Animal Feed Science and Technology 87 (2000) 95±103

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1 Animal Feed Science and Technology 87 (2000) 95±103 Effect of feeding undegraded intake protein at a level greater than National Research Council recommendation on the lactational performance of crossbred cows J.V. Manjunatha a,1, U. Krishnamoorthy b, M.M. Kailas b, C.K. Singh a,* a Department of Animal Nutrition, Veterinary College, University of Agricultural Sciences, Hebbal, Bangalore , India b Department of Dairy Production, Dairy Science College, University of Agricultural Sciences, Hebbal, Bangalore , India Received 29 July 1998; received in revised form 3 August 1999; accepted 22 June 2000 Abstract Feeding two levels of undegraded intake protein (UIP) was studied in late lactation crossbred dairy cows, as affecting dry matter intake (DMI), digestibility, nitrogen (N) balance, milk yield and milk composition. The study included a feeding trial and a metabolism trial. The feeding trial was carried out during two periods of 7 weeks in a switch-over design using two groups of four multiparous cows. Group I was fed UIP according to NRC [National Research Council, Nutrient Requirements of Dairy Cattle, 6th Revised Edition. National Academic Press, Washington, DC, pp. 138±147] (NRC-UIP) and Group II received 260 g per day more (HNRC-UIP). The diet consisted of mixed straw of nger millet and paddy (FM-P) and a compound feed mixture (CFM). The roughage DMI for NRC-UIP and HNRC-UIP was 3.83 and 3.66 kg per day, respectively. The 4% FCM yield was equal for the two groups and amounted to 11.1 kg per day. The fat, SNF and protein contents (%) for NRC-UIP and HNRC-UIP were, respectively, 4.53, 8.72, 3.69 and 4.71, 8.73, The roughage DMI, body condition score, milk yield and milk composition were not signi cantly different (P > 0:05). On the other hand, N retention (g per day) in HNRC-UIP (103) was higher than in NRC-UIP (55) (P < 0:01). The results indicated that although N balance improved with feeding higher UIP levels, it had no bene cial effect on roughage DMI, milk yield, milk composition and body condition score. Therefore, it is concluded that in crossbred cows in late * Corresponding author. Tel.: ; fax: address: chandrapal@yahoo.com (C.K. Singh). 1 Present address: Veterinary Dispensary, Begar, Chickmagalur District, Karnataka, India /00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII: S (00)

2 96 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95±103 lactation, with low levels of production, feeding UIP at levels higher than NRC (1989) recommendations is not required. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Undegraded intake protein; NRC; Dairy cows 1. Introduction High producing dairy cows require undegraded intake protein (UIP) because they are unable to consume adequate dry matter (DM) in the form of rumen fermentable energy to synthesise microbial protein in quantities suf cient to meet the lactation requirements (ARC (1984) and NRC (1989)). Therefore, any factor associated with the feed and/or the animal, adversely affecting the rumen fermentable energy and/or degraded intake protein (DIP) intake can increase the need for UIP intake. Although the UIP requirement speci ed by NRC (1989) is approximately 30% higher than that speci ed by ARC (1984), the latter was reported to be adequate for cows producing upto 30 kg of milk per day with a silage diet (Robinson et al., 1991). However, in crossbred cows producing 10± 15 kg milk per day, fed with cereal straw and concentrate, an increase in milk yield was reported with the feeding of UIP at levels higher than the NRC (1989) (Ramachandra and Sampath, 1995). On the contrary, Venkatesh et al. (1998) reported that ARC (1984) protein feeding recommendation was adequate for crossbred cows producing upto 7 kg of milk per day, fed with cereal straw and concentrate. The differences in response to UIP levels in these studies are perhaps attributable to differences in the quality of feedstuffs with reference to the rumen fermentability of organic matter and/or the feeding pattern, which both in uence microbial protein ow to the duodenum. Since the protein requirement of ruminants is met by the microbial protein synthesised in the rumen and the UIP, the response to UIP is rather a re ection of microbial protein ow to the duodenum. In India, the common practice of feeding crossbred cows with low quality roughages ad libitum supplemented with compound feeds, often fails to meet their energy requirements (Nataraja, 1995). Under such circumstances supplemental UIP may improve lactational performance since the microbial protein output is constrained by the low intake of rumen fermentable energy. On the other hand, increasing DMI to assure adequate rumen fermentable energy intake and optimise microbial protein ow to the duodenum would be more meaningful than to feed high levels of UIP in the diet. Therefore, this study was undertaken to assess the response of crossbred cows to two levels of UIP when energy requirement was met by higher allocation of compound feeds as a supplement to straw fed ad libitum. 2. Materials and methods 2.1. Animals and diet Eight nonpregnant multiparous crossbred cows (Holstein Friesian Bos indicus, or Jersey Bosindicus) in late lactation were divided into two comparable groups of four

3 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95± Table 1 Ingredient composition (g kg 1 DM) of the diets a Ingredient NRC-UIP HNRC-UIP FM-P CFM Corn (Deccan variety) Cotton seed meal, s.e Rice bran, s.e Groundnut meal, s.e. 42 ± Coconut meal, s.e Sun ower meal, s.e. 7 ± Molasses Urea 6 7 Common salt 7 7 Mineral mixture a Vitamin A acetate (5000 I U kg 1 ) was added to the compound feed mixture. DM: dry matter; NRC-UIP: NRC (1989) undegraded intake protein; HNRC-UIP: 260 g higher than NRC (1989) undegraded intake protein; FM-P: mixed straw of nger millet and paddy; CFM: compound feed mixture; s.e.: solvent extracted. each based on milk yield, body weight, number of lactations completed and days in lactation (Group I 178, Group II 172). The cows, housed in individual stalls, were provided with similar management practices. The diet included mixed straw of nger millet (Eleucine coracana) and paddy (Oryza sativa) (FM-P) offered ad libitum (6 kg per day) and a compound feed mixture (CFM) as a supplement to provide adequate energy and other nutrients as speci ed by the NRC (1989). The two CFM, I and II were formulated using the published data (Krishnamoorthy et al., 1995) to be identical in metabolizable energy (ME) and DIP but to differ in UIP by increasing the proportion of cottonseed meal s.e. and coconut meal s.e. The ratio of DIP:UIP in CFM I and CFM II was, respectively, 60:40 and 50:50. The protein requirements in terms of DIP and UIP were met according to NRC (1989) in Group I (NRC-UIP) and 260 g more UIP than NRC (1989) recommendation in Group II (HNRC-UIP). The ingredient composition of the CFMs is presented in Table 1. The ingredients of CFM were ground with a hammer mill to pass a 3.36 mm sieve. FM-P and CFM were offered separately. The daily allowance of CFM was calculated based on previous weeks FM-P intake, milk yield, milk fat and body weight. The CFM was fed in two equal portions at 6.00 and h while milking. The cows were milked by hand and were allowed to have free access to water at 8.00 and h. The daily allowance of FM-P straw was offered in portions of 1.5 kg, at 9.00, 16.00, and h. The orts of FM-P straw from each feeding were pooled for the day and weighed at 8.30 h. The orts of CFM, if any, were weighed 1 h after offering Lactation trial (LT) The LT lasted for 14 weeks in two periods in a switch-over design. Each period lasted for 7 weeks with an adjustment period of 2 weeks and an observation period of 5 weeks. Feed intake and milk yield were recorded daily. Samples of FM-P and CFM offered were collected once weekly for determination of DM. 2 or 3 weeks samples were pooled for chemical analyses. Milk samples were taken 1 day per week. The cows were weighed once

4 98 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95±103 in a week, after milking, before having access to water. The body weights were recorded on a weighing platform scale (Avery). The cows were also scored for the body condition at the beginning and at the end of each period, on a ve-point scale (Edmonson et al., 1989) Metabolism trial (MT) A MT lasting for 5 days was conducted in period II, during which daily intake of CFM and FM-P, milk yield and output of faeces and urine were recorded. Faeces and urine were collected manually as and when voided and stored separately until weighed and sampled. Samples of feed offered, feed refusals, faeces and urine were collected every day in the morning. One thousandth by weight of the daily faeces voided by each animal was used for DM determination. DM in the feeds and faeces was determined by drying at 708C to a constant weight. Dried samples from 5 days were pooled, ground through a 1 mm sieve and preserved for chemical analyses and in vitro rumen studies. For Nitrogen (N) determination, the faeces samples (1/1000 of daily voids) were preserved in 25% sulphuric acid for 5 days. Samples of urine (1/500 of total output) from individual animals were collected every day morning for 5 days in a 500 ml Kjeldahl ask containing 15 ml concentrated sulphuric acid and stored at room temperature for N determination Chemical analyses The samples of feed offered, refusals and faeces were analysed for proximate constituents (AOAC, 1984). The neutral detergent bre (NDF) and acid detergent bre (ADF) were determined according to Van Soest et al. (1991). The metabolizable energy (ME) was determined by prediction equations using gas production from in vitro rumen incubation and proximate composition (Menke and Steingass, 1988). Rate of fermentation was calculated from gas production measurement in vitro (Krishnamoorthy et al., 1991). Protease insoluble crude protein (PICP) was determined following Krishnamoorthy et al. (1983), and buffer soluble crude protein (BSCP) according to Krishnamoorthy et al. (1982). Morning and evening samples of milk were pooled in proportion to the corresponding yield. Total solids, protein, and fat (Gerbers method) were determined according to AOAC (1984) Statistical analysis The data of LT were analysed by an analysis of variance (ANOVA) in a switch over design with two periods and two treatments (Federer, 1967). The data of MT were analysed by the Student t-test (Snedecor and Cochran, 1968). 3. Results 3.1. Lactation trial The chemical composition of FM-P and CFM (for the three composite samples collected during the experimental period) is presented in Table 2.

5 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95± Table 2 Chemical composition (g kg 1 DM) of compound feed mixture (CFM) and mixed straw of nger millet and paddy (FM-P) used in lactation trial (LT) and metabolic trial (MT) a CFM FM-P NRC-UIP HNRC-UIP LT MT Organic matter Crude protein Ether extract Total ash Neutral detergent bre Acid detergent bre Acid detergent lignin Metabolisable energy (MJ kg 1 DM) Crude protein (CP) fractions Undegraded intake protein b Protease insoluble CP c Buffer soluble CP d Acid detergent insoluble CP Slow degraded intake protein Gas production (ml/200 g DM/24 h) Rate of fermentation e a DM: dry matter; NRC-UIP: NRC (1989) undegraded intake protein; HNRC-UIP: 260 g higher than NRC (1989) undegraded intake protein. b Calculated from published data (Sampath, 1990). c Krishnamoorthy et al. (1983). d Krishnamoorthy et al. (1982). e Krishnamoorthy et al. (1991) Feed intake, body condition score, milk yield and milk composition The mean daily intakes of DM, crude protein (CP), DIP, UIP, NDF and ADF, average body condition score, milk yield and milk composition for the two groups over 5 weeks are presented in Table 3. The intake of DM, NDF and ADF was not signi cantly different. The change in condition score for NRC-UIP and HNRC-UIP was 0.15 and 0.23, respectively, and was not signi cantly different. The two groups had a similar 4% FCM yield of 11.1 kg day. Milk composition (total solids, fat, solids not fat, protein) was also not signi cantly different Metabolism trial The mean intake, digestion coef cients and N balance for the two treatments are presented in Table 4. The digestibility of all components, as well as TDN and DOMD were lower for the HNRC-UIP than for the NRC-UIP diet, but none of the differences was signi cant (P > 0:05). The daily intake and faecal excretion of N (g per day), although both lower for the NRC-UIP (296, 117) than for the HNRC-UIP (334, 135) group, were not signi cantly different (P > 0:05). The urinary N (g per day) excretion was also lower for NRC-UIP than for HNRC-UIP, being 75 and 43, respectively, and this

6 100 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95±103 Table 3 Body weight, body condition score, intake, milk yield and milk composition for the two groups during the lactation trial (Mean S:E:) a NRC-UIP HNRC-UIP Body weight (kg) NS Body condition score Initial NS Final NS Gain NS Intake (kg per day) Dry matter Roughage 3:83 0:27 3:66 0:38 NS Compound feed mixture 9:28 0:39 9:39 0:40 NS Total 13:1 0:36 13:1 0:34 NS Crude protein 1:58 0:04 1:84 0:04 S Degraded intake protein 0:94 0:04 0:94 0:04 NS Undegraded intake protein 0:64 0:03 0:90 0:04 S Slow degraded intake protein 0:47 0:03 0:63 0:04 S Neutral detergent bre 5:50 0:17 6:08 0:20 NS Acid detergent bre 2:88 0:11 3:01 0:13 NS Milk yield (kg per day) Total 10:2 0:63 10:1 0:63 NS 4% FCM 11:1 0:66 11:1 0:65 NS Milk composition (%) Total solids 13:3 0:25 13:5 0:21 NS Fat 4:53 0:12 4:71 0:13 NS SNF 8:72 0:15 8:73 0:11 NS Protein 3:69 0:14 3:67 0:12 NS a S.E.: standard error; NRC-UIP: NRC (1989) undegraded intake protein; HNRC-UIP: 260 g higher than NRC (1989) undegraded intake protein; NS: not signi cant (P > 0:05); S: signi cant (P < 0:05); FCM: fat corrected milk; SNF: solids not fat. difference was signi cant (P < 0:01). N retention (g per day) in NRC-UIP and HNRC- UIP amounted, respectively, to 55 and 103 and the difference was signi cant (P < 0:01). 4. Discussion The CFM of NRC-UIP and HNRC-UIP were formulated to be similar in ME and DIP but to differ in UIP. The PICP of the two CFMs agreed closely with the UIP content calculated from published dacron bag data (Sampath, 1990) (Table 2). The difference in CP content of the two CFMs is completely attributable to the difference in UIP content. Although both CFMs had similar DIP, the BSCP of CFM I was higher than that of CFM II suggesting that the CFM II supplied more slowly degraded intake protein (SDIP) (SDIP ˆ CP UIP BSCP). The HNRC-UIP group received 260 g more UIP than the NRC-UIP group (Table 3). While the DIP supplied to both groups was similar and

7 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95± Table 4 Body weight, intake, digestibility, Nitrogen (N) balance and metabolic matter (NDS) for the two groups during the metabolism trial a NRC-UIP HNRC-UIP Body weight (kg) NS Intake (kg DM per day) Roughage 4:79 0:19 4:63 0:41 NS Compound feed mixture 8:68 0:38 8:80 0:43 NS Total 13:5 0:19 13:4 0:34 NS Digestibility (%) Total digestible nutrients NS DOMD NS Nitrogen balance (g per day) N intake NS N output Milk NS Faeces NS Urine S N retained S Faecal NDS (kg per day) 2:32 0:28 2:69 0:11 NS Faecal N:NDS a NDS: neutral detergent solubles; NRC-UIP: NRC (1989) undegraded intake protein; HNRC-UIP: 260 g higher than NRC (1989) undegraded intake protein; DM: dry matter; DOMD: digestible organic matter in dry matter; NS: not signi cant (P > 0:05); S: signi cant (P < 0:01). exceeded the NRC (1989) requirement (800 g per day) by 200 g, the UIP supplied to both NRC-UIP and HNRC-UIP was in excess of the recommendation (561 g per day) by 159 and 419 g, respectively (Table 3). The additional UIP did neither in uence total DMI nor the roughage DMI. This is consistent with the observations of Ramachandra and Sampath (1995). A similar milk yield and milk composition for the two groups suggests that feeding UIP at levels higher than the NRC recommendation is not bene cial. Increase in milk yield on feeding more UIP was reported in cows when ME intake was lower as a consequence of low concentrate feeding (érskov et al., 1981). In the present study, the cows were fed to be in positive energy balance. The mean ME intake during the LT, calculated with the ME content of the diets obtained in the MT and corrected for level of intake (9.87 and 8.88 MJ kg 1 DM for NRC-UIP and HNRC-UIP, respectively) (NRC, 1989; Nataraja, 1995), amounted to 129 and 116 MJ per day for NRC-UIP and HNRC-UIP, respectively. The ME supplied to the NRC-UIP and HNRC-UIP groups exceeded 23 and 10 MJ, respectively, above the maintenance and milk production requirements (NRC, 1989). The body condition score and positive N balance observed in both groups also suggest an adequate energy intake. Although feeding additional UIP did not in uence DMI, milk yield and composition, this resulted in a signi cant increase in N retention. In spite of ME available for gain in NRC-UIP was higher (23 MJ) than in HNRC-UIP (10 MJ), N retained was signi cantly

8 102 J.V. Manjunatha et al. / Animal Feed Science and Technology 87 (2000) 95±103 (P < 0:01) higher in HNRC-UIP (55 versus 103 g per day). This may be explained by a higher post-ruminal delivery of amino acids. However, one would calculate that for a gain of 48 g N, a dietary supply of 637 g digestible postruminally available protein is required. Because the excess UIP supplied in HNRC-UIP diet was only 260 g (compared to NRC- UIP), which is partly indigestible, higher N retention cannot be justi ed by the higher level of UIP alone. This could be explained by an increase in microbial protein ow to the duodenum, as re ected by the higher output (kg per day) of faecal neutral detergent solubles (NDS) in HNRC-UIP (2:69 0:11) than in NRC-UIP group (2:32 0:28) (Table 4). Faecal NDS largely represent undigested microbial cell walls (Van Soest, 1982). Although the ratio of faecal N to faecal NDS was about 2% lower than expected (Van Soest, 1982), it was similar for both groups. The total OM digestibility was marginally lower in HNRC-UIP, whereas, the rate (k) of OM fermentation in the rumen was higher (0.108), as compared to NRC-UIP (0.094) (Table 2). Consequently, the total fermentable organic matter in the rumen can be expected to be similar for the two groups because of similar DMI. Therefore, the nature of DIP, may have in uenced the microbial protein production in the rumen. Although the two groups received similar amounts of DIP (1.02 and 1.01 kg per day) (Table 3), the SDIP (kg per day) was higher in HNRC- UIP (0.63) than in NRC-UIP (0.47). This might have increased the ef ciency of microbial protein synthesis through a better synchronisation between energy and N availability in the rumen. Slower degradation of N in the rumen is reported to increase microbial protein ow to the duodenum (ARC, 1984). Since the total protein requirement is met from microbial protein and the UIP, a substantial reduction in UIP feeding can be achieved by increasing microbial protein ow to the duodenum. Such an approach would be more meaningful than attempting to deliver UIP to the duodenum. With NRC-UIP, the N retention (g per day) was 55 which is an unwanted luxury under conditions of chronic feed shortage. Similarly, Venkatesh et al. (1998) reported a N retention of 4 and 39 g per day for crossbred cows fed on a straw based diet according to ARC (1984) and NRC (1989) recommendations, respectively, although there was no difference in milk yield and milk composition. The recommendations for protein feeding of ARC (1984) are about 30% lower than those of NRC (1989). The former were also found to be adequate for medium production levels with silage based diets (Robinson et al., 1991). So, our ndings and the above mentioned studies suggest that there is scope for reducing UIP to levels lower than NRC (1989) recommendation for cows in late lactation producing 10 kg of milk per day, fed on low quality roughages, when adequate energy intake is assured through higher allocation of concentrate feeding. Acknowledgements The authors wish to thank M/s Mysore Feeds Pvt. Ltd. Bangalore, India, for providing the supplements. This work was a part of the project `Studies on nitrogen utilisation in ruminants' (DR/UAS/DP/9 & 11/96) jointly sponsored by the Alexander von Humboldt Foundation, Germany, in the form of equipment donation and the University of Agricultural Sciences, Hebbal, Bangalore, India.

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