A comparison of digestibility of some concentrate feed ingredients in cattle and sheep

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1 Animal Feed Science and Technology 81 (1999) 167±174 Short communication A comparison of digestibility of some concentrate feed ingredients in cattle and sheep F.P. O'Mara a,*, J.E. Coyle a, M.J. Drennan b, P. Young a, P.J. Caffrey a a Department of Animal Science and Production, University College Dublin, Belfield, Dublin 4, Ireland b Teagasc, Grange Research Centre, Dunsany, Co. Meath, Ireland Received 16 October 1998; received in revised form 23 February 1999; accepted 12 April 1999 Abstract An experiment was carried out to compare the digestibility of five concentrate ingredients (barley, beet pulp, citrus pulp, maize gluten feed and grain screenings) in cattle or sheep, fed at 1.2 maintenance. Four wether sheep and four steers were fed each concentrate, which comprised 800 g/kg of the dietary dry matter (DM). The remaining 200 g/kg was a hay/soyabean meal mixture whose digestibility was determined simultaneously in another four sheep and cattle. Following diet introduction and adaptation, faeces were collected for a 10-day period. Across diets, there was no difference (p >0.05) between sheep and cattle in digestibility of organic matter (OM, and 0.78, respectively, standard error of the difference (s.e.d.), ), crude protein (0.586 and 0.577, respectively, s.e.d ), or neutral detergent fibre (0.632 and 0.628, respectively, s.e.d ). However, cattle digested the OM (0.749 vs , p <0.05, s.e.d ) of maize gluten feed better than sheep, but there were no significant differences (p >0.05) between sheep and cattle with any of the other four feeds. These results do not support previous conclusions that sheep digest concentrates better than cattle, but they do suggest that there are differences within specific feeds. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Digestibility; Concentrates; Cattle; Sheep 1. Introduction Most digestibility studies of ruminant feedstuffs have been carried out using sheep, because they are easier to handle and the amounts of feed and excreta involved are lower. * Corresponding author. Tel.: ; fax: address: frank.omara@ucd.ie (F.P. O'Mara) /99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S (99)

2 168 F.P. O'Mara et al. / Animal Feed Science and Technology 81 (1999) 167±174 As a result, digestibility data on many feeds are scant apart from that generated with sheep and the digestibility values assigned to feedstuffs in databases of nutritive value are mainly based on measurements carried out using sheep (e.g. INRA, 1989; NRC, 1989; MAFF, 1992). However, cattle consume far greater quantities of feedstuffs and the use of digestibility values derived using sheep requires the assumption that digestibility is the same with cattle and sheep. Many trials have been conducted to test this assumption over the past 100 years. On some occasions, digestibility for sheep vs. non-lactating cattle has been found to be equal (see, e.g. Watson et al., 1948; Wilkins et al., 1972; Lindgren, 1981), but on other occasions, differences were reported (see, e.g. Blaxter and Wainman, 1964; Blaxter et al., 1966; Leaver et al., 1969). The most comprehensive comparison is probably the analysis carried out by Cipolloni et al. (1951) using data compiled by Schneider (1947). This indicated that cattle tended to digest forages better than sheep, but sheep tended to digest concentrates better than cattle. Mertens and Ely (1982) reported that sheep digest high quality feeds better than cattle, but the opposite occurs with low quality feeds, and they put the crossover point at a dry matter (DM) digestibility of 660 g/kg. Other researchers have supported these findings (e.g. Playne, 1978; Aerts et al., 1984/85). An interpretation of the data lies in that sheep have a higher apparent digestibility with high quality feeds because of lower metabolic losses, but with low quality feeds cattle show higher apparent digestibility because of a better ability to digest fibre (Van Soest, 1994). However, most of the species comparisons have involved forages (see, e.g. Playne, 1978; Mertens and Ely, 1982) and there is less information concerning the effect of species on concentrate digestibility. The data of Cipolloni et al. (1951) only included eight concentrate feeds: barley, maize and oat grains, cottonseed feed, linseed oil meal, soyabean oil meal, potato flakes or flour, and wheat bran. Its usefulness is somewhat limited because it was not from comparative trials, but rather was a compilation of reported digestibility trials with sheep or cattle involving these feeds. Bines et al. (1988) reported that DM digestibility of a diet consisting of 900 g/kg of concentrate was 55 g/kg higher in sheep than in cattle when fed around 0.7 times maintenance. However, when fed at around 1.3 times maintenance, DM digestibility was 42 g/kg higher in cattle. The objective of this study was to determine the digestibility of a selection of concentrate feeds in cattle and sheep. The feeds ranged widely in composition and expected digestibility and they were fed at slightly above a maintenance level of feeding. 2. Materials and methods Twenty four Cheviot wether sheep and 24 steers (12 Friesian and 12 Charolais cross) were used in this experiment. The sheep were 7±9-months old and weighed, on average, 42.8 kg (SD Ð 3.12), and the cattle were 1.5 years old and weighed, on average, 477 kg (SD Ð 32.9). They were blocked (sheep on the basis of liveweight and cattle on the basis of breed and liveweight) and allocated at random to one of six diets. The diets were based on barley, citrus pulp, beet pulp, maize gluten feed, or grain screenings, and the sixth diet

3 F.P. O'Mara et al. / Animal Feed Science and Technology 81 (1999) 167± consisted of hay and soyabean meal in a ratio of 4 : 1. The overall feeding level was 800 g/day for the sheep and 6.25 kg/day for the cattle. The concentrate ingredients were fed at 800 g/kg of the diet with the remaining 200 g/kg being composed of the same hay : soyabean meal mixture as fed in the sixth diet. The digestibility of this latter diet was used to calculate the digestibility of the five concentrates by difference. The level of feeding was calculated to be 1.15 and 1.35 maintenance for cattle and sheep, respectively, when fed the barley-based diet (INRA, 1989). In the case of the citrus pulp diet, the sheep and cattle were fed an extra 50 and 400 g of soyabean meal daily, respectively, with a corresponding reduction in the amount of citrus pulp fed. The purpose of this was to increase the crude protein content (CP) of the diet to 100 g/kg in order to avoid any possible negative effects of a low dietary protein level on diet digestibility. The contribution of this additional soyabean meal to the faeces was calculated using digestibility coefficients for organic matter (OM), CP, and neutral detergent fibre (NDF) of 0.916, 0.891, and 0.826, respectively. These were the average of five samples of soyabean meal measured at University College Dublin around the time of this study. Digestibility was measured over 10 days following a 17-day acclimatisation period. The sheep were initially housed in individual, slatted pens and were moved to digestibility crates for the last three days of the acclimatisation period. The cattle were housed in individual tie-up stalls and were moved to the digestibility unit two days prior to faecal collection. Both, cattle and sheep were fed from the same batches of ingredients. The concentrates were given in two feeds daily. The hay was coarsely chopped and fed twice daily to the cattle and once per day to the sheep. All feed allowances for the sheep for the 10-day faecal collection period were weighed at the same time prior to the study and were sampled at that time. Feed for the cattle was weighed and sampled daily. Refusals, where present, were added back to the following day's feed if unsoiled or else were weighed and the DM determined. Faeces was weighed and sampled daily for the sheep and every two days for the cattle. Samples of feed, faeces and refusals were dried at 558C to a constant weight to determine the DM content. Feed and faeces samples were ground (1-mm screen) and analysed for ash (muffle furnace for 4 h at 5508C), CP (AOAC, 1980; Kjeldahl N 6.25), ether extract (AOAC, 1980; Soxhlet procedure), NDF (Van Soest and Wine, 1967), acid detergent fibre (ADF; Van Soest, 1973) and gross energy (Gallenkamp adiabatic bomb calorimeter). The procedures outlined by MAFF (1993) which included amylase to solubilise starch were used when determining the NDF content of barley. Following ADF determination, acid detergent lignin (ADL) was measured. The ADF residue was resuspended in 10% acid detergent solution, boiled for 5 min and washed. Twenty five millilitres of 72% H 2 SO 4 was added to the crucibles. After 3 h, the crucibles were filtered and washed until the entire acid residue was gone, and ADL was then determined. Ether extract, ADF and ADL were determined on feeds only. The digestibility in cattle and sheep was compared by ANOVA using the general linear models procedure of SAS (1985). When comparing the digestibility of the individual feeds in cattle or sheep, the s.e.d. associated with the interaction term, feed species, was used.

4 170 F.P. O'Mara et al. / Animal Feed Science and Technology 81 (1999) 167±174 Table 1 Chemical analysis of the experimental feedstuffs Barley Beet pulp Citrus pulp Maize gluten feed Grain screenings Soyabean meal Hay Crude protein (g/kg DM) Ash (g/kg DM) Ether extract, (g/kg DM) Neutral detergent fibre (g/kg DM) a Acid detergent fibre (g/kg DM) a Acid detergent lignin (g/kg DM) Gross energy (MJ/kg DM) a The cell walls of citrus pulp are high in pectin which is normally more soluble in neutral detergent solution than in acid detergent solution. 3. Results The chemical analysis of each of the feedstuffs is shown in Table 1 and the intakes of each after any refusals were taken into account are shown in Table 2. The amount of refusals was very low for all animals. There was a slight difference in the hay : soyabean meal ratio between sheep and cattle: 4.05 vs when expressed on a DM basis for the sheep and cattle, respectively, compared to the target of 4.0. However, this did not compromise the use of the digestibility of the hay : soyabean meal diet (the sixth diet) to determine the digestibility of the concentrate feeds by difference as within each species, the same hay : soyabean meal ratio was fed on each of the other five concentrate diets as in the sixth diet. When the data for the concentrates were examined as a group, the differences in digestibility were very small and not statistically significant (Table 3). Cattle digested the OM of maize gluten feed significantly (p <0.05) better than sheep, but the differences in CP or NDF digestibility were not significant (p >0.05), although they tended to be higher for cattle. Sheep tended to digest the hay/soyabean meal mixture better than cattle, but the differences were small. With barley, beet pulp, citrus pulp and grain screenings, none of the differences in digestibility between cattle and sheep were statistically significant (p >0.05). Table 2 Feed dry-matter intakes (g/kg 0.75 ) of sheep and cattle on each of the experimental diets Diet Sheep Cattle hay soyabean meal test feed hay soyabean meal test feed Barley Beet pulp Citrus pulp Maize gluten feed Grain screenings Hay/soyabean meal

5 F.P. O'Mara et al. / Animal Feed Science and Technology 81 (1999) 167± Table 3 Comparison of digestibility of organic matter (OM), crude protein (CP) and neutral detergent fibre (NDF) in cattle and sheep Sheep Cattle s.e.d. a Sig b All concentrates OM NS CP NS NDF NS Barley OM NS CP NS NDF NS Beet pulp OM NS CP NS NDF NS Citrus pulp OM NS CP NS NDF NS Maize gluten feed OM * CP NS NDF NS Grain screenings OM NS CP NS NDF NS Hay/soyabean meal OM NS CP NS NDF NS a Standard error of the difference. b Sig, Statistical significance; NS, not significant (p >0.05). 4. Discussion The similar concentrate digestibility between cattle and sheep found in this study is in contrast to the conclusions of Cipolloni et al. (1951), namely that sheep digested concentrates better than cattle. However, despite their conclusions, Cipolloni et al. (1951) only reported significant differences in ether-extract digestibility between sheep and cattle with no significant differences in digestibility of OM, CP, crude fibre or nitrogenfree extractive. There was a trend towards differences in total digestible nutrients (TDN) which would be consistent with the difference in ether-extract digestibility. Ether-extract digestibility was not measured in this study, because of the low level of ether extract in the concentrates used. The methodology of this study and that of Cipolloni et al. (1951) differed. In this study, a direct comparison, using the same batches of feedstuffs fed at the same level, was carried out, whereas the study of Cipolloni et al. (1951) was based on reports in the literature of digestion with cattle and sheep (Schneider, 1947), but not necessarily direct comparisons as in our study. Feeding level may have been substantially different and batches of feedstuffs would have differed. Cipolloni et al. (1951) made

6 172 F.P. O'Mara et al. / Animal Feed Science and Technology 81 (1999) 167±174 corrections for proximate composition in their statistical analysis but it is well recognised that there is a poor relationship between proximate composition and digestibility and recent detailed studies have confirmed this (Mulligan, 1997). The results of our study with concentrate ingredients have been confirmed in a further study at our Institutes (Woods et al., 1999). Although there was no significant difference between species in digestibility of the concentrates, when the individual concentrates were examined, cattle digested the OM of maize gluten feed to a greater extent than sheep. The difference of 25 g/kg was relatively small, but differences of this magnitude could be commercially important. A subsequent study at our Institutes (Woods et al., 1999) compared digestibility of a further two samples of maize gluten feed and also found their OM digestibility to be higher in cattle by a similar amount as in this study. Even though the differences in that study were not statistically significant, they support the results reported here that there is a difference between cattle and sheep in their ability to digest maize gluten feed. It is difficult to understand why this difference should occur. The sample examined in this study was fibrous and had a very high NDF content (529 g/kg of DM). It has been reported that cattle are better fibre digesters than sheep (Van Soest, 1994), and that the difference in digestibility of forages with cattle compared to sheep (in favour of cattle) widens as the quality of the forage decreases (Rees and Little, 1980; Aerts et al., 1984/85). However, a sample of grain screenings which had a higher NDF content than the maize gluten feed was also examined in this study and there was no difference between sheep and cattle in its OM digestibility. The chemical composition of the feedstuffs used were normal and comparable to values found in other databases (e.g. INRA, 1989; NRC, 1989; MAFF, 1992). However, the digestibility of maize gluten feed was substantially lower than reported in any of the above-mentioned publications. In a subsequent study (Cronin et al., 1997), the digestibility of eight maize gluten feed samples was measured with sheep under conditions similar to this experiment and the mean OM digestibility was (SD = ). The samples measured in this study and by Cronin et al. (1997) may have differed from the samples on which the results of INRA (1989), NRC (1989) and MAFF (1992) are based due to changes in the manufacturing process in the intervening period leading to higher proportions of the lower digestibility fractions of the maize grain in our maize gluten feed samples. However, there was no evidence of such changes in the chemical composition. 5. Conclusions This study does not support the contention that sheep are better digesters of concentrates than cattle, or that cattle digest high-fibre feeds better than sheep while the opposite occurs with low-fibre feeds. However, there was evidence that there may be some feed-dependent differences, because in this study, cattle digested maize gluten feed better than sheep.

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