“CHOLESTEROGENIC" DIETARY FACTORS AND MILK AND MILK FAT YIELDS IN DAIRY COWS Pellervo Saarinen Department of Animal Husbandry , University of Helsinki Received November 15, 1958 In an earlier publication, »Diet and plasma cholesterol in dairy cows» (5), it was established that there is a statistically verifiable positive partial correlation between the cholesterol level in the blood of the cow and certain dietary factors. The most important of these factors, in addition to the energy requirements of the animal, seem to be the digestible crude fat and fibre present in the food ration. However, the same kind of effect can also be produced by obesity of the animal and in certain cases even by temporary overfeeding. As the liver is the only organ supplying significant amounts of cholesterol to the blood plasma and therefore is the actual source of plasma cholesterol, it was supposed that the grade of plasma cholesterol may possibly be used as a reliable indicator for some factors which affect the normal liver functions, but which are otherwise hard to establish (5). In addition, from the point of view of animal nutrition it would be of prime im- portance to know to what extent these cholesterogenic dietary factors result in strain on the liver and/or other metabolic organs, or whether they reduce the stress. To throw light on this latter group of questions we have tried at this institute to complete the picture given by blood plasma cholesterol measurements, at the same time determining the quantity of 17-ketosteroids segregated in the urine. The effect of ACTH and cortisone injections on the level of blood cholesterol has also been examined. According to the results obtained, variations in the function of the pituitary-cortical system do not have any particular effect on the level of plasma cholesterol in the blood, or vice versa. Investigations which are at present being carried out on simultaneous variations in thyroid function have as yet not given any results in which the picture given by the cholesterol measurements can be made fundamentally clearer under normal conditions. As a fourth possibility, an attempt has been made to use the variations in the level of milk yield in explaining possible effects from strain. https://www.c-info.fi/en/info/?token=WfMnD9oL48ZY6woV.WFx70LhiWohiDJqEQnIVZg.x2XbklmeivgUl0TaEMRtcPfNsR79qHDNLvHttF-rFDYKzkQ-Jg1zS8_XzbM5ZWTUGRIYnOrMrxNWUAxMYhAlsdS1RZuDXcwAm7nt9H5IU29XJhlkee6-DQt4wfDsVj4O1pqRaK4gofJLbbCrPHmWfrG07lBBdb820Lj1J5ManA In addition to the partial correlation between the dietary factors and the level of blood plasma cholesterol in the cow, mentioned at the beginning of this pa.per, the author has reported earlier that a positive partial correlation also exists between the milk or milkd fat yields and the level of blood plasma cholesterol in the cow (4). In view of this, it is possible that the effect of the cholesterogenic dietary factors can be verified directly from variations in milk or milk fat yields. Statistical investiga- tions have thus been made to examine whether the existing cholesterogenic factors studied in earlier investigations have any specific effects on the milk or milk fat yields. Experimental procedure Investigations have been made on the dietary factors observed in an earlier investigation as probably having some kind of effect on the level of blood plasma cholesterol (5). The material for analysis was obtained in two different ways. First, calculations were carried out using the experimental results obtained from 12 feeding tests (5, trials I—XII) made to investigate the effect of diet on the level of blood choleste- rol. These results were then checked separately, using a second series of experimental results obtained from feeding trials (trials XIII—XXVII) carried out at the Depart- ment of Animal Husbandry, Agricultural Research Centre, for other purposes and also suitable for this purpose. Only results from normally fertilized animals were taken in these feeding trials. The trials had been carried out on estates where there was some certainty that the cows had been fed approximately to standard for several years in succession, and that they had normally received sufficient energy, protein and minerals from their food. All the trials had been carried out during a period of indoor feeding, using the individual feeding method. Trials I—XII comprised several experimental periods of a comparatively short duration, only about two weeks in length. Trials XIII—- XXVII were of longer duration, lasting about four months. They consisted of three 30-day experimental periods, to which were added additional 10-day change-over periods. Eliminating the effects of the stage of lactation and variations in nutritional requirements, the level of yield (x,) was measured as a relative deviation from each individual normal lactation curve for each experimental period. For the same reason an attempt was made to express the dietary factors as far as possible as quantities independent of the stage of lactation. For use in comparison, curves for the normal yields of the cows were plotted for the year in which the short-period tests had been performed (trials I—XII), as well as for the previous year and the year following, i.e., on the basis of the average yields for three successive years. Further, an attempt was made to eliminate the temporary effects of possible diseases and nutritional disturbances. For the longer period feeding trials the normal curves were plotted only on the basis of average yields for the year preceding and the year following the year of the tests. 3 Table 1. The variables, their averages (M), standard deviations (d) and the rangesof variations in the material used. Series of tests n Level of milk Level of milk Level of Level of Dig. cru- Dig- crude fat Cows yield % of fat yield % of net ener- protein de fibre intake pregnant normal normal gy in- intake, intake, g/fu.req. g/kg live days take, % of the g/kg live weight % of the require- weight require- ments ments Xla Xu, X2X, X4X, X, X, I— IX cows in nor- mal conditions 481 M 103.6 105.7 120.6 1H.6 3.2 46.9 0.83 61.3 Ö 25.9 23.17 15.15 16.62 1.12 17.93 0.30 78.2 Range 10—210 10—230 90—190 90—175 1.6—6.1 10—105 0.25—2.3 —l5O h 250 tX—XII well condi- tioned cows 155 M +0.33' + 40.9 2 113.11 120.47 3.1 45.2 0.84 —7.8 6 1.78 123.5 16.27 10.98 0.38 14.80 0.27 118.6 Range —6.6— + 6.0 1 —3OO— + 4202 85—180 95—165 1.9—5.1 10—110 0.15—1.4 —2OO 1-275 XIII—XXVII con- trol 1435 M 105.3 103.7 103.4 109.4 3.9 34.9 0.71 6 19.54 18.2 8.56 18.78 1.53 1.68 0.19 Range 30—190 50—180 75—135 65-170 1.7—8.5 10—80 0.15—1.4 1 Difference from average kg/day 8 Difference from average kg/day 4 The momentary milk and fat yields obtained from the experimental feedings were calculated on the basis of the average values for 10-day periods in each experimental period. The relative milk yield was determined by calculating what percentage the milk yield in the experimental feeding wras of the yield according to the normal lactation curve for the corresponding period of time after calving. Otherwise the experimental and analytical methods of calculation were the same as in previous investigations (5). The investigation material, the different variables, their average values and ranges of variation are presented in greater detail in Table 1. As Table 1 shows, on an average the level of net energy and digestible crude protein intake was somewhat above the requirements of the animals, but a few cases of slight under-nourishment were included in the material. In trials I—XII the net energy intake varied from 85—190 % of the standard requirements, and the digestible crude protein intake varied from 90—175 %. In trials XIII—XXVII it was originally attempted to keep to the same lower limits. However, in some individual cases, the corresponding lower limits in some of the feeding trials in this series were lower than these, being 75 % in the case of net energy and 65 % in the case of digestible crude protein. Results First the results were calculated on the basis of the actual deviation values (kg/day). The combinations of the results from each series are presented in Table 2 in the first and last rows of the figures. As appears from the figures in the last column of this table, a slight negative effect of the lactation stage and or of pregnancy (x 7) on the yield could still be statistically verifiable. On closer examination, this was observed to be due, at least in part, to the fact that the variations are generally Table 2. Coefficients of partial correlation when the actual difference in milk or milk fat yield (X, = differences from normalkg/day) is considered as the dependentvariable and the level of net energy intake (X 2 = % of the requirements), the level of dig. crude protein intake (X, = % of the requirements), the dig. crude fibre intake (X, = g/kg live weight), the dig. crude fat intake (X 5 = g/Sc. feed unit required and X, = g/kg live weight), and the stage of lactation (X, = cows pregnant days) as independentvariab- les. Trials I—IX. Xormallv fertilized cows in normal condition. X 2 = level of net X 3 = level of X, = dig. crude X 5 = dig. crude X 8 = dig. crude X, = cows preg- energy intake protein intake fibre intake fat intake g/fu. fat intake g/kg nant days req. live weight Actual difference in milk yield r 12;84867--01099 r13;245fi7 +0.04.74 fj 4; ä35g7 -+(!• 1 193 r45;. 0.3054 rK,;23457 “ +0.4657 ri;;23456 - -0.1 31 1 Relative difference in milk vield r 12;34567 = -°- 1923 r 18;24567 =+° 0382 r u;23567 +'»-0493 r 15;5467 = -0.3627 >„..,„,- +0.3568 rI7;aMM = +0.0649 Actual difference in milk fat yield r 12;3456- = -°- 20i- '18:24887 =+° o9oo r 14;23567 =+00123 r 15«34C7 = -°"4220 r IKSS467 = +04017 r 17;*5456 = +00672 5 greater during a stage of high yield than during a stage of low yield. If on the other hand, the variations of yield were, measured as percentages of the corresponding level of yield in the normal curve, such an effect no longer seemed to occur, as the last column in the second row of figures in Table 2 shows. For this reason only the coefficients of the partial correlation calculated on the basis of the relative yield values were included in the following tables. A similar attempt was also made to express the dietary factors as variables independent of the stage and level of yield. In this respect only the levels of energy and protein intake (x 2 and x 3) could be determined to entire satisfaction. The crude fibre intake was not quite so easily determinable as an independent quantity. In satisfying the nutritional requirements of the animal by making the concentration ratio of the food ration at the same time such that undisturbed utilisation of the food was possible, the crude fibre content of the food ration, calculated either as percentage dry matter weight, in grams per feed unit, or in grams per kilogram live weight, varied according to the stage of yield. However, the last-mentioned quantity was least dependent on the level of yield in the experimental material and generally in practice, too. Because of this, the crude fibre intake was measured in grams per kilo live weight in the accompanying calculations. For the same reason, the digestible crude fat intake was measured in grams per feed unit. However, as the experimental results showed a more significant positive partial correlation between the digestible crude fat intake, measured in g/kg live weight (x g), and the relative level of yield Table 3. Coefficients of partial correlation when the relative milk yield (X 4 = milk yield % of normal) is considered as the dependent variable and the level of net energy intake (X 2 = % of the requirements), the level of dig. crude protein intake (X 3 = % of the requirements), the dig. crude fibre intake (X, = g/kg live weight) and the dig. crude fat intake (X 5 = g/Sc. feed unit required and X, = g/kg live weight) as independent variables. Trials I—IX. Normally fertilized cows in normal condition (n = 481). ~ , , , ~ , , , ~ .. , X. = dig. crude X, = dig. crudeX„ = level of net X, = level of X, = dig. crude , ■ . , ,° ~ * i • * ■ „ ... " . . . . , * ... . , fat intake g/fu. fat intake g/kgenergy intake protein intake fibre intake .. . ' " °. ' reg. live weight r, 2 0.4517 r )3 =-0.2809 ru r,.,.., 0.3729 r l:t;2 = +0.0607 r 14;2 *nu o*l9B TiZ °-2479 ru-~ 3 >,,.., -0.3741 r 13;5 =-0.1746 r14;5 r, 2;6 -0.4666 r 13;6 =0.3067 r 14;6 r 12..,, =-0.4180 r, 3;24 =+0.0131 r 14;23 tlrM -0.3460 r 13;25 =+0.0320 r 14;25 r, 2;36 -0.3704 r 13;26 = +0.0286 rMK „ r 12;45 0.3546 r 18;48 0.1574 r,,..,, ~,.„. -0.4342 r, 3;46 (.2719 rl4;3fi 'una 02206 r .3;5C, 0.1153 r i4; M ri«MB " 3977 r i 3;245 =+00343 rM;gBB 1,,...,,. 0.3537 r 13;246 = +0.0384 r ]4;236 r 12;35C =-01922 r 13;a66 =+0.0286 r 14;256 r i->;456 =-02193 r 13;456 =-0.1118 rM;B6B r 12;3450 = -0.1933 r 43;245C " +oo3,>i' r 14;235G +0.2679 rl5 =-0.2962 r, c =+0.0419 +0.1980 r 15;2 -0.1195 r 16;2 -+0.1374 +0.2327 rl5 ! 3 -0.1995 r lg! 3 =+0.1347 +0.2256 rla;4 -0.2593 r 1(, = +0.0379 +0.2674 rl5 ! 6 0.5868 r l6 ' ;5 =+0.5304 +0.2004 rl5 ! 23 =-0.1350 r lg ! 23 =+0.1267 +0.1873 rl5 ! 24 =-0.1002 rIKM =+0.1285 +0.1921 r 1&;M =-0.4486 r 16;25 =+0.4528 +0.2128 rl5!84 =-0.1755 r l6. M =+0.1211 +0.2254 hme 0.5332 r 16;88 +0.5180 1-0.0698 r 15;46 =-(1.5441 r 16;45 =+0.4965 +0.2289 -0.1166 r, 6 '. 234 =+0.1155 +0.1937 r15;23G =-0.4489 r 1(,- =+0.4469 +0.0656 rIS;M6 =-0.4242 rIKMB =+0.4242 +0.0642 r 15;346 =-0.4991 rlfi;34s =+0.5433 +0.0673 0.4172 +0.4167 6 Table 4. Coefficients of partial correlation when the relative milk fat yield (X 4 = milk fat % of normal) is considered as the dependent variable, and the level of net energy intake (X 2 = % of the requirements), the level of dig crude protein intake (X 3 = % of the requirements), the dig. crude fibre intake (X, = g/kg live weight*) and the dig. crude fat intake (X 5 = g/Sc. feed unit required and X, = g/kg live weight) as independent variables. Trials I—IX. Normally fertilized cows in normal condition (n = 481). X 2 = level of net X 3 = level of X, = dig. crude = **■ cr "de , X « = **■ crude energy intake protein intake fibre intake £at lntake S/ fu - »"take g/kg req. live weight rl2 = -0.4905 r l3 = -0.2489 ru r 12;3 =-0.4591 r 13;2 =+0.1585 r1(.., r I2U =-0.4657 r 13;4 =-0.2199 ru;3 r la;s =-0.4023 r 13;5 =-0.1156 r 14;5 r 12;6 =-0.5001 r 13;6 =-0.2634 r14;6 r 12;34 =-0.4464 r 13;24 =-0.1643 r 14;23 r 12;35 =-0.4285 r 13;2- =+0.1975 r 14;25 r 12;36 =-0.4572 r l3;,6 =+0.1364 r I4;2G r 12;45 =-0.3876 r 13;45 =-0.1011 ru;gB r 12;46 =-0.4748 r 13;46 =-0.2324 rM;M r i2;56 ="0.2511 r 13. . (. =-0.0422 ru.M r 12;345 ="0.4194 r 13;245 =-0.1392 >,,.,.,, r 12;346 =-04451 r,3;246 =+0.1440 r 14;236 r 12;356 =-02898 r, 3. 256 =+0.1554 ru;2se r 12;456 ="0.2512 r 13;456 =-0.0425 r ~..,.„. r 12;3456 = -02897 r 13;2456 = +0.1549 ru ;2356 +0.2205 r l5 =-0.3415 r lfi +0.0102 +0.1376 r15;2 -0.1583 rMi =+0.1117 +0.1866 r1 -0.2662 r l6 j3 M).0894 +0.1684 r 15;1 -0.3128 rl6 j4 =+0.0058 +0.2204 r l5 ! 6 = -0.6192 rIKB = +0.5495 +0.1444 r 15;33 -0.1973 r 16;23 =+0.0766 +(11224 r15;24 -0.1454 r 16;24 =+0.1048 +0 1321 rls;2g -0.4795 rmm =+0.4689 +0.1.-.89 r 15;34 -0.2483 rl6 j34 =+0.0772 +0.1812 r 15;36 =-0.5819 r,6 ! 35 =+0.5422 +0.0092 r 15;46 -0.5933 r l6 ! 45 = +0.5305 +0.1265 r 15;234 =-0.1849 r 16;234 =+0.0676 +0.1398 r 15;236 =-0.4840 r ]( ,! 235 =+0.4559 -0.0161 r 15;246 =-0.4653 r lt...,4 - =+0.4568 -0.0114 r 15;341 . -0.5623 rr6;:145 =+0.6252 -0.0088 r 15;234(. -0.4680 -0.4416 Table 5. Coefficients of partial correlation when the actual difference in milk fat yield (X, = difference from normal g/day) is considered as the dependent variable and the level of net energy intake (X 2 = % of the requirements), the level of dig. crude protein intake (X 3 = % of the requirements), the dig. crude fibre intake (X, = g/kg live weight) and the crude fat intake (X 5 = g/Sc. feed unit required and Xs = g/kg live weight) as independent variables. Trials X—XII. Well conditioned normally fertilized cows (n = 155). X 2 = level of net X, = level of X 4 = dig. crude *• = /*.«■ cr "de *• c ™de energy intake protein intake fibre intake fat intake g/fu. fat intake g/kg req. live weight r l2 =-0.4115 r l3 =1)3778 ru r 12;3 =-0.3430 r 13;2 =0.2989 r 14;2 r 12!4 =-0.3217 r l3 ! 4 =-0.3397 rl4 ' ;3 r 12;5 =-0.3498 r 13;5 (12991 r,^ rl2;e =-0.4061 r 13;6 =-0.3901 rM;6 r 12i34 —0.2631 r 13;24 0.2856 r, 4 ..,3 r 12;35 =-0.3136 r l3 . 2. 0.2640 ru;M r 12;36 =-0.3219 r13; ,(. =-0.2999 r 14;26 r 12;45 -0.2793 r 13;45 0 2841 r u;3s r 12;46 ==-0.3313 r 13;46 =-0.3399 r u;B6 r 12;56 =-0.0574 r 13;56 =-0.2184 r,,..,. r 12;34ö = 0.2455 r]3;245 =-0.2510 ru;m r 12;346 =-0.2628 r 13;246 =-0.2740 ru;236 r12;356 = 0.0549 r I3;2W =-0.2176 rUi2M r 12;456 ="0.0900 r 13;456 =-0.2272 rM!BM r 12;3456 =-° O94S rl3; ä4s6=^°-,:J91 rH;235« +0.3926 rl5 ,-0.3012 rlg +0.0773 +0.2950 r15.., =-0.1983 r, 6;g -0.0249 +0.3566 r15;3 -0.1K49 r l6; =+0.1300 +0.3454 r 15;l -0.2309 r [(.., 0.0286 +0.3870 rIK6 -0.5143 r l6 ! 8 =+0.4428 +0.2814 rl5; .,3 -0.1144 r 16;23 =+0.0352 +0.2734 rIKM -0.1625 r l6;.,4 = 0.0886 +0.3060 rIKM -0.3496 rLG ..,:) +0.2949 +0.3329 rIKM = -0.1270 r 1( ... u = +0.0304 +0.3361 r 15;86 -0.4170 rl6. 85 =+0.3989 +0.0869 r15;46 = -0.3761 r 16;45 - +0.3069 +0.2706 ri 5;.>34 = -0.0818 r, 6; .)34 0.0286 +0.2807 -0.2847 r,,...,.,. h0.2646 +O.llll r^g46 =-0.2085 rl6 ! M 5 =+0.1585 +O.lOBO r15;346 = -0.2820 r 16;345 = +0.2559 +0.1330 rl5.,346 = -0.1418 r 16;2345 =+0. 1193 7 than could be explained on the basis of the partial correlation between the stage of yield (days since calving) and the fat content of the food ration, the first-mentioned factor (x g) was treated specially as a separate independent variable. Tables 3 and 4 present results from the effects of different dietary factors on the level of the relative milk and milk fat yields in the short-period feeding tests on cows in normal condition. In these statistics the effect of the level of net energy intake (x 2) appeared slightly negative throughout. In slight protein over-nourishment no detrimental effects on the level of yield appeared in these animals in normal condi- tions. The statistical effect of digestible crude fibre intake (x 4), insomuch as it appeared, was positive. The effect of the digestible crude fat intake again appeared negative as regards the amount in grams. For comparison, Table 5 presents results from a small material from trials X—XII, calculated on the basis of the actual differences in milk yield in well- conditioned cows. These results were very uniform with the results in the previous Tables 3 and 4. However, in the case of wellconditioned obese cows, it should be noted that the excessive intake of protein was statistically in negative partial correla- tion with the level of milk yield. Tables 6 and 7 present corresponding results from the long-period feeding trials carried out at the Department of Animal Husbandry, Agricultural Research Centre. In this material the effects appeared somewhat slighter, but approximately just as significant statistically as in the shortperiod tests mentioned earlier. This indicated Table 6. Coefficients of partial correlation when the relative milk yield (XL = milk % of normal) is considered as the dependent variable and the level of net energy intake (X 2 = % of requirements), the level of dig. crude protein intake (X 3 = % of the requirements), the dig. crude fibre intake (X 4 = g/kg live weight), and the dig. crude fat intake (X 5 = g/Sc. feed unit required and X 8 = g/kg live weight) as independent variables. Trials XII—XXVII. The feeding tests of the Department of Animal Husbandry (n = 1435), X, = level of net X, = level of X, = dig. crude ,*. . .* ~ ,* . . % „ . , 3 . , , *.., . , lat intake g/fu. fat intake g/kgenergy intake protein intake fibre intake ~ • ■_.r req. live weight !,._, +0.0697 r l3 =+0.0333 ru r12;3 = +0.0630 r 13;2 = +0.0146 r 14;2 rlKi +0.0291 r l3 ! 4 =+0.0373 r u;3 r,,. :> =-0.0448 r l3 ! 5 =-0.0568 ru JB r l2;g =+0.0208 r lg;6 =-0.0017 r U;g r,,,, =+0.0193 rlB .M =+0.0303 rl4;gB rlB. 86 =-0.0330 r13;25 =-0.0479 r u;2s ~.,..„; +0.0218 r l3;2g =-0.0064 r u;2g rJ2;45 =-0.0580 r 13;46 =-0.0475 r u;3s r 12.„; -0.0035 r 13;46 =+0.0112 rl4;3g rlg. M =-0.0738 r l3;sg =-0.0717 ru;sg r12;345 -0.0482 r 13;245 =-0.0345 r 14;235 r12;34g ==-0.0062 r 13;24g =+0.0124 r 14;236 r12;356 =-0.0090 r 13;25g =-0.0411 ru;2sg r 1K456 =-0-0872 r 13;45g =-0.0624 rU;35g r 12;3456 = -0.0245 r13;245g = -0.0275 r14;235g +0.2050 rl5 =+0.1580 rl6 =+0.3644 +0.1954 r15;2 =+0.1436 r 16;2 =+0.3610 +0.2056 r 15;3 =+0.1545 rlg;3 =+0.3670 +0.1031 rl5 ! 4 =+0.1144 rlg ! 4 =+0.3230 +0.1742 r15;6 =-0.1822 rlg! 5 =+0.3744 +0.1971 rl5 ! 23 =+0.1430 r]K23 =+0.3635 +0.1096 r ]s. 24 =+0.1107 r16;24 =+0.3266 +0.1731 r l5! 26 =-0.1779 rlg;2s = +0.3743 +0.0982 rIRM =+o.loBB rlg;34 =+0.3243 +0.1746 r l5 : M =-0.1791 rlg;M =+0.3768 +0.1025 r 15;46 =-0.1845 rlg;4s =+0.3512 +0.1044 rl5 ! 234 =+0.1072 rlg ! 234 =+0.3269 +0.1734 rl5! 236 =-0.1761 rlg ! 235 =+0.3761 +0.1144 rIKM6 =-0.1784 rWiU -+0.3527 +0.1034 r l5. 34G =-0.1819 r1g:345 =+0.3527 +0.1061 r15;2346 =-0.1771 r1g;2345 =+0.3533 8 Table 7. Coefficients of partial correlation when the relative milk fat yield (X 4 = milk fat % of normal) is considered as the dependent variable and the level of net energy intake (X 2 = % of the requirements), the level of dig. crude protein intake (X 3 = % of the requirements), the dig. crude fibre intake (X, = g/kg live weight), and the dig. crude fat intake (X 5 = g/Sc. feed unit required and X 6 = g/kg live weight) as independent variables. Trials XIII—XXVII. The feeding tests of the Department of Animal Husbandry (n = 1435), X 2 = level of net X 3 = level of X 4 = dig. crude . c***^ e c ***^e energy intake protein intake fibre intake a *** a e g/ u. a mae g/ g r req. live weight rl2 = +0.0923 r l3 = +0.0444 ru r12;3 = +00833 r i;);2 = +0.0196 r 14;2 r 12;4 +0.0373 r ]3;4 =+0.0498 r 14;3 rl2 '. b +0.0065 r l3! 5 = -0.0248 r l4 ! 5 r 12;6 = +0.0848 r 13;6 = +0.0368 r 14;6 r 12;34 =+00245 r 13;24 =+0.0415 r 14;23 r12;35 =+0.0120 r13;25 =-0.0261 ru;M r 12;36 =+0.0776 r13;26 =+o.olBl r14;26 r 12;45 =-00198 r 13;45 =-0.0047 r 14;35 rI2U6 =+00470 r 13;46 =+0.0577 r14;36 r 12;56 =+0.0503 r13;86 =-0.0044 ru;66 r 12;345 =-0.0187 r13;245 =+o.oool r 14;235 rl2;:i4G -+0.0350 r13;246 : +0.0488 r 14;236 r 12;356 =+ooslo r 13;256 =-0.0151 r14;25G r 12;456 -+0.0241 r 13;45e =+0.0179 r 14;356 r 12;3456 = +OOl9B r 13;2456 =+0.0123 r 14;2856 +0.2775 r la =+0.0407 rl6 = +0.2879 +0.2649 r 15;2 =+0.0119 r16;2 =+0.2735 +0.2784 r 15;3 =+0.0317 rl6;g =+0.2850 +0.2121 r 15;4 =-0.0274 rl6 ! 4 =+0.2164 +0.2793 rl5 ! 6 =-0.2792 r 16;5 =+0.3908 +0.2673 rIKM = +0.0091 r 16;23 = +0.2740 +0.2066 rls;ä4 =-0.0403 r lg ! 24 =+0.2178 +0.2674 r 15;26 =-0.2753 r ]6;25 =+0.3806 +0.2048 r l5 ! 34 =-0.0408 r |g ! 34 =+0.2140 +0.2795 r l5 : 3G 0.2700 H1.3540 +0.2240 r16;46 =-0.2885 r16;45 =+0.3437 +0.2051 . 1ä;234 = -0.0479 r16;234 = +0.2140 +0.2711 rl5. 2g6 =-0.2745 i"1U; 235 -10.3803 +0.2134 =-0.2803 r 1K246 = +0.3474 +0.2183 r 15;346 =-0.2806 r 16;345 = +0.3462 +0.2057 r 15;2346 = -0.2804 rieaMß = +0.3447 some kind of adaptation to feeding in the long-period tests. Detrimental effects from an excessive intake of energy and protein could not be observed in these statis- tics. However, it should be noted that in this series of tests the excesses were rela- tively slight even in the most extreme cases (level of net energy intake 75—135 % and level of protein intake 65—170 % of the standards) and, on the other hand, under-nourishment could also be a limiting factor on the yield in certain cases. A rise in the level of yield was not obtained by heavier feeding, however, even under these circumstances. Discussion The statistical results obtained seem to indicate that the excessive intake of energy in the experiments described has had only some unmeasurable or negative effects on the level of milk and milk fat yields. In this respect the results are uni- form with results obtained in Norway and Denmark using other experimental me- thods (1,6). In the negative cases the effect of over-nourishment seems to appear somewhat more clearly in the level of milk and milk fat yields than in the blood plasma cholesterol content (5). This specifically indicates strain effects. The effects of excessive intake of protein seem to be similar in the level of plasma cholesterol and in the level of milk and milk fat yields. Increasing the proportion of digestible crude fibre in the food ration seems in certain cases to raise the level of milk and milk 9 fat yields somewhat. This rise does not, however, entirely correspond to a simulta- neous rise in the level of blood plasma cholesterol. The negative results obtained with the relative values of the digestible crude fat intake, calculated per feed unit, and the positive results with the simultaneous values in grams indicate that the amount of fat required by a dairy cow in its food varies during the different stages of yield. Thus the optimal level of digestible crude fat intake for the average stage of yield can be insufficient in stages of heavy milk yield, and again detrimentally large in stages of small yields. Summary and Conclusions The following results have been obtained from a statistical investigation carried out on experimental results from 27 feeding trials in which the effect of cholestero- genic dietary factors, observed in an earlier investigation (5), on the relative levels of milk and milk fat yields are compared. An execessive intake of energy either has no statistically clear effect on the level of yield, or the effect is negative. In this respect the results obtained are uniform with experimental results obtained in Norway and Denmark using other methods (1, 6). In the negative cases the effect appears more clearly in the level of milk and milk fat yields than in the plasma cholesterol content. An excessive intake of protein shows a negative effect only in well-conditioned obese cows. An increase of the proportion of digestible crude fibre in the foodration appears in most cases to have an increasing effect on the milk yield. This effect, however, seems to be slighter than the effect on the blood plasma cholesterol content. The level of milk and milk fat yields has proved to be statistically in positive partial correlation to the digestible crude fat intake in g/kg live weight ,and in nega- tive partial correlation to the relative fat intake compared with the nutritional requirements of the animal. This indicates that the favourable level of fat intake varies according to the level of milk yield, being larger in stages of higher yields than in stages of small yields. REFERENCES (1) Hvidsten, H, 1951. Kraftforforbruk og forstyrke i mjolkeproduksjonen. Buskap og Avdratt, 3, p. 3—7. (2) Jutila, Vappu 1956. Aivolisäkkeen etulohkon ja lisämunuaisen kuorikerroksen toimintoihin liitty- vistä rasitusilmiöistä kotieläimillä. Masters thesis. (3) Lönnberg, Githa 1954. Om inverkan av fodrets fett och protein pä blodets kolesterol och urinens 17-ketosteroidhalt. Laudaturbeskrivning. (4) Saarinen, P. 1944. Lehmän veriplasman lipoidiaineosien vaikutuksesta maitorasvan muodostuk- seen. Rcf. Cbcr den Einfluss einiger Lipoidbestandteile im Blutplasma der Kuh auf die Milchfetterzeugung. Acta Agralia Fennica, 57. 2, p. I—l3l.1 —131. 10 (5) Saarinen, 1955. Diet and plasma cholesterol in dairy cows. Maataloustieteellinen Aikakauskirja (J. Sei. Agr. Soc. Finland), 27, p. 117—141. (6) Wenzel Eskedal, H. & Hansen, K. 1951. Forsog med fodringens indflydelse pä kaernes holdbar- hed. Oversigt. Forsogslaboratoriet 1950—1951. Ref.: Problems of animal feeding in Europe, p. 67—99, Published by FAO and EAAP, Rome 1955. SELOSTUS: KOLESTEROGENISEN RAVINNON VAIKUTUS MAIDON JA MAITORASVAN TUOTOKSEEN Pellervo Saarinen Helsingin yliopiston kotieläintieteen laitos. Kun 27 ruokintakokeesta saadun köetulosmateriaalin nojalla suoritettiin tilastollinen tutkimus, jossa verrattiin aikaisemmassa tutkimuksessa (5) kolesterogenisiksi havaittujen dieettisten tekijöiden vaikutusta lypsylehmien suhteelliseen maidon ja maitorasvan tuotostasoon, niin saatiin seuraavat tulok- set. Energiayliruokinnalla ei ole ollut joko mitään tilastollisesti selvää vaikutusta tuotostasoon tai tämä vaikutus on ollut negatiivinen. Tässä suhteessa saatu tulos on yhdenmukainen Norjassa ja Tans- kassa muilla menetelmillä saatujen koetulosten kanssa (1, 6). Negatiivisissa tapauksissa vaikutus on esiintynyt maidon ja maitorasvan tuotostasossa selvempänä kuin plasman kolesterolipitoisuudessa. Valkuaisyliruokinnalla ilmeni negatiivista vaikutusta vain voimakkaasti kunnostetuilla lehmillä. Sulavan raakakuidun osuuden lisäämisellä rehuannoksessa näytti useimmissa tapauksissa olevan maidon tuotosta lisäävä vaikutus. Tämä vaikutus näyttää kuitenkin ilmenevän lievempänä kuin vas- taava vaikutus plasman kolesterolipitoisuuteen. Sulavan raakarasvan määrä rehuannoksessa grammoissa elopainokiloa kohden mitattuna on osoit- tautunut olevan tilastollisesti positiivisessa vuorosuhteessa ja eläinten ravinnontarpeeseen verrattu suhteellinen raakarasvan määrä taas negatiivisessa vuorosuhteessa maidon ja maitorasvan tuotosta- soon. Tämä viittaa siihen, että edullisin rasvan määrä rehussa vaihtelee tuotoksen määrästä riip- puen, ollen se suurempi runsaan tuotannon kuin vähäisen tuotanon vaiheessa.