Most finishing diets include corn as a primary energy source. If the finishing diet consists mostly of corn, a large proportion of the protein needed by the ruminant is supplied through corn protein. A protein in corn, zein, largely escapes ruminal degradation (60%) and the ungraded fraction is passed into the small intestine for digestion. Since urea and zein act differently in supplying proteins and amino acids to the small intestine of the ruminant, an evaluation of nitrogen retention in lambs was conducted. The objective of this study was to evaluate the effects of diet nitrogen change, time and fasting on nitrogen metabolism by lambs fed urea or zein in a semipurified diet

Hoppe, K. F.

Pritchard, R. H.

English

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South Dakota State UniversityOpen PRAIRIE: Open Public Research Access InstitutionalRepository and Information ExchangeSouth Dakota Sheep Field Day Proceedings andResearch Reports, 1989 Animal Science Reports1989Fed and Fasting Nitrogen Metabolism by LambsFed a Semi-purified Diet Supplemented with Ureaor ZeinK. F. HoppeSouth Dakota State UniversityR. H. PritchardFollow this and additional works at: http://openprairie.sdstate.edu/sd_sheepday_1989This Report is brought to you for free and open access by the Animal Science Reports at Open PRAIRIE: Open Public Research Access InstitutionalRepository and Information Exchange. It has been accepted for inclusion in South Dakota Sheep Field Day Proceedings and Research Reports, 1989 byan authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For moreinformation, please contact michael.biondo@sdstate.edu.Recommended CitationHoppe, K. F. and Pritchard, R. H., "Fed and Fasting Nitrogen Metabolism by Lambs Fed a Semi-purified Diet Supplemented with Ureaor Zein" (1989). South Dakota Sheep Field Day Proceedings and Research Reports, 1989. Paper 4.http://openprairie.sdstate.edu/sd_sheepday_1989/4FED AND FASTING NITROGEN METABOLISM BY LAMBS FED A SEMIPURIFIED DIET SUPPLEMENTED WITH UREA OR ZEIN K .  F .  Hoppe and R. H .  Pritchard Department of Animal and Range Sciences ------------------------SHEEP 89-4 -------------------------Summary The effect two nitrogen sources, urea and zein, have on dry matter digestibility and nitrogen retention was evaluated using a semipurifed diet . Sixteen Hampshire ram lambs were adapted to either a urea (USPD) or zein (ZSPD) supplemented semipurified diet (12% CP) . Lambs were adapted to the USPD for 12 days prior to abruptly changing (day 13) the diet for eight lambs to ZSPD . On day 24, four lambs fed USPD and four lambs fed ZSPD were fasted for 4 days . Samples of feed, orts, feces and urine were collected daily during days 12 to 17 and 24 •to 28 and analyzed for nitrogen content . Dry matter digestibility (DMD) was greater (P< . 01) for USPD than ZSPD (67.7 vs 60 . 7% + 1 . 09) after an abrupt diet change . Twelve days after a diet change, DMD of USPD and ZSPD was similar . This indicates protein source affects digestibility, although with adaptation, the effect of protein source on DMD was diminished . Nitrogen digestibility of USPD was greater ( P< . 01) than ZSPD . Urinary nitrogen output was greater (P< . 01) in lambs fed USPD than ZSPD (11 . 1  vs 5. 7 g/day ± . 42) . Greater nitrogen retention (P< . 01) in lambs fed ZSPD than USPD (5. 9 vs 2 .  0 g/day ± . 57) indicated a combination of microbial and escape feed protein enhanced nitrogen retention compared to microbial protein . Fasting affected nitrogen balance with decreased urinary nitrogen output within 2 days of fasting . Although a 12% CP diet • Prepared for Sheep Day, June 9, 1989 . 15 was fed, nitrogen balance data suggest protein quality or quantity was limited in the USPD . (Key Words: lambs, zein, Semipurified diet, nitrogen, fasting . )  Introduction Supplemental protein sources are included in many ruminant diets . For ruminants fed finishing diets, urea is a commonly used, relatively inexpensive nitrogen source . Since urea cannot be utilized directly by the ruminant, the ruminant relies on rumen microbes to convert urea into microbial protein . The microbial protein is then used by the ruminant as a source of protein . Most finishing diets include corn as a primary energy source . If the finishing diet consists mostly of corn, a large proportion of the protein needed by the ruminant is supplied through corn protein . A protein in corn, zein, largely escapes ruminal degradation (60%) and the undegraded fraction is passed into the small intestine for digestion . Since urea and zein act differently in supplying proteins and amino acids to the small intestine of the ruminant, an evaluation of nitrogen retention in lambs was conducted . The objective of this study was to evaluate the effects of diet nitrogen change, time and fasting on nitrogen metabolism by lambs fed urea or zein in a semipurified diet . Experimental Procedure S ixteen , 4 - month - old Hampshire ram lambs (33.5 kg) were gradually adapted for 2 weeks to a semipurified diet1 (Table 1) containing urea (USPD ) . Lamb dry matter ( DM) intake was then s tabi l ized for 12 days at 3. 1% body we ight . On day 13, e ight lambs were abruptly· switched to a semipur ified diet supplemented with ze in (ZSPD ) . Lambs were then maintained for 12 days on their  respective diets . On day 24, four lambs fed USPD and four lambs fed ZSPD were fasted with access  to water for 4 days . Orts , feces , urine and feed samples were collected daily on days 12 to 17 ( Per iod 1) and days 24 to 28 ( Period 2). Daily feed consumpt ion , feed refusal and fecal and urine output were recorded and sampled for each lamb . Samples were analyzed for DM and N content . Feed and orts were dried in a forced air oven at 100 °C for 48. hours and feces were dried at 60 ° C for 72 hours . Dried samples were then ground through a. 1 mm screen and stored in air tight containers . Urine was collected into vessels  containing 100 ml of  30% HCl (v/v) . Urine output <1000 ml  was diluted to 1 l iter with distilled water . Urine was sampled and s tored at -18 ° C until  nitrogen analys is . Nitrogen content of the feed , feces , orts and urine was determined by the Kjeldahl method . The trial was s tat�st ically analyzed as two experiments , Per�od 1 and Period 2. Both periods were analyzed as a completely random des ign with diet , .day and diet x day effects included in "the analys is of variance . The main e ffec ts for Period 2 were die t , treatment ( fast ing vs fed) and day . All pos s ible two- and three -way interactions were included in the model . The error term used was the res idual error remaining after the main effec t  and interaction e ffects were removed .  Means were separated us ing T tests  only when � s ignificant F value was calculated for main effec ts or interactions . TABLE 1. COMPOSITION OF S EMIPURI FIED DIET SUPPLEMENTED WITH UREA OR ZEIN AS PROTEIN SOURCES Nitrogen source Ingredients. % DM Urea Ze in Corn cobs 29.932 27.355 Corn s tarch 30.951 28.374 Solka floe 27.931 25.354 Urea 4.269 0 Zein8 0 12.000 Animal fat 2.499 2.499 Masonex 2.000 2.000 Dicalb 1.490 1.490 �S04 .584 .584 Trace mineral salt .300 .300 MgO .017 .017 KI , ppm 1.000 1.000 ZnO , ppm 64.000 64.000 NaSe03• 5H20 ,  ppm .219 .219 Vitamin ADE premix0 .020 .02. 8 Ze in , regular grade , Freeman Industr ies , Inc . , Tuckahoe , NY. b A mixture of mono and dicalc ium phosphate to equal 26.30% Ca and 18.70% P .  c Premix contained 1, 000, 000 USP units vitamin A ,  500, 000 USP uni ts vitamin D and 1, 000 international uni ts vitamin E per . 45 kg . Re sults The effects of an abrupt diet change on dry matter digestib i l i ty and nitrogen retention were evaluated in Period 1 ( Table 2) . After lambs had been adapted to the semipuri fed diet supplemented with urea (USPD ) , a diet change to ze in ( ZSPD )  as the nitrogen source resulted in a 7% decrease (P<.01) in digestibi l i ty of the 1 Feedstuffs generously donated were case in from International Distributing Compan� and masonex from Masonite Corporation . � 16 • Diet USPDC ZSPD SE USPD ZSPD SE USPD ZSPD SE TABLE 2. EFFECTS OF DIET AND DAY ON LAMBS WHEN NITROGEN SOURCE IN A SEMIPURIFIED DIET IS  CHANGED , PERIOD 1 Mean 67.7d 60.78 1.09 19.4d 15.78 .57 5.7d 6.88 .17 67.9 66.3 19.4 18.5 5.9 5.8 Da 2 3 4 Dry matter digestibi l i ty ,  % 66.9 56.3 69.2 61. 3 67.5 57.7 Nitrogen intake , g/day 19.4 13.6 19.4 16.6 19.4 15.7 Fecal nitrogen , g/day 5.8 6.3 5.4 7.0 5.7 7.7 Digestible nitrogen , g/day 5. 67.6 58 :1 19.4 14f2 5.7 7.0 6 67.2 64.6 19.4 15.7 5.8 6.8 2.69 1. 39 .43 . USPD ZSPD SE 13. 6d 8.98 .48 13.4 12.7 13.5 7.2 13.9 9.5 13.6 8.0 13.6 7.2 13.5 8.8 1.18 • USPD ZSPD SE USPD ZSPD SE 12.ld 6 .18 .25 1. 5d 2.88 .49 12.1 10. 51 1.4 2.1 Urinary nitrogen , g/day 12.2 4.8g 13. 5 4.2g 11.8 5.6g Retained nitrogen , g/day 1. 3 2.4 .3 5.3 1. 7 2.3 10.9 6 ;lg .. 2.7 1.0 12.1 5.2g 1.4 3.6 .63 1. 22 8 Lambs were fed urea supplement on day 1, zein lambs were fed ze in days 2 to 6. b S tandard error . c USPD -urea supplemented semipurified diet , ZSPD - zein supplemented semipurified diet . d,e Means with unl ike superscripts within column and dependent v&riable differ, P<.01. f,g Means with unlike superscripts for day and within row differ .( P<. 01) . 17 semipuri fied diet (USPD 67 . 7 ,  ZSPD 60 . 7 % ± 1 .  09 ) . The abrupt change in nitrogen source caused a reduced intake of the ZSPD which resulted in a decrease (P< .  01 ) in nitrogen intake (USPD 19 . 4 ,  ZSPD 15 . 7  g/day ± . 5 7 ) . Fecal nitrogen was greater (P< . 0 1 )  for lambs fed ZSPD than USPD ( 6 . 8  vs 5 . 7  g/day ± . 17 ) . Although the presence of zein was not measured directly , the increase in fecal nitrogen for ZSPD suggests poorer util ization of ze in -N  by the animal . Ni trogen digestion was less (P< .  0 1 )  for ZSPD than USPD ( 7 . 8  vs 1 3 . 6  g/day ± . 48 ) . This indicates greater absorption of nitrogen from the USPD . Urinary nitrogen losses for USPD were greater (P< . 01 )  than the ZSPD ( 12 . 1  vs 6 . 1  g/d ± . 2 5 ) . Although the nitrogen digestibi l i ty was greater for USPD , urinary nitrogen losses  with USPD resulted in less nitrogen retention than lambs fed ZSPD ( 1 . 5  vs 2 . 8  g/day ± . 49 ) . The greater nitrogen retention by ze in- fed lambs poss ibly indicates lambs were better able to util ize the amino ac id nitrogen suppl ied in the ZSPD containing a mixture of microb ial and non r um i n a l l y d e g r a d e d  p r o t e i n . Alternatively , a diet containing urea as the nitrogen source has nitrogen lost into the ur ine as a result of e i ther nitrogen not be ing incorporated into the microb ial prote in and eventually lost as ur inary nitrogen or that the qual ity of the microb ial prote in is not as good as a comb inat ion of microbial prote in and zein .  A comparison between feeding or fasting effects on nitrogen retention by lambs previously fed USPD or ZSPD was conducted in Period 2 (Table 3 ) . In Per iod 2 ,  lambs were fed USPD or ZSPD on day 1 with subsequent fasting days 2 to 4 for one -half of the lambs fed USPD and ZSPD . Twelve days after a diet change (Period 1 ) , dry matter digestibil ity of the ZSPD was not different (P< .  0 1 )  from the USPD ( 6 5 . 2  vs 6 6 . 6% ± 1 . 41 ,  respect ively) . Daily nitrogen intake by lambs was s imilar (P< . 01 )  for USPD and ZSPD ( 19 . 4  vs 19 . 5  g/day ± . 41 ) . As observed in 18 Period 1 ,  dai ly fecal nitrogen output wa� higher (P< . 01 )  for lambs fed ZSPD than USPD ( 7 . 8  vs 6 . 2  g/day ± . 32 ) . Fas ting decreased ( P< . 01 )  fecal nitrogen output (Table 4 )  from 5 . 8  g ,  day 1 ( fed) , to 3 . 9  g ,  day 2 ( 24 -hour fast ) . Fecal nitrogen was further decreased (P< . 01 )  by fas ting an additional 24 hours ( 1 . 5  g ,  day 3 ) . Nitrogen digestibi l i ty of diets containing urea was higher ( P< .  01 ) than ze in . However ,  ur inary losses of nitrogen were higher for USPD than ZSPD ( 1 1 . 1  vs 5 . 7  g/day ± . 42 ) . Upon fas ting , lambs previously fed USPD decreased ( P< . 01 )  ur inary nitrogen output from 13 . 0  g/day ( day 1 ,  fed)  to 6 . 8  g/day ( day 2 ,  24 -hour fas t ) . Urinary nitrogen output by lambs fed ZSPD did not change ( P> . 05 )  when fasted . . This indicates metabol ic turnover of nitrogen is  s imilar between fed and fasted for ZSPD lambs . Although nitrogen turnover is  s imilar , different mechanisms may be respons ible for nitrogen loss . When nitrogen retent ion is pos it ive , urinary nitrogen losses are presumably from catabol ism of prote ins and. amino ac ids or from excess  ammonia escaping the rumen . During fas t ing , ammonia loss from the rumen would be minimal . Consequently , urinary nitrogen losses would be from prote in degradation .  S ince ur inary nitrogen losses are s imilar when ZSPD lambs were fed or fasted , the portion of ur inary nitrogen loss from lambs fed ZSPD due to ruminal ammonia may be minimal . However ,  lambs fed USPD had urinary nitrogen losses greater than ZSPD . This indicates diets supplemented with urea may not incorporate all urea into microbial prote in . High ammonia concentrations in the rumen with urea diets were observed in a previous study us ing the semipurified diet . USPD nitrogen absorbed from the rumen as ammonia and excreted in the ur ine would partially explain the higher nitrogen digest ibi l i ty observed previously . The decrease in nitrogen retention for USPD may be a result of nitrogen not be ing incorporated into microbial prote in . Excess nitrogen was then excreted from th� body as urea via urine . Microb ial prote in�· may have a lower qual ity , an imbalance in • TABLE 3 .  EFFECT OF DAY ON FED OR FASTED LAMBS PREVIOUSLY FED UREA OR ZEIN AS NITROGEN SOURCE IN A S EMIPURIFIED DIET , PERIOD 2 Dal SE6 Trt Mean la 2 3 4 5 Dry matter digestibi l i ty ,  % Fed x USPDc 6 5 . 2  6 2 . 5  6 6 . 0  6 7 . 2  6 5 . 3  64 . 8  3 . 1 7 Fed x ZSPD 6 6 . 6  64 . 7  64 . 2  6 9 . 9  6 5 . 9  6 8 . l  Fasted x USPD 1 2 . 9  64 . 5  0 0 0 0 Fasted x ZS PD 1 2 . 2  6 1 . 5 0 0 0 0 SE  1 . 41 Nitrogen intake , g/day Fed x USPD 1 9 . 4  1 9 . 4  1 9 . 4  1 9 . 4  1 9 . 4  1 9 . 4  . 9 2 Fed x ZSPD 1 9 . 5  1 9 . 7  1 9 . 8  1 8 . 7  1 9 . 1  2 0 . 3  Fasted x USPD 3 . 8  1 9 . 4  0 0 0 0 Fasted, x ZSPD 2 . 5  1 2 . 8  0 0 0 0 SE  . 41 Fecal nitrogen , g/day Fed x USPD 6 . 2d 7 . 0  6 . 5  6 . 0  5 . 7  5 . 7  . 7 3 Fed x ZSPD 7 . 88 8 . 5  8 . 5  6 . 4  7 . 9  7 . 7  Fasted x USPD 2 .  7f 6 . 3  3 . 9  1 .  7 . 9  . 5 Fasted x ZSPD 2 .  5f 5 . 3  3 . 9  1 .  5 1 . 0  . 9  SE  . 3 2 • Digestible nitrogen , g/day Fed x USPD 1 3 . 1  1 2 . 3  1 2 . 8  1 3 . 3  1 3 . 6  1 3 . 6  . 9 7 Fed x ZSPD 1 1 . 7 1 1 . 2 1 1 . 2  1 2 . 3  1 1 . 1  1 2 . 6  Fas ted x US PD 1 . 1  1 3 . 0  - 3 . 9  - 1 .  7 - . 9 - . 5  Fas ted x ZSPD . 1  7 . 5  - 3 . 9  - 1 .  5 - 1 .  0 - . 9 SE  . 4 3 Urinary nitrogen , g/day Fed x USPD 1 1 . ld 1 1 . 3 1 1 . 9  10 . 2  1 1 . 4  1 1 . 2 . 94 Fed x ZSPD 5 . 78 6 . 4 5 . 3  5 . 2  5 . 8  5 . 7  Fas ted x USPD 7 .  6f 1 3 . oh 6 .  8 i 5 . 8 i 6 .  5 i 5 . 6 i Fas ted x ZSPD 6 . 49 5 . 6  7 . 4 6 . 9  6 . 1  5 . 6  SE  . 42 Retained nitrogen , g/day Fed x USPD 2 . 0d 1 .  3 . 9  3 . 1  2 . 2  2 . 3  1 . 2 8 Fed x ZSPD 5 . 98 4 . 7  5 . 8  7 . 0  5 . 3  6 . 8  Fas ted x USPD - 6 .  4f . 0  - 10 . 8  - 7 . 5  - 7 . 5  - 6 . 2  Fas ted x ZSPD - 6 .  4f 1 .  8 - 1 1 .  9 - 8 . 5  - 7 . 2  - 6 . 6  SE  . 5 7 8 Fas ted lambs were fed on day 1 and fasted on days 2 to 5 .  b Standard error . c USPD = urea supplemented semipurified diet , ZSPD - zein supplemented semipurified diet . • d,�,f,g Means with unl ike superscripts within column and dependent variable differ h , i  Means with unl ike superscripts within row differ ( P< .  01 ) . ( P< . 0 1 )  . 1 9  TABLE 4 .  EFFECT OF FEEDING OR FASTING ON LAMBS WHEN PREVIOUSLY FED UREA OR • ZEIN AS NITROGEN SOURCE IN A S EMIPURIFIED DIET , PERIOD 2 Da Trt 1 2 3 4 5 SE8 Dry matter digestibi l i ty ,  % Fed 6 3 . 6  6 5 . 1  68 . 5  6 5 . 6  66 . 5  2 . 24 Fastedb 62 . 9c od od od od Mean 6 3 . 3c 3 2 . 5d 34 . 2d 3 2 . 8d 3 3 . 2d 1 .  58  Nitrogen intake , g/day Fed 19 . 5  19 . 6  19 . 0  19 . 2  19 . 8  . 6 5 Fas ted 16 . le od od od od Mean 17 . 8c 9 . 8d 9 . 5d 9 . 6d 9 . 9d . 46 Fecal nitrogen , g/day Fed 7 . 7  7 . 5  6 . 2  6 . 8  6 . 7  . 5 1 Fasted 5 .  8c 3 . 9d 1 .  68 1 . 08 . 78 Mean 6 . 7c 5 . 7d 3 . 98 3 . 98 3 . 78 . 3 6 Digestible nitrogen , g/day Fed 11 . 8  12 . 0  12 . 8  12 . 4  13 . 1  . 6 8  • Fasted 10 . 2c - 3 . 9d - 1 .  6d8 - 1 . 08 - . 78 Mean 1 1 . oc 4 . 0d 5 . 5d 5 . 6d 6 . ld . 48 Urinary nitrogen , g/day Fed 8 . 7  8 . 6  7 . 7  8 . 6  8 . 5  . 6 6 Fasted 9 . 3c 7 . 4d 6 . 3d 6 . 3d 5 . 6d Mean 9 . 0d 8 .  ocd 7 . 0d 7 . 4d 7 . 1  d . 47 Retained nitrogen , g/day Fed 3 . 0  3 . 4  5 . 0  3 . 7  4 . 5  . 90 Fas ted . gc - 1 1 . 3d - 8 . 08 - 7 .  38 - 6 . 48 Mean 1 .  gc - 3 . 9d - 1 . 48 - 1 . 88 - . 98 . 64 8 Standard error . b Fas ted lambs were fed on day 1 and fasted days 2 to 5 .  c,d ,9 Means with unlike superscripts within row and day differ ( P< . 01 ) . • 20 .amino ac id ratios , than needed by the lamb for greater nitrogen retention . • • The higher nitrogen retention for lambs fed ZSPD than USPD may be from the greater quantity of  microbial and ze in prote in available to the animal with the ZSPD . Also , there may be an improvement in prote in qual ity suppl ied to the animal from the comb ination of microbial and zein prote ins which may have caused an increase in nitrogen retention for ZSPD . The greater nitrogen retention observed in ZSPD compared to USPD may be due to different mechanisms in which the 2 1  rumen microbes  and ruminant respond t o  the nitrogen sources .  Nonprote in nitrogen (USPD ) is dependent on incorporation into microbial amino ac ids which are then used as substrate by the ruminant for nitrogen retention . The diet containing ZSPD is only partially degraded in the rumen with the resulting mixture of  microbial prote in and feed prote in providing amino ac ids for nitrogen retention . The increased nitrogen retention by ZSPD indicates the qual ity of prote in is  better than USPD . S ince zein prote in is  cons idered to have a poorer b iological value than microbial prote in , the mechanism for this response requires further cons ideration . 

Fed and Fasting Nitrogen Metabolism by Lambs Fed a Semi-purified Diet Supplemented with Urea or Zein

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Fed and Fasting Nitrogen Metabolism by Lambs Fed a Semi-purified Diet Supplemented with Urea or Zein

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