PAPERS AND PROCEEDINGS OF THE ROYAL SOCIETY OF TASMANIA, VOLUME 104

[Manuscript received 28 October 1969

THE EFFECT ON WOOL GROWTH IN THE NEW ZEALANDROMNEY OF DIETARY SUPPLEMENTS OF NORMAL

AND TREATED CASEIN

By

J. MeG. BRYDEN­

(Communicated by Dr W. Bryden)

(With four text figures)

ABSTRACTAn experiment was conducted to determine the

effect of chemically treated casein supplements onwinter wool growth. All sheep were housed inindividual pens and fed a basic diet of chopped hayand oat grain at two levels-half the sheep receiveda maintenance ration calculated on body weight,and the other half received a half-maintenanceration. Within each of these two groups, a furthersubdivision was effected. One group received 30 gof untreated casein, one group 60 g of untreatedcasein, a third group was fed 30 g of treated caseinand the fourth group received 60 g of treated caseinper day. This situation was similar at both levelsof basic diet.

All sheep were weighed each week and theirweights were recorded. Small but positive increasesin body weight were noted, and the relationshipbetween casein and this increase is discussed.

A comparison of treated versus untreated caseinwas made each month for five months, commencingin April 1968, and concluding in September 1968,and this comparison was considered in terms ofwool weight, fibre length and fibre diameter.Similarly, a study of energy levels and treatmentof casein was made and the significance of theseresults are discussed.

INTRODUCTIONThe rate of production of keratinised fibres from

skin follicles in sheep can be profoundly influencedby nutrition. Some of the earliest controlledexperiments demonstrating this fact appear to bethose reported by Weber (1931) and Fraser andNichols (934). Although there were other reportsin the literature which suggested that wool growthwas probably affected by nutritional factors, thesewere concerned with observations of seasonalvariations in wool growth of grazing animals(Lush and Jones, 1923); Duerden and Bosman1927; Hardy and Tennyson, 1930; Burns, 1931). '

During the late 1920s and early 1930s a sub­stantial controversy developed around the problemof whether or not the sheep could synthesisecysteine (Marston and Robertson, 1928; Barritt andKing, 1926, 1929; Rimington, 1929; Rimington and

$: Present address: Department of Agricultural Science U ni-versity of Tasmania. Hobart. Tasmania 7001. '

R.S.-8

Bekker, 1932; Pollard and Chibnall, 1934). At thistime, because of the relatively large amount foundin wool, cysteine was regarded as an essential aminoacid for wool growth. An increase in wool growthdue to a supplement of blood meal fed to grazingsheep was inferred by Marston (932) to be dueto the intake of cystine contained in the bloodmeal. He also attributed the superiority of asupplement of yeast as compared with casein forwool growth to the higher cystine content ofyeast. The first reported response of wool growthto the administration of a SUlphur containingamino acid was given by Marston (1935). Thebiological significance of methionine was notknown at this time.

Under normal circumstances, ruminants makeinefficient use of high protein diets. It has been shownthat some proteins are readily degraded by rumenmicro-organisms to ammonia, a large part of which~ay then be absorbed and excreted as urea. Whendietary protein content is high, the extent ofprotein. degradation probably exceeds proteinsynthes1s by rumen micro-organisms (McDonald19.48) . Thus substantial amounts of dietary pro~tem may be lost to the animal. Considerablelosses of nitrogen due to ammonia production inthe rumen have been demonstrated with protein­rich meals and soluble proteins such as casein(McDonald, 1952; Annison, et al., 1954; Chalmersand Synge, 1954). However, nitrogen retentionand conversion to animal products such as woolare enhanced when proteins are administereddirectly into the abomasum or duodenum(Chalmers, et al., 1954; Reis and Schinckel 19631964). ' ,

The latest development in the administration ofprotein into the abomasum or duodenum is to useprotein protected from rumen microbial degrada­tion by chemical modification (McDonald 1967)Any protection procedure would need to leave th~protein in a form capable of digestion and absorp­tion further along the alimentary tract so that theprotein could be utilised. The pH differentialbetween the rumen, normally above pH6, and theabomasum, normally below pH3, allows scope forreversal of the effects of coating or chemical treat­ments.

Sheep produce wool at the maximal rate of whichthey are capable for only a brief period in each

99

102 THE EFFECT OF WOOL GROWTH IN THE NEW ZEALAND ROMNEY

The energy level in terms of fibre length is onlysignificant in the periods 29 May to 25 June and26 June to 23 July. During the period in whichall sheep lambed, that is 24 July to 20 August, the

pregnancy factor may have been more of a com­plication than was first thought.

Treatment of casein in the ration showed asignificant response for all months of the experi­mental period except 26 June to 23 July.

FIG 2(a) ::;roup

SEPJUL Y AUG

Wool Weiqhts (Maint.)

MAY JUNE

FIG. 2(b) Group Mean

C 30

I

C 60

II ..J

TC 30

---r--

TC 60I

0·5APR

1·0

E 1·00>

2·0

0·5

2·0

1 ·5

-'o~ 1·5

1· 5

1· 0

1 ·0

s= 0·5S2

:g 2'0

~ 0·5u

roN 2.0~

fjo 1·5S2

SEP

Weights (Half Maint,)

JULY AUGJUNE

Mean Wool

C 30

II I

C 60

II

TC 30

I I

TC 60

I

0·5APR MAY

1·0

1·5

-' 2·0oo~ 1·5

1·0

0·5

I-

f2 0·5

1·0

2·0

1·5

2·0

~ 0·5'"uroN 2.0

DISCUSSIONThe increase in the rate of wool growth obtained

in this experiment when casein, chemically treatedwith formalin, was fed, is in agreement with theresults of Reis and Schinckel <1961, 1963). Theextra energy available from the casein was far toosmall to account for the increases in wool growthwhich were obtained. A similar untreated supple­ment may not result in increased wool growthwhen added to the diet and exposed to ruminalactivity, and this is borne out in the results ofthose sheep receiving untreated casein. Thisagrees with the lack of wool growth response tolevels of dietary protein above 8% in the experi­ments reported by Ferguson (959), It thusappears that protein, apart from its energy value,can specifically stimulate wool growth and that theS-amino acids may be especially important. How­ever, the specific function of cysteine in stimUlatingwool growth is not known at present.

Although cysteine and methionine are presentin the form of S-amino acids, their exact amountsare not known. The mechanism of action of thesetwo S-amino acid supplements in stimUlating woolgrowth is obscure but several possibilities exist(Reis and Schinckel, 1963). There may be somegeneral anabolic effect which indirectly affectskeratin synthesis in the follicles. There is anindication of such a general anabolic effect becausethere was a positive increase in body weight in allsheep receiving a maintenance energy ration pluscasein, but not affected by pregnancy. There mayalso be direct effects on keratin synthesis in thefollicle. Cysteine may be the limiting amino acidfor keratin synthesis as suggested by Marston0935, 1948, 1955) and the feeding of casein maysimply increase the supply of substrate availablefor keratin synthesis. There may also be someother specific effect of cysteine or of the sulphuror sulphydryl component of the molecule, in the

J. MeG. BRYDEN 103

35

35

35

30

C 30

C 60

I

TC 30

TC 60I

35

30

25

35

30

25

'" 35c

§E 30c:wt;:; 25="«0 35wc:

'" 30~

25

C 30I

I IC 60

II

TC 30

I

Tc 60

30

35

25

25

30

25

mcou

Ec:wf-

~ 25«owc:

'"4: 30

Mean Fibr"e Diameters (Half Maint,)

APR MAY

FIG 3(a)

JUNE

Group

JULY AUG SEP APR MAY

FIG. 3(b)

JUNE

Group Mean

JULY AUG SEP

Fibre Diameters (MainO

5

15

10

15

C 30

C 60

TC 30

TC 60

15

10

5

15

10EE 5If- 1519z~

10wc:

'" 5c:

15

10

5

C 30I

COO

TC 30

TC 60

5

5

5

15

10

10

15

EE

wc:

'"

::r:f­oZw-'

10

APR MAY JUNE

FIG. 4 (a) Group Mean

JULY AUG SEP

Fibre Length (Half Maint.!

APR MAY JUNE JULY AUG

FIG. 4 b Group Mean Fibre Length (Maint.)

SEP

TABLE V-THE EFFECT ON FIBRE DIAMETER OF LEVEL OF CASEIN IN THE RATION (30 g/DAY v 60 g/DAY), ENERGYLEVEL OF RATION (0.5 M v 1.0 M) AND TREATMENT OF CASEIN (FORMALIN TREATED v UNTREATED)

PRE-EXPERIMENTAL EXPERIMENTAL

Period ... .... .... .... 1.5.68-28.5.68 29.5.68-25.6.68 26.6.68-23.7.68 24.7.68-20.8.68 21.8.68-17.9.68

Casein level- Diam. (p,) DiU. Diam. (p,) DiU. Diam. (p,) DiU. Diam. (p,) DiU. Diam. (p,) DiU.30 g 32.4 30.8 30.0 29.3 30.8

60 g 34.2 1.8§ 33.4 2.2* 32.1 2.1 * 31.1 1.8* 31.9 1.1§

~

Energy level- is:0.5 M 33.7 32.7 29.5 30.1 31.7

('>

P

1.0 M 33.8 0.1§ 32.5 -0.2§ 32.5 3.ot 32.2 2.1' 32.9 1.2§ I:l:I

~t:I

Casein treatment- t'JZ

Untreated 32.3 31.8 29.0 29.3 30.8

Treated .. 34.1 1.8§ 33.4 1.6§ 32.0 3.0:1: 31.1 1.8* 31.9 1.1§

5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1%Minimum difference required

for significance 2.23 2.98 1.88 2.51 1.80 2.41 1.68 2.25 1.77 2.37

* P <0.05; t P <0.01; :I: P <0.001; § Not significant

....o0:>

TABLE VI-THE EFFECT ON FIBRE LENGTH OF LEVEL OF CASEIN IN THE RATION (30 g/DAY v 60 g/DAY), ENERGY ..,LEVEL OF RATION (0.5 M v 1.0 M) AND TREATMENT OF CASEIN (FORMALIN TREATED V UNTREATED) II:

l"l

l"lOJ

PRE-EXPERIMENTAL EXPERIMENTAL OJl"l0

Period 1.5.68-28.5.68 29.5.68-25.6.68 26.6.68-23.7.68 24.7.68-20.8.68 21.8.68-17.9.68..,0

Length Difj. Length Difj. Length Difj. Length Difj. Length Difj. OJ

Casein level- (mm) (mm) (mm) (mm) (mm) ~

30 g 12.5 11.8 11.6 12.2 12.900I:"'

60 g 13.0 0.5§ 12.7 0.9' 12.3 0.7§ 12.9 0.7§ 14.2 1.3t ":<I0

Energy level- ~..,0.5 M 12.8 11.6 11.1 13.2 13.2 II:

H

1.0 M 13.6 0.8§ 12.8 1.2t 12.8 1.7t 13.0 -0.2§ 13.9 0.7§ z..,II:

Casein treatment- l"l

Untreated 12.5 11.8 12.5 12.2 12.9 Zl"l

Treated 13.9 1.4§ 13.7 1.9:1: 12.3 -0.2§ 13.9 1.7+ 15.1 2.2:1: :::JNl"l>I:"'

5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1% 5% 1% 0.1% >zMinimum difference required t:l

for significance 1.8 2.1 - 0.73 0.98 1.29 0.86 1.15 1.51 0.82 1.10 1.45 0.79 1.06 1.39 :<I0~

* P <0.05; t P <0.01; :I: P <0.001; § Not significant zl"l>1

J. MeG. BRYDEN 107

follicle. This effect may be a stimulation of mitoticactivity in the follicle bulb since there is muchevidence that sulphydryl groups play an importantrole in mitosis (Stern, 1959; Mazia, 1959, 1961).Also there may be increased production ofco-factors important in protein or energy metab­olism. Thus, cysteine is involved in the synthesisof glutathione and co-enzyme A (Reis and Schinckel,1963) .

Restriction of wool growth by poor nutrition isassociated with a reduction in length and diameterof individual fibres (Daly and Carter, 1956). Itwas considered by Fraser (934) that fibre diameterwas more susceptible to nutritional influence thanwas fibre length and Galpin (948) found thatchanges in length precede changes in diameter.From this she suggested that diameter is influencedless by poor nutrition than is length.

Under normal feeding regimes, Romney sheepfed a maintenance ration throughout the winterexhibit a seasonal decline in wool production. Thisdecline is caused by a number of factors, the twomost important being photoperiodic stimulus andnutrition. While the photoperiodic stimulus can­not be altered under normal circumstances, thefeeding regime can be. In the present experimentsheep fed a half maintenance energy ration showedan accentuated decline in wool production and thegreater proportion of this can be attributed to thefact that these sheep were in a state of negativeenergy balance. Feeding of treated casein in thisexperiment has arrested this seasonal decline ofwool production and so although no great increasesin wool weight due to the feeding of treated caseinare apparent, when considered in terms of seasonalwool production, the differences are very real.

In this experiment, sheep receiving a mainten­ance energy ration plus untreated casein showed areduction in weight of wool grown when comparedwith those receiving treated casein, and this reduc­tion was accompanied by a reduction in fibrediameter only. Earlier workers suggested thatchange in fibre diameter was mainly due to changein the width of the medUlla, but recent work(Ryder, 1956a; Henderson, 1965) has shown thatchanges in diameter of the fibre are accompaniedby changes in the thickness of both the cortex andthe medulla.

The physical basis of the length/diameter ratiohas been shown by Rudall (955) to be the dimen­sional structure of the follicle papilla. However,both Fraser (964) and Henderson (965) foundthat although a clear association of these dimen­sions was demonstrated within sheep the relation­ship did not hold between sheep.

The length/diameter ratio in the present investi­gation altered as the nutritional regime improved.In the half maintenance energy group receiving30 g of untreated casein per day, the effect wasseen as a reduction in both length and diameter,the effect on length being greater. Feeding 30 gof treated casein substantially reduced the effect onlength. Short (unpUblished) and Henderson(unpublished) have noted that at low levels ofnutrition any change in fibre dimensions inducedby nutritional regime is seen primarily as a reduc­tion in length. In the low energy groups receiving60 g of untreated casein per day there was less

effect on fibre length than in those sheep receiving30 g per day, and feeding 60 g of treated caseinper day produced a proportionately greater effecton fibre diameter than on fibre length.

Sheep in the maintenance energy group receiv­ing untreated casein showed the reduction in woolweight as one of reduction in fibre diameter ratherthan reduction in length. It was found that whilea reduction in fibre diameter occurred in sheepreceiving untreated casein, those receiving treatedcasein showed an increase in fibre diameter. Therewas a greater proportionate increase in diameterthan in length. This agrees with the results ofSchinckel (962) and Reis and Schinckel (964).Schinckel (962) observed an increase of 71% infibre cross-sectional area during casein administra­tion per abomasum and this increase accountedfor 46 % of the increased wool growth. Schinckelpointed out then that there was no way of deter­mining the relative contributions of rate of cellproduction and of cell volume changes in cross­sectional area and length of fibres. It is notpossible to estimate accurately changes in themitotic rate of matrix cells from measured changesin fibre output and cortical cell volume, nor toestimate changes in fibre cell volume from observedchanges in mitotic rate and fibre output (Short,et al., 1965).

From the wool growth figures obtained in thisinvestigation during the last of the experimentalperiods it would seem that pregnancy in sheep hasa more positive effect on wool growth than wasfirst thought. This has since been shown to besignificantly correct (Bryden, unpublished). Inthe design of the experiment, lambs were removedwithin forty-eight hours from those sheep whichlambed on the presumption that lactation hadmuch more effect on wool growth than did preg­nancy. However, Coop (pel's. comm,) has shownthat any stress effect in terms of wool growth hasa long carry-over effect, and so the greater effectwhich can show up during lactation is most likelya carry-over effect from pregnancy.

The level of casein fed during the experimentalperiod was not a significant factor in terms ofweight of wool grown. This indicates either that30 g per day of casein is as effective as 60 g perday, or that pregnancy in some sheep masked theresponse. This latter explanation would appear tobe the logical one since during the last experimentalperiod the difference between 30 g and 60 g perday of treated casein was much greater than forthe rest of the experimental period when someewes in most groups were pregnant.

A significant relationship between the level ofcasein and fibre diameter occurred for all but thelast period of the experiment whereas significancebetween level of casein and fibre length onlyoccurred in two periods. This might indicate thatfibre diameter is much more sensitive than fibrelength to the effects of pregnancy.

A significant relationship between energy levelof the ration and wool growth occurred in all butthe first of the experimental periods. The factthat no significance was evident during the firstperiod is likely to be due to a carry-over effectfrom the pre-experimental period. Under ordinaryfeeding regimes, the rate of wool growth closely fol-

108 THE EFFECT OF WOOL GROWTH IN THE NEW ZEALAND ROMNEY

lows the intake so that the greater the intake thegreater the wool production. The rate of wool pro­duction at very low levels of feeding is understand­ably very small, but it is apparent and continues atthe expense of other tissues.

The relationship between energy level and fibrelength was significant during the first two monthsof the experimental period only, although in thefinal period significance was approached. Thus,the only period when any real difference was noticedwas during 24 July to 20 August, the period inwhich all pregnant ewes lambed.

Low significant values were obtained for therelationship between energy level and fibre diameterfor all periods except 26 June to 23 July. Again,these values approached significance levels andpossibly the complication caused by pregnancy mayhave been an important factor in these results.

It is apparent in the results of this experimentthat there was some sort of an interaction betweenthe response 01 wool growth to administration oftreated casein and time, although this cannot bedefinitely assessed. The magnitude of the responseto casein and S-amino acid supplements willobviously depend on how nearly the wool growthrate on the basic diet approaches the geneticpotential for wool growth.

In the experiments of Reis and Schinckel 0961,1963) the intake of basic diet was kept at amoderate level so that wool growth would be wellbelow the maximum.

Although non-significant results were apparentin some instances throughout this investigation,the fact that most approached significance wouldtend to indicate that the number of sheep pergroup, five, was not enough. The use of largernumbers per group would most likely have shownthese results that approached significance to bein fact significant.

Sheep which received a maintenance ration plusa supplement of casein increased in body weightduring the experimental period. This increase,although small, was positive. There seemed to besome increase in favour of those sheep receivingtreated casein, regardless of level, over those sheepreceiving untreated casein, although the differencewas only slight.

Various studies have clearly shown that rumin­ants can make use of non-protein nitrogen com­pounds in lieu of a part of the protein intakerequired for growth and maintenance. The explana­tion seems to be that micro-organisms in therumen can use non-protein nitrogen to build theirbody protein which is in turn digested in the truestomach and intestines. Lofgreen, et al. (947),suggested that the quality of protein as fed in therations of lambs may be of importance under someconditions. It seems logical to assume that ifprotein quality has an effect upon the nitrogenretention of lambs that it may have some similareffect upon the gains in weight in feed lot opera­tions.

Comparing control sheep with those receivingDL-methionine or L-cysteine administered into theabomasum, Reis (967) found that the treated sheepshowed small but consistent and positive increasesin body weight. In contrast to effects on wool

growth there was a progressive increase in bodyweight with each increment of S-amino acid.

In the present stUdy, the significance of bodyweig'ht increase is difficult -to ascertain, due to thecomplications caused by pregnancy. For sheepbeing fed a maintenance ration alone, body weightshould remain constant to within ±1 Kg per week,and thus it may be assumed in this case that theincrease was due to the supplement of casein.

ACKNOWLEDGMENTSThe author wishes to thank Professor A. E.

Henderson of the Wool Science Department,Lincoln College, New Zealand, for his helpful adviceand criticism.

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