Serum hormones, follicular fluid steroids, insulin-like growth factors and their binding proteins, and ovarian IGF mRNA in sheep with different ovulation rates.

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P < .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidiumbromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in B x F and B x C ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and F x C ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from B x C and B x F ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from B x F ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of exogenous insulin on plasma and follicular insulin-like growth factor I, insulin-like growth factor binding protein activity, follicular oestradiol and progesterone, and follicular growth in superovulated Angus and Brahman cows.

Angus (n = 14) and Brahman (n = 14) cows were used to evaluate the effects of insulin administered concomitantly with FSH in a superovulation regimen. Cows were allotted to four pen replicates by treatment and breed, and received FSH (i.m.) twice a day for 5 consecutive days (first day of injections = day 0 of study) plus concomitant administration of either saline (control) or long-acting bovine insulin (0.25 iu kg-1 body mass; s.c.). Blood samples were collected at intervals of 6 h during the injection period and analysed for plasma insulin, glucose, insulin-like growth factor I (IGF-I) and IGF-I binding protein (IGFBP) activity. Cows were ovariectomized on day 5. The number and diameter of follicles were recorded. Follicular fluid was aspirated for determination of IGF-I, IGFBP activity, oestradiol and progesterone. Mean plasma concentration of glucose was lower in insulin-treated than in control cows averaged over days 1-5 (56 +/- 3 versus 82 +/- 3 mg dl-1; P < 0.01). Plasma concentration of IGF-I and IGFBP activity were not affected (P > 0.10) by treatment, but were higher in Brahman than in Angus cows (IGF-I: 41 +/- 6 versus 19 +/- 6 ng ml-1, P < 0.05; IGFBP activity: 17.5 +/- 0.4 versus 15.8 +/- 0.04% (10 microliters)-1; P < 0.03). Insulin treatment did not affect the number of small (1.0-3.9 mm), medium (4.0-7.9 mm) or large (> or = 8.0 mm) follicles. Brahman cows had a greater (P < 0.01) number of medium and total follicles (19.4 +/- 2.5 and 60.5 +/- 5.5, respectively) than did Angus cows (7.5 +/- 2.6 and 30.5 +/- 5.6, respectively). Diameter of large follicles was greater in insulin-treated than in control cows (11.4 +/- 0.2 versus 10.6 +/- 0.1 mm; P < 0.05). Follicular fluid IGF-I concentration in large follicles was higher in insulin-treated Brahman cows (60 +/- 2 ng ml-1) than in control Brahman cows (37 +/- 2 ng ml-1), but was lower in insulin-treated Angus cows (31 +/- 3 ng ml-1) than in control Angus cows (38 +/- 2 ng ml-1; treatment x breed interaction, P < 0.01). IGFBP activity in fluid from large follicles was not affected by insulin treatment in Brahman cows but was reduced (P < 0.05) by insulin treatment in Angus cows.(ABSTRACT TRUNCATED AT 400 WORDS)

Natural sodium sesquicarbonate fed for an entire lactation: influence on performance and acid-base status of dairy cows.

Forty-eight multiparous Holstein cows were blocked according to month of parturition, age, and previous milk yield and arranged in a randomized complete block design to evaluate the effect of a naturally occurring sodium sesquicarbonate on DMI, milk yield, milk composition, milk value, and systemic acid-base status. Cows were assigned at parturition to diets containing sorghum silage, alfalfa hay, concentrate, and 0 or 1% naturally occurring sodium sesquicarbonate (DM basis); cows were fed these diets for 308 d postpartum. Blood was collected every 4 wk via jugular venipuncture for analysis of pH, HCO3, partial pressure of O2, and partial pressure of CO2. Sesquicarbonate exhibited alkalogenic properties by increasing blood HCO3, partial pressure of CO2, and total CO2 for the 308-d lactation. Buffer tended to increase DMI and increased milk protein throughout lactation. During 0 to 56 d postpartum, sodium sesquicarbonate did not affect milk yield or composition. In midlactation (56 to 252 d postpartum), buffer increased milk protein content only. During 252 to 308 d postpartum, milk fat and protein contents increased with buffer supplementation. Hence, the value of milk yielded daily was similar for all cows. Effects of dietary buffer on all variables were more pronounced during late lactation.

Effects of basic fibroblast growth factor and heparin on follicle-stimulating hormone-induced steroidogenesis by bovine granulosa cells.

The objectives of the present study were to determine the effect of and interaction between basic fibroblast growth factor (bFGF) and heparin, a major bFGF-binding protein, on bovine granulosa cell estradiol and progesterone production. Cells from small (1 to 5 mm) follicles were collected from cattle, cultured for 2 d in medium containing 10% fetal calf serum, and then treated for 1 d with bFGF and(or) heparin in serum-free medium. Treatment with .1 to 10 micrograms/mL of heparin for 1 d had no effect (P > .05), whereas 100 micrograms/mL of heparin inhibited (P < .05) FSH-induced estradiol production by bovine granulosa cells. Treatment with .1 to 1.0 ng/mL of bFGF for 1 d, supplied with human serum albumin as a carrier protein, inhibited (P < .05) FSH-induced estradiol production by bovine granulosa cells, with the greatest inhibition detected at 1.0 ng/mL; coculture with 10 micrograms/mL of heparin did not influence these effects. In comparison, .1 ng/mL of bFGF supplied carrier-free had no effect (P > .05) on FSH-induced estradiol production, whereas 1.0 to 100 ng/mL of carrier-free bFGF inhibited (P < .05) FSH-induced estradiol production, with the greatest inhibition detected at 100 ng/mL. The presence of heparin (10 micrograms/mL) had variable effects on granulosa cell estradiol and progesterone production inhibited by carrier-free bFGF. These results indicate that bFGF may play a significant role in FSH-modulated granulosa cell steroidogenesis during follicular development in cattle.

Administration of porcine somatotropin by a sustained-release implant: effect on follicular growth, concentrations of steroids and insulin-like growth factor I, and insulin-like growth factor binding protein activity in follicular fluid of control, lean, and obese gilts.

Prepubertal gilts of control (n = 30), obese (n = 30), or lean (n = 29) genetic lines were implanted with no, one, or two implants of porcine somatotropin (pST, each delivers 2 mg/d) for 6 wk starting at 160 d of age to determine whether pST affects ovarian function. At 4 mg/d, pST increased (P < .01) numbers of 4.0- to 6.9-mm (medium) follicles but not (P > .10) numbers of 1.0- to 3.9-mm (small) follicles per gilt. Both doses of pST increased (P < .01) serum and follicular fluid (FFL) concentrations of IGF-I and activity of IGF binding protein (IGFBP)-3 and 36-kDa IGFBP in all three lines; IGFBP-3 was the predominant IGFBP. In comparison, binding activity of IGFBP-2 was decreased (P < .01) in serum by 4 mg of pST but increased (P < .05) in FFL by 4 mg of pST. Lean gilts had lower (P < .05) serum concentrations of IGF-I and less (P < .05) total binding activity of IGFBP than control and obese gilts. Concentrations of estradiol in FFL of small and medium follicles tended (P < .08) to be increased by 2 mg/d of pST, whereas FFL concentrations of progesterone were unaffected by pST. Obese and control gilts had twofold greater (P < .05) FFL progesterone concentrations than lean gilts. We conclude that sustained-release implants of pST can stimulate follicular growth, increase concentrations of IGF-I in serum and FFL, and increase IGFBP activity in serum of genetically divergent lines of gilts without an adverse effect on ovarian function.

Insulin-like growth factor-I receptors in ovarian granulosa cells: effect of follicle size and hormones.

The objectives of the present studies were to determine if the numbers of IGF-I receptors in bovine granulosa cells differed with size of follicle and to determine if growth factors and hormones affected the number of IGF-I receptors in granulosa cells. Granulosa cells from small (1-5 mm) and large (> or = 8 mm) follicles were cultured for 2-4 days in 10% FCS and then assessed for levels of IGF-I receptors. Numbers of IGF-I receptors were 15-fold greater in granulosa cells from large than small follicles. In addition, bFGF (5 and 50 ng/ml) decreased whereas estradiol (1 microgram/ml), FSH (10 ng/ml) and EGF (10 and 100 ng/ml) increased the number of IGF-I receptors in granulosa cells from small follicles. These hormones had no effect on the number of IGF-I receptors in granulosa cells from large follicles. In conclusion, granulosa cells from large follicles have a greater number of IGF-I receptors than cells from small follicles, and thus, it appears that granulosa cells acquire a greater number of IGF-I receptors during the process of differentiation.

Effects of inert fat on energy balance, plasma concentrations of hormones, and reproduction in dairy cows.

The objective was to determine the effects of dietary inert fat on estimated energy balance, hormones in plasma, and reproduction during early lactation. From wk 0 to 12 postpartum, 14 pluriparous Holstein cows were fed individually a TMR, and blood samples were taken twice weekly for quantification of IGF-I, progesterone, and cholesterol. During wk 5 to 12, one-half of the cows remained on the TMR, and the other half were fed the TMR containing inert fat at 1.8% of dietary DM. Estrous behavior was monitored twice daily, and body condition scores were recorded every 4 wk. Cows fed inert fat between wk 5 and 12 postpartum had similar concentrations of IGF-I in plasma but greater luteal phase progesterone secretions than cows fed the control diet. Total cholesterol in plasma also was greater in cows fed inert fat than in cows fed the control diet. Intervals to first, second, and third ovulation or estrus did not differ among cows fed control or inert fat diets. Body condition scores, daily DMI, and milk production were not affected by dietary inert fat. Inert fat fed to cows between wk 5 and 12 postpartum did not affect ovulatory activity but may enhance luteal activity.

Controlled ruminal infusion of sodium bicarbonate. 3. Influence of infusion dose on systemic acid-base status, minerals, and ruminal milieu.

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 x 4 Latin square to monitor effects of intraruminal NaHCO3 infusion on temporal changes in ruminal and systemic acid-base status and mineral metabolism. Twice daily from 2 to 4 h postfeeding, cows were infused with 0, 110, 220, or 330 g of NaHCO3 dissolved in 3.8 L of water. All cows had access to their TMR of sorghum silage and concentrate (35: 65, DM basis) for 2 h twice daily. Ruminal fluid, blood, and urine were collected at feeding and every 30 min postfeeding for 12 h on the last day of each 14-d period. Total urine volume also was measured during this interval. Infusion of buffer increased ruminal fluid buffering capacity transiently at 4.5 h postfeeding but otherwise did not markedly affect ruminal fluid acid-base status. Systemic acid-base status was unaffected by the buffer primarily because renal excretion of base successfully reduced systemic base load. Urine volume increased in response to NaHCO3 infusion. Buffer infusion increased urinary excretion of Na, Mg, and K but decreased Ca excretion for 12 h postfeeding; Cl excretion was not affected. Buffer infusion tended to increase total VFA in ruminal fluid. Our data indicate that homeostatic mechanisms can eliminate exogenous base via the kidneys; hence, acid-base status was not perturbed by infusion of NaHCO3. The increased excretion of Mg and K with buffer infusion indicates that the dietary requirements for these minerals may be increased by NaHCO3. Although loss of Ca through the urine was reduced by buffer infusion, this reduction may indicate reduced availability of Ca to the cow. The diuresis accompanying large doses of NaHCO3 may increase dietary requirements for some minerals.

Controlled ruminal infusion of sodium bicarbonate. 2. Effects of dietary and infused buffer on ruminal milieu.

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 X 4 Latin square to monitor the effects of NaHCO3 infusion on ruminal environment of cows receiving dietary sodium bicarbonate. Sodium bicarbonate (110 g) was mixed with 3.8 L of water and infused at a constant rate into the rumen from 0 to 2, 2 to 4, or 4 to 6 h postfeeding twice daily. All cows were fed sorghum silage and concentrate in a 35:65 DM ratio for 45 min twice daily. Ruminal fluid was collected at feeding and every 30 min postfeeding for 8 h on the last day of each 1-wk experimental period. Dry matter intake was not affected by NaHCO3 infusion. Yields of milk and its components were reduced with 4- to 6-h NaHCO3 infusion. At certain isolated times, especially during infusion, NaHCO3 infusion increased ruminal fluid buffer. Concentrations of ruminal fluid total VFA were not affected by NaHCO3 infusions, whereas acetate to propionate ratio tended to be reduced. Ruminal liquid volume tended to be increased by 0- to 2-h NaHCO3 infusion, and ruminal outflow rate tended to be reduced by the 2- to 4-h infusion. Intraruminal infusion of NaHCO3 into cows receiving supplemental dietary NaHCO3 altered ruminal acid-base status as typically reported for those receiving dietary NaHCO3; however, these alterations were not accompanied by shifts in ruminal VFA patterns or in milk composition that normally result from such feeding regimens. The effects of NaHCO3 infused directly into the rumen may be different from those of dietary NaHCO3 and are possibly related to the different time of entry into the rumen relative to feeding.

Controlled ruminal infusion of sodium bicarbonate. 1. Influence of postfeeding infusion interval on ruminal milieu.

Four ruminally cannulated, lactating Holstein cows were assigned to a 4 x 4 Latin square to monitor the effects of intraruminal NaHCO3 infusion on changes in the rumen environment. Sodium bicarbonate (110 g), dissolved in 3.8 L of water, was infused twice daily at a constant rate for 2 h starting at 0, 2, or 4 h postfeeding. All cows had access to their diet containing sorghum silage and concentrate in a 35:65 ration (DM basis) for 45 min twice daily. Ruminal fluid was collected at feeding and every 30 min postfeeding for 12 h on the last day of each 7-d period. Dry matter intake was lower for buffer infusion at 2 to 4 h than for water-infused control but was not affected by the other NaHCO3 infusions. Although total milk yield was not affected, milk fat percentage and fat yield tended to be lower for the NaHCO3 treatments. Compared with the water infusion, the NaHCO3 infusion from 2 to 4 h postfeeding most effectively prevented the postfeeding increase in ruminal free proton concentration. Additionally, volume of ruminal liquid was increased for the NaHCO3 infusions from 0 to 2 h and 4 to 6 h; ruminal liquid turnover time was increased for the NaHCO3 infusion at 4 to 6 h, but ruminal kinetics otherwise were not affected by NaHCO3. Although infusion of NaHCO3 from 2 to 4 h prevented severe alterations in ruminal acid-base status, it did not increase total VFA concentration or the acetate:propionate ratio. Although total VFA concentrations were not affected by NaHCO3 infusion, acetate:propionate ratio was higher for the NaHCO3 infusion from 0 to 2 h than for the control. Based upon alterations in ruminal acid-base status, exogenous buffer ideally should be provided to the rumen from 2 to 4 h postfeeding; however, our results indicate that the effectiveness of this regimen might be improved if buffer is combined with a rapidly released or unprotected dietary buffer.