Effects of energy sources on milk production and reproduction of dairy cows

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Stellenbosch : Stellenbosch University
ENGLISH ABSTRACT: Two main objectives were investigated in this study, conducted at the Elsenburg Research Farm of the Western Cape Department of Agriculture (WCDA). The first objective was to study the effect of nutritional treatments differing after calving in energy levels and sources on plasma metabolites and live weight (LW) changes, milk production and milk composition, ovarian follicular dynamics and oestrous activity, as well as fertility traits of dairy cows. The second objective was to investigate the effects of two late prepartum diets differing in non-fibre carbohydrates (NFC) and protein levels on milk production and milk composition, LW changes and fertility traits of dairy cows in the subsequent lactation. Three trials were conducted in this study. The first trial explored the effect of energy-dense ingredients like fat or starch on milk production and milk composition, plasma metabolites, LW change and fertility of lactating dairy cows. In this study, pregnant Holstein heifers and dry cows were similarly managed and fed prepartum. Following calving, they were allowed to graze ad libitum on kikuyu-ryegrass pasture, and received supplements that differed in terms of inclusion levels and types of concentrates. Holstein cows in the control group received 7 kg/day of a control concentrate supplement for both primiparous and multiparous groups, while treatments consisted of 11.6 and 12.6 kg/day for primiparous and multiparous cows, respectively. Supplements in treatments contained high starch-low fat (HSLF) and high starch-low fat/low starch-high fat (HSLF-LSHF) levels. The control and HSLF concentrates were offered from calving to 154 days in milk (DIM). The HSLF supplement was a glucogenic concentrate containing maize as the energy source. The HSLF-LSHF supplements were combinations of a glucogenic concentrate offered for the first 60 DIM as per treatment HSLF and followed from 61 to 154 DIM by a lipogenic concentrate containing wheat bran and calcium (Ca)-salts of long-chain fatty acids as the energy sources. The postpartum diets were formulated to be isonitrogenous. The control diet contained low energy level (2.47 Mcal ME/kg DM) and provided 457, 104 and 40 g/kg of NDF, starch and fat on DM basis, respectively. The HSLF diet contained high energy level (2.71 Mcal ME/kg DM) and offered 341, 242 and 35 g/kg of NDF, starch and fat on DM basis, respectively. The HSLF treatment was formulated to increase plasma insulin and glucose levels in order to reduce the magnitude of the NEB and encourage the early return of oestrous cyclicity after calving. In the HSLF-LSHF combination treatment, the high starch-based diet initially aimed to achieve the same objective of the HSLF treatment during the first 60 DIM. The LSHF diet contained high energy level (2.70 Mcal ME/kg DM) and provided 388, 137 and 58 g/kg of NDF, starch and fat on DM basis, respectively. Secondly, the LSHF diet was fed from 61 DIM to decrease plasma insulin and improve plasma cholesterol in order to increase the size of the ovulatory follicle as well as promote embryo development. The second experiment trial was simultaneously conducted with the first trial using the same feeding treatments. In this trial, the same objectives of the diets were evaluated for ovarian follicular dynamics and oestrous activity of multiparous cows after being synchronized by means of the Ovsynch protocol at 80 ± 10 DIM without artificial insemination (AI). Results on plasma metabolites showed that postpartum levels of non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB) did not differ between nutritional treatments for multiparous cows, but levels increased (P < 0.05) for the control in comparison to HSLF and HSLF-LSHF treatments for primiparous animals. In addition, plasma urea levels were higher (P < 0.05) in both primiparous and multiparous animals receiving HSLF and HSLF-LSHF concentrates, compared to the control concentrate. The postpartum LW was the lowest (P < 0.05) and LW loss was greater (P < 0.05) in cows in the control in comparison to HSLF and HSLF-LSHF treatments in both primiparous and multiparous cows. Findings on productive responses showed that the milk yields and 4 % fat corrected milk (FCM) yields of both primiparous and multiparous cows in HSLF and HSLF-HFLS treatments were higher (P < 0.05), compared to cows in the control. In the primiparous group, the HSLF diet enhanced (P < 0.05) milk protein content whereas HSLF and HSLF-HFLS diets resulted in increased milk lactose content (P < 0.05). In multiparous group, HSLF treatment increased (P < 0.05) milk lactose content. Results of ovarian follicular dynamics and oestrous activity showed that dimensions of the ovaries and the preovulatory follicle as well as numbers of follicles within different classes in dairy cows were similar between nutritional treatments. However grazing cows receiving high (12.6 kg/day) levels of concentrates in the HSLF and HSLF-LSHF treatments recorded a higher number of total follicles (P < 0.05), compared to those on the low (7 kg/day) level of concentrate in the control group. Results of reproductive performance showed no nutritional effects in both primiparous and multiparous cows on the interval calving to first service, the percentage of cows serviced for the first time within the 80 DIM, pregnancy rate at first service, number of services per conception, interval days open and the pregnancy rate at 100 DIM. However, the conception rate at 150 DIM in both primiparous and multiparous groups improved (P < 0.05) in cows fed HSLF and HSLF-LSHF concentrates, in comparison to the control. The third trial was conducted to evaluate the effect of two late prepartum nutritional treatments on subsequent LW changes, milk production and milk composition, and fertility traits of Holstein dairy cows. Pregnant heifers and dry cows received a similar level and type of prepartum concentrate associated either unchopped oat hay ad libitum (control) or ad libitum intake of a partial total mixed ration (pTMR, treatment). The pTMR consisted of oat hay (48%), lucerne hay (43%) and soybean oil cake meal (9%). The prepartum treatment was designed to optimise rumen digestion and fermentation through improved prepartum intake of NFC and protein per kg on DM basis with an objective of reducing the extent of a periparturient negative energy balance (NEB) in comparison to the control. Following parturition, primiparous and multiparous cows received 7 kg/day of concentrate while grazing ad libitum on kikuyu-ryegrass pastures from calving to 120 DIM. Results showed that prepartum LW was similar for both primiparous and multiparous groups. In the primiparous group, the prepartum treatment significantly improved (P < 0.05) postpartum LW, with 20 kg more weight at LW nadir, compared to the control. However, no prepartum nutritional effects were detected on postpartum LW traits and LW loss for multiparous cows. Milk yields and milk composition were similar between the control and treatment for both primiparous and multiparous groups. Primiparous cows in the control group had a longer interval from calving to first service (P < 0.05), compared to those in treatment group. However, this improvement did not turn into increased conception rates of primiparous cows at 120 DIM. Similarly, prepartum diet effects in multiparous cows showed no postpartum differences in conception rates at 120 DIM. It can concluded that there is definite merit in the use of energy levels and sources for improving production responses, plasma metabolite profiles and LW change, ovarian follicular dynamics and fertility of grazing dairy cows. These improvements are related to nutrient composition and levels of total energy intake, controlling the profile of nutrients absorbed in the gastrointestinal tract (GIT) and their hepatic partitioning to various body tissues for metabolic requirements of dairy cows. This modulation has probably influenced the hypothalamic-pituitary-ovarian-uterine axis through improved nutritional status and optimized the energy carry-over effect into fertility success, while sustaining milk production. However, feeding fibre-based diets differing in NFC and protein levels in the late prepartum period showed no benefit in either milk production or conception rates of dairy cows in the subsequent lactation. The lack of significant differences of prepartum dietary effects on milk production and conception success can be related to the prepartum feeding period and the relatively low number of animals per treatment used in the study. Further investigations should be undertaken using different inclusion and types of energy sources in prepartum and postpartum dairy cows on metabolic and hormonal responses that can improve restoration body reserves and benefit chronological sequences of the reproductive process such as postpartum health, uterine regression, resumption of oestrous cycles, conception, and embryo/pregnancy survival until the next calving.
AFRIKAANSEOPSOMMING: Hierdie studie is uitgevoer op die Elsenburg Navorsingsplaas van die Wes-Kaapse Departement van Landbou (WKDL) en het twee hoofdoelwitte gehad. Die eerste doelwit was om die effek te bepaal van verskilllende voedingspeile, naamlik twee energiepeile en twee energiebronne, op spesifieke bloedplasma metaboliete, die verandering in liggaamsmassa, melkproduksie en -samestelling, ovarium en follikulêre aktiwiteite asook vrugbaarheidseienskappe van lakterende Holsteinkoeie wat die diete vanaf na kalwing ontvang het. Die tweede doelwit was om die effek te bepaal van twee diete, verskillend ten opsigte van nie-vesel koolhidraat- (NVK) en proteïenpeile, wat tydens die laat-dragtige periode aan melkkoeie gevoer is op die melkproduksie en -samestelling, verandering in liggaamsmassa en vrugbaarheidseienskappe van melkkoeie in die daaropvolgende laktasie. Vir die eerste doelwit is drie studies uitgevoer. In die eerste studie is die effek van energieryke grondstowwe soos vet of stysel op die melkproduksie en -samestelling, plasma metaboliete, liggaamsmassaverandering en die vrugbaarheid van lakterende melkkoeie bepaal. In hierdie studie is dragtige Holsteinverse en droë koeie voor kalwing op dieselfde manier bestuur en gevoer. Na kalwing het koeie ad libitum toegang gehad tot aangeplante kikoejoe-raaigrasweiding met kragvoeraanvullings wat verskil het ten opsigte van insluitingspeil en die tipe energiebron. Die kontrole-dieet het bestaan uit ‘n lae kragvoerpeil (7 kg/koei/dag) van ‘n standaard aanvulling terwyl behandelings bestaan het uit aanvullings wat (1) hoë stysel en lae vetpeile (HSLV) en (2) hoë stysel en lae vetpeile gevolg deur lae stysel en hoë vetpeile (HSLV-LSHV) bevat het. Dié aanvullings is teen hoër peile (11.6 en 12.4 kg/koei/dag vir eerste- en tweede-pluslaktasiekoeie, onerskeidelik) as die standaard kragvoer aanvulling voorsien. Die HSLV-aanvulling het bestaan uit ‘n konsentraat wat glukose bevat met mielies as energiebron en is vanaf kalwing tot 154 dae na kalf aan koeie voorsien. Die aanvullings wat in die behandeling HSLV-LSHV gebruik is, het bestaan uit kombinasies van ‘n glukose-bevattende energiebron vir die eerste 60 dae van die laktasieperiode, soortgelyk aan die behandeling HSLV, gevolg deur ‘n kragvoer (LSHV) wat vet bevat het as energiebron (koringsemels en kalsiumsoute met langkettingvetsure) wat vanaf 61 tot 154 dae na kalf aan koeie gevoer is. Die tweede proef is gesamentlik met die eerste proef gedoen met dieselfde diete. Koeie wat op 80 ± 10 dae na kalf nog nie kunsmatig geïnsemineer was nie, is gesinchroniseer volgens die Ovsynch program en die follikulêre veranderinge en hitte-aktiwiteit van koeie is bepaal. Die energie-balansstudie het aangetoon dat geen verskille voorgekom het ten opsigte van die nie-esterbevattende vetsure (NEVS), plasma ureumpeile en liggaamsmassaveranderinge vir beide eerste- en tweedeplus-laktasiekoeie nie. Die NEVS en β-hidroksiebutiraat (BHB) peile na-kalwing is ook nie beïnvloed vir die tweede-pluslaktasiekoeie nie terwyl die peile hoër (P < 0.05) was by eerstelaktasiekoeie wat die kontrole diet ontvang het in vergelyking met koeie wat die HSLV en HSLV-LSHV aanvullings ontvang het. Ureumpeile in bloedplasma in beide die eerste- en tweedeplus-laktasiekoeie is eweneens beïnvloed (P < 0.05) deur diëte met laer peile wat die kontrole dieet in vergelyking wat die HSLV en HSLV-LSHV aanvullings ontvang het. Aanvullend hierby het beide die eerste- en tweedeplus-laktasiekoeie wat die kontrole aanvulling ontvang het ‘n groter afname in liggaamsmassa ondervind in vergelyking met koeie wat die HSLV en HSLV-LSHV aanvullings ontvang het. Die produksiestudie het getoon dat die melkproduksie van koeie verhoog (P < 0.05) en dat sommige bestanddele in melk ook verander (P < 0.05) is deur die behandelings wat toegepas is. Die melkproduksie van beide eerstelaktasie- en ouer (tweede-pluslaktasie) koeie wat die HSLV en HSLV-LSHV behandelings ontvang het, was hoër as die melkproduksie van koeie wat die kontrole dieet ontvang het. Eerstelaktasiekoeie wat die HSLV aanvulling ontvang het, het melk met ‘n hoër (P < 0.05) proteienpersentasie geproduseer terwyl die melk van dié koeie wat die HSLV-LSHV aanvulling ontvang het, ‘n hoër (P < 0.05) laktosepersentasie bevat het. Netso het die melk van tweede-pluslaktasiekoeie wat die HSLV aanvulling ontvang het, hoër laktose peile bevat. Die follikulêre aktiwiteite in die ovaria en geslagsaktiwiteit is nie beïnvloed deur die vlak van energie-inname nie terwyl die totale aantal follikels wel beïnvloed (P < 0.05) is. Die reproduksieprestasie van beide eerste- en tweede-pluslaktasiekoeie vir die volgende reproduksie-eienskappe, naamlik periode vanaf kalf tot eerste inseminasie, die proporsie van koeie gedek voor 80 dae-in-melk, die persentasie besetting met eerste inseminasie, aantal dekkings per konsepsie, die aantal dae oop en die proporsie koeie wat beset was by 100 dae-in-melk, is nie beïnvloed deur kragvoeraanvullings nie. Die proporsie koeie wat beset was by 150 dae-in-melk is wel beïnvloed (P < 0.05) deur kragvoeraanvulling met meer eerstelaktasie- en tweedeplus-laktasie koeie beset wat die HSLV en HSLV-LSHV aanvullings ontvang het in vergelyking met die kontrole-aanvulling. Die derde studie is uitgevoer om die invloed van die energiepeil in die dieet voor kalwing ten opsigte van liggaamsmassaverandering, melkproduksie en vrugbaarheidseienskappe gedurende die daaropvolgende laktasieperiode te bepaal. Dragtige verse en droë koeie is voor kalwing dieselfde tipe en hoeveelheid kragvoer voorsien tesame met (1) ad libitum gevoerde lang, ongekerfde hawerhooi en (2) ‘n ad libitum inname van ‘n gedeeltelike totaal gemengde rantsoen (pTMR) wat uit 48% hawerhooi, 43% lusernhooi en 9% sojaboon-oliekoekmeel bestaan het. Na kalwing is die eerstelaktasie- en tweedeplus-laktasiekoeie op aangeplante kikoejoe-raaigrasweiding aangehou en het hulle dieselfde kragvoeraanvulling ontvang. Volgens die proefresultate het die voorkalwingsliggaamsmassa van beide eerstelaktasie- en tweedeplus-laktasiekoeie in die verskillende behandelingsgroepe nie verskil nie. Hierteenoor het die na-kalwingsliggaamsmassa van eerstelaktasiekoeie wat die kontrole-dieet (hawerhooi) en pTMR-voorkalwingsdieet ontvang het, verskil terwyl geen effek waargeneem is by die tweedeplus-laktasiekoeie nie. Die melkproduksie en –samestelling was dieselfde vir beide eerstelaktasie- en tweedeplus-laktasiekoeie wat die kontrole en behandelingsdiëte voorkalwing ontvang het. Eerstelaktasiekoeie wat net hawerhooi gedurende die voorkalwingsperiode ontvang het, het ‘n langer (P < 0.05) periode van kalf tot eerste inseminasie gehad in vergelyking met koeie wat die pTMR-dieet ontvang het. Geen verskille is gevind vir tweedeplus-laktasiekoeie nie. Net so is geen verskille tussen die kontrole en proefdiete gevind by beide eerstelaktasie- en tweedeplus-laktasiekoeie vir die persentasie koeie wat vir die eerste keer gedek is binne 80 dae na kalf, dragtigheid na eerste inseminasie, koeiliggaamsmassa met eerste dekking en besettingspersentasie teen 120 dae-in-melk. Resultate toon dat daar beslis meriete bestaan om spesifieke energiebronne te gebruik om die volgende eienskappe te verbeter, naamlik melkproduksie, status van die enegiebalans en verandering in die liggaamsmassa van koeie asook follikulêre aktiwiteite, wys van hitte en die vrugbaarheid van koeie. Hierdie verbeteringe hou verband met voedingstofsamestelling en totale energie-innamevlakke, wat die profiel van voedingstowwe wat in die spysverteringskanaal (SVK) geabsorbeer word, sowel as die allokasie daarvan in die lewer na die onderskeie liggaamsweefsels vir die metaboliese behoeftes van melkkoeie, beheer. Die verandering in voedingstowwe het waarskynlik die hypothalamus-pituitêre-ovarium verbintenis beïnvloed tot ‘n beter energie balans met ‘n verdere oordragingseffek op die vrugbaarheid van koeie terwyl melkproduksiepeile gehandhaaf word. Tersefdertyd het ‘n verandering in die dieet wat dragtige verse en droëkoeie voorkalwing ontvang het geen voordele ingehou vir koeie in die daaropvolgende laktasieperiode ten opsigte van melkproduksie, -samestelling of besettingspersentasies nie. Dit kan waarskynlik toegeskryf word aan die beperkte aantal koeie wat in die proef in elke behandeling gebruik is. In hierdie studie het die behandelings nie-betekenisvolle produksie- en reproduksieresponse op alle gebiede getoon nie. Dit word aanbeveel dat die studie opgevolg behoort te word met groter getalle diere.
Thesis (PhD)--Stellenbosch University, 2017.
Dairy cattle -- feeding and feeds, Dairy cows -- Milk production, Dairy cows -- Reproduction, UCTD