Lactation performance, feed efficiency, and blood metabolites of dairy cows treated with recombinant bovine somatotropin: A systematic review and meta-analysis

A systematic review and meta-analysis were conducted to assess the impact of recombinant bovine somatotropin (rbST) on lactation performance, feed efficiency, and blood metabolites in dairy cows. In the systematic review, articles were selected based on the following criteria: (1) Data focusing on the influence of bovine somatotropin doses on milk production; (2) Submission of original data; (3) Articles published in journals; and (4) Articles in English or Portuguese. The analysis of variance was used with a completely randomized design and mixed models methodology. Polynomial regression was applied to significant fixed effects (rbST dose). The use of rbST resulted in increased milk yield and 4% fat-corrected milk yield, while fat, protein, and lactose contents remained unaffected. Dry matter and metabolizable energy intakes, as well as milk/feed efficiency, exhibited a linear increase, but body condition score (BCS) was negatively impacted. The administration of rbST led to higher blood concentrations of triglycerides and insulin. Cows treated with rbST showed a 23% increase in non-esterified fatty acid (NEFA) concentrations compared to non-treated cows. Additionally, growth factors IGF-1 and IGF-2 displayed a linear increase with rbST treatment. In summary, rbST administration increased milk yield and fat-corrected milk yield without affecting milk components. However, despite increasing intake, it resulted in BCS losses and alterations in blood parameters such as NEFA, IGF-1, and IGF-2.

Effects of bovine somatotropin on productive performance and Minas Padrão cheese

We aimed to evaluate the effects of two brands of bST (bovine somatoropin) on productive performance and on Minas Padrão cheese yield. Fifteen Girolando cows with more than 60 days of lactation were used. The animals were distributed in a randomized block design, according to days in milk, with three treatments (somatotropin A, somatotropin B, and control). The animals received a balanced diet with commercial concentrate and corn silage as roughage. It was measured milk yield and composition, dry matter intake, body condition score (BCS), and feeding behavior; it was compared by Tukey at 5.0% of significance level. Physical-chemical composition of Minas Padrão cheese was obtained from the different treatments, was also measured, being evaluated in a completely randomized design, and compared by Tukey at 1.0% of significance level. The dry matter intake per body weight lower in control treatment (p < 0.05) was equal to 2.85, somatotropin A was equal to 3.17, and somatotropin B was equal to 3.17. Animals that received bST showed higher milk production (p < 0.05), with control being 17.56 kg/day, somatotropin A 21.12 kg/day, and somatotropin B 20.69 kg/day. The physical-chemical composition of milk showed significant differences (p < 0.05) for the fat, protein, and dry extract contents. The somatotropin applications also influenced the BCS (p < 0.05) and the feeding behavior in time for total intake, time spent with rumination, and idleness. The application of bST increased milk yield and technical and economic yields of Minas Padrão cheese did not show significant differences between treatments.

Assessment of temperature-induced hERG channel blockade variation by drugs

Drug-induced QT prolongation has been reported in humans and animals. This potentially lethal effect can be induced by drugs interacting with a cardiac potassium channel, namely hERG (human ether-a go-go-related gene) leading to arrhythmia or torsade de pointes (TdP). Hence, in vitro evaluation of therapeutics for their effects on the rapid delayed rectifier current (IKr) mediated by the K(+) ion channel encoded by hERG is a valuable tool for identifying potential arrhythmic side effects during drug safety testing. Our objective was to evaluate the temperature-induced hERG channel blockade variation by human and veterinary drugs using the IonFlux 16 system. A panel of eight drugs was tested for IKr inhibition at both ambient (23 °C) and physiological (37 °C) temperatures at various concentrations using IonFlux 16, an automated patch clamp system. Our results established that both amiodarone (IC(50)  = 0.56 μM at 23 °C and 0.30 μM at 37 °C) and β-estradiol (IC(50)  = 24.72 μM at 23 °C and 8.17 μM at 37 °C) showed a dose-dependent IKr blockade with a higher blockade at 37 °C. Whereas, blockade of IKr by both ivermectin (IC(50)  = 12.52 μM at 23 °C and 24.41 μM at 37 °C) and frusemide (IC(50)  = 12.58 μM at 23 °C and 25.55 μM at 37 °C) showed a dose-dependent IKr blockade with a lower blockade at 37 °C. Gentamicin, enrofloxacin, xylazine and albendazole did not block IKr at both the assessed temperatures. Collectively, these results demonstrate that the effect of temperature variation should be taken into consideration during the evaluation of test drugs for their hERG channel blockade potential.

Colostrogenesis during an induced lactation in dairy cattle

Colostrum immunoglobulin G (IgG) is of major importance for the newborn calf because epitheliochorial placentae do not provide transport in utero. The formation of colostrum occurs in the later stages of pregnancy. Our objectives were to induce lactation in non-pregnant dairy cows and (i) to determine the changes of IgG in serum and mammary secretions during the induction process and (ii) to establish α-lactalbumin (αLA) and prolactin (Prl) alterations to monitor the changing mammary epithelial tight junction status and development pattern. Estradiol-17β (E2) and progesterone (P4) injections in a 1-7 days series were combined with a 3-day injection series (day 21-23) of dexamethasone (DEX). Blood and both front quarter secretion samples were collected daily. Milking started 24 days after the start of the experiment. Results show that the mammary secretory IgG1 was increased at >7 days after the start of steroid injections and depicted a bimodal pattern reaching a high of 16 mg/ml at 21 day compared with 3.2 mg/ml in the serum. There was a small increase in secretory IgG2 that did not correlate with tight junction status, but never reached the serum concentration. The injections of DEX resulted in constriction of tight junctions. Secretory αLA was immediately increased with steroid injections, dropped precipitously after 7 days and then began a steady increase until the start of milking. Changes in serum αLA are related to mammary tight junctions while serum Prl gradually increased from 30 to >60 ng/ml after the steroid injections stopped. These results provide insights into the mechanisms and timing of colostrogenesis during an induced lactation protocol.

Colostrogenesis: IgG1 transcytosis mechanisms

Biological transport of intact proteins across epithelial cells has been documented for many absorptive and secretory tissues. Immunoglobulins were some of the earliest studied proteins in this category. The transcellular transport (transcytosis) of immunoglobulins in neonatal health and development has been recognized; the process is especially significant with ungulates because they do not transcytose immunoglobulins across the placenta to the neonate. Rather, they depend upon mammary secretion of colostrum and intestinal absorption of immunoglobulins in order to provide intestinal and systemic defense until the young ungulate develops its own humoral defense mechanisms. The neonatal dairy calf's ability to absorb immunoglobulins from colostrum is assisted by a ~24 h "open gut" phenomenon where large proteins pass the intestinal epithelial cells and enter the systemic system. However, a critical problem recognized for newborn dairy calves is that an optimum mass of colostrum Immunoglobulin G (IgG) needs to be absorbed within that 24 h window in order to provide maximal resistance to disease. Many calves do not achieve the optimum because of poor quality colostrum. While many studies have focused on calf absorption, the principal cause of the problem resides with the extreme variation (g to kg) in the mammary gland's capacity to transfer blood IgG1 into colostrum. Colostrum is a unique mammary secretory product that is formed during late pregnancy when mammary cells are proliferating and differentiating in preparation for lactation. In addition to the transcytosis of immunoglobulins, the mammary gland also concentrates a number of circulating hormones into colostrum. Remarkably, the mechanisms in the formation of colostrum in ungulates have been rather modestly studied. The mechanisms and causes of this variation in mammary gland transcytosis of IgG1 are examined, evaluated, and in some cases, explained.

Induced lactation in heifers: Effects of dexamethasone and age at induction on milk yield and composition

Milk production in heifers induced into lactation is lower than that of postpartum primiparous cows. A method to improve milk production in induced lactations may provide opportunities for increased profitability as well as increase our understanding of the mechanisms that regulate mammary gland development and colostrum composition. The present study was conducted to determine if dexamethasone administration at the onset of milking or age at lactation induction would affect milk production in heifers induced into lactation. Holstein heifers at 14 [n=20; 354 ± 38 kg of body weight (BW)] and 18 mo of age (n=20; 456 ± 30 kg of BW) were assigned randomly to dexamethasone (DEX) or control (CON) treatment groups in a 2 × 2 factorial arrangement with age and dexamethasone treatment as the 2 factors. Heifers were induced into lactation with daily subcutaneous injections of estradiol-17β and progesterone (0.075 and 0.25 mg/kg of BW per d, respectively) on experimental d 1 to 7. They also received bovine somatotropin (bST) every 14 d beginning on experimental d 1. Milking began on experiment d 18 (lactation d 1). Dexamethasone (10mg) was administered on lactation d 1 and 2 following the morning milking; CON heifers did not receive dexamethasone. Milk yield from d2 to 15 of lactation of heifers receiving DEX (7.8 kg/d) was greater than that of CON heifers (6.0 kg/d) but was similar thereafter through 305 d of lactation (18.2 kg/d). Milk production to d 11 was similar for 14- and 18-mo-old heifers but was greater for 18- (18.9 kg/d) than for 14-mo-old animals (17.4 kg/d) through 305 d in milk. Milk fat percentage increased initially and was greater in DEX (4.51%) compared with CON (3.53%) heifers until 21 d in milk. Milk protein and lactose concentrations were not affected by DEX treatment. Age at induction did not affect milk fat, protein, or lactose percentages. Mean milk IgG concentration declined from 107.4 mg/mL on d 1 to 5.0mg/mL on d 7 of lactation, tended to be greater for 18- compared with 14-mo-old heifers, and was not different due to DEX treatment. Administration of DEX to heifers induced into lactation increased initial milk production during the first 2 wk of lactation but this effect did not persist through 305 DIM. Treatment with DEX appeared to stimulate mammary cell differentiation but did not change the rate of decline of milk IgG concentrations. Higher milk yield in 18-mo-old heifers may be due to greater mammary epithelium, higher body mass, or both.