Long-term and combined effects of N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide and fumaric acid on methane production,rumen fermentation, and lactation performance in dairy goats

Background:In recent years,nitrooxy compounds have been identified as promising inhibitors of methanogenesis in ruminants.However,when animals receive a nitrooxy compound,a high portion of the spared hydrogen is eructated as gas,which partly offsets the energy savings of CH4mitigation.The objective of the present study was to evaluate the long-term and combined effects of supplementation with N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide(NPD),a methanogenesis inhibitor,and fumaric acid(FUM),a hydrogen sink,on enteric CH4production,rumen fermentation,bacterial populations,apparent nutrient digestibility,and lactation performance of dairy goats.Results:Twenty-four primiparous dairy goats were used in a randomized complete block design with a 2×2factorial arrangement of treatments:supplementation without or with FUM(32 g/d)or NPD(0.5 g/d).All samples were collected every 3 weeks during a 12-week feeding experiment.Both FUM and NPD supplementation persistently inhibited CH4yield(L/kg DMI,by 18.8%and 18.1%,respectively)without negative influence on DMI or apparent nutrient digestibility.When supplemented in combination,no additive CH4suppression was observed.FUM showed greater responses in increasing the molar proportion of propionate when supplemented with NPD than supplemented alone(by 10.2%vs.4.4%).The rumen microbiota structure in the animals receiving FUM was different from that of the other animals,particularly changed the structure of phylum Firmicutes.Daily milk production and serum total antioxidant capacity were improved by NPD,but the contents of milk fat and protein were decreased,probably due to the bioactivity of absorbed NPD on body metabolism.Conclusions:Supplementing NPD and FUM in combination is a promising way to persistently inhibit CH4emissions with a higher rumen propionate proportion.However,the side effects of this nitrooxy compound on animals and its residues in animal products need further evaluation before it can be used as an animal feed additive.

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health, milk performance, and profitability of dairy cows. The objective of this study was to determine the effect of reduced energy density of dose-up diets on dry matter intake （DMI）, lactation performance and energy balance （EB） in multiparous Holstein cows which were housed in a free-stall barn and fed for ad libitum intake. Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet [HD, n = 13; 6.8 MJ of net energy for lactation （NEL）/kg; 14.0% crude protein （CP） ], or a middle energy density diet （MD, n = 13; 6.2 MJ NEh/kg; 14.0% CP）, or a low energy density diet （LD, n = 13; 5.4 MJ NEh/kg; 14.0% CP） from d 21 before expected day of calving. After parturition, all cows were fed the same lactation diet to d 70 in milk （DIM）. The DMI and NEE intake prepartum were decreased by the reduced energy density diets （P 〈 0.05）. The LD group consumed 1.3 last 24 h before calving. The milk yield and the postpartum kg/d （DM） more diet compared with HD group in the DMI were increased by the reduced energy density diet prepartum （P 〈 0.05）. The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation （P 〈 0.05）. The energy consumption for HD, MD and LD groups were 149.8%, 126.2% and 101.1 % of their calculated energy requirements prepartum （P 〈 0.05）, and 72.7%, 73.1% and 7.5.2% during the first 4 wk postpartum, respectively. In conclusion, the low energy density prepartum diet was effective in controlling NF_L intake prepartum, and was beneficial in increasing DMI and milk yield, and alleviating negative EB postpartum.

Effects of Diets with Different Corn-to-Soybean Ratios on Performance of Lactational Rex Rabbits

[ Objective] To study the effects of diets with different com-to-soybean ratios on production performance of lactational Rex rabbits and select the best feed formula. [Method] A total of 80 lactational healthy Rex rabbits （similar age, body weight and delivery time） were randomly divided into five groups, 16 in each group. The Rex rabbits in group I were fed with corn-based meal diet, group II with soybean-based meal diet, group III with the developed corn-soybean meal diet, group IV with corn-soybean meal free diet, and group CK with conventional corn-soybean meal diet. During the lactation period, the changes in the lactation performance, growth rate of baby rabbits, weight and feed costs were observed. [ Result] The lactation performance of mother rabbits and the growth rate of baby rabbits in the experimental groups were similar to that in the control group. The weaning survival rate of the group III was the highest, but it was not significantly higher than that of the control group. The weaning survival rate of the other three groups was lower than that of the control group （P〈0.05）. The weight loss of mother rabbits in the group I, II and III was not significantly different from that of the control group, but the weight loss of the group IV was higher than that of the control group （ P 〈 0.01 ）. [ Conclusion] Diets with appropriate corn-to-soybean ratios not only reduce feed costs but also give the best feeding effects.

Lactation Performance of Primiparous Nubian Ewes and Yunling Black Ewes

[ Objective] To evaluate lactation performance of primiparous Nubian ewes and Yunling Black ewes. [ Method] Healthy primiparous Nubian ewes （20 ewes lambing twins and 19 ewes lambing single） and Yunling Black ewes （4 ewes lambing twins and 15 ewes lambing single） were used to study the effects of breeds and litter size on lactation performance. [Result] The total milk yield of the Nubian ewes lambing twins was 14.81% higher than that of the Nubian ewes lambing single （ P 〈 0.05） and 22.93% higher than that of the Yunling Black ewes lambing twins （ P 〈 0.05）. The total milk yield of the Yunling Black ewes lambing twins was 32.80% higher than that of the Yunling Black ewes lambing single （ P〈 0.05 ）, but the total milk yield of the Nubian ewes lambing single was 42.20% higher than that of the Yunling Black ewes lambing single （ P 〈 0.05）. The Nubian goats and the Yunling Black goats had similar lactation curves. The milk yield gradually increased during the early lactation period （5 - 15 d post partum）, and the lactation peak lasted for 20 d （15 -35 d post partum）. Then the milk yield gradually decreased. The predicted values showed the milk yield of the ewes may rapidly decrease during 80 -120 d post partum. Until Day 70 post partum, the Nubian ewes lambing twins had lost 3.06% more body weight than those lambing single had （P〈0.05）; the Yunling Black ewes lambing twins had lost 0.89% more body weight than those lambing single had （P〈0.05）. The Nubian ewes lambing lost 3.22% -5.39% more body weight than those with the same litter size did （ P 〈 0.05）. [ Conclusion] The regular pattern of primiparous lactation is similar between the Nubian ewes and the Yunling Black ewes, and their lactation performance is closely related to breeds and litter size.

Effects of Supplemental Carbohydrate Sources on Lactation Performance, Nitrogen Balance,and Ruminal Fermentation in Dairy Cows Fed Energy-Deficient Total Mixed Rations

The effects of supplemental carbohydrate （CHO） sources on milk yield and composition, nitrogen （N） balance,and ruminal fermentation were evaluated in lactating dairy cows fed energy-deficient total mixed rations （TMR） . Fifty-six lactating Holstein cows （36. 8 ± 3. 4 kg / d of milk yield; 152 ± 26 days in milk [DIM]） were randomly assigned to one of four diets： （1） basal TMR （control） ; （2） basal TMR ＋ 1. 25 kg / d sucrose （SUC） ; （3） basal TMR ＋ 2. 12 kg /d steam-flaked corn （SFC） ; （4） basal TMR ＋ 2. 23 kg / d wheat （WHE） . The trial lasted 70 days,including the first 10 days of adaptation. Simultaneously, a 4 × 4 Latin square trial was conducted with four ruminally cannulated cows of similar DMI （Dry Matter Intake） fed on the above four diets. Each testing period lasted 18 days： 15 days for adaptation and 3 days for sampling. Cows fed SUC-,SFC-,and WHE-supplemented diets produced 1. 6,2. 9,and 0. 8 kg / d,respectively,more milk than those on the basal TMR control diet,but the difference was not significant （P = 0. 160） . However,the production of energy-corrected milk of cows fed CHO-supplemented diets improved significantly （P = 0. 020） ,and the yield of 4% fatcorrected milk tended to be higher （P = 0. 063） than in control animals. Percentages of milk protein,lactoseand solids-not-fat （SNF） increased significantly in cows fed CHO-supplemented diets （P 〈 0. 05） ,and yields of milk protein and SNF were significantly higher （P 〈0. 05） ; yields of milk fat and lactose were somewhat higher （P 〈 0. 10） . Cows receiving supplementary CHO diets consumed more DM （Dry Matter） （P = 0. 023） ; however,there was no significant difference in N retention,digestibility,or utilization efficiency among the treatments （P 〉 0. 10） . The average ruminal pH was lowest in cows supplemented with SUC,while that in cows supplemented with SFC and WHE was only slightly reduced （P = 0. 025） . Ruminal NH 3 -N concentration was highest with no supplementary CHO （P = 0. 017） ,and changes in postfeeding time were similar across the diets. Total volatile fatty acid concentration was significantly lower in control animals than in those on SUCand WHE-supplemented diets （P = 0. 001） ; significant dietary responses were observed in the concentrations of acetate,butyrate,and branchedchain fatty acids and in the acetate-to-propionate ratio （P 〈0. 001） . These results indicate that supplementation with different CHO sources in energy-deficient diets substantially improved the balance of energy and N in the rumen,altered ruminal fermentation,and improved lactation performance in dairy cows.

Heat stress affects dairy cow health status through blood oxygen availability

Background Rises in global warming and extreme weather occurrence make the risk of heat stress(HS)induced by high ambient temperatures more likely in high-yielding dairy cows,resulting in low milk quality and yield.In ani-mals,oxygen is involved in many physiological and metabolic processes,but the effects of HS on oxygen metabolism remain unclear.Thus,the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield,milk composition,and blood biochemical variables of cows under different levels of HS:none(No-HS),mild(Mild-HS),and moderate HS(Mod-HS).Results The HS significantly increased rectal temperature(Ptreat<0.01)and respiration rate(Ptreat<0.01).Under Mod-HS,greater Na+(P<0.05)and lower total CO_(2),and pH(P<0.05)were observed relative to those under No-HS and Mild-HS.Oxygen concentrations in both coccygeal artery and mammary vein(Ptreat<0.01)were lower under Mod-HS than under No-HS.Coccygeal vein concentrations of heat shock protein 90(HSP90)(P<0.05)increased during Mod-HS compared with those in cows under No-HS.Malondialdehyde increased during Mod-HS,and glu-tathione peroxidase(P<0.01)increased during Mild-HS.Coccygeal vein concentrations of vascular endothelial growth factor(P<0.01),heme oxygenase-1(P<0.01),and hypoxia-inducible factor 1α(P<0.01)were greater in cows under Mod-HS than those under No-HS.Red blood cell count(P<0.01)and hemoglobin concentration(P<0.01)were lower in the coccygeal vein of dairy cows under Mild-and Mod-HS than those of cows under No-HS.Conclusions Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limit-ing oxygen metabolism and transportation.However,the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

Rumen microbiome structure and metabolites activity in dairy cows with clinical and subclinical mastitis

Background:Due to the high prevalence and complex etiology,bovine mastitis(BM)is one of the most important diseases to compromise dairy cow health and milk quality.The shift in milk compositions has been widely investigated during mastitis,but recent studies suggested that gastrointestinal microorganism also has a crucial effect on the inflammation of other peripheral tissues and organs,including the mammary gland.However,research focused on the variation of rumen inner-environment during mastitis is still limited.Therefore,the ruminal microbial profiles,metabolites,and milk compositions in cows with different udder health conditions were compared in the present study.Furthermore,the correlations between udder health status and ruminal conditions were investigated.Based on the somatic cell counts(SCC),California mastitis test(CMT)parameters and clinical symptoms of mastitis,60 lactating Holstein dairy cows with similar body conditions(excepted for the udder health condition)were randomly divided into 3 groups(n=20 per group)including the healthy(H)group,the subclinical mastitis(SM)group and the clinical mastitis(CM)group.Lactation performance and rumen fermentation parameters were recorded.And rumen microbiota and metabolites were also analyzed via 16S rRNA amplicon sequencing and untargeted metabolomics,respectively.Results:As the degree of mastitis increased,rumen lactic acid(LA)(P<0.01),acetate,propionate,butyrate,valerate(P<0.001),and total volatile fatty acids(TVFAs)(P<0.01)concentrations were significantly decreased.In the rumen of CM cows,the significantly increased bacteria related to intestinal and oral inflammation,such as Lachnospiraceae(FDR-adjusted P=0.039),Moraxella(FDR-adjusted P=0.011)and Neisseriaceae(FDR-adjusted P=0.036),etc.,were accompanied by a significant increase in 12-oxo-20-dihydroxy-leukotriene B4(FDR-adjusted P=5.97×10^(−9))and 10beta-hydroxy-6beta-isobutyrylfuranoeremophilane(FDR-adjusted P=3.88×10^(−10)).Meanwhile,in the rumen of SM cows,the Ruminiclostridium_9(FDR-adjusted P=0.042)and Enterorhabdus(FDR-adjusted P=0.043)were increased along with increasing methenamine(FDR-adjusted P=6.95×10^(−6)),5-hydroxymethyl-2-furancarboxaldehyde(5-HMF)(FDR-adjusted P=2.02×10^(−6))and 6-methoxymellein(FDR-adjusted P=2.57×10^(−5)).The short-chain fatty acids(SCFAs)-producing bacteria and probiotics in rumen,including Prevoterotoella_1(FDRadjusted P=0.045)and Bifidobacterium(FDR-adjusted P=0.035),etc.,were significantly reduced,with decreasing 2-phenylbutyric acid(2-PBA)(FDR-adjusted P=4.37×10^(−6)).Conclusion:The results indicated that there was a significant shift in the ruminal microflora and metabolites associated with inflammation and immune responses during CM.Moreover,in the rumen of cows affected by SM,the relative abundance of several opportunistic pathogens and the level of metabolites which could produce antibacterial compounds or had a competitive inhibitory effect were all increased.

Transfer of β-hydroxy-β-methylbutyrate from sows to their offspring and its impact on muscle fiber type transformation and performance in pigs

Background： Previous studies suggested that supplementation of lactating sows with β-hydroxy-β-methylbutyrate（HMB） could improve the performance of weaning pigs, but there were little information in the muscle fiber type transformation of the offspring and the subsequent performance in pigs from weaning through finishing in response to maternal HMB consumption. The purpose of this study was to determine the effect of supplementing lactating sows with HMB on skeletal muscle fiber type transformation and growth of the offspring during d 28 and180 after birth. A total of 20 sows according to their body weight were divided into the control（CON, n = 10） or HMB groups（HMB, n = 10）. Sows in the HMB group were supplemented with β-hydroxy-β-methylbutyrate calcium（HMB-Ca） 2 g/kg feed during d 1 to 27 of lactation. After weaning, 48 mixed sex piglets were blocked by sow treatment and fed standard diets for post-weaning, growing, finishing periods. Growth performance was recorded during d 28 to 180 after birth. Pigs were slaughtered on d 28（n = 6/treatment） and 180（n = 6/treatment） postnatal and the longissimus dorsi（LD） was collected, respectively.Results： The HMB-fed sows during lactation showed increased HMB concentration（P ＆lt; 0.05） in milk and LD of weaning piglets（P ＆lt; 0.05）. In addition, offsprings in HMB group had a higher finishing BW and lean percentage than did pigs in CON group（P ＆lt; 0.05）, meanwhile, compared with pigs from sows fed the CON diet, pigs from sows fed HMB diet showed higher type Ⅱ muscle fiber cross-sectional area（CSA）, elevated myosin heavy chain（MyHC） Ⅱb and Sox6 mRNA, and fast-MyHC protein levels in LD（P ＆lt; 0.05）.Conclusions： HMB supplemented to sow diets throughout lactation increases the levels of HMB in maternal milk and skeletal muscle of pigs during d 28 after birth and promotes subsequent performance of pigs between d 28 and 180 of age by enhancing glycolytic muscle fiber transformation.

Improvement Effects of Guizhou Local Yellow Cattle Crossbred with Fleckvieh

[Objective] The aim was to discuss the improvement effect of Guizhou local yellow cattle crossbred with Fleckvieh. [Method] With Fleckvieh as male parent, they were crossbred with Guizhou local yellow cattle （ ♀ ）, and hybridized cattle of Simmental × local yellow cattle （ ♀ ） to determine production performance, slaughter performance and lactation performance of their offspring. And they were compared with Guizhou local yellow cattle. [ Result ] The growth, slaughter and lactation performance of offspring of F1 Fleckvieh （ ♂ ） × Simmental （ ♂ ） × local yellow cattle （ Q ） proved optimal, followed by offspring of F1 Fleckvieh （ ♂ ） × local yellow cattle （ ♀） and offspring of Guizhou local yellow cattle. [ Conclusion] Offspring of improved local yellow cattle crossbred with Fleckvieh （ ♂ ） and hybridized cattle of Fleckvieh × Simmental × local yellow cattle enjoy significant heterosis and the economic benefits of cattle farming could be significantly enhanced.

Maternal sodium acetate supplementation promotes lactation performance of sows and their offspring growth performance

Milk yield and composition are critical determining factors for the early growth and development of neonates.The objective of this experiment was to comprehensively evaluate the effects of dietary sodium acetate(SA)supplementation on the milk yield and composition of sows and the growth performance of their offspring.A total of 80 sows(Landrace×Yorkshire,3 to 6 parity)were randomly assigned to 2groups(with or without 0.1%SA)from d 85 of gestation to d 21 of lactation.The result shows that maternal 0.1%SA supplementation significantly increased sows milk yield,milk fat,immunoglobulin A(IgA)and IgG content in milk(P<0.05),with the up-regulation of short-chain fatty acids receptors(GPR41 and GPR43)expression and the activation of mammalian target of rapamycin complex C1(mTORC1)signaling pathway.Consistently,in our in vitro experiment,SA also activated m TORC1signaling in porcine mammary epithelial cells(P<0.05).Furthermore,the improvement of milk quality and quantity caused by maternal SA supplementation led to the increase in body weight(BW)and average daily weight gain(ADG)of weaning piglets,with the improvement of gut health and colonization of the beneficial bacteria(P<0.05).In conclusion,maternal supplementation of 0.1%SA improved the lactation performance(milk yield and milk fat)of sows,possibly with the activation of GPR41/GPR43-mTORC1 signaling.Furthermore,enhanced milk quality improved growth performance,gut health and the colonization of beneficial microbial flora of their piglets.

Dietary supplementation of sodium butyrate enhances lactation performance by promoting nutrient digestion and mammary gland development in dairy cows

This experiment was to evaluate the influence of sodium butyrate(SB)addition on milk production,ruminal fermentation,nutrient digestion,and the development and metabolism regulation of the mammary gland in dairy cows.Forty Holstein dairy cows averaging 710±18.5 kg body weight,72.8±3.66 d in milk(DIM),and 41.4±1.42 kg/d milk production were divided into four treatments blocked by DIM and milk production.Treatments were control group,low SB,medium SB,and high SB with 0,100,200 and 300 g/d of SB addition per cow,respectively.The study lasted for 105 d.Production of milk,milk protein and lactose quadratically increased(P<0.05),while fat-corrected milk,energycorrected milk and milk fat yields linearly increased(P<0.05)with increasing SB addition.The digestibility of dietary dry matter,organic matter,and crude protein linearly increased(P<0.05),whereas the digestibility of ether extract,neutral detergent fibre,and acid detergent fibre quadratically increased(P<0.05).Ruminal pH quadratically decreased(P=0.04),while total volatile fatty acids(VFA)quadratically increased(P=0.03)with increasing SB addition.The acetic acid to propionic acid ratio increased(P=0.03)linearly due to the unaltered acetic acid molar percentage and a linear decrease in propionic acid molar percentage.Ruminal enzymatic activity of carboxymethyl-cellulase and a-amylase,populations of total bacteria,total anaerobic fungi,total protozoa,Ruminococcus albus,R.flavefaciens,Butyrivibrio fibrisolvens,Fibrobacter succinogenes,and Ruminobacter amylophilus linearly increased(P<0.05).Blood glucose,urea nitrogen,and non-esterified fatty acids linearly decreased(P<0.05),while total protein concentration linearly increased(P=0.04).Moreover,the addition of SB at 200 g/d promoted(P<0.05)mRNA and protein expression of PPARγ,SREBF1,ACACA,FASN,SCD,CCNA2,CCND1,PCNA,Bcl-2,GPR41,and the ratios of p-Akt/Akt and p-mTOR/mTOR,but decreased(P<0.05)mRNA and protein expressions of Bax,caspase-3,and caspase-9.The results suggest that milk production and milk fat synthesis increased with SB addition by stimulating rumen fermentation,nutrient digestion,gene and protein expressions concerned with milk fat synthesis and mammary gland development.

Dietary supplementation with N-carbamoylglutamate initiated from the prepartum stage improves lactation performance of postpartum dairy cows

The objective of this study was to investigate the effects of supplementing N-carbamoylglutamate(NCG),an Arg enhancer,on amino acid(AA)supply and utilization and productive performance of early-lactating dairy cows.Thirty multiparous Chinese Holstein dairy cows were randomly divided into con-trol(CON,n=15)and NCG(CON diet supplemented with NCG at 20 g/d per cow,n=15)groups at 4 wk before calving.Diets were offered individually in tie-stalls,and NCG was supplemented by top-dress feeding onto total mixed ration for the NCG group.The experiment lasted until wk 10 after calving.Dry matter intake tended to be higher(P=0.06),and yields of milk(P<0.01),milk protein(P<0.01),and milk fat(P<0.01)were higher in the NCG-cows than in the CON-cows.Plasma activities of aspartate aminotransferase(P<0.01),alanine aminotransferase(P=0.03),and plasma level ofβ-hydroxybutyrate(P=0.04)were lower in the NCG-cows than in the CON-cows,whereas plasma glucose(P=0.05)and nitric oxide(NO,P<0.01)concentrations were higher.Coccygeal vein concentrations of Cys(P<0.01),Pro(P<0.01),Tyr(P=0.05),most essential AA except Thr and His(P<0.01),total essential AA(P<0.01),and total AA(P<0.01)were higher in the NCG-cows than in the CON-cows.The arterial supply of all AA was greater in the NCG-cows than in the CON-cows.The NCG-cows had higher mammary plasma flow of AA(P=0.04)and clearance rate of Cys(P<0.01),Pro(P<0.01)and Asp(P<0.01),and higher ratios of uptake to output of Met(P=0.05),Lys(P<0.01),Cys(P=0.01),Pro(P=0.03),and Asp(P=0.01).In summary,addition of NCG initiated from the prepartum period improved the lactation performance of postpartum dairy cows,which might attribute to greater Arg and NO concentrations,as well as improved AA supply and utilization,liver function,and feed intake in these cows.

Regulation of dietary fiber on intestinal microorganisms and its effects on animal health

The animal gut harbors diverse microbes that play an essential role in the well-being of their host.Specific diets,such as those rich in dietary fiber,are vital in disease prevention and treatment because they affect intestinal flora and have a positive impact on the metabolism,immunity,and intestinal function of the host.Dietary fiber can provide energy to colonic epithelial cells,regulate the structure and metabolism of intestinal flora,promote the production of intestinal mucosa,stimulate intestinal motility,improve glycemic and lipid responses,and regulate the digestion and absorption of nutrients,which is mainly attributed to short-chain fatty acids(SCFA),which is the metabolite of dietary fiber.By binding with G protein-coupled receptors(including GPR41,GPR43 and GPR109A)and inhibiting the activity of histone deacetylases,SCFA regulate appetite and glucolipid metabolism,promote the function of the intestinal barrier,alleviate oxidative stress,suppress inflammation,and maintain immune system homeostasis.This paper reviews the physicochemical properties of dietary fiber,the interaction between dietary fiber and intestinal microorganisms,the role of dietary fiber in maintaining intestinal health,and the function of SCFA,the metabolite of dietary fiber,in inhibiting inflammation.Furthermore,we consider the effects of dietary fiber on the intestinal health of pigs,the reproduction and lactation performance of sows,and the growth performance and meat quality of pigs.

Nano-sized zinc addition enhanced mammary zinc translocation without altering health status of dairy cows

This study aimed to evaluate role of nano-sized zinc(Zn)on lactation performance,health status,and mammary permeability of lactating dairy cows.Thirty multiparous dairy cows with similar days in milk(158±43.2)and body weight(694±60.5 kg)were chosen based on parity and milk production and were randomly assigned to 3 treatment groups:basal diet(control,69.6 mg/kg of Zn adequate in Zn requirement),basal diet additional Zn-methionine(Zn-Met,providing 40 mg/kg of Zn),and basal diet additional nano-sized Zn oxide(nZnO,providing 40 mg/kg of Zn).The study lasted for 10 wk,with the first 2 wk as adaptation.Feed intake,milk yield and the related variables,and plasma variables were determined every other week.Blood hematological profiles were determined in the 8 th week of the study.We found that feed intake,milk yield,and milk composition were similar across the 3 groups.The nZnO-and Zn-Met-fed cows had greater milk Zn concentrations in the milk(3.89 mg/L(Zn-Met)and3.93 mg/L(nZnO))and plasma(1.25 mg/L(Zn-Met)and 1.29 mg/L(nZnO))than the control cows(3.79 mg/L in milk and 1.21 mg/L in plasma).The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows.The Zn appearance in milk was greater in nZnO-fed(area under curve during the first 4 h post-feeding for milk Zn:16.1 mg/L)and Zn-Met-fed cows(15.7 mg/L)than in control cows(15.0 mg/L).During the first 4 h post-feeding,milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows.Oxidative stress-related variables in plasma,blood hematological profiles,and mammary permeability related variables were not different across treatments.In summary,lactation performance,Zn concentrations in milk and plasma,hematological profiles,mammary permeability were similar in cows fed nZnO and Zn-Met.We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance,health status,and mammary gland permeability in dairy cows.

Responses of milk production of dairy cows to jugular infusions of a mixture of essential amino acids with or without exclusion leucine or arginine

The purpose of this study was to determine effects of jugular infusion of either balanced or imbalanced amino acid mixture on milk production and composition in dairy cows. Eight mid-lactation Holstein cows were randomly assigned to 5-d continuous jugular infusions of saline(CTL), essential amino acid(EAA) mixture prepared on the profile of casein(CSN, 160 g/d), EAA mixture excluding leucine(Leu)(-Leu, 163 g/d) or EAA mixture excluding arginine(Arg)(-Arg, 158 g/d) in a duplicated 4×4 Latin square design with 4 infusion periods separated by a 7-d interval period. The basal diet was formulated with corn grain, soybean meal, cottonseed meal, corn silage, alfalfa hay and Chinese wildrye grass hay according to NRC(2001) and supplied 1.6 Mcal net energy for lactation(NEL) and 94.4 g metabolizable protein(MP) per kg dry matter(DM) to meet requirements for lactation. The results showed that the dry matter intake(DMI) and normal physiological status were not affected by amino acid mixture infusions.Compared with CTL treatment, the CSN treatment increased milk yield(14.9%, P < 0.001), milk lactose yield(14.5%, P = 0.001), milk fat yield(16.6%, P = 0.01), milk protein yield(18.2%, P < 0.001) and the contents of α_(S1)-casein(α_(S1)-CN,11,8%,P = 0,007),β-casein(β-CN,4.2%.P=0.035) and K-casein(κ-CN,8.5%, P = 0.003). However, the-Leu and-Arg treatments had lower milk yield(6.3%, P = 0.058 and 5.7%,P = 0.073, respectively), milk protein yield(8.8%, P = 0.010 and 8.2%, P = 0.011, respectively) and the contents of α_(S1)-CN(7.3%,P = 0.057 and 8.4%,P = 0.026, respectively),β-CN(4.2%,P = 0.033 and 3.8%,P = 0.048, respectively) and κ-CN(5.8%, P = 0.023 and 7.6%, P = 0.003, respectively) than those of the CSN treatment. Milk lactose yield(5.9%, P = 0.076) tended to decrease when Leu was removed from amino acid mixture infusate. In conclusion, the supply of casein profile can increase milk production in dairy cows, but a deficiency of Leu or Arg had negative effects on milk yield and milk protein yield.