The effects of method of processing of starters, tallow inclusion and roughage supplementation on the performance of early-weaned calves

Animal Feed Science and Technology, 19 (1988) 231-246

231

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

The Effects of Method of P r o c e s s i n g of Starters, T a l l o w Inclusion and R o u g h a g e S u p p l e m e n t a t i o n on the P e r f o r m a n c e of E a r l y - W e a n e d Calves P.J. CAFFREY, C. MILLER*, P.O. BROPHY and D.L. KELLEHER

Department of Agriculture, University College Dublin, Lyons, Newcastle P. 0., Co. Dublin (Eire) (Received 22 October 1986; accepted for publication 22 June 1987)

ABSTRACT Caffrey, P.J., Miller, C., Brophy, P.O. and Kelleher, D.L., 1988. The effects of method of processing of starters, tallow inclusion and roughage supplementation on the performance of earlyweaned calves. Anim. Feed Sci. Technol., 19: 231-246. Two experiments involving 63 Friesian calves were carried out to investigate the effect of fat inclusion and method of processing of starters on the performance and roughage requirements of the early-weaned calf. Milk replacer was fed at the rate of 0.41 kg DM per calf daily for 23 days. Three starters, WPT, GPN, GTPN, based on 63.5% barley and 25% soya-bean meal, were fed ad libitum throughout each experiment. WPT and GPN were identical in composition, but differed in that whole barley was used in the production of an 8-mm pellet in WPT, whereas the barley was ground prior to the production of a 5-mm pencil in GPN. Starter GTP N differed from starter GPN i n t h a t it contained 3.5% tallow in place of 3.5% cassava. In Experiment 1, 18 calves were kept on expanded metal floors without access to long roughage for 62 days, followed by 10 days when they were bedded on straw and had free access to hay; in Experiment 2, 45 calves were bedded on straw and had free access to hay for a 58-day period. Apparent digestibility coefficients, based on a total 10-day collection (Days 49-58) in Experiment 1 were significantly different in the case of fat, where GTPN was higher ( P < 0.001 ) than GPN and in N-free extract where WPT was lower (P < 0.05) than the others; otherwise differences failed to reach significance. Whole barley voided in the faeces for WPT, expressed as a percentage ( _+ SE) of dietary barley, amounted to 4.27 + 1.03% in Experiment 1 and 4.56 + 1.13% in Experiment 2. Rumen fluid pH values were significantlyhigher at four sampling dates in the postweaning period with WPT than with the other starters when no supplementary roughage was provided in Experiment 1. Provision of long roughage during the final 10 days of Experiment 1 and in Experiment 2 resulted in a significant increase in rumen fluid pH values on all starters. Bloat was not observed o n W P w in either Experiment 1 or 2, or on any starter in Experiment 2. Persistent bloat occurred with GPN when no long roughage was provided in Experiment 1; bloating almost completely disappeared when long roughage was introduced towards the end of Experiment 1. In Experiment 2, liveweight gains were not significantlyaffected by starter type, except during *Present address: Waterford Co-operative Creamery, Dungarvan, Co. Waterford, Eire.

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© 1988 Elsevier Science Publishers B.V.

232 the post-weaningperiod when GTPN gave lowergains than GPN (P< 0.05). In contrast, in Experiment 1, when no long roughagewas provided, WPT fed calves gained 14.1 and 9.1 kg more than calvesfed the pencils with (GTPN) or without tallow (GPN) overa 62-dayperiod. In both experiments,intake of W~PT was highest and intake of GTPNwas lowest.

INTRODUCTION The relative costs of feeds often dictate that calves are weaned onto dry starters at an early age (Caffrey and Brophy, 1974). The limited rumen capacity of the young calf coupled with immature salivary glands (Kay, 1966; Williams et al., 1985) impose severe limitations on the composition and processing of the starter. It must be sufficiently concentrated to facilitate adequate energy intake within the constraints of limited rumen capacity, yet the diet must provide sufficient roughage or chemical buffers to maintain rumen function. With judicious selection of ingredients and appropriate processing of the starter, good calf performance can be achieved without supplementary roughage (Kay, 1969; Warner et al., 1973). However, may authors have reported good responses in terms of intakes and liveweight gains from roughage supplementation (Kellaway et al., 1973; T h o m a s and Hinks, 1982, 1983; Williams et al., 1985). the roughage may be provided separately from the starter (Caffrey and Brophy, 1974; Fisher et al., 1985) or incorporated in the starter (Thomas and Hinks, 1982, 1983; Williams et al., 1985). When provided separately, the intake of roughage seems to be governed more by the composition and palatabilities of starters and roughages fed than by the roughage requirements of the calf (Bartley, 1973; Kang and Leibholz, 1973). If incorporated in the starter, it involves additional costs in processing and the optimal level of inclusion is open to debate and is likely to be related to the composition and processing of both concentrate and roughage fractions of the diet (Kay, 1969; Preston and Willis, 1974; Thomas and Hinks, 1982 ). Since energy intake is often considered the main limiting factor to rate of gain in early-weaned calves, addition of fat to the starter seems the obvious way of increasing energy consumption (Preston and Willis, 1974). Early work with tallow in calf starters gave promising results (Johnson et al., 1956 ). However, many subsequent reports using tallow gave disappointing results in terms of intake and liveweight gains (Wrenn et al., 1979; Abdelgadir et al., 1984). Poor palatability is the reason most often cited for the low intake of tallowsupplemented starters. The present report deals with the effect of method of processing and inclusion of tallow (3.5%) in calf starters based on barley and soya-bean meal. Three starters were fed to Friesian calves, with and without supplementary roughage, and the parameters measured included digestibility, rumen fluid pH values, intake and liveweight gain.

233 MATERIALSAND METHODS Animals and diets

Sixty-three Friesian male calves were purchased locally over a 2-day period when they were 10-14 days old. They were gradually introduced to milk replacer according to routines previously outlined (Caffrey and Brophy, 1974) in a naturally ventilated straw-bedded house. On the fifth day, they were weighed and assigned to the experimental treatments. All weights and periods used in the text relate to this starting point. To minimise variation within experiments, the 18 heaviest calves were assigned to Experiment 1 and the remaining 45 calves to Experiment 2. Until weaning at 23 days, each calf received twice daily 1.71 warm ( 39 ° C ), milk replacer at a concentration of 125 g milk replacer powder 1-1, i.e., 425 g powder per calf day-1. The milk replacer was a commercial formulation based on skim milk and had a declared analysis of 180 g fat and 250 g protein k g - 1 powder and an assumed digestible energy (DE) of 19.5 MJ k g - 1. The starters (experimental treatments) were introduced on Day 1 and fed ad libitum throughout the experimental period. Starters were fed once daily in amounts that would result in 5-10% refusal daily. Feed intakes were recorded daily and calf weights recorded weekly. Representative samples of feed and refusals were retained for analysis. Water was available ad libitum throughout. The composition and chemical analysis of the three starters (WPT, GPN and GTPN) are presented in Table I. Starters WPT and GPN were identical in composition, but differed in that whole barley was mixed with the other ingreclients prior to extrusion through an 8-mm die in WPT (whole barley pellet) while the barley in GPN (ground barley pencil) was ground in a h a m m e r mill using a 3.5-mm screen prior to extrusion through a 5-mm die. Starter GTPN (ground barley pencil with tallow) differed from GPN in that it contained 3.5% tallow in place of 3.5% cassava. The starters were prepared from the same batch of the respective ingredients. Experiment I - - restricted roughage

Eighteen calves (mean initial weight 50.4 kg) were randomly assigned to three starters (WPT, GPN, GTPN) at 6 calves per treatment. They were placed in individual fibre-glass pens (1.5 × 0.5 m) with elevated expanded metal floors in a controlled environment house. Feed and water was provided from buckets placed in rings at the end of each pen and the calves were restrained by neckties. The calves were weaned off milk replacer after 23 days and starter was provided ad libitum for 62 days. No long roughage was provided throughout this period. After 62 days, the calves were transferred to individual pens in a naturally ventilated house where intake and performance were monitored for a further

234 TABLE 1 Composition and chemical analysis of dietary treatments (starters) in Experiments I and 2 Dietary treatment (starters) 1 WPT 8-mm pellet

GPN 5-ram pencil

GTPN 5-mm pencil

Composition (g kg - 1) Whole barley Ground barley (3.5 ram) Soya-bean meal Cassava Tallow Molasses Supplement2 Dry matter (DM)

635 250 35 50 30 873

635 250 35 50 30 872

635 250 35 50 30 881

Chemical analysis (g kg -1DM) Crude protein Crude fibre Oil Ash N-free extract

210 61 22 64 643

213 53 19 60 655

202 62 63 58 615

Gross energy (MJ kg -1 DM)

17.68

17.76

18.69

IWPT: whole barley pellet; GPN: ground barley pencil; GTPN: ground barley pencil with tallow. 2Supplying per 1000 kg starter: Ca 5.6 kg; P 1.0 kg; NaC1 8.0 kg; Mg 0.1 kg; Fe 20 g; Mn 35 g; Zn 56 g; Cu 8 g; 1 3 g; Co 1 g; vitamin A 8 M. i.u.; vitamin D 2 M. i.u.; vitamin E 10 000 i.u.; vitamin K 1 g; riboflavin 2 g; virginiamycin 10 g; flavour 100 g. 10 days. D u r i n g t h i s p e r i o d , t h e y w e r e b e d d e d o n s t r a w w i t h free access to h a y a n d w e r e fed t h e s a m e s t a r t e r as earlier. T h r o u g h o u t t h e e x p e r i m e n t c a l v e s were o b s e r v e d f r o m 8.00 t o 17.00 h daily for i n c i d e n c e o f b l o a t , r u m i n a t i o n a n d signs of ill h e a l t h .

Experiment 2 - - long roughage F o r t y - f i v e calves ( m e a n initial w e i g h t 45.2 k g ) w e r e r a n d o m l y a s s i g n e d to t h e s a m e t h r e e s t a r t e r s as in E x p e r i m e n t 1 a t 15 c a l v e s p e r t r e a t m e n t . T h e e x e c u t i o n o f t h e e x p e r i m e n t w h i c h l a s t e d 58 d a y s w a s s i m i l a r to E x p e r i m e n t 1, e x c e p t t h a t t h e c a l v e s w e r e h o u s e d in s t r a w - b e d d e d p e n s in a n a t u r a l l y v e n t i l a t e d h o u s e w i t h free access to r y e g r a s s h a y ( i n v i t r o d r y m a t t e r d i g e s t i b i l i t y 58% ). T e n calves p e r t r e a t m e n t g r o u p w e r e k e p t in i n d i v i d u a l p e n s (1.65 X 1.2 m ) while t h e r e m a i n i n g 5 c a l v e s o f e a c h t r e a t m e n t g r o u p w e r e in a g r o u p p e n (1.65 X 6 m ) . H a y i n t a k e w a s m e a s u r e d for t h e g r o u p - p e n n e d calves o v e r

235 a 22-day period (Days 37-58). Due to admixture of hay with bedding, it was not possible to get accurate hay intakes for the individually penned calves. No attempt was made to measure straw (bedding) intake.

Determination of digestibility and whole barley voided

Total 10-day collection of faeces was made while the calves in Experiment 1 were receiving the starter diets only (Days 49-58). Faeces were collected on perforated polythene sheets placed under each pen, dried in a forced air oven at 100 °C and stored for chemical analysis and whole barley determination with respect to starter W P w (whole barley pellet). For the whole barley determinations, a 200-g sample was retained for each of the 6 calves receiving starter WPT, saturated with water and washed through a 3.35-mm sieve. The residue remaining on the sieve after floating shells were removed was arbitratily taken as the whole barley voided in the faeces. This residue was expressed as a percentage of the total faeces (DM basis) and of the dietary intake of barley using the composition (Table I ) and digestibility (Table II) of the :starter. Faecal grab samples were also taken from 8 calves fed the same starter (WPT) in Experiment 2 on Day 58. Voided barley was expressed in the same way, with allowance being made for the contribution of hay to faecal output. The hay was assumed to have a dry matter digestibility of 58%. The proportion of the barley which remained intact during pelleting of starter WPT was estimated by physically separating intact from broken and fractured grains following soaking in water for 48 h.

Rumen pH, incidence of bloating and rumination Rumen fluid samples were obtained by stomach tube using a 50-ml syringe for suction on Days 33, 42, 51, 58 and 72 from the calves in Experiment i and on Days 35, 44 and 51 from 18 calves (6 per treatment group) in Experiment 2 for pH determinations. The samples were taken at 14.00-15.00 h and pH determinations performed immediately using a glass electrode pH meter. Incidence and severity of bloat were recorded, with severity rated on a scale 1-4; 1 representing slight distention on left flank and 4 representing severe distention on both sides and obvious distress. ~ e n it was considered that a calf was in imminent danger of succumbing, rumen gas was evacuated by means of a stomach tube. Calves were also observed for rumination, but the duration of rumination was not recorded.

236 TABLE II Apparent digestibility coefficients of dry matter, organic matter, energy and proximate constituents of three starters fed as sole diet in Experiment 1 Starter WP T

Number of calves

SEM GPN

GTPN

Comparison WPT v. others

GPN V. GTPN

6

6

6

Mean liveweight (kg)

89.6

81.8

76.8

Mean 10-day intake (kg DM) Days 49-58

28.4

20.9

19.2

Digestibility (%) Dry matter Organic matter Energy Crude protein Crude fibre Oil N-free extract

76.8 78.1 76.2 77.1 33.6 74.6 82.8

79.7 81.9 78.7 76.4 32.9 64.5 87.1

78.8 80.0 77.6 76.6 38.2 82.2 84.9

1.28 0.97 1.03 1.51 3.25 2.10 0.94

NS NS NS NS NS NS *

NS NS NS NS NS *** NS

Digestible energy (MJ kg-XDM)

13.47

13.98

14.50

0.19

*

NS

Chemical analysis S t a n d a r d p r o c e d u r e s ( A s s o c i a t i o n of Official A g r i c u l t u r a l C h e m i s t s (1970) w e r e u s e d to d e t e r m i n e t h e p r o x i m a t e c o n s t i t u e n t s o f feeds a n d faeces. G r o s s e n e r g y w a s d e t e r m i n e d in a n a d i a b a t i c b o m b c a l o r i m e t e r a n d t h e in v i t r o digestibility of the hay was determined according to the method described by T i l l e y a n d T e r r y (1963).

Statistical analysis D a t a w e r e a n a l y s e d u s i n g a s t a n d a r d single c l a s s i f i c a t i o n a n a l y s i s of v a r i a n c e followed b y d e s i g n e d c o m p a r i s o n a m o n g t h e t r e a t m e n t s m e a n s . S t a n d a r d errors of mean (SEM) were computed using the harmonic mean where numb e r s p e r m e a n d i f f e r e d ( S n e d e c o r a n d C o c h r a n , 1967).

237 RESULTS With the exception of bloat, which was persistent with starter GPN in Experiment 1, the health of the calves was generally excellent. There were a few cases of scouring, which responded to replacing the milk by electrolytes for a day, and a few cases of chills which cleared up without incident in Experiment 2. None of these seemed to be associated with any particular starter. One calf on starter GPN in Experiment 2 refused to drink milk from the outset and data from this calf were omitted. Liveweight gains for the grouppenned and individually-penned calves in Experiment 2 did not differ significantly from each other and the data were pooled in the analysis.

Digestibility and whole barley in feed and voided Apparent digestibility coefficients of dry matter, organic matter, energy, proximate constituents and digestible energy density (MJ kg-1 DM) for the three starters are presented in Table II. Significant differences in these digestibility coefficients were found in the case of fat, where starter GTPN was higher ( P < 0.001) than starter GP N and in N-free extract where starter WPT was lower ( P < 0.05) t h a n the others; otherwise differences failed to reach significance. Digestible energy ( M J kg -1 DM) in starter WPT was lower ( P < 0.05) than in the other starters. Whole barley voided in the faeces, expressed as a percentage ( + SE ) o f dietary barley on a DM basis, amounted to 4.27 + 1.03 % in Experiment 1 and 4.56 + 1.13% in Experiment 2. Intact barley grains represented 20.1% of total dietary barley ( DM basis ) in starter WPT (i.e., 79.9 % were broken or cracked in processing). Liveweights and intakes, both in absolute and per unit bodyweight, were lower in starters GPN and GTPN t h a n in W P w during the digestibility trial. This reflected the relative response to the three starters throughout the experiment.

Liveweight gain, intake and conversion efficiency Liveweight gain, intake and conversion efficiency for the three starters ( WPT, GPN, GTPN) are summarised in Table III (period of Experiment I when no long roughage was fed) and Table IV (Experiment 2 with calves bedded on straw and having free access to hay). In Experiment 1, intake and liveweight gains were significantly higher ( P < 0.05) in the post-weaning and entire periods when the barley fraction of the diet was unprocessed prior to incorporation into an 8-mm pellet (starter WPT ) than when the barley was ground prior to incorporation into 5-mm pencils (starters GPN and GTPN). Replacing cassava by tallow in the pencil (GPN

238 TABLE III Liveweights, average daily gain, average dry matter intake of calves fed three starter diets without long roughage (Experiment 1 ) Starter WPT

Number of calves Liveweights (kg) Initial Weaning (23 days) 62 days

SEM GPN

GTPN

6

6

6

50.0 60.0 103.3

51.3 59.5 95.5

50.0 57.2 89.2

Comparison WPT

GPN

V.

V.

others

GTPN

0.047 0.081 0.063

NS * *

NS NS NS

Daily gain (kg) Days 1-23 Days 24-62 Days 1-62

0.43 1.11 0.86

0.36 0.92 0.71

0.32 0.82 0.63

Dry matter intake (kg day- 1) Milk replacer Days 1-23

0.41

0.41

0.41

0.50 2.43 1.72

0.49 1.90 1.38

0.46 1.76 1.28

0.051 0.184 0.012

NS * *

NS NS NS

0.87 0.46 0.51

0.71 0.48 0.51

0.68 0.47 0.50

0.062 0.017 0.018

* NS NS

NS NS NS

Starter Days 1-23 Days 24-62 Days 1-62 Feed efficiency (kg gain kg- 1 starter DM) Days 1-23 Days 24-62 Days 1-62

v. GTPN) tended to reduce intake and liveweight gain, but differences failed to reach significance. Over a 62-day period, the calves fed starter W P w gained 14.1 and 9.1 kg more liveweight, respectively, than calves fed the pencils with (GTPN) or without tallow (GPN). Feed efficiency, expressed as the ratio of liveweight gain to starter intake, was not significantly affected by starter type except during the pre-weaning period when starter W P T gave the highest ratio (P<0.05). In Experiment 2, when long roughage was provided, liveweight gains were not significantly affected by starter type except during the post-weaning period when GTPN gave lower gains than GPN ( P < 0 . 0 5 ) . Intake of GTPN was also lowest ( P < 0.05) during this period (Table IV). Intake of starter W P T w a s significantly ( P < 0.01 ) higher than the others during the post-weaning period

239 TABLEIV Liveweights, average daily gain, average dry matter intake and feed efficiencies of calves fed three starters with access to long roughage (Experiment 2:) Starter

WPT

SEM

GPN

15(10)

14(9)

I5(10)

Liveweight (kg) Initial Weaning (23 days) 58 days

45.5 58.0 92.5

44.7 57.6 91.5

45.3 58.2 89.4

Daily gain (kg) Days 1-23 Days 24-58 Days 1-58

0.54 0.99 0.81

0.56 0.97 0.81

0.56 0.89 0.76

Dry matter intake (kg day -1) Milk replacer Days 1-23

0.41

0.41

0.41

0.53 2.23 1.56

0.45 2.07 1.43

0.44 1.78 1.25

0.14

0.15

0.19

1.11 0.45 0.53

1.19 0.46 0.55

1.25 0.48 0.59

0.42

0.44

0.45

Starter Days 1-23 Days 24-58 Days 1-58

WPT

GPN

V.

V,

others

GTPN

0.038 0.030 0.033

NS NS NS

NS * NS

0.037 0.090 0.063

NS ** **

NS * NS

0.052 0.013 0.016

NS NS NS

NS NS NS

GTPN

Number of calves1

Comparison

H~ Days 24-58 Feed Efficiency kg gain kg -1 starter DM Days 1-23 Days 24-58 Days 1-58 kg gain kg- 1DM 2 Day 24-58

1Numbers in parentheses refer to individually-fed calves on which intake and feed-efficiency data are based. 2Hay intake for individually-fed calves extrapolated from intake of group-fed calves, see text. a n d t h e e n t i r e period. F e e d c o n v e r s i o n r a t i o s were n o t s i g n i f i c a n t l y a f f e c t e d b y s t a r t e r type. H a y i n t a k e , m e a s u r e d f r o m D a y 36 t o 58 o f E x p e r i m e n t 2 w i t h t h e g r o u p - f e d

240

calves, amounted to 5.8, 6.6 and 9.7% of total DM intake for WPT, GPN and GTPN, respectively.

Rumen fluid pH, bloat and rumination R u m e n fluid pH was significantly higher at each of four sampling dates in the post-weaning period on starter WPw t h a n on the other starters in Experiment i when no long roughage was provided (Table V). Provision of long roughage for the final 10 days (Days 63-72) of Experiment 1 resulted in an increase in pH on all starter diets and no significant differences between starters were observed for samples taken o n Day 72. In Experiment 2, in contrast to Experiment 1, starter type had no significant effect on rumen fluid pH with the exception of samples taken on Day 51, when samples from calves receiving starter GTPN were significantly lower ( P < 0.05 ) than samples from calves fed GPN (Table V). Rumen pH values were consistently higher in Experiment 2 than the corresponding values in Experiment 1. In Table V, the variable number of calves sampled reflects the difficulty in obtaining satisfactory samples by the method used. Details of incidence, severity and timing of bloat are given in Table VI. Bloat was not observed with starter WPT in either Experiment 1 or 2 or with any of the starters in Experiment 2. In contrast to Experiment 2, there was persistent bloat with starter GPN in Experiment 1, 4 of the 6 calves on this starter being affected. Bloat also occurred with starter GTPN, but was less extensive and less severe. A case of mild (score 1 ) bloat occurred only once in the period in which long roughage was available in Experiment 1. Although the duration of rumination was not quantified, all calves in Experiment 2 were observed to ruminate apparently normally from the weaning stage onwards. Apparently normal rumination was also observed in calves fed starter WPT from weaning onwards in Experiment 1. Although some calves on starters GPN and GTPN (Experiment 1) were observed to attempt regurgitation, sustained chewing, characteristic of ruminating did not follow while the calves were deprived of long roughage. Apparently normal rumination was initiated in these calves during the final 10 days of the experiment when long roughage was provided. DISCUSSION The selection of the processing methods used for starters GPN and GTPN (Table I) reflected a common practice obtaining in Ireland at the time the work was initiated in the production of commercial calf starters, namely grind-

241 TABLE V Effect of starter type on mean ( ± SE) rumen fluid pH in Experiment I and 2 Starter

Comparison

WPT

GPN

GTPN

Experiment 11 Day 33 Number of calves Rumen fluid pH

5 5.58 ± 0.21

6 5.22 ± 0.15

Day 42 Number of calves Rumen fluid pH

3 5.60±0,11

Day 51 Number of calves Rumen fluid pH

WPT v. others

GPN v. GTPN

5 5.23 _+0.12

*

NS

5 5.11±0.13

5 5.22±0.14

**

NS

5 5.94_+0.32

4 5.31±0.16

5 5.25±0.18

***

NS

Day 58 Number of calves Rumen fluid pH

4 5.76±0.15

4 5.39___0.06

6 5.25±0.18

*

NS

Day 72 Number of calves Rumen fluid pH

6 6.91 ± 0.74

4 6.16 _ 0.45

5 6.30 ± 0.50

NS

NS

Experiment 21 Day 35 Number of calves Rumen fluid pH

5 6.17 ± 0.24

4 5.79 ± 0.31

4 5.89 ± 0.44

NS

NS

Day 44 Number of calves Rumen fluid pH

6 6.13 ± 0.40

6 5.99 ± 0.49

6 6.02 ± 0.41

NS

NS

Day 51 Number of calves Rumen fluid pH

6 6.68 ± 0.34

5 7.03 ± 0.30

6 6.26 ± 0.77

NS

*

1No supplementary long roughage available in Experiment 1 except from Days 63-72; calves in Experiment 2 had access to long roughage throughout. ing of cereals prior to their inclusion in a small pellet or pencil (5-mm die used in present study) often with the inclusion of tallow to increase the energy density. The processing method used for starter WPT (whole barley incorporated into an 8-mm pellet) attempted to retain the roughage characteristics of

242 TABLE VI Incidence, severity and date of bloat for different starters in Experiment 1 (Days 1-72)1 Starter WP T

GPN

GTPN

Number of calves

6

6

6

Number of calves bloating

0

4

1

Number of incidences

0

20

4

Incidence per bloat score (1-4) 1 2 3 4

0 0 0 0

5 5 3 7

1 2 1 0

Incidence X days Days 1-23 (pre-weaning) Days 24-36 Days 37-50 Days 50-62 Days 63-72

0 0 0 0 0

0 1 11 7 1

0 I 2 1 0

1No long roughage available except from Days 63-72 when calves were bedded on straw and had free access to hay.

the husk while at the same time ensuring satisfactory digestibility. Preston and Willis (1974) quoting unpublished work claimed that pellet size is critical when whole barley is fed without supplementary roughage: pellets < 6 m m diameter destroyed the roughage characteristics of the husk, while pellets > 10 m m gave insufficient breakdown for m a x i m u m digestibility. While the digestibility data in Table II may not fully support the concept o f " m a x i m u m digestibility" for starter W P w (whole barley extruded through an 8-mm die), in that digestibility coefficients were marginally lower for most nutrients and significantly so in the case of N-free extract relative to starter GPN (ground barley extruded through a 5-mm die), intake and liveweight gains ( Table III) were excellent with WPT both in absolute terms (Roy, 1980) and relative to GPN when no supplementary roughage was provided. That the digestibility coefficients for starter W P T w e r e only marginally lower than those for starter GPN is consistent with the low levels of whole grains voided in the faeces (Morgan and Campling, 1978; Vipond et al., 1985 ). In the present work, the whole barley voided in the faeces (4.27% Experiment 1 and 4.56% Experiment 2) is close to the value of 4.7% observed by Vipond et al. (1985) with ewes fed whole barley and hay, but considerably less t h a n the 45%

243 observed by Morgan and Campling (1978) using heifers varying in age from 7 to 16 m o n t h s and also fed whole barley and hay. In the latter work, there was a tendency for the digestibility of the starch of the whole barley to decline as the heifers aged. It should be noted that the data of Morgan and Campling (1978) and Vipond et al. (1985) refer to unprocessed barley, whereas in the present investigation the whole barley was extruded through an 8-mm die ( WP T) resulting in 79.9% of the barley grain being fractured prior to feeding. The relative contribution of processing, chewing and rumination to relatively high digestibility values found with W P T is n o t clear and deserves further investigation. When the results of Experiments 1 and 2 are considered together it is apparent t h a t either judicious processing (WPT) or the intake of relatively small amounts of long roughage (Experiment 2) were effective in protecting calves from many of the adverse effects (low intake, poor liveweight gains and a high incidence of digestive upsets) which were observed with starter GPN when no long roughage was provided in Experiment 1 (Tables III and VI). The almost complete elimination of bloat when calves were given access to long roughage at the end of Experiment i (Table VI) and the accompanying increase in rumen fluid p H (Table V) further illustrates the importance of roughage in maintaining normal rumen function and the fact that calves can adapt rapidly to the inclusion of long roughage in the diet (Stobo et al., 1966; Warner et al., 1973; Leek, 1983). The rumen fluid p H levels recorded when the calves were deprived of long roughage in Experiment I (Table y ) are low relative to what might be considered desirable for normal rumen function (Hungate, 1966, Leek, 1983), but are consistent with m a n y reports for calves on comparable dietary regimes (Kay et al., 1969; Fisher et al., 1985). It is difficult to disentangle the relative contributions of the low rumen fluid pH values and lack of coarse fibre to the poor performance (low intake, low liveweight gains and high incidence of bloat) which were obtained with starter GPN in Experiment 1 (Tables IH, V and VI) relative to starter WPT, which was of identical composition. Kay et al. (1969) considered low rumen fluid p H to be the primary cause of rumen lesions in calves fed high barley diets. In addition to raising rumen fluid pH through increased rumination and enhanced saliva production, coarse fibre may be important for normal rumen motility and eructation. Daniels and Colvin (1963) associated decreased r'dmen motility and a high incidence of bloat with feeding milled hay; replacing the milled hay by long hay restored rumen motility and eliminated bloat. In contrast to the results of Daniels and Colvin (1963) where frothy bloat was recorded, the calves on GPN in the present study seemed to suffer from free gas type of bloat which was readily relieved by stomach tube. The low intake, reduced liveweight gain and high incidence of bloat which was obtained on the pencils ( GP N) relative to the whole barley pellet (WPT) in Experiment 1 should not be taken as incriminating pencils per se, but rather should be considered in the context of the experiment, i.e., diets containing a

244 high level of potentially readily degradable starch without supplementary roughage. In these circumstances, retaining the integrity of the husk (WPT) resulted in significantly higher rumen fluid pH values (Table V ), probably as a result of a reduced rate of starch fermentation, coupled with an increased buffering of saliva from increased rumination. In contrast to Experiment 1, WP w and GPN did not differ significantly in liveweight gain, feed efficiencies ( Table IV ) or rumen fluid pH values (Table V ) when long roughage was provided in Experiment 2. No satisfactory explanation can be offered at this stage for the higher intake of WPT relative to GPN in Experiment 2 (Table IV); it may reflect differences in palatability and relative hay intake. W h e n the results of Experiment 1 and 2 are considered together, it is obvious that processing of starters for calves should not be considered in isolation but rather in the context of the feeding programme as a whole. When no long roughage was provided in Experiment 1, GPN gave disappointing results in terms of intake, liveweight gain and incidence of bloat relative to WP w while in Experiment 2, when supplementary roughage was provided, both starters proved satisfactory in all the parameters measured. On the question of long roughage, it should be noted that many authors ( Kang and Leibholz 1973; Preston and Willis, 1974; Thomas and Hinks, 1982, 1983) consider that the voluntary intake of such roughage provided separately may not always be consistent w i t h optimising total energy intake and calf performance. Judged by digestibility and digestible energy, tallow-supplemented starter (GTPN) seemed to be well utilized (Table II). However, in terms of intake and liveweight gains, GTPN gave disappointing results relative to GPN (tallow replaced by cassava) in both experiments; differences being non-significant in Experiment 1 (Table III) and significant ( P < 0.05 ) in the post-weaning period in Experiment 2 (Table IV). These results are consistent with many reports in the literature where the responses from tallow have usually varied from slight, non-significant improvements to severe depression in both intake and liveweight gains (Johnson et al., 1956; Kay et al., 1970; Wrenn et al., 1979; Abdelgadir et al., 1984). The poor response from tallow in calf starters is in sharp contrast to the situation obtaining with older cattle fed high concentrate diets. From a review of 24 experiments in which dietary fat additions (mainly tallow) varied from 2 to 10%, Preston and Willis (1974) concluded that an improvement of ~ 9% in liveweight gain can be expected from 4-5% fat supplementation. Palatability, rather than energy density, seems to be the more likely reason for the low intake of GTPN in the present study. In a comparison involving energy density, Abdelgadir et al. (1984) recorded lower liveweight gains and intake when 1.57% animal fat was in the starter t h a n with an isocaloric starter containing soya-bean oil. In the present study, the palatability theory is consistent with the intake of hay being higher with GTPN than with GPN in Experiment 2 - - 9.7 versus 6.6% of total dry matter intake. If palata-

245 bility was the real cause of the low intake of GTPN it is of interest t h a t inclusion of 5% molasses and a flavour did not eliminate the effect. The lower incidence of bloat with GTPN t h a n with GPN (Table VI) may have been due to tallow having some specific effects on r u m e n function or to the reduced intake of fermentable carbohydrate with GTPN. In the authors' view, the latter is the more likely explanation since fat in calf starters and in other high concentrate diets seems to have a variable effect on the incidence of bloat ( J o h n s o n et al., 1956; Miller et al. 1959; P r e s t o n a n d Willis, 1974). It is concluded that: (i) neither energy density nor chemical analysis adequately describe the productive potential of calf starters, (ii) in m a n y situations the physical form of starters m a y be more i m p o r t a n t t h a n the chemical composition, (iii) with barley-based starters processing should be at the minimum consistent with adequate digestibility, a n d (iv) in view of the variable voluntary intake of roughages reported in the literature it would seem a prudent practice to ensure t h a t the starter is capable of maintaining normal rumen function in its own right in order to protect individual calves from digestive upsets whose voluntary intake of long roughage might otherwise be sub-optimal. ACKNOWLEDGEMENTS T h e authors are indebted to Messrs. J. Callan a n d J. Hegarty for chemical analyses, to Mr. A. M i n n o c k for care of the experimental animals and to K e r r y Co-operative Creameries, Ltd., Tralee for preparation of starters.

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