Partial substitution of maize with soybean hulls in a concentrate supplement for grazing dairy cows

Van der Vyver, Anesme (2019-04)

Thesis (MScAgric)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Climate in the southern Cape region of South Africa permits dairy farmers to make use of cultivated pasture as their main nutrient and feed source for dairy cows. A commonly used pasture system in this region is kikuyu over-sown with ryegrass. Pasture has a limited supply of nutrients which necessitates the need to provide dietary supplementation in a concentrated form. Concentrates consists primarily of maize grain which is a highly priced product containing a high starch content. Including alternative feed ingredients with lower starch content, higher level of digestible fibre and possibly a lower cost in concentrates may improve milk production and milk composition. Soybean hulls are one of many by-products which are considered as an alternative to maize. The hulls are a by-product after processing of soybeans for oil and meal, and are high in energy, crude protein (CP) and fibre which make it a possible alternative to maize in dairy feed as it is digested more efficiently by ruminants. The aim of this study was to determine the effect of partial substitution of a maize in a dairy concentrate with soybean hulls, on milk production, milk composition, digestion of kikuyu-ryegrass pasture and rumen environment. Fifty-one lactating Jersey cows from Outeniqua Research Farm were blocked according to mean milk yield, days in milk (DIM) and lactation number for the production study. Cows used were between 127 ± 50.5 DIM. A complete randomised block design was used. Cows within each block were randomly allocated to one of the three treatments. Treatments were defined according to the level of soybean hulls included in the concentrate supplement: SH0, SH15 or SH30 containing respectively 0%, 15% or 30% soybean hulls. Cows were fed 6 kg/day (3 kg per milking session) concentrates. After each milking session the cows grazed fresh kikuyu-ryegrass pasture allocated at ± 13 kg dry matter (DM)/cow per day. There were no significant differences (P > 0.05) in milk yield, 4% fat corrected milk (FCM) and energy corrected milk (ECM) between treatments. Milk fat tended (P = 0.06) to increase when 15% soybean hulls were included. Milk protein and lactose percentages increased significantly (P < 0.05) when soybean hulls were included (15 and 30%) in the concentrates. Somatic cell count (SCC) did not differ significantly between treatments. The milk urea nitrogen (MUN) content (8.30 – 9.36 mg/dL) indicated that sufficient protein was supplied to cows on all treatments. Cows on all three treatments gained weight and improved in condition during the study. Live weight of cows did not differ between treatments. Body condition improved (P < 0.05) when 15% soybean hulls were included indicating sufficient energy supply. Nine ruminally cannulated cows from the Outeniqua Research Farm were used for the rumen study. A 3 x 3 Latin square design was used, where all cows were subjected to all three treatments. In each period, cows were randomly allocated to one of the three treatments. Cows were fed 6 kg/day (3 kg per milking session) concentrates. After each milking session the cows grazed together with the production study cows on fresh kikuyu-ryegrass pasture allocated at ± 13 kg DM/cow per day. There were no significant differences in the rumen pH among treatments. Acetate production showed no significant difference among treatments. Rumen propionate and butyrate concentration was lower (P ≤ 0.05) when 30% soybean hulls were included compared to the control. The ratio of acetate to propionate increased (P < 0.05) when soybean hulls were included at 15 and 30%. Rumen ammonia nitrogen (NH3-N) increased (P < 0.05) when 30% soybean hulls were included. After 30 h of incubation the in sacco DM disappearance of ryegrass pasture was higher (P = 0.05) when soybean hulls were included. The in sacco neutral detergent fibre (NDF) disappearance of kikuyu-ryegrass pasture after 30 h of incubation increased significantly when 15% soybean hulls were included, compared to 0% soybean hulls. The study showed that milk production can be maintained when as much as 30% soybean hulls replaced maize in the concentrate. Replacing 15% of the maize tended to increase milk fat content and increased milk protein and lactose content significantly.

AFRIKAANSE OPSOMMING: Klimaat in die suidelike Kaapstreek van Suid-Afrika laat suiwelboere toe om van aangeplante weiding as hul hoofvoedingstof en voerbron vir melkkoeie gebruik te maak. 'n Algemeen gebruikte weidingstelsel in hierdie streek is kikoejoe oor-gesaai met raaigras. Weiding het 'n beperkte hoeveelheid voedingstowwe wat dit nodig maak om dieetaanvulling in 'n gekonsentreerde vorm te verskaf. Konsentrate bestaan hoofsaaklik uit mieliegraan wat 'n hoogs geprysde produk is wat 'n hoë styselinhoud bevat. Insluiting van alternatiewe voer bestanddele met laer styselinhoud, hoër vlak van verteerbare vesel en moontlike laer koste in konsentrate kan melkproduksie en melksamestelling verbeter. Sojaboondoppe is een van die vele neweprodukte wat as 'n alternatief vir mielies beskou word. Die doppe is 'n neweproduk na die verwerking van sojabone vir olie en meel, en is hoog in energie, ru-proteïen (RP) en vesel wat dit 'n moontlike alternatief vir mielies in suiwelvoedsel maak, aangesien dit meer doeltreffend deur herkouers verteer word. Die doel van hierdie studie was om die effek van gedeeltelike vervanging van ‘n mielie-gebaseerde suiwelkonsentraat met sojaboondoppe op, melkproduksie, melksamestelling, vertering van kikoejoe-raaigras weiding en rumenomgewing te bepaal. Een-en-vyftig lakterende Jersey-koeie van Outeniqua Navorsingsplaas was geblokkeer volgens gemiddelde melkopbrengs, dae in melk (DIM) en laktasienommer vir die produksiestudie. Koeie gebruik was tussen 127 ± 50.5 DIM. 'n Volledige ewekansige blokontwerp was gebruik. Koeie binne elke blok was ewekansig toegeken aan een van die drie behandelings. Behandelings was gedefinieer volgens die vlak van sojaboondoppe wat ingesluit was in die konsentraat aanvulling: SH0, SH15 of SH30 wat onderskeidelik 0%, 15% of 30% sojaboondoppe bevat. Koeie was 6 kg/dag (3 kg per melk sessie) konsentraat gevoer. Na elke melksessie het die koeie vars kikoejoe-raaigras weiding gewei wat teen ± 13 kg droëmateriaal (DM)/koei per dag toegedien was. Daar was geen beduidende verskille (P > 0.05) in melkopbrengs, 4% vet gekorrigeerde melk (FCM) en energie gekorrigeerde melk (ECM) tussen behandelings nie. Bottervet het ‘n neiging getoon (P = 0.06) om toe te neem wanneer 15% sojaboondoppe ingesluit was. Melkproteïen en laktose persentasies het aansienlik toegeneem (P < 0.05) wanneer sojaboondoppe (15 en 30%) in die konsentrate ingesluit was. Somatiese seltelling (SCC) het nie beduidend verskil tussen behandelings nie. Die melkureumstikstof (MUN) inhoud (8.30 – 9.36 mg/dL) dui aan dat voldoende proteïen aan koeie op al die behandelings voorsien was. Koeie op al drie behandelings het gewig opgetel en in kondisie verbeter tydens die studie. Lewendige gewig van koeie verskil nie tussen behandelings nie. Liggaams-kondisie het verbeter (P < 0.05) wanneer 15% sojaboondoppe ingesluit was, wat voldoende energievoorsiening aandui. Nege rumen-gekannuleerde koeie van die Outeniqua Navorsingsplaas was vir die rumenstudie gebruik. 'n 3 x 3 Latynse vierkante ontwerp was gebruik, waar alle koeie aan al drie behandelings onderhewig was. In elke periode was koeie lukraak toegeken aan een van die drie behandelings. Koeie was 6 kg/dag (3 kg per melk sessie) konsentraat gevoer. Na elke melksessie het die koeie saam met die produksiestudie koeie vars kikoejoe-raaigras weiding gewei wat teen ± 13 kg DM/koei per dag toegedien was. Daar was geen beduidende verskille in die rumen pH tussen behandelings nie. Asetaat produksie het geen beduidende verskil tussen behandelings getoon nie. Rumen propionaat en butyraat konsentrasie was laer (P ≤ 0.05) toe 30% sojaboondoppe ingesluit was in vergelyking met die kontrole. Die verhouding van asetaat tot propionaat het toegeneem (P < 0.05) toe sojaboondoppe teen 15 en 30% ingesluit was. Rumen-ammoniakstikstof (NH3-N) het beduidend toegeneem (P < 0.05) toe 30% sojaboondoppe ingesluit was. Na 30 uur van inkubasie was die in sacco DM verdwyning van kikoejoe-raaigras weiding hoër (P = 0.05) toe sojaboondoppe ingesluit was. Die in sacco neutraalbestande vesel (NDF) verdwyning van kikoejoe-raaigras weiding na 30 uur van inkubasie het beduidend toegeneem toe 15% sojaboondoppe ingesluit was in vergelyking met 0% sojaboondoppe. Die studie het getoon dat melkproduksie gehandhaaf kan word wanneer soveel as 30% sojaboondoppe die mielies in die konsentraat vervang. Die vervanging van 15% van die mielies het geneig om bottervetinhoud te verhoog en die melkproteïen en laktose-inhoud beduidend te verhoog.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105923
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