Effect of the ratio of dietary metabolizable energy to nitrogen content on production performance, serum metabolites, rumen fermentation parameters, and bacterial diversity in yaks

This study examined the effect of the ratio of dietary metabolizable energy (MJ) to nitrogen (g) content (ME:N) on average daily gain (ADG), blood biochemical indices, rumen fermentation parameters, and rumen bacterial community in yaks. Thirty-six male yaks, aged 2–3 years, were divided into three groups and received a ME:N ratio of 0.42 (HY), 0.36 (MY,) or 0.32 (LY) MJ/g. Dry matter intake ranged between 3.16 and 3.63 kg/d and was lesser (p < 0.001) in the LY group than the other two groups. ME intake increased (p < 0.001) with an increase in the ME:N ratio, while N intake did not differ among groups. The ADG was 660 g/day for the MY group, which was higher (p < 0.005) than the 430 g/day in the LY group, while the HY group gained 560 g/day and did not differ from the other two groups. Feed intake to ADG ratio ranged between 5.95 and 7.95, and numerically was highest in the LY group and lowest in the MY group. In general, the concentration of ruminal total volatile fatty acids (p < 0.03) and molar proportions of propionate (p < 0.04), increased, while the molar proportion of acetate (p < 0.005) and the acetate:propionate ratio decreased (p < 0.001) with a decrease in the ME:N ratio. The molar proportion of butyrate did not differ among groups (p = 0.112). Group MY had higher ruminal NH₃-N content than group HY and had a higher serum glucose content but lower urea content, lactate dehydrogenase, and creatine kinase content than group LY. In ruminal bacteria at the phylum level, the relative abundance of Firmicutes (F) was greater and of Bacteroidetes (B) was lesser, while the F:B ratio was greater in group MY than in groups HY an LY. We concluded that the yaks consuming the diet containing a ME:N ratio of 0.36 MJ/g had the best performance of the three groups.

Effect of Chinese Herbs on Serum Biochemical Parameters, Immunity Indices, Antioxidant Capacity and Metabolomics in Early Weaned Yak Calves

Chinese traditional herbs are used widely as feed supplements to improve the immune response and antioxidant capacity of livestock. Twenty early-weaned 4-month-old yak calves (72.3 ± 3.65 kg) were divided randomly into four groups (n = 5 per group); three groups were provided with supplementary 80 mL/kg DMI of the root water extracts of either Angelica sinensis, Codonopsis pilosula or Glycyrrhiza uralensis, and one group (control) was not provided with a supplement. Compared to control calves, calves consuming the three herbal extracts increased serum concentrations of albumin (ALB) and glutathione peroxidase (GSH-Px), but decreased serum concentrations of free fatty acids (FFAs) and malondialdehyde (MDA) (p < 0.05). Calves consuming A. sinensis decreased (p < 0.05) serum concentration of total cholesterol (TC), and increased (p < 0.05) serum concentration of total proteins (TP). Serum FFA concentrations increased (p = 0.004) linearly with time in the control group, but not in the groups consuming herbs. Serum metabolomic data demonstrated that A. sinensis and C. pilosula regulate mainly amino acid metabolism, while G. uralensis regulates mainly carbon and amino acid metabolism. It was concluded that the three herbal root extracts, as dietary supplements, improved energy and nitrogen metabolism, and enhanced the antioxidant capacity of yak calves.

Growth performance and mammary gland development of Holstein calves fed milk with 15% solids and treated with growth promoters

The objective of this study was to evaluate growth performance, and mammary gland parenchyma (PAR) development in Holstein female calves fed whole milk combined with milk replacer for 15% total solids (15TS) or only milk (11% TS; 11TS). The effects of zilpaterol hydrochloride (ZH) and an estrogenic implant (EI) on growth performance, serum metabolites, and PAR development in post-weaning calves (63-90 days of age) fed 15TS or 11TS were also investigated. In the first phase, 78 calves were randomly divided into two groups (n = 39/group), 15TS, or 11TS (5 to 8 L/day; starter ad libitum). After weaning, calves were randomly assigned to four treatments, no EI, EI, ZH, and ZH-EI. In phase 1, 15TS calves had greater (P < 0.01) average body weight at weaning than 11TS calves (82.0 ± 5.8 vs. 74.1 ± 5.7 kg). Pre-weaning average daily gain (718 ± 67 vs. 576 ± 64 g/day) was higher (P < 0.01) for 15TS calves than 11TS calves. Feed/gain (1.5 ± 0.3 vs. 1.8 ± 0.3 kg of DMI/kg of gain) was lower (P < 0.01) for 15TS calves than 11TS calves. PAR area (8.8 ± 3.3 vs. 5.0 ± 1.6 cm²) was greater (P < 0.01) for 15TS calves than 11TS calves. No differences (P > 0.10) in average daily gain (986 ± 79 g/day across treatments) were observed in calves receiving ZH, EI, or ZH-EI fed 15TS or 11TS diets previously. However, the PAR area of 15TS calves administered ZH-EI was 2.2 times greater (P < 0.01) than 11TS calves with no ZH and CI. This study demonstrated the benefits of supplying milk with 15% TS for enhancing overall animal growth and PAR development. Further use of ZH and EI during the post-weaning period did improve mammary PAR growth.

Influence of ractopamine hydrochloride supplementation on pancreatic digestive enzyme activity in finishing steers

Sixty-nine finishing steers were randomly assigned to one of two treatment groups: supplementation to provide 0 or 267 mg·d−1 of ractopamine hydrochloride (RAC) for 42 d. Twelve steers were slaughtered for tissue and blood collection. Final body weight (BW) tended to be greater with RAC supplementation. Ractopamine hydrochloride supplementation decreased liver mass as a percentage of BW. Pancreatic protein concentration, digestive enzyme activities, serum glucose, and insulin concentrations were not influenced by RAC supplementation. Ractopamine hydrochloride supplementation decreased the pancreatic:α-amylase:trypsin and serum urea nitrogen concentrations. These data suggest that RAC may influence pancreatic exocrine function in cattle.

Zilpaterol hydrochloride lowers marbling score by dilution of marbling and depression of intramuscular adipocyte volume in M. longissimus dorsi of beef steers

We hypothesized that zilpaterol hydrochloride (ZH) depresses marbling scores in beef cattle by dilution of the intramuscular (i.m.) adipose tissue in the longissimus thoracis (LT) by increased muscle cross-sectional area. Crossbred steers were treated with ractopamine hydrochloride (RH; 28 d) or ZH (20 d) or no β-adrenergic agonist (CON). ZH increased LT cross-sectional area (P < .001) and depressed rib fat depth (P < .001), USDA marbling score (P < .05), percent LT lipid (P < .02), total lipid in a 2.54 cm-thick LM steak (P < .05) and most LT lipid fatty acids (P ≤ .05),but had no effect on mean i.m. adipocyte volume (P = .15). ZH increased the relative volume proportion of smaller i.m. adipocytes (250 to 500 pL) and decreased the proportion of larger i.m. adipocytes (2000 and 3000 pL) (P < .05). We conclude that ZH reduces marbling score both by dilution of the marbling and a depression of i.m. adipocyte relative volumes.

Effect of natural feed additives on meat quality and caecotrophic fatty acid profile of New Zealand rabbits

ABSTRACT The objectives of this research were to evaluate the effects of commercial probiotic and chitosan as food additives on the quality and meat composition of 36 New Zealand White rabbits (57 ± 8 days old and 1,648 ± 0.194 kg) and on the fatty acid profile of caecotrophs. The treatments were CT (diets without inclusion of additives), PRO (inclusion of 4 g / kg of commercial probiotic) and CHI (inclusion of 4 g / kg of chitosan). The additives increased triglycerides and decreased urea compared to the control group, as well as increased oleic and linoleic acids, Ʃ unsaturated, Ʃ monounsaturated and Ʃ polyunsaturated in caecotrophs. CHI animals showed a decrease in myristic and palmitic acids compared to PRO. CHI decreased the meat's crude protein and the meat's fat. In addition, there was a decrease in omega-3, omega-6 and the relationship unsaturated and saturated fatty acids for the CHI group and an increase in erucic acid and a decrease in the rate of hypocholesterolemic acids. As a conclusion, the data showed that the animals that ingested probiotic had better meat quality, for having better fatty acid profile and hypocholesterolemic index, compared to the treatment with chitosan. The additives improved the caecotrophs fatty acid profile.

Serum blood metabolite response and evaluation of select organ weight, histology, and cardiac morphology of beef heifers exposed to a dual corticotropin-releasing hormone and vasopressin challenge following supplementation of zilpaterol hydrochloride

The objectives of this study were 1) to determine if supplementation of zilpaterol hydrochloride (ZH) altered select organ weights, histology, and cardiac anatomical features at harvest and 2) to determine if administration of a corticotropin-releasing hormone (CRH) and vasopressin (VP) challenge following 20 d of ZH supplementation altered the blood chemistry profile in cattle. Crossbred heifers ( = 20; 556 ± 7 kg BW) were randomized into 2 treatment groups: 1) control (CON), without ZH, and 2) zilpaterol (ZIL; ZH at 8.33 mg/kg [DM basis] for 20 d). On d 20 of supplementation, heifers were fitted with indwelling jugular catheters. On d 24, starting at 0800 h and continuing until 1600 h, blood samples were collected at 60-min intervals. At 1000 h, heifers received an i.v. bolus of CRH (0.3 µg/kg BW) and VP (1.0 µg/kg BW) to activate the stress axis. Serum was separated and stored at -80°C until analyzed for a large-animal chemistry panel. Following the CRH/VP challenge, heifers were harvested on d 25, 26, and 27 (5, 6, and 7 d after ZH supplementation); BW, HCW, select organ weights, and histology were measured, and a total heart necropsy was performed. A treatment effect ( ≤ 0.02) was observed for Ca, K, creatinine, alkaline phosphatase, and sorbitol dehydrogenase. Zilpaterol-fed heifers had decreased ( ≤ 0.02) concentrations of Ca and K and increased concentrations ( 0.01) of creatinine ( = 0.02) during the CRH/VP challenge when compared to control heifers. Control heifers had greater ( ≤ 0.05) alkaline phosphatase and sorbitol dehydrogenase concentrations when compared with ZIL heifers. A treatment × time interaction ( = 0.02) was observed for P; concentrations were similar between treatments from -2 to 6 h postchallenge, and 7 h postchallenge CON heifers had decreased P. Liver ( = 0.06) and kidney ( = 0.08) weights as a percentage of BW tended ( ≤ 0.08) to be reduced in ZIL heifers. Gross liver weights tended ( = 0.08) to be lower in ZIL heifers. Other organ (heart, lung, adrenals) to BW ratios remained similar ( ≥ 0.41). These data suggest that there are some variations observed between treatments in terms of response to ZH supplementation and the CRH/VP challenge; however, in the environmental conditions of this study, limited variation in blood metabolic responses and organ weights suggests that the supplementation of ZH did not detrimentally alter the physiology of cattle.

Interaction between supplemental zinc oxide and zilpaterol hydrochloride on growth performance, carcass traits, and blood metabolites in feedlot steers

Interactive effects of supplemental Zn and zilpaterol hydrochloride (ZH) were evaluated in feedlot steers ( = 40; 652 kg ± 14 initial BW) to determine their impact on feedlot performance, blood constituents, and carcass traits. The study was conducted as a randomized complete block design with a 2 × 2 factorial treatment arrangement. Steers were blocked by BW and randomly assigned to treatments. Factors consisted of supplemental Zn (60 or 300 mg/kg diet DM) and ZH (0 or 8.33 mg/kg) in the diets. For diets supplemented with 300 mg Zn/kg DM, 60 mg Zn/kg was supplemented as zinc sulfate and 240 mg Zn/kg was supplemented as zinc oxide, and the diet was fed for 24 d. Zilpaterol hydrochloride was fed for 21 d followed by a 3-d withdrawal. Cattle were housed in partially covered individual feeding pens equipped with automatic waterers and fence-line feed bunks and were fed once daily for ad libitum intake. Plasma samples were collected on d 0 and 21 to assess changes in Zn, plasma urea nitrogen (PUN), glucose, and lactate concentrations, and serum samples were collected on d 21 to assess IGF-1 concentration. On d 25, cattle were weighed and transported 450 km to a commercial abattoir for harvest; HCW and incidence of liver abscesses were recorded. Carcass data were collected after 36 h of refrigeration. Data were analyzed as a mixed model with Zn, ZH, and Zn × ZH as fixed effects; block as a random effect; and steer as the experimental unit. No interaction or effects of Zn or ZH were observed for IGF-1 concentration, plasma glucose, or lactate concentrations ( ≥ 0.25). No interaction between Zn and ZH was observed for PUN concentration, but PUN decreased with ZH ( < 0.01). There were no effects of ZH or Zn on ADG, DMI, final BW, feed efficiency, HCW, back fat, KPH, quality grade, or incidence of liver abscesses ( > 0.05). Zinc supplementation tended ( = 0.08) to improve the proportion of carcasses grading USDA Choice. Feeding ZH decreased yield grade ( = 0.05) and tended to increase LM area ( = 0.07). In conclusion, increasing dietary concentrations of Zn does not impact response to ZH, but feeding ZH altered circulating concentrations of PUN.

Skeletal muscle and liver gene expression profiles in finishing steers supplemented with Amaize

Our main objective was to evaluate the effects of feeding α-amylase (Amaize, Alltech Inc., Nicholasville, KY, USA) for 140 days on skeletal muscle and liver gene transcription in beef steers. Steers fed Amaize had lower average daily gain (p = .03) and gain:feed ratio (p = .05). No differences (p > .10) in serum metabolites or carcass traits were detected between the two groups but Amaize steers tended (p < .15) to have increased 12th rib fat depth. Microarray analysis of skeletal muscle revealed 21 differentially expressed genes (DEG), where 14 were up-regulated and seven were down-regulated in Amaize-fed steers. The bioinformatics analysis indicated that metabolic pathways involved in fat formation and deposition, stress response, and muscle function were activated, while myogenesis was inhibited in Amaize-fed steers. The quantitative PCR results for liver revealed a decrease (p < .01) in expression of fatty acid binding protein 1 (FABP1) and 3-hydroxybutyrate dehydrogenase 1 (BDH1) with Amaize. Because these genes are key for intracellular fatty acid transport, oxidation and ketone body production, data suggest a reduction in hepatic lipid catabolism. Future work to investigate potential positive effects of Amaize on cellular stress response, muscle function, and liver function in beef cattle appears warranted.

Effects of ractopamine hydrochloride on growth performance, carcass characteristics, and physiological response to different handling techniques

Feedlot cattle ( = 128; BW = 549 ± 60 kg) were used to evaluate the effects of ractopamine hydrochloride (RAC) on growth performance, physiological response to handling, and mobility during shipment for slaughter in a study utilizing a split-plot design with a 2 × 2 factorial arrangement of treatments: 1) diet (CON [no β-adrenergic agonist] vs. RAC [400 mg·animal·d ractopamine hydrochloride for 28 d]) and 2) handling intensity (HI; low-stress handling [LSH; cattle moved at a walking pace with no electric prod use] vs. high-stress handling [HSH; cattle moved at a minimum of a trot and an electric prod applied while in the alley for posthandling restraint and during loading for shipment to the abattoir]). Cattle fed RAC tended to have greater ADG and G:F ( = 0.06), and had greater HCW and LM area ( = 0.04). The HI treatments were applied on the day after the 28-d growth performance period. Blood samples were collected before HI treatment (baseline), after HI treatments (POSTHAND), after transport to the abattoir (POSTTRANS), and during exsanguination at slaughter. A diet × HI interaction ( = 0.01) was observed in the change in cortisol from baseline to POSTTRANS, and there tended ( ≤ 0.07) to be diet × HI interactions for the change in epinephrine from baseline to POSTHAND and for the change in creatine kinase (CK) from baseline to POSTTRANS. Feeding RAC and HSH both increased the change from baseline to POSTHAND in norepinephrine and pH ( ≤ 0.05). The HSH cattle also had greater changes from baseline to POSTHAND in blood HCO, base excess, partial pressure of CO, lactate, cortisol, and glucose ( ≤ 0.01). Ractopamine and HSH both produced greater increases in CK concentrations from baseline to slaughter ( < 0.01). Mobility was not affected by RAC at the feedlot or following an average 6-h lairage ( ≥ 0.43). This study confirms RAC improves growth performance and suggests metabolic acidosis, a precursor to fatigued cattle syndrome, develops in cattle allowed to trot without the use of a lead rider regardless of RAC administration. Cattle fed RAC displayed altered hormonal responses to handling and transport stress, and the overall proportion of cattle with compromised mobility appears to increase later in the marketing channel. These findings warrant additional research aimed at better understanding the physiological response to stress and protect the welfare of cattle during shipment for slaughter.

Effects of zilpaterol hydrochloride on methane production, total body oxygen consumption, and blood metabolites in finishing beef steers

An indirect calorimetry experiment was conducted to determine the effects of feeding zilpaterol hydrochloride (ZH) for 20 d on total body oxygen consumption, respiratory quotient, methane production, and blood metabolites in finishing beef steers. Sixteen Angus steers (initial BW = 555 ± 12.7 kg) were individually fed at ad libitum intake and used in a completely randomized design. The model included the fixed effects of dietary treatment, day, and treatment × day. Dry matter intake did not differ between the treatments ( = 0.89), but was greater on d 0 than any other day ( < 0.01). Oxygen consumption was not different between treatments ( = 0.79), but was different across day ( < 0.01) on d 7, 14, 21, and 28. Respiratory quotient was less for cattle fed ZH than control ( < 0.01), and also different across day ( < 0.01), being greater on d 7, 21, and 28 than d 3 or 21. Methane production (L/kg of DMI) was greater for steers fed the control vs. the ZH diet ( < 0.01), and it also differed by day ( < 0.01), being greater on d 21 and 28 than d 0, 3, 7, and 14. Nonesterified fatty acids were not different across treatments ( = 0.82), and there was no effect of treatment on β-hydroxybutyrate concentration ( = 0.45). Whole blood glucose concentrations were not affected by feeding ZH in this experiment ( = 0.76); however, lactate concentrations were reduced by feeding ZH ( = 0.03). Additionally, there was no treatment effect on ɑ-amino-N, blood glutamate, or glutamine ( ≥ 0.16). Plasma NH was not affected by ZH ( = 0.07), but plasma urea nitrogen was reduced by ZH ( < 0.01). Urinary creatinine was increased by steers receiving ZH ( = 0.01), and urine 3-methylhistidine (3-MH) concentrations were normalized to creatinine, the 3-MH:creatinine ratio decreased from d 0 to d 3 in steers fed ZH, and remained less than control steers until d 28. These data provide insight into how β-agonists alter nutrient partitioning and improve the efficiency of tissue accretion, mainly through decreased muscle protein turnover and altering the catabolic fuel for peripheral tissues.

Effects of dietary urea concentration and zilpaterol hydrochloride on performance and carcass characteristics of finishing steers

Cattle receiving zilpaterol hydrochloride () may recycle less N and require a greater supply of RDP. This study evaluated effects of ZH on performance and carcass characteristics of steers fed diets with increasing dietary RDP concentrations supplied as urea. Steers (429 animals; BW = 423 ± 4.5 kg) were sorted into 3 blocks according to BW and assigned to 1 of 6 treatments (6 pens per treatment) in a randomized complete block design. Treatments were a 2 × 3 factorial arrangement of either no ZH or ZH (75 mg ZH per steer daily) supplemented to finishing diets containing 0, 0.5, or 1.0% urea of dietary DM. Pen weights were recorded before treatment initiation; urea was fed for 27 d, and ZH treatments were fed for 24 d with a 3-d withdrawal period. Pen weights were recorded before transporting steers to a commercial abattoir. Continuous response variables were analyzed using the MIXED procedure and categorical data were analyzed using the GLIMMIX procedure of SAS. No ZH × dietary urea interactions ( ≥ 0.14) occurred for all performance and carcass response variables. Feeding ZH for the last 27 d (included a 3-d withdrawal period) of the finishing period increased ( < 0.01) ADG, decreased ( < 0.01) DMI, and increased ( < 0.01) G:F compared with no ZH. In addition, ZH increased HCW ( < 0.01), dressing percentage ( < 0.01), LM area ( < 0.01), and decreased ( = 0.01) yield grade. Increasing dietary urea linearly decreased ( = 0.01) ADG and DMI. A tendency for a linear decrease ( = 0.10) in HCW, and a tendency for a quadratic increase ( = 0.07) in marbling score were observed as urea increased in the diet. Results indicate that cattle supplemented with ZH do not require additional RDP in the diet, and that performance and carcass characteristics were negatively affected when urea was increased in the diet.

Zilpaterol hydrochloride improves feed efficiency and changes body composition in nonimplanted Nellore heifers

This research aimed to evaluate the effects of zilpaterol hydrochloride (ZH; MSD Animal Health, São Paulo, SP, Brazil) on the performance, carcass traits, serum metabolites, body composition, and gain composition of nonimplanted Nellore heifers. Nellore heifers ( = 72; average BW = 267 ± 16 kg; average 18 mo of age) were maintained in a feedlot system for 118 d. Heifers were separated into 2 groups: Control and ZH. The ZH group received ZH (8.3 mg/kg diet DM) for 30 d with 3 d of withdrawal before slaughter. Heifers were allotted to 18 pens, 9 pens per treatment, and assigned to a randomized block design. The animals were weighed, blood samples were collected, and subgroups of heifers were slaughtered at the beginning of supplementation and after 20 and 33 d to evaluate performance, blood metabolites, empty BW (EBW), and EBW composition. Hot carcass and kidney-pelvic fat weights were recorded at slaughter. At 24 h postmortem, carcasses were fabricated and the 9-10-11th rib (HH) section was removed from the primal rib to analyze moisture, protein, ash, and ether extract (EE) content in empty body (EB) and gain composition. Heifers fed ZH had gains in HCW that were 19.7 kg greater than controls, reflecting the 30% increase ( < 0.01) in ADG. There was no change in DMI, resulting in a 20% greater G:F ratio ( < 0.01) for heifers fed ZH. Heifers supplemented with ZH had carcass dressing percentages that were 3% greater than controls ( < 0.01), and there was also a 19% reduction in kidney-pelvic fat ( = 0.05) in ZH-treated heifers. Zilpaterol increased serum creatinine ( < 0.01), tended to increase ( = 0.06) serum triacylglycerol, decreased serum NEFA ( = 0.04), and tended to decrease ( = 0.06) serum glucose. The EBW composition was changed after 20 d of ZH supplementation ( = 0.02), with ZH increasing the moisture, ash, and protein contents, whereas carcass fat was decreased by ZH by 14%. Consequently, the carcass CP:EE ratio after 20 d was increased ( = 0.03) by 24% with ZH supplementation. There was no change on EBW composition after 30 d of ZH supplementation ( = 0.17). Regarding carcass gain composition, ZH increased EBW gain ( = 0.02) by 842 g/d from d 0 to d 30, EB protein gain by 221 g/d ( = 0.05) from d 0 to d 20, and by 180 g/d ( = 0.01) from d 0 to d 33. In conclusion, ZH supplementation in nonimplanted Nellore heifers altered the composition of body weight gain, promoting greater lean tissue deposition and improving feed efficiency.