Frequency of concentrate supplementation for cattle fed barley straw ...

Frequency of concentrate supplementation for cattle fedbarley straw. 1. Effect on voluntary intake, ruminalstraw disappearance, apparent digestibility andheat productionR. C. Tellier 1 , G. W. Mathison 1 , E. K. Okine 1 , D. McCartney 2 , and R. Soofi-Siawash 11 Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta,Canada T6G 2P5 (e-mail: erasmus.okine@ualberta.ca); and 2 Agriculture and Agri-Food Canada,Lacombe Research Centre, 6000 C&E Trail, Lacombe, Alberta, Canada T4L 1W1.Received 28 July 2003, accepted 10 March 2004.Tellier, R. C., Mathison, G. W., Okine, E. K., McCartney, D. and Soofi-Siawash, R. 2004. Frequency of concentrate supplementationfor cattle fed barley straw. 1. Effect on voluntary intake, ruminal straw disappearance, apparent digestibilityand heat production. Can. J. Anim. Sci. 84: 455–465. Five ruminally cannulated crossbred steers (474 ± 30 kg) were fed dietscontaining 70% barley straw and 30% concentrate in an unbalanced 5 × 5 Latin square design experiment to investigate the effectsof frequency of feeding barley grain-based concentrates (daily, alternate days or every third day) with different dietary protein(7.9 and 11.5%) on voluntary intake of straw, ruminal disappearance of straw, apparent digestibility, and heat production. Neitherfrequency of feeding nor dietary protein concentration influenced voluntary intake of straw, nor did cattle eat differing amounts ofstraw on days when concentrate was fed in comparison with days when concentrate was not fed. Protein supplementation increased(P < 0.01) 24-h ruminal straw disappearance, but did not affect disappearances at other times. Concentrate feeding frequency hadno influence on rate of ruminal disappearance of straw. Apparent digestibilities of dry matter, gross energy, acid detergent fibre(ADF) and crude protein were 5, 6, 8 and 33% higher (P < 0.05), respectively, in diets containing the high-protein concentrate,but were not affected by frequency of concentrate feeding. Heat production (kJ kg -0.75 ) tended to be reduced (P = 0.06) by 4% insteers fed concentrate on alternate days in comparison with steers fed concentrate daily. Dietary protein concentration had no influenceon heat production even though digestible energy intake was 10% higher when the high protein concentrate diet was fed. Itwas concluded that concentrate can be fed every second day without any negative impact on intake and digestibility, with a possiblebenefit of a reduction in energy lost as heat. More research, however, is required to study the feasibility of feeding concentrateevery third day.Key words: Cattle, straw, protein, feeding frequency, digestion, heat productionTellier, R. C., Mathison, G. W., Okine, E. K., McCartney, D. et Soofi-Siawash, R. 2004. Fréquence des apports de concentrépour les bovins nourris de paille d’orge. 1. Incidence sur l’indice de consommation, la disparition de la paille dans le rumen,la digestibilité apparente et la production de chaleur. Can. J. Anim. Sci. 84: 455–465. Cinq bouvillons hybrides (474 ± 30 kg)canulés au rumen ont reçu un régime composé à 70 % de paille d’orge et à 30 % de concentré dans le cadre d’une expérience encarré latin 5 × 5 non équilibré qui devait préciser les effets de la fréquence à laquelle un concentré d’orge à teneur variable en protéines(7,9 et 11,5 %) était servi (tous les jours, un jour sur deux ou aux trois jours) sur l’indice de consommation de la paille, ladisparition de cette dernière dans le rumen, la digestibilité apparente et la production de chaleur. Ni la fréquence ni la concentrationde protéines n’ont d’influence sur l’indice de consommation de la paille et les animaux ne mangeaient pas une quantité différentede paille les jours où on leur donnait le concentré. Le supplément de protéines augmente (P < 0,01) la quantité de pailledisparue du rumen au bout de 24 heures, mais n’affecte pas le volume de paille digérée dans d’autres laps de temps. La fréquenceà laquelle le concentré est distribué n’influe pas sur la vitesse de disparition de la paille dans le rumen. La digestibilité apparentede la matière sèche, de l’énergie brute, des fibres au détergent acide et des protéines brutes s’accroît respectivement de 5, 6, 8, 8et 33 % (P < 0,05) avec le concentré le plus protéique, mais la fréquence à laquelle ce concentré est servi n’exerce aucune influencesur ce plan. Les bouvillons recevant le concentré un jour sur deux ont tendance à produire 4 % moins (P = 0,06) de chaleur(kJ par trois quarts de kilo) que ceux le recevant tous les jours. La concentration de protéines dans l’aliment n’agit pas sur la quantitéde chaleur produite,même si les animaux recevant le concentré très protéique absorbent 10 % plus d’énergie digestible. On enconclut qu’on pourrait servir le concentré un jour sur deux sans répercussion négative sur l’indice de consommation et la digestibilité,avec une éventuelle diminution de la quantité d’énergie perdue sous forme de chaleur. Des recherches plus poussées s’imposentpour établir la faisabilité d’un régime avec apport de concentré un jour sur trois.Mots clés: Bovins, paille, protéines, fréquence des repas, digestion, production de chaleurAbbreviations: BW, body weight, DM, dry matter; ADF, acid detergent fibre; Low-1, low protein concentrate fed daily; Low-2,low protein concentrate fed on alternate days; High-1, high protein concentrate fed daily; High-2, high protein concentrate fed onalternate days; High-3, high protein concentrate fed every third day; NDF, netural detergent fibre455

456 CANADIAN JOURNAL OF ANIMAL SCIENCEAn Alberta study found that provision of winter feed represented33% (range 17 to 48%) of input costs in cow-calfproduction systems in 1998 (Alberta Agriculture, Food andRural Development 2003). Feeding cereal straw can reducethe cost of feeding pregnant cows in the winter. Major concernswith feeding straw are low voluntary intake, low proteincontent, poor digestibility, low mineral and vitaminconcentrations, and slow passage rate (Anderson 1978).Provision of supplemental feeds to straw-based diets isexpensive, however, thus cattle producers in westernCanada and western United States are studying the feasibilityof reducing frequency of providing supplemental feedsto less than once daily as a cost-cutting measure.Research concerning infrequent feeding of supplementalfeeds has yielded variable results. Voluntary intake anddigestibility were not influenced by frequency of supplementationin studies of Chase and Hibberd (1989) and Huntet al. (1989) whereas Collins and Pritchard (1992) reportedan 8% decrease in dry matter (DM) intake when steer calveswere fed soybean meal and corn gluten meal supplementson alternate days rather than daily. Beaty et al. (1994)reported that straw intake was decreased when cattle werefed concentrate three times rather than seven times weeklybut the digestibility of neutral detergent fibre (NDF) wasincreased. Variable results have also been reported withrespect to animal performance. McIlvain and Shoop (1962),who both fed a high protein supplement daily or every thirdday, and Huston et al. (1999) did not detect any detrimentaleffect of reduced frequency of feeding on weight changes.However Collins and Pritchard (1992) and Beaty et al.(1994) found negative effects of reduced feeding frequencyon weight changes.The variable conclusions arrived at by researchers withrespect to the effect of reduced frequency of feeding supplementalfeeds may be due to the differing dietary protein contentsand feedstuffs used and the length of time betweenfeeding. It is known, for example, that the addition of a feedto a diet may influence the digestibility of another feed, andthat feed type may influence these “associative effects”. ThusKay et al. (1968) reported that the digestibility of straw wasnot reduced when a barley straw diet was supplemented withbarley grain, whereas digestibility of NDF was decreasedwhen sorghum grain was added to an ammoniated wheatstraw-based diet in the study of Fike et al. (1995). In an examinationof the literature it became apparent that no informationon feeding concentrates less frequently than once daily isavailable with respect to: (1) barley straw, and (2) the energeticefficiency of cattle, as assessed through measurementsof heat production. For these reasons, and because theresponses to reduced frequency of feeding of supplementalfeeds are variable, this experiment was conducted to provideadditional information on reduced frequency of concentratefeeding with barley-straw-based diets. Alternate-day feedingof concentrates, or the extreme of every second day feedingof concentrates, was examined since further reductions infeeding frequency could probably not be defended nor recommendedcommercially with straw-based diets.The objectives of this study were to investigate thehypotheses that the provision of concentrates containing lowand high protein levels on alternate days or concentrate withhigh protein level every third day would have no influenceon voluntary intake of barley straw, in vivo digestibility, orheat production of steers.Additional information concerning liquid and particulatedilution rates in the rumen and ruminal metabolites was alsoobtained (Tellier et al. 2004).MATERIALS AND METHODSAnimals, Feed and Feeding RegimenFive crossbred steers (474 ± 30 kg) were used in the 5 × 5Latin square experiment to examine the effects of frequencyof feeding barley-grain-based concentrates with straw-baseddiets on voluntary straw intake, ruminal degradability ofstraw, diet digestibility and efficiency of energy use. Theexperiment was conducted at the Laird McElroyEnvironmental and Metabolic Centre, University of Alberta,Edmonton, Alberta, Canada. At least 90 d before the experiment,the steers were fitted with 10-cm i.d. soft ruminal cannula(Bar Diamond, Parma, ID) as described by Tellier et al.(2004). All animals were cared for in accordance with theguidelines of the Canadian Council of Animal Care (1993).Steers were offered barley straw (Lacombe, six-row) ad libitumalong with five different concentrate feeding treatments asfollows: (1) low protein concentrate fed daily (Low-1), (2) lowproteinconcentrate fed every second day at two times the dailyrate (Low-2), (3) high-protein concentrate fed daily (High-1),(4) high-protein concentrate fed every second day at two timesthe daily rate (High-2), (5) high-protein concentrate fed everythird day at three times the daily rate (High-3). The amount ofconcentrate was calculated as 30% of the total as-fed intake ofthe previous week. Steers were also provided with free accessto fresh water and trace-mineralized salt blocks. The straw waschopped in a tub grinder (New Holland Model 390, Sperry,New Holland, PA) to approximately 6 cm in length.Composition of the concentrate mixtures and straw are summarizedin Table 1. The straw contained 5.3% crude protein,76.9% NDF, and 52.6% ADF. Straw was offered ad libitum insuch amounts as to maintain approximately a 10% weighback.Concentrates were offered at 0900 on the days that they wereprovided. All of the steers were allowed to consume the concentratebefore the straw was offered (normally within 0.5 h).On those days when animals were not fed concentrates, strawwas offered at 0900. Not all of the concentrate was consumedin the time allotted on some occasions. In such cases, straw wasadded on top of the concentrate.Each period was designed to be 31 d in length, althoughdue to practicalities of scheduling facilities and equipment,actual periods ranged from 26 to 35 d. There was a 14-dadaptation period prior to sampling. Voluntary feed intakemeasurements were obtained during days 15 to 20. Duringthis time, nylon bags were also incubated in the rumen andfaecal “grab” samples were obtained for calculation ofdigestibility. Indirect calorimetry measurements were madebetween days 21 and 31.Animals were weighed before each period. Orts wereremoved and weighed prior to feeding. Samples of straw,concentrates, and orts were taken daily during day 15 to day

TELLIER ET AL. — CONCENTRATE SUPPLEMENTATION FOR CATTLE FED BARLEY STRAW 457Table 1. Concentrate formulation and nutrient composition of straw and concentratesLow-proteinHigh-proteinComponent Straw concentrate concentrate SE z ProbabilityIngredients (% as-fed)Barley, dry rolled 97.8 64.4Canola meal 32.0Urea 1.4Fortified salt 2.0 2.0Vitamin ADE premix 0.2 0.2Composition (DM basis)Crude protein (%) 5.3c 14.1b 24.6a 1.02

458 CANADIAN JOURNAL OF ANIMAL SCIENCEChemical AnalysisCrude protein was determined on approximately 100-mgsamples of feed and faeces using a nitrogen analyzer (LECOModel FP-428, St. Joseph, MI). Neutral detergent fibre wasdetermined according to the procedure of Van Soest et al.(1991) without amylase or sodium sulphite. The Associationof Official Analytical Chemists (1997) procedure #973.18was used for the determination of ADF. Fibre analysis wasconducted using an ANKOM 200 Fiber Analyzer (ANKOMTechnology Corporation, Fairport, NY) with filter bags.Lignin was measured with the 72% sulphuric acid procedureof Goering and Van Soest (1970). Gross energy was measuredwith a Parr adiabatic bomb calorimeter (ParrInstrument Co., Inc. Moline, IL).Statistical AnalysisMean concentrate and straw intakes over the 6-d period foreach animal, ruminal straw DM disappearance, apparentdigestibilities and heat productions were analyzed as a 5 × 5Latin Square design using the GLM procedure of SAS (SASInstitute, Inc. 1988). Treatments (n = 5), animals (n = 5) andperiods (n = 5) were the main sources of variation. One animal(High-1 diet) was not included in analyses of straw DMintake because of a brief illness during one period. Meanswere separated using the Student-Newman-Keul’s test (SASInstitute, Inc. 1988). Comparisons between both dietary proteincontent of concentrates and frequencies of feeding concentrateswere examined using the GLM procedure of SAS(SAS Institute, Inc. 1988) with only the Low-1, Low-2,High-1, and High-2 treatments being considered in thesecomparisons. Ruminal straw DM disappearances (24, 48and 72 h) were examined by a repeated measures analysis(SAS Institute, Inc. 1988), with time as the repeated measure.The effect of days when concentrate was fed versusdays when concentrate was not fed was determined withineach dietary treatment, with days (n = 2 or 3) and animals(n = 5) as sources of variation.RESULTSFeed IntakeMean daily DM intakes of straw and concentrate and totalintake over the experimental period are outlined in Table 2.Straw intake when the low-protein concentrates were fed(5.55 kg d –1 ) was similar to straw intake when the high-proteinconcentrates were fed (5.39 kg d –1 ). Mean daily strawintake when concentrate was fed daily was 5.45 kg in comparisonwith the intake of 5.49 kg in steers fed concentrateon alternate days (P = 0.99). The amount of concentrateoffered was calculated as 30% of feed intake the previousweek, and was dependent on the amount of straw eaten.Percentages of concentrate in the diet were 31, 27, 33, 31and 31% for steers on the Low-1, Low-2, High-1, High-2and High-3 treatments, respectively, which differed slightlyfrom the targeted 30%. Thus, in contrast with straw intakes,there were differences (P < 0.05) in daily concentrateintakes between treatments; steers fed the low-protein andhigh-protein diets consumed 2.27 and 2.53 kg d –1 , respectively.Also, steers fed straw daily and on alternate daysconsumed 2.52 and 2.29 kg d –1 , respectively. TheseTable 2. Effect of dietary regimen z on mean daily dry matter intake over the experimental periodProtein concentration contrast for Frequency of feeding contrast for steersIndividual treatmentssteers fed daily or every 2 d fed concentrate daily or every 2 d Low protein High proteinLow High SE y P x 1 d 2 d SE y P x 1 d 2 d 1 d 2 d 3 d SE y P xSteer wt (kg) 474 473 2.9 0.70 474 473 2.9 0.92 476 471 470 474 486 4.1 0.12Straw DMkg 5.55 5.39 0.135 0.59 5.45 5.49 0.135 0.99 5.53 5.56 5.34 5.42 4.90 0.191 0.17% BW w 1.18 1.15 0.031 0.70 1.16 1.18 0.031 0.84 1.18 1.18 1.14 1.17 1.04 0.044 0.20g kg BW -0.75 54.8 53.2 1.23 0.49 53.8 54.2 1.27 0.92 54.5 55.1 53.0 53.4 47.7 1.790 0.08Concentrate DMkg 2.27b 2.53a 0.070 0.03 2.52a 2.29b 0.070 0.04 2.45ab 2.10b 2.60a 2.48ab 2.21ab 0.098 0.03% BW 0.48b 0.54a 0.014 0.02 0.54a 0.49b 0.014 0.04 0.52a 0.45b 0.55a 0.53a 0.47ab 0.020 0.02g kg BW -0.75 22.5b 25.0a 0.646 0.03 25.0a 22.5b 0.646 0.03 24.3ab 20.7b 25.8a 24.3ab 21.5b 0.913 0.02Total DMkg 7.82 7.92 0.145 0.52 7.97 7.78 0.145 0.30 8.00a 7.66ab 7.95a 7.90a 7.11b 0.205 0.05% BW 1.66 1.69 0.032 0.43 1.69 1.66 0.032 0.49 1.70 1.63 1.69 1.70 1.51 0.045 0.56g kg BW -0.75 77.3 78.2 1.255 0.60 78.8 76.8 1.255 0.28 78.8a 75.8a 78.7a 77.7a 69.2b 1.779 0.02z Low- or high-protein concentrate fed daily, every 2 d, or every 3 d.y Standard error mean is based upon five animals per mean for individual treatments and ten animals per mean for contrasts.x Probability.w Body weight.a, b Means not followed by the same letter differ (P < 0.05).

TELLIER ET AL. — CONCENTRATE SUPPLEMENTATION FOR CATTLE FED BARLEY STRAW 459Fig. 1. Effect of days after concentrate feeding on voluntary straw DM intake of steers. Fed, Day-1 and Day-2 refer to day of concentratefeeding, 1 d after concentrate fed and 2 d after concentrate fed, respectively. Vertical bars are pooled standard errors. Probabilities of treatmentdifferences from repeated measures analyses were 0.74, 0.23 and 0.35 for Low-2, High-2 and High-3 dietary regimens, respectively.unplanned for and unexpected differences were related todifferences in straw offered which was not consumed. Steersfed the low-protein concentrate diets consumed 7.82 kg d –1of total DM, which was similar (P = 0.52) to the 7.92 kg d –1of those fed the high-protein concentrate diets. Intakes oftotal DM were similar (P = 0.30) in steers fed concentratedaily (7.97 kg d –1 ) and those fed concentrate on alternatedays (7.78 kg d –1 ).The effect on straw intake of whether or not concentrate wasfed on a particular day is examined in Fig. 1. Straw intakes didnot differ between the days on which concentrate were fed andnot fed for the Low-2, High-2 and High-3 treatments.Ruminal Disappearance of Barley StrawRuminal disappearances of straw at 24, 48, 72 h and themeans of these times are shown in Table 3. Mean disappearancesof straw DM at 24, 48 and 72 h were 39.2, 50.3and 55.2% (P < 0.01), respectively.After 24 h incubation, straw disappearances were 37.0,37.9, 42.1, 40.1, and 40.1% for Low-1, Low-2, High-1,High-2, and High-3, respectively (P = 0.02). The differencewas due to protein content of the diet; feeding the high-proteinconcentrate compared to feeding the low-protein concentrateincreased (P < 0.01) 24-h disappearance of straw by10%. After 72 h, straw disappearance tended (P = 0.07) tobe lower when steers were fed the high-protein concentrateevery third day (High-3 diet) than when they were fed thisconcentrate daily (High-1 diet). No other differences instraw disappearance were detected between individual treatmentsdue to protein level or frequency of feeding.Day on which bags were placed in the rumen had no effecton straw DM disappearance in any treatment. With the Low-2diet DM disappearances on the day after concentrates were fedin comparison with the day they were fed were 9, 5 and -3%higher (P = 0.27) after 24, 48 and 72 h incubation, respectively.Corresponding values for the High-2 diet were 3, 0 and 3%(P = 0.47). With the High-3 diet after 24 h of incubation, DMdisappearances were 5 and 2% higher on day 1 and day 2 afterfeeding than they were on the day concentrate was fed, whereascorresponding values after 48 and 72 h incubation were 1and –7% and –5 and –5% respectively (P = 0.53).In Vivo DigestibilityMean DM, NDF, ADF, protein and energy digestibilitiesacross all treatments were 56, 58, 45, 58 and 55%, respectively(Table 4). Digestibilities of DM, ADF, protein andenergy were 5, 8, 33, and 6% higher (P < 0.05), respectively,when steers were fed the high-protein concentrate ratherthan the low-protein concentrate. Similarly, the digestibleenergy contents of the high-protein diets were 7% higherthan that of the low-protein diets. There was no indicationthat digestibility was affected by feeding concentrate lessfrequently than once daily.Digestibility estimates were also made for days on whichconcentrates were fed and days when concentrates were notfed using mean daily faecal lignin concentrations and themean DM intake over the 6-d period in the calculation. Theonly difference detected was for crude protein digestibilityin steers fed concentrate once every 3 d (High-3 diet) wherethe protein digestibility was 13% higher (P = 0.03) on the

460 CANADIAN JOURNAL OF ANIMAL SCIENCETable 3. Effect of dietary regimen z on ruminal disappearance (%) of barley strawProtein concentration contrast for Frequency of feeding contrast forIndividual treatments ysteer fed daily or every 2 d steer fed daily or every 2 d Low protein High proteinIncubation time Low High SE x P w 1 d 2 d SE x P w 1 d 2 d 1 d 2 d 3 d SE x P w24 h 37.5b 41.1a 0.65

TELLIER ET AL. — CONCENTRATE SUPPLEMENTATION FOR CATTLE FED BARLEY STRAW 461Table 5. Relationships between ruminal dry matter disappearance (%) of straw dry matter with apparent energy digestibility and digestible energycontent of strawEquation SE R 2 ProbabilityDigestibility of straw energy z (%)Both concentrates y-1.07 + 1.172 (24 h disappearance) 6.30 0.25 0.01-3.20 + 0.960 (48 h disappearance) 6.57 0.18 0.02-0.15 + 0.821 (72 h disappearance) 6.84 0.12 0.06Low protein concentrate y40.1 + 0.014 (24 h disappearance) 5.65 0.00 0.98-4.00 +0.893 (48 h disappearance) 4.95 0.14 0.167.99 + 0.590 (72 h disappearance) 5.15 0.24 0.06High protein concentrate y0.10 + 1.160 (24 h disappearance) 6.13 0.21 0.063.96 + 0.877 (48 h disappearance) 6.16 0.20 0.06-13.3 + 1.121 (72 h disappearance) 5.96 0.25 0.04Digestible energy content of straw y (MJ kg –1 )Both concentrates-0.10 + 0.215 (24 h disappearance) 1.20 0.23 0.01-0.57 + 0.178 (48 h disappearance) 1.24 0.17 0.020.05 + 0.151 (72 h disappearance) 1.30 0.11 0.07Low protein concentrate7.93 -0.010 (24 h disappearance) 1.08 0.00 0.94-0.57 + 0.162 (48 h disappearance) 0.96 0.11 0.181.64 + 0.1067 (72 h disappearance) 1.00 0.27 0.04High protein concentrate0.07 + 0.218 (24 h disappearance) 1.17 0.20 0.060.68 + 0.164 (48 h disappearance) 1.17 0.19 0.06-2.44 + 0.207 (72 h disappearance) 1.14 0.24 0.04z Range in gross energy digestibilities for straw in all diets, low-protein diets and high-protein diets were 29 to 59, 29 to 47 and 35 to 59%, respectively.Corresponding ranges in digestible energy contents were 5.3 to 10.9, 5.3 to 8.8 and 6.4 to 10.9 MJ kg –1 .y Numbers of observations for both, low-protein and high-protein concentrates were 24, 10 and 14, respectively.digestibility of the high-protein diets, digestible energyintakes were higher (P < 0.01) in steers fed the high-proteinconcentrate than in those fed the low-protein concentrate.Dietary protein intake, however, had no influence on theheat production of the steers. There were no differences indigestible energy intake between steers fed concentratedaily and those fed concentrates on alternate days; however,heat production (kJ kg -0.75 ) was 4% higher (P= 0.06) insteers fed concentrate daily.Heat productions on days when concentrates were fedwere compared with heat production on days when concentrateswere not fed within each dietary treatment (Fig. 2). Nodifferences were detected between days when concentratewas fed and days when no concentrate was provided.DISCUSSIONVoluntary Consumption of Straw-based DietsThe average protein content of six-row barley straw inAlberta in 1984-1994 was 5.4% (Alberta Agriculture, Foodand Rural Development 1997), suggesting that the barleystraw used in this experiment was of average quality.Voluntary consumption of straw averaged 1.18, 1.18,1.14, 1.17, and 1.04% of body weight (Table 2) for animalsfed the Low-1, Low-2, High-1, High-2 and High-3 diets,respectively. These straw intakes are similar to those ofZorrilla-Rios et al. (1991) who measured intakes of untreatedstraw as 1.08, 1.14, and 1.17% of body weight when animalswere supplemented with 0, 150, or 500 g d –1 soybeanmeal, respectively. Okine et al. (1993) reported daily barleystraw intakes of 1.5% of body weight when barley strawbasedand concentrate diets were fed. Beaty et al. (1994)reported a daily intake of wheat straw of 1.4% when animalshad concentrate supplied daily and 1.18% when concentrateswere supplied three times per week, the latter beingclose to our intakes. All of these straw intakes were obtainedindoors under controlled conditions and are generally lowerthan the barley straw intake of 1.5% of body weight of cowsmeasured by Weisenburger et al. (1977) in an outdoor winterfeeding trial. Mathison et al. (1981), however, reportedbarley straw intakes of 1.3% of body weight in an outdoorwinter feeding trial with cows.It is well accepted that protein deficiencies can decreasefeed intake (National Research Council 1996). In this study,however, protein supplementation did not increase voluntaryintake of straw. This was surprising since the intake ofrumen degradable protein was below requirements (Tellieret al. 2004) and rate of disappearance of straw in the rumen

462 CANADIAN JOURNAL OF ANIMAL SCIENCEFig. 2. Effect of days after concentrate feeding on heat production of steers. Fed, Day-1 and Day-2 refer to day of concentrate feeding, 1 dafter concentrate fed and 2 d after concentrate fed, respectively. Vertical bars are pooled standard errors. Probabilities of treatment differencesfrom repeated measures analyses were 0.13, 0.86 and 0.34 for Low-2, High-2 and High-3 dietary regimens, respectively.was reduced with the low-protein diet. With only five animals,however, we would not have been able to detect a differencein voluntary intake of less than 6% because thestatistical power of our experiment was limited.Supplemental protein did not increase straw intake in thestudy of Weisenburger and Mathison (1977) but in manyother studies it has (Mathison et al. 1981; Sunvold et al.1991; Beaty et al. 1994).Neither straw intake nor total intake was affected whensteers were fed concentrate less frequently than once daily,although straw intake was numerically 8% less when thehigh-protein concentrate was provided every third day thanwhen it was provided daily (Table 2). Supplementing lowqualityforage-based diets less than once daily has beenshown to have a variable effect on intake. Hunt et al. (1989)reported similar intakes in steers fed grass hay (6.6% crudeprotein) and provided with a cottonseed supplement every 12,24, or 48 h. Chase and Hibberd (1989) did not detect a differencein intake between cows fed low-quality grass hay (5%crude protein) and supplemented either a low level (1.4 kgdaily equivalent) or a high level (2.0 kg daily equivalent) ofcorn daily or on alternate days. In contrast, in the study ofBeaty et al. (1994), intake of wheat straw fell (P < 0.01) from1.42% for animals supplemented daily to 1.18% body weightfor animals fed three times per week with a soybeanmeal/sorghum grain supplement. Collins and Pritchard (1992)reported an 8% decrease in intake with alternate day feedingof protein supplements but also concluded that DM intakewas variable in response to protein source and frequency.The observation that straw intake did not differ betweendays when concentrate was fed and days when concentratewas not fed (Fig. 1) is of interest. It can be concluded thatsteers did not change their intake behaviour in anticipationof changes in availability of concentrate. Also, similar strawintakes across days demonstrated that the steers were able tophysiologically adjust to the reduced nutrient intake on dayswhen concentrate was not fed, probably because the longresidence time in the rumen tends to even out nutrient supplyto the animal over time.In Situ Disappearance of StrawThe polyester bags contained 20 to 30 mg of sample cm -2 ofbag surface. This relatively high weight to surface area ratiowas used by 16% of researchers in the summary of Vanzantet al. (1998). This is higher than the recommended value of10 mg cm -2 , but according to Vanzant et al. (1998), theeffect of weight per surface area is reduced when slowlydegrading forages such as straw are used. The use of a 2-mmscreen for grinding and a 50-µm pore size are consistentwith recommendations of Vanzant et al. (1998).There was a 10% increase (P < 0.01) in ruminal disappearanceof straw after 24 h incubation when the high-proteinconcentrates were fed in comparison to the low-proteinconcentrates. Such a difference was not apparent at either 48or 72 h, which suggests that the rate, rather than the extentof disappearance was influenced by dietary protein. Hunt etal. (1989) measured an increase in ruminal degradability offorage with protein supplementation.

TELLIER ET AL. — CONCENTRATE SUPPLEMENTATION FOR CATTLE FED BARLEY STRAW 463Frequency of provision of concentrate did not influence 24,48, or 72 h ruminal disappearance of straw (Table 1). Theseresults are consistent with those of Hunt et al. (1989) whofound that in situ fibre degradability of grass hay was notaffected by feeding cottonseed meal every 12, 24, or 48 h.Digestibility of DietsThe mean apparent DM digestibility was 57% and the meandigestible energy content of the diets was 10.3 MJ kg –1 .According to National Research Council (1996) informationaverage barley straw and low-protein concentrate contained7.4 and 15.1 MJ kg –1 digestible energy, respectively. Usingthis information the calculated energy content of the lowproteindiet was 9.7 MJ kg –1 , which was similar to the 9.8MJ kg –1 actually obtained. Using the formula to calculatedigestible crude protein from dietary crude protein providedby National Research Council (1984), the low (7.9% crudeprotein) and high protein diets (11.5% protein), should havecontained 4.3 and 7.4% digestible protein, which correspondsto expected percentage protein digestibilities of 54and 65%. The measured digestibilities of protein for the lowand high diets were 49 and 65%, respectively. On the basisof these estimates, we have confidence that the digestibilitiesobtained with the lignin marker were quite accurate.Crude protein digestibilities were higher with the high-proteindiet (Table 4). This would be expected in light of the higherrate of ruminal disappearance with this diet. In addition,digestibilities of DM, ADF and energy were improved (P

464 CANADIAN JOURNAL OF ANIMAL SCIENCEincreased efficiency of energy use with less frequent provisionof nutrients because of increased energy costs associatedwith cyclical energy storage. In this regard, Hyltander etal. (1993) found a more pronounced response in heat production,and hence reduced energy assimilation, whenhumans were given six bolus-based intermittent infusions of60 min duration over a 24-h period rather than having nutrientscontinuously infused. Another alternative for considerationis that reduced frequency of feeding concentratesinfluenced heat production through a reduction in energycosts of eating and rumination. Such costs are substantial(Ferrell 1988). No measurements of eating and ruminatingtimes were made in this experiment. Significant relationshipswere, however, found between heat production andruminal acetic:propionic acid rations and branched-chainfatty acids, which are discussed in a companion report(Tellier et al. 2004).Weight changes should be impacted if cattle are more efficientwhen concentrates are fed less frequently. AlthoughMcIlvain and Shoop (1962), Brandyberry et al. (1992) andHuston et al. (1999) concluded that provision of supplementsless frequently than once daily had no influence on weightchanges, Collins and Pritchard (1992) and Beaty et al. (1994)measured a detrimental effect on weight changes. Intakes ofmetabolizable energy were not similar between treatmentgroups, however; thus it is difficult to determine energetic efficienciesfrom these weight change experiments.CONCLUSIONS AND IMPLICATIONSOur study supports earlier research where it was found thatstraw DM intake was not influenced by feeding concentratesless frequently than once daily. The observation that strawintake did not differ between the days when straw was orwas not fed suggests that more than one day is required forbehavioural and physiological adaptations to occur in voluntaryintake. In support of much of the previous research,frequency of provision of concentrates had no effect ondigestibilities of the diets, although digestibilities wereincreased with protein supplementation. The reduced heatproduction of the steers fed concentrate on alternate dayssuggests that these animals may have been more energeticallyefficient, but further studies are required to confirmthis observation. Although no significant differences wereobtained, there were indications that voluntary intake maybe reduced when concentrates are fed only every third day.It was concluded that concentrate may be fed every secondday without any negative impact on intake and digestibility,with the possible benefit of a reduction in energy lost asheat. More research, however, is required to study the feasibilityof feeding concentrate every third day.ACKNOWLEDGEMENTSThe authors gratefully acknowledge S. Melnyk and the staffat the Laird McElroy Environmental and MetabolismCentre, as well as V. Pagon, for their assistance with theproject. Financial Assistance was provided by AlbertaAgricultural Research Council, Alberta Agriculture Foodand Rural Development, and the National Sciences andEngineering Research Council.Aerts, J. V., De Brabander, D. L., Cottyn, B. G. and Buysse, F. X.1977. Comparisons of laboratory methods for predicting the organicmatter digestibility of forages. Anim. Feed Sci. Technol 2: 337–349.Alberta Agriculture Food and Rural Development. 1997. Tenyear average analysis of Alberta feeds 1984–1994. Edmonton, AB.[Online] Available http://www.agric.gov.ab.ca/livestock/feed/straw1.html [2001 Aug. 17].Alberta Agriculture Food and Rural Development. 2003. 1998weaned calf enterprise cost & returns analysis. 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