The estimation of the energy value of liveweight change in the lactating dairy cow

Livestock Production Science, 9 (1982) 665--673

665

Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

THE ESTIMATION OF THE E N E R G Y V A L U E OF LIVEWEIGHT CHANGE IN THE LACTATING D A I R Y COW

G. ALDERMAN

MAFF/ADAS, Great Westminster House, Horse ferry Road, London (Gt. Britain) W.H. BROSTER

National Institute for Research in Dairying, Shinfield, Reading (Gt. Britain) M.J. STRICKLAND

Boxworth Experimental Husbandry Farm, Elsworth, Cambridgeshire (Gt. Britain) C.L. JOHNSON

Leeds University, Department of Animal Physiology and Nutrition, Leeds (Gt. Britain) (Accepted 20 April 1982)

ABSTRACT Alderman, G., Broster, W.H., Strickland, M.J. and Johnson, C.L., 1982. The estimation of the energy value of liveweight change in the lactating dairy cow. Livest. Prod. Sci., 9: 665--673 Nine feeding experiments with dairy cows have been combined to assess liveweight change and its energy value at two stages of lactation. All animals were individually fed. Records of group average food intakes, milk yields and composition, and liveweights were available. Mean metabollsable energy (ME) intakes were calculated and estimates of energy balance (EB) derived by difference between ME intake and the ME requirement for maintenance and milk production according to the Ministry of Agriculture, Food and Fisheries (MAFF), Mean EB was regressed on mean liveweight change (AW) and highly significant (P < 0.01) relationships found for heifers and cows in Weeks 1--10 of the lactation, the regression coefficients being 49.1 and 31.3 MJ ME/kg AW for heifers and cows, respectively. The data could be pooled to give a coefficient of 39.5 ± 11.0 MJ ME/kg liveweight loss. This can be compared to the MAFF allowance of 28 MJ ME/kg (based on a net energy value of 20 MJ/kg liveweight change) and to the Agricultural Research Council (ARC) value of 34 MJ ME/kg liveweight change based on 26 MJ net energy/kg liveweight change. In mid lactation, when mean AW was small and positive, no significant relationship was found for heifers, b u t for cows a significant relationship (p < 0.05) was found with a coefficient of 89.1 MJ ME/kg.

INTRODUCTION

The cow divides her food, maintenance needs apart, between milk and body. To ration the cow adequately, attention must be given to exchanges of

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© 1982 Elsevier Scientific Publishing Company

666

b o d y energy. In the first instance it is necessary to know the l iveweight of the c o w to assess maintenance needs; secondly changes in liveweight can assist in the judgement of the adequacy of feeding, and in guiding the pattern of feeding. An estimation of the pattern of liveweight change and of the energy value of that liveweight change is required. MA T ER I ALS AND METHODS

In this study nine published experiments (Table I) all of the same type involving in total some five hundred cows have been combined to allow an assessment of weight change at t w o stages of the lactation for first calf and for older cows and to provide an assessment of the energy value of that weight change. TABLE I General details of the experiments Source

Broster et al. (1958) Broster and Tuck (1967) Broster et al. (1969) Broster et al. (1975) Johnson (1977) Johnson (1977) Johnson (1979) Broster et al. (1978, and unpublished) Strickland and Broster (1981) Strickland and Broster (1981) a b c d e f

No. of replicates e

No. of levels of intake

Parity

Post-calving Order o f liveweight milk yield (kg) kg/day

22

2c

1

476

15

10

Ib

1

489

18

20

2b

1

545

22

16 8 16 10 9 4 4

3b 3a 3a 2d 3b 3b 3b

1 2 3f 3f 1 2 3f

540 486 562 535 530 560 550

22 20 20 28 19 23 23

12

3a

1

472

15

15

3a

3f

566

18

Two fixed levels plus one treatment with the feeding in proportion to the yield (Woodman, 1957). Fixed amounts per day at each level; Broster et al. (1978) also had an ad libitum treatment. Two rates o f feeding per litre of milk produced. Divided into two groups according to yield potential; fixed amounts/day. Friesian cows save for Broster et al. (1958) who had groups of Friesian and of Shorthorn cows. Third or later parity.

667

Experimental evidence All the experiments included as treatments variation in the a m o u n t of concentrate (compound feed consisting of cereal grain and oil cake residues) fed in addition to fixed allowances of forages (hay, silage) and in one instance sugar beet pulp. Table I gives details of these variations. Cows were fed individually; all feeds were weighed; milk records were taken daily; milk samples at least twice m o n t h l y ; liveweights at least once weekly. All trials were conducted in the first 20 weeks of lactation; various parities were involved.

Method o f analysis The mean values per treatment group for all the experiments were assembled according to parity of cows. Separate analyses were used for heifers and for older cows. The energy balance was computed using the following procedures.

Calculation o f metabolisable energy intakes The metabolisable energy (ME) values for individual feeds used in each set of experiments were derived from the tables of feed composition in Technical Bulletin 33 of the Ministry of Agriculture, Fisheries and Food (MAFF, 1975) for foods such as cereals and dried sugar beet pulp. In the case of forages, ME values were predicted from chemical composition, using appropriate regression equations (numbers 61--75) on pp. 66 and 67 of the same Bulletin. From the recorded intakes of dry m a t t e r for each ration constituent, mean total ME intakes per day (MEI) for each treatment group were calculated.

Calculation o f energy balance based on M A F F (1975) equations The recorded mean liveweight (W) for each treatment group was used to calculate the maintenance ME requirement (Mm) using M m (MJ/day) = 8.3 + 0.091 W Adjustments for the energy c o n t e n t of milk (EVI) were made using EV 1 (MJ kg -1) = 0.0386 BF + 0.0205 SNF - 0.236 where BF = butterfat c o n t e n t g/kg; SNF = solids n o t fat c o n t e n t g/kg. The ME required for milk production (Ml) was calculated as M 1 = 1.694 EV 1 which assumes an efficiency of 0.62, b u t includes a 5% safety margin as does the maintenance calculation.

Energy balance (EB) was then calculated by deducting maintenance milk production needs from calculated ME intake per day EB (MJ/day)

and

= ME1 - Mm - Ml

The energy balance (EB), calculated as ME intake per day in excess of Mm and M, , was regressed on liveweight change (AW). In order to convert this to the net energy of tissue gain or loss, the relevant efficiency factors must be used (MAFF, 1975). Limitations of the calculations The ME values of the feeds were estimated not measured; this, plus the indirect method of estimating energy utilisation, increases the errors in values for energy balance (EB). Liveweight change was indeed measured, but suffers from possible bias due to variation in gut fill (ARC, 1965,198O) especially in early lactation. ARC (1980) gave a multiplier constant (1.09) for conversion of empty body gain to liveweight gain. This does not confer any advantage in the present analysis and has not been applied. Liveweight change, as the measured variate, has been preferred as the independent variate in the regression analysis to be presented. The analysis is also based on unweighted mean values per treatment group. COMPARISON OF RECORDED AND RECOMMENDED LIVEWEIGHT CHANGE

The mean liveweight change (AW) recorded for heifers and cows in early and mid lactation and the corresponding energy balances are shown in Table II. TABLE

II

Regression of energy balance (expressed in ME) upon liveweight change

Heifers A. Early lactation B. Mid lactation Pooled A+B

Linear regression of EB on AW

Energy balance (MJ ME/day)

Liveweight change @g/day)

Range

Mean

Range

Mean

Coefficient (b)

19 to -43

-14

0.02 to -0.76

-0.38

49.1**

26 to -17

-3

0.65 to

25to-43

-9

0.66 to -0.76

-0.17

-19 to -49

-29

0.12to

-0.49

to

+13

0.26 to -0.19

0.18

0.10 27.4t

constant (a)

f 13.19

r=

4.3NS f 5.86 0.50

Error degrees of freedom

14

f 16.94

- 6.SNS

f 3.80 0.19

11

41.0**

f 14.69

- 3.0NS f 2.68 0.42

25

31.3**

f

-13.3*

cows Early lactation Mid lactation ** * t NS

47

P < 0.01.

P < 0.05. P
-14

-1.04

0.08 89.1*

8.68

f 36.3

f 6.16 0.66

7

2.1NS f 6.22 0.48

7

669 In agreement with many feeding trials and with practical evidence (e.g., Wood et al., 1980) the data presented in Table II indicate a loss in liveweight in early lactation and stability of weight or small gains for the next two months. This agrees with the norms for liveweight change for this stage of lactation proposed by M A F F (1975). Exceptions to this finding exist, as for instance the experiment by J o h n s o n (1979) in the present group of trials. In that study cows lost very little weight in early lactation and by Week 20 had regained their initial post-calving liveweight. This experiment is n o t included in Table II. The weight of evidence indicates that at present the counsel of perfection to avoid b o d y loss and the tacit assumption in some instances that such losses do n o t occur cannot be accepted though clearly rigorous examination and pursuit of the implications of Johnson's (1979) study is merited. The M A F F {1975) estimates of liveweight losses thus represent a good initial approximation to the actual changes of weight. To account for such losses in rationing schemes is realistic, b u t such acknowledgement should n o t be regarded as systematic deliberate under-feeding of cows to induce weight losses or a failure to appreciate the ultimate target in efficiency of energy utilisation of avoiding these losses. The inclusion of protected lipids in the diet of cows in early lactation offers a possible solution to the problem. A difficulty in early lactation is the low voluntary intake the cow exhibits (Bines, 1979). Lodge et al. (1974) have demonstrated that thin cows eat more than fat cows at this time. Such cows will be at risk, however, in that the total yield of milk in the lactation may be reduced consequent u p o n their poor b o d y condition (Broster, 1971; F r o o d and Croxton, 1978). B o d y score systems may calibrate this relationship eventually (Frood and Croxton, 1978). The changes in liveweight after calving are complex: changes can be induced by ration and consequent gut fill effects (ARC, 1965, 1980); alteration in body water c o n t e n t can also occur, and this does n o t represent any change of body net energy. These questions have been expanded u p o n b y Moe et al. (1971), van Es and van der Honing (1979). RELATIONSHIP B E T W E E N E N E R G Y B A L A N C E A N D L I V E W E I G H T C H A N G E

If energy balance is positive, b o d y tissue net energy will be deposited with an efficiency of 0.62. B o d y tissue is used for milk secretion with an efficiency of 0.82. These values lead to an overall efficiency of use of ME of 0.51 for milk production when b o d y reserves deposition and mobilisation are involved. Since milk is produced from ME with a mean efficiency of 0.62, 1 MJ of negative energy balance calculated as ME is equivalent to 0.76 MJ of net energy coming from b o d y tissue loss. The problem of the energy c o n t e n t of weight changes in the dairy cow remains unresolved. Classical calorimetric experimentation (Flatt et al., 1969) illustrates the extent of withdrawal of b o d y reserves. MAFF (1975) indicated b y implication from the data quoted above losses of 17 and 0 MJ/day for early and mid lactation periods, based on a net energy value of 20 MJ/kg liveweight gain equivalent to 28 MJ ME/kg liveweight loss.

670

ARC (1980) r e c o m m e n d e d as an interim measure " 2 6 MJ net energy/kg weight change consisting of 150 g protein and 550 g fat". Separate evaluations for b o d y loss and gain are n o t currently possible. Also even the ARC (1980) estimates do n o t apply specifically to Weeks 0--6 of lactation. Wood et al. (1980) concluded that 10% of the metabolisable energy needs in early lactation are derived from b o d y tissue mobilisation, or 20--25 MJ ME. Van der Honing et al. (1977) studied the relationship between energy balance and liveweight change in dairy cows using feed intake and production data from trials published by Frederiksen (1931) and b y Dijkstra (Anonymous, 1971). These data concerned the period from Week 8 to Week 18 of lactation, i.e., the mid lactation phase in the present study. Correlations of 0.48 and 0.37 were found between these two factors for the Frederiksen (1931) and A n o n y m o u s (1971) data, respectively, leading to a pooled value of 0.41. The regression coefficient of energy balance on AW averaged 50 MJ/kg in net energy (lactation) terms. Values for individual experiments varied widely, however, as van der Honing et al. (1977) discussed. This value would equal 66 MJ/kg in metabolisable energy terms. From the mean values per group for liveweight change and energy balance in Table II the overaU unweighted mean for 1 kg liveweight change is equivalent to 47.8 MJ of ME. For heifers and cows separately the ME values were 60.7 and 39.0 MJ respectively/kg liveweight; and for early and mid lactation they were 49.4 and 55.5 MJ ME/kg liveweight, respectively. The results of the regression analysis of energy balance (EB, MJ/day) on liveweight change (AW, kg/day) for heifers and cows in early and mid lactation are also shown in Table II. Regression calculations based on logarithms of the variates or made to pass through the origin did n o t alter materially the values obtained. For heifers a highly significant relationship (P < 0.01) was found in early lactation between energy balance (EB) and liveweight change (AW). One kg liveweight change equalled 49 MJ of ME (i.e., the slope of the regression line of EB on AW). The intercept value indicates the animals were in energy balance at 0.09 kg loss of liveweight. This may reflect the intercept being non-significantly different from zero or an indication of an energy need for growth n o t allowed for in the calculated EB. In mid lactation the regression coefficient was only significant at 10% probability, the slope indicating 1 kg liveweight change to be equivalent to 27 MJ ME. The higher estimated EB value per kg AW in early lactation may be attributable to the high energy value of b o d y fat (40 MJ/kg) which would be mobilized shortly after calving, b u t may also reflect an under-estimation of true b o d y weight loss in early lactation, due to increase in gut contents between Weeks 1 and 10. The slope of EB on AW is less consistent for cows than heifers between early and mid lactation. In early lactation, a highly significant relationship was found (P <= 0.01) and 31 MJ of ME/kg liveweight loss is implied, close to the M A F F (1975) value of 28 MJ/kg. For cows in early lactation AW = 0.42 kg for EB = 0, a larger value than that recorded above for heifers. In mid lactation the

671

relationship is not as strong, and a value of 89 MJ per 1 kg AW is implied, which is difficult to explain in physiological terms. It would equate with the deposition of 1.7 kg fat and the concomitant loss of 0.7 kg water. The regressions of b o d y energy exchange estimates (Y) on liveweight change (X) were tested for parallelism and coincidence (Snedecor and Cochran, 1967). For heifers the information for early and mid lactation could be combined giving Y = 4 1 . 0 5 X : 2.95. Pooling was acceptable for cows and heifers in early lactation so far as slope of the regressions were concerned giving a b value of 39.52 + 10.998, b u t they were n o t coincident. The data for early and mid lactation for cows could n o t be pooled. Thus the three regressions, for heifers in early and mid lactation and for cows in early lactation, gave an energy value of 40 MJ metabolisable energy/kg AW with intercepts approaching zero for heifers, b u t n o t cows. With a conversion factor to net energy of 0.76 this gives an energy value of the tissues of 30 MJ, slightly higher than the value cited by ARC (1980) of 26 MJ/kg. ACKNOWLEDGEMENT

The assistance of Mr. A. Eggert in the computations is gratefully acknowledged.

REFERENCES Agricultural Research Council (ARC), 1965. Nutrient Requirements of Farm Livestock. No. 2. Ruminants. Technical Reviews and Summaries. Her Majesty's Stationery Office, London, 264 pp. Agricultural Research Council, 1980. The Nutrient Requirements of Ruminant Livestock. Technical Review by an Agricultural Research Council Working Party. Commonwealth Agricultural Bureaux, Farnham Royal, Slough, 351 pp. Anonymous, 1971. Lijstvan publikaties van Dr. N.D. Dijkstra. Landbouwkd. Tijdschr., 83: 309. Bines, J.A., 1979. Voluntary Food Intake. In: W.H. Broster and H. Swan (Editors), Feeding Strategy for the High Yielding Dairy Cow. Granada, St Albans, pp. 23--40. Broster, W.H., 1971. The effect on milk yield of the cow of the level of feeding before calving. Dairy Sci. Abstr., 33: 253--270. Broster, W.H. and Tuck, V.J., 1967. Experiments on the nutrition of the dairy heifer. VI. The effect on milk production of the level of feeding during the lastsix months of pregnancy and the firsteight weeks of lactation. J. Agric. Sci., 69: 465--477. Broster, W.H., Ridler, B. and Foot, A.S., 1958. Levels of feeding of concentrates for dairy heifers before and after calving. J. Dairy Res., 25: 373--382. Broster, W.H., Broster, V.J. and Smith, T., 1969. Experiments on the nutrition of the dairy heifer. VIII. Effect on milk production of level of feeding at two stages of the lactation. J. Agric. Sci., 72: 229--245. Broster, W.H., Broster, V.J., Smith, T. and Siviter, J.W., 1975. Experiments on the nutrition of the dairy heifer. IX. F o o d utilization in lactation. J. Agric. Sci., 84: 173--186. Broster, W.H., Sutton, J.D. and Bines, J.A., 1978. Concentrate :forage ratios for highyielding dairy cows. In: W. Haresign and D. Lewis (Editors), Recent Advances in Ruminant Nutrition. Butterworth, London, pp. 99--126.

672 Flatt, W.P., Moe, P.W., Munson, A.W. and Cooper, T., 1969. Energy utilisationby high producing dairy cows. II. S u m m a r y of energy balance experiments with lactating Holstein cows. In: K.L. Blaxter, J. Kielanowski and G. Thorbeck (Editors), Energy Metabolism of Farm Animals. Oriel Press, Newcastle-upon-Tyne, pp. 235--251. Frederiksen, L., 1931. Varierede foder-og proteinmaengder tilmaelke produktion. 136 Beretning Fr~i Fors~bgsiab,K~bbenhavn. Frood, M.J. and Croxton, D., 1978. The use of condition scoring in dairy cows and its relationship with milk yield and liveweight. Anim. Prod., 27 : 285--291. Johnson, C.L., 1977. The effect of the plane and the pattern of concentrate feeding on milk yield and composition in dairy cows. J. Agric. Sci., 88: 79--94. Johnson, C.L., 1979. The effect of level and frequency of concentrate feeding on the performance of dairy cows of different yield potential. J. Agric. Sci., 92: 743--751. Lodge, G.A., Fisher, L.J. and Lessard, J.R., 1974. Influence of prepartum feed intake on performance of cows fed ad libitum during lactation. J. Dairy Sci., 58: 696--702. Ministry of Agriculture, Fisheries and Food, Department of Agriculture and Fisheries for Scotland, Department of Agriculture for Northern Ireland (MAFF), 1975. Energy Allowances and Feeding Systems for Ruminants. Technical Bulletin 33. Her Majesty's Stationery Office, London, 79 pp. Moe, P.W., Tyrrell, H.F. and Flatt, W.P., 1971. Energetics of body tissue mobilisation. J. Dairy Sci., 54: 548--553. Snedecor, G.W. and Cochran, W.G., 1967. Statistical Methods, 6th edn. The Iowa State University Press, Ames, IA, 593 pp. Strickland, M.J. and Broster, W.H., 1981. The effect of different levels of nutrition at two stages of the lactation on milk production and liveweight change in Friesian cows and heifers. J. Agric. Sci., 96: 677--690. Van der Honing, Y., Steg, A. and Van Es, A.J.H., 1977. Feed evaluation for dairy cows: tests on the system proposed in The Netherlands. Livest. Prod. Sci., 4: 57--67. Van Es, A.J.H. and van der Honing, Y., 1979. Energy utilisation. In: W.H. Broster and H. Swan (Editors), Feeding Strategy for the High Yielding Dairy Cow. Granada, St Albans, pp. 68--89. Wood, P.D.P., King, J.O.L., Youdan, P.G., 1980. Relationships between size, liveweight change and milk production characters in early lactation in dairy cattle. Anim. Prod., 31 : 143--151. Woodman, H.E., 1957. Rations for livestock. Bulletin 48 Ministry of Agriculture, Fisheries and Food. Her Majesty's Stationery Office, London, 134 pp. RESUME Alderman, G., Broster, W.H., Strickland, M.J. et Johnson, C.L., 1982. L'estimation de la valeur ~nerg~tique des variations de poids vif chez la vache laiti~reen lactation.Livest. Prod. Sci., 9:665--673 (en anglais) O n a rassembl~ neuf eassais d'alimentation stirdes vaches laiti~resafin d '~valuerles variations de poids vif et leur valeur ~nerg~tique ~ deux stades de lactation. Toutes les vaches avaient ~t~ aliment~es individuellement. O n disposait des quantit~s d'aliment consomm~es, de la quantitd et de la composition du laitproduit et des poids des animaux. O n a calcul~ l'~nergiem~tabolisable (EM) ing~r~e et estim~ le bilan ~nerg~tique (EB) par la difference entre I'EM ingdr~e et les besoins en E M pour l'entretienet la production laiti~reproposes par le M A F F . En calculant la r~gression du bilan ~nerg~tique m o y e n en fonction du changement de poids vif m o y e n (AW) on a obtenu une relation tr~s significative(P < 0,01) pour les g~nisses et les vaches durant les semaines 1 ~ 10 de la lactation,les coefficients de r~gression ~tant de 49,1 M J de ME/kg A W pour les g~nisses et de 31,3 pour les vaches. Les

673 donn~es ont pu $tre regroup~es, avec u n coefficient de 39,5 MJ d'EM/kg de perte de poids vif, qui peut ~tre cornpar~ aux valeurs de 28 et de 34 p r o p o s e s , respectivernent, par le MAFF et I'ARC sur la base de 20 et 26 MJ d'~nergie nette par kg de variation de poids vif. Au milieu de la lactation, lorsque la variation de poids vif ~tait faible et positive, on a observ~ une relation significative chez les vaches, avec u n coefficient de 89,1 MJ d'EM/kg, rnais pas chez les g~nisses.

KURZFASSUNG Alderman, G., Broster, W.H., Strickland, M.J. und Johnson, C.L., 1982. Die Sch~/tzung des Energiewertes der Lebendgewichtver~/nderung bei der laktierenden Milchkuh. Livest. Prod. Sci., 9 : 665--673 (auf englisch). Neun Ftitterungsversuche mit Milchvieh wurden miteinander verbunden um die Lebendgewichtveriinderung und ihren Energiewert w~ihrend zweier Laktationsstadien zu bewerten. Alle Tiere wurden einzeln geftittert. Daten tiber die Futteraufnahrne, die Milchleistung und -~usarnmensetzung sowie tiber das Lebendgewicht standen zur Verftigung. Die durchschnittliche Aufnahrne an umsetzbarer Energie (ME) wurden berechnet, und die Sch~itzwerte ftir das Energiegleichgewicht (EB) ergaben sich aus der Differenz zwischen ME-Aufnahme und dern ME-Bedarf fiir Erhaltung und Milchproduktion gern~ss Ministry of Agriculture Food and Fisheries (MAFF). Die durchschnittliche EB wurde auf die rnittlere Lebendgewichtver~/nderung (AW) regressiert, wobei ftir die Laktationswochen 1--10 hochgesicherte Beziehungen (P < 0,01) ftir F~rsen und Ktihe gefunden wurden; die Regressionskoeffizienten ftir F~rsen und Ktihe waren 49,1 bzw. 31,3 MJ ME/kg AW. Die Daten k 6 n n t e n zusamrnengefasst werden, urn auf diese Weise einen Koeffizienten von 39,5 +- 11,0 MJ ME/kg Lebendgewichtverlust zu ergeben. Dies ist vergleichbar rnit dem Weft yon MAFF yon 28 MJ ME/kg, der auf einern Nettoenergiewert yon 20 MJ/kg Lebendgewichtver'~nderung basiert. Der ARC (Landwirtschaftlicher Forschungsrat) 1980 hat diesen Wert auf 26 MJ/kg gesenkt; dies entspricht 34 MJ ME/kg AW und stirnmt in etwa rnit den zusarnrnengelegten Werten ftir F~rsen und Ktihe tiberein. Nach der H~ilfte der Laktation, als die rnittlere AW gering und positiv war, wurde fiir F~irsen keine gesicherte Beziehung, ftir Ktihe jedoch eine gesicherte Beziehung (P < 0,05) rnit einern Koeffizienten von 89,1 MJ ME/kg gefunden.