Vol. 5(1996): 399-412. Effects of physical treatment of barley and rapeseed meal in dairy cows given grass silage-based diets Pekka Huhtanen and Terttu Heikkilä Agricultural Research Centre of Finland, Institute ofAnimal Production, FIN-31600 Jokioinen, Finland Twenty-four Ayrshire cows were used to study the effects of physical treatment of barley, rapeseed meal (RSM) supplementation and heat-moisture treatment ofRSM on silage intake and milk produc- tion. Experimental design was a cyclic change-over with six dietary treatments. The treatments in a 2 x 3 factorial arrangement consisted of either untreated (UB) or heat-moisture treated barley (TB), given without protein supplementation (control) or with untreated or heat-moisture treated RSM. Grass silage was given ad libitum and the concentrates at a rate of 10 kg/d. For the RSM diets, 2 kg/d of the basal concentrate was replaced with either untreated or treated RSM. Treatment of barley decreased silage intake, the effect being greater when the supplement did not contain RSM. There was no effect on milk yield, but due to the lower milk fat content, energy cor- rected milk yield was lower in cows given TB than in those given ÜB. Feeding the TB diets was also associated with lower milk urea content, and with increased milk protein content but not protein yield. Faster initial rate of gas production in vitro suggested that the treatment of barley increased the rate of fermentation. Compared with the control diets, RSM supplementation significantly increased silage intake, milk yield, milk protein content and yields of all milk constituents. Heat-moisture treatment of RSM did not produce any further production response. Key words: milk production, feed intake, protein supplementation, digestibility, heat treatment ntroduction It is well established that increasing the protein concentration of supplements increases milk yield in cows given grass silage-based diets (Thomas and Rae 1988,Chamberlain et al. 1989, Tuori 1992). The responses can be attributed to increased silage DM intake, improved diet di- gestibility and increased supply of amino acids from the small intestine. However, physical and chemical treatments of protein supplements to increase the supply ofamino acids from the small intestine have often produced limited responses in animal production. Replacing grain mixture in the concentrate with rapeseed meal (RSM), the most important protein supplement for ru- minants in Finland, has consistently increased © Agricultural and Food Science in Finland Manuscript received June 1996 399 AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=K3L9ileY8yqNHFHo.cuPG7Cmvwef99lJWYmEZpA.9A3ydYpXWwAxvkbutMIOxhTe4Yq82t8LNrZY1hoZ0MXWv2vGPcccHcOIaFWaVhvIGLMfuzm6cv0LJmHngu8wSZa-WBXPlxTbRBvqjAvFHeL2k1FzITmHp1McHW12IShJ-RirvNRkms9yhNlfe2DIbL_eulGJX98fAsynWK4BKGTtaGaaEgpM120aALRhkP0Z5khr3hg3qg8lAKNFGprT9xvUci2vjf-cxX-1MptxabZroNlD84-An-vK49TCXM0slqqTbT5ruT1Q33xLnV7Gkx7GNXwD0lsaXfrLGtOG milk yield. However, reducing ruminal protein degradability of 00-varieties of RSM by heat- moisture treatment has not produced any further responses (Tuori 1992) despite an increase in the calculated supply of amino acids absorbed from the small intestine (AAT). Reducing ruminal protein degradability of grain supplements by either chemical or physi- cal processing offers another way to increase the supply of amino acids. Although cereal grains have a low crude protein content, they generally comprise a large proportion of concentrate mix- tures, which means that improvements in the protein value of grain could result in considera- ble increases in the supply of amino acids from the small intestine. Kassem et al. (1987) demos- trated some improvements in milk production when barley was treated with a formaldehyde reagent. Physical treatment of grain can be used to modify grain starch, which should increase microbial protein synthesis in the rumen (Cham- berlain et al. 1993). Heat treatmentcan produce complexes between starch and protein that are not digested by microbial enzymes (Dreher et al. 1984) and if these complexes are digested in the small intestine, the supply ofboth amino ac- ids and glucose could increase. The objective of our experiment was to ex- amine the effects ofphysical treatment to reduce ruminal protein degradability ofbarley and rape- seed meal (RSM) on milk production in cows fed grass silage ad libitum. Material and methods Animals The experimental animals were 24 Finnish Ayr- shire cows, of which 6 were in their first lacta- tion. The cows had calved 63 days (SE 4.0) be- fore the start of the experiment and their aver- age milk yield was 34.0 kg (SE 0.86) at the be- ginning of the experiment. The cows were fed and housed in individual stalls. Grass silage was given ad libitum in amounts ensuring refusal of about 10% of the amount offered. The concen- trate mixtures were given three times daily at 1.00, 13.00 and 16.30 h and the cows were milked twice daily at 6.45 and 15.30 h. Experimental design The experiment was conducted according to a cyclic change-over design (Davis and Hall 1969) with six treatments, four replicate blocks of six cows and four 3-week experimental periods. The cows were divided into blocks according to pre- trial milk yield and parity, and allocated at ran- dom to treatments and sequences of treatments. The six treatments in a 2 x 3 factorial arrange- ment consisted of two energy supplements [un- treated barley (UB) and heat-moisture-treated barley (TB)], each given without protein supple- ment (control), with untreated RSM or with treat- ed RSM. The control concentrateconsisted on a DM basis (g/kg) of either UB or TB (800) and molassed sugar beet pulp (200). For the cows given RSM diets, 200 g/kg of the basal concen- trate was replaced with RSM. On air-dry basis (870 g DM/kg), the concentrates were given at a rate of 10 kg/d throughout the experiment. The concentrate mixtures contained 36 g/kg ofa com- mercial mineral mixture containing (g/kg) Ca (213), P (46), Mg (33) and Na (93). Four late-lactation cows, each fitted with a rumen cannula, were used in a change-over de- sign with two periods of 14 days to study the effects of barley treatment on rumen fermenta- tion. The cows were given grass silage ad libi- tum and 2 kg/d of untreated RSM with 6 kg/d of either UB or TB. They were fed twice daily at 12 h intervals. Rumen samples were taken on the last day of each period before feeding and thereafter 8 times at 1 h intervals. Feeds The silage was made from a sward of second- cut meadow fescue (Festuca pratensis) - timo- 400 Huhtanen, P. & Heikkilä, T. Treated barley and rapeseed mealfor dairy cows AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 5 (1996): 399-412. thy (Phleum pratense). The silage was harvest- ed as direct-cut by a flail-type forage harvester and ensiled into a bunker silo of 200 t capacity. Formic acid-based additive was applied at en- siling at a rate of 5 I/t. The ingredients of the basal concentrates were crushed and mixed in the feed mill of the institute. RSM was weighed separately and mixed with the concentrate before feeding. Un- treated RSM was solvent extracted and ofFinn- ish origin (Raisio Ltd). Heat-moisture treated RSM was imported from Sweden, because for practical reasons it was not possible to transport RSM to Sweden for the treatment. The higher crude protein content of treated (Expro®) RSM was taken into account by making the concen- trates isonitrogenous. The treated barley was prepared from the same lot of barley that was fed untreated, by cooking at high temperature. Experimental procedure Feed intake and milk yield of individual cows were recorded daily. The results of the last sev- en days of each period were used for statistical analyses, and the feed samples forchemical anal- yses were collected during this period. Fresh si- lage samples were preserved frozen at -20°C for the analyses of silage fermentation characteris- tics. Milk samples were taken on four consecu- tive milkings on the last week of each period. The samples were analysed for fat, protein and lactose by an infra-red milk analyser. Live weight of the cows was recorded on two consecutive days at the beginning of the experiment and at the end of each period. The apparent digestibil- ity of the diets was determined by using acid insoluble ash as an internal marker (Van Keulen and Young 1977). Faecal samples were taken from all cows twice daily at 7.30 am and 4 pm on five consecutive days during the last week of each period. Ruminal protein degradability of the concentrate feeds was determined by nylon bag technique. The samples were incubated in the rumen of four cows for 0,3, 6, 12, 24 and 48 h. Efficient ruminal protein degradability (EPD) was calculated using the values of0.03 and 0.04/h for the passage rate of barley and RSM (Tuori et al. 1995). Cumulative gas production was measured from barley samples by a modifica- tion of the method of Theodorou et al. (1994). Chemical analyses Feed analyses were made using standard proce- dures. Silage DM content was corrected for the volatile losses according to Huida et al. (1986). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin were determined accord- ing to Robertson and Van Soest (1981). The pH ofthe silage and rumen fluid samples was meas- ured immediately. Ammonia-N (McCullough 1967) and volatile fatty acids (VFA) (Huida 1973) were measured both in silage and in ru- men fluid samples. The concentration of lactic acid in silage was determined by the method of Barker and Summerson (1941) and that ofwater soluble carbohydrates (WSC) by the method of Somogyi (1945). Milk fatty acid composition was analysed by gas chromatography (Antila and Kankare 1983,Karow et al. 1984) and milk urea content as ammonia (McCullough 1967) after hydrolyses by urease. Calculations and statistical analyses The content of metabolizable energy (ME) was calculated using the D-value determined in sheep for silage and from chemical composition and digestibility coefficients (Tuori et al. 1995) for the concentrate feeds. ME intake was also esti- mated from calculated intake of digestible OM (DOM) assuming ME content of 16 MJ/kg DOM. Milk energy content was calculated according to Tyrrel and Reid (1965). The efficiency of the utilization of ME for milk production was cal- culated ignoring the effect oflive weight change. The supply of amino acids absorbed from the small intestine (AAT) was estimated either by using EPD values determinedby nylon bag meth- 401 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Table 1.Chemical composition (g/kg dry matter) and calculated feeding values of the experimental feeds. Silage 1 Untreated Treated Untreated Treated barley2 barley 2 RSM RSM Dry matter (g/kg) 241 882 912 883 895 In dry matter Ash 87 66 63 78 79 Crude protein 133 126 122 366 409 Ether extract 50 17 19 39 32 Crude fibre 283 73 73 137 120 NEE’ 447 719 723 381 360 NDF 522 275 379 292 283 ADF 294 86 101 218 176 Lignin 29 17 23 78 66 EPD 4 (g/kg) 801 726 751 581 ME 5 (MJ/kg DM) 10.9 12.8 12.9 11.2 11.2 AAT6 (g/kg DM) 82 105 110 134 181 PBV 7 (g/kg DM) -6 -46 -57 158 134 1 In silage: pH 3.96; In DM (g/kg): WSC 28, lactic acid 62, acetic acid 16, ethanol 6; In total N (g/kg): ammonia N 30, soluble N 505. 2 A mixture of barley and sugar beet pulp (8:2). 3 Nitrogen free extracts. 4 Efficient protein degradability, rate of passage 0.03/h for barley and 0.04 for RSM. 5 Calculated from D-value determined in sheep for silage and from feed table digestibility coefficients for the concentrates. 6 The values determined by nylonbag method for concentrates and from feed tables (TUori et al. 1995) for silage. 7 Calculated using determined EPD values for the concentrates and a value of 0.85 for silage. od for the concentrate feeds and a value of 0.85 for silage (Tuori et al. 1995) or using EPD val- ues from Finnish feed tables (Tuori et al. 1995) for all feeds. The data were analysed with general linear models of the Statistical Analyses System (SAS Institute 1989). The model included the effects of block, cow (block), period, treatment and car- ry-over. The results for the production parame- ters are adjusted for the carry-over effects al- though all these effects were non-significant and negligible. The treatment effects were further separated into single degree comparisons of effects of barley treatment, RSM supplementation, RSM treatment, interaction between barley and RSM supplementation, and interaction between barley treatment and RSM treatment. Data from the rumen fermentation study was subjected to a split-plot analysis of variance for repeated measurements. Results The silage fed was of good fermentation quality in terms of low pH, low concentrations of fer- mentation acids and small proportion of ammo- nia N in total N (Table 1). Despite the relatively low crude protein content in the silage, the D- value determined in sheep was fairly high (681 g digestible OM/kg DM). Treatment of barley increased NDF content markedly, and also ADF content of the energy supplement. The treatment of both barley and RSM decreased ruminal pro- tein degradability, and consequently increased calculated AAT values. The results for feed intake and calculated ME and AAT consumption are shown in Table 2. Si- lage DM intake was higher (P<0.001) with the UB diets than the TB diets (11.14 v. 10.27 kg/d). Compared with the control diets, both UR and 402 Huhtanen, P. & Heikkilä, T. Treated barley and rapeseed mealfor dairy cows AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 5 (1996): 399^)12. Table 2. Feed intake and calculated ME and AAT consumption in cows receiving grass silage with supplements based untreated barley (UB) or treated barley (TB), both given withoutprotein supplementation (control), with untreated RSM or treated RSM. Control Untreated RS M Treated RS M Significance of effect 1 UB TB UB TB UB TB SEM B R RT BxRBxRT Intake (kg DM/d) Silage 10.61 9.36 11.20 10.84 11.61 10.62 0.139 *** *** NS * NS Concentrate 8.83 8.77 8.79 8.78 8.84 8.80 Total 19.44 18.13 19.99 19.62 20.45 19.42 0.140 *** *** NS * NS ME (MJ/d) 2 221.8 209.3 222.6 220.8 229.4 218.6 1.55 *** *** NS * * ME (MJ/d)' 199.8 186.1 206.1 203.2 213.0 200.4 1.62 *** *** NS o ** Difference (MJ/d) 22.0 23.1 16.5 17.6 16.5 18.2 0.77 o *** NS NS NS AAT(g/d)4 1747 1690 1824 1841 1947 1896 11.8 ** *** *** o * AAT(g/d)' 1736 1636 1848 1831 1908 1821 11.8 *** *** o * * PBV(g/d) 4 -468 -551 -109 -182 -184 -253 1.3 *** *** *** *** NS 1 Significance of orthogonal contrasts: B = effect of barley treatment, R = effect of RSM supplementation, RT = effect of RSM treatment, B x R interaction between barley treatment and RSM supplementation and B x RT = interaction between barley treatment and RSM treatment. o P < 0.10, * P<0.05, �* P