| This study was conducted to investigate the effect of feeding antibiotic-containing milk on growth performance, blood indicator, gastrointestinal development of Holstein calves,and was to explore if having an impact on Holstein calves and the effect mechanism. That would provide the theory basis for domestic dairy farm on utilizing antimicrobial milk to feed calves and for the way of optimal utilization in future research.(1) In this experiment, β-lactam antibiotic residuces were detected for 143.00 to 347.40 μg/L in antibiotic-containing milk. The milk protein and somatic cell counts were all significantly higher than bulk milk(P<0.05). There were no differences on lactose, fat, total solids, and milk urea nitrogen between antibiotic milk and bulk milk(P>0.05). It was concluded that the antibiotic residues existes in the milk producted by disease of cows in the progress of treatment and affects the milk composition.(2) Eighteen Holstein male calves with similar body weight were selected and devided into one of two feeding groups with randomized design. The 9 Holstein male calves of control group were fed bulk milk, and another half of experiment group were fed antibiotic-containing milk from day 3 to 60 of life. And subsequently replaced milk completely with pellet diet and Chinese wildrye from day 61 to 180 of life. Body weight and measurement were respectively measured on the days of 3, 30, 60, 90, and 180 in the calves growing period, and then calculated the average daily gain and measurement index. Fecal score was recorded in the priority period of 60 days of age, and then calculated the diarrhea rate in any period. The body weight on 30 days and the ADG from day 3 to 60 of calves fed antibiotic-containing milk were all less than that of calves fed bulk milk(P<0.05); However, the body weight on 60, 90, and 180 days and ADG from 60 to 180 days or 3 to 180 days were all not affected by feeding antimicrobial milk(P>0.05). Body measurement and diarrhea rate for calves fed antibiotic-containing milk were all not different from calves fed bulk milk(P>0.05). Compared with control group, the body length on 90 days, the heart girth on 60 days and 90 days, and leg circumference on 180 days of experiment group were all decreased significantly(P<0.05); No differences on male calves’ height, body straight length, cannon bone circumference, and chest depth between control and experiment group(P>0.05). Likewise, there were no differences on limb length index, body length index, body body index, pipe circumference index, chest circumference index, and leg circumference index in any measement time between two groups(P>0.05). Feeding antimicrobial milk to calves significantly increased fecal score from 3 to 60 days and diarrhea rate from 11 to 30 days(P<0.05). It was included that feeding antibiotic-containing milk could limit calves’ growth development before or after weaning, which may be affected by diarrhea; but the growth development could be recovered on days of 180.(3) Blood-sampling would be taken on calves’ breeding days of 7, 15, 30, 60, 90, and 180, and then measured blood indicators including glucose, urea nitrogen, triglycerides, glutamic pyruvic transaminase, glutamic oxalacetic transaminase; and the immune indexes including IgA, IgM, IgG, IL-1β, IL-2, IL-6, and TNF-α. The experiment results showed that feeding antibiotic-containing milk decreased blood glucose on 60 days(P<0.05), and respectively increased blood triglycerides on 90 days(P<0.05), glutamic pyruvic transaminase on 90 days(P<0.05), glutamic oxalacetic transaminase on 180 days(P<0.05); but not affected urea nitrogen concentrations(P>0.05). For the immune indicators, compared with control group, the IgA levels on 30 days of experiment group was very significantly increased(P<0.01), as well as on 90 days was increased significantly(P<0.05); the IgM levels on 7 days, the IgG levels on 60 days, and IL-2 levels of experiment group was significantly increased, respectively(P<0.05); the TNF-α levels on 15 days of experiment group of test group was very significantly increased(P<0.01); but no differences on IL-1β and IL-6 between control and experiment group(P>0.05). It was included that feeding antibiotic-containing milk may contribute to a certain influence on the metabolism of blood glucose and triglycides, and damage on liver. In addition, to a certain extent, to enhance immune function of calf.(4) The Holstein male calves were slaughtered on 60, 90 and 180 days of breeding period. The pH value of rumen, abomasum, duodenum, jejunum, ileum, and cecum was respectively determined after opened abdominal cavity. The fresh weight of internal organs were determined, and then calculate organ indexes. Biopsy of rumen and intestine was taken respectivelsy of rumen and intestine was taken respectively, and then observed its morphological changes. The test results showed that feeding antibiotic-containing milk increased Holstein calves’ rumen and reticulum weight on 180 days(P<0.05). Compared with control group, the calves’ reticulum index on 180 days and the abomasum index on 60 days of experiment group were all significantly increased(P<0.05); on the contrary, the jejunum index on 60 days was significantly decreased(P<0.05). The pH values in rumen, abomasum, duodenum, jejunum, ileum, colon and caecum on 60, 90 and 180 days between two groups had no any differences(P>0.05). Compared with control group, nipple height on rumen ventral blind sac of experiment group on days 60 and nipple width on days 90 were respectively decreased significantly(P<0.05). While submucosa thickness, papilla superficial area and muscular layer thickness on days 60, 90, 180 of life was not different(P>0.05). Likewise, nipple height, width, submucosa thickness, papilla superficial area, muscular layer thickness rumen dorsal sac were not different(P>0.05). Feeding antibiotic-containing milk decreased duodemum villous height on 60 days of life and mucosal thickness on 180 days of life(P<0.05), increased duodemum crypt depth on 90 days of life(P<0.05). Compared with control group, the experiment group’s jejunum villous height and the jejumum villous height/crypt depth(V/C) on 90 days of life, and jejunum mucosal thickness on 180 days of life were all decreased significantly(P<0.05), on the contrary, the jejumum crypt depth on 90 days of life was increased(P<0.05). However, no differences were found in ileum villous height, villous width, crypt depth, V/C, mucosal thickness, and muscle layer thickness of any test time between control and experiment group(P>0.05). It was concluded that feeding antibiotic-containing milk in a long period did not cause damage to liver, but to a certain extent affect calves’ gastrointestinal development, especially in the development of small intestine.The experimental results prove that antimicrobial milk contained a certain amount of antibiotic resistance, and the milk composition content would changed with different pathological and physiological state of lactation cows; Feeding antibiotic-contaminated milk would increase the risk of diarrhea in calves that would affect the growth of calves before and after weaning; However, to a certain extent, would improve the immune function of calves; In addition, the effects of feeding antimicrobial milk on gastrointestinal development mainly reflected in the influence on the development of the small intestine, but did not cause damage to the liver. |
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