Differential effects of plane of protein or energy nutrition on visceral organs and hormones in lambs

Effects of Dietary Energy Levels on Rumen Fermentation, Gastrointestinal Tract Histology, and Bacterial Community Diversity in Fattening Male Hu Lambs

This study investigated rumen fermentation and histological and microbial diversity in male Hu lamb fed diets with different metabolizable energy (ME) levels (MEA, 9.17 MJ/kg, MEB, 10.00 MJ/kg, and MEC, 10.82 MJ/kg). Thirty-six male Hu lambs were randomly allotted to three treatments, and the feeding trial lasted for 67 days. Rumen fermentation results suggest that the iso-valerate had a significant effect on dietary energy level. The papillary height (PH) of rumen was the highest in the MEB group, the crypt depth (CD) was significantly increased in the duodenum and jejunum, and the villus height (VH)-to-CD ratio (VH/CD) was significantly decreased in the duodenum by increasing dietary energy levels; the VH, villus width (VW), and VH/CD also had significant differences in the ileum. 16S rRNA sequencing results showed that the operational taxonomic units (OTUs) number, the ACE, and Chao1 indices were linearly decreased by increasing dietary energy level; 24 phyla including 124 genera were identified, and the relative abundance of Papillibacter and Quinella linearly decreased by increasing the dietary energy level. Compared to MEA and MEB groups, the relative abundance of unidentified_Veillonellaceae and Anaerovibrio was significantly increased in the MEC group at the genus level. The relative abundance of the carbohydrate metabolism pathway predicted by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was linearly increased by increasing the dietary energy levels. Three metabolic pathways identified in Kyoto Encyclopedia of Genes and Genomes (KEGG) level 3 were significantly influenced as the dietary energy level increased. In summary, these results demonstrated that the dietary energy levels affected the rumen fermentation parameters, morphological structures of the gastrointestinal tract (GIT), and the composition and function of rumen microflora in male Hu sheep.

Effects of dietary energy levels on rumen fermentation, microbiota, and gastrointestinal morphology in growing ewes

This study investigated whether dietary metabolizable energy (ME) could generate dynamical effects on rumen fermentation, gastrointestinal tract (GIT) morphology, and microbial composition of growing ewes. A total of twenty-eight female Hu lambs were randomly allotted to two treatments with different dietary ME levels: 9.17 (FEA) and 10.41 MJ/kg (FEB). These lambs were further made ready for a 67-day feeding trial. Results showed that the molar proportions of butyrate (p = .020), iso-valerate (p = .028), and valerate (p = .005) were significantly higher in the FEB group than those in the FEA group. The results of the GIT morphologic properties showed that the villus height (VH) (p = .005) was significantly higher and crypt depth was significantly deeper (CD) (p = .005) in the duodenum and that the rumen papillary height (PH) was significantly higher (p = .020) in FEB group compared with the FEA group. High-throughput sequencing results showed that 1826 operational taxonomic units (OTUs) were obtained and that the OTU number (p = .039), the ACE (p = .035), and Chao1 indices (p = .005) were lower in the FEB group. Moreover, 76 genera belonging to 21 phyla were detected in all samples; the relative abundance of Papillibacter (p = .036) and Flexilinea (p = .046) was significantly lower in the high energy group, whereas the relative abundance of unidentified Lachnospiraceae (p = .019), Acetitomaculum (p = .029), unidentified Veillonellaceae (p = .017), Anaerovibrio (p = .005), and Succinivibrio (p = .035) was significantly higher in the FEB group at the genus level. Furthermore, the relative abundance of genes and metabolic pathways were predicted by PICRUSt. The relative abundance of gene families related to carbohydrate metabolism was particularly higher (p = .027) in the FEB group. In summary, these results reveal that the dietary energy levels altered the composition and function of rumen microbiota and GIT morphology in growing female Hu sheep and provide a reference for optimizing diet formula and 10.41MJ/kg of ME level has been recommended in the growing period.

Transcriptome assisted label free proteomics of hepatic tissue in response to both dietary restriction and compensatory growth in cattle

Compensatory growth (CG) is a naturally occurring phenomenon where, following a period of under nutrition, an animal exhibits accelerated growth upon re-alimentation. The objective was to identify and quantify hepatic proteins involved in the regulation of CG in cattle. Forty Holstein Friesian bulls were equally assigned to one of four groups. Groups; A1 and A2 had ad libitum access to feed for 125 days, groups R1 and R2 were feed restricted. Following this, R1 and A1 animals were slaughtered. Remaining animals (R2 and A2) were slaughtered following ad libitum feeding for a successive 55 days. At slaughter hepatic tissue samples were collected and label-free quantitative proteomics undertaken with spectra searched against a custom built transcriptome database specific to the animals in this study. 24 differentially abundant proteins were identified during CG (R2 vs. R1) including; PSPH, ASNS and GSTM1, which are involved in nutrient metabolism, immune response and cellular growth. Proteins involved in biochemical pathways related to nutrient metabolism were down-regulated during CG, indicating a possible adaptive response by the liver to a period of fluctuating nutrient availability. The livers ability to regulate its metabolic activity may have profound effects on the efficiency of whole body energy utilization during CG. SIGNIFICANCE: This study is the first to unravel the effect of compensatory growth on the hepatic proteome of cattle using transcriptome-assisted shot gun proteomics. Proteins identified as being affected by dietary restriction and subsequent expression of compensatory growth in this study may, following appropriate validation, contribute to the identification of functional genetic variants. Such information could be harnessed within the context of genomic selection in cattle breeding programs to identify animals with a greater genetic potential to undergo compensatory growth, thus increasing the profitability of the beef sector and accelerating genetic gain.

Effect of feed restriction on hepatic estradiol metabolism and liver function in cows

In this study, the effects of restriction feeding on the liver function, hepatic uridine diphosphate glucuronosyltransferase (UGT) activity, hepatic insulin-like growth factor (IGF)-1 mRNA expression and response to high-dose estradiol-17β (E₂) administration were investigated in non-lactating cows. Cows were assigned to either restricted feeding (30% of total digestible nutrient requirement) or ad libitum feeding of a dent corn-based concentrate and roughage for a 2-week feeding trial (Day 1=day of beginning the feeding trial). On day 14, a high-dose E₂ administration study was carried out to examine plasma E₂ levels as an indicator of hepatic E₂ metabolism. Plasma E₂ concentration in the restricted feeding group was consistently higher after high-dose E₂ administration than in the control group. In addition, indocyanine green half-life value was prolonged by restricted feeding for 13 days, and increased liver triglyceride concentration and decreased liver UGT activity were caused by this restriction over 14 days. Restricted feeding did not affect plasma IGF-1 concentration or hepatic IGF-1 mRNA expression. These results suggest that two weeks of restriction feeding led to accumulation of triglyceride, decreased liver blood flow, and slightly impaired liver function, which in turn slowed down the hepatic metabolism of E₂ without significantly impacting hepatic IGF-1 production.

Dietary energy and protein levels influenced the growth performance, ruminal morphology and fermentation and microbial diversity of lambs

The aim of the study was to evaluate the ruminal function and microbial community of lamb under different nutrient levels. Sixty-four lambs with similarity body weight were randomly assigned to four groups after weaning off ewe’s milk on the 17th day (6.2 ± 0.2 kg). The lambs of the control group (CON) were fed a basal diet, and the other three groups were subjected to a diet of decreased protein (PR), digestible energy (ER) or both of them at 20% (BR) of basal diet. The decrease of dietary protein or energy level decreased the average daily gain, ruminal weight and mucosal thickness of lambs (P < 0.05). The total volatile fatty acid (TVFA), acetate and propionate concentration of the CON group were significantly higher than that of the other three groups. The dietary protein and energy level affected the microbial diversity, and low energy level increased the relative abundance of phyla of Fibrobacteres, whereas at the genus level, increased the relative abundance of Butyrivibrio and Prevotellaceae. Under different dietary energy and protein levels, 14 genera exhibited significant correlation with ruminal fermentation. These findings supplied new perspective for the understanding of the dietary effect on ruminal microbial community interactions and are of great significance for establishing the optimal nutrient supply strategy for lambs.

Effects of dietary protein restriction followed by realimentation on growth performance and liver transcriptome alterations of lamb

The present study aimed to investigate the compensatory effect of early protein restriction followed by a realimentation on growth performance of lamb and to explore the transcriptomic changes in liver. Thirty-two lambs with an initial birth weight of 2.3 ± 0.20 kg that were weaned on day 15 were randomly divided into two groups. The lambs were fed a basal diet with normal protein level (NPL, protein level in the milk replacer and starter, 25 and 21%, respectively) or low protein level (LPL, protein level in the milk replacer and starter, 19 and 15%, respectively) from 15 to 60 d, after which all lambs consumed the same diet with a normal protein level from 61 to 90 d. Protein restriction led to a significant decrease in average daily gain (ADG), body weight and liver weight (P < 0.05). Transcriptome analysis showed that 302 or 12 differentially expressed genes (DEGs) were identified during the restriction or recovery periods, respectively (P < 0.05). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that DEGs enriched in nutrient metabolism and antioxidant capacity were down-regulated, while vessel development and immunity response-related genes up-regulated. The genes involved in metabolism of tyrosine were still down-regulated in the realimentation phase. Studies in this area indicated the accelerated growth effect of early protein restriction followed by a realimentation on growth performance of lambs and explored the transcriptomics change of liver which can help to develop feeding strategies to optimize the use of feedstuffs and in providing a new perspective for the study of early nutrition and epigenetics in later life.

Comparative slaughter performance and carcass quality of three Ethiopian fat-tailed hair sheep breeds supplemented with two levels of concentrate

A study was conducted to compare carcass and noncarcass yield, carcass composition, conformation, and fat depot partitioning of three Ethiopian fat-tailed hair sheep breeds (Blackhead Ogaden (BHO), Horro, and Washera) under two concentrate supplement levels (CSL). Sixteen sheep from each genotype (8 sheep per concentrate level), a total of 48, were used in a 3 × 2 factorial arrangement (3 breeds and 2 CSL). The two CSL were 1% (L1) and 1.75% (L2) body weight. Animals were about a year of age at the start of the experiment and all were slaughtered after 90 days of fattening. Dressing percentage per SBW was in the orders of Horro > BHO = Washera (P < 0.001). Total edible noncarcass component yield per EBW (TENCCY/EBW) of Horro breed (21%) was heavier (P < 0.0001) by about 2.8% than that from BHO and Washera sheep. Blackhead Ogaden sheep had significantly (P < 0.05) higher fat percentage and fat to bone ratio, while lower lean to fat ratio than Horro and Washera sheep. The fat partitioning results showed that carcass depot is the major fat depot in BHO and Horro sheep, whereas carcass fat and tail fat in Washera sheep had comparable value. The highest (P < 0.0001) carcass compactness index (CCI) value was obtained in Horro sheep, while the value for Washera was the lowest coupled with leg compactness index; as a result, Washera sheep had poor carcass conformation. Sheep supplemented with L2 had heavier HCW and CCW (P < 0.0001), wider RMA, and dressed better (P < 0.001) than L1-fed sheep. Carcass fat per CCW, carcass fat per total body fat (TBF), TYEP per SBW, and CCI values of the L2 diet-fed group were 2.7, 1.8, 1.2%, and 13.2 g/cm, respectively, higher (P < 0.05) than L1-supplemented sheep. The result highlights that Horro and Washera have closely comparable carcass composition, indicating the two breeds were at a similar stage of physiological maturity, while BHO appeared to be an early maturing sheep, suggesting a need for different feeding management for BHO to harvest lean meat. In conclusion, there existed a significant breed variation in most parameters considered in this study, which can be an opportunity to select breeds for various use and production objectives.

Ground Juniperus pinchotii and urea in supplements fed to Rambouillet ewe lambs: I. Feedlot growth traits, blood serum parameters, and fecal characteristics

Ground woody products and urea are low-cost roughage and N sources. Rambouillet ewe lambs ( = 48, 6 lambs/treatment; initial BW = 42 kg ± 3.8) were used to evaluate effects of using ground (juniper) and urea in supplements on feedlot lamb growth traits, blood serum parameters, and fecal characteristics. In a randomized complete block design (40 d), lambs were individually fed an ad libitum basal sorghum-Sudangrass hay diet, which was fed separate from 1 of 8 supplemental diets (6 lambs/diet; 533 g of supplement/d, as-fed basis). Treatment structure was a 4 × 2 factorial: 4 concentrations of ground juniper (JN: 15%, 30%, 45%, or 60% of DM) and 2 concentrations of urea (UR: 1 or 3% of DM). Lamb growth traits were evaluated on d 0, 5, 12, 19, 26, 33, and 40; blood serum was evaluated on d 6 to 8, 20 to 22, and 34 (at h 3 and 6), and feces was evaluated on d 35. Compared to lambs fed all of the other treatments, lambs fed JN60UR1 or JN60UR3 had reduced supplement DMI (negative quadratic, = 0.007). Hay and total DMI were variable across day (JN × UR × day, < 0.04), but no linear or quadratic trends were detected ( > 0.10). A JN × day interaction was detected ( < 0.001) for lamb BW and the JN × day negative quadratic trend ( = 0.02) for BW was influenced by reduced ADG (linear decrease, < 0.001) of lambs fed JN60. Lambs supplemented with UR3 vs. UR1 tended ( = 0.06) to have reduced BW but had similar ( > 0.17) ADG and G:F. Lamb G:F fluctuated across day (JN × day, = 0.007), but the JN × day quadratic trend ( < 0.001) was mainly due to reduced G:F in lambs fed JN45 or JN60 diets. As the percentage of JN increased in the supplement, serum IGF-1 linearly decreased ( = 0.04), and serum urea N quadratically increased ( < 0.001). The UR × hour interaction ( < 0.001) for serum urea N resulted from a greater decline from 3 to 6 h after feeding in lambs supplemented with UR1 vs. UR3. Increasing JN concentration tended to quadratically increase ( = 0.09) fecal DM and linearly decrease ( = 0.002) fecal N, but an effect due to dietary UR was not detected ( > 0.34). Results indicated that daily supplement DMI was restricted only by using JN60. However, a 60% JN-based supplement will not make an effective rangeland supplement for growing ewe lambs, and using 3% UR should not be considered, especially since daily UR intake was not restricted enough to be considered safe.

Effect of dietary restriction and subsequent re-alimentation on the transcriptional profile of bovine ruminal epithelium

Compensatory growth (CG) is utilised worldwide in beef production systems as a management approach to reduce feed costs. However the underlying biology regulating the expression of CG remains to be fully elucidated. The objective of this study was to examine the effect of dietary restriction and subsequent re-alimentation induced CG on the global gene expression profile of ruminal epithelial papillae. Holstein Friesian bulls (n = 60) were assigned to one of two groups: restricted feed allowance (RES; n = 30) for 125 days (Period 1) followed by ad libitum access to feed for 55 days (Period 2) or (ii) ad libitum access to feed throughout (ADLIB; n = 30). At the end of each period, 15 animals from each treatment were slaughtered and rumen papillae harvested. mRNA was isolated from all papillae samples collected. cDNA libraries were then prepared and sequenced. Resultant reads were subsequently analysed bioinformatically and differentially expressed genes (DEGs) are defined as having a Benjamini-Hochberg P value of <0.05. During re-alimentation in Period 2, RES animals displayed CG, growing at 1.8 times the rate of their ADLIB contemporary animals in Period 2 (P < 0.001). At the end of Period 1, 64 DEGs were identified between RES and ADLIB, with only one DEG identified at the end of Period 2. When analysed within RES treatment (RES, Period 2 v Period 1), 411 DEGs were evident. Genes identified as differentially expressed in response to both dietary restriction and subsequent CG included those involved in processes such as cellular interactions and transport, protein folding and gene expression, as well as immune response. This study provides an insight into the molecular mechanisms underlying the expression of CG in rumen papillae of cattle; however the results suggest that the role of the ruminal epithelium in supporting overall animal CG may have declined by day 55 of re-alimentation.

Supplementation of metabolizable protein during late gestation and fetal number impact ewe organ mass, maternal serum hormone and metabolite concentrations, and conceptus measurements

To examine the effects of maternal metabolizable protein (MP) supplementation during late gestation on serum hormone and metabolites and organ masses, multiparous ewes (n = 45) carrying singletons or twins were allotted randomly (within pregnancy group) to 1 of 3 treatments: 60% (MP60), 80% (MP80), or 100% (MP100) of MP requirements. Blood samples were drawn before the initiation of diets (day 100) and before slaughter (day 130) for chemistry panel analysis and weekly for hormone analysis including progesterone (P4) and estradiol-17β (E2). At day 130, ewe organ masses were recorded. Despite being fed isocaloric diets, MP60 ewes gained less weight throughout pregnancy compared with MP80 and MP100 ewes which were similar. Although diet did not impact E2 or P4 concentrations, ewes carrying twins had greater (P < 0.05) concentrations of both as gestation advanced. Albumin, aspartate aminotransferase, and total protein were reduced (P < 0.05) in MP60 compared with MP100 ewes near term. There was a diet by fetal number interaction (P = 0.03) for lactate dehydrogenase. Twin-carrying MP80 ewes had greater lactate dehydrogenase compared with all other groups on day 130 of gestation. Ewes that were fed MP80 had greater body weight on day 130 of gestation compared with MP60 ewes. Kidney and heart weights were lighter in MP60 ewes compared with MP80 ewes. There was a maternal diet by fetal number interaction (P = 0.05) on fetal weight per unit empty ewe body weight. In ewes carrying singletons, MP60 ewes supported less fetal weight compared with MP100. In contrast, MP60 ewes supported more fetal mass compared with MP100 ewes when carrying twins. The level of protein, and not just total energy, in the diet appears to impact some aspects of the maternal system. Moreover, it appears some measurements of mobilizing maternal body resources are enhanced in ewes carrying twins.

Effects of road transportation or droving on the weight and metabolism of young bulls

This study evaluated the effects of the mode of transportation on weight and metabolism of young bulls, which are generally transported by two systems: droving and truck. This experiment consisted of two phases: transportation and refeeding and involved transportation by droving and truck. Fifty young Nellore bulls were separated in equal numbers in both groups, droving group and truck group. In the transportation phase, animals were moved, in a 640-km journey. The refeeding phase consisted of 84 days and commenced after the animals arrived at the fattening farm. The effect of the transportation system on animals' weight, metabolic hormones, and serum biochemistry was assessed after 28, 56, and 84 days. During the transportation phase, animals in the droving group lost 10.11 kg and animals in the truck group gained 13.1 kg. The truck group showed 20.5 kg of weight gain at the end of the refeeding phase. The highest triiodothyronine (T3) and thyroxine (T4) concentrations were observed on days 0 and 60 in the transportation phase in both droving and truck groups. The serum cortisol concentration was higher in the droving group than in the truck group on day 56 of the refeeding phase. The IGF-I concentrations were higher during the refeeding phase in the droving group than in the truck group. Our results showed that transportation by droving leads to increased weight loss and reduced further weight gain compared to transportation by truck and that serum concentrations of T4, cortisol, and insulin-like growth factor (IGF-I) hormones are altered by the transportation system.

Effects of using ground redberry juniper and dried distillers grains with solubles in lamb feedlot diets: growth, blood serum, fecal, and wool characteristics

Effects of using ground redberry juniper and dried distillers grains with solubles (DDGS) in Rambouillet lamb (n = 45) feedlot diets on growth, blood serum, fecal, and wool characteristics were evaluated. In a randomized design study with 2 feeding periods (Period 1 = 64% concentrate diet, 35 d; Period 2 = 85% concentrate diet, 56 d), lambs were individually fed 5 isonitrogenous diets: a control diet (CNTL) that contained oat hay but not DDGS or juniper or DDGS-based diets in which 0 (0JUN), 33 (33JUN), 66 (66JUN), or 100% (100JUN) of the oat hay was replaced by juniper. During Period 1, lambs fed CNTL had greater (P < 0.05) DMI and ADG and tended to have greater (P < 0.10) G:F than lambs fed 0JUN or lambs fed DDGS-based diets. Lamb DMI, ADG, and G:F quadratically increased (P < 0.008) as juniper increased in the DDGS-based diets. During Period 2, lambs fed CNTL had greater (P < 0.05) DMI than lambs fed 0JUN or lambs fed DDGS-based diets, but ADG was similar (P > 0.41). Compared to 0JUN, lambs fed CNTL had similar (P = 0.12) G:F and tended to have less G:F (P = 0.07) than lambs fed DDGS-based diets. Among lambs fed DDGS-based diets, DMI was similar (P > 0.19), ADG increased linearly (P = 0.03), and G:F tended to decrease quadratically (P = 0.06) as juniper increased in the diet. Serum IGF-1, serum urea N (SUN), and fecal N were greater (P < 0.05) and serum Ca and P and fecal P were similar (P > 0.13) for lambs fed CNTL vs. lambs fed DDGS-based diets (CNTL). Within lambs fed DDGS-based diets, SUN increased quadratically (P = 0.01) and fecal N increased linearly (P = 0.004), which can partially be attributed to increased dietary urea and condensed tannin intake. Most wool characteristics were not affected, but wool growth per kilogram of BW decreased quadratically (P = 0.04) as percentage of juniper increased in the DDGS-based diets. When evaluating the entire 91-d feeding trial, results indicated that replacing all of the ground oat hay with ground juniper leaves and stems in lamb growing and finishing diets is not detrimental to animal performance and that DDGS-based diets can reduce total feedlot costs, as compared to sorghum grain and cottonseed meal-based diets. However, compared to using juniper or oat hay as the sole roughage source, using both during the growing period (Period 1) enhanced growth performance and further reduced total feedlot costs.

Effects of energy and protein restriction, followed by nutritional recovery on morphological development of the gastrointestinal tract of weaned kids

Effects of energy, protein, or both energy and protein restriction on gastrointestinal morphological development were investigated in 60 Liuyang Black kids, which were sourced from local farms and weaned at 28 d of age. Weaned kids were randomly assigned to receive 1 of 4 dietary treatments (15 kids per treatment), which consisted of adequate nutrient supply (CON), energy restriction (ER), protein restriction (PR), or energy and protein restriction (EPR). The entire experiment included adaptation period (0 to 6 d), nutritional restriction period (7 to 48 d), and recovery period (49 to 111 d). Three kids from each group were killed at d 48 and 111, and the rumen, duodenum, jejunum, and ileum were harvested. On d 48 (end of nutritional restriction), lengths of the duodenum (P = 0.005), jejunum (P = 0.003), and ileum (P = 0.003), and weights of the rumen (P = 0.004), duodenum (P = 0.006), jejunum (P = 0.006), and ileum (P = 0.004) of kids in ER, PR, and EPR were less than those of kids in CON. Compared with CON, PR decreased papillae width (P = 0.03) and surface area (P = 0.05) of the rumen epithelium, villus surface area (P = 0.05), and N concentration (P = 0.02) of the jejunum mucosa on d 48. Compared with CON, EPR decreased papillae height (P = 0.001), width (P = 0.001), and surface area (P = 0.003), N concentration (P = 0.01), and the ratio of N to DNA (P = 0.03) of the rumen epithelium. Compared with CON, EPR also decreased villus height (P = 0.01), width (P = 0.006), and surface area (P = 0.006), N concentration (P < 0.001), and the ratio of N to DNA (P < 0.001) of the jejunum mucosa on d 48. On d 111 (end of nutritional recovery), lengths of the duodenum (P = 0.001), jejunum (P = 0.001), and ileum (P = 0.001), weights of the rumen (P < 0.001), duodenum (P = 0.001), jejunum (P < 0.001), and ileum (P < 0.001) of kids in ER, PR, and EPR were still less than those of kids in CON; N concentrations of rumen epithelium of kids in PR (P = 0.01) and EPR (P = 0.001), and the ratio of N to DNA of jejunum mucosa of kids in EPR (P < 0.001) were greater than those of kids in CON. Results indicate that nutritional restriction of 6 wk can retard gastrointestinal morphological development for kids weaned at 28 d of age and retarded development remains evident, even after nutritional recovery of 9 wk.

Effects of restricted feed intake on heat energy by different goat breeds

Sixteen Boer goat doelings, 16 Spanish doelings, and 8 Angora doelings and 8 wethers, 283, 316, and 330 d of age initially (SEM = 5.0), respectively, were used to evaluate effects of nutrient restriction on heat energy (HE). During the first and second 10-wk phases, 8 animals of each breed were fed a 50% concentrate pelletized diet at a level adequate for maintenance and moderate energy accretion (CONT). Other animals were fed approximately 50% of these amounts in phase 1 relative to initial BW, followed by the greater level of feeding in phase 2 based on initial or actual BW when greater (REST). Average daily gain was 43, -20, 16, -78, 8, and -48 g in phase 1 (SEM = 5.0) and 26, 44, 50, 65, 27, and 32 g in phase 2 (SEM = 3.5) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively. Total HE was greater for CONT vs. REST in both phases (P < 0.001), greater in phase 1 for Angora than for Boer (P < 0.01) and Spanish (P < 0.01), and greatest (P < 0.01) in phase 2 among breeds for Angora [481, 347, 430, 356, 424, and 338 kJ/kg of BW(0.75) per day in phase 1 (SEM = 11.1), and 494, 479, 445, 397, 444, and 406 kJ/kg of BW(0.75) per day in phase 2 (SEM = 11.3) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively]. Equations describing the temporal pattern of HE (kJ/kg of BW(0.75) per day), expressed as a percentage of the wk-0 value and corrected for corresponding breed × week CONT means, in phase 1 were 95.8 ± 2.43 - (8.18 ± 1.144 × week) + (0.655 ± 0.1098 × week(2)) for Angora (R(2) = 0.58), 95.3 ± 2.63 - (4.34 ± 1.237 × wk) + (0.271 ± 0.1187 × wk(2)) for Boer (R(2) = 0.41), and 97.4 ± 2.21 - (4.69 ± 1.068 × wk) + (0.282 ± 0.1021 × wk(2)) for Spanish (R(2) = 0.53). Phase 2 equations were 78.9 ± 2.22 + (8.74 ± 1.036 × wk) - (0.608 ± 0.0095 × wk(2)) for Angora (R(2) = 0.60), 77.5 ± 2.10 + (3.30 ± 0.978 × wk) - (0.153 ± 0.0942 × wk(2)) for Boer (R(2) = 0.39), and 80.6 ± 2.50 + (4.50 ± 1.165 × wk) - (0.208 ± 0.1122 × wk(2)) for Spanish (R(2) = 0.43). These equations indicate that changes in HE in response to nutrient restriction and realimentation were more rapid and of greater magnitude in Angora vs. Boer and Spanish. The temporal pattern of decline in HE by Boer and Spanish during restriction was similar, but the subsequent rise with realimentation was slower and smaller for Boer. In conclusion, most appropriate methods of predicting change in the maintenance energy requirement during and after periods of limited feed intake may differ among breeds of goats.

Effects of winter growing program on visceral organ mass, composition, and oxygen consumption of beef steers during growing and finishing

The purpose of this experiment was to investigate the effects of winter growing program on organ mass, composition, and oxygen consumption in beef steers. A total of 46 steers were used for the experiment. Four steers were randomly selected as an initial slaughter group. Remaining steers were randomly allotted to 1 of 4 treatment groups: 1) fed a high-concentrate diet for ad libitum intake (CF); 2) grazed on wheat pasture (WP); 3) fed a sorghum silage-based growing diet (SF); or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of BW gain during the growing phase. After the growing phase (112 d), steers in the WP, SF, and PF treatments were adapted to a high-concentrate diet for finishing. Steers from all treatments were slaughtered at a fat thickness of 1.27 cm as estimated by ultrasound. In addition, 6 steers from each treatment were randomly selected for slaughter at the end of the growing phase. Weights of all individual organs were measured and tissue samples of duodenum and liver collected. At the end of the growing phase, WP steers had greater (P < 0.05) small intestine, liver, and kidney mass than SF and PF steers. In contrast, mesenteric fat mass and total visceral fat content were greatest (P < 0.01) for PF, intermediate for SF, and least for WP steers. Mass of total viscera and total splanchnic tissues (TST) did not differ (P > 0.10) among treatments. At final slaughter, mass of mesenteric fat, total viscera, and TST were similar among treatments, but liver weights remained greatest (g/kg of empty BW; P < 0.01) for WP steers. There were no differences in oxygen consumption of duodenum or liver tissue on an equal weight basis (microL.min(-1.)g(-1)) at the end of either period. Growing program affected mass of components of the TST at the end of the growing phase, which contributed to differences in rate of splanchnic organ growth during finishing. We conclude that program feeding a high-concentrate diet during the growing phase may result in greater ADG and G:F during the subsequent finishing period compared with forage-based diets due to less accretion of visceral organ mass resulting in reduced maintenance energy requirements during finishing.

Redberry juniper as a roughage source in lamb feedlot rations: performance and serum nonesterified fatty acids, urea nitrogen, and insulin-like growth factor-1 concentrations

Effects of replacing cottonseed hulls with dry redberry juniper leaves on performance and serum NEFA, urea N, and IGF-1 were investigated in Rambouillet lambs (n = 24, initial BW = 28.6 +/- 4.94 kg). In a study with 2 feeding periods (period 1 = 65% concentrate ration, 28 d; period 2 = 85% concentrate ration, 49 d), lambs were individually fed ad libitum treatment diets containing cottonseed hulls (control; CSH), one-half of the cottonseed hulls replaced by dry juniper leaves (CSHJ), or all the cottonseed hulls replaced by dry juniper leaves (JUN). Lamb BW was similar on d 0 and 14, but increasing juniper in the diet linearly reduced (P = 0.04) BW on d 28. Differences in BW during period 1 are attributed to ADG and average daily DMI linearly decreasing (P < 0.001) with increasing concentrations of juniper, with lambs fed CSH, CSHJ, or JUN diets having ADG of 0.34, 0.30, and 0.14 kg, respectively. Differences in average daily DMI are attributed to secondary compounds in the cottonseed hulls and juniper and nutrient-toxin interactions. Lambs fed CSHJ diets had the greatest (P = 0.04) G:F compared with lambs fed CSH and JUN during period 1. Lambs fed JUN diets tended to have the greatest (P = 0.09) NEFA concentrations during period 1, and increasing juniper in the diet linearly reduced (P = 0.006) serum urea N and IGF-1 on d 14 and 28, respectively. During period 2, intake and growth of lambs fed JUN diet rapidly increased, resulting in all lambs having similar ADG, DMI, G:F, and BW. When period 2 began (d 33), serum NEFA and urea N were similar (P > 0.12) among lambs, but serum IGF-1 tended to be linearly reduced (P = 0.09) by increasing juniper in the diet. At times during period 2, lambs fed CSHJ had the greatest (P < 0.02) serum urea N (d 40 and 82) and IGF-1 (d 54) concentrations. Results were interpreted to indicate that air-dried redberry juniper leaves can replace all of the cottonseed hulls in lamb feedlot rations. Feeding 30% juniper in the diet for a longer period of time during the initial feeding period probably would have further reduced growth performance.

Growth performance, carcass quality, and noncarcass components of indigenous Caribbean goats under varying nutritional densities

Studies were conducted to determine the effects of feeding regimens on growth and carcass quality of the Creole goat, a genotype indigenous to the Caribbean. Forty kids weighing 9.0 +/- 1.2 kg of BW were reared indoors after weaning. Four supplement amounts were compared (10 kids per treatment): the G0 group received the basal diet (tropical forage, 8.8 MJ of ME and 108 g of CP/kg of DM) without concentrate, whereas the G100, G200, and G300 groups were offered 130, 230, and 310 g/d of concentrate (13.6 MJ of ME and 209 g of CP/kg of DM), respectively, in addition to the basal diet. The kids were slaughtered according to the standard procedure at 22 to 24 kg of BW for assessment of carcass traits and meat quality. Total DMI increased significantly, from 51 to 78 g/kg of BW(0.75), for G0 to G300 kids, whereas their ADG doubled from 42 to 84 g/d (P < 0.01; P < 0.01, respectively). The G:F values reached 125 to 130 for the G200 and G300 diets and were satisfactory compared with literature values. The carcass weight and dressing percentage (P < 0.01) increased from group G0 to G300, from 9 to 13 kg and from 42 to 51%, respectively. The proportions of the different cuts (related to the carcass weight) did not vary by diet. The conformation score increased significantly (P < 0.05) among the 4 groups from an average score of 3.2 to 4.0 (score/5). There was a significant effect (P < 0.01) of supplement amount on the accumulation of internal fat tissues: the kidney fat weight increased from 113 to 253 g from the G0 to the G300 group. Regardless of the feeding level and amount of internal fat, the carcasses had an acceptable fat cover score, which remained less than 2.6 (score/5). A significant effect was not observed for the ultimate pH and the main color variables of the meat. The cooking loss and the shoulder DM content varied (P < 0.05) with the supplement amount. By increasing the nutritional density of the diet, it was possible to obtain well-conformed and heavy carcasses, with no excessive fattening. Indigenous Creole goats have potential as meat animals when fed to gain more than 80 g/d. The optimal supplement supply with good-quality grass would be approximately 3.69 MJ of ME/d in our conditions. Further studies are required on meat sensory parameters and fatty acid profiles.

Effects of dietary selenium supply and timing of nutrient restriction during gestation on maternal growth and body composition of pregnant adolescent ewes

The objectives were to examine effects of dietary Se supplementation and nutrient restriction during defined periods of gestation on maternal adaptations to pregnancy in primigravid sheep. Sixty-four pregnant Western Whiteface ewe lambs were assigned to treatments in a 2 x 4 factorial design. Treatments were dietary Se [adequate Se (ASe; 3.05 microg/kg of BW) vs. high Se (HSe; 70.4 microg/kg of BW)] fed as Se-enriched yeast, and plane of nutrition [control (C; 100% of NRC requirements) vs. restricted (R; 60% of NRC requirements]. Selenium treatments were fed throughout gestation. Plane of nutrition treatments were applied during mid (d 50 to 90) and late gestation (d 90 to 130), which resulted in 4 distinct plane of nutrition treatments [treatment: CC (control from d 50 to 130), RC (restricted from d 50 to 90, and control d 90 to 130), CR (control from d 50 to 90, and restricted from d 90 to 130), and RR (restricted from d 50 to 130)]. All of the pregnant ewes were necropsied on d 132 +/- 0.9 of gestation (length of gestation approximately 145 d). Nutrient restriction treatments decreased ewe ADG and G:F, as a result, RC and CR ewes had similar BW and maternal BW (MBW) at necropsy, whereas RR ewes were lighter than RC and CR ewes. From d 90 to 130, the HSe-CC ewes had greater ADG (Se x nutrition; P = 0.05) than did ASe-CC ewes, whereas ADG and G:F (Se x nutrition; P = 0.08) were less for HSe-RR ewes compared with ASe-RR ewes. The CR and RR treatments decreased total gravid uterus weight (P = 0.01) as well as fetal weight (P = 0.02) compared with RC and CC. High Se decreased total (g; P = 0.09) and relative heart mass (g/kg of MBW; P = 0.10), but increased total and relative mass of liver (P < or = 0.05) and perirenal fat (P < or = 0.06) compared with ASe. Total stomach complex mass was decreased (P < 0.01) by all the nutrient restriction treatments, but was reduced to a greater extent in CR and RR compared with RC. Total small intestine mass was similar between RC and CC ewes, but was markedly reduced (P < 0.01) in CR and RR ewes. The mass of the stomach complex and the small and large intestine relative to MBW was greater (P = 0.01) for RC than for CR ewes. Increased Se decreased jejunal DNA concentration (P = 0.07), total jejunal cell number (P = 0.03), and total proliferating jejunal cell number (P = 0.05) compared with ASe. These data indicate that increased dietary Se affected whole-body and organ growth of pregnant ewes, but the results differed depending on the plane of nutrition. In addition, the timing and duration of nutrient restriction relative to stage of pregnancy affected visceral organ mass in a markedly different fashion.

Circulating estradiol suppresses luteinizing hormone pulse frequency during dietary restriction

The influence of dietary restriction on the negative feedback potency of 17-beta-estradiol (E2) was evaluated in both castrated male (wethers) and female sheep (OVX ewes) during the breeding season. In study 1, OVX ewes received maintenance or restricted dietary energy for 7 weeks or maintenance energy for 6 weeks prior to a 5 day fast (n=12ewes/feeding group). Estradiol (0.31microg E2/50kg/h) or vehicle (10% EtOH-saline) was continuously infused into half the animals in each dietary treatment for the final 54h of the study. The dynamic pattern of LH secretion was assessed during the final 6h of infusion. Estradiol inhibited luteinizing hormone (LH) pulse amplitude independent of nutrition (P=0.02); fasting increased mean LH, LH peak height, and LH nadir in the absence of E2 (P=0.004, P=0.02, and P=0.02, respectively); while E2 inhibited pulse frequency (P=0.02) and increased peak width (P=0.04) in restricted ewes. Interestingly, despite uniform E2 delivery, serum concentrations of E2 differed with feeding status. Therefore, 12 wethers were infused with 0.31microg E2/50kg/h (6 fed, 6 fasted) and six wethers received 0.19microg E2/50kg/h (fasted) to establish similar serum concentrations of E2 in fed (0.31microg/50kg/h) and fasted (0.19microg/50kg/h) wethers. When fed and fasted wethers had uniform serum concentrations of E2 LH pulse frequency was suppressed (P<0.05) in fasted relative to fed animals, supporting the postulate that energy restriction enhances the E2 negative feedback potency. Collectively, these studies demonstrate that nutrition affects E2 feedback potency and clearance.

Influence of ruminal and postruminal carbohydrate infusion on visceral organ mass and adipose tissue accretion in growing beef steers1

Forty crossbred beef steers (243 +/- 2 kg of BW) with ruminal and abomasal infusion catheters were used to test 2 hypotheses: 1) visceral mass is responsive to energy input and site of carbohydrate (CHO) infusion and 2) rate and site of adipose accretion are dependent on site of CHO infusion and complexity. Treatments included a pelleted, forage-based, basal diet fed at 161 (LI) or 214 (HI) kcal of ME/(kg of BW(0.75) x d), LI plus ruminal (R-SH) or abomasal (A-SH) infusion of a partial starch hydrolysate (SH), and LI plus abomasal infusion of glucose (A-G). The basal diet was fed in 12 equal portions daily at 2-h intervals, with starch and glucose infused over a 22-h period at rates of 12.6 and 14.4 g/(kg of BW(0.75) x d). After 35 d of infusion, steers were slaughtered; and visceral organ and adipose mass, subcutaneous adipose thickness over the 5th and 12th rib, and LM intramuscular fat concentration were determined. Total intake energy (IE) increased (P = 0.0001) with ME intake. Dietary IE was similar between LI and CHO treatments, but total IE increased (P < 0.001) with CHO infusion. Greater dietary ME intake and CHO infusion increased or tended (P < or = 0.09) to increase final BW and HCW. As a percentage of empty BW, total stomach complex, rumen, omasum, liver, pancreas, and kidney weights were greater (P < or = 0.05) for HI vs. LI. Stomach complex, rumen, pancreas, and kidney weights as a percentage of empty BW were greater (P < or = 0.05) for R-SH vs. A-SH. Compared with ASH, A-G increased (P < or = 0.02) total and mucosal weights from the 10-cm sections of the ileum. Increases in rumen mass were associated with no change or an increase in rumen total and mucosal DNA concentrations. Greater dietary ME tended (P = 0.06) to increase subcutaneous fat thickness at the 5th rib but did not affect alimentary adipose accretion on an empty BW basis. Omental and total alimentary adipose weights were increased (P < or = 0.04) by A-G compared with A-SH. Although SH infusion did not alter adiposity, there was a consistent numerical pattern in total alimentary and subcutaneous fat depots with CHO infusion (A-G > ASH > R-SH). Our findings demonstrate that increasing ruminal CHO supply results in a disproportionate increase in rumen mass, whereas increasing small intestinal CHO supply does not alter gastrointestinal organ mass. Small intestinal energy in the form of glucose resulted in greater adipose accretion, particularly the omental depot.

Energy expenditure and restriction of energy intake: could energy restriction alter energy expenditure in companion animals?

The treatment of obesity in companion animals frequently focuses on restriction of energy intake. One important question with this treatment is whether dietary energy restriction (ER) produces a sustained decrease in mass-adjusted energy expenditure (EE), which prevents further weight loss and promotes rapid regain of body weight during lapses in dietary ER. This review summarizes studies that investigated the effects of dietary ER on EE at the whole-animal, organ, and cellular level. Whole-animal studies indicate that long-term dietary ER either decreases or does not affect mass-adjusted EE. The reason for this discrepancy between studies is not entirely clear, although analysis of data pooled from multiple studies suggests that a reduction in mass-adjusted EE with long-term ER would be observed if the sample size were sufficiently large and appropriate methods were used to adjust EE for body size. At the organ level, attempts were made to determine whether alterations in organ mass can entirely explain changes in EE with dietary ER. However, these studies were not conclusive, and it remains to be determined whether changes in EE exceed those that would be predicted from ER-induced alterations in organ mass. At the cellular level, there is evidence that dietary ER may induce sustained decreases in substrate oxidation, mitochondrial proton, and Na+-K+-ATPase activity in at least some tissues. These results are consistent with the idea that dietary ER may induce decreases in cellular EE. However, future studies integrating measurements at the whole-animal, organ, and cellular level will be required to determine definitively whether dietary ER produces sustained decreases in tissue or cellular EE.

Changes in heat production by mature cows after changes in feeding level1,2

We hypothesized that adaptation of heat production in the realimented cow would occur over an extended period, and the length of time would be influenced by the level of feed. Our objectives were to quantify the changes in heat production of cows after feed restriction and to quantify the effect of level of realimentation on the dynamics of heat production in lightweight cows. Forty 4-yr-old nonpregnant, nonlacting cows (4-breed composite: 1/4 Hereford, 1/4 Angus, 1/4 Red Poll, and 1/4 Pinzgauer) were randomly assigned to receive 1 of 4 levels of a common alfalfa hay source. All cows were feed-restricted [50.0 g of DM/metabolic body size (MBS, kg of BW(0.75)); period 1], and individual fed heat production measurements were taken 0, 7, 13, 28, 56, and 91 d after feed restriction (period 1). In period 2, cows were fed their assigned feed level for their treatment after d 91 of restriction: 50.0 (T50.0), 58.5 (T58.5), 67.0 (T67.0), and 75.5 (T75.5) g of DM/MBS. Measures were taken at 7, 13, 28, 42, 56, 91, 119, and 175 d. In period 3, all cows were fed 75.5 g of DM/MBS after their 175-d measurement, and measures were taken at 7, 14, 28, 56, and 112 d later. In period 1, heat production decreased rapidly during the first 7 d of feed restriction, and heat production continued to decrease during the 91-d restriction. Heat production increased rapidly within the first 7 d, but chronic adaptation continued for T75.5 and T67.0 cows. In period 3, heat production increased rapidly during the first 7 d. Heat production scaled for metabolic body size tended to differ among treatments (P = 0.11). Daily heat production increased by 2.5 kcal/d. These data suggest that there is not a lag in heat production during realimentation and that increased recovered energy is associated with a rapid increase in heat production.

The effect of dietary restriction, pregnancy, and fetal type in different ewe types on fetal weight, maternal body weight, and visceral organ mass in ewes

Our objectives were to evaluate maternal body changes in response to dietary restriction or the increased nutrient requirement of fetal growth. In Exp. 1, 28 mature crossbred ewes (61.6 +/- 1.8 kg initial BW) were fed a pelleted forage-based diet to evaluate effects of pregnancy and nutrient restriction on visceral organ mass. Treatments were arranged in 2 x 3 factorially, with dietary restriction (60% restriction vs. 100% maintenance) and reproductive status (nonpregnant [NP], d 90 or d 130 of gestation) as main effects. Dietary treatments were begun at d 50 of gestation, and restricted ewes remained at 60% of maintenance throughout the experiment. Nonpregnant and d-90 ewes were fed dietary treatments for 40 d and slaughtered. The d-130 ewes were fed dietary treatments for 80 d and then slaughtered. In Exp. 2, four Romanov ewes were naturally mated (Romanov fetus and Romanov dam; R/ R), and two Romanov embryos were transferred to each of four Columbia recipients (Romanov embryos and Columbia recipient; R/C). Three Columbia ewes were naturally mated (Columbia fetus and Columbia recipient; C/C). In both experiments, maternal organ weights were reported as fresh weight (grams), scaled to empty body weight (EBW; grams per kilogram) and maternal body weight (MBW; grams per kilogram). In Exp. 1, ewe EBW and fetal mass were decreased (P < 0.02) with restriction compared with maintenance. Dietary restriction decreased liver mass (16.7 vs. 14.5 g/kg EBW or 18.8 vs. 16.4 g/kg MBW; P < 0.01), but dietary restriction did not affect total digestive tract mass. In Exp. 2, ewe BW was less for the R/R compared with R/C and C/C (44.8 vs. 110.4 and 98.1 +/- 7.9 kg, respectively; P < 0.01). Fetal weight at d 130 was less for the R/R than for R/C and C/C (2.2 vs. 3.3 and 4.7 +/- 0.3 kg, respectively; P < 0.01) when measured as individual fetuses; however, when measured as total fetal mass carried in each ewe, there was no effect of ewe type. These data suggest that the gastrointestinal tract, along with other maternal organs, responds to both level of dietary intake and nutrient requirements for gestation, and that fetal weight is decreased as a result of a 40% decrease in nutrients offered.

Short-term dietary restriction modulates liver lipid peroxidation in carbon tetrachloride-intoxicated rats

We investigated whether dietary restriction (DR) can protect the liver against the acute toxicity of carbon tetrachloride (CCl4). Adult female Wistar rats received a quantum of diet representing 75 and 50 percent of the food intake of control rats fed ad libitum (25% and 50% daily regimen, respectively) for 30 days. A single dose of CCl4 (3 mL kg(-1) b.w.) was administered subcutaneously at the end of the feeding period. Lipid peroxidation, as thiobarbituric acid reactive substance, conjugated dienes, lipid hydroperoxides and the hepatic markers alanine transaminase, aspartic transaminase, and alkaline phosphatase were significantly decreased in food-restricted rats. The enzymic antioxidants superoxide dismutase, catalase, glutathione peroxidase and the non-enzymic antioxidant glutathione were significantly increased in both groups. The magnitude of liver damage after CCl4 treatment was lower in food-restricted animals than in ad libitum-fed animals. The results suggest that dietary restriction increases the resistance of the liver and protects against oxidative insult produced by an acute dose of CCl4.

Visceral Tissue Growth and Proliferation During the Bovine Lactation Cycle,

Twenty one multiparous, nonpregnant, lactating dairy cows were used to assess the impact of stage of lactation on visceral tissue mass and small intestinal cell proliferation. Cows were slaughtered at each of 4 stages of lactation: 14, 90, 120, and 240 d of lactation. With stage of lactation, DMI increased through d 90 and thereafter remained similar through d 240 (quadratic). Carcass weight and empty body weight (EBW) declined with stage of lactation through d 120 and increased thereafter (quadratic). As a percentage of EBW, rumen, small intestine, and liver weights increased with increasing stage of lactation (quadratic), increasing from 14 to 120 d and declining through 240 d. Stage of lactation did not have a measurable affect on reticulum, omasum, abomasum, or large intestine weights as a percentage of EBW. Visceral adipose mass as a percentage of EBW declined with stage of lactation to a minimum at 120 d and increased by 240 d (quadratic). Concentrations of RNA and DNA of digestive tract organs were largely unaffected by stage of lactation with the exception of the liver DNA concentration through d 120 (quadratic). The proliferative growth fraction (Ki67) was unaffected by stage of lactation. However, bromo-deoxyuridine labeling of jejunal crypts exhibited a cubic response with stage of lactation and tritiated thymidine incorporation by duodenal epithelium increased with stage of lactation through d 120, declining thereafter (quadratic). Mass of visceral tissues increase to meet the energetic demands of lactation and that increased absorption capacity of the intestines is achieved by hyperplastic growth of the intestinal epithelium.

Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing12

Two experiments were conducted using 48 Angus x Angus-Hereford steers in each experiment to determine the effect of previous winter grazing BW gain on jugular concentrations of metabolites and hormones during feedlot finishing. In each experiment, steers were randomly assigned to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) with 0.91 kg/d of a 41% CP (DM basis) supplement. Steers grazed for 120 or 144 d in Exp. 1 and 2, respectively. Plasma and serum were collected from all steers before placement into a feedlot, and six or seven times during finishing in Exp. 1 and 2, respectively. In Exp. 1, before steers entered the feedlot, concentrations of insulin, triiodothyronine (T3), and thyroxine (T4) were greater (P < 0.05) in HGW than in LGW or NR steers, and concentrations of IGF-I and plasma urea-N were greater (P < 0.05) in steers that grazed wheat pasture than in NR steers. In Exp. 2, concentrations of glucose, T3, T4, and IGF-I were greater (P < 0.05) in steers that grazed wheat pasture than NR steers. In Exp. 1 (P < 0.19) and 2 (P < 0.86), glucose concentration did not differ among treatments during finishing. In Exp. 1, insulin concentration across days on feed was greater for HGW than LGW steers, which were greater than for NR steers (treatment x day interaction, P < 0.03). In Exp. 2, insulin concentration increased (P < 0.001) as days on feed increased. Concentrations of IGF-I were greater in steers that had grazed wheat pasture, whereas the increase in IGF-I with increasing days on feed was greater for NR steers (treatment x day interaction, P < 0.003). Concentrations of T3 and T4 during finishing were greater (P < 0.001) in HGW and LGW than in NR steers in Exp. 1. In Exp. 2, T4 concentration also differed (P < 0.009) among treatments (HGW > LGW > NR). In Exp. 2, final concentration of glucose was greater (P < 0.01) in NR than in HGW and LGW steers, and serum insulin concentration was greater (P < 0.04) in NR than LGW steers. Final concentrations of T3 (P < 0.01) and T4 (P < 0.004) were greater in NR than in HGW steers. Our data show that previous BW gain can affect blood metabolites and hormones in steers entering the feedlot. However, lower concentrations of T3, T4, and IGF-I in steers when they entered the feedlot did not inhibit the growth response of previously restricted steers.

Effect of nitrogen intake on nitrogen recycling and urea transporter abundance in lambs

Urea recycling in ruminants has been studied extensively in the past, but the mechanisms regulating the amount of urea recycled or excreted remain obscure. To elucidate the role of urea transporters (UT) in N recycling, nine Dorset-Finn ewe lambs (20.8 +/- 0.8 kg) were fed diets containing 15.5, 28.4, and 41.3 g of N/kg of DM for 25 d. Nitrogen balance and urea N kinetics were measured during the last 3 d of the period. Animals were then slaughtered and mucosa samples from the rumen, duodenum, ileum, and cecum, as well as kidney medulla and liver, were collected. Increasing N intake tended to increase N balance quadratically (1.5, 5.1, and 4.4 +/- 0.86 g of N/d, P < 0.09), and linearly increased urinary N excretion (2.4, 10, and 16.5 +/- 0.86 g N/d, P < 0.001) and plasma urea N concentration (4.3, 20.3, and 28.4 +/- 2.62 mg of urea N/dL, P < 0.001), but did not affect fecal N excretion (5.0 +/- 0.5 g of N/d; P < 0.94). Urea N production (2.4, 11.8, and 19.2 +/- 0.83 g of N/d; P < 0.001) and urinary urea N excretion (0.7, 7.0, and 13.4 +/- 0.73 g N/d; P < 0.001) increased linearly with N intake, as well as with the urea N recycled to the gastrointestinal tract (1.8, 4.8, and 5.8 +/- 0.40 g of N/d, P < 0.001). No changes due to N intake were observed for creatinine excretion (518 +/- 82.4 mg/d; P < 0.69) and clearance (46 +/- 10.7 mL/min; P < 0.56), but urea N clearance increased linearly with N intake (14.9, 24.4, and 34.9 +/- 5.9 mL/min; P < 0.04). Urea N reabsorption by the kidney tended to decrease (66.3, 38.5, 29.1 +/- 12.6%; P < 0.06) with increasing N content of the diet. Increasing the level of N intake increased linearly the weight of the liver as a proportion of BW (1.73, 1.88, and 2.22 +/- 0.15%, P < 0.03) but only tended to increase the weight of the kidneys (0.36, 0.37, and 0.50 +/- 0.05%, P < 0.08). Urea transporter B was present in all the tissues analyzed, but UT-A was detected only in kidney medulla, liver, and duodenum. Among animals on the three diets, no differences (P > 0.10) in UT abundance, quantified by densitometry, were found. Ruminal-wall urease activity decreased linearly (P < 0.02) with increasing level of N intake. Urease activity in duodenal, ileal, and cecal mucosa did not differ from zero (P > 0.10) in lambs on the high-protein diet. In the present experiment, urea transporter abundance in the kidney medulla and the gastrointestinal tract did not reflect the increase in urea-N reabsorption by the kidney and transferred into the gut.

Effect of live weight gain of steers during winter grazing: II. Visceral organ mass, cellularity, and oxygen consumption1,2

Two experiments were conducted to examine the effect of BW gain during winter grazing on mass, cellularity, and oxygen consumption of splanchnic tissues before and after the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range supplemented with 0.91 kg/d of a 41% CP supplement (NR). At the end of winter grazing, four steers were selected randomly from each treatment for initial slaughter to measure organ mass, cellularity, and oxygen consumption. All remaining steers were placed into a feedlot and fed to the same backfat end point (1.27 cm). Six steers were selected randomly from each treatment for final organ mass, cellularity, and oxygen consumption. Initial empty BW (EBW) was greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both Exp. 1 and 2 (355 > 263 > 207 +/- 6.5 kg and 337 > 274 > 205 +/- 8.7 kg, respectively). For both experiments, the initial total gastrointestinal tract (GIT; g/kg of EBW) proportional weight was greater (P < 0.05) in NR steers than in LGW, and LGW steers had greater (P < 0.05) initial GIT proportional weight than HGW steers. Proportional weight of total splanchnic tissues (TST; g/kg of EBW) did not differ (P < 0.19) among treatments. Initial duodenal RNA concentration and RNA:protein were greater (P < 0.02) in LGW than in HGW steers, and NR steers were intermediate. Initial in vitro liver O2 consumption was greater (P < 0.09) in HGW and LGW than in NR steers (34.5 > 16.9 mL/min), whereas initial small intestinal oxygen consumption was greater (P < 0.01) in LGW than in HGW and NR steers (12.1 > 5.2 mL/min). Ruminal papillae oxygen consumption did not differ (P < 0.55) among treatments. The rate of decrease of GIT (g x g EBW(-1) x d(-1)) during finishing was greater in NR than in HGW and LGW steers in both Exp. 1 and 2, but mesenteric fat (g x g EBW(-1) x d(-1)) increased for NR steers, resulting in a similar (P < 0.75) increase in TST across the finishing period for all treatments. Similar rates of increase in TST across the finishing phase corresponded with similar rates of live and carcass weight gain among treatments. Our data support the hypothesis that increased visceral organ mass increases maintenance energy requirements of growing cattle.

Relationship between aging and nutritionally controlled growth rate on heat production of heifers

The first objective of this study was to test how well a function that was developed to describe heat production (HP) in growing ewes fit HP data in growing heifers. The second objective was to determine the pattern of adaptation of HP to feed restriction and subsequent realimentation of nutrients. At 234.5 +/- 0.5 d of age, HP was determined by indirect calorimetry on 32 Meat Animal Research Center III heifers. Following the first calorimetry measurement, heifers on the High-High (HH) treatment continued to receive ad libitum access to feed, and daily feed offered to the Low-High (LH) heifers was set at 157 Mcal of ME/kg of BW0.75. Feed restriction of LH heifers continued for 84 d. After 84 d of restriction, LH heifers were allowed ad libitum access to feed. Heat production was determined 4 and 11 wk following feed restriction and 2, 5, 12, and 18 wk following realimentation. There was no residual bias when HP in ad libitum-fed heifers was estimated with an equation form developed in growing ewes: [(kcal/d) = f(BW, matBW) = BW (Ae[k(BW/mature BW)])], nor was there a residual bias when HP was predicted with an allometric equation: [(kcal/d) = f(BW) = A(BWk)]. However, there were residual biases when HP was estimated with an allometric equation that set the exponent to 0.75. Heat production per unit of BW of LH heifers was lower than that of HH heifers at 4 wk of feed restriction (P < 0.001), but HP did not differ between treatments at 11 wk of feed restriction (P = 0.87). At 2 (P = 0.002) and 5 wk (P < 0.001) following the increase in feed offered, HP per unit of BW of the LH heifers was greater than that of the HH heifers. Heat production did not differ between treatments at 12 and 18 wk following refeeding (P < 0.17). Our findings demonstrate that the relationship between HP and BW is described equally well by a logistic and allometric function, but applying a generalized interspecies exponent in an allometric equation to growing heifers results in a bias in estimating HP. The equation form developed in ewes can be used to develop a single equation for the prediction of HP across ages in heifers.

The effect of pregnancy on visceral growth and energy use in beef heifers

Beef heifers (24 mo; 378 +/- 32 kg of BW; 22 pregnant, PR; 17 nonpregnant, NP) were grouped in common pens and fed corn silage- and hay-based diets formulated to provide an ADG of 0.45 kg in NP heifers. Both PR and NP heifers were slaughtered on d 40, 120, 200, and 270 of the study. Intestinal and hepatic tissues were analyzed for protein, DNA, RNA (mg/g of fresh tissue), and in vitro oxygen use. Jejunal samples were analyzed for cellular proliferation via immunohistochemical analysis. For ileum, DNA, which provides an estimate of cell number per unit of tissue, revealed an interaction (P = 0.06) between pregnancy and slaughter day; both PR and NP decreased with time, but NP increased on d 270 (P = 0.09). Cell number in the ileum was reduced at d 200 and 270 in the PR heifers (P < 0.09). Liver protein concentration was less (P = 0.07) in PR than in NP heifers (NP = 291.1 vs. PR = 210.5 +/- 33.9 mg/g). Hepatic protein:DNA ratio was not affected (P > 0.10) by pregnancy or day. Energy use (kcal/d) of duodenum and jejunum, calculated from in vitro oxygen consumption, increased linearly (P < 0.02) with time for both PR and NP. Pregnant and NP ileal energy use increased linearly (P < 0.01), but ileal energy use by PR was less throughout gestation (P = 0.07) than ileal energy use by NP. Cellular proliferation in the crypt region of the jejunum was decreased on d 120 and 200 (P < 0.02). These data indicate that the small intestine and liver of PR heifers may conserve energy expenditure compared with NP heifers. Energy conservation can partially be explained by differences in growth and cell proliferation and by energy use of the liver and small intestine.

Effect of GH and IGF-I treatment on reproduction, growth, and plasma hormone concentrations in domestic nutria (Myocastor coypus)

The role of GH and IGF-I in the control of reproduction, growth, and hormone secretion in domestic nutria was examined. In the first series of experiments, we studied the effects of single and multiple (daily for 20 days) injections of recombinant hGH (15 microg/animal) on plasma triiodothyronine (T3), thyroxine (T4), and progesterone (P) concentrations, as well as on the duration of pregnancy (time between start of mating and birth of pups), number of pups born, and body weight of adult females and their newborn pups. In the second series of experiments, the effects of single and multiple (daily for 28 days) injections of recombinant hIGF-I (1 microg/animal) on plasma IGF-I, IGFBP-3, T3, T4 concentrations, the duration of pregnancy, and number of offspring delivered were assessed. It was found that either single or multiple GH treatment resulted in significant increase in plasma T3, T4, but not P concentration. Furthermore, it significantly increased the body weight of adults and newborn pups. No influence of GH on the duration of pregnancy and the number of offspring was observed. IGF-I treatment caused an increase in plasma IGF-I concentration, a reduction in plasma IGFBP-3, T3, and T4 concentrations, and a shorter duration of pregnancy but did not alter the number of pups delivered. Our observations suggest that GH and IGF-I may be involved in the control of hormone secretion, growth, and reproduction in domestic nutria. Reproductive processes are controlled by IGF-I rather than by GH, whilst GH may be involved in the stimulation of prenatal and postnatal growth. The differential effects of these substances on thyroid hormones and reproductive parameters suggest that the actions of GH on these processes are probably not mediated by IGF-I.

Maternal protein restriction before pregnancy affects vital organs of offspring in Wistar rats

Epidemiologic studies indicate that undernutrition during fetal growth can have long-term effects on adult health. However, it is not known whether these effects are also associated with maternal undernutrition before conception. The objective of the present study was to examine the effect of dietary restriction before pregnancy on the vital organs and blood parameters of offspring at different time points. Wistar female rats in the restricted group were fed a diet consisting of 80 g protein/kg for 8 weeks before pregnancy and switched to 160 g protein/kg (control) from day 0 of pregnancy, while animals from the control group were fed 160 g protein/kg throughout life. The progeny were studied at birth (n = 71), at 94 days (n = 20), and at 180 days (n = 16). Weight gain during pregnancy was significantly lower (P <.01) for dams in the restricted group. At birth, relative weight for brain was lower (P </=.008), while for kidney it was higher (P </=.008) in the restricted group compared to control. At 94 days, the relative weights of brain, liver, and heart were lower (P </=.01 for all) in the restricted group than in the control group. However, at 180 days, only liver and kidney showed lower (P </=.01 for both) relative weights. Further, in the restricted group, increases in blood glucose at 94 days and in cholesterol at 180 days were significant (P <.01 for both) in the offspring. The results thus indicate that maternal undernutrition before conception not only affected growth of vital organs, but also resulted in increased levels of glucose and cholesterol in the offspring at adulthood.