been described, for example, by Johnson and Rowe 1.
1984 and Ash and Norton 1987a. These latter workers demonstrated significant increases in the
3.2. Effect of sulphur amino acid supplementation daily gain of nitrogen in addition to empty body
on the composition of hair protein .
weight, water, fat and ash in response to increases in dietary crude protein concentration from 113 to 163
While it is clear that responses to protein and
21
and 209 g kg
. That these responses did not methionine supplementation produce superior yields
produce significant effects on final empty body particularly of mohair and sheep wool there is little
weight and chemical composition as a proportion of systematic information on the proteins which com-
empty body weight was attributed to the extensive prise the major components of the hair fibre and how
ruminal degradation of the crude protein and only they might be altered by increased deposition in the
small differences in protein amino acids available follicle. Gillespie 1991 has demonstrated the simi-
for uptake at the small intestine. The use of the larity of protein fractions in the products of a number
rumen-protected intestinally-available product essen- of different ‘keratinised’ integumental tissues includ-
tially improves delivery of absorbable methionine at ing hair from different sources, hoof horn and human
the small intestine and the results shown in Tables 7 finger nails. In the absence of specific studies on goat
and 8 indicate the presence of response to a dietary hair production, it is useful to consider the responses
deficiency of this amino acid. in sheep wool to increased sulphur amino acid
In another study Souri et al. 1997, showed that supply. In the study described by Gillespie 1991,
10-month-old Angora goats given basal diets con- sheep were infused abomasally with sulphur-con-
taining | 100 g crude protein per kg DM and taining amino acids methionine, cysteine or pro-
supplemented with
rumen-protected methionine
teins containing high concentrations of these amino Smartamine
E M grew more quickly and had acids Table 9. In addition to a greater rate of
greater retention of dietary N than controls. How- growth, marked increases in the cysteine concen-
ever, the relative partitioning of dietary N to mohair tration of wool were recorded. These increases were
N was unchanged at ¯ 0.40. These results suggest largely attributed to a greater synthesis of the ultra
that the animals were deficient in methionine cys- high-sulphur UHS proteins in the intermediate
teine in both fleece and non-fleece tissues and that filament-associated matrix fraction containing | 30
90 H
. Galbraith Livestock Production Science 64 2000 81 –93 Table 9
Amino acid composition residues 100 residues of sheep wool and its constituent high sulphur proteins before BS and after AS sulphur enrichment modified from Gillespie, 1991
Wool High sulphur proteins
d
BS AS
BS AS
UHS Threonine
6.0 6.9
10.0 10.4
11.1 Leucine
8.1 6.6
4.1 2.8
1.3 Phenylalanine
2.9 2.1
2.0 1.4
0.5 Lysine
3.0 2.8
0.6 0.6
0.9
a
Methionine 0.5
0.4 NP
NP NP
b
Cystine 9.5
13.8 NP
NP NP
c
SCMC NP
NP 20.1
24.5 29.9
a
NP, not present.
b
Expressed as half-cystine.
c
S-Carboxymethycysteine.
d
Ultra-high-sulphur proteins.
residues per cent of cysteine measured as S-car- question was tested in vitro Souri et al., 1996 using
boxymethyl-cysteine. This fraction has been as- our follicle explant system Ibraheem et al., 1994.
cribed importance in the formation of the inter- Small skin samples were obtained by approved
mediate filament–matrix complex, and in the pro- technique from the mid-side area of three 18-month-
duction of cystinyl disulphide bonds associated old, Scottish male castrate Cashmere goats in the
with properties of strength and elasticity of the hair time period August to September. Anagen cashmere
fibre. The increased diameter of mohair fibres fol- follicles were isolated and incubated | 90 treat-
lowing methionine supplementation is in keeping ment in Williams E medium without cystine, cys-
with the suggested role of an increased intermediate teine or methionine O and then supplemented to
filament-associated protein fraction in producing a give final concentrations as follows: 100 mM
greater volume of cells of the hair cortex. Recent methionine 1 330 mM cysteine 1 83 mM cystine
studies Galbraith et al., 1998 have described the MC; 100 mM methionine without cysteine or
effect of
rumen-protected methionine
supple- cystine M: 330 mM cysteine 1 83 mM cystine
mentation in increasing growth rate and cysteine without methionine C.
deposition in hair and claw horn of Angora goats. It The results Table 10 indicated that the follicles
is interesting to note that the hardness of claw horn in treatment MC containing all of the sulphur amino
from methionine-supplemented animals measured by acids exhibited typical hair growth rates for up to
duropenetrometer was greater than that of unsup- 120 h incubation. Follicle growth and viability at 72
plemented controls. h was significantly reduced in the absence of
methionine with cystine and cysteine present treat- 3.3. Effect of methionine and cysteine on hair fibre
ment C. In addition, methionine supported growth growth and viability in vitro
of follicles in the absence of cysteine and cystine to about 0.75 of that recorded in its presence. It is
The results in the studies described above did not concluded that methionine is essential to support hair
explain the relative importance of methionine and growth and viability and that cysteine cystine are not
cysteine for hair growth or address the issue of essential provided that methionine is present. The
transulphuration studied in sheep wool, e.g. by results also provide strong evidence for the presence
Downes et al. 1964 and alluded to by Ash and of a transulphuration pathway within the cashmere
Norton 1987a in the lack response of Cashmere secondary hair follicle.
goats to protected methionine supplementation, or More recent studies Souri et al., 1998b have
consider the question of whether methionine can demonstrated the transfer of radioactivity-labelled
convert to cysteine in the hair follicle. This latter sulphur from methionine to form cysteine in isolated
H . Galbraith Livestock Production Science 64 2000 81 –93
91 Table 10
absence of more definite information, the anagen
Elongation mm and number of viable V anagen cashmere hair
cashmere hair follicle appears to be similar to that of
follicles in 24-h growing periods in vitro modified from Souri et
sheep wool or mohair follicles apart from having a
al., 1996
reduced capacity to grow hair. Comparisons of
a,b
Treatments P.S.D
differences in the capacity to grow hair were made in
CM M
C O
the in vitro studies of Lee et al. 1994. These
a a
b b
workers compared secondary follicle characteristics
24 0.11
0.09 0.05
0.03 0.07
a a
a a
V 89
70 54
41 9.6
of entire male Siberian Cashmere goats with male
a b
c c
castrate Angoras and demonstrated under similar
48 0.11
0.08 0.04
0.03 0.06
a a
a a
V 83
58 26
25 10.0
conditions that the mohair follicle produced a 4.9-
a b
c c
times greater volume of fibre, exhibited a 4.6-times
72 0.13
0.09 0.02
0.02 0.07
a a
b b
greater concentration of DNA, had a 7.6-times
V 62
42 9
2 6.0
14
a a
greater uptake of U- C-labelled leucine per follicle
120 0.12
0.10 0.00
0.00 0.07
a a
and deposited 1.6-times more protein per mg DNA.
V 54
38 7.4
These results suggest that the mohair follicle had
a,b
Values are means with pooled standard deviation P.S.D.
more cells than cashmere in addition to an intrinsi-
Values in the same row with different superscripts are significantly
cally greater capacity for protein synthesis per cell. It
different P , 0.05. See text for treatments.
is logical, therefore, to conclude that one component of a failure to respond to improved sulphur amino
mohair follicles. These results suggest that actively acid nutrition by increasing cashmere production is
growing anagen cashmere and mohair secondary that the requirement is already met and that there is
follicles are at least partially independent of the an absence of deficiency for these nutrients. Other
synthesis of cysteine cystine in, and supply from, factors controlled by genotype or nutrition may thus
other tissues. However, the studies do suggest that be expected to limit cashmere production as sug-
maximum hair follicle growth requires the presence gested by Johnson and Rowe 1984.
of methionine and cysteine cystine. Pierzynowski et It may also be concluded that where a response
al. 1997 have also demonstrated that administration occurs such as under sub-maintenance nutrition or as
of a mixture of dipeptides methionine–leucine and shown in Table 7 above, the provision of methionine
cystine–leucine to a perfused area of skin of Angora overcomes a limitation imposed by sulphur amino
goats increased the production of mohair compared acid deficiency.
with an infusion of saline. This effect was associated with altered concentrations of amino acids in venous
blood. The authors suggested that the dipeptide
4. Conclusions
