Effects of including chopped alfalfa hay in barley-based total mixed rations on production and rumen fermentation of lactating dairy cows

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1 SHORT COMMUNICATION Effects of including chopped alfalfa hay in barley-based total mixed rations on production and rumen fermentation of lactating dairy cows M. S. Einarson, J. C. Plaizier 1, and K. M. Wittenberg Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. Received 4 February 2005, accepted 3 March Einarson, M. S., Plaizier, J. C. and Wittenberg, K. M Effects of including chopped alfalfa hay in barley-based total mixed rations on production and rumen fermentation of lactating dairy cows. Can. J. Anim. Sci. 85: Alfalfa silage [13.6% dry matter (DM)] was replaced with chopped alfalfa hay in barley silage and barley-grain-based total mixed rations. This replacement increased DM from 45.2 to 54.9%, decreased physical effective fibre, determined as the proportion of the DM passing through the 8- and 19-mm screens of the Penn State Particle Separator multiplied by dietary neutral detergent fibre (pendf), from 21.9 to 16.2% DM, increased dry matter intake from 19.1 to 21.2 kg d 1, numerically reduced milk protein yield from 1.01 to 0.93 kg d 1, but did not affect milk yield, milk fat, rumen ph, and rumen ammonia. Key words: Alfalfa silage, chopped alfalfa hay, milk production, feed intake Einarson, M. S., Plaizier, J. C. et Wittenberg, K. M Conséquences de l inclusion de foin de luzerne haché aux rations mixtes totales à base d orge sur la production et sur la fermentation dans le rumen des vaches laitières en lactation. Can. J. Anim. Sci. 85: Les auteurs ont remplacé l ensilage de luzerne (13,6 % de matière sèche (MS)) par du foin de luzerne haché dans les rations mixtes totales à base d ensilage et de grain d orge. Cette substitution fait passer la concentration de MS de 45,2 % à 54,9 %, réduit la quantité de fibres physiques efficaces (proportion de MS qui traverse les tamis à mailles de 8 et de 19 mm du séparateur de particules Penn State multipliée par la proportion de fibres au détergent neutre) de 21,9 à 16,2 %, augmente l ingestion de MS de 19,1 à 21,2 kg par jour et diminue numériquement le rendement en protéines du lait de 1,01 à 0,93 kg par jour, mais n a aucune incidence sur le rendement laitier, la matière grasse du lait, le ph du rumen et la concentration d ammoniaque dans le rumen. Mots clés: Ensilage de luzerne, foin de luzerne haché, production de lait, prise alimentaire The addition of long alfalfa hay to silage-based diets can increase milk production of dairy cows (Beauchemin and Buchanan-Smith 1989). However, replacing alfalfa silage with chopped and ground alfalfa hay in these diets can reduce (Beauchemin et al. 2003) or not affect (Calberry et al. 2003) feed intake and milk production. This disparity could be due to increased rumen buffering resulting from increased intake of long hay and decreased rumen buffering due to increased intake of chopped and ground hay (Mertens 1997). The effects of adding chopped hay and reducing dietary particle size depend on dietary physical effective fibre (pendf) and forage source (Mertens 1997). Hence, the effect of adding chopped hay to barley-silage-based diets can differ from that of adding chopped hay to the alfalfa-silage- and corn-silage-based diets used by Beauchemin et al. (2003) and Calberry et al. (2003). This study investigated the effects of replacing alfalfa silage with chopped alfalfa hay on dry matter intake (DMI), rumen ph, and milk production of dairy cows fed barley-silage- and barleygrain-based total mixed ration (TMR). Alfalfa silage was 1 To whom correspondence should be addressed. 251 replaced with chopped alfalfa hay in order to include chopped alfalfa hay in the diet without altering the dietary content of alfalfa. Twelve multiparous lactating Holstein cows, housed in a tie-stall barn at the Glenlea Research Station, University of Manitoba, were used in four 3 3 Latin squares with three 3-wk experimental periods. Experimental periods consisted of 14 d of adaptation and 7 d of data collection. Animals were cared for in accordance with the guidelines of the Canadian Council on Animal Care (1993). Upon commencement of the experiment, cows averaged 142 ± 62.3 (mean ± SD) days in milk (DIM), had an average body condition score (BCS) of 3.0 ± 0.40 on a 1 to 5 scale and weighed on average 625 ± 76.7 kg. Cows were assigned one of three TMR during each experimental period. Diets contained 34.6% DM barley silage, 33.6% DM barley- grain- Abbreviations: ADF, acid detergent fibre; CP, crude protein; DM, dry matter; DMI, dry matter intake; NDF, neutral detergent fibre; NFC, non-fibre carbohydrates; pendf, physical effective fibre; PSPS, Penn State Particle Separator; TMR, total mixed ration

2 252 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 1. Feed intake, rumen conditions, milk production and composition of cows fed experimental diets, with fixed inclusion rates of barley silage, energy supplement and protein supplement and containing 13.6% DM chopped alfalfa hay (H), 6.8% DM chopped alfalfa hay and 6.8% DM alfalfa silage (HS), or 13.6 % DM alfalfa silage (S) Diet Item z H HS S SE P value DMI (kg d 1 ) 21.2a 20.4ab 19.1b Orts (% of feed provided) Rumen ph Rumen ammonia (mg dl 1 ) Milk yield (kg d 1 ) Milk components Fat (%) Fat yield (kg d 1 ) Protein (%) Protein yield (kg d 1 ) z Feed intake and milk production variables were averaged for each animal during each period (n = 12) for each treatment and analyzed by analysis of variance. a c Means in row with different letters are different (P < 0.05). based energy supplement, 14.7% DM protein supplement and 3.5% DM sunflower seeds. Diets also contained (1) 13.6% DM chopped alfalfa hay, (2) 6.8% DM chopped alfalfa hay and 36.8% DM alfalfa silage, or (3) 13.6% DM alfalfa silage. Hay was chopped with a 8610 Tub Grinder (JI Case International, Rancine, WI). TMR were fed once daily for ad libitum consumption allowing for between 5 and 10% orts. Cows had unlimited access to fresh water. During data collection periods, the amount of TMR offered and refused was recorded daily for each cow. Feed samples were analyzed by wet chemistry (Calberry et al. 2003). Particle size distributions of forages and diets were determined using the Penn State Particle Separator (PSPS) (Lammers et al. 1996). The pendf was determined as the proportion of DM retained by the 19- and 8-mm PSPS screens multiplied by dietary neutral detergent fibre (NDF) content. Cows were milked twice daily. Milk samples were collected from four subsequent milkings and analyzed by near infrared analysis (Calberry et al. 2003). Rumen fluid was sampled twice during each collection period at 4 to 5 h post-feeding using an oral probe and analyzed for ph and ammonia as described by Calberry et al. (2003). Analysis of variance of weekly averages of rumen fluid, milk, and intakes was conducted using the SAS Mixed Procedure (SAS Institute, Inc. 1999). The effect of diet was considered fixed. The effects of cow and period were considered random. To test residual effects, the diets during the previous experimental period were included as fixed effects. However, as these effects were not significant (P > 0.25), they were removed from the statistical model. Alfalfa silage and chopped alfalfa hay differed in DM (53.9 vs. 87.3%) and pendf (34.1% DM vs. 18.1% DM), but did not differ in crude protein (CP), NDF, acid detergent fibre (ADF), crude fat, ash, and non-fibre carbohydrates (NFC). Replacing alfalfa silage with chopped alfalfa hay increased (P < 0.01) dietary DM from 45.2 to 54.9%, reduced (P = 0.04) soluble protein from 35.9 to 28.2% CP, reduced pendf from 21.9 to 16.2% DM (P < 0.03), and did not affect CP, NDF and ADF. Hence, diets differed in DM and pendf. Averaged across diets, CP, NDF, ADF, crude fat, ash, and NFC contents were 15.8, 41.2, 28.2, 5.9, 10.9, and 26.2% DM, respectively. The proportions of the barley silage retained by the bottom pan of the PSPS were 28.2, 25.7, and 58.0% DM, respectively. A survey of Manitoba dairy farms showed that, on average, 42.5% DM of barley silage samples were retained by the PSPS bottom pan (Plaizier et al. 2004). Hence, the barley silage used in the current study was coarser than what is commonly seen across Manitoba. Replacing alfalfa silage with chopped alfalfa hay increased (P < 0.05) DMI from 19.1 to 21.2 kg d 1, did not affect milk yield and milk fat, tended (P = 0.08) to reduce milk protein, and did not affect rumen ph and rumen ammonia (Table 1). Similar to the studies by Beauchemin et al. (2003), Calberry et al. (2003) and Soita et al. (2003), adaptation periods of 2 wk were used. This was considered long enough to adapt rumen conditions and feed intake to diets. Reducing dietary particle size of high pendf diets can increase DMI due to increased rumen passage rate and reduced physical fill of feed particles (Allen 2000). This could explain why in the current study increasing the proportion of small feed particles in the diet by replacing alfalfa silage with chopped alfalfa hay increased DMI, and why in studies with diets containing less pendf (Beauchemin et al. 2003; Calberry et al. 2003) this replacement did not increase DMI. This effect could also have been due to the negative effects of fermentation products and moisture content on DMI, or underestimation of DMI from silagebased-diets due to volatilization of organic compounds (Petit et al. 1997; Allen 2000). However, the underestimation of silage DM by oven drying observed by Petit et al. (1997) was not large enough to explain the observed increase in DMI due to replacing 13.6% DM of alfalfa silage with chopped alfalfa hay. Differences in PSPS distribution between TMR and their respective orts (Fig. 1) indicate that cows selected against large feed particles in favour of smaller particles. Similar feed selection was observed by Calberry et al. (2003) and Leonardi and Armentano (2003). Rumen fluid was sampled 4 to 5 h after feeding due to the diurnal variation in rumen ph, and the expected low rumen ph at that time (Beauchemin et al. 2003). The ph of these rumen samples indicate that none of the diets induced suba-

3 EINARSON ET AL. REPLACING CHOPPED HAY WITH SILAGE IN TOTAL MIXED RATIONS 253 Fig. 1. Penn State Particle Size distribution of diets and orts (DM basis). Diets contained 13.6% DM chopped alfalfa hay (H), 6.8% DM chopped alfalfa hay and 6.8% DM alfalfa silage (HS), or 13.6% DM alfalfa silage (S). cute ruminal acidosis (Beauchemin et al. 2003). The absence of differences in rumen ph among diets, despite dietary differences in pendf could be due to the high pendf of the diets. Mertens (1997) concluded that reduction in dietary particle size causes a larger reduction in rumen ph in low pendf diets compared with high pendf diets. This might explain why Beauchemin et al. (2003) and Calberry et al (2003) found that replacing alfalfa silage with chopped or ground alfalfa hay reduced mean rumen ph in diets that contained less pendf compared with those used in the current experiment. Despite increasing DMI, replacing alfalfa silage with chopped alfalfa hay did not affect milk yield and milk fat. When a reduction in feed particle size results in low rumen ph, then de novo milk fat synthesis can be reduced due to increases in trans-fatty acids (Griinari et al. 1998). The absence of a diet effect on milk fat can, therefore, be explained by the lack of a diet effect on rumen ph and the high rumen ph resulting from all diets. In contrast to the current study, Beauchemin et al. (2003) and Calberry et al. (2003) did not find that replacing alfalfa silage with chopped alfalfa hay reduced milk protein. The diet effect on milk protein in the current study might be explained by a reduction in rumen digestible organic matter due to the inclusion of chopped hay, as this component of feeds drives microbial protein production (National Research Council 2001). Diets did not differ in ADF, which is inversely related to rumen digestibility (National Research Council 2001). However, as the addition of chopped hay reduced dietary particle size, it could also have increased rumen passage rate (Soita et al. 2003). The latter could have contributed to reduced rumen digestion of organic matter and microbial protein production. The study did not demonstrate benefits of including chopped hay in barley-based TMR containing 41.2% DM NDF and 21.9% DM pendf. This study was supported by a grant from Dairy Farmers of Canada (DFC). Allen, M. S Effects of diet on short-term regulation of feed intake by lactating dairy cattle. J. Dairy Sci. 83: Beauchemin, K. A and Buchanan-Smith, J. G Effects of dietary neutral detergent fiber concentration and supplementary long hay on chewing activities and milk production of dairy cows. J. Dairy Sci. 72: Beauchemin, K. A., Yang, W. Z., Rode, L. M Effects of particle size of alfalfa based dairy cow diets on chewing activity, ruminal fermentation, and milk production. J. Dairy Sci. 86: Calberry J. M., Plaizier, J. C., Einarson, M. S. and McBride, B. W Effects of replacing chopped alfalfa hay with alfalfa silage in a total mixed ration on production and rumen conditions of lactating dairy cows. J. Dairy Sci. 86: Canadian Council on Animal Care Guide to the care and use of experimental animals. E. D. Olfert, B. M. Cross, and A. A. McWilliams, eds. Vol. 1, 2nd ed. CCAC, Ottawa, ON. Griinari, J. M., Dwyer, D. A., McGuire, M. A., Bauman, D. E., Palmquist, D. L. and Nurmela, K. V Trans-octadecenoic acids and milk fat depression in lactating dairy cows. J. Dairy Sci. 81: Lammers, B. P., Buckmaster, D. R. and Heinrichs, A. J A simple method for the analysis of particle sizes of forages and total mixed rations. J. Dairy Sci. 79: Leonardi, C. and Armentano, L. E Effect of quantity, quality, and length of alfalfa hay on selective consumption by dairy cows. J. Dairy Sci. 86: Mertens, D. R Creating a system for meeting the fiber requirements of dairy cows. J. Dairy Sci. 80: National Research Council Nutrient requirements of dairy cattle. 7th rev. ed. National Academy of Science, Washington, DC. Petit, H. V., Lafreniere, C. and Veira, D. M A comparison of methods to determine dry matter in silages. J. Dairy Sci. 80: Plaizier, J. C., Garner, T., Droppo, T. and Whiting, T Nutritional practices and water quality on Manitoba dairy farms. Can. J. Anim. Sci. 84: SAS Institute, Inc SAS/STAT user s guide. Version 8 SAS Institute, Inc., Cary, NC. Soita, H. W., Christensen, D. A. and McKinnon, J. J Effects of barley silage particle size and concentrate level on rumen kinetic parameters and fermentation patterns in steers. Can. J. Anim. Sci. 83:

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