- Email: [email protected]
concentrate ration
Livestock Production Science 61 (1999) 23–31
The metabolisable energy requirement for maintenance and the efficiency of use of metabolisable energy for lactation and tissue gain in dairy cows offered a straw / concentrate ration R.M. Kirkland*, F.J. Gordon
1
The Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down, Northern Ireland BT26 6 DR, UK Received 31 August 1998; received in revised form 14 December 1998; accepted 25 February 1999
Abstract Data from a series of 36 complete energy balance trials (determined by indirect calorimetry) with eight high genetic merit lactating Holstein Friesian cows offered a straw / concentrate ration (0.18:0.82 dry matter basis) were analysed by a range of regression techniques to determine the metabolisable energy (ME) required for maintenance (ME m ), and the efficiencies of ME use for lactation (k l ) and concomitant tissue gain (k g ). In the data set, milk yield ranged from 1.0 to 37.2 kg / day (s.d. 10.56), with this achieved by stage of lactation, plane of nutrition and drying off two quarters of all animals. Mean ME m was determined as 0.61 MJ / kg 0.75 per day (range 0.60–0.62) which was proportionately 0.27 above the value predicted from Agricultural and Food Research Council (AFRC, 1990) (0.48 MJ / kg 0.75 ). It is suggested that ME m is influenced by animal genotype or body condition, which can both reflect differences in fat and protein contents of the body. The mean k l value produced was 0.59, which is above that (0.51) calculated from the relationship k l 5 El( 0 ) / ME p when the latter is calculated using the ME m predicted from AFRC (1990). The mean derived value of k g , 0.86, has limited biological meaning considering the small portion of total energy use on which the estimate is based. 1999 Elsevier Science B.V. All rights reserved. Keywords: Body condition; Calorimetry; Dairy cow; Energy utilisation; Genotype
1. Introduction The current energy rationing system adopted in the United Kingdom for ruminants, the metabolisable energy (ME) system (Agricultural and Food Re*Corresponding author. Tel.: 1 44-1846-682-484; fax: 1 441846-689-594. E-mail address: [email protected] (R.M. Kirkland) 1 Also member of staff of the Department of Agriculture for Northern Ireland and The Queen’s University of Belfast.
search Council (AFRC 1990), is based on a factorial approach to the estimation of requirements. It is axiomatic that in this approach each component of the system should be accurately determined. Within this framework, the ME requirement for maintenance (ME m ) and the efficiency of utilisation of ME for milk production (k l ) in dairy cows are important parameters. AFRC (1990) based their recommendations for ME m on measures of fasting heat production (FHP). The validity of using this approach has been
0301-6226 / 99 / $ – see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 99 )00046-9
24
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
questioned due to effects of breed (Blaxter and Wainman, 1966) and maturity (Moe, 1981), inter alia, and more recently by Chowdhury and Ørskov (1994) who suggest that animals should be fed to meet their glucogenic need during measurement of ‘fasting’ metabolism. Nevertheless, estimates derived using this methodology have been in line with those recorded using regression techniques by earlier workers (Moe et al., 1970, 0.51; Van Es et al., 1970, 0.49; Van Es, 1975, 0.49; Vermorel et al., 1982, 0.51 MJ / kg 0.75 per day). Aphoristically, k l , when predicted from corrected milk energy output (El( 0) ) as a proportion of ME available for production (ME p ), is strongly influenced by the value of ME m used in the calculation of ME p . A number of recent studies have reported low k l values (compared with AFRC, 1990) when adopting this approach (Unsworth et al., 1994: 0.55; Gordon et al., 1995a, 0.58; Yan et al., 1997a, 0.53; Beever et al., 1997, 0.54), and it has been suggested (Yan et al., 1997a), that these low k l values have been due to the underprediction of ME m using the equations of AFRC (1990). The data produced by Yan et al. (1997a) using regression analyses to predict ME m and k l from a large number of calorimetric measurements with grass silage based diets has been particularly important in trying to understand these discrepancies. These workers suggest that not only is ME m higher than AFRC (1990), but it also varies according to the forage:concentrate ratio of the diet. In contrast forage:concentrate ratio has no effect on k l . These data raise the question as to whether the higher maintenance noted by Yan et al. (1997a) purely reflects the use of diets containing ensiled grass as opposed to other forage / non-forage-based rations. This is particularly in view of the recent data by Cammell et al. (1998) which indicates that ME m with non-grass silage-based diets is in line with that of AFRC (1990), while k l is much lower. The primary objective of the present study was therefore to establish, using regression techniques, the ME m and k l on a non-grass silage (straw / concentrate)based diet to establish if the high ME m and k l values reported by Yan et al. (1997a) were also relevant to non-grass silage-based diets. Limited data are available on the efficiency of use of ME for concomitant tissue gain during lactation
(k g ). Most published results suggest that the efficiency of this process approaches that of lactation (k l ) (Armstrong and Blaxter, 1965; Patle and Mudgal, 1977), and this led AFRC (1990) to adopt a constant coefficient of 0.95 that of k l , although the regressions of Moe et al. (1970) and Yan et al. (1997a) suggest that k g is much higher than k l . A secondary objective of the present study was therefore to provide further evidence on the efficiency of concomitant tissue gain during lactation (k g ) with straw / concentrate-based diets.
2. Materials and methods
2.1. Animals, diet and calorimeters Eight high genetic merit (PTA( 95 ) fat 1 protein 5 42 kg (s.d. 9.8 kg)) Holstein–Friesian dairy cows were subjected to energy metabolism studies at this Institute. Up to five measurements of gaseous exchange were carried out on each cow in indirect, open-circuit respiration calorimeters, providing a total of 36 determinations across a wide range of milk yields. Each individual calorimetric period represented a particular production level achieved by independently modifying both daily dietary ME allowance and physiological state in all cows. With the latter, cows were milked initially (periods 1–3) in all four quarters before being dried off in two quarters while milking was continued in the remaining two (periods 4 and 5). For each measurement period cows remained in the chambers for 72 h, with measurements of gaseous exchange taken over the final 48 h. While the cows were not familiarised to the environment of the respiration chambers prior to the beginning of the experiment, there was no evidence of either behavioral abnormalities or elevated heat productions during the first period of the study. A total mixed ration (TMR) of straw and concentrate (0.18 : 0.82 dry matter basis) was offered throughout the course of the trial. The concentrate portion of the diet consisted of (g / kg fresh weight) barley (105), maize (100), molassed sugar beet pulp (130), citrus pulp (200), soybean (200), rapemeal (155), megalac (45), white fishmeal (50) and mineral supplement (15). As fed, the TMR had the following
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
mean composition (g / kg): dry matter (DM) 840, CP 213, ADF 203, NDF 308 and GE 18.88 (MJ / kg DM). Dietary ME concentration for each individual cow was determined twice, once in a 6-day study undertaken during the second calorimetric measurement and incorporating the 3 days prior to, and the 3 days during the chamber period. The second digestibility was undertaken as a 9-day balance either following (and including) calorimetric periods 4 (one cow), or 5 (six cows). The mean of the two determinations per cow was taken as the diet ME concentration for that cow throughout the study. One cow was removed half way through the study due to ill health while another was dried off after period 4. All equipment (with the exception that harnesses were not used for faeces / urine separation in the present trial), sampling procedures, and analytical methods used in the calorimetric studies, as well as calibration tests, were as described by Gordon et al. (1995b) and Yan et al. (1997a), respectively. The results of the calibration tests recorded recoveries of 100.89 and 101.35% for the CO 2 and O 2 analysers, respectively.
2.2. Data analysis Data on energy utilisation were analysed using a range of regression techniques to determine ME m , k l and k g . Where appropriate, milk energy secretion was corrected to zero energy balance (El( 0) ) according to AFRC (1990); thus El(0 ) 5 milk energy output (El ) minus (0.84 3 negative energy retention; 2 Eg ), or plus a positive energy retention ( 1 Eg ). Furthermore, for those cows which were pregnant during the trial, ME requirements for pregnancy at each calorimetric period were predicted from AFRC
25
(1990) and the value subtracted from the MEI of each individual cow. As there were up to five repeat measurements on individual cows in the study these cow effects were removed during the development of the regressions. The range of regression models used to analyse the data from the present study are given in Table 1. Eq. (1) provides an estimate of both ME m and k l , while Eq. (2) additionally predicts the efficiency of concomitant lipogenesis during lactation (k g ). Similarly, Eq. (3), Moe et al. (1970) is adapted from Eq. (2) but divides the measurements of energy retention into positive and negative components with the reciprocals of constants ‘b’ and ‘c’ giving the efficiencies of utilisation of ME for lactation and tissue gain respectively. Eq. (4), Aguillera et al. (1990) is similar to Eq. (1) and provides an estimate of ME m , but does not include the correction for negative tissue energy balance in the measure of milk energy secretion suggested by AFRC (1990). In Eq. (5), Garrett et al. (1959), heat production is regressed on ME intake (both variables expressed on a per unit metabolic weight basis) and ME m is determined where ME intake equates with heat production. With the final model, Eq. (6), k l is predicted using the ME m derived from the mean of Eqs. (1)–(5).
3. Results Summary data on animals and calorimetric measurements are presented in Table 2 and demonstrate the wide range in intakes and production levels achieved, with the ME intake ranging from 79.5 to 292.8 MJ / day, and milk energy output from 2.8 to 108.3 MJ / day. The range in energy balance data is
Table 1 The regression models used in the analysis of the data from the present study a Equations El( 0 ) 5 aMEI 1 b MEI 5 aMW 1 bEl 1 cEg MEI 5 aMW 1 bEl 1 c( 1 Eg ) 1 d(2Eg ) El 1 Eg 5 aMEI 2 b HP 5 aMEI 1 b El( 0 ) 5 aME p a
Reference
Moe et al. (1970) Aguillera et al. (1990) Garrett et al. (1959)
Eq. no. (1) (2) (3) (4) (5) (6)
Where MW is metabolic liveweight; HP is heat production; MEI is metabolisable energy intake; ME p is ME available for production.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
26
Table 2 Data on animals and energy utilisation in the present study Min Cows Milk yield (kg / day) Live weight (kg) Parity Days of pregnancy Days of lactation Condition score a Energy utilisation GEI (MJ / day) Energy outputs ( MJ /day) Heat production Milk Energy retained ME intake ( MJ /day) a
Max
Mean
s.d.
1 542 2 0 171 2.0
37.2 663 4 133 556 3.0
19.9 610 3.1 41.2 326.2 2.5
10.56 37.0 0.64 39.71 134.02 0.22
122.9
453.9
288.6
90.48
75.9 2.8 2 10.8
161.4 108.3 24.3
117.7 62.1 1.5
23.92 30.57 8.31
79.5
292.8
182.8
56.79
Condition score where 1 is very thin and 5 is very fat.
however relatively small (210.8 to 24.3 MJ / day) as this was part of the objective of the original study from which these data were derived. Nineteen of the 36 estimates of energy retention were positive (range 0.7–24.3 MJ / day). Using the regression models listed previously (Table 1) with the present data set resulted in the regression equations given in Table 3, along with the derived estimates of ME m , k l and k g . In Eq. (1), El( 0) regressed on MEI (both expressed per unit metabolic weight) produced estimates of ME m of 0.60 MJ / 0.75 2 kg per day and k l of 0.59. The R value associated with this equation is very high (0.99) and the
standard errors are low (0.01 and 0.005 for ME intake and intercept, respectively). This relationship is shown diagrammatically in Fig. 1. In the regressions relating MEI to metabolic weight and energy balance (Eqs. (2) and (3)), the predicted values of ME m and k l were similar to those predicted from Eq. (1) (0.61 MJ / kg 0.75 per day and 0.58, respectively for Eq. (2); 0.62 MJ / kg 0.75 per day and 0.59, respectively for Eq. (3)). In Eqs. (2) and (3), the line of regression has been forced through the origin to remove the constant (intercept) from the equation hence assigning the corresponding amount of energy to the maintenance function, as
Table 3 The regression equations and derived values of metabolisable energy required for maintenance (ME m ), and the efficiencies of utilisation of ME for lactation (k l ) and tissue gain (k g ) predicted from the present data set with dairy cows a Equations
R2
ME m MJ / kg 0.75
kl
kg
El( 0 ) 5 0.59 ( 0.01 ) MEI 2 0.354 ( 0.005 ) MEI 5 0.61 ( 0.019 ) MW 1 1.713 ( 0.035 ) El 1 1.186 ( 0.149 ) Eg MEI 5 0.616 ( 0.019 ) MW 1 1.710 ( 0.036 ) El 1 1.133 ( 0.179 ) ( 1 Eg ) 1 1.331 ( 0.303 ) (2Eg ) El 1 Eg 5 0.595 ( 0.011 ) MEI 2 0.363 ( 0.005 ) HP 5 0.405 ( 0.011 ) MEI 1 0.363 ( 0.018 ) El( 0 ) 5 0.59 ( 0.01 ) ME p Mean
0.99 1.00 1.00 0.99 0.99 0.99 0.99
0.60 0.61 0.62 0.61 0.61
0.59 0.58 0.59
0.84 0.88
0.59 0.59
0.86
a
0.61
Eq. no. (1) (2) (3) (4) (5) (6)
Figures in parentheses are the standard errors associated with the estimates. El( 0 ) , corrected milk energy output (MJ / kg 0.75 in Eq. (1), and MJ / day in Eq. (6)); MEI, ME intake (MJ / kg 0.75 in Eqs. (1), (4) and (5), and MJ / day in Eqs. (2) and (3); MW, metabolic liveweight (kg 0.75 ); El , milk energy output (MJ / day in Eqs. (2) and (3), and MJ / kg 0.75 in Eq. (4)); Eg , energy balance (MJ / day in Eqs. (2) and (3), and MJ / kg 0.75 in Eq. (4)); (2Eg ), ( 1 Eg ), negative and positive energy balance, respectively (MJ / day); HP, heat production (MJ / kg 0.75 ).
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
27
Fig. 1. The regression of metabolisable energy intake (MEI) on corrected milk energy output (E1( 0 ) ).
suggested by Moe et al. (1970). Furthermore, the estimate of k g obtained from regression Eq. (2), at 0.84, is similar to that from Eq. (3) (0.88), although the standard errors associated with these figures (0.149 and 0.179 for Eqs. (2) and (3), respectively) are quite large. Regression of El 1 Eg (Eq. (4)), or HP (Eq. (5)), on ME intake both produce estimates of ME m of 0.61 MJ / kg 0.75 per day, near to those predicted from Eqs. (1)–(3). In Eq. (6) El( 0) was regressed against ME p , the value for maintenance having been taken as 0.61 MJ / kg 0.75 (i.e. the mean obtained from the preceding models). Using this approach the estimate of k l , at 0.59, was equal to that predicted from the other regression techniques. As with Eq. (1), all equations had highly significant associated values of R 2 and all constants had comparatively low standard errors.
4. Discussion The results from the current study differ in some respects from those which would be predicted from the equations of AFRC (1990), and suggest that
components of the factorial approach adopted by AFRC (1990) for estimating energy requirements in dairy cows may be inaccurate.
4.1. ME requirements for maintenance In the present study the predicted ME m values were remarkably similar across the range of regression techniques used, with a mean of 0.61 MJ / kg 0.75 per day. This translates into a daily ME requirement of 74.9 MJ for cows with a liveweight of 610 kg (i.e. the mean liveweight recorded in the present study). In contrast, using the approach of AFRC (1990) would indicate an ME m of 0.48 MJ / kg 0.75 per day for the animals and diets (qm 5 0.64) used in this study, which translates to a daily maintenance requirement for cows in the present study of 59 MJ. This latter value is proportionately 0.27 lower than the mean value obtained here with regression methods. This higher value for ME m recorded in the present study, in comparison with AFRC (1990) does, however, support other recently published estimates. In a recent review of 221 calorimetric trials carried
28
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
out at this Institute, with lactating dairy cows offered grass silage-based diets, Yan et al. (1997a), using a range of linear and multiple regression techniques, similarly noted a high mean value of ME m at 0.67 MJ / kg 0.75 per day (range, 0.61–0.75). Other high values of ME m with lactating cows fed forage-based diets, also calculated by regression techniques, have been reported by Patle and Mudgal (1977), Unsworth et al. (1994) and Hayasaka et al. (1995) (means of 0.57, 0.64 and 0.59 MJ / kg 0.75 per day, respectively). All these values are, however, in marked contrast to the lower values reported by Moe et al. (1970), Van Es et al.(1970), Van Es (1975) and Vermorel et al. (1982) (0.51, 0.49, 0.49 and 0.51 MJ / kg 0.75 per day, respectively). More recently, Cammell et al. (1998) has reported an ME m of 0.506 MJ / kg 0.75 for lactating cows (n 5 50) fed either whole crop wheat or a maize silage-based total mixed ration. In their review, Yan et al., (1997a) suggested that the disparity between the high ME m values found in their trial (mean 0.67) and that calculated according to the equations of AFRC (1990) might be explained by the differences in approaches adopted to determine ME m . Chiefly, these related to the use of regression techniques on data derived from lactating animals with ad lib feeding levels of grass silagebased diets, in contrast to the fasting metabolism studies with steers and dry cows on which AFRC (1990) recommendations were based. However, the hypothesis that the fasting metabolism methodology per se results in low values of ME m is not supported by further work by Yan et al. (1997b), which indicate similarly high estimates of ME m (mean 0.69 MJ / kg 0.75 ) even when derived from fasting metabolism studies. Furthermore, the suggestion that ME m is influenced by plane of nutrition or physiological state is not supported by the data from the present study. More recent attention has focused towards the possible impact of diet type on ME m , particularly the possibility of higher ME m on grass silage-based diets (Reynolds et al., 1997). Recent evidence supports the view that proportion of concentrate in grass silage diets can influence ME m with Yan et al. (1997a) obtaining estimates of ME m of 0.59, 0.68 and 0.74 MJ / kg 0.75 per day for diets containing , 0.50, 0.5– 0.99 and 1.00 forage, respectively (GE basis). Against this background it is interesting to note that
the ME m recorded in the present study, 0.61 MJ / kg 0.75 , is directly in line with the lower value obtained by Yan et al. (1997a) (0.59) for diets of similar forage proportion to that used here. These similar values have therefore been obtained with two very different forages, grass silage and straw. While the data of Yan et al. (1997a) would indicate that ME m may be influenced by forage:concentrate ratio in the diet, the present study would not provide any evidence that grass silage per se has any specific effect. This would rather support the view that the proportion of forage in the diet may influence the amount of metabolically active intestinal tissue which leads to an increase in total heat energy loss from these tissues (Reynolds et al., 1991), and therefore ME m . Webster (1981) estimated that greater than 40% of total heat production was associated with the abdominal organs. While this hypothesis provides appropriate linkages between the high ME m values of Yan et al. (1997a) and those of the present study, there remains the major discrepancies between these recent sets of data and some of the previously noted studies (Moe et al., 1970; Van Es et al., 1970; Van Es, 1975; Vermorel et al., 1982; Cammell et al., 1998), which have reported much lower values of ME m . It is obvious that any difference could not reflect forage:concentrate ratio as all these latter studies did contain forage as a component of the DM intake, often as a high proportion of the total diet. If diet effects are not the major factor influencing the high ME m recorded in some recent studies then it is probable that these differences reflect the change in animal type which has occurred over the past number of years. It is recognised that body condition of cows reflects differences in the relative masses of protein and fat tissue and Webster (1981) has suggested that ME m will be more related to body protein than fat mass. That turnover of body protein has a high associated energy cost is well established, with Baldwin et al. (1980) estimating that this process may account for 9–12% of basal energy expenditure. In contrast, body fat has a much lower rate of turnover and is subsequently much less exothermic, accounting for an estimated 2–4% of basal metabolism. Hence, it is possible that body condition of cows at a given body weight may have a major influence on ME m per unit metabolic weight.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
Some recent work at this Institute would tend to support this hypothesis (J. Birnie and R. Agnew, personal communication). Furthermore, in a study with pigs, van Milgen et al. (1998) determined the FHP of fat and lean breeds. These workers noted a significant difference in FHP between breeds with the fatter Meishan breed found to have a lower daily FHP/ kg 0.75 compared to the leaner Large White and ´ Pietrain breeds. Visceral mass was found to contribute more to FHP (per kg 0.81 ) than that of muscle mass, while fat had a negative effect. Other authors have suggested that fat free body mass (FFM) is the most reliable predictor of basal heat production. In a study with humans, Sparti et al. (1997) reported that 83% of the variation in resting metabolic rate was accounted for by FFM, a proportion which was not improved by including the composition of the lean mass in the calculation. The high ME m values in the present study were obtained with relatively lean high genetic merit cows (range in condition scores from 2.0 to 3.0) which, using the mean liveweight (610 kg), and the equations of Gibb and Ivings (1993) to calculate fat mass, would suggest a FFM of 511 and 469 kg for cows of condition score 2.0 and 3.0 respectively. Hence, it is tempting to speculate that a major part of the disparity observed between the ME m recorded in the present study and the lower values noted previously, might be explained by a difference in body condition between animal genotypes used presently (high genetic merit animals) and those included in the studies on which AFRC (1990) (predominantly steers and dry cows) and others have based their predictions.
4.2. The efficiency of utilisation of ME for lactation ( kl ) The estimates of the efficiencies of utilisation of ME for lactation, predicted from the range of linear and multiple regression equations in the present study are almost identical (range, 0.58–0.59; mean, 0.59), and relatively close to the values published by a number of other workers using similar regression methods (Van Es et al., 1970, 0.62; Van Es, 1975, 0.60; Vermorel et al., 1982, 0.59), but marginally below that reported by others (Moe et al., 1970, 0.64; Patle and Mudgal, 1977, 0.66; Unsworth et al., 1994, 0.67; Hayasaka et al., 1995, 0.64; Yan et al.,
29
1997a, 0.65). It is also somewhat below the value predicted from the equation k l 5 0.35qm 1 0.420 (AFRC, 1990) (0.64). Furthermore, the value obtained from the present study (0.59) is in close agreement with that reported by Yan et al. (1997a) (0.62) with similar dietary forage contents ( , 0.50 forage GE / total GE) as in the present study. Yan et al. (1997a) has highlighted the major differences between estimates of k l derived by regression techniques in comparison with those obtained by using the equations of AFRC (1990) to estimate ME m , and subsequently ME p , which is then related to milk energy output. For example, using the latter approach of AFRC (1990) to calculate ME m in the present study, the calculated k l , at 0.51, would be much lower than the 0.59 obtained using the regression technique. This much lower k l is in agreement with those noted by Unsworth and Gordon (1984), Unsworth (1991), Unsworth et al. (1994), Gordon et al. (1995a), Beever et al. (1997) and Yan et al. (1997a) when using a similar approach to calculate ME p (AFRC, 1990). It had originally been postulated (Yan et al., 1997a) that as all these studies (with the exception of that by Beever et al., 1997) contained diets based on grass silage, diet type could have been the reason for the low k l . However, the present data would support the view that these low k l values were not related specifically to the diet type used in these studies, as similar results have been obtained in the present study using straw as the roughage source.
4.3. The efficiency of utilisation of ME for tissue gain ( k g ) Multiple regression analyses of the data from the present study (Eqs. (2) and (3)) produced two estimates of the efficiency of utilisation of ME for concomitant tissue gain (0.84 and 0.88; mean, 0.86). However, the standard errors of the estimates are large (0.149 and 0.179, respectively), reflecting the limited variation and small number of estimates of positive Eg in the data set used. The corollary is that the present estimates of k g may be considered as having limited biological meaning and hence must be viewed with caution. From a biochemical point of view, Van Es and Van der Honing (1979) suggest that the theoretical maximum efficiency of fat synthesis is close to 90% when dietary fat or long-chain fatty
30
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
acids are used directly as the substrate, while the corresponding efficiency from volatile fatty acids (which would have been the primary dietary substrate in the present study) is only | 70%. However, while the mean k g value in the present study is greater than that derived by Moe et al. (1970), 0.75, when using similar regression techniques, it is close to those of Hayasaka et al. (1995) and Yan et al. (1997a), and would support the view that tissue gain during lactation may be more efficient than milk energy output. These high efficiencies would, however, be in contrast to the commonly accepted view that k g during lactation is similar to that of k l . For example, Armstrong and Blaxter (1965) reported k g as proportionately 0.96 of k l (where k l 5 0.69). Other workers, including Van Es et al. (1970), Van Es (1975), Patle and Mudgal (1977), Aguillera et al. (1990), Rapetti et al. (1997) and Yan et al. (1997b), have also reported similar efficiencies of lipogenesis in lactating animals to that of lactation, with k l in these trials ranging from 0.60 up to 0.67. For beef animals, AFRC (1990) regard the efficiency of use of ME for fattening to be influenced by diet metabolisability (qm ). The studies cited previously encompass a range of values of k g from approximately 0.56 (Van Es et al., 1970) to 0.92 obtained by Yan et al. (1997a) with grass silagebased rations. It is tempting to speculate that while recognising the inaccuracies of the present high estimates of k g that it could also reflect the quality of the diet used.
5. Conclusion A series of regression techniques were used to estimate ME m in dairy cattle. The ME m value obtained, 0.61 MJ / kg 0.75 per day, was proportionately 0.27 above that predicted by AFRC (1990) (0.48 MJ / kg 0.75 ). The k l value predicted by regression analysis was 0.59. Both the ME m and k l determined in this study using straw / concentrate diets, are very close to those obtained by Yan et al. (1997a) using grass silage-based diets with a similar proportion of forage. The efficiency of concomitant tissue energy retention was 0.86, suggesting, circumspectly, that tissue deposition during lactation is proportionately 0.46 more efficient than lactation itself.
Acknowledgements The authors wish to thank the staff of the Agricultural Research Institute of Northern Ireland for their assistance throughout the course of this study.
References Agricultural and Food Research Council, 1990. Technical Committee on Responses to Nutrients, Report Number 5, Nutritive Requirements of Ruminant Animals. Energy Nutr. Abstr. Rev. (Ser. B) 60, 729–804. Aguillera, J.F., 1990. Protein and energy metabolism of lactating Granadina goats. Br. J. Nutr. 63, 165–175. Armstrong, D.G., Blaxter, K.L., 1965. Effects of acetic and propionic acids on energy retention and milk secretion in goats. In: Blaxter, K.L. (Ed.), Proceedings of the 3rd Symposium on the Energy Metabolism of Farm Animals, The Energy Metabolism of Ruminants, London Academic Press (European Association for Animal Production, Publication No. 11), pp. 59–72. Baldwin, R.L., Smith, N.E., Taylor, J., Sharp, M., 1980. Manipulating metabolic parameters to improve growth rate and milk secretion. J. Anim. Sci. 51, 1416–1428. Beever, D.E., Cammell, S.B., Sutton, J.D., Humphries, D.J., 1997. The effect of stage of harvest of maize silage on the concentration and efficiency of utilisation of metabolisable energy by lactating dairy cows. In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, pp. 359–362. Blaxter, K.L., Wainman, F.W., 1966. The fasting metabolism of cattle. Br. J. Nutr. 20, 103–111. Cammell, S.B., Dhanoa, M.S., Beever, D.E., Sutton, J.D., France, J., 1998. An examination of the metabolisable energy requirements of lactating cows. Proc. Br. Soc. Anim. Sci., annual conference, p. 197, abst. Chowdhury, S.A., Ørskov, E.R., 1994. Implications of fasting on the energy metabolism and feed evaluation in ruminants. J. Anim. Feed Sci. 3, 161–169. Garrett, W.N., Meyer, J.H., Lofgreen, G.P., 1959. The comparative energy requirements of sheep and cattle for maintenance and gain. J. Anim. Sci. 18, 528–547. Gibb, M.J., Ivings, W.E., 1993. A note on the estimation of the body fat, protein and energy content of lactating HolsteinFriesian cows by measurement of condition score and live weight. Anim. Prod. 56, 281–283. Gordon, F.J., Patterson, D.C., Yan, T., Porter, M.G., Mayne, C.S., Unsworth, E.F., 1995a. The influence of genetic index for milk production on the response to complete diet feeding and the utilisation of energy and nitrogen. Anim. Sci. 61, 199–210. Gordon, F.J., Porter, M.G., Mayne, C.S., Unsworth, E.F., Kilpatrick, D.J., 1995b. Effect of forage digestibility and type of concentrate on nutrient utilisation for lactating dairy cattle. J. Dairy Res. 62, 15–27.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31 Hayasaka, K., Takusari, N., Yamagishi, N., 1995. Energy metabolism in lactating Holstein cows. Anim. Sci. Technol. (in Japanese, with English abstract) 66, 374–382. Moe, P.W., 1981. Energy metabolism of dairy cattle. J. Dairy Sci. 64, 1120–1139. Moe, P.W., Tyrrell, H.F., Flatt, W.P., 1970. Partial efficiency of energy use for maintenance, lactation, body gain and gestation ¨ in the dairy cow. In: Schurch, A., Wenk, C. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 13, pp. 65–68. Patle, B.R., Mudgal, V.D., 1977. Utilisation of dietary energy for maintenance, milk production and lipogenesis by lactating crossbred cows during their midstage of lactation. Br. J. Nutr. 37, 23–33. Rapetti, L., Crovetto, G.M., Tamburini, A., Galassi, G., Sandrucci, A., Succi, G., 1997. Some aspects of the energy metabolism in lactating goats. In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, Cambridge, pp. 93–96. Reynolds, C.K., Tyrrell, H.F., Reynolds, P.L., 1991. Effects of dietary forage-to-concentrate ratio and intake on energy metabolism in growing beef heifers: whole body energy and nitrogen balance and visceral heat production. J. Nutr. 121, 994–1103. Reynolds, C.K., Ferris, C.P., Hocquette, J.F., 1997. Effects of diet quality (summary of the discussion). In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, Cambridge, p. 102. Sparti, A., DeLany, J.P., de la Bretonne, J.A., Sander, G.E., Bray, G.A., 1997. Relationship between resting metabolic rate and the composition of the fat-free mass. In: Metab. Clin. Exp., Vol. 46 (10), pp. 1225–1230. Unsworth, E.F., 1991. The efficiency of utilisation of metabolisable energy for lactation from grass silage-based diets. In: Aguillera, J.F. (Ed.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 76, pp. 179–181. Unsworth, E.F., Gordon, F.J., 1984. The energy utilisation of
31
wilted and unwilted grass silage by lactating dairy cows. 58th Annual Report of the Agricultural Research Institute of Northern Ireland, pp. 13–20. Unsworth, E.F., Mayne, C.S., Cushnahan, A., Gordon, F.J., 1994. The energy utilisation of grass silage diets by lactating dairy cows. In: Aguillera, J.F. (Ed.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 76, pp. 179–181. Van Es, A.J.H., 1975. Feed evaluation for dairy cows. Livest. Prod. Sci. 2, 95–107. Van Es, A.J.H., Van der Honing, Y., 1979. Energy utilisation. In: Broster, W.H., Swan, H. (Eds.), Feeding Strategy for the High Yielding Dairy Cow, pp. 68–89, ch. 5. Van Es, A.J.H., Nijkamp, H.J., Vogt, J.E., 1970. Feed evaluation ¨ for dairy cows. In: Schurch, A., Wenk, C. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 13, pp. 61–64. van Milgen, J., Bernier, J.F., Lecozler, Y., Dubois, S., Noblet, J., 1998. Major determinants of fasting heat production and energetic cost of activity in growing pigs of different body weight and breed / castration combination. Br. J. Nutr. 79, 509–517. ´ Vermorel, M., Remond, B., Vernet, J., Liamadis, D., 1982. Utilisation of body reserves by high producing cows in early lactation; effects of crude protein and amino acid supply. In: Ekern, A., Sundsøl, F. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 29, pp. 18–21. Webster, A.J.F., 1981. The energetic efficiency of metabolism. Proc. Nutr. Soc. 40, 121–128. Yan, T., Gordon, F.J., Agnew, R.E., Porter, M.G., Patterson, D.C., 1997a. The metabolisable energy requirement for maintenance and the efficiency of utilisation of metabolisable energy for lactation by dairy cows offered grass silage-based diets. Livest. Prod. Sci. 51, 141–150. Yan, T., Gordon, F.J., Ferris, C.P., Agnew, R.E., Porter, M.G., Patterson, D.C., 1997b. The fasting heat production and effect of lactation on energy utilisation by dairy cows offered foragebased diets. Livest. Prod. Sci. 52, 177–186.
The metabolisable energy requirement for maintenance and the efficiency of use of metabolisable energy for lactation and tissue gain in dairy cows offered a straw / concentrate ration R.M. Kirkland*, F.J. Gordon
1
The Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down, Northern Ireland BT26 6 DR, UK Received 31 August 1998; received in revised form 14 December 1998; accepted 25 February 1999
Abstract Data from a series of 36 complete energy balance trials (determined by indirect calorimetry) with eight high genetic merit lactating Holstein Friesian cows offered a straw / concentrate ration (0.18:0.82 dry matter basis) were analysed by a range of regression techniques to determine the metabolisable energy (ME) required for maintenance (ME m ), and the efficiencies of ME use for lactation (k l ) and concomitant tissue gain (k g ). In the data set, milk yield ranged from 1.0 to 37.2 kg / day (s.d. 10.56), with this achieved by stage of lactation, plane of nutrition and drying off two quarters of all animals. Mean ME m was determined as 0.61 MJ / kg 0.75 per day (range 0.60–0.62) which was proportionately 0.27 above the value predicted from Agricultural and Food Research Council (AFRC, 1990) (0.48 MJ / kg 0.75 ). It is suggested that ME m is influenced by animal genotype or body condition, which can both reflect differences in fat and protein contents of the body. The mean k l value produced was 0.59, which is above that (0.51) calculated from the relationship k l 5 El( 0 ) / ME p when the latter is calculated using the ME m predicted from AFRC (1990). The mean derived value of k g , 0.86, has limited biological meaning considering the small portion of total energy use on which the estimate is based. 1999 Elsevier Science B.V. All rights reserved. Keywords: Body condition; Calorimetry; Dairy cow; Energy utilisation; Genotype
1. Introduction The current energy rationing system adopted in the United Kingdom for ruminants, the metabolisable energy (ME) system (Agricultural and Food Re*Corresponding author. Tel.: 1 44-1846-682-484; fax: 1 441846-689-594. E-mail address: [email protected] (R.M. Kirkland) 1 Also member of staff of the Department of Agriculture for Northern Ireland and The Queen’s University of Belfast.
search Council (AFRC 1990), is based on a factorial approach to the estimation of requirements. It is axiomatic that in this approach each component of the system should be accurately determined. Within this framework, the ME requirement for maintenance (ME m ) and the efficiency of utilisation of ME for milk production (k l ) in dairy cows are important parameters. AFRC (1990) based their recommendations for ME m on measures of fasting heat production (FHP). The validity of using this approach has been
0301-6226 / 99 / $ – see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 99 )00046-9
24
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
questioned due to effects of breed (Blaxter and Wainman, 1966) and maturity (Moe, 1981), inter alia, and more recently by Chowdhury and Ørskov (1994) who suggest that animals should be fed to meet their glucogenic need during measurement of ‘fasting’ metabolism. Nevertheless, estimates derived using this methodology have been in line with those recorded using regression techniques by earlier workers (Moe et al., 1970, 0.51; Van Es et al., 1970, 0.49; Van Es, 1975, 0.49; Vermorel et al., 1982, 0.51 MJ / kg 0.75 per day). Aphoristically, k l , when predicted from corrected milk energy output (El( 0) ) as a proportion of ME available for production (ME p ), is strongly influenced by the value of ME m used in the calculation of ME p . A number of recent studies have reported low k l values (compared with AFRC, 1990) when adopting this approach (Unsworth et al., 1994: 0.55; Gordon et al., 1995a, 0.58; Yan et al., 1997a, 0.53; Beever et al., 1997, 0.54), and it has been suggested (Yan et al., 1997a), that these low k l values have been due to the underprediction of ME m using the equations of AFRC (1990). The data produced by Yan et al. (1997a) using regression analyses to predict ME m and k l from a large number of calorimetric measurements with grass silage based diets has been particularly important in trying to understand these discrepancies. These workers suggest that not only is ME m higher than AFRC (1990), but it also varies according to the forage:concentrate ratio of the diet. In contrast forage:concentrate ratio has no effect on k l . These data raise the question as to whether the higher maintenance noted by Yan et al. (1997a) purely reflects the use of diets containing ensiled grass as opposed to other forage / non-forage-based rations. This is particularly in view of the recent data by Cammell et al. (1998) which indicates that ME m with non-grass silage-based diets is in line with that of AFRC (1990), while k l is much lower. The primary objective of the present study was therefore to establish, using regression techniques, the ME m and k l on a non-grass silage (straw / concentrate)based diet to establish if the high ME m and k l values reported by Yan et al. (1997a) were also relevant to non-grass silage-based diets. Limited data are available on the efficiency of use of ME for concomitant tissue gain during lactation
(k g ). Most published results suggest that the efficiency of this process approaches that of lactation (k l ) (Armstrong and Blaxter, 1965; Patle and Mudgal, 1977), and this led AFRC (1990) to adopt a constant coefficient of 0.95 that of k l , although the regressions of Moe et al. (1970) and Yan et al. (1997a) suggest that k g is much higher than k l . A secondary objective of the present study was therefore to provide further evidence on the efficiency of concomitant tissue gain during lactation (k g ) with straw / concentrate-based diets.
2. Materials and methods
2.1. Animals, diet and calorimeters Eight high genetic merit (PTA( 95 ) fat 1 protein 5 42 kg (s.d. 9.8 kg)) Holstein–Friesian dairy cows were subjected to energy metabolism studies at this Institute. Up to five measurements of gaseous exchange were carried out on each cow in indirect, open-circuit respiration calorimeters, providing a total of 36 determinations across a wide range of milk yields. Each individual calorimetric period represented a particular production level achieved by independently modifying both daily dietary ME allowance and physiological state in all cows. With the latter, cows were milked initially (periods 1–3) in all four quarters before being dried off in two quarters while milking was continued in the remaining two (periods 4 and 5). For each measurement period cows remained in the chambers for 72 h, with measurements of gaseous exchange taken over the final 48 h. While the cows were not familiarised to the environment of the respiration chambers prior to the beginning of the experiment, there was no evidence of either behavioral abnormalities or elevated heat productions during the first period of the study. A total mixed ration (TMR) of straw and concentrate (0.18 : 0.82 dry matter basis) was offered throughout the course of the trial. The concentrate portion of the diet consisted of (g / kg fresh weight) barley (105), maize (100), molassed sugar beet pulp (130), citrus pulp (200), soybean (200), rapemeal (155), megalac (45), white fishmeal (50) and mineral supplement (15). As fed, the TMR had the following
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
mean composition (g / kg): dry matter (DM) 840, CP 213, ADF 203, NDF 308 and GE 18.88 (MJ / kg DM). Dietary ME concentration for each individual cow was determined twice, once in a 6-day study undertaken during the second calorimetric measurement and incorporating the 3 days prior to, and the 3 days during the chamber period. The second digestibility was undertaken as a 9-day balance either following (and including) calorimetric periods 4 (one cow), or 5 (six cows). The mean of the two determinations per cow was taken as the diet ME concentration for that cow throughout the study. One cow was removed half way through the study due to ill health while another was dried off after period 4. All equipment (with the exception that harnesses were not used for faeces / urine separation in the present trial), sampling procedures, and analytical methods used in the calorimetric studies, as well as calibration tests, were as described by Gordon et al. (1995b) and Yan et al. (1997a), respectively. The results of the calibration tests recorded recoveries of 100.89 and 101.35% for the CO 2 and O 2 analysers, respectively.
2.2. Data analysis Data on energy utilisation were analysed using a range of regression techniques to determine ME m , k l and k g . Where appropriate, milk energy secretion was corrected to zero energy balance (El( 0) ) according to AFRC (1990); thus El(0 ) 5 milk energy output (El ) minus (0.84 3 negative energy retention; 2 Eg ), or plus a positive energy retention ( 1 Eg ). Furthermore, for those cows which were pregnant during the trial, ME requirements for pregnancy at each calorimetric period were predicted from AFRC
25
(1990) and the value subtracted from the MEI of each individual cow. As there were up to five repeat measurements on individual cows in the study these cow effects were removed during the development of the regressions. The range of regression models used to analyse the data from the present study are given in Table 1. Eq. (1) provides an estimate of both ME m and k l , while Eq. (2) additionally predicts the efficiency of concomitant lipogenesis during lactation (k g ). Similarly, Eq. (3), Moe et al. (1970) is adapted from Eq. (2) but divides the measurements of energy retention into positive and negative components with the reciprocals of constants ‘b’ and ‘c’ giving the efficiencies of utilisation of ME for lactation and tissue gain respectively. Eq. (4), Aguillera et al. (1990) is similar to Eq. (1) and provides an estimate of ME m , but does not include the correction for negative tissue energy balance in the measure of milk energy secretion suggested by AFRC (1990). In Eq. (5), Garrett et al. (1959), heat production is regressed on ME intake (both variables expressed on a per unit metabolic weight basis) and ME m is determined where ME intake equates with heat production. With the final model, Eq. (6), k l is predicted using the ME m derived from the mean of Eqs. (1)–(5).
3. Results Summary data on animals and calorimetric measurements are presented in Table 2 and demonstrate the wide range in intakes and production levels achieved, with the ME intake ranging from 79.5 to 292.8 MJ / day, and milk energy output from 2.8 to 108.3 MJ / day. The range in energy balance data is
Table 1 The regression models used in the analysis of the data from the present study a Equations El( 0 ) 5 aMEI 1 b MEI 5 aMW 1 bEl 1 cEg MEI 5 aMW 1 bEl 1 c( 1 Eg ) 1 d(2Eg ) El 1 Eg 5 aMEI 2 b HP 5 aMEI 1 b El( 0 ) 5 aME p a
Reference
Moe et al. (1970) Aguillera et al. (1990) Garrett et al. (1959)
Eq. no. (1) (2) (3) (4) (5) (6)
Where MW is metabolic liveweight; HP is heat production; MEI is metabolisable energy intake; ME p is ME available for production.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
26
Table 2 Data on animals and energy utilisation in the present study Min Cows Milk yield (kg / day) Live weight (kg) Parity Days of pregnancy Days of lactation Condition score a Energy utilisation GEI (MJ / day) Energy outputs ( MJ /day) Heat production Milk Energy retained ME intake ( MJ /day) a
Max
Mean
s.d.
1 542 2 0 171 2.0
37.2 663 4 133 556 3.0
19.9 610 3.1 41.2 326.2 2.5
10.56 37.0 0.64 39.71 134.02 0.22
122.9
453.9
288.6
90.48
75.9 2.8 2 10.8
161.4 108.3 24.3
117.7 62.1 1.5
23.92 30.57 8.31
79.5
292.8
182.8
56.79
Condition score where 1 is very thin and 5 is very fat.
however relatively small (210.8 to 24.3 MJ / day) as this was part of the objective of the original study from which these data were derived. Nineteen of the 36 estimates of energy retention were positive (range 0.7–24.3 MJ / day). Using the regression models listed previously (Table 1) with the present data set resulted in the regression equations given in Table 3, along with the derived estimates of ME m , k l and k g . In Eq. (1), El( 0) regressed on MEI (both expressed per unit metabolic weight) produced estimates of ME m of 0.60 MJ / 0.75 2 kg per day and k l of 0.59. The R value associated with this equation is very high (0.99) and the
standard errors are low (0.01 and 0.005 for ME intake and intercept, respectively). This relationship is shown diagrammatically in Fig. 1. In the regressions relating MEI to metabolic weight and energy balance (Eqs. (2) and (3)), the predicted values of ME m and k l were similar to those predicted from Eq. (1) (0.61 MJ / kg 0.75 per day and 0.58, respectively for Eq. (2); 0.62 MJ / kg 0.75 per day and 0.59, respectively for Eq. (3)). In Eqs. (2) and (3), the line of regression has been forced through the origin to remove the constant (intercept) from the equation hence assigning the corresponding amount of energy to the maintenance function, as
Table 3 The regression equations and derived values of metabolisable energy required for maintenance (ME m ), and the efficiencies of utilisation of ME for lactation (k l ) and tissue gain (k g ) predicted from the present data set with dairy cows a Equations
R2
ME m MJ / kg 0.75
kl
kg
El( 0 ) 5 0.59 ( 0.01 ) MEI 2 0.354 ( 0.005 ) MEI 5 0.61 ( 0.019 ) MW 1 1.713 ( 0.035 ) El 1 1.186 ( 0.149 ) Eg MEI 5 0.616 ( 0.019 ) MW 1 1.710 ( 0.036 ) El 1 1.133 ( 0.179 ) ( 1 Eg ) 1 1.331 ( 0.303 ) (2Eg ) El 1 Eg 5 0.595 ( 0.011 ) MEI 2 0.363 ( 0.005 ) HP 5 0.405 ( 0.011 ) MEI 1 0.363 ( 0.018 ) El( 0 ) 5 0.59 ( 0.01 ) ME p Mean
0.99 1.00 1.00 0.99 0.99 0.99 0.99
0.60 0.61 0.62 0.61 0.61
0.59 0.58 0.59
0.84 0.88
0.59 0.59
0.86
a
0.61
Eq. no. (1) (2) (3) (4) (5) (6)
Figures in parentheses are the standard errors associated with the estimates. El( 0 ) , corrected milk energy output (MJ / kg 0.75 in Eq. (1), and MJ / day in Eq. (6)); MEI, ME intake (MJ / kg 0.75 in Eqs. (1), (4) and (5), and MJ / day in Eqs. (2) and (3); MW, metabolic liveweight (kg 0.75 ); El , milk energy output (MJ / day in Eqs. (2) and (3), and MJ / kg 0.75 in Eq. (4)); Eg , energy balance (MJ / day in Eqs. (2) and (3), and MJ / kg 0.75 in Eq. (4)); (2Eg ), ( 1 Eg ), negative and positive energy balance, respectively (MJ / day); HP, heat production (MJ / kg 0.75 ).
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
27
Fig. 1. The regression of metabolisable energy intake (MEI) on corrected milk energy output (E1( 0 ) ).
suggested by Moe et al. (1970). Furthermore, the estimate of k g obtained from regression Eq. (2), at 0.84, is similar to that from Eq. (3) (0.88), although the standard errors associated with these figures (0.149 and 0.179 for Eqs. (2) and (3), respectively) are quite large. Regression of El 1 Eg (Eq. (4)), or HP (Eq. (5)), on ME intake both produce estimates of ME m of 0.61 MJ / kg 0.75 per day, near to those predicted from Eqs. (1)–(3). In Eq. (6) El( 0) was regressed against ME p , the value for maintenance having been taken as 0.61 MJ / kg 0.75 (i.e. the mean obtained from the preceding models). Using this approach the estimate of k l , at 0.59, was equal to that predicted from the other regression techniques. As with Eq. (1), all equations had highly significant associated values of R 2 and all constants had comparatively low standard errors.
4. Discussion The results from the current study differ in some respects from those which would be predicted from the equations of AFRC (1990), and suggest that
components of the factorial approach adopted by AFRC (1990) for estimating energy requirements in dairy cows may be inaccurate.
4.1. ME requirements for maintenance In the present study the predicted ME m values were remarkably similar across the range of regression techniques used, with a mean of 0.61 MJ / kg 0.75 per day. This translates into a daily ME requirement of 74.9 MJ for cows with a liveweight of 610 kg (i.e. the mean liveweight recorded in the present study). In contrast, using the approach of AFRC (1990) would indicate an ME m of 0.48 MJ / kg 0.75 per day for the animals and diets (qm 5 0.64) used in this study, which translates to a daily maintenance requirement for cows in the present study of 59 MJ. This latter value is proportionately 0.27 lower than the mean value obtained here with regression methods. This higher value for ME m recorded in the present study, in comparison with AFRC (1990) does, however, support other recently published estimates. In a recent review of 221 calorimetric trials carried
28
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
out at this Institute, with lactating dairy cows offered grass silage-based diets, Yan et al. (1997a), using a range of linear and multiple regression techniques, similarly noted a high mean value of ME m at 0.67 MJ / kg 0.75 per day (range, 0.61–0.75). Other high values of ME m with lactating cows fed forage-based diets, also calculated by regression techniques, have been reported by Patle and Mudgal (1977), Unsworth et al. (1994) and Hayasaka et al. (1995) (means of 0.57, 0.64 and 0.59 MJ / kg 0.75 per day, respectively). All these values are, however, in marked contrast to the lower values reported by Moe et al. (1970), Van Es et al.(1970), Van Es (1975) and Vermorel et al. (1982) (0.51, 0.49, 0.49 and 0.51 MJ / kg 0.75 per day, respectively). More recently, Cammell et al. (1998) has reported an ME m of 0.506 MJ / kg 0.75 for lactating cows (n 5 50) fed either whole crop wheat or a maize silage-based total mixed ration. In their review, Yan et al., (1997a) suggested that the disparity between the high ME m values found in their trial (mean 0.67) and that calculated according to the equations of AFRC (1990) might be explained by the differences in approaches adopted to determine ME m . Chiefly, these related to the use of regression techniques on data derived from lactating animals with ad lib feeding levels of grass silagebased diets, in contrast to the fasting metabolism studies with steers and dry cows on which AFRC (1990) recommendations were based. However, the hypothesis that the fasting metabolism methodology per se results in low values of ME m is not supported by further work by Yan et al. (1997b), which indicate similarly high estimates of ME m (mean 0.69 MJ / kg 0.75 ) even when derived from fasting metabolism studies. Furthermore, the suggestion that ME m is influenced by plane of nutrition or physiological state is not supported by the data from the present study. More recent attention has focused towards the possible impact of diet type on ME m , particularly the possibility of higher ME m on grass silage-based diets (Reynolds et al., 1997). Recent evidence supports the view that proportion of concentrate in grass silage diets can influence ME m with Yan et al. (1997a) obtaining estimates of ME m of 0.59, 0.68 and 0.74 MJ / kg 0.75 per day for diets containing , 0.50, 0.5– 0.99 and 1.00 forage, respectively (GE basis). Against this background it is interesting to note that
the ME m recorded in the present study, 0.61 MJ / kg 0.75 , is directly in line with the lower value obtained by Yan et al. (1997a) (0.59) for diets of similar forage proportion to that used here. These similar values have therefore been obtained with two very different forages, grass silage and straw. While the data of Yan et al. (1997a) would indicate that ME m may be influenced by forage:concentrate ratio in the diet, the present study would not provide any evidence that grass silage per se has any specific effect. This would rather support the view that the proportion of forage in the diet may influence the amount of metabolically active intestinal tissue which leads to an increase in total heat energy loss from these tissues (Reynolds et al., 1991), and therefore ME m . Webster (1981) estimated that greater than 40% of total heat production was associated with the abdominal organs. While this hypothesis provides appropriate linkages between the high ME m values of Yan et al. (1997a) and those of the present study, there remains the major discrepancies between these recent sets of data and some of the previously noted studies (Moe et al., 1970; Van Es et al., 1970; Van Es, 1975; Vermorel et al., 1982; Cammell et al., 1998), which have reported much lower values of ME m . It is obvious that any difference could not reflect forage:concentrate ratio as all these latter studies did contain forage as a component of the DM intake, often as a high proportion of the total diet. If diet effects are not the major factor influencing the high ME m recorded in some recent studies then it is probable that these differences reflect the change in animal type which has occurred over the past number of years. It is recognised that body condition of cows reflects differences in the relative masses of protein and fat tissue and Webster (1981) has suggested that ME m will be more related to body protein than fat mass. That turnover of body protein has a high associated energy cost is well established, with Baldwin et al. (1980) estimating that this process may account for 9–12% of basal energy expenditure. In contrast, body fat has a much lower rate of turnover and is subsequently much less exothermic, accounting for an estimated 2–4% of basal metabolism. Hence, it is possible that body condition of cows at a given body weight may have a major influence on ME m per unit metabolic weight.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
Some recent work at this Institute would tend to support this hypothesis (J. Birnie and R. Agnew, personal communication). Furthermore, in a study with pigs, van Milgen et al. (1998) determined the FHP of fat and lean breeds. These workers noted a significant difference in FHP between breeds with the fatter Meishan breed found to have a lower daily FHP/ kg 0.75 compared to the leaner Large White and ´ Pietrain breeds. Visceral mass was found to contribute more to FHP (per kg 0.81 ) than that of muscle mass, while fat had a negative effect. Other authors have suggested that fat free body mass (FFM) is the most reliable predictor of basal heat production. In a study with humans, Sparti et al. (1997) reported that 83% of the variation in resting metabolic rate was accounted for by FFM, a proportion which was not improved by including the composition of the lean mass in the calculation. The high ME m values in the present study were obtained with relatively lean high genetic merit cows (range in condition scores from 2.0 to 3.0) which, using the mean liveweight (610 kg), and the equations of Gibb and Ivings (1993) to calculate fat mass, would suggest a FFM of 511 and 469 kg for cows of condition score 2.0 and 3.0 respectively. Hence, it is tempting to speculate that a major part of the disparity observed between the ME m recorded in the present study and the lower values noted previously, might be explained by a difference in body condition between animal genotypes used presently (high genetic merit animals) and those included in the studies on which AFRC (1990) (predominantly steers and dry cows) and others have based their predictions.
4.2. The efficiency of utilisation of ME for lactation ( kl ) The estimates of the efficiencies of utilisation of ME for lactation, predicted from the range of linear and multiple regression equations in the present study are almost identical (range, 0.58–0.59; mean, 0.59), and relatively close to the values published by a number of other workers using similar regression methods (Van Es et al., 1970, 0.62; Van Es, 1975, 0.60; Vermorel et al., 1982, 0.59), but marginally below that reported by others (Moe et al., 1970, 0.64; Patle and Mudgal, 1977, 0.66; Unsworth et al., 1994, 0.67; Hayasaka et al., 1995, 0.64; Yan et al.,
29
1997a, 0.65). It is also somewhat below the value predicted from the equation k l 5 0.35qm 1 0.420 (AFRC, 1990) (0.64). Furthermore, the value obtained from the present study (0.59) is in close agreement with that reported by Yan et al. (1997a) (0.62) with similar dietary forage contents ( , 0.50 forage GE / total GE) as in the present study. Yan et al. (1997a) has highlighted the major differences between estimates of k l derived by regression techniques in comparison with those obtained by using the equations of AFRC (1990) to estimate ME m , and subsequently ME p , which is then related to milk energy output. For example, using the latter approach of AFRC (1990) to calculate ME m in the present study, the calculated k l , at 0.51, would be much lower than the 0.59 obtained using the regression technique. This much lower k l is in agreement with those noted by Unsworth and Gordon (1984), Unsworth (1991), Unsworth et al. (1994), Gordon et al. (1995a), Beever et al. (1997) and Yan et al. (1997a) when using a similar approach to calculate ME p (AFRC, 1990). It had originally been postulated (Yan et al., 1997a) that as all these studies (with the exception of that by Beever et al., 1997) contained diets based on grass silage, diet type could have been the reason for the low k l . However, the present data would support the view that these low k l values were not related specifically to the diet type used in these studies, as similar results have been obtained in the present study using straw as the roughage source.
4.3. The efficiency of utilisation of ME for tissue gain ( k g ) Multiple regression analyses of the data from the present study (Eqs. (2) and (3)) produced two estimates of the efficiency of utilisation of ME for concomitant tissue gain (0.84 and 0.88; mean, 0.86). However, the standard errors of the estimates are large (0.149 and 0.179, respectively), reflecting the limited variation and small number of estimates of positive Eg in the data set used. The corollary is that the present estimates of k g may be considered as having limited biological meaning and hence must be viewed with caution. From a biochemical point of view, Van Es and Van der Honing (1979) suggest that the theoretical maximum efficiency of fat synthesis is close to 90% when dietary fat or long-chain fatty
30
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31
acids are used directly as the substrate, while the corresponding efficiency from volatile fatty acids (which would have been the primary dietary substrate in the present study) is only | 70%. However, while the mean k g value in the present study is greater than that derived by Moe et al. (1970), 0.75, when using similar regression techniques, it is close to those of Hayasaka et al. (1995) and Yan et al. (1997a), and would support the view that tissue gain during lactation may be more efficient than milk energy output. These high efficiencies would, however, be in contrast to the commonly accepted view that k g during lactation is similar to that of k l . For example, Armstrong and Blaxter (1965) reported k g as proportionately 0.96 of k l (where k l 5 0.69). Other workers, including Van Es et al. (1970), Van Es (1975), Patle and Mudgal (1977), Aguillera et al. (1990), Rapetti et al. (1997) and Yan et al. (1997b), have also reported similar efficiencies of lipogenesis in lactating animals to that of lactation, with k l in these trials ranging from 0.60 up to 0.67. For beef animals, AFRC (1990) regard the efficiency of use of ME for fattening to be influenced by diet metabolisability (qm ). The studies cited previously encompass a range of values of k g from approximately 0.56 (Van Es et al., 1970) to 0.92 obtained by Yan et al. (1997a) with grass silagebased rations. It is tempting to speculate that while recognising the inaccuracies of the present high estimates of k g that it could also reflect the quality of the diet used.
5. Conclusion A series of regression techniques were used to estimate ME m in dairy cattle. The ME m value obtained, 0.61 MJ / kg 0.75 per day, was proportionately 0.27 above that predicted by AFRC (1990) (0.48 MJ / kg 0.75 ). The k l value predicted by regression analysis was 0.59. Both the ME m and k l determined in this study using straw / concentrate diets, are very close to those obtained by Yan et al. (1997a) using grass silage-based diets with a similar proportion of forage. The efficiency of concomitant tissue energy retention was 0.86, suggesting, circumspectly, that tissue deposition during lactation is proportionately 0.46 more efficient than lactation itself.
Acknowledgements The authors wish to thank the staff of the Agricultural Research Institute of Northern Ireland for their assistance throughout the course of this study.
References Agricultural and Food Research Council, 1990. Technical Committee on Responses to Nutrients, Report Number 5, Nutritive Requirements of Ruminant Animals. Energy Nutr. Abstr. Rev. (Ser. B) 60, 729–804. Aguillera, J.F., 1990. Protein and energy metabolism of lactating Granadina goats. Br. J. Nutr. 63, 165–175. Armstrong, D.G., Blaxter, K.L., 1965. Effects of acetic and propionic acids on energy retention and milk secretion in goats. In: Blaxter, K.L. (Ed.), Proceedings of the 3rd Symposium on the Energy Metabolism of Farm Animals, The Energy Metabolism of Ruminants, London Academic Press (European Association for Animal Production, Publication No. 11), pp. 59–72. Baldwin, R.L., Smith, N.E., Taylor, J., Sharp, M., 1980. Manipulating metabolic parameters to improve growth rate and milk secretion. J. Anim. Sci. 51, 1416–1428. Beever, D.E., Cammell, S.B., Sutton, J.D., Humphries, D.J., 1997. The effect of stage of harvest of maize silage on the concentration and efficiency of utilisation of metabolisable energy by lactating dairy cows. In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, pp. 359–362. Blaxter, K.L., Wainman, F.W., 1966. The fasting metabolism of cattle. Br. J. Nutr. 20, 103–111. Cammell, S.B., Dhanoa, M.S., Beever, D.E., Sutton, J.D., France, J., 1998. An examination of the metabolisable energy requirements of lactating cows. Proc. Br. Soc. Anim. Sci., annual conference, p. 197, abst. Chowdhury, S.A., Ørskov, E.R., 1994. Implications of fasting on the energy metabolism and feed evaluation in ruminants. J. Anim. Feed Sci. 3, 161–169. Garrett, W.N., Meyer, J.H., Lofgreen, G.P., 1959. The comparative energy requirements of sheep and cattle for maintenance and gain. J. Anim. Sci. 18, 528–547. Gibb, M.J., Ivings, W.E., 1993. A note on the estimation of the body fat, protein and energy content of lactating HolsteinFriesian cows by measurement of condition score and live weight. Anim. Prod. 56, 281–283. Gordon, F.J., Patterson, D.C., Yan, T., Porter, M.G., Mayne, C.S., Unsworth, E.F., 1995a. The influence of genetic index for milk production on the response to complete diet feeding and the utilisation of energy and nitrogen. Anim. Sci. 61, 199–210. Gordon, F.J., Porter, M.G., Mayne, C.S., Unsworth, E.F., Kilpatrick, D.J., 1995b. Effect of forage digestibility and type of concentrate on nutrient utilisation for lactating dairy cattle. J. Dairy Res. 62, 15–27.
R.M. Kirkland, F. J. Gordon / Livestock Production Science 61 (1999) 23 – 31 Hayasaka, K., Takusari, N., Yamagishi, N., 1995. Energy metabolism in lactating Holstein cows. Anim. Sci. Technol. (in Japanese, with English abstract) 66, 374–382. Moe, P.W., 1981. Energy metabolism of dairy cattle. J. Dairy Sci. 64, 1120–1139. Moe, P.W., Tyrrell, H.F., Flatt, W.P., 1970. Partial efficiency of energy use for maintenance, lactation, body gain and gestation ¨ in the dairy cow. In: Schurch, A., Wenk, C. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 13, pp. 65–68. Patle, B.R., Mudgal, V.D., 1977. Utilisation of dietary energy for maintenance, milk production and lipogenesis by lactating crossbred cows during their midstage of lactation. Br. J. Nutr. 37, 23–33. Rapetti, L., Crovetto, G.M., Tamburini, A., Galassi, G., Sandrucci, A., Succi, G., 1997. Some aspects of the energy metabolism in lactating goats. In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, Cambridge, pp. 93–96. Reynolds, C.K., Tyrrell, H.F., Reynolds, P.L., 1991. Effects of dietary forage-to-concentrate ratio and intake on energy metabolism in growing beef heifers: whole body energy and nitrogen balance and visceral heat production. J. Nutr. 121, 994–1103. Reynolds, C.K., Ferris, C.P., Hocquette, J.F., 1997. Effects of diet quality (summary of the discussion). In: McCracken, K.J., Unsworth, E.F., Wylie, A.R.G. (Eds.), Proceedings of the 14th Symposium on Energy Metabolism, Energy Metabolism of Farm Animals, Cambridge University Press, Cambridge, p. 102. Sparti, A., DeLany, J.P., de la Bretonne, J.A., Sander, G.E., Bray, G.A., 1997. Relationship between resting metabolic rate and the composition of the fat-free mass. In: Metab. Clin. Exp., Vol. 46 (10), pp. 1225–1230. Unsworth, E.F., 1991. The efficiency of utilisation of metabolisable energy for lactation from grass silage-based diets. In: Aguillera, J.F. (Ed.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 76, pp. 179–181. Unsworth, E.F., Gordon, F.J., 1984. The energy utilisation of
31
wilted and unwilted grass silage by lactating dairy cows. 58th Annual Report of the Agricultural Research Institute of Northern Ireland, pp. 13–20. Unsworth, E.F., Mayne, C.S., Cushnahan, A., Gordon, F.J., 1994. The energy utilisation of grass silage diets by lactating dairy cows. In: Aguillera, J.F. (Ed.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 76, pp. 179–181. Van Es, A.J.H., 1975. Feed evaluation for dairy cows. Livest. Prod. Sci. 2, 95–107. Van Es, A.J.H., Van der Honing, Y., 1979. Energy utilisation. In: Broster, W.H., Swan, H. (Eds.), Feeding Strategy for the High Yielding Dairy Cow, pp. 68–89, ch. 5. Van Es, A.J.H., Nijkamp, H.J., Vogt, J.E., 1970. Feed evaluation ¨ for dairy cows. In: Schurch, A., Wenk, C. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 13, pp. 61–64. van Milgen, J., Bernier, J.F., Lecozler, Y., Dubois, S., Noblet, J., 1998. Major determinants of fasting heat production and energetic cost of activity in growing pigs of different body weight and breed / castration combination. Br. J. Nutr. 79, 509–517. ´ Vermorel, M., Remond, B., Vernet, J., Liamadis, D., 1982. Utilisation of body reserves by high producing cows in early lactation; effects of crude protein and amino acid supply. In: Ekern, A., Sundsøl, F. (Eds.), Energy Metabolism of Farm Animals, European Association for Animal Production, Publication No. 29, pp. 18–21. Webster, A.J.F., 1981. The energetic efficiency of metabolism. Proc. Nutr. Soc. 40, 121–128. Yan, T., Gordon, F.J., Agnew, R.E., Porter, M.G., Patterson, D.C., 1997a. The metabolisable energy requirement for maintenance and the efficiency of utilisation of metabolisable energy for lactation by dairy cows offered grass silage-based diets. Livest. Prod. Sci. 51, 141–150. Yan, T., Gordon, F.J., Ferris, C.P., Agnew, R.E., Porter, M.G., Patterson, D.C., 1997b. The fasting heat production and effect of lactation on energy utilisation by dairy cows offered foragebased diets. Livest. Prod. Sci. 52, 177–186.