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Milk Yield and Composition of Dairy Cows Fed Concentrate Based on Naked Oats1
Milk Yield and Composition of Dairy Cows Fed Concentrate Based on Naked Oats1 HE´LE`NE V. PETIT* and STEPHANE ALARY† *Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, Lennoxville QC, Canada J1M 1Z3 †Ferme Ste ´ pido enr., 160 ch. Alary, Lucksville QC, Canada J0X 2G0
ABSTRACT A 1.5-yr study was designed to determine the effects of feeding isonitrogenous and isoenergetic concentrates based on naked oats, corn, or a mixture (50: 50 on as-fed basis) of naked oats and corn on milk yield and composition. In vitro dry matter ( D M ) digestibility and ruminal degradabilities of DM, N, and starch of naked oats were compared with those of covered oats. Twenty-seven multiparous Holstein cows were blocked by similar calving date and assigned to 9 replicates. All cows were fed a mixture of grass silage, protein supplement, concentrate, and a vitamin and mineral mix for ad libitum intake. Treatment diets were fed from 3 to 36 wk of lactation. Milk yield and composition, yield of 4% fat-corrected milk, and yield of protein and fat were similar among treatments. Ruminal effective degradabilities of DM were higher for naked oats than for covered oats, but the ruminal degradabilities of crude protein and starch were similar. The rapidly degradable fractions of DM, crude protein, and starch were greater for naked than covered oats; the potentially degradable fractions were less. In vitro DM digestibility of naked oats was higher than was that of covered oats. Naked oats may be a good alternative to corn for milk yield. ( Key words: dairy cows, naked oats, milk yield) Abbreviation key: EDCP = effective degradability of CP, EDDM = effective degradability of DM, EDST = effective degradability of starch, IVDMD = in vitro DM digestibility.
( 2 ) . Naked oats have a relatively high percentage (18%) of protein, which could contribute to decreased soybean meal supplementation and feeding costs. Brand and van der Merwe ( 2 ) reported that naked oats could replace all corn in the diets of weanling and grower-finisher pigs without any adverse effect on daily gain or feed conversion, and Morris and Burrows ( 1 1 ) reported that the inclusion of naked oats improved feed efficiency by pigs. The incorporation of naked oats up to 50% of the DM in the diets of broiler chicken has no negative effects on production (3). Most research on naked oats has been conducted with nonruminant species, and it is difficult to extrapolate results to ruminants. The feeding values of naked oats and barley have been compared for lactating dairy cattle (4, 8); however, a comparison for naked oats and corn has not been published. Although the net energy for lactation of hull-less barley was found to be higher than was that of barley, milk yield by cows might be limited unless hull-less barley is adequately processed to ensure high digestibility (18). As a result, it is impossible to evaluate the nutritive value of hull-less cereals based solely on their chemical composition. Consequently, the objectives of this experiment were 1 ) to compare the effects of a concentrate based on corn (control), naked oats, or a mixture (50:50 on as-fed basis) of corn and naked oats on feeding costs, milk yield, and composition; and 2 ) to compare the in vitro DM digestibility ( IVDMD) and ruminal degradabilities of DM, N, and starch of naked and covered oats.
INTRODUCTION
MATERIALS AND METHODS
In those areas of Canada where cooler temperatures prevail in the summer, naked oats ( Avena nuda) are a potentially useful alternative to corn because the energy content of both is quite similar
Received September 21, 1998. Accepted January 11, 1999. 1Contribution No. 598 from the Dairy and Swine Research and Development Centre. 1999 J Dairy Sci 82:1004–1007
During a 1.5-yr period, 27 multiparous Holstein cows were blocked for similar calving date and assigned to 9 replicates. At 2 wk postpartum, cows within groups were assigned randomly to one of three isonitrogenous and isoenergetic treatment diets. Cows were introduced gradually to the treatment diets over a 5-d period starting at wk 3 postpartum. Treatment diets consisted of the control (corn), naked oats, or a mixture (50:50, as-fed basis) of corn and naked oats
1004
SHORT COMMUNICATION: NAKED OATS FOR DAIRY COWS TABLE 1. Ingredient amounts offered (DM basis). Ingredients
Corn
Grass silage1 Naked oats2 Corn3 Protein supplement4 Total DM offered5
11.5 0 10.1 1.2 22.8
Naked oats
Corn and naked oats
(kg/d per cow) 11.5 11.5 9.6 5.5 0 6.0 0 0.6 21.1 23.6
1Contained 17.5% CP, 34.8% ADF, 46.2% NDF, 0.91% Ca, and 0.20% P. 2Contained 17.1% CP, 6.2% ADF, 7.1% NDF, 0.09% Ca, and 0.63% P. 3Contained 9.7% CP, 4.6% ADF, 7.3% NDF, 0.02% Ca, and 0.30% P. 4MH55, Co-op, Montreal, QC; contained 45.0% CP, 15.0% ADF, 18% NDF, 3.2% Ca, 1.5% P, 0.7% Mg, 1.4% Na, 2.1% Cl, 1% K, 1% S, 386 mg/kg of Fe, 443 mg/kg of Mn, 539 mg/kg of Zn, 68 mg/kg of Cu, 25 mg/kg of I, 4.6 mg/kg of Co, 2 mg/kg of Se, 62,500 IU/kg of vitamin A, 12,500 IU/kg of vitamin D, and 159 IU/kg of vitamin E. 5In addition, cows fed corn, naked oats, and corn and naked oats received 50, 200, and 200 g, respectively, of a salt mixture containing 5% CP, 5.5% Mg, 55% salt, 200,000 IU/kg of vitamin A, 60,000 IU/kg of vitamin D, 1200 IU/kg of vitamin E, and 30, 50, and 50 g, respectively, of an Se vitamin E premix containing 5% CP, 7500 IU/ kg of vitamin E, and 120 mg/kg of Se. All cows also were fed 100 g of a vitamin and mineral mix containing 37% Ca, 5.5% Mg, 0.4% S, 3200 mg/kg of Zn, 125 mg/kg of I, 300,000 IU/kg of vitamin A, 100,000 IU/kg of vitamin D, and 500 IU/kg of vitamin E.
(Table 1). Vitamins and minerals were fed to meet the NRC ( 1 2 ) requirements (Table 1). Forages were fed at 0500, 0700, 0900, 1200, 1500, 1700, 2100, and 2300 h, and grains were fed at 0630, 1030, 1430, 1730, and 2030 h. The cultivars of naked oats used during the first year were Hill and Lotta; Hill only was used during the second year. Cereals were rolled before feeding. The continuous lactation trial was carried out from wk 3 to 36 of lactation. Cows were housed in tie stalls, fed individually, and milked twice daily at 0600 and 1700 h. Milk yield and composition for all cows were determined twice monthly and adjusted for the number of days of lactation. Ruminal DM, CP, and starch degradabilities of naked oats and covered oats (cv. Shaw) were estimated by the nylon bag technique (14). Ruminal fluid was obtained from cows used for the nylon bag procedure for IVDMD determination ( 1 7 ) of naked and covered oats samples that were ground through a 1-mm screen in a Wiley mill (model 3; Arthur M. Thomas, Philadelphia, PA). Naked and covered oats were rolled before being placed in the nylon bags. Degradation of DM, CP, and starch was calculated by previously described methods (13, 14). The nonlinear parameters a, b, and c were estimated by an iterative least squares procedure (16), and best
1005
fit values were chosen with the Secant method, using the convergence criterion (10 –8) of SAS (16). The effective degradabilities of DM ( EDDM) , CP ( EDCP) , or starch ( EDST) were calculated ( 1 4 ) assuming a ruminal solid outflow rate of 8%/h ( 1 ) . Milk composition analysis, conducted by the Programme d’Ame´lioration des Troupeaux Laitiers du Que´bec (Ste. Anne-de-Bellevue, QC, Canada) was determined by infrared methods for fat and protein. Feeds were analyzed by standard methodology (14). Milk yield measured on d 15 was used as a covariable in the analysis of subsequent milk yield (14). Milk yield and composition data were analyzed in a randomized block design with covariable, treatment, and block as main sources of variation. Data on ruminal degradability were analyzed as a completely randomized design with cow as the replicate. Significance was declared at P < 0.05 unless otherwise noted. The GLM procedure of SAS ( 1 6 ) was used. RESULTS AND DISCUSSION The costs of concentrate per cow per day were calculated using the prevailing prices at the time this experiment was conducted: US $212, US $328, US $1313, US $556, US $754, and US $354/tonne of DM, respectively, for corn, naked oats, the Se + vitamin E premix, the Ca premix, the salted cube, and the protein supplement. The daily feeding costs of concentrates based on corn, naked oats, and the mixture of corn and naked oats were US $2.69, $3.42, and $3.56. Feeding a mixture of corn and naked oats was more expensive than feeding naked oats only because of the use of naked oats and protein supplement. Milk yield, 4% FCM yield, milk fat percentage, and milk protein percentage averaged, respectively, 34.2 kg/d, 33.7 kg/d, 3.94%, and 3.71%, and they were similar ( P > 0.10) among treatments. Similar milk yields and milk composition were obtained for cows fed either hull-less cereals or the covered varieties (18), suggesting that hull-less grains could require more processing to improve their utilization for milk yield. This hypothesis is corroborated by the fact that flaking increases the digestibility and energy value of hull-less barley for growing steers (19). Moreover, starch from corn is more slowly fermented in the rumen than is that from oats ( 6 ) , and rations were fed five times daily in the present experiment; consequently, this diet could have maintained a more gradual starch fermentation over time for naked oats. Utilization of naked oats to increase milk yield could also be limited by their high fat content. Naked oats have approximately half the cell wall content but are three times richer in lipid than are common oats Journal of Dairy Science Vol. 82, No. 5, 1999
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PETIT AND ALARY
TABLE 2. Ruminal degradability of naked oats and covered oats.1 Item2 DM a b c EDDM CP a b c EDCP Starch a b c EDST
Naked oats Oats
P
SE
40.4 49.3 24.3 77.2
17.3 51.9 30.2 58.4
0.003 0.06 0.008 0.008
0.7 0.4 2.7 0.9
34.5 56.1 27.2 77.7
19.5 69.4 39.5 77.7
0.02 0.001 0.11 0.8
1.1 0.2 2.2 1.3
58.2 37.3 21.0 84.7
38.7 57.2 49.7 87.9
0.02 0.004 0.07 0.2
1.7 0.7 4.1 0.9
1Least squares means with pooled standard errors ( n = 2 cows per treatment). 2a = The percentage of DM, CP, or starch solubilized at initiation of incubation; b = the percentage of DM, CP, or starch potentially degradable in the rumen; and c = the rate constant (percentage per hour) of disappearance of fraction b; EDDM = effective degradability of DM; EDCP = effective degradability of CP; EDST = effective degradability of starch, calculated at a solid outflow rate of 8%/h.
( 5 ) . This high fat content could explain why DMI decreases with an increased proportion of naked oats in the diets of dairy cows ( 9 ) and pigs ( 2 ) . However, when high proportions of naked oats are substituted, respectively, for barley and corn in the diets of dairy cows and pigs, yields of milk and milk constituents (8, 9 ) and the ADG ( 9 ) are maintained ( 2 ) . According to Martin ( 7 ) , decreased DMI when cows are fed naked oats compared to being fed covered cereals could partly be a result of decreased ruminal fiber digestion and changes in end products of ruminal fermentation caused by higher fat intake. This finding suggests that hull-less cereals with high fat content could benefit from processing treatments decreasing ruminal degradability (e.g., formaldehyde) without affecting the overall digestibility. The readily soluble fraction of DM was higher for naked oats than for covered oats (Table 2). The potentially degradable fraction of DM tended to be smaller ( P = 0.06) for naked oats than for covered oats, but the disappearance rate of DM was lower for the former. The EDDM was higher for naked oats than for covered oats. The readily soluble fraction of CP was higher for naked oats than for covered oats and the inverse was observed for the potentially degradable fraction of CP (Table 2). The disappearance rate of CP tended ( P = 0.11) to be lower for naked than covered oats. The EDCP was similar for naked and covered oats. Differences in the ruminal Journal of Dairy Science Vol. 82, No. 5, 1999
degradability of starch between naked and covered oats were similar to those observed for the ruminal degradability of CP. The value of in vitro DM digestibility of naked oats (93.4%) was higher than was that of covered oats (74.1%), which could be explained by the absence of the hull fraction that contains a large proportion of low digestible fiber. Moreover, the high fat content of naked oats compared to covered oats ( 5 ) would contribute to increase in in vitro digestibility, the readily soluble fraction of DM, and the EDDM as oil would be quickly released. However, a faster release of oil could have a negative impact on the cow because it could decrease ruminal fiber digestion, which may partly explain why milk yield was similar among treatments. Feed costs were lower with corn than with naked oats. A yield of 4% FCM was similar for oats, corn, and a mixture (50:50) of naked oats and corn, although in vitro DM digestibility of naked oats was higher than that of corn. Because of its high oil content, naked oats could have a detrimental effect on ruminal fiber digestion and could benefit from further processing to decrease its degradability in the rumen without changing its overall digestibility. ACKNOWLEDGMENTS The authors thank I. Blanchet for her technical support. This work was financially supported by the Programme d’essais et expe´rimentation en agroalimentaire, Entente auxiliaire Canada-Que´bec sur le de´veloppement e´conomique des re´gions du Que´bec (Que´bec, Canada). REFERENCES 1 Agricultural Research Council. 1984. The Nutrient Requirements of Ruminant Livestock. Suppl. 1. Commonw. Agric. Bur., Wallingford, England. 2 Brand, T. S., and J. P. van der Merwe. 1996. Naked oats ( Avena nuda) as a substitute for maize in diets for weanling and grower-finisher pigs. Anim. Feed Sci. Technol. 57:139–147. 3 Cave, N. A., and V. D. Burrows. 1993. Evaluation of naked oat ( Avena nuda) in the broiler chicken diet. Can. J. Anim. Sci. 73: 393–399. 4 Fearon, A. M., C. S. Mayne, and S. Marsden. 1996. The effect of inclusion of naked oats in the concentrate offered to dairy cows on milk yield, milk fat composition and properties. J. Sci. Food Agric. 72:273–282. 5 Givens, D. I. and J. M. Brunnen. 1987. Nutritive value of naked oats for ruminants. Anim. Feed Sci. Technol. 18:83–87. 6 Herrera-Saldana, R. E., J. T. Huber, and M. H. Poore. 1990. Dry matter, crude protein, and starch degradability of five cereal grains. J. Dairy Sci. 73:2386–2393. 7 Martin, P. A. 1990. Digestion in sheep of diets containing naked oats or barley. J. Sci. Food Agric. 52:477–484. 8 Martin, P. A., and D. J. Roberts. 1989. A comparison of naked oats and barley in a silage-based diet for dairy cows. Anim. Prod. 48:636.
SHORT COMMUNICATION: NAKED OATS FOR DAIRY COWS 9 Martin, P. A., and P. C. Thomas. 1988. The manipulation of milk fat composition by including naked oats in a silage-based diet for dairy cows. Proc. Nutr. Soc. 47:96A. 10 Martin, P. A., and P. C. Thomas. 1988. Dietary manipulation of the yield and composition of milk: effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition. J. Sci. Food Agric. 43:145–154. 11 Morris, J. R., and V. D. Burrows. 1986. Naked oats in growerfinisher pig diets. Can. J. Anim. Sci. 66:833–836. 12 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Nat. Acad. Sci., Washington, DC. 13 Ørskov, E. R., and I. McDonald. 1979. The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. J. Agric. Sci. (Camb.) 92: 499–503. 14 Petit, H. V., and G.T.D. Santos. 1996. Milk yield and composi-
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tion of dairy cows fed concentrate based on high moisture wheat or high moisture corn. J. Dairy Sci. 79:2292–2296. 15 Petit, H. V., and G. F. Tremblay. 1995. Ruminal fermentation and digestion in lactating cows fed grass silage with protein and energy supplements. J. Dairy Sci. 78:342–352. 16 SAS® User’s Guide: Statistics, Version 5 Edition. 1985. SAS Inst. Inc., Cary, NC. 17 Tilley, J.M.A., and R. A. Terry. 1963. A two-stage technique for the in vitro digestion of forage crops. J. Br. Grassl. Soc. 18: 104–111. 18 Yang, W. Z., K. A. Beauchemin, B. I. Farr, and L. M. Rode. 1997. Comparison of barley, hull-less barley, and corn in the concentrate of dairy cows. J. Dairy Sci. 80:2885–2895. 19 Zinn, R. A., M. Montan˜o, and Y. Shen. 1996. Comparative feeding value of hulless vs covered barley for feedlot cattle. J. Anim. Sci. 74:1198–1193.
Journal of Dairy Science Vol. 82, No. 5, 1999
ABSTRACT A 1.5-yr study was designed to determine the effects of feeding isonitrogenous and isoenergetic concentrates based on naked oats, corn, or a mixture (50: 50 on as-fed basis) of naked oats and corn on milk yield and composition. In vitro dry matter ( D M ) digestibility and ruminal degradabilities of DM, N, and starch of naked oats were compared with those of covered oats. Twenty-seven multiparous Holstein cows were blocked by similar calving date and assigned to 9 replicates. All cows were fed a mixture of grass silage, protein supplement, concentrate, and a vitamin and mineral mix for ad libitum intake. Treatment diets were fed from 3 to 36 wk of lactation. Milk yield and composition, yield of 4% fat-corrected milk, and yield of protein and fat were similar among treatments. Ruminal effective degradabilities of DM were higher for naked oats than for covered oats, but the ruminal degradabilities of crude protein and starch were similar. The rapidly degradable fractions of DM, crude protein, and starch were greater for naked than covered oats; the potentially degradable fractions were less. In vitro DM digestibility of naked oats was higher than was that of covered oats. Naked oats may be a good alternative to corn for milk yield. ( Key words: dairy cows, naked oats, milk yield) Abbreviation key: EDCP = effective degradability of CP, EDDM = effective degradability of DM, EDST = effective degradability of starch, IVDMD = in vitro DM digestibility.
( 2 ) . Naked oats have a relatively high percentage (18%) of protein, which could contribute to decreased soybean meal supplementation and feeding costs. Brand and van der Merwe ( 2 ) reported that naked oats could replace all corn in the diets of weanling and grower-finisher pigs without any adverse effect on daily gain or feed conversion, and Morris and Burrows ( 1 1 ) reported that the inclusion of naked oats improved feed efficiency by pigs. The incorporation of naked oats up to 50% of the DM in the diets of broiler chicken has no negative effects on production (3). Most research on naked oats has been conducted with nonruminant species, and it is difficult to extrapolate results to ruminants. The feeding values of naked oats and barley have been compared for lactating dairy cattle (4, 8); however, a comparison for naked oats and corn has not been published. Although the net energy for lactation of hull-less barley was found to be higher than was that of barley, milk yield by cows might be limited unless hull-less barley is adequately processed to ensure high digestibility (18). As a result, it is impossible to evaluate the nutritive value of hull-less cereals based solely on their chemical composition. Consequently, the objectives of this experiment were 1 ) to compare the effects of a concentrate based on corn (control), naked oats, or a mixture (50:50 on as-fed basis) of corn and naked oats on feeding costs, milk yield, and composition; and 2 ) to compare the in vitro DM digestibility ( IVDMD) and ruminal degradabilities of DM, N, and starch of naked and covered oats.
INTRODUCTION
MATERIALS AND METHODS
In those areas of Canada where cooler temperatures prevail in the summer, naked oats ( Avena nuda) are a potentially useful alternative to corn because the energy content of both is quite similar
Received September 21, 1998. Accepted January 11, 1999. 1Contribution No. 598 from the Dairy and Swine Research and Development Centre. 1999 J Dairy Sci 82:1004–1007
During a 1.5-yr period, 27 multiparous Holstein cows were blocked for similar calving date and assigned to 9 replicates. At 2 wk postpartum, cows within groups were assigned randomly to one of three isonitrogenous and isoenergetic treatment diets. Cows were introduced gradually to the treatment diets over a 5-d period starting at wk 3 postpartum. Treatment diets consisted of the control (corn), naked oats, or a mixture (50:50, as-fed basis) of corn and naked oats
1004
SHORT COMMUNICATION: NAKED OATS FOR DAIRY COWS TABLE 1. Ingredient amounts offered (DM basis). Ingredients
Corn
Grass silage1 Naked oats2 Corn3 Protein supplement4 Total DM offered5
11.5 0 10.1 1.2 22.8
Naked oats
Corn and naked oats
(kg/d per cow) 11.5 11.5 9.6 5.5 0 6.0 0 0.6 21.1 23.6
1Contained 17.5% CP, 34.8% ADF, 46.2% NDF, 0.91% Ca, and 0.20% P. 2Contained 17.1% CP, 6.2% ADF, 7.1% NDF, 0.09% Ca, and 0.63% P. 3Contained 9.7% CP, 4.6% ADF, 7.3% NDF, 0.02% Ca, and 0.30% P. 4MH55, Co-op, Montreal, QC; contained 45.0% CP, 15.0% ADF, 18% NDF, 3.2% Ca, 1.5% P, 0.7% Mg, 1.4% Na, 2.1% Cl, 1% K, 1% S, 386 mg/kg of Fe, 443 mg/kg of Mn, 539 mg/kg of Zn, 68 mg/kg of Cu, 25 mg/kg of I, 4.6 mg/kg of Co, 2 mg/kg of Se, 62,500 IU/kg of vitamin A, 12,500 IU/kg of vitamin D, and 159 IU/kg of vitamin E. 5In addition, cows fed corn, naked oats, and corn and naked oats received 50, 200, and 200 g, respectively, of a salt mixture containing 5% CP, 5.5% Mg, 55% salt, 200,000 IU/kg of vitamin A, 60,000 IU/kg of vitamin D, 1200 IU/kg of vitamin E, and 30, 50, and 50 g, respectively, of an Se vitamin E premix containing 5% CP, 7500 IU/ kg of vitamin E, and 120 mg/kg of Se. All cows also were fed 100 g of a vitamin and mineral mix containing 37% Ca, 5.5% Mg, 0.4% S, 3200 mg/kg of Zn, 125 mg/kg of I, 300,000 IU/kg of vitamin A, 100,000 IU/kg of vitamin D, and 500 IU/kg of vitamin E.
(Table 1). Vitamins and minerals were fed to meet the NRC ( 1 2 ) requirements (Table 1). Forages were fed at 0500, 0700, 0900, 1200, 1500, 1700, 2100, and 2300 h, and grains were fed at 0630, 1030, 1430, 1730, and 2030 h. The cultivars of naked oats used during the first year were Hill and Lotta; Hill only was used during the second year. Cereals were rolled before feeding. The continuous lactation trial was carried out from wk 3 to 36 of lactation. Cows were housed in tie stalls, fed individually, and milked twice daily at 0600 and 1700 h. Milk yield and composition for all cows were determined twice monthly and adjusted for the number of days of lactation. Ruminal DM, CP, and starch degradabilities of naked oats and covered oats (cv. Shaw) were estimated by the nylon bag technique (14). Ruminal fluid was obtained from cows used for the nylon bag procedure for IVDMD determination ( 1 7 ) of naked and covered oats samples that were ground through a 1-mm screen in a Wiley mill (model 3; Arthur M. Thomas, Philadelphia, PA). Naked and covered oats were rolled before being placed in the nylon bags. Degradation of DM, CP, and starch was calculated by previously described methods (13, 14). The nonlinear parameters a, b, and c were estimated by an iterative least squares procedure (16), and best
1005
fit values were chosen with the Secant method, using the convergence criterion (10 –8) of SAS (16). The effective degradabilities of DM ( EDDM) , CP ( EDCP) , or starch ( EDST) were calculated ( 1 4 ) assuming a ruminal solid outflow rate of 8%/h ( 1 ) . Milk composition analysis, conducted by the Programme d’Ame´lioration des Troupeaux Laitiers du Que´bec (Ste. Anne-de-Bellevue, QC, Canada) was determined by infrared methods for fat and protein. Feeds were analyzed by standard methodology (14). Milk yield measured on d 15 was used as a covariable in the analysis of subsequent milk yield (14). Milk yield and composition data were analyzed in a randomized block design with covariable, treatment, and block as main sources of variation. Data on ruminal degradability were analyzed as a completely randomized design with cow as the replicate. Significance was declared at P < 0.05 unless otherwise noted. The GLM procedure of SAS ( 1 6 ) was used. RESULTS AND DISCUSSION The costs of concentrate per cow per day were calculated using the prevailing prices at the time this experiment was conducted: US $212, US $328, US $1313, US $556, US $754, and US $354/tonne of DM, respectively, for corn, naked oats, the Se + vitamin E premix, the Ca premix, the salted cube, and the protein supplement. The daily feeding costs of concentrates based on corn, naked oats, and the mixture of corn and naked oats were US $2.69, $3.42, and $3.56. Feeding a mixture of corn and naked oats was more expensive than feeding naked oats only because of the use of naked oats and protein supplement. Milk yield, 4% FCM yield, milk fat percentage, and milk protein percentage averaged, respectively, 34.2 kg/d, 33.7 kg/d, 3.94%, and 3.71%, and they were similar ( P > 0.10) among treatments. Similar milk yields and milk composition were obtained for cows fed either hull-less cereals or the covered varieties (18), suggesting that hull-less grains could require more processing to improve their utilization for milk yield. This hypothesis is corroborated by the fact that flaking increases the digestibility and energy value of hull-less barley for growing steers (19). Moreover, starch from corn is more slowly fermented in the rumen than is that from oats ( 6 ) , and rations were fed five times daily in the present experiment; consequently, this diet could have maintained a more gradual starch fermentation over time for naked oats. Utilization of naked oats to increase milk yield could also be limited by their high fat content. Naked oats have approximately half the cell wall content but are three times richer in lipid than are common oats Journal of Dairy Science Vol. 82, No. 5, 1999
1006
PETIT AND ALARY
TABLE 2. Ruminal degradability of naked oats and covered oats.1 Item2 DM a b c EDDM CP a b c EDCP Starch a b c EDST
Naked oats Oats
P
SE
40.4 49.3 24.3 77.2
17.3 51.9 30.2 58.4
0.003 0.06 0.008 0.008
0.7 0.4 2.7 0.9
34.5 56.1 27.2 77.7
19.5 69.4 39.5 77.7
0.02 0.001 0.11 0.8
1.1 0.2 2.2 1.3
58.2 37.3 21.0 84.7
38.7 57.2 49.7 87.9
0.02 0.004 0.07 0.2
1.7 0.7 4.1 0.9
1Least squares means with pooled standard errors ( n = 2 cows per treatment). 2a = The percentage of DM, CP, or starch solubilized at initiation of incubation; b = the percentage of DM, CP, or starch potentially degradable in the rumen; and c = the rate constant (percentage per hour) of disappearance of fraction b; EDDM = effective degradability of DM; EDCP = effective degradability of CP; EDST = effective degradability of starch, calculated at a solid outflow rate of 8%/h.
( 5 ) . This high fat content could explain why DMI decreases with an increased proportion of naked oats in the diets of dairy cows ( 9 ) and pigs ( 2 ) . However, when high proportions of naked oats are substituted, respectively, for barley and corn in the diets of dairy cows and pigs, yields of milk and milk constituents (8, 9 ) and the ADG ( 9 ) are maintained ( 2 ) . According to Martin ( 7 ) , decreased DMI when cows are fed naked oats compared to being fed covered cereals could partly be a result of decreased ruminal fiber digestion and changes in end products of ruminal fermentation caused by higher fat intake. This finding suggests that hull-less cereals with high fat content could benefit from processing treatments decreasing ruminal degradability (e.g., formaldehyde) without affecting the overall digestibility. The readily soluble fraction of DM was higher for naked oats than for covered oats (Table 2). The potentially degradable fraction of DM tended to be smaller ( P = 0.06) for naked oats than for covered oats, but the disappearance rate of DM was lower for the former. The EDDM was higher for naked oats than for covered oats. The readily soluble fraction of CP was higher for naked oats than for covered oats and the inverse was observed for the potentially degradable fraction of CP (Table 2). The disappearance rate of CP tended ( P = 0.11) to be lower for naked than covered oats. The EDCP was similar for naked and covered oats. Differences in the ruminal Journal of Dairy Science Vol. 82, No. 5, 1999
degradability of starch between naked and covered oats were similar to those observed for the ruminal degradability of CP. The value of in vitro DM digestibility of naked oats (93.4%) was higher than was that of covered oats (74.1%), which could be explained by the absence of the hull fraction that contains a large proportion of low digestible fiber. Moreover, the high fat content of naked oats compared to covered oats ( 5 ) would contribute to increase in in vitro digestibility, the readily soluble fraction of DM, and the EDDM as oil would be quickly released. However, a faster release of oil could have a negative impact on the cow because it could decrease ruminal fiber digestion, which may partly explain why milk yield was similar among treatments. Feed costs were lower with corn than with naked oats. A yield of 4% FCM was similar for oats, corn, and a mixture (50:50) of naked oats and corn, although in vitro DM digestibility of naked oats was higher than that of corn. Because of its high oil content, naked oats could have a detrimental effect on ruminal fiber digestion and could benefit from further processing to decrease its degradability in the rumen without changing its overall digestibility. ACKNOWLEDGMENTS The authors thank I. Blanchet for her technical support. This work was financially supported by the Programme d’essais et expe´rimentation en agroalimentaire, Entente auxiliaire Canada-Que´bec sur le de´veloppement e´conomique des re´gions du Que´bec (Que´bec, Canada). REFERENCES 1 Agricultural Research Council. 1984. The Nutrient Requirements of Ruminant Livestock. Suppl. 1. Commonw. Agric. Bur., Wallingford, England. 2 Brand, T. S., and J. P. van der Merwe. 1996. Naked oats ( Avena nuda) as a substitute for maize in diets for weanling and grower-finisher pigs. Anim. Feed Sci. Technol. 57:139–147. 3 Cave, N. A., and V. D. Burrows. 1993. Evaluation of naked oat ( Avena nuda) in the broiler chicken diet. Can. J. Anim. Sci. 73: 393–399. 4 Fearon, A. M., C. S. Mayne, and S. Marsden. 1996. The effect of inclusion of naked oats in the concentrate offered to dairy cows on milk yield, milk fat composition and properties. J. Sci. Food Agric. 72:273–282. 5 Givens, D. I. and J. M. Brunnen. 1987. Nutritive value of naked oats for ruminants. Anim. Feed Sci. Technol. 18:83–87. 6 Herrera-Saldana, R. E., J. T. Huber, and M. H. Poore. 1990. Dry matter, crude protein, and starch degradability of five cereal grains. J. Dairy Sci. 73:2386–2393. 7 Martin, P. A. 1990. Digestion in sheep of diets containing naked oats or barley. J. Sci. Food Agric. 52:477–484. 8 Martin, P. A., and D. J. Roberts. 1989. A comparison of naked oats and barley in a silage-based diet for dairy cows. Anim. Prod. 48:636.
SHORT COMMUNICATION: NAKED OATS FOR DAIRY COWS 9 Martin, P. A., and P. C. Thomas. 1988. The manipulation of milk fat composition by including naked oats in a silage-based diet for dairy cows. Proc. Nutr. Soc. 47:96A. 10 Martin, P. A., and P. C. Thomas. 1988. Dietary manipulation of the yield and composition of milk: effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition. J. Sci. Food Agric. 43:145–154. 11 Morris, J. R., and V. D. Burrows. 1986. Naked oats in growerfinisher pig diets. Can. J. Anim. Sci. 66:833–836. 12 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Nat. Acad. Sci., Washington, DC. 13 Ørskov, E. R., and I. McDonald. 1979. The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. J. Agric. Sci. (Camb.) 92: 499–503. 14 Petit, H. V., and G.T.D. Santos. 1996. Milk yield and composi-
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tion of dairy cows fed concentrate based on high moisture wheat or high moisture corn. J. Dairy Sci. 79:2292–2296. 15 Petit, H. V., and G. F. Tremblay. 1995. Ruminal fermentation and digestion in lactating cows fed grass silage with protein and energy supplements. J. Dairy Sci. 78:342–352. 16 SAS® User’s Guide: Statistics, Version 5 Edition. 1985. SAS Inst. Inc., Cary, NC. 17 Tilley, J.M.A., and R. A. Terry. 1963. A two-stage technique for the in vitro digestion of forage crops. J. Br. Grassl. Soc. 18: 104–111. 18 Yang, W. Z., K. A. Beauchemin, B. I. Farr, and L. M. Rode. 1997. Comparison of barley, hull-less barley, and corn in the concentrate of dairy cows. J. Dairy Sci. 80:2885–2895. 19 Zinn, R. A., M. Montan˜o, and Y. Shen. 1996. Comparative feeding value of hulless vs covered barley for feedlot cattle. J. Anim. Sci. 74:1198–1193.
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