| Disease is the main reason for the use of antimicrobials in calf rearing,and antibiotics are commonly used to treat calves,including for unknown diseases.This leads to antimicrobial resistance,which is a challenge to the livestock industry and public health.Despite efforts at improvement,calf diarrhea remains one of the main problems in calf rearing.Plant products containing high levels of phytochemicals may improve the immunity and resistance of calves against infections,thereby reducing the use of antimicrobials.Amla(Phyllanthus emblica)fruit could be a good candidate to improve gut health due to its antimicrobial,gastro-protective,and immunomodulatory effects.Phenolic acids,flavonoids,lipids,amino acids and tannins are the major components,while Digallic acid,Ellagic acid,Kaempferol-4’-O-glucoside,Emblicanin A,and Gallic acid are among the active compounds identified in the fruit.This study aimed to evaluate the effect of amla fruit powder supplementation on frequency of diarrhea,growth performance,antioxidant capacity,immune response,rumen fermentation and rumen bacterial structure of preweaning of dairy calves.One hundred male Holstein calves [2-days(d)-old;42.6 ± 1.7 kg body weight(BW)] were randomly assigned into five treatments,CON,PE5,PE10,PE20,and PE40,with 0,5,10,20,and 40 g/d amla fruit powder(PE)supplementation,respectively,and housed in individual hutches(n = 20 calves per treatment).The experiment lasted from 2 to 75 d of age(weaning)and calves were fed milk(2–7 d),milk replacer(8–75 d),and calf starter(2–75 d).The PE supplementations were fed in two meals a day,equal amount each time,by mixing into milk or milk replacer.Feed intake and fecal score data were collected daily;BW and body frame measurements at 2,14,28,42,and 75 d;and rumen fluid samples at 14,28,42,and 75 d;fecal samples at 2,28,42,and 75 d;blood samples at 28 and 75 d.Feed and rumen fluid samples were analyzed for chemical composition and rumen fermentation characteristics,respectively.Antioxidant and immune indices and pro-and anti-inflammatory cytokines were analyzed from serum samples,whereas 16 S r RNA was analyzed from rumen fluid and fecal samples.Starter and total dry matter intakes(DMI)differed among treatments during 22–75 with the highest in CON and linearly decreased with increasing PE doses.Liquid feed DMI tended to decrease with increasing PE doses.PE supplementation had quadratic effect on body weight(BW),average daily gain(ADG),feed efficiency,body length,heart girth,and withers height.The BW and ADG differed among treatments during 29–75 and 15–75 d,respectively,with the highest in PE5 followed by CON and lowest in PE40.However,PE did not improve BW and ADG compared to the CON.The overall feed efficiency in PE5 was higher than in PE20 and PE40.PE5 decreased the frequency of fecal score “3”(P = 0.02)while PE5(P < 0.01)and PE10(P = 0.03)increased the frequency of fecal score “1”,compared to the CON.Frequency of diarrhea in the PE5 group(7.9%)was lower(P < 0.05)than all groups(11.1%,14.3%,22.6%,and 24.2% for PE10,PE20,and PE40,respectively).Rumen fermentation(p H,ammonia-N,and volatile fatty acids)was not affected by PE supplementation.However,ammonia-N showed a decreasing trend with increasing PE levels.PE supplementation,at 5 g/d,protected calves against oxidative stress and improved antioxidant enzymes and immune and anti-inflammatory responses,showing its immunity-enhancing and protective roles against infections.However,the antioxidant capacity and immune response decreased with increasing PE levels,illustrating the adverse effects of PE supplementation at higher doses.The analysis of ruminal and fecal bacterial community abundance detected higher proportions of Firmicutes at an early age,and a higher Bacteroidetes to Firmicutes ratio at weaning,in calves supplemented with 5 g/d PE.This contributed to the development of the immune system in early life,and improved immune and anti-inflammatory responses at a later age.The overall results suggest that PE could be supplemented at 5 g/d for preweaning dairy calves to protect against oxidative stress and infections while maintaining normal gut microbial hemostasis;and improve gut health and frequency of diarrhea without affecting growth performance and rumen fermentation characteristics.However,higher doses of amla fruit powder supplementation negatively affected the health and growth performance of preweaning calves.We have discussed our speculations for the reduced health and growth performance of calves supplemented with higher doses of amla.However,the cause of these negative effects is not clearly known yet.Thus,further studies are recommended to evaluate the level of toxicity and other related negative effects of amla supplementation on dairy calves.This dissertation discusses the main findings of the studies,scientific implications,limitations,and its significance from improving calf gut health and performance point of view. |
PDF Full Text Request