Intramammary infusion of leptin decreases proliferation of mammary epithelial cells in prepubertal heifers

High energy intake and excessive body fatness impair mammogenesis in prepubertal ruminants. High energy intake and excessive fatness also increase serum leptin. Our objective was to determine if an infusion of leptin decreases proliferation of mammary epithelial cells of prepubertal heifers in vivo. Ovine leptin at 100 mu g/quarter per d with or without 10 mu g of insulin-like growth factor (IGF)-I was infused via the teat canal into mammary glands of prepubertal dairy heifers; contralateral quarters were used as controls. After 7 d of treatment, bromodeoxyuridine was infused intravenously and heifers were slaughtered similar to 2 h later. Tissue from 3 regions of the mammary parenchyma was collected and immunostained for bromodeoxyuridine (BrdU), proliferating cell nuclear antigen (Ki-67), and caspase-3. Leptin decreased the number of mammary epithelial cells in the S-phase of the cell cycle by 48% in IGF-I-treated quarters and by 19% in saline-treated quarters. Leptin did not alter the number of mammary epithelial cells within the cell cycle, as indicated by Ki-67 labeling. Caspase-3 immunostaining within the mammary parenchyma was very low in these heifers, but leptin significantly increased labeling in saline-treated quarters. Leptin enhanced SOCS-3 expression in IGF-I-treated quarters but did not alter SOCS-1 or SOCS-5 expression. We conclude that a high concentration of leptin in the bovine mammary gland reduces proliferation of mammary epithelial cells. The reduced proliferation is accompanied by an increase in SOCS-3 expression, suggesting a possible mechanism for leptin inhibition of IGF-I action. Whether leptin might be a physiological regulator of mammogenesis remains to be determined.

A comparison of dissected follicle numbers and follicle counts on the ovarian surface for the evaluation of ovarian follicular populations in Bos indicus cows

Ovaries (n = 140) from 70 mixed-age multiparous, lactating Brahman cross (3/4-7/8 Bos indicus) cows were used to examine the hypothesis that counts of follicles visible on the surface of the ovaries of Bos indicus cows and their classification into diameter size classes, are closely correlated with numbers of follicles in those size classes found by complete dissection of the ovary. immediately after ovariectomy, mean diameters (long and short axes averaged) of all follicles greater than or equal to 2 mm visible on the surface of each ovary were measured. All follicles greater than or equal to 2 mm were dissected from the ovaries, excess stroma removed and follicle diameters measured under a stereomicroscope using an ocular graticule. For each ovary, follicles were classified in either small (8 mm) categories based on either diameters of surface or dissected follicles. Data for numbers of surface and dissected follicles (mean +/- SE) in small, medium, large categories and total follicle numbers, respectively, were 24.4 +/- 1.6 vs. 28.0 +/- 1.9, 1.6 +/- + 0.2 vs. 11.6 +/- 1.0, 0.5 +/- 0.1 vs. 0.7 +/- 0.1 and 26.4 +/- 1.6 vs. 40.4 +/- 2.5. Correlation coefficients (r) for counts of surface and dissected follicles in small, medium, large and total follicle numbers were 0.76, 0.40, 0.69 and 0.79, respectively. Medium size follicles presented only a small translucent area on the surface of the ovary, leading to an underestimate of numbers when categorised by surface evaluation. Counts of follicles visible on the surface of the ovaries of Bos indicus cows and their classification into size classes based on estimated diameter, are closely correlated with numbers of follicles in those size classes found at dissection of the ovary for small (8 mm) and total follicles but not for medium sized (4-8 mm) follicles. (C) 1997 Elsevier Science B.V.

Crescimento dos tecidos muscular e adiposo e qualidade da carne de novilhas de diferentes grupos genéticos no modelo biológico superprecoce

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of bovine somatotropin administration on growth, physiological, and reproductive responses of replacement beef heifers

This experiment compared growth, body composition, plasma IGF-I and leptin, and reproductive development of beef heifers receiving or not recombinant bovine ST (BST) beginning after weaning until the first breeding season. Fifty Angus × Hereford heifers (initial BW = 219 ± 2 kg; initial age = 208 ± 2 d), weaned at approximately 6 mo of age, were assigned to the experiment (d 0 to 210). On d 0, heifers were ranked by initial BW and age and assigned to 1) treatment with BST or 2) saline control. Heifers assigned to the BST treatment received subcutaneous (s.c.) injections containing 250 mg of sometribove zinc whereas control heifers received a 5-mL s.c. injection of 0.9% saline every 14 d. Treatments were initiated on d 14 and last administered on d 196. Heifers were maintained on separate pastures harvested for hay the previous summer according to treatment and received grass and alfalfa hay at a rate to provide a daily amount of 7.0 and 1.0 kg of DM per heifer, respectively. Heifer shrunk BW was collected on d 1 and 211 for heifer ADG calculation. Blood samples were collected weekly from d 0 to 210 for determination of plasma progesterone to estimate puberty attainment as well as plasma concentrations of IGF-I and leptin in selected samples. On d 0, 63, 133, and 189, heifers were evaluated for intramuscular marbling, LM depth, and backfat thickness via real-time ultrasonography. No treatment effects were detected (P = 0.27) for heifer ADG (0.49 vs. 0.51 kg/d for control and BST heifers, respectively; SEM = 0.02). Mean backfat thickness was lesser (P < 0.01) in BST heifers compared with control cohorts (3.56 vs. 3.92 mm, respectively; SEM = 0.08). Heifers receiving BST had greater plasma IGF-I concentrations compared with control cohorts 7 d after treatment administration (treatment × day interaction; P < 0.01). Mean plasma leptin concentrations were lesser (P = 0.05) in BST heifers compared with control cohorts (1.82 vs. 2.03 ng/mL, respectively; SEM = 0.07). Onset of puberty was hastened in BST heifers compared with control cohorts (treatment x day interaction; P = 0.04). In summary, a greater proportion of BST heifers reached puberty during the experiment compared with control cohorts, despite lesser plasma leptin concentrations, backfat thickness, and similar ADG. Hence, circulating IGF-I was positively associated with hastened puberty attainment independently of growth rate, circulating leptin concentrations, and body fat content of replacement beef heifers. © 2013 American Society of Animal Science. All rights reserved.

Growth performance and meat quality of heifers receiving different forms of soybean oil in the rumen

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The nutritive value of Rhodes grass (Chloris gayana) when treated with CaO, NaOH or a microbial inoculant and offered to dairy heifers as big-bale silage

A series of laboratory and animal studies examined the use of chemical and biological agents to enhance the digestibility of Rhodes grass (grass) cut at 60 (young) and 100 (mature) days of regrowth and ensiled as big round bales. The treatments included an untreated control (C), a microbial inoculant (I), NaOH, CaO and NaOH plus inoculant (NaOH + I). Inoculant was grown anaerobically, using a starter culture of rumen fluid from cattle given Rhodes grass. Treatments C, 1, NaOH, NaOH + I, were offered separately to twelve dairy heifers, in a 3 X 4 randomized complete block design, repeated twice for each grass silage. C and I had substantial mould growth, compared with no visible mould in NaOH or NaOH + 1. CaO treatment was effective in preventing mould growth, but had little effect on the chemical composition and in sacco digestibility of mature grass silage. NaOH reduced NDF content and increased in sacco digestibility (P < 0.05) but not the in vivo digestibility (P > 0.05) of both mature- and young-grass silage. The effects of other treatments on nutritive value were non-significant at both stages of maturity. NaOH increased the intake of mature-grass silage by 24-26% (P < 0.05), but had little effect on the intake of young-grass silage (P > 0.05). Treatment I consistently reduced grass silage intake (P < 005) for young-grass silage. The findings of these studies show that treating mature Rhodes grass with NaOH will improve its nutritive value and reduce mould growth in conserved herbage. However none of the treatments in this study had any consistently positive effects on the in vivo nutritive value or storage quality of young-grass silage.

Use of GnRH agonist implants for long-term suppression of fertility in extensively managed heifers and cows

The ability of gonadotrophin releasing hormone (GnRH) agonist implants to suppress ovarian activity and prevent pregnancies, long-term, was examined in heifers and cows maintained under extensive management. At three cattle stations, heifers (2-year-old) and older cows (3- to 16-year-old) were assigned to a control group that received no treatment, or were treated with high-dose (12 mg, Station A) or low-dose (8 mg, Station B and Station Q GnRH agonist implants. The respective numbers of control and GnRH agonist-treated animals (heifers + cows) at each station were: Station A, 20 and 99; Station B, 19 and 89; Station C, 20 and 76. Animals were maintained with 4% bulls and monitored for pregnancy at 2-monthly intervals for approximately 12 months. Pregnancy rates for control heifers and control cows ranged from 60-90% and 80-100%, respectively, depending on the study site. The respective number of animals (heifers + cows) treated with GnRH agonist that conceived, and days to first conception, were: Station A, 9 (9%) and 336 3 days; Station B, 8 (10%) and 244 +/- 13 days; Station C, 20 (26%) and 231 +/- 3 days. Treatment with high-dose GnRH agonist prevented pregnancies for longer (similar to300 days) than treatment with low-dose GnRH agonist (similar to200 days). In the majority of heifers and cows treated with GnRH agonist, ovarian follicular growth was restricted to early antral follicles (2-4 mm). The findings indicate that GnRH agonist implants have considerable potential as a practical technology to suppress ovarian activity and control reproduction in female cattle maintained in extensive rangelands environments. The technology also has broader applications in diverse cattle production systems. (C) 2002 Elsevier Science B.V. All rights reserved.

Control of ovulation with a GnRH agonist after superstimulation of follicular growth in buffalo: fertilization and embryo recovery

The potential to use a GnRH agonist bioimplant and injection of exogenous LH to control the time of ovulation in a multiple ovulation and embryo transfer (MOET) protocol was examined in buffalo. Mixed-parity buffalo (Bubalus bubalis; 4-15-year-old; 529 13 kg LW) were randomly assigned to one of five groups (n = 6): Group 1, conventional MOET protocol; Group 2, conventional MOET with 12 It delay in injection of PGF(2alpha); Group 3, implanted with GnRH agonist to block the pre-ovulatory surge release of LH; Group 4, implanted with GnRH agonist and injected with exogenous LH (Lutropin(R), 25 mg) 24 h after 4 days of superstimulation with FSH; Group 5, implanted with GnRH agonist and injected with LH 36 h after superstimulation with FSH. Ovarian follicular growth in all buffaloes was stimulated by treatment with FSH (Folltropin-V(R), 200 mg) administered over 4 days, and was monitored by ovarian ultrasonography. At the time of estrus, the number of follicles greater than or equal to8 mm. was greater (P < 0.05) for buffaloes in Group 2 (12.8) than for buffaloes in Groups 1 (8.5), 3 (7.3), 4 (6.1) and 5 (6.8), which did not differ. All buffaloes were mated by AI after spontaneous (Groups 1-3) or induced (Groups 4 and 5) ovulation. The respective number of buffalo that ovulated, number of corpora lutea, ovulation rate (%), and embryos + oocytes recovered were: Group 1 (2, 1.8 +/- 1.6, 18.0 +/- 13.6, 0.2 +/- 0.2); Group 2 (4, 6.1 +/- 2.9, 40.5 +/- 17.5, 3.7 +/- 2.1); Group 3 (0, 0, 0, 0); Group 4 (6, 4.3 +/- 1.2, 69.3 +/- 14.2, 2.0 +/- 0.9); and Group 5 (1, 2.5 +/- 2.5, 15.5 +/- 15.5, 2.1 +/- 2.1). All buffaloes in Group 4 ovulated after injection of LH and had a relatively high ovulation rate (69%) and embryo recovery (46%). It has been shown that the GnRH agonist-LH protocol can be used to improve the efficiency of MOET in buffalo. (C) 2002 Elsevier Science Inc. All rights reserved.

Assessment of DGAT1 and LEP gene polymorphisms in three Nelore (Bos indicus) lines selected for growth and their relationship with growth and carcass traits

The aim of this study was to analyze LEP and DGAT1 gene polymorphisms in 3 Nelore lines selected for growth and to evaluate their effects on growth and carcass traits. Traits analyzed were birth, weaning, and yearling weight, rump height, LM area, backfat thickness, and rump fat thickness obtained by ultrasound. Two SNP in the LEP gene [LEP 1620(A/G) and LEP 305(T/C)] and the K232A mutation in the DGAT1 gene were analyzed. The sample consisted of 357 Nelore heifers from 2 lines selected for yearling weight and a control line, established in 1980, at the Estacao Experimental de Zootecnia de Sertaozinho (Sertaozinho, Brazil). Three genotypes were obtained for each marker. Differences in allele frequencies among the 3 lines were only observed for the DGAT1 K232A polymorphism, with the frequency of the A allele being greater in the control line than in the selected lines. The DGAT1 K232A mutation was associated only with rump height, whereas LEP 1620(A/G) was associated with weaning weight and LEP 305(T/C) with birth weight and backfat thickness. However, more studies, with larger data sets, are necessary before these makers can be used for marker-assisted selection.

Characterization and polymorphism screening of IGF-I and prolactin genes in Nelore heifers

Insulin growth factor I (IGF-I) and prolactin (PRL) are peptide hormones that exert complementary effects on reproductive traits by acting on folliculogenesis. In view of the lack of information about the IGF-I and PRL genes in Bos indicus, the objective of this study was to partially characterize the promoter regions of these genes and to screen animals of different ages at first pregnancy for the presence of polymorphisms in these regions. In addition, we determined whether polymorphisms influence the regulation of the two hormone genes, evaluating their association with sexual precocity.The animals were divided into three groups according to age at first pregnancy: 1) 100 heifers considered to be sexually precocious that became pregnant at 15-16 months of age, 2) 100 heifers that became pregnant during the normal breeding season at 24 months of age, and 3) 100 heifers that did not become pregnant until 24 months of age. For the IGF-I gene, PCR-RFLP-SnaBI analysis showed the presence of genotypes AB and BB at frequencies of 0.02 and 0.98, respectively. Sequencing of the IGF-I gene fragment revealed a single nitrogen base change from cytosine to thymine, corresponding to the restriction site of SnaBI. The polymorphisms identified in the 5'-flanking region of the IGF-I gene may serve as a basis for future studies of molecular markers in cattle. For the PRL gene, PCR-RFLP-HaeIII analysis showed the presence of only one migration pattern, a finding characterizing the region studied as monomorphic. The study of other regions in the IGF-I and PRL genes might provide molecular data that can be used in the future for the selection of sexually precocious animals.

Assessment of DGAT1 and LEP gene polymorphisms in three Nelore (Bos indicus) lines selected for growth and their relationship with growth and carcass traits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

MUC1 gene polymorphism in three Nelore lines selected for growth and its association with growth and carcass traits

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

First polymorphisms in JY-1 gene in cattle (Bos taurus indicus) and their association with sexual precocity and growth traits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)