Postpartum nutrition affects the insulin-like growth factor system in dominant follicles and plasma of anestrous beef cows.

Effects of nutrition on insulin-like growth factor-I (IGF-I), IGF binding proteins (IGFBP), and insulin in plasma and dominant follicles were evaluated at day 72 and 56 (Exp. 1, n = 12 and Exp. 2, n = 28, respectively) postpartum in anovulatory primiparous beef cows. Cows were stratified based on body condition score at calving and randomly assigned to nutritional treatments: maintain (M), 2.27 kg of a 40 % CP supplement per day and ad libitum hay; or gain (G), ad libitum access to a 50 % concentrate diet and ad libitum hay. Blood samples were collected twice weekly starting 30 days postpartum. Ovarian follicles were evaluated using ultrasonography commencing 42 (Exp. 1) or 30 (Exp. 2) days postpartum. Body weight and condition score were greater (P < 0.05) for cows of G than M groups and postpartum interval to luteal function was longer for cows of the M than G group. Insulin and IGF-I concentrations in follicular fluid (FF) and plasma were greater (P < 0.05) for cows of the G than M group at follicular aspiration. Plasma and FF IGFBP4 and IGFBP5 concentrations were greater (P <  0.05) in Exp. 2, and IGFBP5 was greater in Exp. 1 for cows of the G than M group. Treatment did not affect FF steroid concentrations or granulosal cell CYP19A1, PAPPA, IGFBP4, and IGFBP5 mRNA abundance. These results indicate concentrations of IGF-I, insulin, IGFBP4, and IGFBP5 in FF and plasma are affected by nutritional intake and may be related to follicular function.

Effects of N-carbamylglutamate and L-arginine on gonadotrophin-releasing hormone (GnRH) gene expression and secretion in GT1-7 cells.

Recent studies have shown that N-carbamylglutamate (NCG) and arginine (ARG) supplementation improves reproductive performance in livestock. The objectives of the present study were to evaluate the effects of NCG and ARG on GT1-7 cell gonadotrophin-releasing hormone (GnRH) secretion, gene expression and cell proliferation. GT1-7 cells were treated in vitro with different concentrations of NCG (0-1.0mM) or ARG (0-4.0mM) in serum-free medium for 12 or 24h. For GnRH secretion and cell proliferation, GT1-7 cells were more sensitive to NCG than ARG. NCG treatment after 12h increased cell numbers and inhibited GnRH secretion in a dose-dependent manner (P<0.05), although there was no significant effect of NCG on these parameters after 24h culture. ARG treatment decreased GnRH secretion after 24h (P<0.05), whereas it had no effect after 12h. GT1-7 cells express GnRH, Kiss-1 metastasis-suppressor (Kiss1), G-protein coupled receptor 54 (GPR54), neuronal nitric oxide synthase (nNOS) and estrogen receptor α (ERα) genes. High concentrations of NCG (1.0mM) and ARG (4.0mM) inhibited (P<0.05) GnRH and nNOS mRNA abundance in GT1-7 cells. ARG treatment decreased Kiss1 and increased ERα mRNA abundance. Thus, high concentrations of NCG (1.0mM) and ARG (4.0mM) may act both directly and indirectly to regulate GnRH neuron function by downregulating genes related to GnRH synthesis and secretion to slow GnRH production while stimulating GT1-7 cell proliferation.

Effects of body condition score at parturition and postpartum protein supplementation on estrous behavior and size of the dominant follicle in beef cows.

The objective of this study was to determine the effects of BCS at calving and the amount of postpartum protein supplementation on the dominant follicle (DF) and behavioral characteristics at the first postpartum estrus of mature beef cows. Multiparous Angus x Hereford cows (n = 45) were fed to calve in thin (T; < 5) or moderate (M; >or=5) BCS. Cows were stratified by BCS and calving date, and randomly assigned to receive lesser (L; 1.2 kg/d) or greater (G; 2.5 kg/d) amounts of a 42% CP supplement. All cows grazed the same native grass pasture and were fed in individual stalls for 49 +/- 2 d. Beginning 20 d after calving, blood samples were collected from each cow thrice weekly, and estrous behavior was monitored continuously with a radiotelemetry system. At 4 to 16 h after the onset of estrus, size of the DF was determined by ultrasonography. Body condition score of T cows was less (P < 0.01) at calving than M cows; L and G cows had similar BCS at calving and at the end of the feeding period. Body weight gains during treatment did not differ for L or G cows. Duration from calving to first estrus was greater (P < 0.01) for T than M cows. The incidence of a short luteal phase before first estrus was not influenced by BCS or protein supplement. Concentrations of IGF-I in plasma tended (P < 0.07) to be greater and size of the DF was greater (P < 0.01) for M than T cows. Size of the DF tended (P < 0.06) to be greater for G than L cows. Duration and number of mounts received at the first estrus were not influenced by BCS or supplement. Pregnancy rate of M cows during the breeding season was greater (P < 0.05) than T cows. Postpartum protein intake and BCS at calving influenced the size of the DF at the first postpartum estrus in mature suckled beef cows. Cows should be managed to calve in moderate BCS and maintain BW after parturition to decrease the interval to first estrus, increase follicular development, and maximize pregnancy rate.

Influence of nutrient intake and body fat on concentrations of insulin-like growth factor-I, insulin, thyroxine, and leptin in plasma of gestating beef cows.

Pregnant Angus x Hereford cows (n = 73) were used to determine the effects of amount of nutrient intake and BCS on concentrations of IGF-I, insulin, leptin, and thyroxine in plasma. At 2 to 4 mo of gestation, cows were blocked by BCS and assigned to one of four nutritional treatments: high (H = a 50% concentrate diet fed ad libitum in a drylot) or adequate native grass pastures and one of three amounts of a 40% CP supplement each day (M = moderate, 1.6 kg; L = low, 1.1 kg; or VL = very low, 0.5 kg; as-fed basis). After 110 d of treatment, all cows grazed dormant native grass pasture and received 1.6 kg/d of a 40% CP supplement. At 68, 109, and 123 d of treatment, cows were gathered, and plasma samples were collected by tail venipuncture (fed sample). After 18 h without feed and water, a second plasma sample was collected (fasted sample). At 109 d of treatment, BCS was greatest (P < 0.05) for H cows, similar for M and L cows, and least for VL cows. Concentrations of insulin and leptin were greater (P < 0.05) for H cows than for M and VL cows at 68 and 109 d, but similar for all groups at 123 d. Thyroxine in plasma was greatest (P < 0.05) for H cows at 68 d and similar for cows on all treatments at 123 d. Concentrations of IGF-I, insulin, and leptin in fed and fasted cows were positively correlated with BCS at 109 d. Body condition was predictive of concentrations of IGF-I, insulin, and leptin when cows had different nutrient intakes, but BCS accounted for less than 12% of the variation in plasma concentrations of IGF-I, insulin, and leptin when nutrient intake was the same for all cows. We conclude that amount of nutrient intake has a greater influence than body energy reserves on IGF-I, insulin, and leptin concentrations in the plasma of gestating beef cows.

Insulin-like growth factor-I and its binding proteins in colostrum compared to measures in serum of Holstein neonates.

Colostral insulin-like growth factor-I (IGF-I) may be beneficial in the development of gastrointestinal tracts of bovine neonates. Thus, the purpose of this study was to examine relationships among concentrations of IGF-I and IGF-binding proteins (IGFBP) in colostrum used at two initial feedings and serum concentrations of IGF-I, IGFBP, total protein, gamma glutamyltransferase (GGT), and immunoglobulin G at 0 and 48 h after birth in Holstein neonates. Calves (n = 22) were separated from dams immediately after birth. Blood samples were taken before initial feeding and at 48 h after birth. Calves were fed 2 L of colostrum twice and milk replacer thereafter. Linear regression of serum IGF-I at 48 h and colostral IGF-I revealed a significant positive relationship (R2 = 0.204). Serum IGFBP-3 at 48 h and colostral IGFBP-3 also had a positive relationship (R2 = 0.143). However, linear regression of colostral IGF-I on the difference in serum IGF-I at 48 and 0 h was not significant. Calves were assigned to group 1 (0-h serum IGF-I < 10 ng/ml; n = 11) or group 2 (0-h serum IGF-I > or = 10 ng/ml; n = 11) for further analysis. There were no differences in serum IGF-I or IGFBP-2, -3, -4, and -5 concentrations at 48 h between groups 1 and 2. Correlation coefficients revealed negative relationships of serum IGF-I at 0 h to the difference between serum IGF-I at 48 and 0 h (r = -0.824), as well as birth weight of the calf to the amount of GGT at 48 h (r = -0.604). Females had lower birth weights than males, but sex of calf did not affect serum measures. At 0 h, but not 48 h, total serum protein was correlated to serum GGT concentrations (r = 0.573). From indirect evidence, absorption of colostral IGF-I and IGFBP-3 into systemic circulation may occur, but relative importance compared to endogenous sources is uncertain.

Propionibacteria fed to dairy cows: effects on energy balance, plasma metabolites and hormones, and reproduction.

To determine the effect of feeding Propionibacteria on energy balance, milk yield, and composition, metabolites and hormones of early-lactating dairy cows, multiparous Holstein cows were individually fed a total mixed ration from -2 to 12 wk postpartum with no addition (control, n = 10) or with an additional 17 g of Propionibacteria culture daily (Treated, n = 9). Daily feed intake and milk production were recorded. Plasma cholesterol, nonesterified fatty acids (NEFA), leptin, insulin, glucose, insulin-like growth factor-I (IGF-I), IGF-binding proteins (IGFBP), and progesterone concentrations were measured up to twice weekly. Cows fed supplemental Propionibacteria had improved energy balance at wk 1 of lactation and had lower DMI per kg of body weight than control cows on wk 3 to 7, 10, and 12. Cows fed Propionibacteria had a greater percentage of milk protein and solids-not-fat and plasma NEFA concentrations than did control cows only at wk 1 of lactation. Treatment did not affect milk production or percentage of milk fat and lactose. Leptin levels were greater in treated than control cows throughout the study. Plasma glucose, insulin, cholesterol, IGFBP-3, and IGF-I concentrations were not affected by feeding Propionibacteria, but those variables increased with week postpartum. Plasma IGFBP-2 and IGFBP-5 levels decreased with week postpartum. Measures of reproductive and ovarian function did not differ between Propionibacteria-treated and control cows. Feeding Propionibacteria culture to transition and early lactating dairy cows may hold potential for improved milk protein production and metabolic efficiency during early lactation, without affecting reproductive function.

Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle.

Ten Holstein cows averaging 120 d in lactation were arranged in replicated 5 x 5 Latin squares with 3-wk periods to evaluate the role of sulfur (S) in the dietary cation-anion balance equation. Diets were based on corn silage in Exp. 1 and sorghum silage in Exp. 2. Supplemental S and chloride (Cl) from the double sulfate of potassium and magnesium and CaCl2 were used to manipulate dietary cation-anion balance from 0 to +30 meq when expressed as meq [(Na + K)-(Cl + S)]/100 g diet DM and from +19 to +49 meq when expressed as meq [(Na + K)-Cl]/100 g diet DM. Blood pH was not affected by cation-anion balance, although both S and Cl supplementation tended to lower pH. Blood HCO3- and urine pH decreased and plasma calcium (Ca) and urinary Ca excretion increased as anion was added to the diet. Milk fat production tended to be increased by the low S supplementation. Dietary Cl and S had similar effects on acid-base status. Therefore, we suggest that S be included with Cl in the dietary cation-anion balance equation for lactating dairy cows as follows: meq [(Na + K)-(Cl + S)]/100 g diet DM. Although response of acid-base status to S and Cl was similar, as more data comparing the acidogenicity of S vs Cl become available, it may be necessary to include a modifying coefficient for S in the equation to adjust for differences between S and Cl in acid-generating potential. This coefficient may be further dependent on the dietary source of S.