Effects of nanoselenium supplementation on lactation performance, nutrient digestion and mammary gland development in dairy cows

The objective of this experiment was to evaluate the influence of nanoselenium (NANO-Se) addition on milk production, milk fatty acid synthesis, the development and metabolism regulation of mammary gland in dairy cows. Forty-eight Holstein dairy cows averaging 720 ± 16.8 kg of body weight, 66.9 ± 3.84 d in milk (dry matter intake [DIM]) and 35.2 ± 1.66 kg/d of milk production were divided into four treatments blocked by DIM and milk yields. Treatments were control group, low-Se (LSe), medium-Se (MSe) and high-Se (HSe) with 0, 0.1, 0.2 and 0.3 mg Se, respectively, from NANO-Se per kg dietary dry matter (DM). Production of energy- and fat-corrected milk (FCM) and milk fat quadratically increased (p < 0.05), while milk lactose yields linearly increased (p < 0.05) with increasing NANO-Se addition. The proportion of saturated fatty acids (SFAs) linearly decreased (p < 0.05), while proportions of monounsaturated fatty acids (MUFAs) linearly increased and polyunsaturated fatty acids (PUFAs) quadratically increased. The digestibility of dietary DM, organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) quadratically increased (p < 0.05). Ruminal pH quadratically decreased (p < 0.01), while total VFA linearly increased (p < 0.05) with increasing NANO-Se addition. The acetic to propionic ratio decreased (p < 0.05) linearly due to the unaltered acetic molar percentage and a quadratical increase in propionic molar percentage. The activity of CMCase, xylanase, cellobiase and pectinase increased linearly (p < 0.05) following NANO-Se addition. The activity of α-amylase increased linearly (p < 0.01) with an increase in NANO-Se dosage. Blood glucose, total protein, estradiol, prolactin, IGF-1 and Se linearly increased (p < 0.05), while urea nitrogen concentration quadratically decreased (p = 0.04). Moreover, the addition of Se at 0.3 mg/kg from NANO-Se promoted (p < 0.05) mRNA and protein expression of PPARγ, SREBP1, ACACA, FASN, SCD, CCNA2, CCND1, PCNA, Bcl-2 and the ratios of p-ACACA/ACACA and BCL2/BAX4, 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 by NANO-Se addition by stimulating rumen fermentation, nutrients digestion, gene and protein expressions concerned with milk fat synthesis and mammary gland development.

Effects of dietary folic acid supplementation on lactation performance and mammary epithelial cell development of dairy cows and its regulatory mechanism

The experiment investigated the impacts of FA on the proliferation of bovine mammary gland epithelial cells (BMECs) and to investigate the underlying mechanisms. Supplementation of 10 µM FA elevated the mRNA expression of proliferating cell nuclear antigen (PCNA), cyclin A2 and cyclin D1, and protein expression of PCNA and Cyclin A1. The mRNA and protein expression of B-cell lymphoma-2 (BCL2) and the BCL2 to BCL2 associated X 4 (BAX4) ratio elevated, while that of BAX, Caspase-3 and Caspase-9 reduced by FA. Both Akt and mTOR signaling pathways were activated by FA. Moreover, the stimulation of BMECs proliferation, the alteration of proliferative genes and protein expression, the change of apoptotic genes and protein expression, and the activation of mTOR signaling pathway caused by FA were obstructed by Akt inhibitor. Suppression of mTOR with Rapamycin reversed the FA-modulated promotion of BMECs proliferation and change of proliferous genes and protein expression, with no impact on mRNA or proteins expression related to apoptosis and FA-activated Akt signaling pathway. Supplementation of rumen-protected FA in cow diets evaluated milk yields and serum insulin-like growth factor-1 and estradiol levels. The results implied that the proliferation of BMECs was stimulated by FA through the Akt-mTOR signaling pathway.

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.

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.

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.