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Development and evaluation of polymer coated urea as a potential slow-release urea supplement for ruminantsUpton, Erlanda January 1999 (has links)
Thesis (MScAgric)--Stellenbosch University, 1999. / ENGLISH ABSTRACT: The rate of hydrolysis of urea in the rumen of animals is a major limitation when
considering the substitution of natural protein with urea in the formulation of rations.
The aim of this study was to evaluate polymer coated urea prills with variable coating
thickness and evaluate its potential as a slow-release NPN compound. A new slowrelease
urea compound, made by coating prilled feedgrade urea with a co-polymer
of urea-formaldehyde resin and a castor-coconut alkyd was initially evaluated for
urea-nitrogen concentration in distilled water in order to evaluate its potential as a
slow-release urea product for ruminants. Amino/alkyd or polyester blends are
among the cheapest of the modern synthetic systems and are considered because it
is non-toxic, low-cost, biodegradable and easy to manufacture. A 2 x 2 x 2 x 2
factorial design was used and 16 individual products were made and evaluated. The
Wurster method was used to encapsulate urea prills. The slopes of the urea release
curves represented the release rate of the encapsulated products and were
compared to identify the process variables, which had an effect on release rate. Two
of the coating variables, coating weight and alkyd: resin ratio, had a major effect (P =
0.0001) on the release rate of urea. The crushing strength of encapsulated products
was significantly (P = 0.0001) higher than that of untreated urea. Results motivated
the evaluation of the products in the rumen of sheep in terms of rumen ammonia and
blood urea N concentrations. Four slow-release products were made after
interpreting results from the first study, and differed on account of the coating weight and the composition of the co-polymer. Fifteen fistulated wethers were randomly
allotted into 5 groups and intraruminally received an equivalent of 15g urea. Rumen
ammonia and blood ammonia were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48
h after administration of the various treatments. Slow release urea (SRU) resulted in
significantly lower rumen ammonia peaks (P = 0.0001) than untreated urea, while the
peaks were also significantly delayed. Untreated urea resulted in the maximum
concentration at two hours after administration of the urea (P = 0.0685) while the
SRU's reached a maximum at six hours after administration in the rumen. No
significant differences between the four different SRU types were found. Responses
in blood urea-N was similar to that observed for rumen ammonia nitrogen. The
encapsulation was effective in decreasing the rate of ammonia release from the urea
for up to six hours after administration. In a third trial four Dehne Merino wethers
were used in a 2 x 2 Latin square design. They received a SRU product equivalent to
0.4 g urea per kg body weight orally. Rumen liquor and blood samples were taken at
0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after intake. Difficulty was initially
experienced with ingestion and palatability of the SRU products due to the strong
formaldehyde and butanone odour present in the coating. The maximum rumen
ammonia (NH3) concentration for the SRU were lower than that of untreated urea
(17.5 mg N/dl vs. 66.9 mg N/dl). The time to reach blood urea levels also differed
considerably (6 h vs. 24 h for blood urea nitrogen) between treatments.
The encapsulation of urea prills shows potential solutions to reduce the solubility of
urea and also reduce the hygroscopic nature of urea and improve the palatability and
storage characteristics thereof.
Keywords: Slow-release urea, encapsulate, copolymer, urea formaldehyde rumen
ammonia, blood urea nitrogen, solubility, palatability, storage characteristics. / AFRIKAANSE OPSOMMING: Die vinnige tempo waarteen ureum in die rumen na ammoniak omgesit word, is die
grootste beperking in die optimale benutting van ureum, as vervanging van
natuurlike protein in herkouerrantsoene. Die doel van hierdie studie was om 'n
stadig vrystellende ureumproduk te ontwikkel wat die rumenammoniakvlak
gedurende 'n aansienlike periode van die dag bokant 'n sekere vlak kan hou. 'n
Nuwe stadig vrystellende ureumproduk, vervaardig deur ureumkorrels met 'n
kopolimeer van ureum-formaldehiedhars en 'n kastor-en klapperalkied te bedek, is
geevalueer om die potentiaal as stadig vrystellende nie-protein stikstof (NPN)-produk
vir herkouers te ondersoek. Die veiligheid, biodegradeerbaarheid, lae koste en
maklike vervaardiging van amino/alkied-kopolimere maak dit een van die
goedkoopste sintetiese sisteme om vir stadig vrystellende sisteme te oorweeg. 'n 2
x 2 x 2 x 2 Faktoriale antwerp is gebruik om 16 individuele produkte te vervaardig.
Die Wurster-metode is gebruik om individuele korrels te enkapsuleer met die
polimeer en die potentiaal van die produkte is aanvanklik geevalueer deur die
ureumstikstofvrystelling in gedistilleerde water te meet. Die hellings van die
vrystellingsgrafieke is vergelyk om die veranderlikes te bepaal wat die grootste
invloed op die vrystellingstempo van ureum uit die ge·inkapsuleerde produkte het.
Resultate dui dat twee verandelikes 'n betekenisvolle effek het op die vrystellingstempo, nl. dikte van die omhulsel, en die samestelling van die kopolimeer
(P = 0.0001 en P = 0.0135, onderskeidelik) het. Die samedrukbaarheid van die ge
·lnkapsuleerde produkte was ook betekenisvol hoer (P = 0.0001) as die van
onbehandelde ureumkorrels, wat lei tot verbeterde bergings- en
hanteringseienskappe. lnterpetering van resultate lei tot die vorming van vier stadig
vrystellende produkte. Vyf groepe van 3 volwasse rumengefistuleerde
Dohnemerinohamels is in 'n proef gebruik om die potentiaal van die produkte verder
te ondersoek. 'n Ekwivalent van 15 g ureum is direk in die rumen van elke dier
geplaas en ammoniak-en bloed monsters is 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 & 48
ure na dosering geneem. Die stadig vrystellende ureumprodukte het 'n betekenisvol
laer maksimum waardes vir beide ammoniak-en bloedstikstofureum getoon (P =
0.0001 ). Onbehandelde ureum het 'n maksimum rumenammoniakstikstof
konsentrasie reeds twee ure na toediening bereik in vergelyking met ses ure vir die
stadig vrysellende produkte. Geen betekenisvolle verskille in hierdie parameters is
tussen die ge·lnkapsuleerde produkte gevind nie, terwyl geen interaksie is tussen
hoofeffekte voorgekom het nie. In 'n derde proef is vier Dohnemerinohamels gebruik
om die vrystellingstempos, in terme van rumenammoniak-en bloedureumstikstof te
bepaal waar die stadig vrystellende produk en onbehandelde ureum direk aan die
diere gevoer is . 'n Ekwivalent van 0.4 g ureum/kg liggaamsmassa is gevoer.
Aanvanklik is inname- en smaakliksheidprobleme ondervind, moontlik as gevolg van
die sterk butanoon-en formaldehiedreuk van die omhulsel. Die
rumenammoniakstikstof het 'n laer maksimum (17.5 vs. 66.9 mg N/1 00 ml) as die
van onbehandelde ureum gehad terwyl die tyd wanneer maksimum konsentrasie
bereik word ook aansienlik later was. Die polimeer inkapsulering van ureumkorrels
toon potensiaal as 'n stadig vrystellende ureumproduk deurdat dit die oplosbaarheid
van ureum in die rumen verlaag. Bykomende voordele is dat die omhulsel die
higroskopisiteit verlaag en die samedrukbaarheid verhoog, beide eienskappe wat die
hantering-en bergingseienskappe bevorder.
Sleutelwoorde: Stadig vrystellende ureum, enkapsulering, kopolimeer, ureumformaldehied,
rumenammoniak, bloed ureum stikstof, oplosbaarheid, smaaklikheid,
bergingseienskappe.
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The effect of rumen inert fat supplementation and protein degradability in starter and finishing diets on veal calf performance and the fatty acid composition of the meatLategan, Elna 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Six groups each with six Friesian bull calves were used in this investigation and slaughtered
at 20 weeks of age. Calves received a low- (LD) or high (HD) degradable protein diet, each
with or without rumen inert fat supplementation. Two commercial fat sources were used,
Morlae (m) and Golden Flake (gf), included at 2.5% of the diet. A commercial milk replacer
(Denkavit) was fed at 4L for 42 days, followed by 2L until weaning at 49 days of age. The
starter diets were fed ad lib. from day 14 to 10 weeks of age and finishing diets ad lib. from
11 to 20 weeks of age. There were no significant differences in body mass gain or dry matter
intake over the entire 20 week period. The feed conversion ratio (FCR) was improved
significantly (P=0.0032) when fat was supplemented to LD, but not to HD diets. The FCR
(kg dry matter/ kg gain) ofLD, HD, LDm, HDm, LDgfand HDgfdiets were 3.45,3.44,3.07,
3.81, 3.02 and 3.43, respectively. All 36 calves were used in a digestibility trial, using
chromium oxide (Cr203) as a marker, during week 18 of the investigation. Digestibility
values (%) for the six diets (LD, HD, LDm, HDm, LDgfand HDgf) were 61.74, 65.91, 75.44,
69.00, 75.54 and 67.15 for dry matter, 61.44, 61.60, 71.33, 68.23, 75.44 and 66.12 for crude
protein and 58.56, 66.45, 75.98, 70.92, 78.43 and 70.79 for fat, respectively. The dry matter
(P=O.OOOl)and fat (P=O.OOOl) digestibilities were only significantly higher when fat was
added to LD diets. The crude protein (CP) digestibilities were significantly higher when fat
was added to either the LD (P=0.0001) or the HD (P=0.0488) diets.
All the calves were slaughtered at 20 weeks of age and the fatty acid content of the meat (m.
longissimus) and subcutaneous fat layer adjacent to the 12th rib as well as the meat colour,
was determined. The fatty acid composition of the longissimus muscle was changed by
feeding the rumen inert fat sources. The three predominant fatty acids found were palmitic,
stearic and oleic acids. The palmitic acid (CI6:0) content of the muscle and diet was 24.44 &
20.47,25.97 & 22.57,31.06 & 33.23, 30.98 & 37.91, 34.94 & 31.77 and 29.71 & 32.88 of the
total fat for the LD, HD, LDm, HDm, LDgf and HDgf diets, respectively. The C16:0 content
was significantly higher in the muscle of the calves receiving the LD diets supplemented with
fat (P=0.0008). There was also a significant interaction between the two fat sources and
protein degradability (P=0.0065), but only in the LD diets. The stearic acid (CI8:0) content
of the muscle and diet was 14.35 & 5.22, 19.65 & 8.61, 17.29 & 4.68, 22.59 & 5.78, 22.27 &
15.54, and 26.48 & 20.15 of the total fat for the LD, HD, LDm, HDm, LDgfand HDgfdiets,
respectively. The C18:0 content was significantly higher in the muscle of calves receiving the
HD (P=O.OOOl)compared to LD diets. The stearic acid content was also significantly higher
when fat was added to LD (P=0.0042) or HD (P=0.0073) diets. The oleic acid (CI8:1)
content of the muscle and diet was 36.06 & 21.51,39.99 & 21.11,32.21 & 23.67, 29.13 &
24.59, 25.23 & 18.68 and 35.93 & 16.02 of the total fat for the LD, HD, LDm, HDm, LDgf
and HDgf diets, respectively. The linolenic acid (CI8:3) content of the muscle was
significantly higher (P=0.0038) when fat was added to LD diets compared to no fat
supplementation (0.87 vs. 0.15). The CIELAB values indicated that LD diets resulted in more
pink meat. Mean values ofL* =-32.61, 34.19; a* = 7.08, 7.91 and b* = 3.18 and 4.07 were
observed for the LD and HD diets, respectively. Meat from the LD diets had significantly
lower L*-(P=0.0252), a*-(P=0.0283) and b*-(P=0.0109) values compared to meat from the
HD diets. It was concluded that there was a positive response in CP digestibility when rumen
inert fats were supplemented to LD or HD diets, although a greater response was shown in the
LD diets. The FCR, dry matter and fat digestibility were only increased when fat was added
to the LD and not to the HD diets. Similarly, the fatty acid contents of the longissimus
muscle of veal calves can be manipulated with the supplementation of rumen inert fat sources,
but only when combined with a low protein degradable diet. The low degradable protein diets
also produce a more attractive meat colour for the potential veal consumer. / AFRIKAANSE OPSOMMING: Ses behandelings, lae- (LD) of hoë (HD) degradeerbare diëte, elk met of sonder rumeninerte
vetsupplementering, is geëvalueer met ses kalwers in elke groep. Twee kommersiële
vetbronne is gebruik, nl. Morlae (m) en Golden Flake (gf) teen 'n 2.5% insluitingspeil. 'n
Kommersiële melksurrogaat (Denkavit) is aangebied teen 4L1dag tot 42 dae ouderdom,
gevolg deur 2L/dag tot speenouderdom op 49 dae. Aanvangsdiëte is ad lib. aangebied vanaf
14 dae tot 10 weke ouderdom en die groeidiëte ad lib. vanafweek 11 tot 20. Daar was geen
betekenisvolle verskille in die totale massatoename of die droëmateriaalinname nie. Die voeromsettingsverhouding
is betekenisvol verbeter (P=0.0032) in die behandelings waarin
rumeninerte vette by LD diëte ingesluit is, maar nie by die HD diëte nie. Die voeromsettingsverhouding
(kg droëmateriaalinname / kg massatoename) van die LD, HD, LDm,
HDm, LDgf en HDgf diëte was 3.45, 3.44, 3.07, 3.81, 3.02 en 3.43, onderskeidelik. Al 36
kalwers is in 'n verteringsproef gebruik gedurende week 18 van die proef. Chroomoksied
(Cr203) is as merker gebruik. Verteerbaarheidswaardes vir die ses diëte was 61.74, 65.91,
75.44,69.00,75.54 en 67.15 vir droëmateriaal, 61.44, 61.60, 71.33, 68.23, 75.44 en 66.12 vir
ruproteïen en 58.56, 66.45, 75.98, 70.92, 78.43 en 70.79 vir vet, onderskeilik. Die
droëmateriaal- (P=O.OOOl) en vetverteerbaarheid (P=O.OOOI) was slegs betekenisvol hoër
wanneer vet by LD diëte gevoeg is en nie by HD nie. Die ruproteïen (RP) verteerbaarheid
Stellenbosch University http://scholar.sun.ac.za
VI
was betekenisvol hoër (P=0.0002) by LD en HD (P=0.0488) diëte met vet supplementering,
teenoor geen vet insluiting.
Die kalwers is op 20 weke ouderdom geslag en die vetsuursamestelling van die vleis (m.
longissimus) en die subkutane vetlaag teenaan die 12de rib, asook en die vleiskleur, is bepaal.
Die vetsuursamestelling van die longissimus spier is deur die supplementering van
rumeninerte vet verander. Die drie primêre vetsure wat in die vleis voorgekom het, was
palmitiensuur, steariensuur en oleïensuur. Die palmitensuur (CI6:0) inhoud van die spier en
diëte was 24.44 & 20.47, 25.97 & 22.57, 31.06 & 33.23, 30.98 & 37.91, 34.94 & 31.77 en
29.71 & 32.88 van die totale vet van die LD, HD, LDm, HDm, LDgf en HDgf diëte,
onderskeilik. Die C16:0 was betekinisvol hoër in die spiere van kalwers wat die LD diëte met
vet supplementering (P=0.0008) ontvang het. Die steariensuur (CI8:0) inhoud van die spier
en diëte was 14.35 & 5.22, 19.65 & 8.61, 17.29 & 4.68, 22.59 & 5.78, 22.27 & 15.54, en
26.48 & 20.15 van die totale vet vir die LD, HD, LDm, HDm, LDgf en HDgf diëte,
onderskeidelik. Die C18:0 inhoud was betekinisvol hoër in die spiere van die kalwers wat die
HD (P=O.OOOI),teenoor LD diëte ontvang het. Die steariensuur inhoud was ook betekenisvol
hoër wanneer vet by LD (P=0.0042) of HD (P=0.0031) diëte gevoeg word. Die oleïensuur
(CI8:1) inhoud van die spier en diëte was 36.06 & 21.51, 39.99 & 21.11, 32.21 & 23.67,
29.13 & 24.59, 25.23 & 18.68 en 35.93 & 16.02 van die totale vet vir die LD, HD, LDm,
HDm, LDgf en HDgf diëte, onderskeidelik. Die linoleensuur (CI8:3) inhoud van die spier
was betekinisvol hoër (P=0.0038) in die LD diëte met vet teenoor LD met geen vet
supplementering (0.87 vs. 0.15). Die CIELAB waardes van die LD diëte dui op 'n pienker
vleiskleur. Gemiddelde waardes van L* = 32.61 & 34.19, a* = 7.08 & 7.91 en b* = 3.18 &
4.07 is vir die LD en HD diëte, onderskeidelik, waargeneem. Die vleis van die LD diëte het
'n betekenisvol laer L*-(P=0.0252), a*-(P=0.0283) en b*-(P=0.0109) waarde in vergelyking
met die HD diëte getoon. Die resultate dui daarop dat daar 'n positiewe respons in die
ruproteïenverteerbaarheid by die supplementering van rumeninerte vette by LD en HD diëte
voorkom, maar die response op die LD diëte is groter. Die voeromsettingsverhouding,
droëmateriaal- en vetverteerbaarheid is egter net bevoordeel in die LD met vet en nie in die
HD diëte nie. Die vetsuursamestelling van die longissimus spier in die kalf kan gemanipuleer
word met die supplementering van rumeninerte vetbronne, maar slegs wanneer dit
gekombineer word met lae degradeerbare proteïen diëte. Die lae degradeerbare proteïen diëte
produseer ook die mees aanloklike vleiskleur vir die potensiële kalfsvleisverbruiker.
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Feedlot performance and essential amino acid growth requirements of Dorper lambsJurgens, Andre Hendrik 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The Dorper is numerically the second most abundent of all the sheep breeds in
South Africa. It is the most numerous sheep breed in the dry arid areas of South
Africa which make out a very big portion of the natural grazing in South Africa. In this
study the feedlot performance was specifically investigated since so little research
has been done in this regard. In the first study (Chapter 1), the production efficiency,
body components and commercial yield of 13 Dorper and 12 Merino lambs were
investigated. A pelleted diet was fed ad lib and the water intake per day was
measured. Lambs were slaughtered at 30kg and at 40kg live weight and cut up
according to the South African commercial cuts. The weights of the organs, head,
feet, skin and carcass were also recorded. Results from the first study showed that
Dorpers had a lower (P<0.05) water efficiency (285.97 mVkgO75/day) than the
Merinos (240.07 mVkg075/day), but had a higher (P<0.05) nitrogen retention. The
head, feet, skin, heart, lungs, kidneys and diaphragm of Merino lambs were heavier
(P<0.05). Merinos had heavier (P<0.05) breast and shank and thick rib (only at
40kg live weight) cuts. But the Dorper had a significantly heavier hindquarter
(buttock and loin) which is the high-priced cut of any carcass. It seems that the
Dorper will do well under feedlot conditions, and would possibly make a better
commercial meat producer than the Merino under all circumstances.
In the second study (Chapter 2), the free-ranging Dorper on natural grazing were
compared with 7 Dorper lambs in the feedlot study. The essential amino acids in the
duodenal contents were compared. The free-ranging Dorpers were randomly slaughtered at 40 kg live weight and a duodenal sample was collected. The feedlot
Dorpers were also slaughtered at 40 kg live weight and a duodenal sample was
taken. The second study indicated no significant differences between the EAA
composition of the duodenal samples, whether protein quantity was taken into
account (gAA/100g crude protein (CP)) or not (expressed as % of lysine). The
chemical scores indicated that the two most limiting amino acids in the duodenal
digesta for whole empty body growth were: arginine and histidine. Excess levels of
amino acids tend to be present in all three duodenal digesta samples (isoleucine,
leucine, lusine, methionine, phenylalaline, threonine and valine). The whole empty
body EAA composition (g AA/100 g crude protein) was as follows 7.10 arginine; 2.40
histidine; 3.31 isoleucine; 7.22 leucine; 6.61 lysine; 1.62 methionine; 3.91
phenylalanine; 3.77 threonine and 4.85 valine. The composition can serve as an
example of the ideal EAA requirements for whole empty body growth between 30
and 40 kg live weight of Dorper ram lambs. The duodenal amino acid concentrations
of the free-ranging Dorper compared well with those of the feedlot Dorpers which
suggests that the microbial organisms have a big influence on the amino acid
concentration which reaches the intestines. / AFRIKAANSE OPSOMMING: Die voerkraal prestasie en essentiele aminosuur behoeftes van
groeiende Dorper lammers: The Dorper is getalgewys die tweede mees talryke skaapras in Suid-Afrika. Dit is die
mees talryke skaapras wat in die drce woestynagtige gebiede van Suid-Afrika
aangetref word. Die gebiede beslaan die grootste oppervlakte van Suid-Afrika se
natuurlike weiveld. In die studie is voerkraal prestasie van die Dorper nagevors,
spesifiek omdat daar so min navorsing op hierdie gebied gedoen is. In die eerste
studie (Hoofstuk 1) is die produksie doeltreffendheid, liggaams komponente en
kornrnersiele produksie van 13 Dorper- en 12 Merino lammers ondersoek. 'n
Verpilde rantsoen is ad lib gevoer en die water inname per dag is ook gekontroleer.
Die lammers is geslag op 30 en 40 kg lewende gewig en die karkasse is daarna
opgesny volgens die Suid-Afrikaanse kornmersiele karkassnitte. Die resultate van
die eerste studie het getoon dat Dorpers 'n laer water potentiaal (P<0.05) (285 97
mflkgO 75/dag) as die Merinos (240.07 mVkg075/dag) het. Dorper lammers het ook 'n
hoer (P<0.05) stikstof retensie. Die kop, vel, pote, hart, longe, niere en diafragma
van Merino lammers was swaarder (P<0.05). Merinos se brisket en dikrib snitte
weeg ook swaarder (P<0.05). Die Dorper het 'n beduidende swaarder agterkwart
(len de en boud) gehad, wat die duurste snit is van enige karkas. Die Dorper het baie
goed gedoen in die voerkraal toestande en sal waarskynlik onder aile omstandighede
'n hcer vleisproduksie op die Merino lewer. In die tweede studie (Hoofstuk 2), is die vryweiende Dopers op natuurlike weiding
vergelyk met die Dorpers in 'n voerkraal. Die twee groepe Dorpers se essensiele
aminosuur samestelling in hul dunderms is bepaal en vergelyk om te bepaal of daar
enige tekorte teenwoordig is. Die Dorpers in die veld en in die voerkraal is op 40 kg
lewende gewig geslag en monsters van die dunderm inhoud is gekollekteer. Die
monsters is ontleed om te bepaal of daar enige betekenisvolle verskille in die
essensiele aminosure van die dunderm inhoud tussen die veld Dorpers en voerkraal
Dorpers was. Die tweede studie het geen betekenisvolle verskille getoon tussen die
dunderm monsters se essensiele aminosure, of die hoeveelheid proteien (gAA/100g)
in aanmerking geneem is of nie (uitgedruk as % lisien). Die chemiese telling dui aan
dat die twee mees beperkende aminosure in die dunderm inhoud vir lee liggaam
groei arginien en histidien was. Oormaat vlakke van aminosure kom voor in al drie
dunderm inhoud monsters (isoleusien, leusien, lisien, metionien, femielalanien,
treonien en valien). Die totale lee liggaam essensiele aminosuursamestelling (g
aminosuur/100g ruprotein) was soos volg: 7.10 arginien; 2.40 histidien; 3.31
isoleusien; 7.22 leusien; 6.61 lisien; 1.62 metionien; 3.91 fenielalanien; 3.77 treonien
en 4.85 valien. Hierdie aminosuursamestelling kan as 'n aanduiding dien vir die
ideale aminosuurbehoeftes van Dorper ram lammers vir totale lee liggaamsgroei
vanaf 30 tot 40 kg lewende massa. Die dunderm aminosuur konsentrasie van die
Dorper in die veld stem goed ooreen met die van die voerkraal Dorper. Dit toon
waarskynlik dat die mikrobe organismes in die rumen In groot invloed het op die
aminosuur samestelling wat die dunderm bereik.
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The effects of different selenium sources on the meat quality and bioavailability of selenium in lambEsterhuyse, Jacobus Johannes 12 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In many parts of the world, soil is depleted of selenium (Se), leading to selenium-poor plants, animals and, therefore, humans. It was recognised that a study to examine the functionality of new products on the market to address this problem was required.
The purpose of this research were threefold: to compare the effects of sodium selenite (NaSe) and organically bound selenium sources on small ruminant performance, to investigate the bioavailability of these Se sources, and analyse their influence on carcass characteristics, meat quality and antioxidant capabilities. Fourty growing Döhne Merino wethers from the Southern Cape region, a selenium-deficient area, were used for the study. The animals were all fed the same basal diet in the adaptation period and were then allocated to one of four treatment groups: Control (CT), inorganic selenium (IS), organically bound Se A (OSA) or B: (OSB). The period of supplementation was 90 days.
This first study assessed the effect of the different Se sources on growth and Se bioavailability in the wethers. The wethers and the feed they consumed were regularly weighed to determine their growth and feed conversion rate (FCR) in the trial period. To gauge their Se level, blood samples were collected via jugular venipuncture at monthly intervals. The wool around the jugular was shorn and samples were collected on day 0 and day 90 for comparative Se level analysis. Liver, skeletal muscle and kidney samples were collected at day 90, directly after slaughter, to determine the Se level in these tissues.
No effect could be reported in the growth and FCR of the wethers between the supplementation groups. For whole blood Se levels there was an effect in the early part of the study, with a greater increase in Se levels for the organically bound Se groups, but in the end no effect on whole blood levels could be seen between the different Se treatments. Neither could any difference between the inorganic Se and organic bound Se treatments be found in the liver – however, the total Se concentration of the wool, kidney and meat samples was greater in those animals offered organically bound Se when compared with those receiving a comparable dose of inorganic Se.
The second study evaluated the antioxidant capabilities of the different Se supplements in the wethers. Blood samples were taken monthly for plasma collection to test for Glutathione peroxidase (GSH-Px) activity and total antioxidative capacity (TAC) with the oxygen radical absorbance capacity (ORAC) assay. Liver, skeletal muscle and kidney samples were collected at day 90, immediately after slaughter and measured for GSH-Px activity.
With TAC, there was a significant effect for the treatment period between day 0 and day 90, however the treatments did not show any significant difference. No significant differences could be established between the different Se treatments for the GSH-Px analysis in any of the tissues. For the mean plasma values of the treatments no significant differences can be reported, but a significant difference was observed at day 30 in the contrast between the organically bound Se and the other treatment groups.
The third study was to evaluate the quality and lipid oxidation of muscle from those wethers supplemented with different Se sources. Skeletal muscle samples were collected at day 90, directly after slaughter to determine this. No differences in the meat quality of the wethers could be detected between Se sources after the 90-day supplementation period. Lipid oxidation was measured by determining TBA reactive substances (TBARS) and once again no differences could be detected.
Based on the results found in this investigation, it may be inferred that organically bound Se (OSA & OSB) supplementation will hold a number of advantages for small ruminants over inorganic Se supplementation. Animals fed the organically bound Se had reached adequate Se levels sooner on the organically bounded treatments than the inorganically bounded treated animals. The greater bioavailability of organically bounded Se over inorganic Se was proven by the increased Se levels in certain tissues and organs. Additionally, only the organically bounded Se could find a pathway to the wool, confirming that it was carried in an organic form (probably selenomethionine) in the body. Organically bound Se will therefore have a positive impact on small ruminant health and production, which will result in an indirect advantage for consumer health. / AFRIKAANSE OPSOMMING: Die grond in groot dele van die wêreld word selenium-arm en dit lei na selenium-arm plante, diere en mense. Dit is waargeneem dat ‘n studie wat kyk na die funksionaliteit van nuwe produkte op die mark om die probleem aan te spreek nodig is.
Die doelwit van die studie was om verskillende selenium (Se) bronne te vergelyk en die uitwerking daarvan op klein herkouer prestasie te evalueer. Daar is gekyk na die biobeskikbaarheid, invloed daarvan op die karkas eienskappe en antioksidant vermoëns van die verskillende Se bronne. Veertig groeiende Dohne Merino-hamels van die Suid-Kaap-streek, 'n Se arm gebied is gebruik vir die studie. Die diere is almal dieselfde basale dieet gevoer in die aanpassing periode en dan toegeken aan een van vier behandelings: kontrole (CT), anorganiese Se (IS), organies gebinde Se A (OSA) of B: (OSB). Die tydperk van die aanvulling was 90 dae.
In die eerste studie is gekyk na die effek van die verskillende bronne van Se op die groei en die biobeskikbaarheid daarvan aan die hamels. Die hamels en voer verbruik, is gereeld geweeg sodat hul groei en voer omset verhouding (VOV) in die proef tydperk te bepaal. Bloedmonsters is versamel deur middel van die jugulêre venipuncture vir die Se vlak bepaling daarvan. Lewer, skeletspier en nier monsters is versamel op dag 90, direk na die slagting vir die Se vlak bepaling. Die wol rondom die nekslagaar is geskeer en monsters is versamel op dag 0 en 90 vir Se vlak analise.
Geen effek kan gerapporteer word vir die groei en VOV van die hamels tydens die aanvullings periode nie. Vir die bloed Se vlakke was daar 'n uitwerking in die vroeë deel van die studie, met 'n vinniger toename in Se vlakke vir die organies gebinde Se groepe, maar aan die einde kon geen effek gesien word tussen die verskillende Se behandelings nie. Geen verskil tussen die NaSe en organiese gebonde Se behandelings kon gevind word in die lewer nie. Die totale Se konsentrasie van die wol-, nier-en vleis
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Specialized feeding of lambs for optimized performance during the finishing phaseMoolman, Justin 04 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of this study was to determine whether a lamb finishing ration that is
balanced for essential amino acids (EAA), at a specific level of non-structural
carbohydrates (NSC) would yield better feedlot performance when compared to a
standard commercial finishing ration.
Metionine (Met) and Lysine (Lys) were identified as the first limiting amino acids for
growing lambs. These two amino acids, as well as Threonine (Thr), Arginine (Arg),
Leucine (Leu), Isoleucine (Ile) and Phenylalanine (Phe) were included in an
optimized protein (OP) feedlot ration at optimal levels. This ration was formulated to
contain 157 g/kg crude protein (CP) and 477 g/kg NSC, with Met, Lys, Arg and Thr at
2.48, 7.45, 8.51 and 8.12 g/kg on dry matter (DM) basis respectively. The second
treatment, FIN, was a standard commercial lamb finishing feed without optimized
amino acids and contained similar total protein and NSC to OP of 152 g/kg CP and
468 g/kg NSC but with Met, Lys, Arg and Thr at 2.08, 5.49, 7.47 and 4.80 g/kg on
DM basis respectively. A third treatment, a low protein (LP) diet served as a positive
control and was formulated on lower specifications (139 g/kg CP, 455 g/kg NSC) and
was also not optimized for amino acids. This treatment contained Met, Lys, Arg and
Thr at 1.93, 4.99, 6.66 and 4.73 g/kg on DM basis respectively. Lambs grazing
kikuyu pasture served as the negative control (CON) group. These lambs also
received additional supplementary feed at 500 g/day as a production lick to be
comparable to a scenario where lambs are finished on grazing. Forty cross-bred Merino x Döhne-Merino lambs with an average weaning weight of
24.35 ± 0.648 kg were finished in a feedlot for 57 days where after they were
slaughtered at an average weight of 41.41 ± 1.259 kg. During the feedlot trial lamb
performance was measured by monitoring daily growth rates and feed intake. Also,
an in vivo digestibility study was carried out on the OP and FIN lambs. During the
slaughter process the rumen was removed which was done to collect a sample of
the rumen wall from next to the rumino-reticular fold. These rumen samples were
mounted onto slides so that the development of the rumen could be examined. The M. longissimus dorsi from both sides of the carcass between the 2nd and 3rd last
thoracic vertebra and the 4th and 5th lumbar vertebra were removed.
There was no significant difference (P > 0.05) between any of the concentrate feed
treatments with regards to the average daily gain (ADG), feed conversion ratio (FCR)
or dressing percentage (DP). The CON lambs, as expected, had lower growth rates
(P < 0.05) than the concentrate fed lamb and thus showed significant differences (P
< 0.05) in terms of ADG. The DP of 45.96 % ± 0.711 for the CON lambs differed
significantly (P < 0.05) from the OP (51.44 % ± 0.358), FIN (52.72 % ± 0.653) and LP
(51.74 % ± 0.611) treatments. As expected the concentrate feeds were much more
effective in maintaining higher growth rates when compared to the CON lambs while
the optimizing of EAA in the OP diet did not lead to improved feedlot performance as
the FIN and LP treatments were able to achieve similar (P > 0.05) growth rates.
Within the feedlot treatments there was no significant difference (P > 0.05) with
regard to the papillae length and rumen wall thickness. There was however a
numerical increase in the papillae length as the NSC levels in the feed increased.
The CON lambs differed from the OP lambs (P < 0.05) in terms of papillae length.
This illustrated the importance of having increased levels of NSC in a feedlot diet as
it is this fraction that is responsible for the initialisation and maintenance of rumen
morphological development. The in vivo digestibility study therefore confirmed that the commercial finishing feed
was just as effective as the optimized feed in terms of nitrogen retention as well as in
maintaining suitable energy balance. Although the in vivo digestibility for Met and Lys
in the OP feed was higher (P < 0.05) than the FIN feed, this did not lead to improved
feedlot performance of the OP lambs. The increased digestibility of these amino
acids is due to the fact that the OP diet was higher in levels of bypass amino acids
than the FIN feed. The in vitro true digestibility (IVTD) of the OP feed was higher (P < 0.05) than that of the FIN feed. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om te bepaal of ‘n lamafrond rantsoen wat
gebalanseerd is vir beperkende essiensiële aminosure (EAA) teen ‘n spesifieke vlak
van nie-strukturele koolhidrate (NSK) beter voerkraal prestasie teweeg sou bring
wanneer gemeet word teen ‘n standaard kommersiële afrond rantsoen.
Metionien (Met) en Lisien (Lis) is geïdentifiseer as die eerste beperkende aminosure
vir groeiende lammers. Hierdie twee aminosure, asook Treonien (Tre), Leusien
(Leu), Isoleusien (Ile) en Fenielalanien (Fen) is teen optimale vlakke ingesluit in ‘n
geoptimeerde voerkraal rantsoen, OP. Hierdie rantsoen is geformuleer om 157 g/kg
RP en 477 g/kg NSK te bevat asook Met, Lis, Arg en Tre teen 2.48, 7.45, 8.51 en
8.12 g/kg onderskeidelik. Die tweede behandeling, FIN, was ‘n kommersiële
lamafrond voer waarin die aminosure nie geoptimeer is nie en het soortgelyke vlakke
van proteïene en NSK bevat teen 152 g/kg RP en 468 g/kg NSK met Met, Lis, Arg
en Tre teen 2.08, 5.49, 7.47, 4.80 g/kg onderskeidelik. ‘n Derde voer, LP, het gedien
as ‘n positiewe kontrole en was ‘n lae proteïen voer met laer spesifikasies (139 g/kg
RP, 455 g/kg NSK) waarin die aminosure ook nie geoptimeer is nie. Die LP voer het
Met, Lis, Arg en Tre bevat teen 1.93, 4.99, 6.66 en 4.73 g/kg onderskeidelik. Die
negatiewe kontrole behandeling, CON, is verteenwoordig deur lammers wat op
kikuyu gewei het terwyl addisionele supplementêre voeding teen 500g/lam/dag
voorsien is. Hierdie supplementêre voeding het gedien as ‘n produksie lek om
sodoende vergelykbaar te wees met scenario waar lammers op weiding afgerond word. Veertig kruisgeteelde Merino x Döhne-Merino lammers met ‘n gemiddelde gewig van
24.35 ± 0.648 kg is vir 57 dae in ‘n voerkraal afgerond waarna hulle, teen ‘n
gemiddelde gewig van 41.41 ± 1.259 kg, geslag is. Tydens die voerkraal proef is
prestasie gemonitor deur die meet van daaglikse groei en voerinname. Hiertydens is
daar ook ‘n in vivo verteringsproef op die OP en FIN lammers gedoen. Tydens die
slagproses is die rumen verwyder waarna ‘n monster van die rumenwand langs die
rumino retikulêre vou geneem is. Hierdie rumenmonsters is op skyfies geplaas sodat
die ontwikkeling van die rumen ondersoek kan word. Die M. longissimus dorsi was aan beide kante van die karkas tussen die 2de en 3de laaste torakale werwels en
die 4de en 5de lumbale werwels verwyder.
Daar was geen betekenisvolle verskille (P > 0.05) tussen enige van die konsentraat
behandelings ten opsigte van gemiddelde daaglikse toename (GDT), voeromset
verhouding (VOV) of uitslag persentasie nie. Die CON lammers het egter, soos
verwag, beduidend (P < 0.05) stadiger gegroei en het dus verskille getoon ten
opsigte van GDT. Die uitslag persentasie van 45.96 % ± 0.711 vir die CON lammers
het ook betekenisvol verskil (P < 0.05) van die OP (51.44 % ± 0.358), FIN (52.72 %
± 0.653) en LP (51.74 % ± 0.611) behandelings.
Binne die voerkraal behandelings was daar geen betekenisvolle verskille (P > 0.05)
ten opsigte van die papillae lengte en rumenwand dikte nie, alhoewel daar ‘n
numeriese toename in papillae lengte was soos die NSK vlakke in die voer gestyg
het. Die CON lammers het wel van die OP lammers verskil (P < 0.05) ten opsigte
van papillae lengte. Hierdie bevinding het bevestig hoe belangrik NSK is in die
inisiasie en instandhouding van die morfologiese ontwikkeling van die rumen. Die in vivo verterings studie het daarop gedui dat die kommersiële afrond voer net so
effektief soos die geoptimeerde voer was in terme van stikstof retensie asook die
handhawing van ‘n geskikte energie balans. Alhoewel die in vivo verteerbaarheid
van Met en Lis in die OP hoër was (P < 0.05) as in die FIN voer, het hierdie verskille
nie gelei tot beter groei in die OP lammers nie. Hierdie verskil in verteerbaarheid is
toegeskryf aan die feit dat die aminosure in die OP voer meer rumen-beskermd was
as dié in die FIN voer. Die in vitro verteringstudie het daarop gedui dat die OP voer
beduidend beter (P < 0.05) verteer is as die FIN voer.
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Comparison of production parameters, gut histology, organ weights, and portion yields of broilers supplemented with Ateli plusTeuchert, Nicole 04 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Antibiotic growth promoters (AGP’s) have been used in feed of production animals to improve
their growth performance and disease resistance. However, there has been an increase in the
presence of antibiotic residue in animal products, as well as an increase in untreatable illnesses
due to antibiotic resistant bacteria. This led to the European Union banning the use of antibiotic
growth promoters, in production animals, in 2006. An alternative to AGP’s is therefore needed in
animal feed in order to maintain performance. Plant extracts and essential oils have gained
much attention, due to their natural antimicrobial, antibacterial, anticoccidial and antioxidant
properties. This study tested the efficiency of Ateli plus®, an oregano plant extract based
product, as a replacement to AGP’s on production parameters, carcass characteristics and
organ and gut health of broilers.
This study consisted of five treatments fed to broilers from hatch till 33 days of age, fed in three
phases; starter, grower and finisher. The treatment diets consisted of a negative control (no
AGP), positive control (AGP), Ateli plus® at 1kg/ton (Ateli plus® min), Ateli plus® at 2kg/ton for
week one followed by 1kg/ton for the remainder of the period (Ateli plus® max), and AGP plus
Ateli plus® max (AGP plus Ateli plus® max). Results from this study show that there was no difference in performance parameters between
treatments. The performance parameters tested included liveability, average daily gain (ADG),
average weekly feed intake, average cumulative feed intake, average weekly live weight,
average cumulative weight gains, feed conversion ratio (FCR), cumulative FCR and the
European production efficiency factor (EPEF). Broiler breast and thigh muscle pH and colour
(L*, a* and b*) reading values were measured, showing a trend for improved L* colour reading
value and ultimate pH, in broilers supplemented with Ateli plus®. This leads to an increase in
water binding capacity and tenderness, therefore resulting in an improvement in meat quality.
No differences were shown for dressing percentage and portion percentages relative to carcass
weight. No significant differences were seen for tibia bone Ca and P content, or tibia bone fat,
moisture or ash percentages. However a significant decrease in tibia bone strength was found
in all broilers supplemented with Ateli plus® diets and the negative control diet, compared to
AGP supplemented broilers. Gut morphology showed no consistent effect of treatment on villi
height or crypt depth of the duodenum, jejunum and ileum. No significant differences between
treatments were found for organ pH or organ weights, except the gizzard, which was heavier for
Ateli plus® max supplemented broilers.
Ateli plus® shows promise on improving meat quality characteristics of broilers, however the
significant decrease in tibia bone strength in Ateli plus® supplemented broilers is a major
concern and needs to be researched further. Ateli plus® acts as a good AGP replacement, as
broiler performance for the Ateli plus® supplemented broilers was maintained, and not decreased, when compared to the AGP supplemented broilers. However, the broilers fed the
negative control diet had performance parameters statistically equal to both the Ateli plus® and
AGP supplemented broilers, as well as no significant differences between organ weights were
found. It can therefore be said that the broilers were raised under good management, and their
optimal environmental conditions. Therefore conclusive effectiveness of Ateli plus® as a
replacement for AGP on broiler performance cannot be reported from this study. / AFRIKAANSE OPSOMMING: Antibiotiese groeistimulante (AGP’s) word gereeld as voerbymiddels vir diere gebruik om groei
en siekte weerstandbiedenheid te verbeter. Die verbod op die gebruik van antibiotika as 'n
groeipromotor in die Europese Unie (sedert 2006) kan toegeskryf word aan die toename in
onbehandelbare siektes as gevolg van weerstandbiedende bakterieë, asook die
teenwoordigheid van residue in die dierlike produkte. Alternatiewe vir AGP’s in dierevoeding
word dus benodig om produksie te handhaaf. Plant ekstrakte en essensiële olies het baie
aandag gekry as gevolg van hul natuurlike antimikrobiese, antibakteriële, antikoksidiese en
antioksidatiewe eienskappe.
'n Studie is gedoen om die doeltreffendheid van Ateli plus® ('n origanum plant ekstrak
gebaseerde produk) op groei produksie parameters, karkaseienskappe, orgaan- en
dermgesondheid te bepaal wanneer Ateli plus® as 'n AGP plaasvervanger in die dieëte van
braaikuikens gebruik word. Gedurende die proef was vyf verskillende diëte/behandelings vir 33
dae vir braaikuikens gevoer. Die behandelings het bestaan uit 'n negatiewe kontrole (geen
AGP), positiewe kontrole (AGP), Ateli plus® teen 1kg/ton (Ateli plus min), Ateli plus® teen
2kg/ton vir die eerste week gevolg deur 1kg/ton vir die res van die tydperk (Ateli plus® max), en
AGP plus Ateli plus® max (AGP plus Ateli plus® max). Resultate van hierdie studie toon dat behandelings nie 'n effek op produksie parameters gehad
het nie. Die groei produksie parameters wat getoets is sluit in oorlewing, gemiddelde daaglikse
toename (GDT), die gemiddelde weeklikse voer-inname, gemiddelde kumulatiewe voerinname,
gemiddelde weeklikse lewendige massa, gemiddelde kumulatiewe gewig toename,
voeromsetverhouding (VOV) en die Europese produksie doeltreffendheid faktor (EPEF). Die
pH en kleur (L*,a* en b* waardes) van die dy- en borsspier is gemeet. Ateli plus® aanvulling in
braaikuiken diëte het 'n tendens getoon vir verbeterde L * en finale pH waardes in die spiere,
wat lei tot 'n toename in waterhouvermoë en sagtheid en dus verbeterde vleiskwaliteit. Geen
verskille tussen behandelings is gevind vir uitslagpersentasie en die massa van porsies
(uitgedruk as persentasie relatief tot karkasgewig) nie. Behandelings het nie 'n effek op die vet,
vog, as persentasies of Ca- en P-inhoud van die tibia gehad nie.
In vergelyking met AGP aangevulde braaikuikens, is 'n beduidende afname in die tibia
breeksterkte van kuikens in die negatiwe kontrole groep en kuikens wat met Ateli plus®
aangevul is, gevind. Spysverteringskanaal morfologie het getoon dat behandeling geen
konsekwente effek op villi hoogte of krip diepte van die duodenum, jejunum en ileum gehad het
nie. Slegs die krop massas van kuikens wat met Ateli plus® max aangevul is, was swaarder in
vergelyking met hoenders in die ander behandelings; verder is geen beduidende verskille
tussen behandelings gevind vir orgaan pH of orgaan gewigte nie.
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Copper deficiency-induced hypercholesterolemia: In vivo catabolism of high density lipoprotein cholesteryl ester and protein moities in the rat.Carr, Timothy Perry. January 1989 (has links)
Two studies were conducted to determine how HDL cholesteryl ester and apoprotein catabolism might contribute to the observed hypercholesterolemia of copper-deficient rats. Weanling male Sprague-Dawley rats were divided into two dietary treatments; copper-adequate (control, 5-7 mg Cu/kg diet) and copper-deficient (0.6-0.8 mg Cu/kg diet). Deionized water and diet were provided ad libitum. Dietary copper deficiency resulted in enlarged intravascular pools of HDL cholesteryl esters and total protein. HDL were isolated from rats of both treatment groups, radiolabeled, and injected into animals of the respective groups. In Study I, HDL apoproteins were labeled by iodination, whereas HDL in Study II were doubly labeled by additionally incorporating into the particle core [³H]cholesteryl linoleyl ether, which served as a nondegradable analog of HDL cholesteryl ester. At specific time intervals up to 12 hours after injection, blood and tissue samples were removed and analyzed for radioactivity. Plasma disappearance curves indicated that HDL cholesteryl esters were preferentially catabolized 1.6-fold faster than HDL protein in controls and 2.5-fold faster in copper-deficient animals. Clearance of individual apoproteins did not occur at significantly different rates in either treatment group. Absolute mass removal of HDL cholesteryl ester and total protein from the plasma was significantly increased in copper-deficient rats. Virtually all of the increased removal of HDL cholesteryl ester was attributed to the liver, whereas most of the increased uptake of HDL protein was attributed to the bulk tissues and not the liver. Since previous studies indicate that copper deficiency may not result in increased cholesterol excretion, these data suggest that cholesteryl esters delivered to the liver of copper-deficient rats are possibly reassembled into new HDL particles at an increased rate. The observed hypercholesterolemia in this animal model, then, appears to be the result of an imbalance in the net flux of cholesterol between the tissues and the plasma.
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EFFECTS OF DIETARY FAT AND BODY WEIGHT ON PROTEIN AND ENERGY UTILIZATION IN LAYING HENS.MADRID LOPEZ, ARTURO. January 1982 (has links)
Four experiments were carried out with laying hens to evaluate the effects of body weight, age, dietary protein, and tallow levels on performance, nutrient intake and energy utilization. In the first experiment, Single Comb White Leghorn birds were divided into four body weight groups at the onset of egg production. Voluntary feed intake was 18% less for the lightest (1.39 kg) in comparison with the heaviest group (1.83 kg). Egg weight was directly related to body weight with the heavy birds producing an average egg weighing 65.3 g and the lightest birds having an average egg weight of 58.9 g. Feed conversion was also significantly better for the lighter birds. Maintenance requirements for the heaviest and lightest birds were 60.5 and 57.9% of metabolizable energy consumed, respectively. Metabolizable energy intakes above maintenance were 131 kcal/d for the heavy birds and only 119 kcal for the light group. A composite regression analysis indicated a maintenance requirement of 127.7 kcal/d/kg('0(.)75) and an energetic efficiency of 75.2% for the conversion of metabolizable energy to net energy. In order to evaluate the effects of age and body weight on laying hen performance, the last three experiments were designed using old, molted, and young hens which were divided into the heaviest and lightest body weight groups. The old birds were 72 weeks old, the molted birds were 106 weeks old, and the young birds were 27 weeks old at the start of the studies. In each experiment the birds were fed ten experimental diets with 12, 14, 16, 18, and 20% dietary protein in combination of 1 and 4% supplemental fat. Egg output was increased with the supplementation of tallow in only the young birds; while energy retentions were improved in the old and molted birds with fat feeding. Average energy retentions per kg physiological body weight were 58.8, 41.7, and 38.6 kcal for the young, molted, and old hens, respectively. The light-bodied birds showed 9% better gross energetic efficiencies than the heavy-bodied birds. Estimated daily protein intake requirements were 16.8, 13.3, and 12.8 g/d to support production levels of 84, 64, and 66% for the young, old, and molted birds, respectively.
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EFFECTS OF DIETARY CALCIUM LEVELS ON ENERGY AND MINERAL UTILIZATION.Zaft, Marjorie Helen. January 1982 (has links)
No description available.
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EVALUATION OF JOJOBA MEAL AS A PROTEIN SOURCE FOR RUMINANTSGarcia-Puebla, Manuel Rogelio January 1982 (has links)
No description available.
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