Search

To obtain measurements of energy balance in lactating beef cows, respiration calorimetry and digestion trials were conducted using seven lactating (613 kg BW) and three nonlactating (598 kg BW) Hereford x Angus heifers fed a pelleted 75% alfalfa:25% concentrate diet. Five measurements of energy balance were obtained at 6- to 7-wk intervals beginning 6 to 10 wk postpartum in lactating heifers and at 6-wk intervals in nonlactating heifers. Milk yield was measured using a combination of weigh-suckle-weigh and machine milking to adapt heifers to milking by machine without the use of oxytocin. Heifers were milked only by machine during measurements of energy balance. Weekly milk yield averages ranged from 8.2 kg/d at wk 5 postpartum to 3.2 kg/d at wk 32 postpartum. When scaled to [BW.sup..75], the regression of [NE.sub.1] on ME intake and the regression of ME intake on [NE.sub.1] were remarkably similar to previously published regressions for measurements obtained from lactating Holstein-Friesian cows. The average daily maintenance energy requirement from these regressions was 503 kJ ME/kg [BW.sup..75], a value similar to the average value reported previously for lactating Holstein-Friesian cows (488 kJ/kg [BW.sup..75]). This is in contrast to numerous published comparisons of the maintenance requirements of cattle breed types in the nonlacting state and current NRC standards for estimating maintenance energy requirements of beef and dairy cattle. The results of the present study suggest that when expressed on the basis of [BW.sup..75] the efficiency of utilization of incremental ME above maintenance for milk and tissue energy (i.e., [NE.sub.1]) is similar among lactating Hereford x Angus heifers and lactating Holstein-Friesian cows. The breeds differ in terms of their propensity for milk yield and the resulting partition of ME between milk synthesis and tissue energy retention. Key Words: Beef Cows, Breed Differences, Energy Metabolism, Lactation

Lambs (n = 48) were used in a 2 × 2 factorial arrangement of treatments to evaluate effects of inclusion of oil containing PUFA in high-concentrate diets (with or without) and duration of oil supplementation (pre- vs. postweaning) on CLA concentration of muscle and adipose tissue. Lambs were fed preweaning creep diets (with or without oil) corresponding to the dietary lactation treatment diet (with or without oil) of the dam. Dams blocked by lambing date and rearing type were randomly assigned to 1 of 2 lactation dietary treatments with or without oil supplementation, Creep diets contained approximately 70% concentrate and 30% roughage and were provided to lambs for ad libitum intake. At weaning (58.7 ± 2.5 d of age), lambs (n = 48) were randomly assigned within preweaning treatment groups to 1 of 2 postweaning dietary treatments (with or without oil) and 16 pens in a randomized block design, blocked by sex and BW. Postweaning diets were formulated to contain approximately 80% concentrate and 20% roughage and were fed once daily for ad libitum intake. Soybean and linseed oil (2:1, respectively) replaced ground corn and provided 3% additional fat in pre- and postweaning diets. Lambs were slaughtered at 60.3 ± 4.2 kg of BW. A subcutaneous fat (SQ) sample was obtained within 1 h postmortem and a LM sample at the 12th rib was obtained 24 h postmortem, and both were analyzed for fatty acid profile. Feedlot performance and carcass measurements were not affected (P ≥ 0.26) by oil supplementation. Total CLA content of LM and SQ was not affected (P ≥ 0.08) by oil supplementation pre- or postweaning, but trans-10, cis-12 CLA was greater (P = 0.02) in SQ from lambs supplemented with oil postweaning. Total PUFA content in LM was greater (P = 0.02) in lambs supplemented with oil pre- or postweaning as a result of increased concentrations of 18:2cis-9, cis-12 and longer chain PUFA. Conversely, pre- and postweaning oil supplementation resulted in less (P = 0.04) MUFA content in LM. Only postweaning oil supplementation increased (P = 0.001) SQ PUFA content. Feeding oils containing PUFA to lambs pre- and postweaning did not increase CLA content of muscle, whereas postweaning oil supplementation minimally increased CLA concentration of SQ fat. Inclusion of soybean and linseed oil in pre- and postweaning diets increased total PUFA content of SQ fat and muscle tissue without adversely affecting growth performance or carcass characteristics. [ABSTRACT FROM AUTHOR]

The effect of nutrient supply to the small intestine on gut peptide secretion in ruminants, and particularly cattle, has not been characterized. The objective of the present study was to determine the effects of abomasal infusion of macronutrients on DMI and plasma concentrations of glucagon-like peptide-1 (GLP1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (CCK). Four rumen cannulated Holstein cows fed a ration containing (DM basis) 17 % alfalfa haylage, 38 % corn silage and 45 % concentrate were used in a 4 X 4 Latin square design with 2-wk periods. Treatments were 7 d abomasal infusions of water (12 kg/d), soybean oil (500 g/d), starch (1100 g/d), or casein (800 g/d). Hormone concentrations (pmol/L, Table 1) were measured in plasma from jugular vein samples (15/d at 30 min intervals) taken during day 1 and 7 of infusions. Oil infusion decreased DMI (kg/d), but not ME, decreased CCK concentration, and increased GLP1 concentration on day 7. Casein and starch infusion had no effect on DMI, but ME and GIP concentration were increased on day 1 and 7. Casein infusion increased CCK concentration on day 1 and 7. Increased GIP concentration with increased ME may be related to effects of this peptide on adipose synthesis. [ABSTRACT FROM AUTHOR]

Adding fat to lactating dairy cow diets often decreases DMI, but the extent of the decrease varies, in part due to the iodine value of the fat fed. Our objective was to determine the effect of feeding rumen-inert fats differing in degree of saturation on DMI and plasma concentrations of insulin, glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (CCK) in lactating dairy cows. Four mid-lactation, primiparous, Holstein cows were fed a control ration containing (DM basis) 17 % alfalfa haylage, 38 % corn silage and 45 % concentrate in a 4 X 4 Latin square design with 2-wk periods. Treatments were the addition of 3 rumen-inert fats at 3.5 % of ration DM comprised of mostly saturated (SFA), monounsaturated (MUFA) or polyunsaturated (PUFA) fatty acids. Hormone concentrations (pmol/L, Table 1) were measured in jugular vein plasma samples taken at 30 min intervals (15/d) on day 12 and 14. Feeding fat decreased DMI (d 11 - 14) and insulin concentration and increased GLP1 concentration, and the effect was greater for MUFA and PUFA vs. SFA. Feeding fat also increased CCK concentration, and the effect was greatest for MUFA. Degree of saturation determines the extent to which dietary fat decreases DMI in dairy cows, and the response is associated with changes in plasma concentrations of gut peptides. [ABSTRACT FROM AUTHOR]

To determine the effect of the duration of dietary vitamin A restriction on the site of fat deposition in growing cattle, 60 Holstein steers (BW = 219.1 kg) were fed a high-moisture corn-based diet with 2,200 IU supplemental vitamin A/kg DM (C) or no supplemental vitamin A for a long (243 d; LR) or short (131 d; SR) restriction before harvest at 243 d. The SR steers were fed the C diet for the first 112 d. Steers were penned individually and feed was offered ad libitum. Jugular vein blood samples for serum retinol analysis were taken on d 1, 112 and 243. Feedlot performance (ADG, DMI and G:F) was not affected (P > 0.05) by vitamin A restriction. At the end of the experiment, the intramuscular fat content of the longissimus muscle was 33% greater (P < 0.05) for LR vs. C steers (5.6 vs. 4.2% Ether extractable fat (EE), respectively), while EE of the longissimus muscle of SR steers was 3.9%. Depth of BF and KPH percentage were not affected (P = 0.44 and 0.80, respectively) by vitamin A restriction. Marbling scores were numerically greater for the LR steers (LR = 433.8, SR = 370.6, C = 401.7; P = 0.36). Carcass weight, composition of edible carcass and YG were similar among treatments (P > 0.10). Liver (LR = 6.1, SR = 6.5, and C = 44.7 µg/g; P < 0.01) but not subcutaneous fat retinol (LR = 0.5, SR = 0.7, and C = 0.6 µg/g; P = 0.33) was reduced in LR and SR steers. Vitamin A restriction reduced (P < 0.01) serum retinol by d 112 (LR = 2.8, SR = 4.2, and C = 3.8 µg/dL). On d 243, LR and SR steers had similar serum retinol levels and these were lower (P < 0.01) than those of C steers (LR = 2.1, SR = 2.5, and C = 3.7 µg/g). These results suggest that serum and liver retinol levels can be reduced feeding a low vitamin A diet for 112 d. Restricting vitamin A intake for 243 d increased intramuscular fat percentage without affecting subcutaneous or visceral fat deposition, feedlot performance, or carcass weight. Restricting vitamin A intake for 131 d or less appears to be insufficient to affect the site of fat deposition in Holstein steers. [ABSTRACT FROM AUTHOR]

Meeting the energy demands of the transition dairy cow is challenging. Cows often decrease DMI before calving, causing negative energy balance (EB). Limit feeding dry cows a high energy diet may enable adequate DM and energy intake and reduce the extent of negative EB at calving. Multiparous Holstein cows (n = 18), dried off 45 d before expected calving and paired by expected calving date, parity, and previous milk yield, were randomly assigned to dry period diets formulated to meet nutrient requirements at ad libitum (AL) or restricted (R) DMI. All cows had ad libitum access to the same diet after calving. Blood samples were taken weekly from the coccygeal vein. Data were statistically analyzed as repeated measures within cows. Prepartum DMI for R cows was 9.4 kg/d, vs. 13.7 kg/d for AL cows (P < 0.01). Prepartum EB (0.02 vs. 6.37 Mcal/d, P < 0.01) and BW (756 vs. 773 kg, P < 0.10) were higher for AL cows, but BCS did not differ (3.58, P = 0.56). For 4 wk after calving, prepartum diet did not affect DMI (19.4 kg/d, P = 0.36), BW (678 kg, P = 0.77), BCS (3.21, P = 0.40), milk yield (41.5 kg/d, P = 0.75), milk protein concentration (3.26 %, P = 0.42) or milk lactose concentration (4.55 %, P = 0.24). Cows fed R had higher EB during week 1 after calving (-10.9 vs. -17.7 Mcal/d, P < 0.10). Milk fat concentration and yield were greater in the first week after calving for AL vs. R (6.63 vs. 4.39 %; 1.22 vs. 1.90 kg/day), but were lower for AL during wk 2 and 3 after calving (P < 0.01). Prepartum plasma glucose was lower (P = 0.08) for R vs. AL (3.5 vs. 3.7 mM), but prepartum insulin (0.22 nM) did not differ by treatment (P = 0.38). After calving, both insulin and glucose concentrations decreased (P < 0.01) and glucose was lower (P = 0.03) for R vs. AL (2.5 vs. 2.9). Postpartum insulin (0.08) did not differ by dry-period diet (P = 0.55). In conclusion, restricted intake of a high energy diet during a 45 d dry period does not adversely affect the milk production or intake of the postpartum dairy cow. [ABSTRACT FROM AUTHOR]

The objective was to determine the effect of feeding soybean oil (SO) and high corn silage (CS) diets on feedlot performance and carcass characteristics in beef steers. Angus based-steers (n = 168; BW = 287 kg) were allotted to 24 pens (7 steers each) and assigned to one of 6 treatments (4 pens each) based on 3 forage regimens with or without SO supplementation in a 3 X 2 arrangement of treatments. Forage regimens (8 pens each) were low CS diets for the entire finishing period (LO) or high CS diets for 126 (HILO) or 210 (HI) d, followed by LO until slaughter. Within each forage regimen 4 pens were fed SO (5 % of diet DM) for the entire study. There were no implants or ionophores used. Steers were harvested when s.c. back fat depth by ultrasound (pen mean) was 1 cm. Final BW (Table) increased (P < 0.01) with greater CS and SO. Increasing CS decreased ADG (P < 0.01). Feeding SO tended to decrease ADG for HI-LO and HI, but not LO (P < 0.08). DMI was greater for LO (P < 0.01) compared to HI-LO and HI, was reduced by SO (P < 0.01), and the reduction was less for LO (P < 0.04). Gain/kg feed DM was decreased (P < 0.01) with increased CS and increased (P < 0.01) by SO. Dressing % (61.3) and marbling score (569) were not affected by treatments, but kidney, heart and pelvic fat % was reduced (P < 0.02) by SO (2.43 vs. 2.10). In conclusion, feeding high CS diets increased total carcass yield without reducing quality, but increased time on feed and decreased ADG. Feeding SO increased gain/feed ratio, but increased feed costs and reduced ADG for the high CS diets. [ABSTRACT FROM AUTHOR]

Tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine that upregulates suppressors of cytokine signaling (SOCS) mRNA and induces nitric oxide (NO) production. Both SOCS and NO inhibit intracellular growth hormone (GH) signaling and uncouple the somatotropic axis. Liver TNF-α mRNA increases after calving in dairy cows, when GH signaling is disrupted. Plasma TNF-α concentrations in transition dairy cows have not been reported. The objective of this study was to measure plasma TNF-α, GH, and insulin-like growth factor-I (IGF-I) concentrations over the course of transition in dairy cows. Multiparous Holstein cows (n = 18), dried off 45 d before expected calving, were fed diets at either ad libitum (AL) or restricted (R) DMI until calving. The R diet was formulated to meet nutrient requirements at a DMI of 9.4 kg/d, while AL cows consumed 13.7 kg DM/d. Cows were fed the same diet ad libitum for 4 wk after calving. Coccygeal or jugular vein blood samples were collected weekly, with additional samples taken on days -18, -13, -9, -5, -2, +1, +4, and +7 relative to calving. Plasma TNF-α concentrations (pM) were unaffected by diet, but tended to be less (P = 0.11) after calving (5.02 vs. 4.77). Plasma GH concentrations (nM) were increased (P < 0.01) by R and were greater (P < 0.01) after calving for all cows (prepartum: 0.06 vs. 0.05; postpartum: 0.15 vs. 0.11, for R vs. AL). Plasma IGF-I concentrations (nM) were unaffected by diet before calving, but decreased (P < 0.01) after calving for all cows (prepartum: 13.28 vs. 12.87; postpartum: 9.84 vs. 8.21, for R vs. AL, respectively). During wk 1 postpartum, IGF-I concentrations were less (P < 0.01) for AL vs. R (7.49 vs. 10.13). If TNF-α is involved in the uncoupling of GH signaling after calving, its role is not readily explained by peripheral plasma changes. Regulation of TNF-α within the liver itself may be more important to understand its role in GH signaling. [ABSTRACT FROM AUTHOR]

Suppressors of cytokine signaling (SOCS) inhibit intracellular growth hormone (GH) signaling. After calving, the somatotropic axis of the dairy cow is uncoupled, partially due to reduced liver specific GH receptor (GHR 1A) on the liver cell surface. Estradiol-17β (E2) concentrations increase at calving, and E2 upregulates SOCS-2 mRNA. The presence of SOCS in the liver of transition dairy cows has yet to be examined. We hypothesize SOCS-2 mRNA is upregulated after calving. Multiparous Holstein cows (n = 18) were dried off 45 d before expected calving and fed diets at ad libitum (AL) or restricted (R) DMI during the dry period. The R diet was formulated to meet nutrient requirements at a DMI of 9.4 kg/d, while AL cows consumed 13.7 kg DM/d. All cows were fed the same diet ad libitum for 4 wk after calving. Coccygeal or jugular vein blood samples were collected weekly and more frequently near calving. Liver biopsies obtained at -21, -7, +2, and +28 d relative to calving were assessed for SOCS-2 and GHR 1A mRNA by real time RT-qPCR and were normalized to controls. The relative amount of SOCS-2 mRNA increased after calving (P < 0.01) and was greater on +2 d for R vs. AL cows (0.81 vs 0.45, P < 0.05). Plasma E2 was greater in R vs. AL (304 vs. 215 pM, P < 0.05) and increased before calving (P < 0.01). Amount of GHR 1A mRNA did not differ between diets, but tended to decrease on +2 d (P < 0.20). In addition to reduced GHR 1A, increased SOCS-2 mRNA after calving, perhaps due to increased E2, may further uncouple GH signaling in the liver of the transition dairy cow. [ABSTRACT FROM AUTHOR]