Standard and lead feeding of dairy cows

Livestock Production Science, 10 (1983) 443--455

443

Elsevier Science Publishers B.V., Amsterdam--Printed in The Netherlands

STANDARD AND LEAD FEEDING OF DAIRY COWS

A. EKERN and L. VIK-MO

Department of Animal Nutrition, Agricultural University of Norway, P.O. Box 25, 1432 ,~s-NLH (Norway) (Accepted 22 March 1983)

ABSTRACT

Ekern, A. and VikoMo, L., 1983. Standard and lead feeding of dairy cows. Livest.Prod. Sci., 10: 443--455. Standard feeding means that the a m o u n t of feed offered is regulated according to actual requirement, with special reference to energy. Lead feeding indicates liberal supply during early lactation in order to challenge the cows for high peak yield. The lead feeding, in contrast to standard feeding rigidly practised, allows the cow to express its yield potential during the critical period of early lactation. Adjusted standard feeding may, however, be practised in a more flexible way by ad libitum feeding of forages, lead feeding during early lactation and with individual rationing of concentrates throughout. Adjusted standard feeding requires individual recordings of milk yield at intervals and qualitative judgement of the roughage available. Such a system is described and discussed. Adjusted standard feeding, flexibly practised seems most applicable for the small farm situation. By using a computerized system for diet calculation combined with adequate techniques for individual milk recordings and concentrate feeding, the system may be feasible even for larger herds. Adjusted standard feeding, as described, stresses the significance of high forage consumption together with efficient use of concentrates, high efficiency overall, and positive effect on ketosis and infertility.

INTRODUCTION

Energy requirements and standards for dairy cows are based on balance studies and feeding trials carried o u t under more practical conditions (Flatt et al., 1972; van Es and van der Honing, 1979). The standards m a y be expressed in terms of megajoules metabolizable energy or in various terms of net energy, e.g., Net Energy Lactation, Starch Equivalent, Feed Units (FU), etc. "Standard feeding" means that the a m o u n t of feed offered is regulated according to actual requirements for maintenance, pregnancy and lactation with special reference t o energy. Rigidly applied the system suggests feed allocation based on recorded, i.e., past performance. In this way 0301-6226/83/$03.00

© 1983 Elsevier Science Publishers B.V.

444 standard feeding would not allow the individual cow to regulate her own intake, except by not consuming all the feed given. Today standard feeding may be practised in a more flexible way by ad libitum feeding of forages combined with individual rationing of concentrates. Rather than feeding according to production, the principle of "lead feeding" indicates liberal feed supply particularly during early lactation in order to challenge the cow into high lactation performance. The lead feeding thus allows for expression of yield potential. Especially lead feeding has merits during the critical, ascending part of lactation. Thus, lead feeding may precede standard feeding, whether rigidly or flexibly applied. A more flexible and applicable system is that of combining "lead feeding" during early lactation with flexibly practised "standard feeding" during mid and late lactation, including ad libitum forage feeding, but with individual concentrate rationing throughout. Such a system is described here and termed "adjusted standard feeding". ASSUMPTIONS CONCERNING FEED ENERGY ALLOCATION

Milk yield and intake capacity The gestation--lactation cycle approach by Lenkeit et al. (1956) indicates a cyclic pattern of nutrients being retained during late pregnancy and the dry period followed by mobilization during early lactation. The significance of such a cyclic pattern is well recognized and should be taken into account when devising feeding systems for dairy cows. Sufficient energy supply during the dry period seems vital for the development of the mammary gland (Smith et al., 1967) and may be needed to restore body reserves. The need for body reserves is emphasized by a more rapid increase in yield than in intake capacity after calving. At this stage in high yielding cows intake of energy, for a while, cannot keep pace with milk energy output. During later parts of the lactation the capacity for intake exceeds current yield ability, and feeding should be regulated for optimal production.

Forage intake Forage as well as total feed intake is generally influenced by animal, dietary and environmental factors (Bines, 1976; Ekern and Macleod, 1978). Thus, the intake of forage in dairy cows may be low immediately after calving with a gradual increase during early lactation. Under practical feeding conditions it is shown that maximum forage intake is reached somewhat later than peak milk yield and thereafter either stabflises or slightly decreases (Ekern, 1972; Grieve et al., 1976; Journet and Remond, 1976; Ostergaard, 1979). It has been clearly demonstrated that concentrate feeding improves

445 TABLE I Substitution rates at various stages of lactation when cows are given concentrates according to yield (Ekern, 1972) Week o f lactation

3--6

7--12 13--18 19--26

Substitution rate: Decline in forage DM per kg extra concentrate DM Experiment 1

0.95

0.70

0.58

0.31

Experiment 2

0.91

0.76

0.48

0.36

total energy intake. If the c o w is given forage ad libitum, however, she m a y substitute concentrates for forage. Such substitution rates seem to be greater for high than for low quality forages (Blaxter and Wilson, 1963) and greater during early than during mid and late lactation (McCaffree and Merrill, 1968; Ekern, 1972; J o u r n e t and Remond, 1976). Other factors such as conservation methods (Wilkins et al., 1976), t y p e of concentrates (Osbourne et al., 1976) and level of concentrate feeding (0stergaard, 1979) m a y also affect substitution rate. The substitution of forage for concentrates may have important practical consequences because the response in total energy intake of the c o w is less than that of additional energy supplied from concentrates. This effect is particularly evident during early lactation as demonstrated in Norwegian studies (Ekern, 1972). When the cows were given high quality grass silage ad libitum and concentrates according to yield (Table I), the total dry matter intake was but little affected when the a m o u n t of concentrate was increased during the first weeks o f the lactation b u t then gradually decreased during mid lactation. Consequently, during the important period of early lactation with previously high levels of concentrate feeding further supplementation m a y induce very small changes in total energy intake as also illustrated b y Broster and Thomas (1981).

Exploitation o f body energy reserves G o o d cows are capable of mobilizing large amounts of energy for milk production during early lactation provided sufficient stores of b o d y fat exist (Flatt et al., 1972). Extreme exploitation of energy reserves should, however, be avoided for several reasons. Firstly, the succession of fattening and mobilization for milk production is energetically less efficient than using feed energy directly for milk production (Moe et al., 1970). Utilization of cheap forage or pasture for fattening may, however, offset the importance of these relationships in practice. Secondly, fat ruminants require more energy for maintenance (M. McNiven, 1983, unpublished) and consume less forage during early lactation (Ekern, 1972). Lastly, excessive fatness at parturition m a y be detrimental to health and fertility.

446 REACTIONS TO FEED ENERGY ALLOCATION Milk yield response to past and current feed energy supplies Response in dairy cows to level and change in feed energy supply depends on a number of factors including yield potential of the cow and stage of lactation, body reserves, and the previous as well as present levels of feed energy, protein and specific nutrients. Classical investigations of the effect of plane of nutrition on lactation performance (Frederiksen, 1931; Jensen et al., 1942; Larsen and Larsen, 1955) measured responses by changing from low to moderate or moderate to high supplies of energy per kg 4% FCM (energy yield). Marginal responses were invariably higher in the former step (low--moderate) as also confirmed later by others (Hvidsten, 1955; Nordfeldt and Ruudvere, 1963; Nordfeldt and Claesson, 1964; Larsen et al., 1969; Wiktorsson, 1971; Ekern, 1972). In most of these studies feeds were allocated according to yield throughout lactation, which may be open to criticism from the point of view of methodology. In particular, a low ratio of feed energy to milk would tend to suppress yields in a decelerating fashion. Nevertheless, experiments in which cows were fed according to yield formed the basis for practical energy feeding standards which have been widely applied (Flatt et al., 1972). Over the years appreciation has risen for a more flexible approach to standard feeding, and attention has turned towards input--output relationships of various feed energy supplies (Ekern, 1972; Broster, 1974; Johnson, 1977; Ostergaard, 1979). Available evidence indicates that mean milk response to changes in energy intake obeys the law of diminishing returns (e.g., Broster, 1974), however, the issue is somewhat complicated by the level of feeding and the potential of the cow. Moreover, yield responses to changing feed energy level may be perceived as immediate (short term) and also residual (long term) in nature. Thus, concomitant with development of lactation, sufficient energy (and protein) to attain high peak yield enhances the total lactation performance. According to Broster (1976) an increase in peak yield of 1 kg day-' results in a 150-200 kg increase for the total lactation, provided that there is an adequate energy supply during the descending part of lactation. Generally, responses in milk yield to changes in intake depend more on current yield than on stage of lactation. Since yields are higher soon after calving, cows then respond more to adequate feeding, especially cows of high production potential (Johnson, 1977). It is noteworthy, however, that the great residual effect on milk yield reported for energy increments in addition to low basic levels diminishes or even disappears at higher planes of nutrition (Broster and Thomas, 1981). The rate of decline in yield during mid-lactation is largely individually determined through the partition of energy into milk or body fat, yet diet and plane of feeding do influence the outcome (Ekern, 1972; Broster,

447

1974). Clearly excessive feeding in mid or late lactation depresses the efficiency of feed conversion into milk. Such overfeeding may, however, be acceptable when body weight recovery is desired. The impact of early lactation on overall milk production points to the importance of pre-partum as well as post-partum feeding, and to the intervening change in feed supply. In general it appears that cows should be fed at a level which ensures good condition at calving. Low level feeding during the dry period may reduce milk yield (Broster, 1971). Heavy pre-calving feeding on the other hand combined with rather liberal energy supply during the lactation, may result in higher peak yield (Swanson and Hinton, 1962; Farries, 1975) with slightly more (Farries, 1975) or similar milk yield (Broster et al., 1958, 1964; Ekern, 1972), and lower forage intake during the following lactation (Ekern, 1972).

Effect of forage Efficient milk production generally depends on high quality forage (Castle and Watson, 1975; Bertilsson et al., 1979; Ekern and Vik-Mo, 1979; Kristensen et al., 1979) with the most positive responses achieved from an ad libitum feeding system, in contrast to restricted forage supply. In our own laboratory (Myhre and Vik-Mo, 1975) adjusted standard feeding based on direct cut, formic acid-treated silage resulted in more milk (1.2 kg FCM day -1) when the grass was cut early (Table II). Higher dry matter (DM) content of the later cut silage (26.6 vs. 20.6%) probably promoted higher DM intakes, but nutrient supplies from silage TABLE II Effect of early harvest of grass for ensiling on forage intake and milk yield of dairy c o w s (Myhre and Vik-Mo, 1975) Early grass harvest*

Late grass harvest

Feed intake d a y Grass silage (kg DM) 9.4 Grass silage (FU) 7.0 Concentrates (kg DM) 5.5

10.1 6.7 6.0

Milk yield day -~ Milk (kg) F a t (g kg -1) Protein (g kg -I) FCM (kg)

22.1 39 34 21.8

21.4 38 34 20.6

*Early harvest = at head emergence o f t i m o t h y . Late harvest is t w o w e e k s later.

448 were still inferior to those observed with the earlier cutting. Evidently greater amounts of concentrates are needed to substitute for lower nutrient intakes by relatively late cut grass silage. In line with the results given in Table II, Thomas et al. {1981) observed higher peak yield (2.7 kg day -1) with increased digestibility of silage fed ad libitum, but the immediate response was n o t accompanied by greater lactation yield. There axe even examples which show that the immediate response to extra concentrate exceeds the total lactation response when cows are fed on high quality forage (Steen and Gordon, 1980). This contradicts the findings of other workers (Broster, 1974: Johnson, 1977). Interaction of diet components thus appears a possibility and high concentrate feeding in early or mid-lactation m a y be less critical when high quality roughages are fed ad libitum (Broster and Thomas, 1981). Bovine ketosis

Excessive fatness at calving and underfeeding of energy after calving seem to be two prominent features of this metabolic disorder (Schultz, 1974; Baird, 1982). The precipitating cause of ketosis is probably carbohydrate insufficiency due to maintained milk ( l a c t o s e ) o u t p u t in the presence of inadequate glucose supply. The latter relates jointly to the digestive processes in the cow and to low feed intake. Ketotic cows typically are hypoglycaemic and respond to treatments with improved blood glucose. Extensive fat mobilization in ketotic cows manifests itself as ketones being generated from endogenous fatty acids, and by development of a fatty liver. Ultimately, during ketosis, milk yield declines, but it is high yielders which seem most prone to ketosis (Pehrson, 1966; Dale et al., 1978). This is probably associated with the greater risk o f severe underfeeding during early lactation, as indicated by results from a Norwegian survey (Fig. 1). Evidently in herds with high ketosis frequency the concentrate allowances post-partum were increased more slowly than recommended; which would result in greater underfeeding during early lactation. The a m o u n t of concentrates per cow and year was, however, almost equal for the three categories of herds which underlines the relatively low supplies during early lactation in herds with more ketotic cows. Moreover, forage supplies often were less than anticipated in herds with high ketosis frequency (Dale et al., 1978). Observations of total feed intake during the first m o n t h of lactation showed that an underfeeding o f more than 3 FU day -1, which is equal to the energy requirement for 7.5 kg 4% FCM, occurred in nearly 30% o f the cows in herds having a clinical ketosis level higher than 10%. In herds with less than 10% clinical ketosis less than 10% of the cows were observed with an energy deficit greater than 3 FU day -1 (Dale et al., 1978). By underfeeding during early lactation hypoglycaemia/ketonaemia m a y be induced and c o m m o n l y precede visible signs of clinical ketosis, nota-

449 /Recommended

10

dietary ~:llowance < 10°/o Ketosis

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i -25

10

°Io

,,

> 3 0 °Io

4

i -

. . . .

//:;...-

6 ? u c o u

10-30

. . . . .

8

g

I 0

5

i

I

I

10 15 20 Stage of lactation

I

i

25

30

Fig. 1. R e c o m m e n d e d allowances of concentrates in early lactation and some amounts used, set out according to the incidence of ketosis (H. Dale and L. Vik-Mo, 1978, unpublished).

bly low appetite (Dale et al., 1979). Despite this, the hazards to the cows' health from subclinical ketosis may be somewhat obscured, but greater ketonaemia was associated with suppressed yields during early lactation in various feeding experiments (Vik-Mo and Refsdal, 1982; L. Vik-Mo, 1983, unpublished).

Fertility Reproduction in the cow may be influenced by long term as well as current levels of feeding expressed, respectively, by condition at calving and weight change after calving (Ducker, 1980). Interaction effects of these and other factors may occur because nutrition probably modifies fertility by subtle mechanisms. An optimum condition for fertility has been established by Mulvany (Ducker, 1980). However, rather inconclusive results have been obtained in experiments designed to test influences of pre- and post-calving feeding level on health and productivity (Gardner, 1969; A.O. Refsdal and L. Vik-Mo, 1983, unpublished). Frequently, however, cows which are fat at calving have reproductive problems, as well as increased susceptibility to infections and metabolic diseases. This "fat cow syndrome" is associated with fatty metamorphosis of the liver (Morrow, 1976). Fatty liver arises mainly as a consequence of fat mobilization related to substandard feeding post-partum, yet dependent upon adipose fat stored during previous liberal feeding. Greater fatness of the liver one week post-partum is related to low fertility in the previous as well as current lactation (Reid et al., 1979a, b). Ducker (1980) reviewed reports on liveweight losses accompanied by suppressed fertility,

450 but some studies did not show such a relationship. Thus, it was claimed that if low fertility were to be induced, body weight losses would have to be followed by low blood glucose concentration. This proposition agrees with the observed relationship between ketonaemia/hypoglycaemia and cystic ovaries in cows deliberately underfed during early lactation (Refsdal, 1980). When aiming at high fertility the feed energy level evidently should not deviate too much from standard requirements neither by underfeeding during early lactation nor by overfeeding during mid and late lactation. Principally, it appears that a feeding system which allows optimal expression of milk production potential in the cow simultaneously promotes sound reproduction and reduces ketosis. APPLICATION

Principles Individual adjustment of concentrates at intervals throughout the lactation is the key point in any standard feeding programme. Consequently, the system requires that the individual cow's performance is observed and that qualitative judgement of available roughages is made. In Norway such a system has been practised, and it may serve as an example for further discussion (see also Fig. 2). (a) Individual milk recordings about once a month serve as the basis for estimation of feed requirements, using energy standards. (b) Rationing is based on prepared schedules for winter and summer feeding. Usually the same amount of roughage (ad libitum or restricted quantities) is offered to all cows and only concentrates are rationed according

in early

mid and late ~

~

0

=.-:'=''throughout I -2

0

I I 2 4 Month of lactation

~

I 6

/

I 8

10

Fig. 2. Principles of adjusted standard feeding according to the Breirem and Ekern system (Ekern, 1972). e--e---e Milk yield day-'; - energy supply day-'; ....... forage intake day- i.

451

to yield, usually in steps equal to the energy requirement of 2.5 kg of milk, i.e., 1 FU or about 1 kg of concentrates. (c) A qualitative judgement scheme is available for the main forages, particularly grass silage, based on date of harvest, botanical composition, N-fertilization and in vitro digestibility values of test samples. By ad libitum forage feeding the individual cow is allowed to adjust her intake independent of milk yield. Except for early lactation, however, the amount of concentrates should be adjusted according to average forage intake, besides individual milk yield. The system thus may favour cows with high capacity for forage consumption.

Irnplications While feed adjustments are made at intervals of some weeks, the lactation cycle may practically be divided into four phases, i.e., (a) dry period, (b) early lactation, (c) peak lactation, and (d) mid and late lactation. The salient points of feeding strategy in the various phases are set out as follows: (a) During the first part of the dry period the cow should be given 125-175% (5--7 FU day -1) of her maintenance energy need, the plane depending upon age and condition. During the last 2--3 weeks pre-partum the energy feeding may increase to 175--225% (7--9 FU day -1 ) of maintenance, including concentrates at 2--5 kg day -1, depending upon forage supply and status of the cow. Thus the system apportions more concentrates to good milkers which have become thin, while saving on feed to cows already in good condition at the end of lactation. (b) As the milk yield rises rapidly during the first 2--3 weeks of lactation, energy needs may increase faster than intake capacity. Appetite then is vital. From our experience, adequate amounts of high quality forage are essential to secure good performances during this early stage of lactation (Ekern and Macleod, 1978). Ad libitum forage feeding appears to be beneficial as it has advantages similar to those of the complete feeding system. On the other hand, concentrates ad libitum may promote digestive upsets and appetite problems (Ekern, 1972). From experience, it is advisable to increase the amount of concentrate by about 0.5 kg day -1 up to a maximum, the amount depending on forage, yield, age and size of the cow. This type of lead feeding may follow close to appetite limits and often occurs as a struggle to avoid underfeeding, rather than leading intake ahead of production (Alderman, 1979). (c) During the second--third month of lactation, when yield remains high, maximum feed intake should be maintained in high yielding cows by a combination of ad libitum forage and liberal concentrate feeding. Poorer cows with high forage consumption, but with a declining or stabilized level of production should be given less concentrates. (d) During the declining phase of lactation all individuals should be given concentrates according to yield, avoiding over-consumption of energy.

452

High yielders which have become thin due to lack of intake capacity during early lactation may be given extra feed above standard. Adjusted standard feeding including ad libitum intake of forage and lead feeding during early lactation is an alternative to complete feeding (Coppock et al., 1974) or flat rate feeding (¢)stergaard, 1979), particularly under small farm conditions. Here, our experience indicates that concentrate rationing according to yield, modified for body condition, may secure appropriate or maximum peak intake and prevent undue variation in body condition, as cows apparently do not regulate intake according to requirement (Coppock et al., 1974). In this way attention to the individual cow has a beneficial effect on the feed input/milk output relationship (Leaver, 1980). Adjusted standard feeding, as described, stresses the significance of high forage consumption together with efficient use of concentrates, and high feed efficiency overall. One of the main difficulties in this, as in other feeding systems, is adjustment of concentrates according to cow yield potential, especially during early lactation. Body condition changes should be observed as a corrective. By using proper techniques for the recording of individual milk yield and use of equipment for individual concentrate feeding in loose housing (e.g., electronic neck key) an adjusted standard feeding seems feasible even for larger herds. The advantages of computerized diet calculation, including test results on forage quality, may then be utilized.

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RESUME Ekern, A. et Vik-Mo, L., 1983. Alimentation standard et alimentation renforc~e des vaches laiti~res. Livest. Prod. Sci., 10: 443--455 (en anglais). L'alimentation standard signifie que la quantit~ d'aliment offerte est adjust~e aux besoins actuels, plus particuli~rement en ~nergie. L'alimentation renforc~e implique u n apport liberal en d~but de lactation de fa~on ~ stimuler les vaches en vue d'atteindre un pic maximum de lactation. Contrairement ~ l'alimentation standard, eUe permet la vache d'exprimer son potentiel laitier au cours de la p~riode critique du dSbut de la lactation. Cependant, on peut pratiquer une alimentation standard corrig~e de faqon plus souple par la distribution ad libitum des fourrages, une alimentation renforc~e en d~but de lactation et une distribution individuelle du concentrfi tout au long. L'alimentation standard corrig~e requiert l'enregistrement par intervalles de la production laiti~re individuelle et une appreciation de la qualit$ des fourrages disponibles. On d~crit et discute ce systhme. Appliqud avec souplesse, il semble applicable au mieux dans les petites exploitations. I1 peut l'~tre aussi aux troupeaux plus grands, grfice ~ un syst~me informatis~ de calcul des rations associfi ~ des techniques ad~quates de contrSle laitier et de distribution des concentr~s pour chaque vache. L'alimentation standard corrig~e, telle qu'elle est d~crite, souligne l'int~r~t d'une consommation ~lev~e de fourrages en m~me temps que d'une utilisation efficace de concentr~s, d ' u n e efficacit~ globale ~lev~e et d ' u n e prevention de la c~tose et de l'infertilitY.

KURZFASSUNG Ekern, A. und Vik-Mo, L., 1983. Standardfiitterung und Fiitterung nach dem "Lead Feeding System" bei Milchkiihen, Livest. Prod. Sci., 10:443--455 (auf englisch). Standardfiitterung bedeutet, dass sich die angebotene Futtermenge nach dem tats~chlichen Bedarf richtet, wobei die Energie besonders beriicksichtigt wird. Lead-Feeding bedeutet eine Art grossziigige Zuteilung w~hrend des Laktationsbeginns, um dadurch die Kuh zu HSchstleistung zu veranlassen. Im Gegensatz zu einer strikten Standardfiitterung, erlaubt das Lead-Feeding der Kuh, ihr Leistungspotential wiihrend der kritischen Periode des Laktationsbeginns zu entfalten. Leistungsorientierte Standardfiitterung kSnnte jedoch flexibler gestaltet warden durch Ad-Libitum-Rohfutter, LeadFeeding w~hrend des Laktationsbeginns und individueller Zuteilung yon Kraftfutter. Leistungsorientierte Standardfiitterung erfordert regelm~sige Milchkontrolle und qualitative Beurteilung des Grundfutters. Solch ein System wird beschrieben und diskutiert. Eine flexible, leistungsorientierte Standardfiitterung scheint sehr geeignet ftir kleine Betriebe zu sein. Bei Rationsbarechnung mittels Computer und individueller Mflchleistungskontrolle und Einsatz von Kraftfutter, ist das Fiittarungssystem auch fiir gr~ssere Herden geeignet. Die beschriebene leistungsgerechte Standardfiitterung streicht die Bedeutung einer hohen Futteraufnahme und eines effizienten Einsatzes vor Kraftfutter fiir die Leistung heraus u n d wirkt sich positiv auf Ketose und Unfruchtbarkeit aus.