Riesgos, Planes y legislación

two

eUbsequent p81'104&

During the first per10d

(JUne

to

(J'uly)

tho "loweat " average

envi

rolll'Dell

tal

terJlleraturea were

found

to

correspond to

"the

lowest" milk

vield ( 23. 2

_kg.

Gl'OlJp

I) ,

the "highest " average

tenveraturoB

to the " lntermed

iate" vleld

( 24.. 2 kg. GroUp II) ,

and tho

"medium"

teq>8reture

to

the

"highest" yleld ( 25 kg. Group .m).

The

opposite

wa e

true o� fat oontent ,

Group

1 glv1ng the

higheet

dal1,

yield

( 744 g. ) fol.lowed bV Group]l

( 722 g. ) and Group iii

(6ga

g.

)

.

In

the 2nd p

e

ri

od

(J�

to August) , 1t has been

stated,

continuous

grazing had

an untavourabl e

etreot

on milk

:rat

ma1nly

due

to "high

max1mum

tenu>eraturee" , and in the

3rd per10d

( August

to september)

housing b¥ dB¥

was found

to lower milk yield, eince hlgh

rnax1nn.u!1

torrperaturee no

- 144 -

loneer occ�d. whUe housing by night increaaed both

mUk

yield and f'at, conten

t

" It i8 remarke

d

� the author toot

" MUch

_{cows should. thererore.}

be

protected h-om extremes or

tCflt)eraturee

(

mnx1

mum

in SUlIIner and m1n1nI1m

in

early 8W1IDer

or

nut�)t:

In

this

Uporiment ot Harless

atroospherlc

tentJel'8tuztefJ have not

_{bean mentioned}

_and

the "highest" ,

"low8st"

and

" intermediate" terlller

at

Ul'e8 ere vague terms.

It heG been stated that

GroUp·I was

subje

c

te

d to

24 hours ­

g1'8z1ng end consequently

_{to the}

"lowest" envil'ODrlJl!fttal

telt1>eratures.

It

_has not been mentioned whether � ahel ter

was prov1ded to protect the animals

from sudden w

e

a

t

her

changes which alone, apart

f'rom

l

o

w tenperature, might have

affeoted production.

Moreover the 71el48 _�

m1lk

and

but

_tel'-rat

8.l'8 not

_{suf'f'lciently d1}

_rte

ren_t

_to show aDl

mBl"ked

effe

_c

t

at

ten;>eratura and

this

d1fterenoe

in

production might be due _{to gro",}

_{d1f'terencee.}

'rhe _{best 1r87}

that

the

exper1ment could be _done 1I8S ( 1 ) ftrsU¥ to

oheck

the produc tion ot tho an1mBls 1n41vldually as well as a

S1'OUp un

d_e

r unitorm oontU. t

lo

ns

at

management and then

( 2 )

t o subj ect

the

_{th:ree groups}

_ot

an1mBl _{B t o the} three _tI'eatmente

seeing

that

all

the an1m8ls were a

d

e_�uate

1J

ted acoording

to l ive

welght and production

and that other oon41tions

exoepting the variations 01' environmental t�eratures were

slrn1J.ar _as

t

a

r

aa l)Osalble.

In

the second

period _ot

t_hi

_s

_{obsenatlon the} high rr1flX1nun ter.t>eraturo8 to which

the ocnre

were

�oeed

during continuous

_{day and}

_night

_grazing

_{had an} unf'ayoureble

effect on

_{the milk fat}

oontent. The

_ettect

ot

tfJrl'pernture

on the butter-tat peroe

n

tage w1ll be dealt with later.

Cont1nu1ne the oXpcrimont during w1nter ( Deoeniler - Febru.al7)

1Iarlass kept _{six Blaak Pied} Lowland oows _in 8 heated

b7l'8

at

six

d1tterent

temperatures.

It haa been _{stated that the}

highest

m1lk yields

were usually

fO\Dld at

mec11um byre

- 14.-5 -

o 0 0 0 0 0

t emperatures -

16

C

{ 61 Fl , 15 C ( 5g

P)

and 10

0 ( 50

P) ;

o 0 0

0

high tarqperuturea - 24

C ( 75 F) and 20

0

(68 F) ,

and low o 0

tOOl>el'stures -

6

C ( 43 PI)

- lowered milk �e1d. It has

been stated that the Beme was true of total fat, but low

b�e teq>eraturcs inoreased th_{e tat} pel'Centage. It _was observed that "the IOOEf& eat1Bf'� otory

teltl>eratures tor

both

o mille a1l(1 rnt perf'ormencc, therefore, ranged

between

10 C

o 0 0

( 50 F) and 16 C ( 61 F). "

According _to H8.l'lsSB the opt1rJllm range

at

enviro_nmental te1Jl)eratUl'8 to

r

_max1mum product ion at

m1lk

lq

o 0 0

between

60 Ii' and 60 P' and

tenperatures aa low ae 43 F gave

the lowest yield. This

�pear8

to be cont1'ad1cto� to the

results ob_tained by Dice _{who tound thnt} the

t�eratures

o 0

between _{23 snd 53 P did} not attect the _,

milk

y1eld �reolablJ.

The

nwnber

of en1mals used by Harless - one tor eaoh tl'8at� - was very small � whether the

en1mal e

were reversed

hils

not

been

mentioned.

Even breed

difference

might be a retrponslble t(�ctor tor

this

_{difference 1n}

witzel and Helzer , JJ.n1verslt� o_t WisconSin, tladlson, _stud1ed

t

he effect

of

teq,erature on p roduction.

They co�nred during two w1nt ers, two herds, each

ot 17

Holato1n-:trleslana, one kept in an insulated etcU barn and the

other

1n

an open pen barn. Menn outside teJll>eraturee

o

0

were 40. a

:m1. �. 8 F

reapectlTely during the

two

periods

o

nnd in the sta1l _barn the t�orature was 46-66 F. I

t

was stated that

1n

the first 7ear ot the e�er1ment milk produc_t1on in nal _ther barn varied _I'll th _ohanges or terrq>erature but _1n the

cold

_{open barn it}

averaged 7. 4,G

_{less than 1n1be}

warm

_1naulate4 born..

Dur1ne

the seoond year when the cows

were

distributed at random. the _{1)roduot1on ot} F. 0 .. M. '.Yen th

e

same

1n

the

warm

and the cold bfl�

( 237)

Sinha and Minnet carried out obsGrYatlons at

- 146 -

milking

butraloes 1n order to ascertain whether alIl' relation­ ship

exists between mdlk

yield and cooling ot the bo� b� daily wetting of the bo� surface. Fifteen buttaloee

8-10 _{years were} oelected so ae '0 obtain a group ot animal s

as near as possible to their maximal yield, Which 1s u8U8ll7

at about 90 days after calTing. Pour sets of obserYatlons were made over consecutive periods

ot

t en da7a each 4Ur1ng t� and June when the da1� oil' t8l'fl>el'6tures T81'led from

o 0

71

-

113 F.

DUring

the

tiret

period the animels were splashed wlth bucketful s ot water tor five mlnu:t.es _morning and evening every dfl¥ two hours betore m1llt

1ng.

Bod¥

temperatures ot

tho en1mals were reoorded inmed1s:t.el7 betore

and

one-halt

hour after eplaehlng. During the

second p

erl

od

no splashing was dono. During the thlrd p erlod "the animals were d1T1ded

into

two sub-groups - one ot which was given dal1� �lash1ng _and the othor none, their average duration ot lactation at this time being 106.2 and

105. 6

�s r8s.peotlvel1 During the tourth period splashing was

toll

owed. _Air

terru:>eratures, relative hum1dlty, bo� tenl)e:ratUl'e Tariatlons,

the fall s in bo4y tenp eraturo after splashing and the oorresponcU.ng average milk yields were recorded every

roo

ming

and

eYen1ng� The bo� t8nl>eratures after aplaahing

o 0

dl'Opped b�

1

to

4 P.

'l'he m1l1t �olds during aplaah1ng periods were ooopered al temate

J.y

with the 71elds during the pr80etU.ng and rollow1ng non-splash1ng per10ds ( this omitted the etrect

of

stage or laotation on production) and al so the �ieldB o� the Bub-groUp 1 were compared with those ot the sub-groUp

11

and the differenoes were stat1stically ennl1'sed. Data preoentod _show that the ¥ie�da or the

animals when splashed were greater than when _not splashed and in eve�

08e8

the dltterencea were h1g� slgn1t1

c

ant. This experiment bears out th

e

�ortance at � wett1ng of cattl e during vexwy hot _weather In tropical countries.

- 147 -

When this is not pI-actloed as a da� routine the' milk yield deoI-eaees. AS hae

been

d

e

alt l'11th elsewhere the heat

dissipation or tho cat_tle

becomes

ditrlo

ul

t when the air o

t� ereture ri ses above

70

P or eo, normal p�alologlcal

t'Unctions or

the

animal

are disturbed; the b� tenpel'Bture

rises _and the m1lk production sutter&

The effeotiveness _ot artificial oooling ot the dalr.y COW8 In overcom1ng the depressing cffecto which the lone continued periods of hot waather havo �on _milk production

( 238)

was reported tram Georgia F-"qler1mental Station.

In

this

experiment tho covs wero art1tioleJ.ly oooled b;r covering them during _{the day with} light _{11Ilal1n oloths}

kapt

lJI)i3t to Bt1nal1- ate c

o

oling

by

evaporation. It was found that oontinued hot

weather

(

temperature no t mentioned

)

\ms the inportant factor

in depressing the milk

y1elds

end art1flc1al cooling was

decidedly effective _1n oao1ng the situation end _� bad effects

In document RIESGOMAP (página 79-83)