Insulin-like growth factor-I, insulin-like growth factor-binding proteins, and gonadotropins in the hypothalamic-pituitary axis and serum of nutrient-restricted ewes.

Body condition scores (BCS) of ovariectomized estradiol-treated ewes were controlled to examine effects of suboptimum BCS on insulin-like growth factor (IGF)-I, IGF-binding proteins (IGFBPs), and LH in the anterior pituitary gland, hypophyseal stalk-median eminence (SME), and circulation. Serum LH increased in ewes with BCS (1 = emaciated, 9 = obese) > 3 (HIGH-BCS), but not in ewes with BCS

Effects of extruded corn or grain sorghum on intake, digestibility, weight gain, and carcasses of finishing steers.

We conducted two trials to evaluate the effects of extruding vs dry-rolling either corn or grain sorghum on intake, digestibility, and performance of finishing steers. In Trial 1, 92 crossbred steers (average BW 413 kg) were used in a 2 x 2 factorial design. Diets contained either dry-rolled corn (RC), extruded corn (EC), dry-rolled grain sorghum (RGS), or extruded grain sorghum (EGS). Diets were fed for 110 d and contained 78.6% of the respective grain, 9% alfalfa pellets, 8.2% molasses, and 4.2% protein-mineral supplement. Daily gain was highest (P < .049) for steers fed RC, and the ADG of steers fed RGS was higher than that of steers fed extruded diets; there was no difference in ADG between steers fed EC and those fed EGS. Steers fed dry-rolled diets consumed more DM (P = .001) than steers fed extruded diets. Feed efficiency was not affected (P = .18) by processing method, but steers fed corn utilized the diets more efficiently (P = .006) than steers fed grain sorghum. Except for carcass weight, carcass data were not affected by grain type (P > .20). Dressing percentage, quality grade, and longissimus muscle area were lower (P < .09) in steers that received extruded grain than in those that received dry-rolled grain. In Trial 2, five ruminally cannulated crossbred steers (average BW 518 kg) were used in a 4 x 4 + 1 Latin square design to evaluate the ruminal and total tract digestion characteristics of the diets used in Trial 1. Type of grain had no effect (P > .16) on intake, total tract digestibility, or ruminal pH. Extruding corn or grain sorghum decreased intake (P < .001) but increased (P < .074) DM and starch digestibility compared with dry rolling; steers fed extruded diets had lower (P < .032) ADF and NDF digestibilities. Ruminal in situ DM and starch disappearance were higher (P < .03) and ruminal pH was lower (P < .052) in steers fed extruded grains than in those fed dry-rolled grains. Data from this study indicate that extruded corn and extruded grain sorghum are highly degradable feeds; however, decreased DM intake and lower ruminal pH levels resulted in lower performance.

Intake and digestion of low-, medium-, and high-quality grass hays by lambs receiving increasing levels of corn supplementation.

Thirty wether lambs (52.5 +/- 1.5 kg) were used in a replicated 3 x 5 factorial treatment arrangement and four periods to determine dietary intake and digestibility of three ground forages with increasing levels of supplemental ground corn. Forages were a mature, low-protein grass hay (LQH; 5.2% CP), an immature, medium-protein grass hay (MQH; 10.2% CP), and an immature, high-protein grass hay (HQH; 14.2% CP). Supplementation treatments were no supplement (NS), a protein supplement (PS), protein plus .25% BW of corn (LC), protein plus .5% BW of corn (MC), and protein plus .75% BW of corn (HC). Crude protein intake (1.4 g/kg BW) from supplements was equalized with soybean meal and corn gluten meal. Lambs were housed in metabolism crates. Supplements were fed at 0700 each morning after orts from the previous day's feeding were removed. Hay was subsequently offered at approximately the previous day's consumption plus 25%. Each of the four periods lasted 21 d. Sixteen days were allowed for diet adaptation. Feces were collected with fecal bags during d 17 to 21. Lambs receiving LQH and PS had higher forage (P < .04) and total DMI (P < .001) than lambs fed LQH and NS. Corn supplementation decreased forage intake (quadratic effect; P = .08), total intake (quadratic effect; P = .08), and increased apparent DM digestibility (linear effect; P < .04) with lambs receiving LQH. Protein supplementation did not affect forage or total DMI (P > .11), and corn supplementation did not affect total DMI (P > .20) with either MQH or HQH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute glucose antagonism on hypophyseal hormones and concentrations of insulin-like growth factor (IGF)-I and IGF-binding proteins in serum, anterior pituitary, and hypothalamus of ewes.

The objectives of this study were to determine whether 2-deoxy-D-glucose (2DG), a metabolic inhibitor of glucose, 1) differentially affected release of LH, growth hormone (GH) and prolactin (PRL); 2) decreased anterior pituitary response to GnRH; and 3) altered concentrations of insulin-like growth factor I (IGF-I) and intensity of 125I-IGF-I binding to proteins (IGFBPs) in serum, anterior pituitary (AP), and hypothalamus (preoptic are [POA], medial basal hypothalamus [MBH], and stalk median eminence [SME]). In trial 1, mature, ovariectomized, crossbred ewes were treated with a single s.c. injection of either saline (n = 5) or 2DG (n = 5; 0.1 g/kg BW). Administration of 2DG suppressed (p < 0.05) concentrations of LH but did not affect (p > 0.05) serum concentrations of GH or PRL. In trial 2, ovariectomized ewes received injections of saline or 2DG, and each group was subdivided to receive either saline or GnRH analog (5 micrograms; Des-Gly10-[D-Ala6]) 2 h later. Administration of 2DG suppressed (p < 0.05) serum concentrations of LH before administration of GnRH; however, release of LH in response to exogenous GnRH was greater (p < 0.05) in ewes that received 2DG. Treatment with 2DG did not affect (p > 0.05) concentrations of FSH before or after administration of GnRH. In trial 3, 10 ovariectomized ewes were slaughtered 2 h after treatment with saline (n = 5) or 2DG (n = 5). Serum and tissues collected at slaughter (AP, MBH, SME, and POA) were analyzed for concentrations of IGF-I by RIA and intensity of 125I-IGF-I binding to proteins by ligand blotting.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of increasing levels of corn or beet pulp on utilization of low-quality crested wheatgrass hay by lambs and in vitro dry matter disappearance of forages.

Two trials were conducted to evaluate the effects of corn or dried beet pulp on intake and digestibility of forage by lambs and on IVDMD. In Trial 1, 16 lambs (average BW = 41 +/- .9 kg) were used in a randomized complete block design with eight lambs per block. Lambs were fed a crested wheatgrass hay (7.5% CP) and received either no supplement (NS), a protein supplement (PS), or protein supplements with various levels of corn or beet pulp. Corn supplements supplied 1.75 (PCL), 3.5 (PMC), and 5.25 (PHC) g of corn/kg of BW, whereas beet pulp supplements supplied 2.1 (PLBP), 4.2 (PMBP), and 6.3 (PHBP) g of beet pulp/kg of BW. All supplemented lambs received .128 g of CP/kg of BW. Hay DMI decreased linearly (P < .03) as the level of corn and beet pulp increased in the supplement. Total DMI decreased linearly (P = .013) as the level of corn increased; however, beet pulp did not affect total DMI (P > .71). Supplemental corn increased (P = .03) apparent diet DM digestibility (DMD), whereas supplemental beet pulp did not affect (P > .32) diet DMD. Lambs whose diet was supplemented with beet pulp had greater (P = .010) estimated hay DMD than lambs whose diet was supplemented with corn. In Trial 2, 48-h IVDMD was determined on each of three forages mixed with either corn or beet pulp. The crude protein content of the three forages was 4.9, 9.4, and 12.2% for low-, medium-, and high-quality forages, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Intake and digestion of low-quality meadow hay by steers and performance of cows on native range when fed protein supplements containing various levels of corn.

Two trials were conducted to evaluate the effects of corn in protein supplements fed to cattle receiving low-quality forages. In Trial 1, four ruminally cannulated steers (avg BW 500 kg) and four intact steers (avg BW 270 kg) were used in a replicated latin square to determine intake and digestibility fo a low-quality meadow hay (4.3% CP) when fed no supplement (NS), 1.12 g CP/kg BW (PS), 1.12 g CP/kg BW with corn supplying 1.98 g starch/kg BW (PLC) or 1.12 g CP/kg BW with corn supplying 3.96 g starch/kg BW (PHC). Hay DMI decreased (P = .001) and total diet DMI increased (P = .001) quadratically as supplemental corn increased. Diet DM digestibility increased (P = .004) and forage DM and hemicellulose digestibility decreased (P less than or equal to .018) quadratically as level of corn in the diet increased. In Trial 2, 135 cows received either ear corn (1.16 kg TDN and 127 g CP.hd(-1).d(-1), ear corn plus protein (1.16 kg TDN) and 290 g CP g CP.hd(-1).d(-1) or protein (.72 kg TDN and 290 g CP.hd(-1.d(-1) while grazing native Sandhills winter range for 112 d and while receiving hay (10% CP) during the following 60-d calving period. Cows that received ear corn lost (P less than .001) more weight than cows fed ear corn plus protein supplement, which lost more weight than cows fed only protein supplement (-54, -18 and 6 kg, respectively) during the 112-d winter grazing period. Cows that received ear corn and ear corn plus protein gained more (P less than .001) weight during calving and summer grazing (after supplement wa withdrawn) than protein-supplemented cows. Reproductive performance was not affected (P greater than .705) by treatments.

Intake and digestibility of low-quality meadow hay by cattle receiving various levels of whole shelled corn.

Two trials were conducted to evaluate the effects of whole shelled corn supplementation on intake and digestibility of low-quality meadow hay by cattle. In Trial 1, four ruminally cannulated steers (avg BW 418 kg) were used in a latin square design with four treatments (no corn or corn fed at .25%, .50% or .75% of BW). Hay DMI decreased (P = .002) linearly .43 g for each gram of increase in corn intake. In contrast, total diet DMI increased (P = .001) linearly as level of corn supplementation increased. Apparent DM digestibility of the diet increased (P = .026) linearly, whereas hay DM digestibility was not affected (P greater than .05) by supplemental corn, although the DM digestion coefficient for hay alone was 24% higher than for hay fed with corn at .75% of BW. Ruminal ammonia concentration and pH were not affected (P greater than .05) by treatments; however, ratio of acetate:propionate and acetate:butyrate responded (P less than or equal to .097) quadratically to increased corn supplementation. Corn supplementation resulted in a cubic (P less than or equal to .081) decrease in meadow hay NDF disappearance from nylon bags suspended in the rumen at all incubation intervals after 4 h. In Trial 2, 45 crossbred, nonlactating, pregnant cows (avg BW 474 kg) were used in a completely randomized design with three treatments (no corn, .91 and 1.81 kg corn.hd-1.d-1). Cow performance was not altered (P greater than .05) by treatments.(ABSTRACT TRUNCATED AT 250 WORDS)