Response of ruminant health and growth to the probiotic Bacillus amyloliquefaciens

Abstract

Probiotics are widely used to restore and maintain normal digestive flora to reduce metabolic disorders and improve health and productivity, especially in simple-stomached animals but less so in ruminants. Bacillus amyloliquefaciens strain H57 (H57) is a novel probiotic that has previously been shown in a pilot study to reduce the risk of hay spoilage and, over a relatively short term of a few weeks, improved dry matter intake (DMI) and the efficiency of nitrogen utilization in pregnant ewes fed the treated hay. The aim of the current study was to evaluate H57 over much longer periods of time than the pilot study, to confirm health and performance responses such as daily weight gain (DWG) at key stress periods in a ruminant's life. The effect of H57 on rumen fermentation, digestibility and concentration of metabolic hormones were also investigated to better understand the actions of H57 in ruminants.The first experiment (Chapter 2) investigated the effect of H57 during the transition from pregnancy to lactation when ruminants undergo a rapid change in metabolic demand.Twenty-four pregnant ewes were individually fed pellets, based on palm kernel meal, to meet their requirements for pregnancy and to gain 70g/d. They were then fed an ad libitum mixture of lucerne and oaten hay during lactation. The H57 improved DMI and DWG in late pregnancy and consequent lamb growth in early lactation. During late pregnancy, the ewes fed H57 ate 16.6% more pellets, retained 45% more nitrogen between 39 and 26 days prior to parturition, and were 17% heavier by parturition. H57 inoculated pellets did not change the digestibility of dietary energy or protein but did modify rumen fermentation toward an increase in the concentration of butyrate and valerate.In the second experiment (Chapter 3), the effect of H57 was investigated around the weaning process, another commonly stressful period in ruminant life. Twenty-four male or female calves were allocated into two groups, and between 4 and 12 weeks of age were individually offered 6 L/d of whole milk and ad libitum starter pellets impregnated with or without H57. Similar to the first experiment, calves fed H57 grew faster, tended to consume more pellets and were 14% more feed efficient compared to the Control calves. The duration of diarrhoea was 2 days less in the H57-fed calves compared to the Control calves. The H57-fed calves also weaned 9 days earlier and were 15.8% heavier at week 19. H57 also showed potential to stimulate rumen development by increasing plasma betahydroxybutyrate, which is an indicator of rumen development in young ruminants, and appeared to improve immunity by increasing the concentration of plasma globulin.iii Given the success of H57 in reducing the weaning age and incidence of diarrhoea in the dairy calves in the second experiment, it was considered there could be additional benefits if the H57 is added at the primary colonization time of the GIT microbiome, that is, as close to parturition as possible. Therefore in the third experiment (Chapter 4), ...