Effects of prolonged intravenous infusions of adrenaline on glucose utilization, plasma metabolites, hormones and milk production in lactating sheep

Lactating ewes received continuous intravenous infusions of adrenaline (0.05 micrograms/kg liveweight) for 4 days. Prior to, during and after adrenaline infusions, milk yield and composition were monitored. Plasma concentrations of metabolites and hormones were measured each day and glucose biokinetics were measured in non-steady state at the start and end of adrenaline infusions. During adrenaline infusion, milk yield and content of solids-not-fat decreased and milk fat content was reduced on the first day of infusion. Plasma glucose was raised throughout the period of adrenaline infusion, plasma lactate increased over the first 4 h from the start of infusion and plasma non-esterified fatty acids increased for 2 h at the start of infusion and tended to increase during the first 2-3 h after withdrawal of adrenaline. Plasma growth hormone remained relatively stable except for a marked increase at 30 min after withdrawal of adrenaline. At the start and immediately after withdrawal of adrenaline infusion plasma insulin was increased approximately twofold. Glucose production, but not utilization, increased at the start of infusions. Immediately after withdrawal of adrenaline glucose utilization increased 2.5-fold with a smaller response in glucose production. There was essentially no change in glucose clearance during adrenaline infusion but a marked increase occurred after withdrawal of adrenaline.     

Effects of restricted nursing on milk production and collection, kid growth and plasma prolactin and growth hormone concentrations in dairy goats

The milk production of dairy goats under various regimes of mother-young contact from day 4 post partum were studied during the first 2 months of lactation, together with the prolactin (PRL) and growth hormone (GH) responses to udder stimulation. In the control group, 13 goats and their kids were left in permanent contact and did not undergo milking. In two additional groups, goats were machine milked once a day in the morning (at 0800 h) and kids were allowed 10 hours (from 1000 to 2000 h; 10H group, n = 11) or 5 h (from 1000 to 2000 h; 5H group, n = 11) of mother-young interaction per day. In the last group (MO, n = 10), mothers were permanently separated from their kids on day 4 post partum and milked once a day. Milk production during a 24-h period at 37 days post partum performed by controlled nursing and weighing of the kids (groups with kids) or by two machine milking 12 h apart (milking only group) revealed a higher production in the three groups with some mother-young contact than in the MO group. Total milk collected by milking over the 2 months of the study did not differ between the three groups that underwent milking. Kid weights at 2 months were 3.4 to 4.8 kg. lighter in the groups that underwent milking than in the control group. Hormonal profiles were significantly affected by restricted mother-young contact, with highest pre-stimulation concentrations of PRL and GH in the 5H group. Restricting mother-young contact from the first week postpartum can permit an early collection of milk without major effects on kid growth, when compared with one daily milking in goats totally separated from their young.     

Effects of exogenous growth hormone on mammary function in lactating goats

The galactopoietic effect of daily injections, for five day periods, of growth hormone was examined by measuring milk yield, mammary blood flow and arteriovenous differences of glucose and amino acids on 12 occasions in four goats. In 10 periods there were marked increases (mean 18.1%) in mammary blood flow (8 statistically significant) and less-marked increases (mean 8.0%) in milk yield (6 statistically significant). On 8 of the occasions on which it was measured the maximum blood plasma growth hormone concentration was increased to more than 8 ng/ml. There were no statistically significant changes in mammary arteriovenous concentration differences of glucose or amino acids in response to growth hormone injections. It is suggested that, contrary to the usual situation in which the rate of mammary blood flow appears to be regulated by the metabolic activity of the gland, the galactopoietic response to growth hormone may be a consequence of elevated blood flow, which increases the supply to the gland of rate-limiting metabolic substrates.     

The effects of intracerebroventricular infusion of prolactin in luteinizing hormone, testosterone and growth hormone secretion in male sheep

This study tested a hypothesis that the enhancement of the prolactin (PRL) concentration within the central nervous system (CNS) disturbs pulsatile luteinizing hormone (LH) and growth hormone (GH) secretion in rams that are in the natural breeding season. A 3h long intracerebroventricular (icv.) infusion of ovine PRL (50 microg/100 microl/h) was made in six rams during the daily period characterized by low PRL secretion in this species (from 12:00 to 15:00 h); the other six animals received control infusions during the same time. Blood samples were collected from 9:00 to 18:00 h at 10 min intervals. A clear daily pattern of LH secretion was shown in control animals, with the lowest concentration at noon and an increasing basal level around the time of sunset (P < 0.001). No significant changes in LH concentration occurred in PRL-infused animals and the concentration noted after infusion of PRL was significantly (P < 0.05) lower than after the control infusion. The frequency of LH pulses tended to decrease in rams after PRL treatment. The changes in LH secretion clearly carried over to the secretion of testosterone in the rams of both groups. The GH concentrations changed throughout the experiment in both groups of rams, being higher after the infusions (P < 0.001). However, the mean GH concentration and GH pulse amplitude noted after PRL infusion were significantly lower (P < 0.001 and P < 0.05, respectively) from those recorded in the control. The continued fall in PRL secretion observed in rams following PRL infusion (P < 0.05 to P < 0.001) indicates a high degree of effectiveness of exogenous PRL at the level of the CNS. In conclusion, maintenance of an elevated PRL concentration within the CNS leads to disturbances in the neuroendocrine mechanisms responsible for pulsatile LH and GH secretion in sexually active rams.     

Impact of fat source and dietary fibers on feed intake,plasma metabolites,litter gain and the yield and composition of milk in sows

Sow lactation diets often include fat sources without considering the impact on digestion, metabolism and performance. Fiber ingredients may reduce feed intake and are often completely excluded from lactation diets, although locally available ingredients may be cost-efficient alternatives to partly replace cereals in lactation diets. Thus, a standard lactation diet low in dietary fiber, and two high-fiber diets based on sugar beet pulp (SBP) or alfalfa meal (ALF) were formulated. The SBP diet was high in soluble non-starch polysaccharides (NSP), whereas ALF being high in insoluble NSP. Each diet was divided in three portions and combined with 3% soybean oil (SOYO), palm fatty acid distillate (PFAD), or glycerol trioctanoate (C8TG) as the dietary fat source. Equal amounts of metabolizable energy were fed to 36 second parity sows from day 105 of gestation and throughout lactation to study the impact on feed intake, plasma metabolites, milk production and litter performance. Backfat thickness and BW of sows were recorded on days 3, 17 and 28 of lactation; blood was sampled on days 3 and 17; milk samples were obtained on days 3, 10, 17 and 24 of lactation; and piglets were weighed on days 2, 7, 14, 21 and 28 of lactation. Litter gain and milk yield during late lactation were greater in sows fed C8TG or SOYO than in sows fed PFAD (P=0.05), whereas loss of BW (P=0.60) and backfat (P=0.70) was unaffected by fat source. Milk protein on days 3 and 10 of lactation were lower in C8TG and SOYO sows, than in PFAD sows (P<0.05). The lowest concentration of plasma lactate on day 3 (P<0.05) and plasma acetate on day 17 (P<0.05) was observed in C8TG sows. Milk yield was unaffected by fiber treatment (P=0.43), whereas milk protein concentration was lowest in ALF sows (P<0.05). Feed intake tended to be lower (P=0.09), and litter gain during the 3^rd week of lactation was decreased (P<0.05) in SBP sows. In conclusion, performance was enhanced in SOYO and C8TG compared with PFAD sows, possibly associated with reduced energy intake in PFAD-fed sows. Furthermore, the SBP diet seemed to impair feed intake and litter gain at peak lactation, suggesting that effects of the dietary fiber fraction on energy intake determines the potential inclusion level of fiber-rich ingredients.     

Variation in blood leucocytes,somatic cell count,yield and composition of milk of crossbred goats

Ten multiparous crossbred goats, five each of alpine × beetal (AB) and saanen × beetal (SB) were selected from the National Dairy Research Institute goat herd immediately after parturition. These were managed as per the practices followed in the institute’s goatherd. Blood and milk samples were collected at biweekly intervals from day 14 post-kidding for 22 weeks (154 days). Somatic cell count, electrical conductivity, fat, protein and lactose contents of milk were determined using standard methods. In the blood samples total leucocytes and differential leucocytes were also determined. Somatic cell counts were high immediately after parturition on day 14 of lactation and declined gradually with advanced lactation. There were individual variations (P < 0.01) in somatic cell counts between different lactation periods. Somatic cell count of milk was negatively correlated with neutrophils only (P < 0.05) and was neither correlated with milk yield, or with fat, protein, lactose content of milk. Electrical conductivity of milk was low up to four weeks of lactation and thereafter increased as the lactation advanced. Lactose content of milk declined gradually with the advancement of lactation. Fat content of milk was stable up to the eighth week and thereafter increased with advancement of lactation while the protein content of milk did not change significantly during lactation.     

Using dried orange pulp in the diet of dairy goats: effects on milk yield and composition and blood parameters of dams and growth performance and carcass quality of kids

Although dried orange pulp (DOP) may conveniently replace cereals in ruminant diets, few studies have considered similar diet substitution for goats. We hypothesised that DOP could replace cereal-based concentrate in goat diets without detrimental effects on growth performance and carcass quality of suckling kids and milk performance and blood biochemical parameters of dams in early lactation. We also hypothesised that DOP substitution may increase the levels of antioxidants, such as phenolic compounds and vitamin E, in milk and improve its total antioxidant capacity (TAC). Therefore, 44 primiparous Payoya dairy goats were allocated to three experimental groups, each fed a different diet: control (CD, n = 14) based on a commercial concentrate with alfalfa hay as forage; and DOP40 (n = 16) in which 40% and DOP80 (n = 14) in which 80% of the cereal in the concentrate were replaced by DOP. The experiment lasted from the final month of pregnancy to 55 days postpartum. The DOP diets did not affect suckling kids’ carcass quality, but at 28 days, led to improvement in live weight (LW) and average daily gain (ADG) from birth, although no differences were found between DOP40 and DOP80 (for CD, DOP40 and DOP80, LW at 28 days was 8.00, 8.58 and 8.34 kg and ADG was 184, 199 and 195 g/day, respectively). Diet had no significant effect on milk yield (average daily milk yield and total yield at 55 days were 1.66 l/day and 90.6 l, respectively) and commercial and fatty acid composition. Nevertheless, α-tocopherol, total phenolic compound (TPC) and TAC concentration in milk increased with substitution of cereals by DOP (for CD, DOP40 and DOP80, concentration of α-tocopherol was 21.7, 32.8 and 42.3 μg/100 g, TPCs was 63.5, 84.1 and 102 mg gallic acid equivalents/l, and TAC was 6.63, 11.1 and 12.8 μmol Trolox equivalents/ml, respectively). Every plasma biochemistry parameter considered was within reference values for healthy goats; therefore, no pathological effect was detected for these variables due to dietary treatment. However, DOP diets caused a reduction in plasmatic creatine kinase and aspartate aminotransferase, implying reduced oxidative damage to muscles. In conclusion, DOP may be an interesting alternative to cereals in early lactation goat diets for increasing farmers’ income and the healthy antioxidant capacity of milk.     

Flight effects on plasma levels of free fatty acids, growth hormone and thyroid hormones in homing pigeons

Significant increases in circulating levels of free fatty acids (FFA) and growth hormone (GH), were observed in homing pigeons after a flight of 48 km, lasting 60-80 min. No significant change in plasma levels of thyroxine (T4) and triiodothyronine (T3) was observed. Nor was there any change in T3/T4 ratio. The increase in plasma FFA is attributed to the increased release into circulation of at least one adipokinetic hormone, GH. It may be concluded that in free sustained homing flight under normal weather conditions and within the specific distance and duration, metabolic fuel and hormonal homeostasis is maintained.     

Artificial induction of lactation in cattle: Effect of modified treatments on milk yield, fertility, and hormones in blood plasma and milk

Holsteins were divided into groups CON and IL, each with six dry cows and six heifers. Group CON calved in mid-summer when group IL was treated (kg body weight per day) with (a) progesterone (P; .25 mg) and estradiol-17beta (Ebeta), either .05 mg or .10 mg, for 7 days; (b) continued Ebeta at one-third the initial rate until udders were engorged; (c) then 12 injections (8-hr intervals) of TRH (each 200 mug) or saline; and (d) GnRH during lactation. Milk yield was not affected by Ebeta dose rate, TRH or GnRH. GnRH luteinized the persistent ovarian follicles in group IL, and pregnancy rates were 80% and 83% in groups IL and CON, respectively. Large differences (P < .01) between groups IL and CON were observed in plasma prolactin (IL-low), insulin (IL-high) and growth hormone (IL-low) wherein insulin was correlated (P < .01) negatively with milk yield between days 7 to 49 of lactation. Milk concentrations of P, Ebeta, estrone and estradiol-17alpha in group IL were no higher (P > .10) 14 days after the last injection of P or Ebeta than in group CON or in milk from the herd's bulk tank. The steroids were lowest in milk and plasma from ovariectomized cows. It was hypothesized that high insulin, as well as low prolactin and growth hormone, may contribute to inferior induced lactations.     

Casein SNP in Norwegian goats: additive and dominance effects on milk composition and quality

Background

The four casein proteins in goat milk are encoded by four closely linked casein loci (CSN1S1, CSN2, CSN1S2 and CSN3) within 250 kb on caprine chromosome 6. A deletion in exon 12 of CSN1S1, so far reported only in Norwegian goats, has been found at high frequency (0.73). Such a high frequency is difficult to explain because the national breeding goal selects against the variant''s effect.

Methods

In this study, 575 goats were genotyped for 38 Single Nucleotide Polymorphisms (SNP) located within the four casein genes. Milk production records of these goats were obtained from the Norwegian Dairy Goat Control. Test-day mixed models with additive and dominance fixed effects of single SNP were fitted in a model including polygenic effects.

Results

Significant additive effects of single SNP within CSN1S1 and CSN3 were found for fat % and protein %, milk yield and milk taste. The allele with the deletion showed additive and dominance effects on protein % and fat %, and overdominance effects on milk quantity (kg) and lactose %. At its current frequency, the observed dominance (overdominance) effects of the deletion allele reduced its substitution effect (and additive genetic variance available for selection) in the population substantially.

Conclusions

The selection pressure of conventional breeding on the allele with the deletion is limited due to the observed dominance (overdominance) effects. Inclusion of molecular information in the national breeding scheme will reduce the frequency of this deletion in the population.     

Effect of administration of live Saccharomyces cerevisiae on milk production,milk composition,blood metabolites,and faecal flora in early lactating dairy goats

The effects of live Saccharomyces cerevisiae (CNCM I-1077) supplementation to 72 Saanen dairy goats in early lactation were investigated. Animals were divided into treatment and control groups balanced for parity and milk production in the first 3 weeks of lactation. Treated animals received 0.2 g/day yeast supplement (Levucell SC20) corresponding to 4 × 10⁹ cfu/day S. cerevisiae, beginning week 3 of lactation, and lasting 15 weeks. Dry matter intake (DMI), body condition score (BCS), milk production and composition were recorded to day126 postpartum. Milk samples were analysed weekly for fat, protein, lactose, urea and SCC. Blood samples were analysed monthly for glucose, BHBA, NEFA, GOT and GGT. Intestinal microflora were assessed monthly in faeces, assaying total bacteria, enterobacteria, E. coli, coliform bacteria, clostridia, lactobacilli, molds and yeast. BCS was not affected by the treatment, but treated animals had greater DMI (2.71 kg/day versus 2.35 kg/day, S.E. ±0.12, P < 0.001) and produced more (P < 0.05) milk (2.38 kg/day versus 2.08 kg/day, S.E. ±0.14) of lower fat content (P < 0.05). Plasma metabolites and liver enzymes (GOT, GGT) were similar between groups, although BHBA levels tended to be lower (P = 0.06) in treated animals. Faecal E. coli were reduced (0.72 log₁₀ cfu/g versus 2.39 log₁₀ cfu/g, S.E. ±0.38, P < 0.05) and lactobacilli increased (P < 0.05) by the treatment. Yeast faecal levels were higher (P < 0.001) in treated animals during supplementation. In this study, live yeast supplementation to early lactating dairy goats significantly increased milk production, in relation to increased DMI, without decreasing BCS. Plasma metabolites (glucose, BHBA and NEFA) were consistent with the BCS findings (no differences between groups) and in addition there was a significant reduction of faecal E. coli content together with increase in lactobacilli in the treated animals, suggesting greater stability of the intestinal ecosystem. Results suggest that the inclusion of Saccharomyces cerevisae in the diet of early lactating dairy goats can be recommended under field conditions.     

Effect of glycerol supplementation during early lactation on milk yield,milk composition,nutrient digestibility and blood metabolites of dairy buffaloes

This study was conducted to evaluate the effect of increasing levels of glycerol in the diet on milk yield and composition, diet digestibility and some blood metabolites of dairy buffaloes in early lactation. A total of 24 buffaloes were blocked by average milk yield, parity and BW and then randomly assigned to three treatments: control without glycerol (CON); low glycerol (LG): control plus glycerol at 150 ml/day per buffalo; and high glycerol (HG): control plus glycerol at 300 ml/day per buffalo. The experimental period lasted for 60 days. Feeding LG and HG decreased (P<0.0001) dry matter intake compared with the CON. Buffaloes supplemented with LG and HG produced more milk (P<0.01) and had a greater (P<0.0001) yield of fat-corrected milk (3.5%) than those buffaloes fed control treatment. Glycerol-supplemented buffaloes showed a positive energy status indicated by reduced concentrations of non-esterified fatty acids and β-hydroxybutyrate. Feeding LG and HG tended to increase (P⩽0.10) concentrations of milk fat, and serum total protein and globulin and significantly decreased (P⩽0.05) milk urea nitrogen and somatic cells counts (SCCs) compared to the CON group. Inclusion of LG and HG had no effect on organic matter and non-fiber carbohydrate digestion, but improved dry matter (P=0.02), CP (P=0.09), ether extract (P=0.03), NDF (P=0.07) and ADF (P=0.03) digestion.     

Relationship between mammary morphology traits and milk yield of Sicilo-Sarde dairy sheep in Tunisia

Sicilo-Sarde is a local breed from northern Tunisia resulting from crossing Sarda and Comisana dairy sheep and is traditionally used for cheese production after lamb weaning. A sample of 52 adult Sicilo-Sarde lactating ewes was used for studying their udder morphological traits and milk yield potential during weeks 4-8 (milking-suckling period) and 10 (milking period) of lactation. Daily milk yield was estimated on a daily basis by using the double oxytocin injection method 4 h after machine-milking at d 30 and 45. Udder and teat morphology were also measured at d 45 of lactation. Cisternal area (by ultrasonography) and udder compartments (cisternal and alveolar milk) were evaluated 8 h after milking by using atosiban and oxytocin on d 72 of lactation. Milk yield averaged 0.56 ± 0.10 L/d and ewes had small (volume, 496 ± 28 mL) and healthy udders (CMT, <1), with medium sized teats (length, 18.5 ± 4.9 mm; diameter, 10.0 ± 2.0 mm) attached at 45 ± 10°. A drop in milk production (49%) was found in the transition from suckling (day 30) to milking (week 10). Udder cisterns were multilocular and small sized (half udder area, 11.6 ± 4.5 cm²), although cisternal milk accounted for 54% of the total milk in the udder. Correlation between cisternal milk and cisternal area was moderate (R² = 0.48; P < 0.05). Lag time and total milking time were 1.9 ± 0.1 and 31 ± 5 s, respectively. In conclusion, the Sicilo-Sarde ewes evaluated showed medium sized cisterns and teats which were morphologically adequate for machine milking, although milk production needs to be improved.     

Rumen-protected conjugated linoleic acid supplementation to dairy cows in late pregnancy and early lactation: effects on milk composition,milk yield,blood metabolites and gene expression in liver

After 27 years with no detected cases, an outbreak of anthrax occurred in a beef cattle herd in the south of Sweden. The outbreak was unusual as it occurred in winter, in animals not exposed to meat-and-bone meal, in a non-endemic country. The affected herd consisted of 90 animals, including calves and young stock. The animals were kept in a barn on deep straw bedding and fed only roughage. Seven animals died during 10 days, with no typical previous clinical signs except fever. The carcasses were reportedly normal in appearance, particularly as regards rigor mortis, bleeding and coagulation of the blood. Subsequently, three more animals died and anthrax was suspected at necropsy and confirmed by culture and PCR on blood samples. The isolated strain was susceptible to tetracycline, ciprofloxacin and ampicillin. Subtyping by MLVA showed the strain to cluster with isolates in the A lineage of Bacillus anthracis. Environmental samples from the holding were all negative except for two soil samples taken from a spot where infected carcasses had been kept until they were picked up for transport. The most likely source of the infection was concluded to be contaminated roughage, although this could not be substantiated by laboratory analysis. The suspected feed was mixed with soil and dust and originated from fields where flooding occurred the previous year, followed by a dry summer with a very low water level in the river allowing for the harvesting on soil usually not exposed. In the early 1900s, animal carcasses are said to have been dumped in this river during anthrax outbreaks and it is most likely that some anthrax spores could remain in the area. The case indicates that untypical cases in non-endemic areas may be missed to a larger extent than previously thought. Field tests allowing a preliminary risk assessment of animal carcasses would be helpful for increased sensitivity of detection and prevention of further exposure to the causative agent.     

Short-term effects of exogenous growth hormone: effects on milk production and utilization of nutrients in muscle and mammary tissues of lactating ewes

Exogenous bovine growth hormone at a dose of 0.1 mg kg-1 liveweight increased yields of milk and milk constituents and milk fat content when injected over 5 days into ewes in mid-lactation. These changes in milk production were associated with changes in the supply to, and utilization of, nutrients by leg muscle and mammary tissues. Arterial concentrations of glucose and non-esterified fatty acids increased significantly, concentrations of lactate and 3-hydroxybutyrate tended to increase, and concentrations of triglycerides associated with very low-density lipoproteins decreased significantly. Growth hormone increased mammary uptake of non-esterified fatty acids, decreased mammary uptake of very low-density lipoproteins and tended to reduce the release of lactate from leg muscle. Oxidation of non-esterified fatty acids in the whole body and mammary tissue was increased by growth hormone and there was a tendency for reduction of glucose oxidation in mammary tissues. During injection of growth hormone, blood flow to leg muscle and mammary tissues increased as did the calculated ratio of blood flow; milk yield. These changes in blood flow, together with changes in arterial concentrations and tissue utilizations of key metabolites, were sufficient to account for the synthesis of extra milk and milk constituents.     

Effects of condensed tannin-amended cassava silage blend diets on feeding behavior,digestibility, nitrogen balance,milk yield and milk composition in dairy goats

Condensed tannins (CTs) are phenolic compounds derived from secondary plant metabolism that act as part of the plant's chemical defense system against pathogen invasion and herbivorous attack. This study aimed to evaluate the intake, digestibility, nitrogen (N) balance, production and composition of milk from goats fed cassava silage with added levels of CTs. Eight Anglo-Nubian goats with a mean BW of 40 ± 2.0 kg were distributed in a double Latin square design with four levels of CTs (0, 25, 50 and 75 g/kg DM) with four 20-day periods with 15 days of adaptation and five evaluation days for each period. No differences were observed in DM, NDF, CP intake and feed conversion (grams of DM intake (DMI) per gram of milk produced); however, when expressed as percent of BW, DMI showed a quadratic increase to 29.1 g/kg. As the level of supplemented CTs increased in the diet, the CP digestibility (P = 0.023), NDF (P = 0.044), non-fiber carbohydrates (NFC; P = 0.032) and total digestible nutrients (P = 0.033) exhibited a linear decrease. Furthermore, the addition of CTs to cassava silage induced a linear increase in N-fecal excretion (P = 0.014) and a positive quadratic effect on N-retained (P = 0.014) and N-balance (P = 0.024) as well as a positive quadratic trend in N-digested (P = 0.092). Milk urea N (P = 0.023) decreased linearly. The addition of CTs to cassava silage had a positive quadratic effect on ruminating time (P = 0.011). In addition, comparing the use or non-use from the orthogonal contrast test, the inclusion of CTs in goat diet increased water and N-intake, CP and NDF digestibility, spent time eating and ruminating and N-balance and decreased milk production corrected^3.5%, fat milk content, milk urea N and dry defatted extract of milk. Thus, adding CTs to cassava silage at 25 g/kg total DM promoted goats' greater use of the diet without impairing feed conversion and the quality of goat milk produced. Dietary levels of 50 and 75 g/kg total DM are not recommended because under the conditions of this study, they reduced the productive efficiency of dairy goats.     

Responses of milk protein,arterial AA concentration,and mammary AA metabolism to graded abomasal casein infusion in lactating goats

It has been generally assumed in postruminal protein or AA infusion studies that casein or AA mixtures mimicking the essential AA (EAA) composition of milk approach ‘ideal protein’ status, but the differences in postabsorptive metabolism of individual EAA may bring the assumption into question. Graded amounts of caseinate sodium were abomasally infused into lactating goats, and concentrations in the plasma of carotid, mammary uptakes and utilization efficiencies of amino acids were monitored in the present study. The results indicated that arterial concentrations of all the amino acids, except for Arg were increased with the increase of caseinate sodium infused (P < 0.05). The increments in plasma concentration differed with individual EAA. Concentrations of Ile, Leu, and Lys increased about two-folds, and that of Met, Thr, Phe, and His increased 58.33, 32.5, 29.87, and 61.66%, respectively, when data of the 99 g/day and the control treatment was compared. Mammary extraction efficiencies of Arg, Thr, Lys, Leu, and Phe increased with graded casein infusion (P < 0.05), while those of the other EAA were not significantly changed (P > 0.05). Mammary extraction efficiencies of individual non-essential amino acids (NEAA) varied greatly, and ranged from 9.18 to 33.89% in the control treatment. Except for Pro, mammary extraction efficiency of NEAA increased with graded casein infusion. Mammary uptake to milk output ratios (U/O) of sequestered AA was generally increased with the increase of casein infused, but that of Thr, His, and Ala was not insignificantly changed (P > 0.05). Compared with the data of previous researchers, the U/O of Thr recorded in the present study was much lower (<0.42). We speculate that Thr may be extracted in forms other than FAA (such as peptide bond AA) by the mammary under conditions of the present study. Consistent with the results of other authors, mammary uptake of Arg was two times more than milk output even in the control treatment, which suggests that there may be a requirement of Arg other than milk protein synthesis in the mammary.