Item – Thèses Canada

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Numéro d'OCLC
1013747120
Lien(s) vers le texte intégral
Exemplaire de BAC
Auteur
Higginson, Valerie,
Titre
Effects of yeast-derived microbial protein and live yeast on the lactational performance and metabolism of transition Holstein cows
Diplôme
M. Sc. -- McGill University, 2017
Éditeur
[Montreal] : McGill University Libraries, [2017]
Description
1 online resource
Notes
Thesis supervisor: Arif Mustafa (Internal/Supervisor).
Thesis supervisor: Bushansingh Baurhoo (Internal/Cosupervisor2).
Includes bibliographical references.
Résumé
"The current study evaluated the effects of a yeast-derived microbial protein (YMP) and live yeast on the health and lactational performance of Holstein cows during their transition period. Experiment 1 examined the effects of supplementing YMP alone, whereas Experiment 2 examined YMP fed in combination with live yeast (Saccharomyces cerevisiae). Both studies commenced 21 days prior to expected calving and ended 28 days postpartum. Cows were blocked according to parity and expected calving dates. Both studies evaluated the effects of treatments on milk production and composition, dry matter intake (DMI), body condition score (BCS) and serum biochemical parameters, macrominerals and proteins. In Experiment 1, twenty-seven primiparous and multiparous Holstein cows were randomly assigned to either a treated (YMP; 50 g YMP prepartum followed by 200 g YMP postpartum) or control (0 g YMP). In Experiment 2, cows were randomly assigned to either a YMPL (100g YMP and 10g live yeast prepartum followed by 200g YMP and 10g live yeast postpartum) or control (0 g YMP or live yeast) group. In both studies, DMI and milk yield were recorded daily in the postpartum period. Milk samples were obtained twice weekly while BCS evaluation and blood collections were performed on d -21, -14, -7, -3 and -1 relative to expected calving dates and d 1, 3, 7, 14, 21 and 28 postpartum. In Experiment 1, there was no effect of YMP on DMI, BCS milk yield or milk composition. However, YMP supplementation significantly reduced serum non-esterified fatty acids (NEFA) concentration from d 3 postpartum until the end of the study. Serum concentrations of [beta]-hydroxybutyrate (BHBA) were also reduced in YMP-supplemented cows on d 3 and 7 postpartum. Moreover, YMP supplementation significantly increased serum glucose levels on d 3 and 7 postpartum, and reduced serum aspartate transaminase (AST) levels on d 14 and 21 postpartum. In Experiment 2, YMP and live yeast supplementation did not affect DMI, BCS or milk performance. Serum concentration of BHBA was not affected by YMPL supplementation. However, YMPL cows had higher serum NEFA concentrations on d 3 and 14 postpartum whereas serum AST concentrations were higher on d 1, 3 and 7 postpartum. This was accompanied by higher serum glutamate dehydrogenase (GLDH) and lower haptoglobin levels in YMPL cows on d 7 and 14 postpartum. From Experiment 1, it was concluded that YMP supplementation to transition cows may significantly reduce metabolic stress leading to less adipose tissue mobilization and improved hepatic health without any negative impacts on milk performance. In Experiment 2, however, YMPL supplementation appeared to increase metabolic stress in transition cows as indicated by higher serum NEFA levels postpartum. However, serum NEFA levels decreased rapidly in YMPL cows as lactation progressed, suggesting that fat mobilization was not excessive. These conflicting results suggests that the mode of YMP supplementation (pellet or powder) may have a direct effect on its efficacy and that feeding YMP in combination with live yeast during the transition period merits further investigation."--
Autre lien(s)
digitool.Library.McGill.CA
escholarship.mcgill.ca
escholarship.mcgill.ca
Sujet
Animal Science