Forage-based Diets Research Articles

Growth Performance and Nutrient Utilization in Male and Female Mithun Calves on Green Forage-based Diet

A comparative study of growth rate and feed intake and its utilization in male and female Mithun calves was carried out in hilly tracts of Nagaland. The animals of both sexes were fed fresh jungle grasses ad libitum and 2.0 kg of rice bran fortified with 1% mineral mixture and 1% salt daily. Growth rates of 369.50 and 305.67 g/day were observed in male and female calves, respectively. Sex-related differences in feed and nutrient intakes were statistically significant, whereas no significant difference was found in digestibility coefficients of nutrients between the groups as well as among the animals. Dry matter, digestible crude protein and total digestible nutrient intakes were recorded to be 107.81, 8.08 and 74.73 g/kgW0.75 per day, respectively, irrespective of sex. Feed conversion efficiency (FCE) and nutritive value of the ration were similar in both male and female calves. Results obtained from the study indicate that the growth rate and nutrient intakes were higher in male than female calves but the sex of the animal did not have any significant effect on nutrient utilization.

Prediction of the digestibility of primary growth and regrowth grass silages from chemical composition, pepsin-cellulase solubility and indigestible cell wall content

Prediction of organic matter (OM) digestibility (OMD) of primary growth and regrowth grass silages was studied based on their chemical composition, pepsin-cellulase solubility of OM (OMS) and indigestible neutral detergent fibre (INDF) content. Twenty-five primary and 28 regrowth silages were harvested from mixed timothy ( Phleum pratense) meadow fescue ( Festuca pratensis) or timothy cocksfoot ( Dactylis glomerata) swards by varying the dates of the first and second harvest. In vivo OMD was measured with sheep and indigestible NDF was determined by 12 days ruminal incubation of forage samples in nylon bags using dairy cows fed a forage-based diet. Chemical composition of the silages was significantly correlated with digestibility, but single regression equations led to an unacceptable prediction accuracy of OMD (RMSE>40 g/kg DM). Pepsin-cellulase solubility reliably predicted OMD of primary growth silages (RMSE = 10.8 g/kg DM), but was less accurate for regrowth silages (RMSE = 25.9 g/kg). The prediction accuracy of OMD could be improved by using different equations for the two silage types. Indigestible NDF predicted OMD more accurately than OMS for all silages and especially for the regrowth silages. In contrast to OMS, the relationship between INDF and OMD was similar for both silage types.

Methane-suppressing effect of myristic acid in sheep as affected by dietary calcium and forage proportion

The efficiency of myristic acid (14 : 0) as a feed additive to suppress CH4 emissions of ruminants was evaluated under different dietary conditions. Six sheep were subjected to a 6 x 6 Latin square arrangement. A supplement of non-esterified 14 : 0 (50 g/kg DM) was added to two basal diets differing in their forage:concentrate values (1 : 1.5 and 1 : 0.5), which were adjusted to dietary Ca contents of 4.2 and 9.0 g/kg DM, respectively. Comparisons were made with the unsupplemented basal diets (4.2 g Ca/kg DM). The 14 : 0 supplementation decreased (P<0.001) total tract CH4 release depending on basal diet type (interaction, P<0.001) and dietary Ca level (P<0.05, post hoc test). In the concentrate-based diet, 14 : 0 suppressed CH4 emission by 58 and 47 % with 4.2 and 9.0 g Ca/kg DM, respectively. The 14 : 0 effect was lower (22 %) in the forage-based diet and became insignificant with additional Ca. Myristic acid inhibited (P<0.05) rumen archaea without significantly altering proportions of individual methanogen orders. Ciliate protozoa concentration was decreased (P<0.05, post hoc test) by 14 : 0 only in combination with 9.0 g Ca/kg DM. Rumen fluid NH3 concentration and acetate:propionate were decreased (P<0.05) and water consumption was lower (P<0.01) with 14 : 0. The use of 14 : 0 had no clear effects on total tract organic matter and fibre digestion; this further illustrates that the suppressed methanogenesis resulted from direct effects against methanogens. The present study demonstrated that 14 : 0 is a potent CH4 inhibitor but, to be effective in CH4 mitigation feeding strategies, interactions with other diet ingredients have to be considered.

Saponin rich tropical fruits affect fermentation and methanogenesis in faunated and defaunated rumen fluid

A comparison of the effects on rumen fermentation of three saponin rich tropical fruits supplemented to forage-based diets was completed using a rumen simulation technique (Rusitec). The diets contained either no tropical fruit or 100 mg/g of Sapindus saponaria (crude saponins, 120 mg/g), 200 mg/g of Enterolobium cyclocarpum (crude saponins, 19 mg/g) or 200 mg/g of Pithecellobium saman (crude saponins, 17 mg/g). The four diets were evaluated with faunated and defaunated rumen fluid obtained from a single donor cow. Compared to the control diet, P. saman decreased ( P<0.05) ammonia concentration of rumen fluid, and E. cyclocarpum and P. saman increased ( P<0.05) n-butyrate proportion of total volatile fatty acids. Defaunation enhanced ( P<0.05) propionate proportion with corresponding reductions of acetate and n-butyrate. Organic matter degradation of the S. saponaria diet did not differ from that of the control diet but was higher ( P<0.05) with P. saman and E. cyclocarpum. Only one of the saponin rich fruits evaluated, S. saponaria, decreased ( P<0.05) protozoal count (by 54%) and daily methane release (by 20%) relative to control, but without affecting the methanogen count. Defaunation suppressed methanogenesis by 43% over all diets ( P<0.05), and the effect of S. saponaria on methane was more pronounced in defaunated (29%) versus faunated rumen fluid (14%). When related to organic matter apparently fermented, differences relative to the control diet persisted ( P<0.05), but methane release per unit of fibre degraded did not differ between the S. saponaria diet and the control diet. This study demonstrated that supplementation with S. saponaria is effective against ruminal methanogenesis, but that this was not exclusively an effect of the associated depression in protozoal count.

Feeding of Lablab purpureus forage with molasses blocks or sugar cane stalks to rabbit fryers in subtropical south Texas

In the lesser-developed countries, pelleted commercial feeds for rabbits are generally not available or are cost prohibitive to most farmers. The development of high quality, forage-based diets with simple supplements is a high priority research area. A 35-day feeding experiment was conducted involving 60 rabbit fryers to evaluate lablab forage (fresh or hay) in combination with an energy supplement (molasses blocks or sugar cane). Control animals received a commercial pelleted diet. Four pens replicated each of the five diets, and each pen contained three fryers. Lablab DM was composed of approximately 20% crude protein, 25% neutral and 21% acid detergent fibers, and 12.0% ash. As expected, controls had heavier final body weights by 580 g and more rapid growth by 15.6 g/day than rabbits fed experimental lablab diets ( P<0.01). Rabbits receiving fresh lablab versus lablab hay had similar growth rates ( P>0.05), but rabbits receiving molasses blocks instead of sugar cane had better growth by 3.8 g/day ( P<0.05). Controls consumed more feed in dry matter and had better feed-to-gain conversion than experimental animals ( P<0.01). Rabbits fed fresh lablab versus lablab hay had better carcass yield (56.3 and 52.3%) because of lower non-emptied GIT weights (19.4 vs. 22.7%; P<0.01). Rabbits receiving molasses blocks instead of sugar cane had 3.1% lower carcass yield and 3.2% higher non-emptied GIT weights ( P<0.01). Local research trials should be conducted before subsistence farmers adopt lablab forage-based diets with molasses blocks or sugar cane.

Content of ileal EAAC1 and hepatic GLT-1 high-affinity glutamate transporters is increased in growing vs. nongrowing lambs, paralleling increased tissue D- and L-glutamate, plasma glutamine, and alanine concentrations.

Glutamate is a central metabolite for whole-animal energy and N metabolism. This study tested the hypothesis that ileal epithelium, liver, and kidney content of system X-(AG) glutamate transporters EAAC1 and GLT-1 would be up-regulated to support growth of wethers (30 +/- 1.2 kg) fed a forage-based diet for at least 14 d to gain (2.0 x NEm; n = 9) vs. maintain (1.2 x NEm; n = 9) BW. We have previously demonstrated that two high-affinity glutamate transporters (EAAC1, GLT-1) are expressed by these extensive glutamate metabolizing epithelial tissues. Wethers fed at 2.0 x NEm gained (P < 0.001; 0.26 kg/d) BW, whereas those fed 1.2 x NEm did not. Although plasma concentrations (microM) of glucose and L- or D-glutamate did not differ, plasma glutamine (precursor of glutamate) and alanine concentrations (transamination product of glutamate) were 28% (P < 0.007) and 22% (P < 0.072) greater for growing lambs than nongrowing lambs. In tissues, the concentration of L-glutamate in ileum epithelia and D-glutamate of liver was 49% (P < 0.015) and 181% (P < 0.042) greater, respectively, in growing vs. nongrowing animals, whereas concentrations of glutamate isoforms did not differ in kidney. Paralleling these increased amino acid concentrations, ileal epithelium contained 313% more (P < 0.038) EAAC1 protein and liver contained 240% more (P < 0.001) GLT-1 protein, whereas kidney transporter content did not differ between growing and nongrowing wethers. In contrast to increased EAAC1 and GLT-1 protein content in ileal and liver tissue of growing lambs, messenger RNA levels did not differ. These results indicate that the increased capacity for high-affinity glutamate uptake in growing vs. nongrowing lambs is achieved through increased expression of EAAC1 by ileal epithelium and GLT1 by liver, which parallel increased tissue concentrations of glutamate and plasma concentrations of two major interorgan N carriers, glutamine and alanine.

Forage Feeding to Reduce Preharvest Escherichia coli Populations in Cattle, a Review

Although Escherichia coli are commensal organisms that reside within the host gut, some pathogenic strains of E. coli can cause hemorrhagic colitis in humans. The most notable enterohemorrhagic E. coli (EHEC) strain is O157:H7. Cattle are asymptomatic natural reservoirs of E. coli O157:H7, and it has been reported that as many as 30% of all cattle are carriers of this pathogen, and in some circumstances this can be as high as 80%. Feedlot and high-producing dairy cattle are fed large grain rations in order to increase feed efficiency. When cattle are fed large grain rations, some starch escapes ruminal microbial degradation and passes to the hindgut where it is fermented. EHEC are capable of fermenting sugars released from starch breakdown in the colon, and populations of E. coli have been shown to be higher in grain fed cattle, and this has been correlated with E. coli O157:H7 shedding in barley fed cattle. When cattle were abruptly switched from a high grain (corn) diet to a forage diet, generic E. coli populations declined 1000-fold within 5 d, and the ability of the fecal generic E. coli population to survive an acid shock similar to the human gastric stomach decreased. Other researchers have shown that a switch from grain to hay caused a smaller decrease in E. coli populations, but did not observe the same effect on gastric shock survivability. In a study that used cattle naturally infected with E. coli O157:H7, fewer cattle shed E. coli O157:H7 when switched from a feedlot ration to a forage-based diet compared with cattle continuously fed a feedlot ration. Results indicate that switching cattle from grain to forage could potentially reduce EHEC populations in cattle prior to slaughter; however the economic impact of this needs to be examined.

Supplemental Fat Effects on Cholesterol Profiles of Nulliparous Beef Heifers

Nutritional management that enhances cholesterol levels and body condition of heifers may be critical to improving reproductive efficiency. The objective of this study was to evaluate the effect of fat supplementation using a high fat, soybean oil cube formulation on changes in serum cholesterol secretion and body composition of beef heifers maintained on forage-based diets. Hereford and Angus (n = 29) and commercial crossbred heifers (n = 40) were assigned to two treatment groups, either control (n = 35) or high fat cube (to supply 0.23kg fat/d, n = 34) for 45 d. Measurements taken at initiation of trial (d 0) and conclusion of trial (d 45) included BW, body condition score (BCS), ultrasound back fat (UBF), and serum cholesterol concentration [total cholesterol (TC) and HDL-cholesterol (HDL-C)]. At the end of the study period, UBF (P=0.06), BW (P=0.01), BCS (P=0.002), weight to height ratio (P=0.0004), TC (P<0.0001), HDL-C (P=0.009), and TC minus HDL-C concentration (P=0.0001) were greater in heifers fed the supplemental fat treatment. The control heifers gained 13.71 ± 2.04 kg, and the heifers fed supplemental fat gained 37.98 ± 2.08kg during the 45-d study period. The changes in TC concentrations were 13.89 ± 6.11 and 76.32 ± 6.21mg/dL, and changes in HDL-C concentrations were 5.56 ± 3.56 and 14.33 ± 3.62mg/dL for control heifers and heifers fed supplemental fat, respectively. Supplemental fat increased TC and HDL-C concentrations in beef heifers and, thus, may have implications for reproductive efficiency.

Evaluation of formulated agro-industrial wastes as dry season feed for sheep

The study was conducted to estimate the performance of rams on a dry season ration formulated from agro-industrial by-products and compared with the animals on free range for a period of 10 weeks. Eight rams were fed the test diet while 8 rams were left on free range with supplemented wheat offal. Feed intake, weight gain, chestgirth, back-bone length and height at withers were observed. Serum glucose, cholesterol and total protein were determined before and at the end of the experiment. Significant (P<0.05) positive relationships were observed between feed intake and chestgirth (r=0.97213), feed intake and backbone length (r=0.947) and feed intake and height at withers (r=0.79049) for animals fed experimental diet. Significant increases (p<0.01) were observed in the levels of the serological parameters. The mean values (mg/dl) increased from 12.08 + 0.43 to 20.88 + 0.64 for serum glucose; 7.78 + 0.30 to 152.63 + 0.68 for serum cholesterol and 7.22 + 0.39 to 52.75 + 0.25 for serum total protein for rams on test diet. The mean value (mg/dl) for serum glucose, cholesterol and total protein also increased from 12.30 + 0.80 to 22.75 + 0.75, 7.97 + 0.12 to 154.50 + 1.89 and 6.15 + 0.45 to 53.75 + 0.85, respectively, for rams on free range. The rams on the test diet significantly (P<0.05) grew faster than those on free range (48.6 vs 13.4gld). There were also significant (P<0.05) dietary effects on chestgirth gain (0.71 vs 0.03 cm/d), back-bone length gain (0.045 vs 0.020cm/d) and height at withers gain (0.041 vs 0.029 cm/d) in rams fed experimental diet and those on free range, respectively.The results of the study suggest that when poultry droppings and sawdust ash are contained in forage-based diet for small ruminants, significantly (P<0.05) high growth rate, increases in chestgirth, backbone length and height at withers could be obtained than by the animals on dry season free range although with supplement. Keywords: Performance, rams, dry season feed, agro-industrial, by-products.

Meat quality of Angus, Simmental, Charolais and Limousin steers compared at the same intramuscular fat content

Meat quality and marbling properties of Angus, Simmental, Charolais and Limousin steers (4×16) were compared at an average intramuscular fat content (IMF) of 3.25% in the M. longissimus dorsi. The steers were fattened on a forage-based diet until the desired, ultrasonically estimated IMF content was reached which resulted in considerably different growth and carcass characteristics. The Angus group showed a growth rate similar to Simmental and Charolais while Limousin grew slower, became oldest and provided the heaviest carcasses and best conformation. Angus carcasses showed the lowest weight but the highest fatness score. Marbling was equal for all breeds. Angus and Charolais provided pale meat with low haem iron content. Angus and Limousin beef was more tender on sensory assessment than Simmental beef, corresponding to differences found in shear force (non-significant) and myofibrillar fragmentation index measured at 48 h post mortem. Flavour was similar among breed groups while juiciness was highest for Limousin and lowest for Angus. The juicier beef simultaneously showed the highest drip but the lowest cooking losses. In conclusion, clear differences in meat quality were observed between breeds despite similar IMF contents.

Utilization of copper during lactation and neonatal development in muskoxen

Post-natal availability of copper may affect survival of arctic ruminants such as muskoxen (Ovibos moschatus), because neonates must develop rapidly before their first winter. We hypothesized that supplemental injections of Cu for lactating females would increase Cu in milk and in circulation within their offspring. Milk was low in Cu (&lt;4 μg Cu·g–1dry matter) but was not affected by Cu supplementation through peak lactation. Muskoxen are born with high concentrations of Cu in the liver but low activity of the Cu enzyme ceruloplasmin in serum. Levels of serum ceruloplasmin and Cu increase as neonates mature, reaching adult levels in late summer, but this transition coincides with poor growth and diarrhea. Reserves of Cu established in utero are likely depleted as metabolic processes mature and as young make the transition from a milk-based to a forage-based diet. Therefore, availability of trace minerals in utero and in autumn forages may influence the growth, immune function, and survival of young muskoxen in their first year.

Soybean hulls, wheat middlings, and corn gluten feed as supplements for cattle on forage-based diets.

Soybean hulls, wheat midds, and corn gluten feed are viable alternative supplements for forage-fed cattle. All three result from the processing of major Unites States agricultural crops, so large supplies are available. Their value is better for ruminant animals than for monogastrics because they contain digestible fiber components. These byproducts are widely available throughout the Unites States and will generally be more economical than traditional feed grains or commercial feeds when used appropriately as supplements to forage-based diets. Knowledge about the composition of base forage must be used in planning supplementation strategies because base forages vary in protein and mineral content [9]. Soybean hulls alone may be a good selection in situations in which forages are adequate or high in protein. In situations where forage is marginal or deficient in protein, wheat midds, corn gluten feed, or a mix of soybean hulls and corn gluten feed might be most desirable. All three feeds can be variable in nutrient composition, so they should be analyzed to ensure a balanced nutrient level in diets. Soybean hulls are especially variable in crude protein content and should always be analyzed when forages are marginal or deficient in protein. Despite the fact that published energy levels are substantially lower, research has shown that soybean hulls and wheat midds have a value comparable to corn and soybean meal in forage-based diets. Corn gluten feed has also been comparable to corn and soybean meal in most reports but is closer in value to its published energy levels. In general, results with soybean hulls have been surprisingly good and consistent, whereas responses to wheat midds and corn gluten feed supplementation have been more variable and sometimes disappointing. Feeding rates for soybean hulls can range from low to extremely high depending on forage availability and desired performance. Wheat midds should be limited in most situations to 50% of the expected dry matter intake because of their rapidly digested starch content. Corn gluten feed should be limited to approximately 50% of expected dry matter intake because of its high sulfur content. Several research groups are currently evaluating self-feeding programs for these byproducts, and while the potential for health and production problems exist, results have been encouraging in most cases. Self-feeding would reduce the labor costs of hand feeding and could provide backgrounders with a program to expand cattle numbers on a limited land base.

Effects of Calcium Salts of Long-Chain Fatty Acids on Growth, Reproductive Performance, and Hormonal and Metabolite Concentrations in Pubertal Beef Heifers and Postpartum Cows

Pubertal Angus heifers and postpartum Angus cows were used to study the effects of supplemental calcium salts of long-chain fatty acids (CLCFA) added to forage-based diets on growth, reproductive performance, and hormonal and metabolite concentrations. In Experiment 1, heifers were fed corn (control; n = 20) or corn plus Megalac® (CLCFA; n = 20). Supplements were isoenergetic and fed for 123 d prior to breeding. Blood samples, BW, and hip heights were obtained on d 0, 32, 60, 88, 123, and 260. Growth, serum leptin, early pregnancy progesterone concentrations, and reproductive performance, except for calving rate, were not different. Calving rate for heifers fed ClCFA tended to be greater (P=0.12) than that of heifers fed a control diet. Serum cholesterol increased (P<0.01) over time only in heifers fed ClCFA; however, ClCFA increased (P<0.01) concentrations of serum triglycerides only on d 32 and 123. Experiment 2 was conducted to determine the effects of ClCFA on reproductive performance of postpartum cows receiving chelated (CHEL; n = 36) or inorganic (INORG; n = 38) mineral supplements. Beginning 28 d prior to estrus synchronization, cows within each mineral group were fed the control diet or the diet containing corn plus CLCFA, as in Experiment 1, for 54 d. Blood samples and BW were obtained on d 0, 28, and 56. Weight loss was greater (P<0.01) in cows receiving INORG supplements than in cows receiving CHEL supplements; however, CLCFA reduced (P<0.01) the amount of BW lost in cows receiving INORG supplements but not in cows receiving CHEL supplements. Overall, concentrations of serum cholesterol and triglyceride and reproductive performance, excluding calving interval, were not significantly affected by CLCFA. Calving interval tended to be longer (P=0.06) in cows fed CLCFA.

The effect of sugar-beet pulp on the nutritive value of high-temperature dried alfalfa for ponies

Feeding horses high levels of cereal starch can result in diet-related azoturia, laminitis and colic, whereas high fibre, forage-based diets do not generally elicit these conditions. Therefore, it would be advantageous to develop fibrous feeds with increased digestibilities, permitting horses with high energy demands to be sustained on greater forage: cereal starch ratios. High temperature dried (HT) alfalfa has been fed to horses for a number of years and it is common practise to combine this with sugar beet pulp (SB) another nutritious fibrous feed for horses. Synergistic effects of SB when added to fibre-based diets have been observed in other species in vivo (Longland et al., 1994) whereby the digestibility of graminaceous feeds has been increased. However, such effects have been little examined in horses fed a leguminous-forage diet. The aim of this study therefore, was to determine if SB enhanced the digestibility of alfalfa, a forage legume that is increasingly being fed to equines in the UK.

Characteristics of steers of six beef breeds fattened from eight months of age and slaughtered at a target level of intramuscular fat – II. Meat quality

Abstract. Meat quality of Angus (AN), Simmental (SI), Charolais (CH), Limousin (LI), Blonde d'Aquitaine (BL), and Piedmontese (PI) steers (n = 22 per breed group) was measured in the M. longissimus dorsi (M.l.d.) and the M. biceps femoris, regio glutea (M.b.f.). Animals were fattened in two subsequent series on a forage-based diet until a target level of 3.5 % intramuscular fat (IMF) was reached aecording to real-time ultrasound assessments in the live animals or until 15 months of fattening had passed. Series 1 was performed in a tie-stall barn while a loosehousing system with straw bedding was applied in series 2. The actually measured IMF contents in M.l.d. were 3.35, 3.47, 3.49, 3.48, 2.34 and 2.40 % for AN, SI, CH, LI, BL and PI, respectively. Breed group differences in IMF content were mostly accompanied by a contrary Variation either in muscle water or protein content. Muscle cholesterol levels were similar for all breeds amounting to 47 and 51 mg/100 g on average in M.l.d. and M.b.f, respectively. Early and late postmortem muscle pH was relatively similar among breeds, but water-holding capacity, measured as losses due to drip, ageing, thawing and cooking, was unfavourably high in AN (drip loss excepted) in both muscles. Cooking loss tended to be lowest in PI, drip loss in SI. The AN showed the palest meat. In line with lightness, heme iron contents were clearly lowest in both muscles in the AN steers. There was no relationship found between IMF and shear force among breed groups. No significant differences between breed groups occurred in M.l.d. collagen solubility and shear force. Apart from breed differences, there were several differences noted between fattening series, namely clearly better water-holding capacity and lower shear force of the meat from series 2 (group housing) than from series 1 (tied System). The results indicate that in steers of similar IMF content and raised under the same feeding and management conditions, differences in most M.l.d. and M.b.f. quality traits were apparent, with the exception of shear force and M.l.d. collagen solubility.

The effects of degradable and undegradable intake protein on the performance of lactating first-calf heifers.

Two 60-d experiments were conducted to evaluate the effects of supplementing degradable (DIP) and(or) undegradable (UIP) intake protein on the performance of lactating first-calf heifers. Diets were formulated to meet the requirements for either DIP, metabolizable protein (MP), or both when diets contained low-quality grass hay and an efficiency of microbial protein synthesis estimate of 10%. In Exp. 1, 32 individually fed first-calf heifers (avg 395 kg) were allotted to a 2 x 2 factorial arrangement of treatments (main effects of DIP, MP, and DIP x MP interaction) 1 d after calving. Cows consumed a basal diet of chopped crested wheat grass hay (4.3% CP, 67% DIP) ad libitum. Supplemental DIP and UIP were supplied by varying the ratios of soybean meal (75% DIP) and a heat-treated, protected soybean meal (70% UIP). Cow weight gain was better (P < 0.01) when adequate DIP was supplied than when DIP was deficient. However, calf weight gain was not increased by supplementing the cow with DIP. Supplemental UIP did not (P > 0.40) improve cow or calf weight gain. Blood urea N levels were higher (P < 0.01) for cows receiving supplemental DIP and UIP. However, milk production estimates were similar among treatments, as were digestibilities of OM and ADF. Nitrogen digestibility was greater when supplemental DIP was fed, but providing additional UIP did not (P = 0.15) change N digestibilities. Experiment 2 evaluated similar supplements using the same experimental design to determine changes in cow and calf weight gain, body condition score, and pregnancy rate. Seventy-two first-calf heifers (avg 441 kg) were allotted to supplement treatments 1 d after calving and were fed grass hay (5% CP, 53% DIP, 10% microbial efficiency) for ad libitum consumption for 60 d. Supplements were individually fed three times/week. Varying the ratios of soybean meal, heat-treated soybean meal, and corn gluten meal provided additional DIP and UIP. Unlike in Exp. 1, supplemental UIP improved (P < 0.05) cow weight gain. Calves from dams supplemented with DIP gained 5 kg more weight after 60 d than calves from dams deficient in DIP. Pregnancy rates in the fall were similar (P = 0.90) among treatments. These data suggest that DIP was more limiting in Exp. 1 than was UIP. Supplementing UIP in Exp. 2 improved cow weight gains but did not improve calf gains. Data suggest that the efficiency of microbial protein synthesis for this forage-based diet was probably less than 10%.

Molecular identification of high-affinity glutamate transporters in sheep and cattle forestomach, intestine, liver, kidney, and pancreas.

Glutamate metabolism is essential to support many facets of metabolism. The objective of this study was to determine the tissue distribution of glutamate transporters known to support the tissue metabolism of glutamate. The expression of proteins capable of high-affinity glutamate transport (system X-(AG)) by epithelia isolated from the rumen, omasum, duodenum, jejunum, ileum, cecum, and colon and homogenates of liver, kidney, and pancreatic tissues from wethers (n = 4; BW = 28.4 +/- 8.4 kg) and steers (n = 3; BW = 426 +/- 32.3 kg) fed forage-based diets was evaluated by immunoblot analysis. Proteins EAAC1 (62, 93 kDa) and GLT-1 (142, 188, >202 kDa) were expressed by every tissue examined. In contrast, GLAST1 (140 kDa) was expressed only by the pancreas, and EAAT4 (67 kDa) was detected only in sheep brain. To corroborate protein expression data, the presence and size of transporter mRNA in ileal, liver, and pancreatic homogenates were evaluated by Northern analysis. GLAST1 mRNA (2.4, 4.3 kb) was detected only in the pancreas, whereas EAAC1 (2.2, 2.8 kb) and GLT-1 (12.1 kb) mRNA transcripts were detected in all three tissues. The expression of EAAT4 and GLT-1 mRNA was confirmed by reverse transcriptase-polymerase chain reaction analyses. Sequencing of the resulting partial-length ovine GLT-1 cDNA revealed 100% identity with the rat homolog. Overall, these data demonstrate that sheep and cattle share the same pattern of system X-(AG) transporter expression, which differed among tissues and transporter isoforms. Accordingly, these data provide the fundamental knowledge to initiate research that determines whether the expression of high-affinity glutamate transporters by ruminants is sensitive to ontogenic and(or) dietary regulation.

The effects of bull exposure and lasalocid on the development of replacement beef heifers

At weaning in the fall, crossbred heifers (n = 224), born in either the winter (January–February) or spring (March–April), were assigned on the basis of age, sire-breed and body weight to one of two similar winter housing facilities (with or without sterilized bulls), and to one of two forage-based (87%) diets (with or without lasalocid, 200 mg d−1) within each housing facility. Observations for estrus were made twice daily. Timed AI (66 h after PGF2α) was used to breed heifers for the first time at 14 mo of age. Plasma progesterone concentrations were used to confirm estrus/ovulation and to determine the PGF2α response rate. Bull exposure advanced puberty in winter-born heifers, but delayed puberty in spring-born heifers (P ≤ 0.029). Similarly, timed AI pregnancy for winter-born heifers was higher with than without bull exposure (58.9 vs. 32.5 ± 5.3%; P = 0.017) while the opposite occurred for the spring-born group (27.1 vs. 59.1 ± 4.7%; P &lt; 0.001). Bull-exposed spring-born heifers were the oldest at calving, the latest to calve, and their calves had the slowest growth and lowest weaning weight means (P &lt; 0.027). Lasalocid did not influence puberty (P ≥ 0.273), had a small effect on body weight gain (P ≥ 0.033) that did not limit attainment of optimal body weight or condition at AI, but enhanced response rate for spring-born heifers (P = 0.075) and conception rate for winter-born heifers (P = 0.047). The efficacy of bull exposure and lasalocid is dependent upon the proximity of heifers to the attainment of puberty when the treatments are introduced; further research is required to determine the most appropriate use of either management tool for developing beef replacement heifers. Key words: Puberty, heifer development, bull exposure, ionophore, estrus, conception

The performance of primiparous and multiparous beef cows rearing single and simulated-twin calves

One hundred and eighteen Hereford-cross heifers (n = 70) and cows (n = 48) and their offspring were used to evaluate the impact of simulated twinning on weaned calf production and reproductive performance. Twin-calf rearing was simulated by the adoption of a second calf born within 24 h of the birth of the dam's natural calf. In each of 4 yr, cows calved in winter (January–February), were turned out in spring (late May) to rotationally graze grass-legume pastures until weaning in the fall (late September). From calving until turnout cows were given a forage-based diet consisting of either grass-legume silage or hay offered free choice, plus concentrate, the amount of which was 75 or 100% higher for dams in the simulated-twin (ST) than the single (S) treatment. All calves had access to the conserved forage and were given the concentrate ration as creep feed. Estrus detection was performed twice daily beginning 3 wk before and continuing for 4 wk into the breeding season, which consisted of AI for the first 25 d and bull service for the remaining 22 d. In years 2 and 3, the postpartum anestrous period was determined by serum progesterone concentrations. At weaning, S calves weighed more than natural or adopted calves in the ST treatment because weight gain was greater for S calves from birth to turnout. However calf production efficiency (total kilograms calf weaned per kilogram dam weight) was greater for primiparous and multiparous ST than S groups (primiparous 0.85 vs. 0.43 and multiparous 1.62 vs. 0.49; P &lt; 0.05). The ST treatment had no negative effect (P &gt; 0.05) on reproductive performance. As a research tool, this study suggests there are large potential benefits to beef cows raising two, as opposed to one calf. Simulated twinning poses severe management challenges and is not being proposed as a commercial option. However, advances in reproductive technology that could control twinning (e.g., transfer of an embryo a week following AI or twin-transfer of sexed embryos) mean that in future, twin rearing of beef calves may become a feasible option and this study provides valuable information on the post-natal management of cows rearing two calves. Key words: Simulated-twin, progesterone, post-partum, weaning, cow-calf, calves

Programmed Feeding for Maintaining Gestating Beef Cows in the Southeastern United States11Approved for publication by the director of the Arkansas Agricultural Experiment Station as manuscript no. 00037. This project was conducted with funding from the University of Arkansas Agricultural Experiment Station under Hatch Project No. ARK1735 and was also partially supported by gifts from Farmland Industries, Inc. (Kansas City, MO),

To evaluate programmed feeding of beef cows fed high concentrate diets as an alternative to hay, 160 spring calving cows (average BW = 510 ± 11 kg) were stratified by age, body condition score (BCS), and BW. The cows were randomly distributed into 10 drought-stricken pastures (16 cows per pasture) on September 11, 1998. Cows on eight pastures were fed one of four diets (two pastures per diet) formulated with corn or corn gluten feed (CGF) and 20% cottonseed hulls (CSH) or rice hulls (RH) for 87 d and compared with cows on two pastures that were allowed free-choice hay plus a supplement. Diets were fed in amounts to meet requirements for NEm and had similar metabolizable protein yields (corn and CSH, 1.8, 17; corn and RH, 2.0, 14; CGF and CSH, 1.5, 23; and CGF and RH, 1.7, 21 NEm/kg and CP percentage, respectively). Data were analyzed in a completely random design by ANOVA; pasture was the experimental unit. Programmed feeding decreased (P<0.08) BW compared with hay diets. By d 87, cows fed RH diets weighed less (P<0.05) than did cows fed CSH diets, and cows fed corn diets weighed less (P<0.05) than did cows fed CGF diets. Body condition score did not differ (P>0.20) among treatments over the feeding period. The cows fed hay plus supplement cost approximately $1.03/d, but the cost of the program-fed cows averaged $0.54/d. After cows were returned to forage-based diets, no differences (P>0.25) were detected among treatments in BW, BCS, calving date, or calf performance. Programmed feeding of high concentrate diets to gestating cows during forage shortages is a viable alternative to feeding hay. Also, when grain prices are favorable, feed costs to maintain gestating cows are lower with grain than with hay plus supplement.