Administration Of Recombinant Bovine Somatotropin Research Articles

Impact of Recombinant Bovine Somatotropin on Bovine Milk Composition and Fatty Acidome: A Multidose Longitudinal Study.

Somatotropin is a species-specific polypeptide hormone produced in the pituitary gland of vertebrates. When administered exogenously to cattle, it can increase milk yield. However, the trade and administration of recombinant bovine somatotropin (rbST) to farm animals have been banned in the European Union (EU). Aside from food safety issues, very little is known about the effects of this hormone on milk composition and quality. In this work, a wide profile of fatty acids (the so-called fatty acidome) was determined by GC-FID in raw milk collected from control and rbST-treated lactating cows in a multidose longitudinal study. Milk composition (lactose, protein, fat, dry matter), including minerals (Ca, K, Mg, Na, P), was also determined, and milk yield was recorded. A tendency toward a less saturated profile was observed in the milk collected from animals treated with rbST, with higher concentrations of monounsaturated fatty acids. In addition, less calcium and potassium and more lactose and protein content were observed in milk from treated animals than in regular milk. As a result of this multicomponent profiling of milk, a clear impact of somatotropin treatment on milk quality was observed. The obtained results should be particularly interesting for those countries that permit the use of this hormone in dairy production.

Recombinant bovine somatotropin in the synchronization of ovulation in crossbred dairy cows (Bos taurus indicus × Bos taurus taurus).

Aim:The aim of this study was to evaluate the effects of the administration of recombinant bovine somatotropin (rbST) at the moment of implementation of the timed artificial insemination protocol, on follicular dynamics and pregnancy rate in crossbred cows.Materials and Methods:A total of 346 cows were used in two experiments with a factorial 2×2 design. The cycling cows (Tcycling) and the anestrous cows (Tanestrous) were considered as factor 1 and the administration of rbST (TrbST) or not (Tcontrol) as factor 2. The experimental protocol: (1) Tcontrol – day 0 (D0), insertion of a progesterone-release intravaginal device (PRID) plus 2 mg of estradiol benzoate (EB); D8, PRID removal, plus 0.150 mg of prostaglandin F2α, and 400 IU of equine chorionic gonadotropin; D9, 1 mg of EB; and with artificial insemination at day 10; (2) TrbST – similar to Tcontrol plus 500 mg of rbST on D0. In experiment I, ultrasound examinations were performed in all treatments. In experiment II, the cows’ pregnancy rate was evaluated. Data were analyzed with 5% probability.Results:There was no effect of the protocols on cows cyclicity or follicular growth rate (p>0.05). There was no interaction of the effects, administration of rbST, and the cyclicity of cows on the pregnancy rate. The total pregnancy rate observed was 49.0%. The pregnancy rate in cows receiving rbST was lower for anestrous compared with cycling cows (p<0.05).Conclusion:The administration of rbST did not alter the patterns of follicular dynamics nor the ovulation rate. However, cows in anestrous that received rbST had lower pregnancy rates than cycling cows.

Effect of growth hormone on milk yield and reproductive performance of subfertile Holstein cows during extended lactations

The objective of this study was to determine the effects of the administration of recombinant bovine somatotropin (rbST) throughout lactation to high-yielding subfertile (conception &gt; 270 days postpartum) Holstein cows undergoing extended lactations (≥480 d) on milk production and reproductive performance. The study used two large adjacent commercial herds with similar management in a hot area of northern Mexico (25° N). Cows in one herd (n=2341) received a 500-mg dose of rbST every 14 d until dried off, starting 60 days postpartum. The other herd served as control (n=984). Across parity, rbST-treated cows produced 20% greater milk yield than control cows in 305-d lactations. Across parities, milk yield from 305 d postpartum to the end of lactation was 2734 kg higher in rbST-treated cows than control cows. Across parities rbST-treated cows produced 4777 more kg of milk during the entire lactation (mean 605 d) than the control group (mean 572 d). Conception rates (CR) at first service were only 3.2% and 5.9% (p&lt;0.05) for control and rbST-treated cows, respectively. Overall CR was 43.5% and 61.6% (p&lt;0.05) for control and treated cows, respectively. Control cows required 2.4 more (p&lt;0.01) services per conception than rbST-treated cows. It was concluded that in this hot environment, the use of rbST suits dairy producers because it substantially improves both milk yield and reproductive performance in subfertile high-yielding Holstein cows. By markedly increasing lactation length and lactation persistency farm efficiency is greatly improved due to extended herd life.

PSI-5 Biweekly administration of recombinant bovine somatotropin during the first trimester of pregnancy failed to alter uterine hemodynamics in suckled beef cows.

PSI-5 Biweekly administration of recombinant bovine somatotropin during the first trimester of pregnancy failed to alter uterine hemodynamics in suckled beef cows.

Administration of recombinant bovine somatotropin prior to fixed-time artificial insemination and the effects on fertility, embryo, and fetal size in beef heifers

Our objectives were to determine the effects of the administration of recombinant bovine somatotropin (bST) at the initiation of a fixed-time AI (TAI) protocol on concentrations of plasma IGF-1, follicle diameter, embryo/fetal size, and pregnancy rates in replacement beef heifers. Four hundred and fourteen Angus-based beef heifers were enrolled in a completely randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) protocol where they received a 100-µg injection of GnRH and a CIDR insert on day -9, 25 mg of PGF2α at CIDR removal on day -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on day 0. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) heifers that received 650 mg of bST on day -9 (BST; n = 191); or 2) heifers that did not receive bST on day -9 (CONTROL; n = 223). Blood samples were collected on day -9, 0, 28, and 60 to determine the plasma concentrations of IGF-1. Follicle diameter was determined on day -2 and 0 by transrectal ultrasonography. Pregnancy was diagnosed via transrectal ultrasonography on day 28 or 35, and again at least 30 d after the end of the breeding season. Embryo morphometry was assessed by measuring crown-to-rump length (CRL) on day 28, and fetal size was assessed by measuring crown-to-nose-length (CNL) on day 60. Concentrations of plasma IGF-1 did not differ between treatments on day -9 (P = 0.924), 28 (P = 0.075), and 60 (P = 0.792); however, concentrations of plasma IGF-1 were greater (P < 0.001) in BST-treated heifers at TAI (372.4 ± 16.6 vs. 193.7 ± 16.6 ng/ml). No differences (P = 0.191) were detected for follicle diameter between CONTROL and BST treatments on day -2 or 0. Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) for CONTROL compared to BST heifers (42.5 ± 4.0 vs. 29.9 ± 4.1%). No differences (P = 0.536) in CRL were observed on day 28 between CONTROL and BST heifers. In addition, no difference (P = 0.890) was observed for CNL between CONTROL and BST treatments. Final pregnancy rates did not differ (P = 0.699) between treatments. The administration of bST to beef heifers at the initiation of a TAI protocol increased plasma concentrations of IGF-1 at TAI; however, failed to enhance follicle diameter, embryo/fetal size, and reduced PR/AI.

105 Effects of biweekly administration of recombinant bovine somatotropin on steroid metabolizing enzymes during early gestation

105 Effects of biweekly administration of recombinant bovine somatotropin on steroid metabolizing enzymes during early gestation

320 The effects of biweekly administration of recombinant bovine somatotropin during the first trimester on fetal development in gestating beef heifers

320 The effects of biweekly administration of recombinant bovine somatotropin during the first trimester on fetal development in gestating beef heifers

Effects of recombinant bovine somatotropin administration at breeding on cow, conceptus, and subsequent offspring performance of beef cattle.

The effects of administration of recombinant bovine ST (bST) on plasma hormone concentrations of cows, conceptus development, and postnatal calf performance were examined. Lactating beef cows ( = 190) were exposed to a fixed-time AI (TAI) protocol from d -10 to 0 (TAI on d 0). Cows were blocked by breed and stratified by days postpartum and then randomly assigned to receive, subcutaneously 1) 2 injections of saline (1 mL of 0.9% saline), 1 on d 0 at TAI and a second injection on d 14 (CTRL; = 53); 2) an injection of 325 mg of bST on d 0 and a saline injection on d 14 (bST0; = 48); 3) a saline injection on d 0 and an injection of 325 mg of bST on d 14 (bST14; = 49); or 4) 2 injections of 325 mg of bST, 1 on d 0 and a second injection on d 14 (bST0+14; = 40). Pregnancy status, crown-to-rump length (CRL) on Day 35, and crown-to-nose length (CNL) on Day 65 were determined via transrectal ultrasonography. Blood samples were collected on d 0, 7, 14, 21, 35, and 65, relative to TAI, to determine plasma concentrations of progesterone (P4), IGF-1, and pregnancy-specific protein B (PSPB) and also on d 18 and 21 for isolation of peripheral blood leukocytes for RNA extraction and measurement of interferon-stimulated genes transcript abundance. Individual calf BW was determined at birth and every 30 d until weaning. A subset of 24 calves was randomly selected for liver biopsies at birth to determine mRNA expression of target genes. Administration of bST to cows increased ( < 0.0001) concentrations of plasma IGF-1 for 14 d after injection compared with CTRL but did not affect fetal CRL and CNL ( = 0.23). Cows receiving bST only on d 0 had a greater ( = 0.05) transcript abundance in myxovirus resistance 2 on d 21 compared with 2bST cows (2.0- and 0.8-fold for bST0 and 2bST, respectively), whereas cows receiving bST14 and CTRL were intermediate (1.2- and 0.9-fold, respectively). Calf BW did not differ ( ≥ 0.100) among treatments on d 0, 30, 60, 90, 120, and 150 relative to birth. Injection of bST only on d 0 tended ( = 0.062) to increase calf liver mRNA expression of at birth compared with the calves born to cows in other treatments. Therefore, during a TAI protocol, the administration of 1 or 2 injections of 325 mg of bST to lactating beef cows enhanced their plasma concentrations of IGF-1 but failed to improve fetal size and plasma concentrations of maternal PSPB and P4 and had no effect on postnatal calf growth performance.

Effect of administration of recombinant bovine somatotropin on health and performance of lactating dairy cows diagnosed with hyperketonemia

The effect of administering recombinant bovine somatotropin (rbST) to cows with hyperketonemia during the early postpartum period on health, metabolic parameters, milk production, and early reproductive performance was evaluated in a double-blinded clinical trial. Cows from 8 dairy herds in New York State were tested weekly between 3 and 16d in milk for elevated serum β-hydroxybutyrate. Cows were enrolled in the study when blood β-hydroxybutyrate was ≥1.3mmol/L for the first time. Enrolled cows were randomly assigned to a treatment (n=273) or placebo control (n=270) group. Treated cows were given 325mg of rbST subcutaneously on the day of enrollment and again 14d later. Control cows received the same regimen except the syringe contained only the carrier without somatotropin. After enrollment, blood samples were collected weekly for 4wk and submitted to the laboratory to be analyzed for selected metabolites. Risk ratios for clinical diseases subsequent to treatment were calculated using Poisson regression. Continuous data were analyzed using linear mixed models. Time to first insemination was assessed with survival analysis. In the 42d following the first administration of rbST, incidence risks of displaced abomasum, clinical ketosis, metritis, clinical mastitis, and lameness were not different between treatment groups. Cows treated with rbST had a slightly lower body condition score 28d after enrollment compared with control cows. In the 4wk following enrollment, serum nonesterified fatty acids and aspartate amino-transferase were slightly higher for treated than control cows, respectively. Serum glucose, calcium, haptoglobin, and β-hydroxybutyrate were similar between groups. Treatment had no effect on resolution of hyperketonemia in any of the 4wk after enrollment. Milk production in either of the 2-wk periods after each treatment was not different between treated and control cows. Furthermore, milk production was not different between groups from enrollment to 98d in milk (42.6±0.6 and 42.1±0.7kg/d for treatment and control groups, respectively). Treatment had no effect on time to first insemination (83 and 74d in milk for treatment and control groups, respectively; hazard ratio=0.72) or first insemination pregnancy risk (27 and 29% for treatment and control groups, respectively; risk ratio=0.92). Based on the current results, it is not recommended to use a low dose of rbST as therapy for cows with hyperketonemia.

Prepartum administration of recombinant bovine somatotropin (rBST) on adaptation to subclinical ketosis of the ewes and performance of the lambs

The aim of this study was to determine the effect of prepartum rbST injection on the metabolic profile of pregnant ewes induced to subclinical ketosis, as well as the metabolism until seven days of life and weight gain until seven weeks of life of the lambs. Twenty seven pregnant ewes of the pantaneiro genetic group were used, divided into two groups: rbST group (n = 14) and control group (n = 13). The rbST group received two applications of 1 mg/kg of rbST, at 97 and 111 days gestation, while the control group received placebo injections. There were significant differences between groups in levels of GGT in the ketosis post induction period and BHB concentrations in the postpartum period. Concentrations of glucose, urea, phosphorus, albumin, cholesterol, AST, NEFA and insulin were not different between dams from the two groups in different periods of the study (P&gt;0.05). There was an effect of rbST on body weight observed already at fourteen days of life (P&lt;0.0001), there was an increase in serum phosphorus levels at birth of lambs (P=0.0014), and albumin at seven days of life (P = 0.0014) of the lambs, with no difference between groups for the other metabolites. Therefore, the use of rbST was effective in increasing the weight of the lambs until the seventh week of life. In addition, rbST treatment had positive effects on the dam metabolism with reduction of liver overload, as indicated by decreased GGT after ketosis induction and decreased BHB at the postpartum period.

Effect of prepartum administration of recombinant bovine somatotropin on health and performance of lactating dairy cows

A double-blind, randomized clinical trial was conducted in 5 commercial dairy herds in southern Ontario with 1,362 cows enrolled to evaluate the effect of prepartum administration of recombinant bovine somatotropin (rbST) on health and performance. Cows were randomly assigned to receive either 325mg of sometribove zinc suspension (n=680) or a placebo injection (n=682; control) subcutaneously every 14 d until calving. Treatments started 28 to 22 d before expected calving, with a maximum of 3 treatments per cow. Serum samples taken at the time of enrollment, 1 wk before calving, and weekly for 3 wk after calving were analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, aspartate aminotransferase, calcium, and haptoglobin. Diseases were recorded by farm staff. Incidences of clinical ketosis, clinical mastitis, displaced abomasum, metritis, retained placenta, milk fever, and lameness were similar between groups. Body condition score was lower for treated than for control cows at 3 wk after calving (3.13 and 3.17, respectively). Serum NEFA tended to be higher for treated than for control cows by 0.01mmol/L. Overall BHBA was not different between groups, but BHBA for treated cows was higher in wk 1 after calving (750 and 698μmol/L, respectively) and tended to be higher in wk 2 after calving (779 and 735μmol/L, respectively). Incidence of hyperketonemia was similar between groups. Treated cows had higher serum glucose compared with control cows (2.8 and 2.7mmol/L, respectively). We detected no differences in serum aspartate aminotransferase, calcium, or haptoglobin between groups. Milk yield was recorded daily for each cow for 63 d, and did not differ between groups (37.1±0.5kg and 36.7±0.5kg, respectively) but we detected a tendency for treated cows to produce 0.8kg/d more milk than control cows in wk 1 after calving. We observed no difference between groups in the time from calving to first insemination or the probability of pregnancy at the first insemination. Groups did not differ in the proportion of anovular cows at 53±3 d in milk based on serum progesterone measured from a subset of cows (38.0 and 34.3%, respectively, for treated and control groups). We found no difference between groups in dry matter intake from 21 d before calving to 63 d after calving in a subset of cows (17.4±0.4 and 17.5±0.4kg/d, respectively). Based on results of the current study, biweekly (every 14 d) administration of rbST before calving to prevent disease and enhance performance is not recommended.

Somatotropina bovina recombinante en sincronización de estros y prolificidad de ovejas Pelibuey

In this study it was investigated whether the effect of administration of Recombinant Bovine Somatotropin (bST) (two days before the end of progestin treatment) on synchronizing estrus, estrus, fertility, prolificacy and mode of delivery in Pelibuey sheep. It was an inserted a intravaginal device impregnated with progesterone (P4 CIDR 0.3 g) for nine days on180 sheep with 4 ± 0.32 years of age, the sheep were randomly assigned to one of three treatments: T1= CIDR (n= 60), T2= +250 mg of bST CIDR (n= 60) and T3= CIDR+300 48 IU eCG hours before the end of progestin (n= 60). Results showed no difference (p>0.05) between treatments in estrus synchronization response, fertility and prolificacy. The time to onset of estrus was lower (p<0.05) when applying bST (31.95 ± 2.85 h), with respect to the application of progesterone (43.67 ± 3.55 h). The number of ewes with triplets was higher (p<0.05) when applying bST (32.73 %) and less where it was applied eCG (13.47 %). The administration of 250 mg of bST in Pelibuey sheep, two days before the end of progestin, reduces the time to onset of estrus and increases the proportion of triplets.

AVALIAÇÃO DA SOMATOTROPINA BOVINA RECOMBINANTE (rbST) NOS NÃO-COMPONENTES DA CARCAÇA DE CABRITOS DE TRÊS GENÓTIPOS

This study was developed with the aim of evaluatingrecombinant bovine somatotropin (rbST) on non-carcasscomponents of goat kids of three genotypes. It was used23 male goat kids of three genotypes, being 8 Alpine, 4 ½Boer + ½ Alpine (½ BA) and 11 ¾ Boer + ¼Alpine (¾BA), from which 12 received rbST e 11 control. Thegrowth hormone used was the recombinant bovinesomatotropin (rbST) and animals of treatment 1 receivedthe hormone in the amount of 0.3 mg/kg live weight, from 45 days, adjusted in intervals of 14 days. Animals oftreatment 2 (control) received saline solution in the samedosage and interval. The ½ BA goats presented a higherproportion of external non-carcass components (head, feetand skin) in relation to Alpine goats. Regarding the vitalorgans, such as lungs, kidneys and spleen, and the noncarcasscomponents blood, internal fat and perinephric fat,Alpine goats presented higher values than ¾ BA goats.The administration of recombinant bovine somatotropin (rbST) did not produce effect on proportions and weight of non-carcass components. Proportions and weight of non-carcass components varied in function of genotypes, although animals were slaughtered at similar live weight. KEYWORDS: carcass; goats; growth hormone; live weight components.

Effect of dietary energy intake and somatotropin administration after weaning on growth rate and semen characteristics of Granadina goat bucks

Twenty-eight growing Granadina goat bucks, divided into 4 groups of 7, in a 2 × 2 factorial arranged design, were used to study the effect of post-weaning levels of dietary energy and administration of recombinant bovine somatotropin (rbST) on growth and semen characteristics. Every 14 days, bucks were offered sustenance at rates of either 1.0 (standard diet, 2.36 Mcal EM kg^{-1}; 15% CP) or 1.25 (increased diet, 2.95 Mcal EM kg^{-1}; 18% CP) times the requirements for growth energy and protein, for a total of 99 days and in combination with or without subcutaneous administration of 125 mg rbST. The average daily gains (ADG) were greater (P < 0.01) in bucks fed the high energy diet (133 ± 25 vs. 111 ± 23 g day^{-1}) and the ADG were greater (P < 0.05) in the bucks treated with rbST than in the untreated bucks (130 ± 28 vs. 114 ± 23 g day^{-1}). The percentage of live sperm cells was not different between bucks fed increased diet of NRC recommendations and bucks fed standard diet. Similarly, the sperm output of bucks on the increased diet did not differ from that of bucks on the standard diet (2282 ± 1137 vs. 1946 ± 529 × 10^6/mL). Semen volume (0.51 ± 0.29 vs. 0.55 ± 0.28 mL), sperm concentration (2210 ± 1139 vs. 2055 ± 656 × 10^6/mL), total sperm cells (1233 ± 962 vs. 1014 ± 572 ×x 10^6), and motile sperm cells (67.1 ± 14.5 vs. 60.9 ± 19.3) were not affected by rbST. No significant differences due to dietary and hormonal treatments were observed in scrotal circumference. Dietary and hormonal treatments had no effect on either serum concentration of particular metabolites, except cholesterol. Results from this study indicate that both high energy diets and chronic application of rbST enhanced the growth performance of young Granadina goat bucks; nevertheless, none of these effects altered the final scrotal circumference, particular blood metabolites, and sperm output.

Administration of recombinant bovine somatotropin (rbST) at the time of breeding in superovulated fertile and subfertile ewes

Two experiments were conducted to evaluate the effects of the administration of 125mg rbST at the time of breeding on fertile and subfertile superovulated ewes – in terms of the ovulation rate, embryo yield and embryonic development. In addition, the effects of the treatment on the plasma progesterone concentrations and interferon-tau (IFNT) expression in the embryos were evaluated in the fertile animals. In the first experiment, carried out on fertile superovulated ewes, the treatment significantly increased the ovulation rate (p<0.05) and shifted the embryo distribution towards more advanced stages of development (p<0.01). Plasma progesterone concentrations increased faster in the treated ewes, being significantly different (p<0.05) between groups at day 6 post-breeding. In the second experiment, embryonic development was more advanced in fertile, but not in subfertile superovulated ewes. The expression of IFNT was significantly (p<0.01) decreased in blastocyst embryos obtained from rbST treated animals, compared with non-treated ewes. It is concluded that the administration of rbST to subfertile ewes at the time of breeding does not stimulate embryonic development as it does when administered to fertile animals.

Development of a flow cytometric immunoassay for recombinant bovine somatotropin‐induced antibodies in serum of dairy cows

Administration of recombinant bovine somatotropin (rbST) to enhance milk production in dairy cows is banned within the European Union. Therefore, methods for pinpointing rbST abuse are required. Due to the problematic detection of rbST itself in serum, methods are also focused on detecting changes in rbST-related biomarkers. In this study, a fast and easy-to-perform microsphere-based flow cytometric immunoassay (FCIA) for detection of rbST-induced antibodies in serum was developed. Until now, detection of rbST-induced antibodies was also problematic due to non-specific binding of serum proteins resulting in a high rate of false positive results. Therefore, five different sample preparation methods, i.e. dilution, octanoic acid precipitation, filtration, protein G purification, and a previously described generic FCIA sample preparation were critically compared to overcome non-specific binding to the microspheres. Only the generic FCIA sample pretreatment was effective in reducing non-specific binding. As a result, an absolute decision level for detecting rbST antibodies in serum of dairy cows was determined and its applicability was demonstrated. In accordance with biological expectations from literature, rbST antibodies were induced in three out of four rbST-treated dairy cows. These rbST-induced antibodies were successfully detected for up to 4 weeks after the last rbST treatment, whereas no false positive results were obtained for 27 untreated dairy cows. This is the first method, able to overcome the interference of serum proteins and therefore, can be applied with high confidence for screening unknown herds of cattle for rbST antibodies, an important biomarker for pinpointing at rbST abuse in cattle.

Milk production and hormonal changes in Murrah Buffaloes administered recombinant Bovine Somatotropin (rBST)

Investigation was carried out to determine the influence of short term administration of recombinant bovine somatotropin (rBST) on plasma growth hormone (GH), Insulin like growth factor–I (IGF-I), prolactin (PRL) and milk production of buffaloes in early lactation. Experimental buffaloes received i.v. rBST infusion in jugular vein @ 5mg/hr. i.v. for 5 days, while control group was given placebo injection. Blood samples were collected for 5 consecutive days before, during and after treatment and plasma GH, IGF-I and PRL levels were measured. Administration of rBST increased plasma GH (P<0.01) and IGF-I (P<0.01) concentration simulating to increased milk yield (P<0.01). Milk IGF-I concentration was more after cessation of treatment (P<0.05) than before and during the treatment period. The milk yield increased by 29.9% during the experiment (P<0.01) in comparison to control. rBST treatment influenced milk protein (P<0.01) and lactose (P<0.01) without affecting plasma glucose and NEFA, milk NEFA, citric acid and fat content. There was no adverse effect of rBST on mammary health and plasma prolactin concentration. The positive correlation of GH and IGF-I with milk yield indicated a galactopoietic effect of both the hormones to augment milk production in buffaloes.

Effects of long‐term exogenous bovine somatotropin on glucose metabolism and the utilization of glucose by the mammary gland in different stages of lactation of crossbred Holstein cattle

ABSTRACTThe effects of long‐term administration of recombinant bovine somatotropin (rbST) on glucose turnover and the utilization of glucose in the mammary gland using a continuous infusion of [3‐3H]glucose and [U‐14C]glucose in lactating crossbred Holstein Friesian(HF) cattle were investigated. Glucose turnover of rbST‐treated animals was significantly higher than those of control animals (P &lt; 0.05) in mid lactation, while plasma glucose concentrations were not affected. The utilization of glucose of non‐mammary tissues of rbST‐treated animals significantly increased (P &lt; 0.05) as lactation advanced. The glucose taken up by the mammary gland in early lactation increased flux through the lactose synthesis and the pentose cycle pathway with significant increases in NADPH formation for fatty acid synthesis during rbST administration. The utilization of glucose carbon incorporation into milk appeared to increase in milk citrate and milk triacylglycerol but not for milk lactose as lactation advances in rbST‐treated animals. The stimulant effect for milk yield by rbST treatment was transiently and significantly increased in early lactation and was decreased in late lactation even though there was a high level of udder blood flow. These findings demonstrate that the regulation of biosynthetic capacity within the mammary gland would be influenced more by local than by systemic factors. The proportion of glucose would be metabolized less for lactose synthesis, but metabolized more via the Embden‐Meyerhof pathway and the tricarboxylic acid cycle as lactation advances.

Effects of long‐term administration of recombinant bovine somatotropin on the concentration of metabolites in milk in different stages of lactation in crossbred Holstein cattle

ABSTRACTEffects of long‐term treatment with recombinant bovine somatotropin (rbST) on concentrations of cellular metabolites in the milk of 87.5% crossbred Holstein cattle were performed. The peak milk yield of rbST‐treated animals was 22% higher (P &lt; 0.05) than that of the control animals in early lactation. The mammary glucose uptake of rbST‐treated animals increased in early lactation, but decreased in mid and late lactation, while plasma glucose concentrations were not affected. Lactose and milk triacylglycerol secretion of rbST‐treated animals significantly increased (P &lt; 0.05) when compared with those of control animals in early lactation. The concentrations of milk glucose of rbST‐treated animals significantly increased in early and mid‐lactation (P &lt; 0.05). The concentrations of milk galactose markedly increased (P &lt; 0.05) whereas the concentrations of milk uridine 5′‐diphosphoglucose (UDP‐glucose) and UDP‐galactose showed no significant changes as lactation advances in both groups. The concentrations of isocitrate, 2‐oxoglutarate and citrate in milk from both groups showed no significant changes throughout experiment. The concentration of glucose‐6‐phosphate (G6P), glucose‐1‐phosphate and cyclic adenosine 3,5′monophosphate in milk from both groups markedly decreased as lactation advances exception in early lactation of rbST‐treated animals, which G6P was not affected. These findings suggest that prolonged rbST treatment exerts its galactopoietic action at least in early lactation through both intramammary and extra‐mammary changes. Increases in the concentrations of glucose and G6P in milk maintained the level of pretreatment in early lactation associated with increases in milk yields during rbST administration, reflect their concentrations in the cytosol or Golgi vesicles of mammary cells, which would be one of the factors regulating intermediary metabolites in the lactose biosynthetic pathway.

Use of computer simulation to teach a systems approach to metabolism

Use of a systems approach, as embodied in the computer simulation model of metabolism of a dairy cow, Molly (Baldwin, 2005), is ideal for teaching nutrition. This approach allows the overall complexity of the comprehensive system to be broken down into smaller manageable subunits that are easier to visualize. Quantitative interactions among nutrients supplied and metabolic production processes can be observed over extended time periods. Using Molly, undergraduate animal science students are able to observe detailed effects of changing dietary inputs, altering genetic milk production potential, and exogenously manipulating metabolism on metabolism of the whole cow. This paper demonstrates how Molly is used in the classroom to teach a systems approach to nutrition using example simulations. Three simulation examples demonstrate exercises examining effects of recombinant bovine somatotropin administration, dietary protein, and amino acid supplementation and nitrogen efficiency on milk production and cow metabolism. These and similar examples have been used to teach nutrition, metabolism, and lactation to undergraduate students for the past 20 yr.