Unsupplemented Heifers Research Articles

Feeding strategies for rearing replacement beef heifers in a grazing system under tropical conditions

Our objective was to evaluate the effects of pre- and post-weaning protein supplement on the productive response and nutritional and metabolic status of replacement beef heifers grazed on tropical pasture. Fifty-six Nellore heifers (7.7 ± 0.1 months age) with an average initial body weight (BW) of 237 ± 3.5 kg were distributed in a completely randomized design in 2 × 2 factorial arrangement. The four strategies were: US-ME, unsupplemented heifers at pre-weaning and supplemented with 5 g/kg BW at post-weaning; US-HI, unsupplemented heifers at pre-weaning and supplemented with 7.5 g/kg BW at post-weaning; ME-ME, heifers supplemented with 5 g/kg BW at pre-weaning and post-weaning; and ME-HI, heifers supplemented with 5 g/kg BW at pre-weaning and 7.5 g/kg BW at post-weaning. On average, crude protein (CP) intake and CP: digested organic matter (DOM) ratio were influenced (P < 0.05) by protein supplement in the post-weaning period, with a higher intake of CP and CP:DOM ratio in HI heifers than in ME heifers (average CP of 0.812 vs 0.665 kg/day and average DOM of 204 vs 174 g CP/kg). Nonetheless, the post-weaning protein supplement did not affect the intake of total dry matter (DM), pasture DM, organic matter (OM), neutral detergent fiber corrected for ash and protein residue (apNDF), non-fibrous carbohydrates, and DOM. The CP digestibility was highest (P = 0.005) for HI heifers than for ME heifers (average of 0.732 vs 0.645 g/g DM). The pre-weaning and post-weaning protein supplement did not affect the concentration of insulin-like growth factor–1 (IGF-1), progesterone, albumin, globulins, glucose, and triglycerides, and liver mRNA expression of carbamoyl phosphate synthetase-1 (CPS-1) and phosphoenolpyruvate carboxykinase (PEPCK). Finally, the pre-weaning and post-weaning protein supplement did not affect growth performance, carcass traits, and body growth in the post-weaning. Supplementation during pre-weaning does not bring any carry-over effect on the productive performance and metabolic status of heifers supplemented during post-weaning. However, supplementation in post-weaning with 5 or 7.5 g/kg BW allows a compensatory growth of heifers that are unsupplemented at pre-weaning. Therefore, the supply of 7.5 g/kg BW of protein supplement for beef heifers only during the post-weaning period is recommended.

Growth and reproductive performance responses to post-weaning supplementation of early and normally-weaned Brahman crossbred heifers raised in tropical rangelands.

This study investigated the effect of five post-weaning supplementation strategies and two weaning weight groups on long-term growth, puberty and pregnancy percentage of Brahman crossbred heifers. Early-weaned (118 ± 6 kg liveweight) and normally-weaned (183 ± 6 kg liveweight) heifers were allocated to group pens (n = 4 and n = 5/pen for early- and normally-weaned respectively) and offered one of five levels of post-weaning protein supplementation: 0, 1, 2.5, 5 and 10 g of supplement/kg liveweight.day with ad libitum access to a low quality sabi grass (Urochloa mosambicensis) hay during the first dry season (169 days) after weaning. After the post-weaning supplementation period, all heifers grazed the same pastures as a single mob until the end of the experiment and were exposed to fertile bulls from January to May 2016. During the first dry season, supplement intake had a positive linear effect on liveweight gain and hip width gain with no difference in the response between weaning groups. Overall, heifers with higher supplement intakes (i.e. 5 and 10 g/kg) had higher hip height gain (P < 0.005), hip width gain (P < 0.001), body condition score (P < 0.001), and concentration of insulin-like growth factor-1 (P = 0.001), triiodothyronine (P = 0.04) and insulin (P = 0.05) in plasma compared to unsupplemented heifers. These changes resulted in thicker proliferative and hypertrophic zones (both P = 0.03) of the tuber coxae growth plate, larger diameter of terminal hypertrophic chondrocytes (both P = 0.004) at the end of the post-weaning supplementation period when comparing the highest level of supplementation with unsupplemented group. Unsupplemented heifers from both weaning weight groups demonstrated compensatory liveweight gain over the first wet season while evidence of catch-up growth in skeletal dimensions was observed in the second wet season. The main determining factor for pregnancy status of two-year-old Brahman crossbred heifers was pre-mating liveweight (P < 0.001), the pre-mating liveweight was in turn affected by post-weaning supplementation (P = 0.02) or weaning weight group (P < 0.001). This study further demonstrated the positive relationship between premating weight and the occurrence of pregnancy, with an approximate 300 kg pre-mating liveweight required to achieve approximately 80% (67.1–90.3% for a 95% confidence interval) probability of pregnancy in two-year-old Brahman crossbred heifers mated for 4 months.

Bioefficacy of hydroxy-selenomethionine as a selenium supplement in pregnant dairy heifers and on the selenium status of their calves

This study aimed to determine the effects of supplementing pregnant heifers with the organic selenium (Se) source 2-hydroxy-4-methylselenobutanoic acid (HMSeBA) during the last 8 wk of pregnancy on dam and calf Se status. A total of 42 in-calf heifers were recruited to the study and randomly allocated to 1 of 3 treatments; a negative control (Con), sodium selenite (NaSe), or HMSeBA. Animals were blocked by body weight, body condition score, and expected calving date before treatment allocation. Following enrollment, all animals underwent a 7-wk wash-out period, after which they received their respective supplements, top-dressed daily onto a basal diet for the last 8 wk of pregnancy. Heifer blood samples were taken at weekly intervals from enrollment until 2 wk before expected calving date and as soon as possible after calving for determination of whole-blood glutathione peroxidase activity (GSH-Px) and plasma Se and malondialdehyde (MDA) concentrations. Selenized AA were determined in plasma samples taken at 3 wk precalving. A colostrum sample was taken as close to parturition as possible for determination of colostrum total Se, selenized AA, and IgG concentration. Calves were blood sampled as close to birth as possible for determination of whole-blood GSH-Px activity and plasma Se and MDA concentrations. Differences in whole-blood GSH-Px activity did not become apparent until calving; GSH-Px activity was lowest in Con heifers but similar between NaSe and HMSeBA heifers. Plasma Se was lowest in unsupplemented heifers and greatest in those supplemented with HMSeBA; this was attributable to greater selenomethionine concentrations in the plasma of HMSeBA heifers. Colostrum Se was lowest in Con heifers and greatest in HMSeBA heifers. The greater Se concentration of HMSeBA heifers was attributable to a greater proportion of total Se comprising selenocysteine; the reason for this is not known. There was no effect of supplementation on colostrum IgG concentration. Plasma Se was lowest in calves born to Con heifers and greatest in those born to HMSeBA heifers. There were no effects of treatment on calf whole-blood GSH-Px activity or plasma MDA concentration. The enhanced Se status associated with HMSeBA supplementation is likely a consequence of selenomethionine supply and may confer benefits to both the dam and her calf postpartum.

Mild Dietary Copper Insufficiency Depresses Blood Neutrophil Function in Dairy Cattle

Abstract Effects of dietary copper insufficiency on bovine blood neutrophil function were evaluated. Dairy heifers were maintained on a basal (6-7 mg Cu/kg diet) or copper-supplemented (20 mg Cu/kg diet) diet beginning 84 d prepartum. At approximately 35 d postpartum, heifers were bled for neutrophil isolation 1 d prior to and 2 d following intramammary infusion of endotoxin in 2 mammary quarters. Neutrophils were evaluated for in vitro production of superoxide anion, reduction of nitroblue tetrazolium, and bactericidal activity. Copper status did not affect neutrophil reduction of nitro-blue tetrazolium or production of superoxide anion. Neutrophil bacterial phagocytosis and number of bacteria ingested per neutrophil were similarly unaffected by diet. Prior to endotoxin infusion neutro-phils isolated from copper-supplemented heifers were significantly more effective at killing ingested bacteria than neutrophils from unsupplemented heifers. Endotoxin infusion eliminated diet-related differences in bacteri...

Modulation of Bovine Mononuclear Cell Proliferation and Cytokine Production by Dietary Copper Insufficiency

Abstract Studies were undertaken to determine immunological effects of subclinical copper deficiency in the bovine. Ten primigravid Holstein heifers were maintained on a basal (6-7 ppm Cu; n = 5 heifers) or copper-supplemented (20 ppm; n = 5 heifers) diet beginning 84 d prepartum. Blood mononuclear cells were isolated at approximately 90 d of lactation. Mononuclear cells were evaluated for proliferative capacity and in vitro cytokine production. The dietary protocol utilized induced significant (p < 0.05) decreases in liver copper stores in unsupplemented heifers without major effects on blood indicators of copper status. Mononuclear cell proliferation was not significantly affected by copper status. Mononuclear cells isolated from copper-supplemented heifers produced significantly (P < 0.05) more interferon in vitro than cells from copper-insufficient animals. Supplementation of copper to previously copper-insufficient animals reversed each of these trends and improved in vitro interleukin-2 production. ...

Effects of Starch, Fiber, or Protein Supplementation on Intake and Digestion of Low-Quality Tall Fescue Hay by Growing Dairy Heifers

AbstractHolstein heifers (n = 20; initial BW = 270 ± 46 kg) were used in 3 consecutive randomized, complete-block experiments to measure the effects of ruminally degradable protein (RDP), NDF, and ruminally degradable starch (RDS) supplementation on utilization of tall fescue hay (8.7% CP, 73.1% NDF, 46.5% ADF). Supplementation rates were 0, 0.05, 0.10, 0.15, or 0.20% of BW per day of RDP delivered via soybean meal; 0, 0.16, 0.33, 0.49, or 0.65% BW per day of NDF delivered via soybean hulls; and 0, 0.10, 0.20, 0.30, or 0.40% BW per day of RDS delivered via dry-rolled corn. In trial 1, supplementation with RDP had no effect (P > 0.05) on forage DMI, whereas DM digestibility (DMD) by supplemented heifers was greater (P < 0.01) than by unsupplemented heifers. Digestibility of ADF (ADFD) tended to increase (P = 0.07; quadratic effect) with supplemental RDP. In trial 2, forage DMI tended to decrease linearly (P = 0.08) as supplemental NDF increased; however, DMD and ADFD increased linearly (P < 0.01)withsupplemental NDF.In trial 3, unsupplemented heifers had greater (P = 0.02) forage DMI compared with RDS-supplemented heifers. Moreover, DMD increased linearly (P < 0.01) with supplemental NDF. In trial 3, unsupplemented heifers had greater (P =0.02) forage DMI compared with RDS-supplemented heifers. Moreover, DMD increased linearly (P < 0.01) with supplemental starch and was greater (P < 0.01) among starch-supplemented heifers than controls. The ADFD of unsupplemented heifers tended to be greater (P < 0.07) than that of RDS-supplemented heifers. All supplement types positively influenced DM digestion of fescue hay-based diets fed to heifers, whereas only starch negatively affected dietary ADF digestion.

Sustainable cotton production by using cattle to graze harvest residues in Mexico

Twenty crossbred beef steers and twenty crossbred beef heifers were randomly allotted to two treatments to evaluate the effect of supplementation on animal performance in animals grazing cotton plant residues: (1) 10 steers and 10 heifers were allowed to graze ad libitum in an 8 ha cotton field after harvest, and (2) 10 steers and 10 heifers grazed in a similar field but received 1kg day −1 of supplement. Water intake and mineral consumptionweremeasureddaily.Cottonplantresidueswereobtainedfromanadjacent10hafieldbycollecting 12 representative samples using a 1m 2 frame, and separating leaves and cottonseeds for lab analysis. Dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, lignin, silica, calcium, phosphorus and nitrogen ADF were determined. Supplementation did not affect the total weight gain of the steers or the heifers during the 30-day grazing period. The unsupplemented steers gained 0.500kg day −1 , while the supplemented steers gained 0.466kg day −1 . The supplemented and unsupplemented heifers gained 0.266kg and 0.233kg day −1 , respectively.Water intake did not differ between treatments, but mineral consumption was significantly greater for the unsupplemented calves. The total cotton residues in the soil accounted for about 2,100kg ha −1 of DM. The economic analysis indicated an increased profitability when using steer calves

Performance of beef heifers grazing stockpiled fescue as influenced by supplemental whole cottonseed1

The objectives of this study were to determine the composition of stockpiled fescue from December through February over 2 yr and to determine the performance of heifers grazing stockpiled fescue with or without supplemental whole cottonseed. In early December, 36 heifers (initial BW 277 +/- 0.70 kg, yr 1; 266 +/- 2.2 kg, yr 2; and initial BCS of 5.0 +/- 0.04) were assigned randomly to 6 groups. Each group was assigned randomly to a 2.4-ha tall fescue pasture (98% endophyte infected), which had received 76 kg of N/ha on September 1. Group was the experimental unit for all measures. Forage DM available during grazing (to ground level) averaged 3,913 and 5,370 kg/ha in yr 1 and 2, respectively. The pasture was strip-grazed for 83 d, with daily forage allocation. Three groups were fed whole cottonseed (0.90 kg of DM/heifer; 24.4% CP, DM basis) daily at 0.33% of BW, and a small amount of a corn-based concentrate (0.19 kg of DM/heifer) to assure complete cottonseed consumption. Nutritive value of forage (dry basis) was determined each week by sampling each pasture to the 5-cm target grazing height. Forage disappearance was estimated every 2 wk from pre- and postgraze forage mass. Forage CP was 16.8% in yr 1 and 12.6% in yr 2. In vitro true organic matter digestibility (IVTOMD) was 82.0 and 71.9%, and ADF was 25.9 and 30.7% in yr 1 and 2, respectively. Most indicators of forage quality declined slightly through the winter, although they recovered in late winter in yr 1. The proportion of fescue that was green declined (P < 0.05) from December (79% in yr 1 and 64% in yr 2) to February (62% in yr 1 and 52% in yr 2). Green tissue averaged 20.4 and 15.2% CP, 91 and 87% IVTOMD, and 22.1 and 23.3% ADF in yr 1 and 2, respectively. Brown tissue averaged 10.3 and 8.5% CP, 64 and 62% IVTOMD, and 35.7 and 37.4% ADF in yr 1 and 2, respectively. Shrunk ADG (0.46 vs. 0.56 kg/d in yr 1 and 0.23 vs. 46 kg/d in yr 2) and change in BCS (- 0.03 vs. 0.33 in yr 1 and 0.13 vs. 0.5 in yr 2) was greater (P < 0.05) for supplemented heifers. Supplemented heifers had greater serum urea nitrogen in yr 1 (9.5 vs. 10.5 mg/dL; P < 0.07) and yr 2 (7.2 vs. 8.6 mg/dL; P < 0.01). Forage disappearance was similar between supplemented and unsupplemented heifers (3.19 vs. 3.39 kg.heifer(-1).d(-1) in yr 1 and 4.14 vs. 4.17 kg.heifer(-1).d(-1) in yr 2, respectively). Heifers responded to supplementation, but performance was lower than expected based on forage nutrient content.

Effect of feeding urea-molasses blocks with incorporated fenbendazole on grazing dairy heifers naturally infected with gastrointestinal nematodes.

Between June 1999 and August 2000, the effects of feeding medicated urea-molasses supplement blocks on the growth of dairy heifers in a marginal area of central Kenya were assessed by comparing the live-weight gain of supplemented and unsupplemented heifers grazing the same pasture. Thirty-nine heifers with an average age of 9.6 months were initially treated orally with albendazole (10 mg/kg body weight) and assigned to 3 groups: group I was fed urea-molasses blocks with incorporated fenbendazole (MUMB), group II was fed urea-molasses blocks (UMB) and group III heifers (control) received no block supplementation (NBS). Body weights of the heifers and faecal egg counts (FECs) were measured monthly and larval cultures were made of positive faecal samples of each group. The mean cumulative live-weight responses of the MUMB and UMB groups were significantly greater than the NBS group (P < 0.05). However, at the end of the experimental period, the mean weight gain of the MUMB group did not differ from that of the UMB group (P > 0.05). The FECs were moderate to low in all groups and decreased progressively with increasing age of the animals; FECs for the urea-molasses-supplemented groups remained significantly lower than those of the NBS group throughout the experimental period (P < 0.05). Haemonchus and Trichostrongylus were the predominant nematode genera found in the heifers, but Cooperia, Bunostomum and Oesophagostomum were also present. These results indicate that feeding of urea-molasses blocks substantially reduced production losses attributable to nematode infection of young grazing cattle, and confirms previous observations that well-fed animals are better able to overcome the effects of helminth infections.

Performance of Heifers Grazing Bermudagrass Supplemented with Corn-Fish Meal, Corn-Soybean Meal, or Corn Gluten Feed

A 3-yr study was conducted to determine the effect of supplementation on weight gain and reproduction of 240 fallborn crossbred heifers (80 per year; initial BW 252 ± 2 kg) grazing bermudagrass from July through November. Treatments were: no supplement (NS); 1.37kg ground corn plus 0.45kg of fish meal (CFM); 1.25kg of ground corn plus 0.57kg of soybean meal (CSBM); or 1.82kg corn gluten feed (CGF). There were three replicates of each treatment with two replicates located at one location and one replicate at another location during each year. The stocking rate was 3.7 head per ha. Treatment groups were rotated among pastures within site at 14-d intervals. At the end of the supplementation period, heifers were grouped across treatments within location and placed on ryegrass for a 60-d breeding period. Heifers were managed in these groups until calving. Forage quality decreased through the grazing period as did forage availability. Supplemental hay was offered when available forage was below 1100 kg/ha. Supplemented heifers gained an average of 0.51 ± 0.02kg compared to 0.27 ± 0.02kg for unsupplemented heifers (P<0.001). Heifers supplemented with CFM had higher (P=0.01) ADG (0.57 ± 0.02 kg) than heifers supplemented with either CSBM or CGF (0.48 ± 0.02 kg), and heifers supplemented with CSBM tended (P=0.07) to gain more weight (0.51 ± 0.02 kg) than heifers supplemented with CGF (0.45 ± 0.02 kg). Supplementation did not affect the number of heifers cycling at the beginning of the breeding season (P=0.50) or the number of heifers that were diagnosed pregnant after a 60-d breeding season (P=0.25). Heifers that received supplements prior to the breeding season were 20kg heavier at calving than non-supplemented heifers (P=0.01). These data indicate that although supplementation improved weight gain of the heifers grazing bermudagrass, the level of gain was not high enough to result in a significant increase in the number of heifers reaching puberty at the start of the breeding season or in an increase in the number of heifers pregnant.

Alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of spring-calving dairy heifers

The objectives of this study were to provide baseline data for alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of New Zealand dairy cattle, and to assess the likelihood that abnormal peroxide metabolism has a role in the impaired lactational and reproductive performance noted in selenium-deficient cattle. Twenty-four Friesian heifers were randomly allocated one of four winter diets consisting of hay with or without selenium supplementation, or pasture and silage with or without selenium supplementation. A winter diet consisting exclusively of hay (alpha-tocopherol concentration 19 mg/kg of dry matter) resulted in a pre-calving serum alpha-tocopherol concentration of 1.2 mg/l compared to 4.5 mg/l for pastured heifers (p<0.01). The pre-calving alpha-tocopherol concentration for the heifers fed hay fell into the range considered deficient (<2.0 mg/l), whereas heifers fed pasture and silage remained in the range considered adequate throughout the study period. Serum fatty acid concentration, and the proportion of fatty acids that were polyunsaturated, were lowest in the hay-fed heifers before calving (1.0 mg/ml, 37.1% respectively), and remained unchanged following re-introduction to pasture after calving in late July and August. Serum fatty acid concentration did not increase following the re-introduction of the heifers to pasture because of the unexpectedly low fatty acid concentration (4.8 g/kg of dry matter) of the mature winter pasture. In October, however, the proportion of fatty acids in serum that were polyunsaturated increased (50%) as did serum cy-tocopherol concentrations (greater than 13 mg/l). Mean serum selenium concentrations in the unsupplemented heifers ranged from 139 to 204 nmol/l, being lowest in October (p<0.01). Supplementation with intraruminal selenium pellets (two pellets delivering about 3 mg of selenium/day) increased serum selenium concentration and glutathione peroxidase activity (p<0.01) whereas the type of winter diet had no effect (p>0.05). These results suggest that dairy cattle wintered on hay can become Vitamin E-depleted, whereas the feeding of pasture and silage should provide adequate Vitamin E. The pasture offered following calving during July and August provided a low dietary polyunsaturated fatty acid challenge, suggesting that abnormal peroxide metabolism is unlikely to be an important mechanism in the impaired performance of selenium-deficient adult cattle which calve at this the of year.

Phosphorus Supplementation of Replacement Heifers in the Northern Great Plains

Studies were initiated in 1980 and 1984 to compare animal performance, dietary P levels, and serum mineral levels of P supplemented and unsupplemented replacement beef heifers (Bos taurus). Phosphorus supplementation levels averaged 4 g day-1 from 14 November 1980 and 24 January 1984, respectively, until 1 September 1980 and 15 October 1984, respectively, when supplemental P was raised to 6 g day-1. Heifers in both studies received mixed hay, primarily smooth bromegrass (Bromus inermis Leyss.), and rolled oats during their first winter and hay only the second winter. During the summer they grazed on native pastures which contained primarily western wheatgrass (Pascopyrum smithii (Rydb.) A. Love), needleandthread (Stipa comata Trin. and Rupr.), green needlegrass (S. viridula Trin.), blue grama (Bouteloua gracilis (H.B.K.) Griffiths), and upland sedges (Carex spp.). Hereford and Hereford-Angus cross heifers in the first study showed no weight gain or serum P response to supplemental P, but conception rate over the 2 studies was lower (P<0.05) for the unsupplemented heifers and 75% of the open heifers occurred in the first study. Hereford-Simmental heifers used in the second study demonstrated an immediate weight gain response (P<0.06) to supplemental P which persisted to the end of the study in 1985, but there was only 1 open heifer in the unsupplemented group in this study, compared to 3 in the first study. Serum P was higher (P<0.06) for P supplemented than control heifers only when they were removed from summer pasture in the second study. Diet P (2.10 g kg-1) for unsupplemented Hereford-Simmental heifers during the winter of 1984 was marginal, but diet P (2.53 g kg-1) for unsupplemented Hereford and Hereford-Angus heifers during the winter of 1980-1981 was clearly above recommended levels. Modest weight gain differences in the second study, serum P data and differences in conception rate suggest that Northern Great Plains forages are marginal to deficient in P for replacement beef heifers, but P supplementation would be expected to produce small and variable benefits.

Effect of phosphorus as fertiliser or supplement on the forage intake of heifers grazing stylo-based pastures

The effect of phosphorus (P) fertiliser and P supplement on the forage intake and liveweight gain of yearling Droughtmaster heifers grazing tropical legume based pasture was determined. Forage intake was calculated from estimates of faecal output using slow release, chromic oxide capsules and the predicted in vivo dry matter digestibility of forage selectively grazed by steers fistulated at the oesophagus. Faecal output, forage intake, and liveweight gain increased with increasing rates of fertiliser or with P supplement. Average gross forage intake (kg/day) of supplemented heifers grazing unfertilised pasture during the growing season was nearly 50% more than that of unsupplemented heifers grazing similar pastures, and liveweight gain over the growing season was increased by 65%. Similar, but greater, increases in forage intake and liveweight gain occurred with heifers grazing pasture fertilised annually with 10 kg P/ha as superphosphate. Dietary P concentrations on pasture that had received just 1 application of fertiliser (10 kg P/ha) 5 years before the study were only marginally higher than on unfertilised pasture, but forage intakes were higher and not significantly increased by supplementation. However, the liveweight gain of unsupplemented heifers grazing pasture that was fertilised on 1 occasion was depressed compared with heifers receiving supplement or grazing pasture fertilised more frequently.

Supplemental methionine and time of supplementation effects on ruminal fermentation, digesta kinetics, and in situ dry matter and neutral detergent fiber disappearance in cattle.

Two experiments were conducted to study the effects of methionine supplementation on ruminal fermentation and digesta kinetics. In Exp. 1, nine ruminally cannulated beef heifers (average initial BW = 527 kg) in a crossover design were fed low-quality grass hay and cottonseed meal with or without 11.4 g of supplemental methionine (polysaccharide-coated). Particulate and fluid kinetics, rate of DM and NDF disappearance, ruminal VFA and NH3 N concentrations, and pH were not altered (P > .10) by supplemental methionine; however, ruminal purine concentration was greater (P < .05) in methionine-supplemented heifers than in unsupplemented heifers. In Exp. 2, 12 ruminally cannulated Holstein steers (average initial BW = 622 kg) grazing a fescue pasture were allotted to one of three groups: no supplemental methionine (CON) or 11.4 g of supplemental methionine fed at 0700 (AM) or at 1200 (PM). Forage intake, particulate kinetics, ruminal fluid kinetics, pH, VFA, and NH3 N concentrations were not altered (P > .10) by supplemental methionine or supplementation time. In situ rate of DM and NDF disappearance was greater (P < .05) in supplemented steers than in CON steers; AM steers exhibited faster (P < .05) rates than PM steers. Overall, methionine supplementation of low-quality forage increased ruminal purine concentration but did not alter in situ fermentation or digesta passage, whereas supplementation at 0700, but not at 1200, of steers grazing fescue forage increased rate of NDF fermentation.

Use of Protein Supplements for Dairy Heifers Fed Fresh Grass

One experiment was conducted to determine the influence of protein supplements on the growth of dairy heifers fed fresh grass. Thirty heifers between 100 and 200kg of BW were fed fresh grass cut daily either without supplement or supplemented with molasses or low rumen-degradable protein blocks. Protein contents of the two blocks were similar. Heifers were weighed every 4 wk during the 12-wk experiment. The BW gains of protein-supplemented heifers were higher than those of unsupplemented heifers, but DMI of grass was not different among treatments. Average daily BW gains of heifers fed degradable or undegradable sources of protein were similar. Intake of total N was correlated highly with average daily BW gain, suggesting that intake of N could limit performance of dairy heifers between 100 and 200kg of BW when they are fed fresh grass. The data suggest that light heifers gain more when supplemented with low or high rumen-degradable protein.

Reducing post-partum anoestrous interval in first-calf Bos indicus crossbred beef heifers. 2. Responses to weaning and supplementation

Supplementation designed to increase the supply of glucose and amino acids, was compared with early weaning as strategies for reducing post-partum anoestrous in Bos indicusx Bos taurus (518x318) first-lactation heifers. Twenty-three pregnant heifers were allocated to four treatment groups and fed long-chopped hay (15.8 g N/kg dry matter) ad libitum and a complete mineral mixture throughout the experiment as well as 450 g molasses and 50 g urea per day during the final month of pregnancy. After calving, three groups were supplemented daily for 120 days with either 2 kg cracked rice (E), 0.4 kg formaldehyde-treated casein (P), or cracked rice (2 kg)+formaldehyde-treated casein (0.4 kg) (E+P); the unsupplemented control group had their calves weaned at 60 days post-partum. Supplemented animals had significantly higher intakes of hay (7- 1-7.3 v. 5.9 kg OM/day), weight gain (0.4-0.5 v. 0.0 kg/day) and body condition score (4.6-4.7 v. 4.3) than the unsupplemented heifers, but there were no differences between the supplemented groups in these variables. Unsupplemented animals and heifers fed P partitioned similar amounts of lactose and fat into milk, whereas secretion of both lactose and protein was significantly higher in the E+P and E groups. All control heifers ovulated within 14 days of their calves being weaned, whereas only two of the lactating supplemented heifers (EfP) showed cyclic ovarian activity at that time and three other lactating heifers ovulated several weeks later. The response to weaning occurred in heifers that had a liveweight and condition score of 374 kg and 4.3 respectively, which was 30-50 kg and a half unit in condition below the suckling heifers. In unsupplemented heifers showing ovarian cyclicity, acetate entry rate was less than half that of the supplemented animals, whereas glucose entry rate, adjusted for loss to lactose, was similar for both groups. Supplementation did not affect either the basal concentration or frequency of pulsatile release of luteinizing hormone (LH) at 60 days post-partum, or the LH response to gonadotrophin releasing hormone (5 8g GnRH). It is concluded that under the conditions of the present study, weaning had a greater effect than post-partum nutritional supplements on the resumption of ovarian activity in first-lactation heifers with moderate nutrition.

Effects of urea supplement with or without molasses on the intake, digestibility and liveweight changes of beef heifers fed native hay

Twenty-five Bunaji (White Fulani) beef heifers were used to investigate the effect of supplement of urea with or without molasses on feed intake, digestibility and liveweight changes. The animals were individually penned and fed with native hay (comprising mainly Andropogon and Hyparrhenia species, 94.3% dry matter (DM) 3.1% crude protein (CP)). Feed dry matter intake did not differ significantly ( P < 0.05) among treatments; however heifers supplemented with urea alone and those supplemented with urea-molasses, on the average consumed slightly (10.1 and 10.4%, respectively) more roughage DM than the controls. The apparent digestibility of DM was significantly ( P < 0.05) higher for supplemented animals than for the controls. Heifers offered urea alone gained more weight than the average of those offered urea-molasses supplement (Treatments 3, 4 and 5). Feed efficiency (kilogram gain per kilogram feed) for supplemented animals was better than for unsupplemented heifers.

Detection of cobalt deficiency in lactating heifers and their calves

SummaryResponses in live weight, milk production and calf growth to cobalt supplementation of groups of three and four pregnant heifers were measured to assess the value of serum vitamin B12 concentrations and the urinary concentrations of methylmalonic acid (MMA) and formiminoglutamic acid (FIGLU) for the detection of cobalt deficiency in cattle.The administration of cobalt bullets to pregnant heifers, grazing pastures containing between 0·03 and 0·05 mg/kg cobalt, had no effect on either their live-weight change or milk production, or on the birth weight of their calves. MMA and FIGLU concentrations in the urine of unsupplemented heifers were low for the majority of the experimental period, although the concentrations of vitamin B12 in their serum (&lt; 100 pg/ml) were in the range usually considered indicative of cobalt deficiency.Calves from unsupplemented heifers had lower growth rates during the first 3 months of life and this was associated with intakes of 0·24–0·46 μg/day of vitamin B12 from milk, only 1–3% of those received by calves from supplemented heifers. Poor growth was associated with high urinary FIGLU concentrations, which increased from 500 to 2000 μmol/l between 1 and 3 months of age but decreased to less than 100 μmol/l between 3 and 4·5 months of age. Urinary FIGLU was a more reliable indicator of vitamin B12 deficiency in suckled calves than was urinary MMA, elevated levels of which were observed only at 3 months of age. The concentration of vitamin B12 in the serum of calves from unsupplemented heifers was consistently less than 100 pg/ml, but was not a reliable indicator of their functional vitamin B12 status, as judged by urinary concentrations of FIGLU and/or MMA.

The effect of supplements of formaldehyde-treated casein on the partitioning of nutrients between cow and calf in lactating Bos indicus × Bos taurus heifers fed a roughage diet

The effect of a supplement of formaldehyde-treated casein on partition of nutrients and productivity of Bos indicus x Bos taurus (50% x 50%) first-calf heifers was studied. Sixteen pregnant heifers were fed a long-chopped roughage diet (13 g N/kg organic matter) ad lib. for approximately 3 weeks before calving and for 16 weeks after calving. Half the animals were supplemented with formaldehyde-treated casein (300 g per day). There were also 8 non-pregnant, non-lactating controls, half of which were supplemented with formaldehyde-treated casein. Supplementation had no significant effect on intake, irrespective of the physiological state of the heifers. There was a significant (P &lt; 0.05) positive multiple regression between peak intake during lactation and the weight change of both heifer and calf in the first 8 weeks of lactation. Milk yield was not significantly affected by supplementation for the first 8 weeks. In the second half of lactation supplemented heifers produced significantly (P &lt; 0.05) less milk, but not less milk solids, than unsupplemented heifers. During the latter half of lactation there was a highly significant (P &lt; 0.001) positive relationship between milk yield and lactose secretion. The mean (� s.e.m.) length of the period of anoestrus after calving was 17 � 2.5 and 12 � 1.7 weeks for unsupplemented and supplemented heifers respectively. The length of the period of anoestrus was positively related to milk production (P &lt; 0.01) and peak intake during lactation (P &lt; 0.05). Supplemented lactating heifers had significantly (P &lt; 0.05) higher plasma insulin concentrations and significantly (P &lt; 0.01) lower plasma growth hormone concentrations than unsupplemented lactating heifers. In supplemented heifers in the second 8 weeks of lactation plasma insulin concentration was significantly (P &lt; 0.01) negatively correlated with milk yield and yield of milk constituents. Supplementation with formaldehyde-treated casein did not increase roughage intake but did affect the partition of nutrients via a positive insulin and negative growth hormone response. Nutrients were preferentially diverted into maternal body growth rather than milk synthesis in the second half of lactation.

Nitrogen supplementation of ruminants grazing native pastures in New England, New South Wales

The potential for nitrogen (N) supplementation of ruminants grazing native pastures in late winter was examined in two experiments. In experiment 1 the N contents of the diet selected by unsupplemented sheep and cattle, and by cattle receiving a supplement of linseed meal were determined. Dietary composition was not affected by supplementation but sheep selected a diet averaging 1.7 gN/100 g OM which was significantly greater than the corresponding value of 0.96 gN/100 g OM for cattle. Differences in dietary composition between sheep and cattle were also evident in experiment 2 and were confirmed by analysis of rumen liquor. It was concluded that sheep would not respond to non-protein N supplementation but that cattle might be marginally N deficient. In experiment 2 groups of heifers grazing native pasture were offered supplements of either molassesurea containing 2.54 gN/100 g OM, molasses-urea containing 7.66 gN/100 g OM, linseed meal containing 6.64 gN/100 g OM, or linseed meal treated with formaldehyde. Liveweight changes relative to an unsupplemented group were determined, and individual consumptions of supplement were measured using tritiated water. All heifers lost weight and the rate of loss was significantly greater in unsupplemented heifers than in those receiving supplement. Differences between supplemented groups were not significant after liveweight losses had been adjusted to equal energy intakes using covariance analysis.