Influence of protein supplementation frequency on cows consuming low-quality forage: performance, grazing behavior, and variation in supplement intake

The objectives of this research were to determine the influence of protein supplementation frequency on cow performance, grazing time, distance traveled, maximum distance from water, cow distribution, DMI, DM digestibility, harvest efficiency, percentage of supplementation events frequented, and CV for supplement intake for cows grazing low-quality forage. One hundred twenty pregnant (60 +/- 45 d) Angus x Hereford cows (467 +/- 4 kg BW) were used in a 3 x 3 Latin square design for one 84-d period in each of three consecutive years. Cows were stratified by age, BCS, and BW and assigned randomly to one of three 810-ha pastures. Treatments included an unsupplemented control (CON) and supplementation every day (D; 0.91 kg, DM basis) or once every 6 d (6D; 5.46 kg, DM basis) with cottonseed meal (CSM; 43% CP, DM basis). Four cows from each treatment (each year) were fitted with global positioning system collars to estimate grazing time, distance traveled, maximum distance from water, cow distribution, and percentage of supplementation events frequented. Collared cows were dosed with intraruminal n-alkane controlled-release devices on d 28 for estimation of DMI, DM digestibility, and harvest efficiency. Additionally, Cr2O3 was incorporated into CSM on d 36 at 3% of DM for use as a digesta flow marker to estimate the CV for supplement intake. Cow BW and BCS change were greater (P < or = 0.03) for supplemented treatments compared with CON. No BW or BCS differences (P > or = 0.14) were noted between D and 6D. Grazing time was greater (P = 0.04) for CON compared with supplemented treatments, with no difference (P = 0.26) due to supplementation frequency. Distance traveled, maximum distance from water, cow distribution, DMI, DM digestibility, and harvest efficiency were not affected (P > or = 0.16) by protein supplementation or supplementation frequency. The percentage of supplementation events frequented and the CV for supplement intake were not affected (P > or = 0.58) by supplementation frequency. Results suggest that providing protein daily or once every 6 d to cows grazing low-quality forage increases BW and BCS gain, while decreasing grazing time. Additionally, protein supplementation and supplementation frequency may have little to no effect on cow distribution, DMI, and harvest efficiency in the northern Great Basin.     

Forage intake by lactating beef cows differing in potential for milk production

Two feeding trials (early and late lactation) were conducted to measure ad libitum forage intake by beef cows from three breed groups of similar mature weight, but with different milk production potential. Twenty-four cow-calf units, eight from each milk production level (low, medium and high) were grouped (two/pen) based on similarity of cow weight and previous weigh-suckle-weigh and calf weaning weight data. Each pair of cow-calf units was confined to separate pens and allowed ad libitum access to chopped native Sandhills meadow hay. Dry matter intake, cow and calf BW and calf milk consumption were determined. Daily DMI (kg/hd) and milk consumption showed a positive linear response (P less than .05) among low, medium and high milk-producing cows. When cow DMI was expressed as g/unit mean cow BW during the trial, both a positive linear (P less than .05) and a quadratic response (P less than .01) expressed the relationship among production levels during early and late lactation. Calf forage intake, birth weight and adjusted 181- and 205-d weaning weight had no linear or quadratic relationship (P greater than .10) to milk production levels. However, June 1 calf weight, actual calf weaning weight and calf rate of gain (birth to weaning) had a positive linear (P less than .07) relationship. Best fit regression models with DMI as the dependent variable were developed for each trial based on R2 and CV values of the potential models. The best fit model (R2 = .94, SE = .33) for early lactation included production level as a class variable with cow BW.75 and calf birth weight as independent variables. The best fit model (R2 = .92, SE = .53) for late lactation included actual weaning weight in addition to the variables used during early lactation.     

Effect of crambe meal on performance, reproduction, and thyroid hormone levels in gestating and lactating beef cows

Crambe meal was compared to a combination of sunflower and soybean meal as a protein supplement for mature beef cows in two experiments. In Exp. 1, cows (n = 80, average BW 651+/-14.4 kg) were fed crambe meal at 9.86% of dry matter intake (DMI) during the last trimester of gestation. No differences (P < .05) were detected due to treatment for cow weight, condition score, thyroid hormones, calf birth weight, or calving interval. In Exp. 2, cows (n = 100, average BW 566+/-6.82 kg) were fed crambe meal at 7.44% of DMI during the last trimester of gestation and at 8.33% of DMI during early lactation (53+/-6 d of lactation). Gains were greater during gestation (P = .09) and throughout the supplementation period (P = .06), and days to first estrus were reduced (P < .01) for cows fed crambe meal. During lactation, serum triiodothyronine (T3) concentrations did not decline as much (P = .03) in cows fed crambe meal as in cows fed sunflower-soybean meal-based supplements. No differences (P > .10) were apparent for condition score, birth weight, calf growth rate, weaning weight, thyroid hormones during gestation, or calving interval. These data indicate that crambe meal fed at the levels used in this experiment can be used as a protein supplement for beef cows without negatively affecting cows' performance.     

Influence of sward height, daily timing of concentrate supplementation, and restricted time for grazing on forage utilization by lactating beef cows

To establish the effect of sward height, concentrate feeding time, and restricted time for grazing on forage utilization by grazing cattle, 32 crossbred beef (24 Angus and eight Hereford) cows (632 kg BW) and calves (104 kg BW) were grouped by weight and calving date. They were assigned randomly to two sward height treatments (4 to 8 or 8 to 12 cm), replicated four times. The herbage comprised mainly Kentucky bluegrass, orchardgrass, some forbs, and white clover. The cows were restricted to 12 h/d grazing (0700 to 1900) or unrestricted to 24 h/d grazing and fed a concentrate supplement (4.1 kg DM.cow(-1).d(-1), approximately 0.65% of BW or 33% of total DMI) either at 0700 or 1800. The experiment was repeated over three 15-d periods in May, June/July, and August 2000. The herbage on high sward height pasture was higher (P = 0.06) in NDF and ADF and lower (P < 0.01) in CP than low sward height herbage. For cows restricted to 12 h/d grazing, supplementing at 0700 as opposed 1800 resulted in greater (P = 0.04) forage DMI (8.6 vs. 8.1 kg/d), whereas cows that were unrestricted showed little change (8.2 kg/d at 0700 vs. 8.4 kg/d at 1800). Supplementing at 1800 as opposed to 0700 resulted in greater (P = 0.03) herbage DM digestibility (67.7 vs. 64.5%) for cows on high sward height, whereas cows on low sward height exhibited minimal differences (65.4% at 1800 vs. 66.3% at 0700). Cows restricted to 12 h/d grazing and supplemented at 0700 as opposed to 1800 resulted in greater (P = 0.06) digestible DMI (5.0 vs. 4.7 kg/d), whereas unrestricted cows exhibited the opposite response (4.6 kg/d digestible DMI at 0700 vs. 4.9 kg/d at 1800). Supplementing at 1800 as opposed to 0700 increased the time spent grazing to a greater (P = 0.09) extent for restricted than for unrestricted cows. When forage availability or grazing time was limiting (due to a low forage allowance and restricted access to forage, respectively) supplementing concentrates at 0700 resulted in greater forage utilization and intake rate because of increased forage DMI, DM digestibility, and digestible DMI. However, when forage or grazing time was not limiting, supplementing concentrates at 1800 resulted in greater forage utilization because of increased forage DM digestibility.     

Whole soybean supplementation and cow age class: effects on intake, digestion, performance, and reproduction of beef cows

Two experiments were conducted to determine the effects of whole soybean supplementation on intake, digestion, and performance of beef cows of varying age. Treatments were arranged in a 2 x 3 factorial with 2 supplements and 3 age classes of cows (2-yr-old, 3-yr-old, and mature cows). Supplements (DM basis) included 1) 1.36 kg/d of whole raw soybeans, and 2) 1.56 kg/d of a soybean meal/hulls supplement. Supplements were formulated to provide similar amounts of protein and energy, but a greater fat content with the whole soybeans. Supplements were individually fed on Monday, Tuesday, Thursday, and Saturday mornings. During the treatment period, cows had free choice access to bermudagrass hay [Cynodon dactylon (L.) Pers.; 8.4% CP; 72% NDF; DM basis]. In Exp. 1, 166 spring-calving Angus and Angus x Hereford crossbred beef cows were individually fed supplements for an average of 80 d during mid to late gestation. During the first 50 d of supplementation, cows fed soybean meal/hulls gained more BW (10 kg; P < 0.001) and body condition (0.18 BCS units; P = 0.004) than cows fed whole soybeans. However, BW change (P = 0.87) and BCS change (P = 0.25) during the 296-d experiment were not different between supplements. Although calves from cows fed soybean meal/hulls were 2 kg heavier at birth, there was no difference in calf BW at weaning between supplements. Additionally, first service conception rate (68%; P = 0.24) and pregnancy rate (73%; P = 0.21) were not different between supplements. In Exp. 2, 24 cows from Exp. 1 were used to determine the effect of supplement composition on forage intake and digestion; cows remained on the same supplements, hay, and feeding schedule as Exp. 1. Crude fat digestibility was the only intake or digestibility measurement influenced by supplement composition; fat digestibility was higher for cows fed whole soybeans compared with cows fed the soybean meal/hulls supplement (58.1 vs. 48.8%). Hay intake and DMI averaged 1.63 and 1.92% of BW daily, respectively. Dry matter, NDF, and CP digestibility averaged 54.1, 55.1, and 63.2%, respectively. Compared with supplementation with soybean meal/ hulls, whole soybean supplementation during mid to late gestation resulted in reduced BW weight gain during supplementation, inconsistent effects on reproduction, no effect on calf weaning weight, and no effect on forage intake or digestion.     

Undegraded intake protein supplementation: I. Effects on forage utilization and performance of periparturient beef cows fed low-quality hay

Hereford x Angus cows (n = 36; initial wt = 568+/-59 kg) were used to evaluate effects of undegradable intake protein (UIP) supplementation on forage utilization and performance of beef cows fed low-quality hay. Treatments were control (unsupplemented) or one of three protein supplements. Supplements were fed at 1.3 kg DM/d and included UIP at low, medium, or high levels (53, 223, or 412 g UIP/kg supplement DM, respectively). Supplements were formulated to be isocaloric (1.77 Mcal NEm/kg) and to contain equal amounts of degradable intake protein (DIP; 211 g DIP/kg supplement DM). Intake of forage was measured daily during six 7-d collection periods, which approximated mo 7, 8, and 9 of gestation and mo 1, 2, and 3 of lactation. Prairie hay (5.8% CP) was offered daily for ad libitum consumption. Cows were weighed and condition-scored on d 7 of each period. Supplemented cows had greater (P = .01) total organic matter intake (g/kg BW) compared with control animals during gestation. Forage organic matter intake (g/kg BW) was greater (P< or =.02) for control cows than for supplemented cows during lactation. Digestion of OM and NDF was lower (P<.10) for control than for supplemented cows. Body weight of supplemented cows was greater (P = .01) than that of control cows on four of six weigh dates. Supplemental UIP did not affect (P> .10) cow body weight or condition score. Body condition scores of supplemented cows were higher (P = .02) during mo 9 of gestation and during mo 3 of lactation compared with controls. Reproductive performance was similar (P>.10) among treatment groups, and there were few differences in calf performance. These data were interpreted to suggest that supplemental protein can increase total tract OM and NDF digestion by beef cows and increase body weight. Increasing the level of UIP in the supplement had little effect on forage utilization or animal performance.     

Influence of milk production potential on forage dry matter intake by multiparous and primiparous Brangus females

Brangus cows (n = 29) were used in three experiments to evaluate the effects of parity (multiparous vs. primiparous) and potential genetic merit for milk production (high vs. low) on forage intake during late gestation, early lactation, and late lactation. Cows were selected for milk production based on their sire's EPD for milk production (MEPD). Cows had ad libitum access to (130% of previous 2-d average intake) low-quality hay (5.3% CP and 76% NDF), and cottonseed meal was supplemented to ensure adequate degradable intake protein. All females were adapted to diets for at least 7 d, and individual intake data were collected for 9 d. During the lactation trials, actual milk production was determined using a portable milking machine following a 12-h separation from calves. During late gestation, multiparous cows consumed 24% more (P = 0.01) forage DM (kg/d) than primiparous cows; however, parity class did not influence forage intake when intake was expressed relative to BW. Furthermore, MEPD did not influence forage intake during late gestation. During early lactation, multiparous cows produced 66% more (P < 0.001) milk than primiparous cows, and high MEPD tended (P = 0.10) to produce more milk than low MEPD. Multiparous cows consumed 19% more (P < 0.0001) forage DM than did primiparous cows when expressed on an absolute basis, but not when expressed on a BW basis. High-MEPD cows consumed 8% more (P < 0.05) forage DM than did low-MEPD cows. During late lactation, multiparous cows produced 84% more milk than primiparous cows, although MEPD did not influence (P = 0.40) milk yield. In addition, multiparous cows consumed 17% more (P < 0.01) forage DM per day than primiparous cows, but when intake was expressed relative to BW, neither parity nor MEPD influenced forage DMI during late lactation. Milk yield and BW explained significant proportions of the variation in forage DMI during early and late lactation. Each kilogram increase in milk yield was associated with a 0.33- and 0.37-kg increase in forage DMI for early and late lactation, respectively. Results suggest that multiand primiparous cows consume similar amounts of low-quality forage DM, expressed per unit of BW, during late gestation and lactation. Selecting beef cows for increased genetic merit for milk production increases forage DMI during early lactation.     

Influence of pasture sward height and concentrate supplementation on intake, digestibility, and grazing time of lactating beef cows

To establish the effect of sward height (SH) and concentrate supplementation on performance of grazing cattle, 24 crossbred Angus beef cows (535 kg BW) and calves (114 kg BW) were grouped by weight and calving date. They were randomly assigned to two SH treatments, either 4 to 8 cm or 8 to 11 cm, and fed three levels of supplement, high, low, or none, consisting of 6.24, 3.12, and 0 kg x animal(-1) x d(-1), respectively. The experiment was repeated over three 15-d periods in 1996: May (P1), June/July (P2), and August (P3). No SH x supplement level x period or SH x supplement level interactions (P > 0.10) were evident for responses tested. Cows on lower SH had greater (P < 0.08) DMI but spent an additional 1.3 h/d (P < 0.01) grazing compared with cows on higher SH. Sward height had no influence (P > 0.10) on forage DM digestibility (DMD). Forage DMI, DMD, and grazing time (GT) decreased (P < 0.05) as supplementation increased. Nonetheless, supplemented cows consumed more total DMI (P < 0.08) than unsupplemented cows. Cows consumed 2.4 kg/d more forage DM (P < 0.01) in P1 and P2 than in P3. Cows grazed 1.3 h/d (P < 0.01) less in P1 than in P2 and P3. Grazing efficiency (DMI/h GT) declined as supplementation increased and grazing season advanced to P3 (P < 0.01). Decreased forage DMI and grazing efficiency with increasing supplementation suggests that supplemented cattle should be able to maintain productivity while grazing at SH lower than unsupplemented cattle.     

不同精粗比日粮对围产期奶牛健康状况的影响

本试验研究了不同精粗比日粮对奶牛血液pH、尿液pH、采食量及产后瘫痪、胎衣不下、产褥热等健康指标的影响。选择10头预产期相同,体重、体况相近的中国荷斯坦奶牛,随机分为2组,试验1组(CS组)饲喂以玉米秸秆为粗饲料来源的日粮,日粮精粗比接近6:4;试验2组(MF组)饲喂以羊草、苜蓿和玉米青贮为粗饲料来源的日粮,日粮精粗比接近4:6。试验结果显示,CS处理组奶牛产前、产后干物质采食量均极显著高于MF组(P<0.01),且CS处理组奶牛产后干物质采食量增长较快、幅度较大。另外,试验结果还发现,MF处理组尿液pH显著高于CS处理组(P<0.05),两处理组奶牛产前、产后血液pH没有差异(P>0.05)。此外,MF处理组产后疾病的发生率显著高于CS组。试验结果表明,围产期奶牛饲喂精料水平较高的日粮对奶牛产后的健康状况更加有利。     

Effects of supplementation on intake, digestion, and performance of beef cattle consuming fertilized, stockpiled bermudagrass forage

Experiments were conducted to determine the effects of increasing supplement protein concentration on performance and forage intake of beef cows and forage utilization of steers consuming stockpiled bermudagrass forage. Bermudagrass pastures were fertilized with 56 kg of N/ha in late August. Grazing was initiated during early November and continued through the end of January each year. Treatments for the cow performance trials were: no supplement or daily equivalents of 0.2, 0.4, and 0.6 g of supplemental protein per kilogram of BW. Supplements were formulated to be isocaloric, fed at the equivalent of 0.91 kg/d, and prorated for 4 d/wk feeding. Varying the concentration of soybean hulls and soybean meal in the supplements created incremental increases in protein. During yr 1, supplemented cows lost less weight and condition compared to unsupplemented animals (P < 0.05). During yr 2, supplemented cows gained more weight (P = 0.06) and lost less condition (P < 0.05) compared to unsupplemented cows. Increasing supplement protein concentration had no affect on cumulative cow weight change or cumulative body condition score change. Forage intake tended to increase (P = 0.13, yr 1 and P = 0.07, yr 2) in supplemented cows. Supplement protein concentration did not alter forage intake. In a digestion trial, four crossbred steers were used in a Latin square design to determine the effects of supplement protein concentration on intake and digestibility of hay harvested from stockpiled bermudagrass pasture. Treatments were no supplement; or 0.23, 0.46, and 0.69 g of supplemental protein per kilogram of BW. Forage intake increased (P < 0.05) 16% and OM intake increased (P < 0.01) 30% in supplemented compared to unsupplemented steers. Diet OM digestibility increased (P = 0.08) 14.5% and total digestible OM intake increased (P < 0.05) 49% in supplemented compared to unsupplemented steers. Supplement protein concentration did not alter forage intake, total digestible OM intake, or apparent digestibility of OM or NDF. During the initial 30 d after first killing frost, beef cows did not respond to supplementation. However, later in the winter, supplementation improved utilization of stockpiled bermudagrass forage.     

Effects of prepartum supplementation of linoleic and mid-oleic sunflower seed on cow performance, cow reproduction, and calf performance from birth through slaughter, and effects on intake and digestion in steers

Two experiments were conducted to determine the effects of sunflower seed supplements with varying fatty acid profiles on performance, reproduction, intake, and digestion in beef cattle. In Exp. 1, 127 multiparous spring-calving beef cows with free-choice access to bermudagrass hay were individually fed 1 of 3 supplements for an average of 83 d during mid to late gestation. Supplements (DM basis) included 1) 1.23 kg/d of a soybean hull-based supplement (control treatment); 2) 0.68 kg/d of linoleic sunflower seed plus 0.23 kg/d of the control supplement (linoleic treatment); and 3) 0.64 kg/d of mid-oleic sunflower seed plus 0.23 kg/d of the control supplement (oleic treatment). During the first 62 d of supplementation, the BW change was 11, 3, and -3 kg for cows fed the control, linoleic, and oleic supplements, respectively (P < 0.001). No difference in BW change was observed during the subsequent period (-65 kg, P = 0.83) or during the entire 303-d experiment (-31 kg, P = 0.49). During the first 62 d of supplementation, cows fed sunflower supplements tended (P = 0.08) to lose more body condition than cows fed the control diet, but BCS was not different (P > 0.22) for any subsequent measurement. At the beginning of the breeding season, the percentage of cows exhibiting luteal activity was greater for cows fed the control diet (43%; P = 0.02) than for cows fed either linoleic (20%) or oleic (16%) supplementation; however, first-service conception rate (67%; P = 0.22) and pregnancy rate at weaning (92%; P = 0.18) were not different among supplements. No differences were detected in calf birth (P = 0.46) or weaning BW (P = 0.74). In Exp. 2, 8 ruminally cannulated steers were used to determine the effects of sunflower seed supplementation on forage intake and digestion. Treatments (DM basis) included 1) no supplement; 2) a soybean hull-based supplement fed at 0.29% of BW/d; 3) whole linoleic sunflower seed fed at 0.16% of BW/d; and 4) whole high-oleic sunflower seed fed at 0.16% of BW/d. Hay intake was not influenced (P = 0.25) by supplement (1.51% of BW/d); however, DMI was greatest (P < 0.01) for steers fed the soybean hull-based supplement (1.93% of BW/d). Sunflower seed supplementation reduced (P < 0.01) NDF and ADF digestibility while increasing (P < 0.01) apparent CP and apparent lipid digestibility. In conclusion, whole sunflower seed supplementation resulted in reduced cow BW gain during mid to late gestation, but this reduction did not influence subsequent cow BW change, pregnancy rate, or calf performance.     

Impact of different wheat milling by-products in supplements on the forage use and performance of beef cattle consuming low-quality, tallgrass-prairie forage

Two experiments were conducted to evaluate the impacts on forage use and beef cattle performance of incorporating divergent wheat milling by-products in a 30% CP supplement. The by-products were wheat bran (high fiber) and second clears (high starch). The by-products were added as 1) 100% wheat bran; 2) 67% wheat bran, 33% second clears; or 3) 33% wheat bran, 67% second clears to constitute approximately 47 to 49% of the supplement. In Exp. 1, 90 Hereford x Angus cows (BW = 554 kg) grazing winter, tallgrass-prairie range were fed the supplement treatments (2.27 kg/cow daily) from early December 1997 until calving (average calving date = 3/11/98). Cumulative BW and condition changes from trial initiation through calving were not significantly different among treatments. Similarly, significant treatment effects on cow pregnancy rates as well as calf birth weights, ADG, and ending weights were not evident. In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 484 kg) were blocked by weight and assigned to one of the same three supplement treatments or to a negative control (forage only). Steers had ad libitum access to tallgrass-prairie hay (76.4% NDF, 3.1% CP) and were fed supplement at the same rate (relative to BW) as the cows in Exp. 1. Forage OM, NDF, and digestible OM intakes were lower (P < 0.01) for the negative control than for supplemented steers but were not significantly different among the supplemented steers. Digestion of OM was lower (P = 0.03) for the negative control than for supplemented steers, although significant treatment differences were not evident among the supplemented groups. Digestion of NDF was not affected (P = 0.49) by treatment. Within the context of the amount of supplemental protein offered, changes in the combination of wheat milling by-products in the supplement did not affect cow performance or intake and digestion of low-quality forage.     

分级指数与相对值在奶牛用粗饲料品质评定上的比较研究

本文在测定江西奶牛养殖常用的6种粗饲料（串叶松香草、桂牧1号杂交象草、矮象草、黑麦草、墨西哥玉米与鸭茅）的常规成分基础上,实测了奶牛对这6种粗饲料的干物质随意采食量（DMI）,并采用相关模型计算出这6种粗饲料的分级指数（GI）与相对值（RFV）。分别应用单项指标粗蛋白（CP）、中性洗涤纤维（NDF）、干物质随意采食量（DMI）以及综合指标RFV、GI对试验用6种粗饲料品质的分级进行了比较。研究表明：单一指标都难以正确地评定粗饲料品质,必须使用综合的整体指标。GI是首个将粗饲料的可利用能、CP、NDF与家畜的DMI综合起来考虑的一个粗饲料综合评定指数,对粗饲料的分级比RFV更精确。     

Dried poultry waste for cows grazing low-quality winter forage

Two trials conducted in 1996-97 measured BW and body condition score changes of cows fed different sources of degradable intake protein, including dried poultry waste and soybean meal, while grazing low-quality winter forages. In Trial 1, 60 spring-calving cows (5 yr; 555 kg) were used in an individual supplementation trial. Cows were gathered three times a week, sorted into individual pens, and fed their respective supplement. Cows grazed dormant native Sandhills winter range (common pasture) and were assigned to one of six supplemental treatments: 1) no supplement, 2) urea, 3) 22% dried poultry waste + urea, 4) soybean meal, 5) 22% dried poultry waste + soybean meal, or 6) 44% dried poultry waste. All supplements were based on wheat middlings and soybean hulls and were formulated to contain 44% CP. Thirty-six cows were selected randomly (six per treatment) for a 5-d measurement of forage intake from December 16 through December 20, 1996. Cows receiving supplements gained more weight (P < 0.001) and maintained greater body condition (P < 0.001) than unsupplemented cows. Cows receiving urea gained less (P < 0.10) than cows receiving a source of natural protein, but body condition remained similar. No differences were found in daily forage or total organic matter intake (P > 0.10). In Trial 2, cows grazed corn residues. Forty-eight spring-calving cows were group-fed supplements in one of six 4-ha paddocks. Cows received supplements containing either soybean meal or dried poultry waste that were the same as the soybean meal and 44% dried poultry waste supplements fed in Trial 1; gains were not different (P > 0.10). Under the economic conditions that existed at the time of these experiments, the supplement containing dried poultry waste resulted in a savings of $.04 per cow per day and a total savings of $3.20 per cow over an 80-d period. Feeding a supplement containing dried poultry waste resulted in performance similar to that when feeding a more conventional supplement containing soybean meal.     

Effect of increasing proportion of supplemental N from urea in prepartum supplements on range beef cow performance and on forage intake and digestibility by steers fed low-quality forage

Four experiments were conducted to evaluate the influence of changing the proportion of supplemental degradable intake protein (DIP) from urea on forage intake, digestion, and performance by beef cattle consuming either low-quality, tallgrass prairie forage (Exp. 1, 2, and 4) or forage sorghum hay (Exp. 3). Experiments 1, 2, and 3 were intended to have four levels of supplemental DIP from urea: 0, 20, 40, and 60%. However, refusal to consume the 60% supplement by cows grazing tallgrass prairie resulted in elimination of this treatment from Exp. 1 and 2. Levels of supplemental DIP from urea in Exp. 4 were 0, 15, 30, and 45%. Supplements contained approximately 30% CP, provided sufficient DIP to maximize digestible OM intake (DOMI) of low-quality forage diets, and were fed to cows during the prepartum period. In Exp. 1, 12 Angus x Hereford steers (average initial BW = 379) were assigned to the 0, 20, and 40% treatments. Forage OM intake, DOMI, OM, and NDF digestion were not affected by urea level. In Exp. 2, 90 pregnant, Angus x Hereford cows (average initial BW = 504 kg and body condition [BC] = 5.0) were assigned to the 0, 20, and 40% treatments. Treatment had little effect on cow BW and BC changes and calf birth weight, ADG, or weaning weight. However, pregnancy rate tended to be lowest (P = 0.13) for the greatest level of urea. In Exp. 3, 120 pregnant, crossbred beef cows (average initial BW = 498 kg and BC = 4.6) were assigned to the 0, 20, 40, and 60% treatments. Prepartum BC change tended (P = 0.08) to be quadratic (least increase for 60% treatment), although BW change was not statistically significant. Treatment effect on calf birth weight was inconsistent (cubic; P = 0.03), but calf ADG and weaning weight were not affected by treatment. Pregnancy rate was not affected by prepartum treatment. In Exp. 4, 132 pregnant, Angus x Hereford cows (average initial BW = 533 and BC = 5.3) were assigned to the 0, 15, 30, and 45% treatments. Prepartum BC loss was greatest (quadratic; P = 0.04) for the high-urea (45%) treatment, although BW loss during this period declined linearly (P < 0.01). Prepartum treatment did not affect pregnancy rate, calf birth weight, or ADG. In conclusion, when sufficient DIP was offered to prepartum cows to maximize low-quality forage DOMI, urea could replace between 20 and 40% of the DIP in a high-protein (30%) supplement without significantly altering supplement palatability or cow and calf performance.     

Supplementation of dormant tallgrass-prairie forage: II. Performance and forage utilization characteristics in grazing beef cattle receiving supplements of different protein concentrations

Two experiments were conducted to evaluate the influence of supplemental protein concentration on the intake and utilization of dormant range forage by beef cattle. In Exp. 1,97 pregnant Hereford x Angus cows (avg wt = 454 kg) were assigned randomly to three isocaloric treatment supplements: 1) low protein (LP), 13% CP; 2) moderate protein (MP), 25% CP; and 3) high protein (HP), 39% CP. In Exp. 2, 15 ruminally and 12 esophageally cannulated steers (avg wt = 319 and 355 kg, respectively) were assigned randomly to LP, MP and HP treatments and were used in a 22-d winter grazing trial to evaluate forage intake and utilization characteristics. In Exp. 1, cow body condition (BC) and BW changes responded in linear (P less than .01) and quadratic (P less than .01) fashions to increasing protein concentration, with MP and HP displaying the least BC and BW loss from trial initiation (d 1) through d 84. From d 84 to calving (avg calving date = d 120), only the HP supplement continued to be effective in minimizing BC loss (P less than .01). Calf birth weight tended (P = .17) to increase in a linear fashion to increasing supplemental protein concentration, but calf ADG and cow reproductive efficiency were unaffected (P greater than .10). In Exp. 2, forage OM intake responded in a quadratic fashion (P less than .10), with the MP treatment having the highest NDF digestibility and ruminal OM fill. In conclusion, beef cow BC and BW losses during the winter grazing period were minimized with increasing supplemental CP concentration. Intake and utilization of dormant forage by steers were improved with moderate (26%) levels of CP in the supplement.     

Effects of supplementation with high linoleic or oleic cracked safflower seeds on postpartum reproduction and calf performance of primiparous beef heifers

Primiparous Angus x Gelbvieh (n = 36) rotationally crossed beef cows (initial BW = 487.9 +/- 10.5 kg, body condition score = 5.5 +/- 0.02) were utilized to determine effects of supplemental safflower seeds high in linoleic (76% 18:2) or oleic (72% 18:1) acid on cow BW change, body condition score, milk production and composition, calf weight gain, cow serum metabolites, and metabolic hormones. On d 3 postpartum, cows were randomly assigned to one of three isonitrogenous dietary supplements with equal total quantity of TDN: corn-soybean control supplement (n = 12); high-linoleate safflower seeds (n = 12); or high-oleate safflower seeds (n = 12). Safflower-seed supplements were formulated to provide 5% DMI as fat. Supplements were individually fed from d 3 postpartum through 90 d postpartum. Cows had ad libitum access to native grass hay (7.8% CP), trace-mineralized salt, and water. Date of parturition was evenly distributed across treatments with all cows calving within 14 +/- 0.8 d. There were no differences (P = 0.65) in total OM intake among treatments. Although cow BW change did not differ (P = 0.33) by treatment, supplementation influenced cow body condition score (P = 0.02) with linoleate-supple-mented cows in higher (P = 0.005) condition overall than oleate-supplemented cows (5.1 +/- 0.06 vs 4.9 +/- 0.06). Twenty-four-hour milk production did not differ (P = 0.68) among treatments. Percentage milk fat was not different at d 30; however, at d 60 and d 90 percentage milk fat was greater (P ( 0.05) in control and oleate-supplemented cows than in linoleate-supplemented cows. Calf BW gains (P = 0.27) and adjusted 205-d weights (P = 0.48) were not affected by supplement treatment. Supplementation did not influence serum concentrations of glucose (P = 0.38), NEFA (P = 0.61), GH (P = 0.29), IGF-I (P = 0.81), insulin (P = 0.26), or IGF-I binding proteins (P > or = 0.11). Days to conception did not differ (P = 0.40) among treatments. Although overall productivity of the primiparous cows and their calves was not altered by safflower-seed supplementation, differential effects were noted between supplements. Oleate supplementation increased percentage milk fat at d 60, and cow body condition score was lower than in linoleate-supplemented cows. Linoleate-supplemented cows had greater body condition scores by 90 d postpartum than either corn-soybean- or oleatesupplemented cows.     

Effects of stocking rate and corn gluten feed supplementation on performance of young beef cows grazing winter-stockpiled tall fescue-red clover pasture

A winter grazing experiment was conducted to evaluate the effects of stocking rate and corn gluten feed supplementation on forage mass and composition and the BW and BCS of bred 2-yr-old cows grazing stockpiled forage during winter. Two 12.2-ha blocks containing Fawn, endophyte-free, tall fescue and red clover were each divided into 4 pastures of 2.53 or 3.54 ha. Hay was harvested from the pastures in June and August of 2003 and 2004, and N was applied at 50.5 kg/ha at the initiation of stockpiling in August. On October 22, 2003, and October 20, 2004, twenty-four 30-mo-old Angus-Simmental and Angus cows were allotted by BW and BCS to strip-graze for 147 d at 0.84 or 1.19 cow/ha. Eight similar cows were allotted to 2 dry lots and fed tall fescue-red clover hay ad libitum. Corn gluten feed was fed to cows in 2 pastures to maintain a mean BCS of 5 (9-point scale) at each stocking rate and in the dry lots (high supplementation level) or when weather prevented grazing (low supplementation level) in the remaining 2 pastures at each stocking rate. Mean concentrations of CP in yr 1 and 2 and IVDMD in yr 2 were greater (P < 0.10) in hay than stockpiled forage over the winter. At the end of grazing, cows fed hay in dry lots had greater (P < 0.05) BCS in yr 1 and greater (P < 0.10) BW in yr 2 than grazing cows. Grazing cows in the high supplementation treatment had greater (P < 0.10) BW than cows grazing at the low supplementation level in yr 1. Cows in the dry lots were fed 2,565 and 2,158 kg of hay DM/cow. Amounts of corn gluten feed supplemented to cows in yr 1 and 2 were 46 and 60 kg/ cow and did not differ (P = 0.33, yr 1; P = 0.50, yr 2) between cows fed hay or grazing stockpiled forage in either year. Estimated production costs were greater for cows in the dry lots because of hay feeding.     

Effect of the type of silage on milk yield,intake and rumen metabolism of dairy cows grazing swards with low herbage mass

The aim of this study was to evaluate the effect of herbage allowance (HA) and type of silage supplemented (TS) on milk yield, dry matter intake (DMI) and metabolism of dairy cows in early lactation. Thirty‐six Holstein‐Friesian dairy cows were allocated to four treatments derived from an arrangement of two HA (LHA = 17 or HHA = 25 kg of DM/cow/day) and two TS (grass (GS) or maize (MS)). Herbage allowance had no effect on DMI or milk yield. Rumen pH and NH₃‐N concentration were not affected by HA. The efficiency of microbial protein synthesis in the rumen (microbial protein (MP)) was affected by HA with 21.5 and 23.9 g microbial nitrogen per kg ruminal digestible organic matter for LHA and HHA, respectively (P < 0.05). Supplementation with MS showed higher values of milk yield by 2.4 kg/cow/day (P < 0.001), milk protein content by 0.10 % (P < 0.023) and herbage DMI by 2.2 kg/cow/day, and showed lower values for milk urea compared to GS (P < 0.001). The former results suggest that TS had a greater effect on milk yield, total feed intake and energy intake than increase in herbage allowance; however, increase in HA had greater effects on MP than TS.     

The effect of residual feed intake classification on forage intake by grazing beef cows

Although feed intake and efficiency differences in growing cattle of low and high residual feed intake (RFI) classification have been established, little is known about the difference in grazed forage intake between beef cows of known RFI classification. Two experiments were conducted using Hereford cows for which RFI had been determined as heifers using the GrowSafe 4000E feed intake system, after which heifers had been divided into thirds as low RFI, mid RFI, and high RFI. During Exp. 1, 2 replicates of low and high RFI cows (n = 7/replicate) in mid- to late-gestation were blocked to 1 of 4 non-endophyte-infected tall fescue paddocks (1.8 to 2.4 ha), which they grazed continuously for 84 d during summer. Using grazing exclosures, weekly rising plate meter readings, and forage harvests every 21 d, average forage DMI was calculated. Low and high RFI groups did not differ (P > 0.05) in BW change or BCS change over the trial (19.5 vs. 22.1 kg of BW gain and 0.11 vs. 0.10 BCS gain), but low RFI cows had a 21% numerically lower DMI than high RFI cows (12.4 vs. 15.6 kg/d; P = 0.23). The average area needed per paddock over the trial was similar for low and high RFI cows (1.71 vs. 1.82 ha; P = 0.35), and the average DM on offer over the trial was less for low RFI than for high RFI cows (4,215 vs. 4,376 kg; P = 0.06). During Exp. 2, 3 replicates of low and high RFI cows with their calves (n = 4 pair/replicate) strip-grazed stockpiled and early spring growth tall fescue paddocks (0.7 to 0.9 ha) for 60 d in late winter and early spring. Because of limiting forage availability and quality at trial initiation, cow-calf pairs were also fed 3.31 kg/pair of pelleted soyhulls daily. Pre- and post-grazed forage samples were harvested for 4 grazing periods, and forage growth was estimated using a growing degree days calculation and on-site weather station data. Performance did not differ (P > 0.05) between low and high RFI cows throughout the experiment (18.4 vs. 26.6 kg of BW gain and -0.04 vs. 0.15 BCS gain). Despite the utilization of forage offered being similar for low and high RFI cow-calf pairs (P > 0.05), low RFI cows and their calves had an 11% numerically lower DMI than high RFI pairs (12.5 vs. 14.1 kg/d; P = 0.12). We concluded that either no intake differences existed between low and high RFI cows or that current methodology and small animal numbers limited our ability to detect differences.