The effects of different feeding strategies providing different levels of vitamin A on animal performance, carcass traits, and the conversion rate of subcutaneous fat color in cull-cows.

Cull cows represent a significant percentage of revenue received from the U.S. beef industry; however, cull cows are heavily price discounted at time of slaughter. This experiment's objective is to evaluate different feeding strategies and their effects on body condition score, subcutaneous fat color, and carcass yield and quality traits in cull cows. The central hypothesis is feeding a high-energy diet, with low levels of vitamin A, for 56 d will improve animal performance, carcass yield, and quality traits in addition to capturing the point (rate) of the conversion of yellow to white subcutaneous fat. In the present experiment 98 Angus crossbreed cows were utilized. Cows were fed either low vitamin A (LVA) diet consisting of whole shelled corn, soybean hulls, soybean meal, and a mineral-vitamin supplement or high vitamin A (HVA) diet, formulated using whole shelled corn, fescue hay, dry distiller grains with soluble, and a mineral-vitamin supplement for 56 d. During the 56 d feeding period, body weights and condition scores, and subcutaneous adipose samples were collected every 14 d. On day 56, cattle were slaughtered; 48 h postmortem carcass characteristics and objective color scores (subcutaneous adipose tissue) were recorded and a sample of the longissimus dorsi lumborum was collected. Subcutaneous adipose tissue samples were utilized to record subjective color scores and then ground to be analyzed for ß-carotene concentration. The longissimus dorsi lumborum samples (2.54 cm slices) were removed for Warner-Bratzler shear force (WBSF) and pH testing. Data were analyzed using the MIXED procedure of SAS. Feeding cull cows LVA resulted in differences in subcutaneous carcass fat color (P = 0.01) as well as b* values (P < 0.01) on day 56 compared with HVA. Subjective fat color scores were not different (P > 0.10) on day 0 or 14 but were different (P ≤ 0.05) on days 28, 42, and 56. Additionally, 9-cis-ß-carotene concentration on day 56 were different (P = 0.05) between treatments. A trend was noticed for all-trans-ß-carotene concentration (P = 0.10) on day 56 as well. Cull cow body weights were greater (P ≤ 0.04) when fed the LVA diet starting on days 14, 28, and 42; and a trend was noticed on day 56 (P = 0.09). Overall, cows fed the LVA treatment for 56 d exhibited decreased adipose yellowness and ß-carotene concentrations as well as increased live weights.

Localized mammary gland changes in milk composition and venous blood metabolite concentrations result from sterile subclinical mastitis.

Subclinical mastitis reduces milk yield and elicits undesirable changes in milk composition, but the mechanisms resulting in reduced milk production in affected mammary glands are incompletely understood. This study investigated the effects of sterile inflammation on mammary gland metabolism by assessing changes in milk and venous blood composition. Mid-lactation primiparous Holstein cows (n = 4) had udder halves randomly allocated to treatments; quarters of 1 udder half were infused with 2 billion cfu of formalin fixed Staphylococcus aureus (FX-STAPH) and quarters of the opposite udder half infused with saline (SAL). Blood samples were collected from the right and left subcutaneous abdominal veins in 2.6 h intervals until 40 h post challenge and analyzed for blood gas and metabolite concentrations. Milk from FX-STAPH udder halves had significantly increased SCS by first milking at 8 h post-challenge. By 16 h post-challenge, FX-STAPH udder halves had increased concentrations of protein and lactate and lower lactose concentrations than SAL udder halves. Milk fat concentrations, milk yields, energy corrected milk yields, and the ferric reducing antioxidant power of milk were not significantly different between SAL and FX-STAPH udder halves. Venous blood of FX-STAPH halves had marginally greater concentrations of saturated O2, partial pressures of O2, and glucose concentrations than SAL halves. Conversely, total and partial pressures of CO2 did not differ between udder half treatments suggesting a shift in local metabolite utilization in FX-STAPH udder halves. These results indicate that changes in milk composition resulting from mastitis are accompanied by changes in some key blood metabolite concentrations. The shift in venous blood metabolite concentrations, along with the marked increase in milk lactate, suggests that local mammary tissue and/or recruited and immune cells alters metabolite usage in mammary tissues. Future studies are needed to quantify the uptake of key milk precursors during mastitis.

Lipid metabolism mRNA expression and cellularity of intramuscular adipocytes within the Longissimus muscle of Angus- and Wagyu-sired cattle fed for a similar days on feed or body weight endpoint.

This study investigates intramuscular (IM) adipocyte development in the Longissimus muscle (LM) between Wagyu- and Angus-sired steers compared at a similar age and days on feed (D) endpoint or similar body weight (B) endpoint by measuring IM adipocyte cell area and lipid metabolism mRNA expression. Angus-sired steers (AN, n = 6) were compared with steers from two different Wagyu sires (WA), selected for either growth (G) or marbling (M), to be compared at a similar days on feed (DOF; 258 ± 26.7 d; WA-GD, n = 5 and WA-MD, n = 5) in Exp. 1 or body weight (BW; 613 ± 18.0 kg; WA-GB, n = 4 and WA-MB, n = 5) in Exp. 2, respectively. In Exp. 1, WA-MD steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GD steers. In Exp. 2, WA-MB steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GB steers. The distribution of IM adipocyte area was unimodal at all biopsy collections, with IM adipocyte area becoming progressively larger as cattle age (P ≤ 0.01) and BW increased (P ≤ 0.01). Peroxisome proliferator activated receptor delta (PPARd) was upregulated earlier for WA-MD and WA-MB cattle compared with other steers at a similar DOF and BW (P ≤ 0.02; treatment × biopsy interaction). Peroxisome proliferator activated receptor gamma was upregulated (PPARg) at a lesser BW for WA-MB steers (P = 0.09; treatment × biopsy interaction), while WA-MD steers had a greater (P ≤ 0.04) overall mean PPARg mRNA expression compared with other steers. Glycerol-3-phosphate acyltransferase, lipin 1, and hormone sensitive lipase demonstrated mRNA expression patterns similar to PPARg and PPARd or CCAAT enhancer binding protein beta, which emphasizes their importance in marbling development and growth. Additionally, WA-MD and WA-MB steers often had a greater early mRNA expression of fatty acid transporters (fatty acid transport protein 1; P < 0.02; treatment × biopsy interaction) and binding proteins (fatty acid binding protein 4) compared with other steers. Cattle with a greater marbling propensity appear to upregulate adipogenesis at a younger chronological and physiological maturity through PPARd, PPARg, and possibly adipogenic regulating compounds, lysophosphatidic acid, and diacylglycerol. These genes and compounds could be used as potential markers for marbling propensity of cattle in the future.

This study investigates intramuscular (IM) adipocyte development in the Longissimus muscle (LM) between Wagyu- and Angus-sired steers compared at a similar age and days on feed (D) or similar body weight (B) endpoint by measuring IM adipocyte cell area and lipid metabolism mRNA expression. Angus-sired steers (AN) were compared with steers from two different Wagyu sires (WA), selected for either growth (G) or marbling (M), to be compared at a similar days on feed (DOF; WA-GD, and WA-MD) in Exp. 1 or body weight (BW; WA-GB, and WA-MB) in Exp. 2. The WA-MD and WA-MB steers had a greater percentage of IM fat in the LM compared with AN and WA-GD and WA-GB steers. Intramuscular adipocyte cellularity analysis indicated few differences due to adipocyte size; therefore, marbling differences were likely due to adipocyte number. The WA-MD and WA-MB steers typically experienced an earlier or a greater mRNA upregulation for adipogenic genes that regulate fatty acid transport and triglyceride synthesis compared with other steers. The pattern of mRNA expression was very similar between steers compared at either a similar age and DOF or BW. Indicating that the timing of energy intake above maintenance requirements may be more influential than age for the upregulation of lipid metabolism in cattle.

Evaluation of the association between plasma glucose-dependent insulinotropic polypeptide, respiratory quotient, and intramuscular fat deposition in feedlot cattle fed different levels of dry matter intake.

The objectives of this trial were to evaluate the association between different levels of dry matter intake (DMI) on gas exchange, plasma glucose-dependent insulinotropic polypeptide (GIP) concentration, and intramuscular (IM) fat deposition. We used 60 individually fed backgrounded Angus × SimAngus-crossbred steers (n = 30) in a randomized complete block design. Steers (paired by body weight [BW] and gain to feed ratio [G:F]) were randomly allocated to one of the following treatments: ad libitum intake (AI) or restricted intake (RI; the same diet fed at 85% of the AI) of a finishing diet. The diet contained 61% cracked corn, 9% corn silage, 15% distillers' dried grains with solubles, 5% soyhulls, and 10% of a protein-mineral-vitamin premix. Measurements of CO2 emission and consumption of O2, and respiratory quotient (RQ) were taken using the GreenFeed system (n = 15/treatment). Plasma and gas samples were collected 10 d before slaughter, 1 h before and 2 h after feeding. Plasma glucose, non-esterified fatty acids, GIP, and insulin concentration and gasses (O2, CO2, and RQ) were analyzed using the MIXED procedure of SAS evaluating the fixed effect of treatment, time (repeated measurement) and their interaction, and the random effect of the block. Final BW and carcass characteristics were analyzed with a similar model, without the time statement and its interaction. Compared with RI, AI steers had greater (P < 0.01) DMI and average daily gain (ADG). Steers on AI had greater final BW (P = 0.02), tended to have a greater ribeye area (P = 0.09), and had lower plasma GIP concentration (P = 0.04). There was no treatment effect (P ≥ 0.11) on G:F, subcutaneous backfat (BF), and IM fat, O2 consumption, CO2 emission, and RQ. Plasma glucose concentration of AI steers was greater before and after feeding than RI (P < 0.05). In conclusion, feeding steers ad libitum increased DMI, ADG, and plasma glucose and GIP concentration but does not affect G:F, BF, IM fat, CO2 emission, and O2 consumption. Plasma GIP concentration and RQ are not associated with IM fat deposition.

Association of prepartum lying time with nonesterified fatty acids and stillbirth in prepartum dairy heifers and cows.

The objective of the present study was to assess the association of prepartum lying time (LT) and the coefficient of variation (CV) of LT within 7 d before calving with prepartum serum nonesterified fatty acid (NEFA) concentration at 7 ± 3 d prepartum (dpp) and stillbirth. Prepartum pregnant Holstein heifers and cows from 3 dairy herds were used (n = 1,044). Animals were housed in freestall barns using a prepartum pen 21 d before the expected calving date and were moved into a contiguous maternity pen at parturition. Monthly, cohorts of 20 to 36 animals (heifers and cows combined) were enrolled at each farm and electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) were fitted to the hind leg of individual animals to assess their behavioral activity. Stillbirth was defined as a calf born dead or died during the first 24 h after parturition in dams with normal gestation length. The LT was recorded for the last 7 dpp to assess differences among dams with stillbirth versus those with a calf born alive. Mean LT within 7 d before blood NEFA collection was assessed to determine the association with prepartum serum NEFA at 7 ± 3 dpp. Blood samples for the assessment of serum NEFA concentration were collected from prepartum animals at 14 ± 3 and at 7 ± 3 dpp. Blood samples for total serum calcium concentration were collected from postpartum cows within 48 h after parturition to assess differences among cows with stillbirth versus those with a calf born alive. Data were analyzed using CORR, MIXED, or GLIMMIX procedures of SAS (SAS Institute Inc., Cary, NC). Dams experiencing dystocic births had a greater proportion of stillbirth, but herd, parity, and season did not have an effect. Dams with a stillborn calf had reduced LT and increased CV of LT within the last 7 dpp compared with dams with a calf born alive, regardless of parity. Multiparous cows with a stillborn calf had higher prepartum serum NEFA concentration compared with multiparous cows with a calf born alive, but this did not differ for first-calf heifers. Regardless of parity, the proportion of postpartum cows with hypocalcemia was higher for dams with a stillborn calf compared with those with a calf born alive. Regardless of parity, LT of prepartum dams was strongly correlated with the CV of LT (as LT increased, the CV decreased), and prepartum dams with a mean LT between 11 and 15 h/d had the lowest serum NEFA concentration compared with dams with LT of 8 to 10 or >16 h/d. Serum NEFA concentrations at 7 ± 3 dpp was positively correlated with the CV of LT within 7 d before blood sample. These results show that the dam's prepartum LT and its consistency over time are associated with prepartum serum NEFA and calf survival at calving.

Short communication: pharmacokinetics of oxytocin administered intranasally to beef cattle.

Providing the neuropeptides oxytocin and vasopressin intranasally increased concentrations in plasma and cerebral spinal fluid in humans and primates, respectively. This is of interest because of the documented anxiolytic effects of oxytocin observed in humans and rodents. To date, a transnasal approach of hormone administration has not been investigated in beef cattle. Defining the pharmacokinetics of intranasal oxytocin in cattle is necessary for determining optimum sampling and dosing timelines for future investigations. Five, weaned Bos taurus steers were used in a 3 × 3 Latin square design. Treatments included 1) 0.33 IU oxytocin/kg BW (A, n = 5), 2) 0.66 IU oxytocin/kg BW (B, n = 5), and 3) 1.32 IU oxytocin/kg BW (C, n = 5). Steers were acclimated to handling and restraint procedures for 4 wk leading up to the start of the experiment. Frequent blood collection occurred every 2 min for the first 30 min and every 5 min for the second 30 min, relative to administration of intranasal treatment. No treatment by time interaction was detected; however, there was an effect of time (P < 0.001) and treatment (P = 0.002) on oxytocin concentrations over time. Pharmacokinetic parameters, determined by PKSolver excel add-in, demonstrated an average maximum concentration (CMAX) of 63.3 pg/mL at 3.5 min after intranasal dose administration. An average half-life (T1/2) of 12.1 min after intranasal administration was determined. Pharmacokinetic parameters to a single bolus were not dose-dependent.

Intranasal oxytocin treatment does not attenuate the hypothalamo-pituitary-adrenal axis in beef heifers subjected to isolation stress or restraint and isolation stress.

Changes in the physiological, psychological, and behavioral manifestations of stress have been observed in association with increases in circulating oxytocin (OXT). Providing OXT intranasally has been shown to attenuate stressor-induced hypothalamo-pituitary-adrenal (HPA) axis activation in humans and rodents; however, anxiolytic effects may be context and species specific. The present study aimed to investigate the effect of intranasal OXT supplementation on stressor-induced activation of the HPA axis in beef cattle. We hypothesized that OXT would attenuate activation of the HPA axis, ultimately decreasing plasma cortisol and adrenocorticotropic hormone (ACTH). Twenty-eight Bos taurus heifers were blocked by bodyweight and randomly allocated to one of four treatment groups, in a 2 × 2 factorial arrangement: (1) saline, isolated, standing, and unrestrained (S-isolation stress [IS], 0.015 mL/kg BW 0.9% isotonic saline, n = 7); (2) saline, isolated, and restrained (S-restraint and isolation stress [RIS]; 0.015 mL/kg BW 0.9% isotonic saline; n = 7); (3) OXT, IS (OXT-IS, 0.3 IU/kg BW oxytocin; n = 7); and (4) OXT and RIS (OXT-RIS, 0.3 IU/kg BW oxytocin; n = 7). Oxytocin and saline were administered intranasally. Intranasal treatments were given followed by a waiting time of 30 min when each of the stress treatments was applied for 2 h. Blood samples were collected via jugular catheters directly after stressor application and every 10 min thereafter, for 2 h. Cortisol concentrations increased over time in animals exposed to RIS (P < 0.01) and decreased over time in animals exposed to IS (P < 0.01). Concentrations of ACTH decreased over time for the IS-treated heifers but remained elevated for the RIS-treated heifers (P < 0.01). Under the conditions of the present study, OXT treatment did not affect measured indicators of HPA axis activation. A treatment × time interaction (P < 0.01) was detected for OXT, such that OXT heifers exhibited greater initial OXT concentrations followed by a decline; saline-treated heifers had consistently stable oxytocin concentrations. The RIS-treated heifers increased their glucose (P < 0.01) and lactate (P < 0.01) concentrations throughout the application of the stressors compared with the IS-treated heifers. Overall, restraint stress increased cortisol and oxytocin in B taurus heifers compared with heifers subjected only to isolation. Finding a more intermediate stress model may better allow for detection of the effects of oxytocin on the stress response.

Association between prepartum metabolic status and resumption of postpartum ovulation in dairy cows.

Cows transitioning from late gestation to early lactation experience an increase in energy demands, which lead to a negative energy balance (NEB) because the greater energy requirement is not fully synchronized with the intake of dry matter. In this context, there is an increase in plasma NEFA and ghrelin concentrations and a decrease in plasma insulin and glucose-dependent insulinotropic polypeptide (GIP) concentrations. This situation could have a negative impact on the return to cyclicity because some of these variables have been associated with reduced GnRH and LH pulsatility (high NEFA and low insulin concentrations). However, there are no studies showing the relationship between ghrelin or GIP and reproductive performance. It is known that these hormones are related with lipolysis and NEB, with NEB being one of the main determinants of GnRH pulse generator activity. Thus, the objective of the present study was to evaluate the association between plasma NEFA concentration and metabolic hormones (insulin, ghrelin, and GIP) before parturition and their associations with the resumption of postpartum ovulations in dairy cows. A completely randomized block design was used in a commercial dairy herd with sampling day (visit to farm) as the blocking criteria. Holstein cows (n = 92) were screened for plasma NEFA concentration -5 d (±2 d) relative to the expected parturition day, and top and bottom quartiles were considered as high (H-NEFA) and low (L-NEFA) NEFA groups. Data were analyzed with correlation, linear regression, and proportional hazard regression models. Plasma NEFA concentration (H-NEFA mean = 294 µM, SD = 141.2; and L-NEFA mean = 122 µM, SD = 25.3) was correlated (P < 0.01) with plasma insulin (r = -0.374) and ghrelin (r = -0.346) concentrations but not with plasma GIP concentration (P = 0.64). The greater the concentration of insulin, the lesser the prepartum NEFA concentration (for each 1 µU/mL of plasma insulin increase, there is a decrease of 1.223 ± 0.62 µM of NEFA). Plasma ghrelin and GIP concentrations were not associated with plasma NEFA concentration. Finally, H-NEFA prepartum cows were less likely to resume ovulation than L-NEFA cows (hazard ratio [HR] = 0.563, 95% confidence interval [CI] = 0.314-1.011), whereas high ghrelin cows were more likely to resume ovulation than low ghrelin cows (HR = 1.873, 95% CI = 0.846-4.145). Conversely, resumption of ovulation was not associated with prepartum insulin and GIP concentrations. Prepartum NEFA and possibly ghrelin are associated with the return to postpartum cyclicity; however, insulin and GIP are not related to the resumption of ovulation in dairy cows.

Associations of pre- and postpartum lying time with metabolic, inflammation, and health status of lactating dairy cows.

The objective was to evaluate the associations of pre- and postpartum lying time (LT) with serum total calcium (Ca), nonesterified fatty acids (NEFA), ß-hydroxybutyrate (BHB), and haptoglobin concentrations, hemogram, and health status of dairy cows. A total of 1,052 Holstein cattle (401 nulliparous heifers and 651 parous cows) from 3 commercial dairy farms were fitted with electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) on a hind leg 14 ± 3 d before parturition (dpp) and removed at 14 ± 3 d in milk (DIM) to assess their LT. Lying time data were summarized and reported daily (min/d or h/d). Serum concentrations of NEFA (at 14 ± 3 and 7 ± 3 dpp), total serum calcium within 48 h after calving, and BHB (at 7 ± 3 and 14 ± 3 DIM) were determined. Serum concentration of haptoglobin was determined and a hemogram was performed on a subsample of 577 cows (237 primiparous and 340 multiparous) at 7 ± 3 DIM. Cases of milk fever, retained placenta, metritis, mastitis, pneumonia, and digestive disorders within 30 DIM were recorded and cows were categorized into 1 of 4 groups: (1) nondiseased (ND, n = 613; cows without ketosis and any other health conditions); (2) cows with only ketosis (KET, n = 152); (3) sick cows experiencing ≥1 health conditions, but without ketosis (SICK, n = 198); or (4) cows with ketosis plus at least one other health condition (KET+, n = 61). Data were analyzed using mixed linear regression models or logistic regression (MIXED or GLIMMIX procedures). Lying time within 14 dpp had a significant positive quadratic association with serum NEFA concentrations at 14 ± 3 and 7 ± 3 dpp but was not significantly associated with serum Ca concentration within 48 h after calving. Lying time during the first 14 DIM after parturition had a significant linear association with the risk of ketosis within 14 DIM. For every 1-h increment in mean LT (from 8 to 15 h/d) within the first 14 DIM after calving, the risk of diagnosis with ketosis within 14 DIM increased by 3.7 percentage points. Regardless of parity, a greater proportion of KET and KET+ groups had increased serum prepartum NEFA concentration (≥400 µEq/L) and increased body condition loss from 14 dpp to 28 DIM compared with SICK and ND cows. A greater proportion of multiparous KET and KET+ cows had hypocalcemia within 48 h after calving compared with ND and SICK cows, but we did not detect a significant association between hypocalcemia and health status on primiparous cows. Multiparous KET+ cows had significantly reduced neutrophils and white blood cell count compared with ND cows, but lymphocytes did not differ. Regardless of parity, KET+ and SICK cows had significantly higher concentrations of serum haptoglobin compared with ND cows. These results suggest that LT along with energy and Ca balance are critical for transition cow health.

Associations of postpartum lying time with culling, milk yield, cyclicity, and reproductive performance of lactating dairy cows.

The objectives were to evaluate the associations of lying time (LT) during the first 14 d in milk (DIM) with milk yield, cyclicity (CYC), culling within 60 DIM (CULL), and reproductive performance of lactating dairy cows. A total of 1,052 Holstein cattle (401 nulliparous heifers and 651 parous cows) from 3 commercial dairy farms had electronic data loggers (IceQube, IceRobotics, Edinburgh, UK) placed on a hind leg 14 ± 3 d before the expected parturition date and removed at 14 ± 3 DIM to assess their LT. Serum concentrations of ß-hydroxybutyrate were determined at 7 ± 3 and 14 ± 3 DIM. Cases of retained placenta, metritis, mastitis, pneumonia, and digestive disorders within 30 DIM were recorded and lactating cows were categorized into 1 of 4 groups: (1) nondiseased (ND, n = 613; cows without ketosis or any other diagnosed health condition); (2) cows with only ketosis (KET, n = 152); (3) sick cows experiencing ≥1 health conditions but without ketosis (SICK, n = 198); or (4) cows with ketosis plus ≥1 health condition (KET+, n = 61). Ultrasound was performed at 28 ± 3 and 42 ± 3 DIM to assess ovarian cyclicity (presence or absence of corpus luteum). Milk yield at first Dairy Herd Improvement Association test was not associated with LT during the first 14 DIM, but it was negatively correlated with the coefficient of variation of LT during the first 14 DIM. Lactating dairy cows experiencing KET+ had the lowest milk yield compared with ND, regardless of parity. Parity, health status, and season were significantly associated with CYC and CULL. Lying time had a significantly linear association with the risk of being culled: for every 1-h increment of LT during 0 to 14 DIM, the risk of culling within 60 DIM increased by 1 percentage point. Lying time had a negative quadratic association with cyclicity at 42 DIM. Multiparous cows with a LT of 9 to 13 h/d had a significantly greater probability of pregnancy up to 300 DIM compared with cows with a LT >13 h/d. Regardless of parity, KET+ cows had significantly higher proportion of culling within 60 DIM and decreased probability of pregnancy up to 300 DIM compared with ND cows. These findings suggest that there is an optimum daily LT range for early postpartum cows housed in freestall barns, different from that reported for mid-lactation cows, with the potential for improved survival, health, and the overall performance (milk yield and reproduction).

Prepartum fatty acid supplementation in sheep I. Eicosapentaenoic and docosahexaenoic acid supplementation do not modify ewe and lamb metabolic status and performance through weaning.

Fatty acids are involved in the regulation of many physiological pathways, including those involved in gene expression and energy metabolism. Through effects on these pathways, fatty acids may have lifelong impacts on offspring development and metabolism via maternal supplementation. Therefore, our objective was to investigate the impact of supplementing a source of omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) during late gestation on productive and metabolic responses of ewes and their offspring. Eighty-four gestating ewes (28 pens) were blocked and randomly assigned to a diet with 0.39% added fat during the last 50 d of gestation (d -0). The fat sources were Ca salts of a palmitic fatty acid distillate (PFAD) or EPA + DHA. After lambing (d 1), all ewes and lambs were placed on the same pasture. The ewes were weighed and BCS was measured on d -50, -20, 30, and 60 (weaning) of the experiment. Blood samples were taken from the ewes on d -50, -20, 1 (lambing), 30, and 60. Milk yield and composition were measured at 30 d postpartum. Lambs were weighed and bled at d 1, 30, and 60, and ADG was calculated. All plasma samples were analyzed for glucose and NEFA. Ghrelin, prostaglandin E metabolites (PGEM), and the prostaglandin D2 metabolite 11ß-PGF2α were measured in d -20 ewe samples. Insulin and adropin were measured in lamb samples at d 60. There was no difference on ewe BW (P = 0.48) or BCS (P = 0.55), or plasma concentrations of glucose (P = 0.57), NEFA (P = 0.44), ghrelin (P = 0.36), PGEM (P = 0.32), and 11ß-PGF2α (P = 0.86) between ewes supplemented with PFAD or EPA + DHA. Neither milk yield nor its composition was different (P > 0.10) among treatments. Lambs born from ewes supplemented with PFAD or EPA + DHA did not have different BW (P = 0.22), ADG (P = 0.21) or plasma NEFA (P = 0.52), glucose (P = 0.50), insulin (P = 0.59), and adropin (P = 0.72) concentrations. These results suggest that supplementation of EPA and DHA during late gestation did not affect ewe metabolic profile or milk production. Lamb performance and metabolism through weaning were not affected by maternal supplementation with an enriched source of EPA and DHA.

Effects of increasing inclusion of sodium hydroxide treatment on growth performance, carcass characteristics, and feeding behavior of steers fed 50% DDGS.

Objectives were to determine the dietary inclusion level of NaOH in a dried distillers grains with solubles (DDGS)-based diet needed to improve growth performance and carcass characteristics of feedlot steers, and to determine the effects of NaOH treatment of DDGS on pattern of feed intake. Based on previous research regarding the acidity of DDGS, we hypothesized that using NaOH in cattle fed 50% DDGS-based diets to neutralize the acidity inherent in DDGS would improve growth performance of cattle but shift intake patterns. Angus-cross steers (120 total) were blocked into 2 BW blocks (light, initial BW = 211 ± 27 kg; and heavy, initial BW = 261 ± 27 kg) and allotted randomly within block to 20 pens (6 steers per pen; = 30). Pens within block were assigned randomly to 1 of 4 dietary treatments: 1) 50% DDGS, untreated; 2) 50% DDGS, treated with 0.5% NaOH (DM basis); 3) 50% DDGS, treated with 1.0% NaOH (DM basis); or 4) 50% DDGS, treated with 1.5% NaOH (DM basis). The remainder of the diets contained 20% dry-rolled corn, 20% corn silage, and 10% mineral and vitamin supplement, on a DM basis. Cattle were fed in a GrowSafe system. There were no effects ( ≥ 0.21) of increasing NaOH inclusion on final BW, ADG, or G:F. Increasing NaOH in the diet increased meal duration (linear; = 0.02) and tended to increase meal size (linear; = 0.06), but did not affect overall number of meals per day (linear; = 0.21) or overall DMI ( ≥ 0.40) for the course of the trial. Relative to cattle fed DDGS treated with 0, 0.5 or 1% NaOH (DM basis), steers fed DDGS treated with 1.5% NaOH consumed a larger proportion of their meals in the afternoon. However, regardless of treatment, all steers consumed 78% or more of their feed in the first 12 h post-feeding. There were no effects ( ≥ 0.19) of increasing NaOH inclusion on HCW, LM area, dressing percentage, KPH, back fat thickness, and marbling. There was a linear ( = 0.02) decrease in USDA Yield Grade (YG) 3 and a tendency ( = 0.09) for a quadratic response in carcasses grading USDA YG 4 as NaOH concentration increased in the diets; however, there were no other YG differences. The quality grade response followed marbling score and was not different ( ≥ 0.11) among treatments. Thus, there were no effects of feeding DDGS treated with NaOH on growing cattle performance or carcass characteristics. However, NaOH inclusion shifted the pattern of intake slightly to the afternoon hours, and increased meal duration without increasing the total number of meals per day.

Effects of sodium hydroxide treatment of dried distillers' grains on digestibility, ruminal metabolism, and metabolic acidosis of feedlot steers.

The objectives were to determine the optimum inclusion of NaOH necessary to buffer the acidity of dried distillers' grains with solubles (DDGS) and its effects on digestibility, ruminal metabolism, and metabolic acidosis in feedlot steers. Rumen cannulated Angus-crossed steers were blocked by BW (small: 555 ± 42 kg initial BW, = 4; large: 703 ± 85 kg initial BW, = 4) over four 21-d periods in a replicated 4 × 4 Latin square design. Steers were assigned to 1 of 4 dietary treatments: 1) 50% untreated DDGS, 2) 50% DDGS treated with 0.5% (DM basis) sodium hydroxide (NaOH), 3) 50% DDGS treated with 1.0% (DM basis) NaOH, and 4) 50% DDGS treated with 1.5% (DM basis) NaOH. The remainder of the diets, on a DM basis, was composed of 20% corn silage, 20% dry-rolled corn, and 10% supplement. Ruminal pH was not affected by treatments ( = 0.56) or by a treatment × time interaction ( = 0.15). In situ NDF and ruminal DM disappearance did not differ ( ≥ 0.49 and ≥ 0.47, respectively) among treatments. Similar to in situ results, apparent total tract DM and NDF digestibility were not affected ( ≥ 0.33 and ≥ 0.21, respectively) by increasing NaOH inclusion in the diets. Urinary pH increased (linear, < 0.01) with increasing NaOH concentration in the diet. Blood pH was not affected ( ≥ 0.20), and blood total CO and partial pressure of CO were similar ( ≥ 0.56 and ≥ 0.17, respectively) as NaOH increased in the diet. Increasing NaOH in the diet did not affect ( ≥ 0.21) ruminal concentrations of total VFA. There were no linear ( = 0.20) or quadratic ( = 0.20) effects of treatment on ruminal acetate concentrations, nor was there a treatment × time interaction ( = 0.22) for acetate. Furthermore, there were no effects ( ≥ 0.90) of NaOH inclusion on ruminal propionate concentration. However, there was a quadratic response ( = 0.01) of ruminal butyrate concentrations as NaOH inclusion increased in the diet; ruminal butyrate concentrations were greatest with the 0.5 and 1.0% NaOH treatments of DDGS. In the current study, feeding DDGS treated with NaOH did not increase fiber digestibility nor was it necessary to alleviate a possible metabolic acidosis. Alkali treatment of DDGS did not increase average ruminal pH or blood pH.

Short communication: plasma concentration of glucose-dependent insulinotropic polypeptide may regulate milk energy production in lactating dairy cows.

In dairy cows, an increase in plasma concentration of glucose-dependent insulinotropic polypeptide (GIP) is associated with an increase in metabolizable energy intake, but the role of GIP in energy partitioning of dairy cattle is not certain. The objective of this study was to examine the relationship between plasma GIP concentrations and energy partitioning toward milk production. Four mid-lactation, primiparous, rumen-fistulated Holstein-Friesian cows were fed a control diet of 55% forage and 45% concentrate [dry matter (DM) basis] in a 4×4 Latin square design with 4-wk periods. The 4 treatments were (1) control diet fed at 1000 and 1600h, and (2) once-daily (1000h) feeding, (3) twice-daily (1000 and 1600h) feeding, and (4) 4 times/d (1000, 1600, 2200 and 0400h) feeding of the control diet plus 1 dose (1.75kg on a DM basis at 0955h) into the rumen of supplemental vegetable proteins (Amino Green; SCA NuTec Ltd., Thirsk, UK). Measurements of respiratory exchange and energy balance were obtained over 4d during the last week of each period while cows were housed in open-circuit respiration chambers. Blood was collected from the jugular vein every 30min for 12h, using indwelling catheters, starting at 0800h on d 20 of each period. Plasma GIP concentration was measured in samples pooled over each 5 consecutive blood samplings. The relationships between plasma GIP, DM intake, heat production, respiratory quotient (RQ), milk yield, and milk energy output were analyzed using linear correlation procedures, with metabolizable intake as a partial variant. Plasma GIP concentration was not correlated with heat production, or milk yield, but was positively correlated with milk energy yield (correlation coefficient=0.67) and negatively correlated with RQ (correlation coefficient=-0.72). The correlations between GIP with RQ and milk energy output do not imply causality, but support a role for GIP in the regulation of energy metabolism in dairy cows.

Prepartum dietary energy source fed to beef cows: II. Effects on progeny postnatal growth, glucose tolerance, and carcass composition.

Mature Angus-cross beef cows (n = 228) were used to evaluate effects of prepartum dietary energy source on postnatal growth and carcass composition of progeny in a 2-yr study. Starting at approximately 160 d of gestation, cows were fed diets consisting of 1 of 3 primary energy sources: grass hay (HY), corn (CN), or dried corn distillers grains with solubles (DG). The CN and DG diets were limit-fed to achieve similar energy intakes as cows fed HY. Following parturition, cows were fed a common diet and managed as a single group. Calves were weaned at an average of 185 ± 6 d of age and backgrounded for 28 d. A subset of progeny (n = 134) was individually fed a common finishing diet until slaughter, when each calf reached 1.2 ± 0.05 cm of backfat. A glucose tolerance test (GTT) was conducted in year 2 on 4 calves/treatment after 41 and 111 d on the finishing diet (DOF). Calf birth weights were greater (P = 0.002) in calves from cows fed CN and DG than calves from cows fed HY, and weaning BW (P = 0.08) was less for calves from cows fed HY vs. CN. Receiving BW, final BW, and HCW did not differ (P ≥ 0.16) among treatments. No difference (P ≥ 0.28) in ADG, morbidity, and mortality from birth to slaughter was observed among treatments. In response to a GTT, increased DOF resulted in greater (P ≤ 0.005) fasting insulin, faster glucose disappearance rate, and greater insulin:glucose area under the curve ratio. Glucose disappearance rate was greater (P = 0.01) in calves from cows fed CN than in calves from cows fed HY or DG. A greater initial insulin response (P = 0.005) was observed in calves from cows fed CN or DG than in calves from cows fed HY. Carcass traits used to measure yield grade did not differ (P ≥ 0.19) among treatments. Calves from dams fed CN had the lowest marbling score (P = 0.03) and intramuscular fat content (P = 0.07). These results indicate that prepartum maternal dietary energy source can alter fetal adipose tissue development and insulin sensitivity resulting in long-term effects on progeny's intramuscular fat deposition. Moreover, present findings suggest that increasing the number of days on a corn-based finishing diet increases insulin resistance in beef cattle.

Effects of glucose, propionate and splanchnic hormones on neuropeptide mRNA concentrations in the ovine hypothalamus.

The capacity for glucose, propionate or hormones of splanchnic origin to influence appetite by directly regulating the expression of neuropeptides in the feeding centres of the hypothalamus of the ruminant is not described. Therefore, our objective was to measure the direct effect of metabolites (glucose and propionate) or hormones [insulin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) and polypeptide YY (PYY)] on hypothalamic mRNA concentrations for neuropeptide Y (NPY), agouti-related peptide (AgRP) and proopiomelanocortin (POMC) following in vitro incubation. Hypothalamic tissue from 4- to 5-month-old lambs was obtained at slaughter and immediately incubated in culture media for 2 h at 36 °C. Treatments included a control Dulbecco's modified Eagle medium (DMEM) containing 1 mm glucose or DMEM with the following additions: 10 mm glucose, 1 mm propionate, 1 nm insulin, 120 pm GLP-1, 100 pm PYY, 80 pm CCK or 10 mm glucose plus 1 nm insulin. The abundance of mRNA for NPY, AgRP and POMC was measured using quantitative reverse transcriptase PCR. Fisher's protected LSD test was used to compare changes in relative mRNA concentrations for the hypothalamus incubated in the control media vs. the rest of the treatments. The media containing glucose plus insulin increased POMC mRNA concentration (p <0.05), but did not affect NPY or AgRP mRNA concentration. There were no effects observed for the other treatments (p > 0.20). Results of the present study are consistent with the concept that effects of propionate on feed intake in ruminants is not mediated through direct effects on the hypothalamus, and that insulin is required for an effect of glucose on hypothalamic POMC expression.

Effect of feeding fat or intrajugular infusion of glucagon-like peptide-1 and cholecystokinin on dry matter intake, digestibility, and digesta rate of passage in growing wethers.

A cause and effect relationship between glucagon-like peptide 1 (7, 36) amide (GLP-1) and cholecystokinin (CCK) and DMI regulation has not been established in ruminants. Three randomized complete block experiments were conducted to determine the effect of feeding fat or infusing GLP-1 or CCK intravenously on DMI, nutrient digestibility, and Cr rate of passage (using Cr(2)O(3) as a marker) in wethers. A total of 18 Targhee × Hampshire wethers (36.5 ± 2.5 kg of BW) were used, and each experiment consisted of four 21-d periods (14 d for adaptation and 7 d for infusion and sampling). Wethers allotted to the control treatments served as the controls for all 3 experiments; experiments were performed simultaneously. The basal diet was 60% concentrate and 40% forage. In Exp. 1, treatments were the control (0% added fat) and addition of 4 or 6% Ca salts of palm oil fatty acids (DM basis). Treatments in Exp. 2 and 3 were the control and 3 jugular vein infusion dosages of GLP-1 (0.052, 0.103, or 0.155 µg•kg of BW(-1)•d(-1)) or CCK (0.069, 0.138, or 0.207 µg•kg of BW(-1)•d(-1)), respectively. Increases in plasma GLP-1 and CCK concentrations during hormone infusions were comparable with increases observed when increasing amounts of fat were fed. Feeding fat and infusion of GLP-1 tended (linear, P = 0.12; quadratic, P = 0.13) to decrease DMI. Infusion of CCK did not affect (P > 0.21) DMI. Retention time of Cr in the total gastrointestinal tract decreased (linear, P < 0.01) when fat was fed, but was not affected by GLP-1 or CCK infusion. In conclusion, jugular vein infusion produced similar plasma CCK and GLP-1 concentrations as observed when fat was fed. The effects of feeding fat on DMI may be partially regulated by plasma concentration of GLP-1, but are not likely due solely to changes in a single hormone concentration.

Effect of abomasal glucose infusion on plasma concentrations of gut peptides in periparturient dairy cows.

Six Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in the portal vein, hepatic vein, mesenteric vein, and an artery were used to study the effects of abomasal glucose infusion on splanchnic plasma concentrations of gut peptides. The experimental design was a randomized block design with repeated measurements. Cows were assigned to one of 2 treatments: control or infusion of 1,500 g of glucose/d into the abomasum from the day of parturition to 29 d in milk. Cows were sampled 12 ± 6 d prepartum and at 4, 15, and 29 d in milk. Concentrations of glucose-dependent insulinotropic polypeptide, glucagon-like peptide 1(7-36) amide, and oxyntomodulin were measured in pooled samples within cow and sampling day, whereas active ghrelin was measured in samples obtained 30 min before and after feeding at 0800 h. Postpartum, dry matter intake increased at a lower rate with infusion compared with the control. Arterial, portal venous, and hepatic venous plasma concentrations of the measured gut peptides were unaffected by abomasal glucose infusion. The arterial, portal venous, and hepatic venous plasma concentrations of glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1(7-36) amide increased linearly from 12 d prepartum to 29 d postpartum. Plasma concentrations of oxyntomodulin were unaffected by day relative to parturition. Arterial and portal venous plasma concentrations of ghrelin were lower postfeeding compared with prefeeding concentrations. Arterial plasma concentrations of ghrelin were greatest prepartum and lowest at 4 d postpartum, giving a quadratic pattern of change over the transition period. Positive portal venous-arterial and hepatic venous-arterial concentration differences were observed for glucagon-like peptide 1(7-36) amide. A negative portal venous-arterial concentration difference was observed for ghrelin pre-feeding. The remaining portal venous-arterial and hepatic venous-arterial concentration differences of gut peptides did not differ from zero. In conclusion, increased postruminal glucose supply to postpartum transition dairy cows reduced feed intake relative to control cows, but did not affect arterial, portal venous, or hepatic venous plasma concentrations of gut peptide hormones. Instead, gut peptide plasma concentrations increased as lactation progressed. Thus, the lower feed intake of postpartum dairy cows receiving abomasal glucose infusion was not attributable to changes in gut peptide concentrations.

Plasma ghrelin and oxyntomodulin concentrations in lactating dairy cows receiving abomasal soybean oil, corn starch, and casein infusions.

The effects of increased postruminal supply of casein, corn starch, and soybean oil on plasma concentrations of the gastrointestinal hormones ghrelin and oxyntomodulin (OXM) were investigated. Four mid-lactation Holstein cows were used in a 4 x 4 Latin square. Treatments were continuous abomasal infusions (23 h/d) for 7 d of water, soybean oil (500 g/d), corn starch (1100 g/d), or casein (800 g/d). Jugular vein plasma was obtained every 30 min for 7h on days 1 and 7. Soybean oil and casein infusion decreased preprandial plasma ghrelin concentration by approximately 20% on both d (time-by-treatment P<0.10); however, dry matter intake (DMI) was depressed only after 7 d of oil infusion. Infusion of soybean oil, corn starch, or casein did not change the plasma OXM concentration (P>0.20). The present data indicate that plasma ghrelin concentration is depressed immediately before feeding by the postruminal infusion of soybean oil and casein, but it is not affected during the postprandial period. Plasma ghrelin concentration was not altered (P>0.20), pre- or postfeeding, by increased postruminal supply of corn starch. In addition, plasma OXM concentration did not respond (P>0.20) to postruminal nutrient infusion. In conclusion, a decrease in DMI when fat is infused could be partially explained by the decrease in prefeeding plasma ghrelin concentration, but a decrease in prefeeding plasma ghrelin concentration is not always associated with a decrease in DMI, as observed for the infusion of casein. Plasma OXM concentration was not affected by postruminal infusion of macronutrients.

Effect of feed restriction and supplemental dietary fat on gut peptide and hypothalamic neuropeptide messenger ribonucleic acid concentrations in growing wethers.

The objectives of the present study were 1) to evaluate the effects of supplemental fat and ME intake on plasma concentrations of glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide, ghrelin, and oxyntomodulin; and 2) to determine the association of these peptides with DMI and the hypothalamic concentration of mRNA for the following neuropeptides: neuropeptide Y (NPY), agouti-related peptide (AgRP), and proopiomelanocortin (POMC). In a completely randomized block design with a 2 x 2 factorial arrangement of treatments, 32 pens with 2 wethers each were restricted-fed (2.45 Mcal/lamb per day) or offered diets ad libitum (n = 16) with or without 6% supplemental fat (n = 16) for a period of 30 d. Dry matter intake was measured daily. On d 8, 15, 22, and 29, BW was measured before feeding, and 6 h after feeding, blood samples were collected for plasma measurement of insulin, GLP-1, CCK, ghrelin, glucose-dependent insulinotropic polypeptide, oxyntomodulin, glucose, and NEFA concentrations. On d 29, blood was collected 30 min before feeding for the same hormone and metabolite analyses. At the end of the experiment, wethers were slaughtered and the hypothalami were collected to measure concentrations of NPY, AgRP, and POMC mRNA. Offering feed ad libitum (resulting in greater ME intake) increased plasma insulin and NEFA concentrations (P = 0.02 and 0.02, respectively) and decreased hypothalamic mRNA expression of NPY and AgRP (P = 0.07 and 0.02, respectively) compared with the restricted-fed wethers. There was a trend for the addition of dietary fat to decrease DMI (P = 0.12). Addition of dietary fat decreased insulin and glucose concentrations (P < 0.05 and 0.01, respectively) and tended to increase hypothalamic mRNA concentrations for NPY and AgRP (P = 0.07 and 0.11, respectively). Plasma GLP-1 and CCK concentrations increased in wethers offered feed ad libitum compared with restricted-fed wethers, but the response was greater when wethers were offered feed ad libitum and had supplemental fat in the diet (fat x intake interaction, P = 0.04). The prefeeding plasma ghrelin concentration was greater in restricted-fed wethers compared with those offered feed ad libitum, but the concentrations were similar 6 h after feeding (intake x time interaction, P < 0.01). Supplemental dietary fat did not affect (P = 0.22) plasma ghrelin concentration. We conclude that insulin, ghrelin, CCK, and GLP-1 may regulate DMI in sheep by regulating the hypothalamic gene expression of NPY, AgRP, and POMC.