Behavioral, nutritional, and toxicological responses of cattle to ensiled leafy spurge.

Yearling cattle (n = 25; 416.1 +/- 25.9 kg) were stratified by weight and gender across five groups. Group 1 (OAT) was offered oat/rape haylage (ORH) for ad libitum consumption during two daily feeding periods. Group 2 (SPURGE) was offered leafy spurge/grass haylage (LSGH) for ad libitum consumption during the same feeding periods. Group 3 was offered ORH in an amount equal to the average amount of LSGH consumed by SPURGE at the previous feeding. Group 4 (MIX) was offered LSGH mixed with ORH for ad libitum consumption during the two feeding periods. Group 5 (PAIR) received the equivalent amount of ORH consumed by MIX at the previous feeding. The DMI for OAT, SPURGE, and MIX were similar at the first feeding (P = .52). The SPURGE group consumed very little LSGH thereafter and was removed from the trial. The OAT and MIX groups consumed similar amounts of DM daily on d 1 to 4 when the ration offered to MIX was only 7% LSGH (P = .33). When LSGH made up > or = 21% of the mixture (d 7 to 32), the OAT group consumed more daily DM than did MIX (P < .05). The spurge/oatlage ration offered to MIX was less digestible than the oatlage-only ration offered to PAIR (P < or = .01). Even though blood chemistry did not indicate that LSGH consumption caused organ damage, its intake caused minor alterations (P < or = .05) in serum albumin, calcium, gamma glutamyltransferase, P, K, and urea nitrogen. No gross or microscopic lesions, infectious agents, or significant numbers of parasites were detected in any of the carcasses or tissues examined. The MIX group had diarrhea for much of the trial. In Trial 2, five yearling cattle were adapted to a mixture of 21% LSGH and 79% ORH. Then they were simultaneously offered three mixtures of spurge and oat haylages: 1) spurge ensiled with a microbial inoculant (LSGH); 2) spurge ensiled with the same inoculant and a cellulolytic/hemicellulolytic enzyme (ENZ); and 3) spurge ensiled with the same inoculant and molasses (MOL). The mixture with ENZ was preferred over those with MOL or LSGH (P < .001), but the amounts consumed were low and similar to those for LSGH-ORH in Trial 1 when amounts of ENZ and LSGH in the mixtures were similar. The ENZ mixture may have been more palatable than LSGH and MOL because it had less (P < .05) lactic acid, but intake of ENZ indicates that it had aversive characteristics, like LSGH. Ensiling leafy spurge did little, if anything, to improve its palatability to cattle.

Evaluation of wheat middlings as a supplement for beef cows grazing native winter range with differing forage availabilities.

We conducted two studies to compare wheat middlings as a low-protein, highly digestible fiber supplement to soybean meal and corn-soybean meal supplement for cows grazing winter range. In two 60-d winter grazing trials (December to February) cows (BW 500 kg) were allotted by age and weight to a 2 x 4 factorial with two forage availabilities and four supplements. Cows received either soybean meal (SBM), corn-soybean meal (CS), low wheat middlings (LWM), or high wheat middlings (HWM). The SBM and LWM supplements were formulated to provide the same daily CP, and CS and HWM provided the same daily CP and ME. In a 4 x 4 Latin square, four ruminally fistulated steers (BW 765 kg) received the same supplements and had free access to mature prairie hay. Cows grazing the high forage pasture gained more (P < .01) weight than cows grazing the low forage pasture. Cows supplemented with HWM gained less weight (P = .05) than cows supplemented with a similar amount of CP and ME from CS. Weight change of cows receiving SBM or LWM was similar. Increasing the amount of wheat middlings from LWM to HWM increased weight change (P = .04). In Exp. 2, SBM and LWM had similar total digestible DMI (DDMI). Steers supplemented with CS had higher total (P = .08) DDMI than HWM. Supplementation with HWM resulted in lower total (P = .02) DDMI than LWM. Response to SBM and LWM was similar. The CS and HWM resulted in beneficial performance responses as well as increasing the level of wheat middlings from low to high.

Effect of methionine addition to a urea-grain supplement on intake and digestibility of mature, dormant grasses and performance of cows grazing winter range.

A digestibility trial involving 20 Hampshire ram lambs and a 2-yr grazing study using 103 mature crossbred cows were conducted to determine the effects of methionine addition to a urea-grain supplement on intake and digestibility of dormant range grasses and on cow performance. In each trial, four treatment groups were supplemented with either a urea-grain control (CON), urea-grain plus methionine (MET, 3.3% DL-methionine), urea-grain plus inorganic sulfur (SUL, 3.0% sodium sulfate), or soybean meal (SBM). Supplements were designed to provide 45 and 360 g of CP.animal-1.d-1 (lambs and cows, respectively) and were balanced for ME, Ca, P, and K. Lambs had ad libitum access to mature prairie hay, whereas cows grazed dormant winter range from mid-November until mid-February. For the grazing study, forage OM intake (OMI) was determined in late November and in late January by the fecal output/indigestibility ratio technique. Controlled-release chromic oxide boluses were used as an external marker to estimate fecal output, and acid insoluble ash was used as an internal marker to predict OM digestibility (OMD). Mean daily DMI of mature prairie hay was 1,057 g/lamb and was not affected by supplementation. Apparent DM, NDF, and ADF digestibilities and N biological value did not differ (P > .10) among treatments. Nitrogen digestibility was increased (P = .06) for lambs fed the MET or SUL compared with CON.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of energy intake after weaning on the sexual development of beef bulls. II. Age at first mating, age at puberty, testosterone and scrotal circumference.

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effect of energy intake after weaning on rate of sexual development. For 200 d, 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Higher energy did not hasten sexual development, as measured by serum testosterone, age at first mating or age at puberty. As energy level increased, weight at puberty increased (P less than .05) for both breeds, and scrotal circumference at puberty increased (P less than .05) for Simmentals. When adjusted for breed and energy level, bulls that were heavier at 1 yr of age had larger scrotal circumference (P less than .05) and were younger at puberty (P less than .01). Bulls that had higher serum testosterone at 1 yr of age reached puberty earlier (P less than .01). At a constant age there was no relationship between testosterone and scrotal circumference. Although higher levels of energy increased scrotal circumference of Simmentals, it did not hasten sexual development for either breed.

Effect of energy intake after weaning on the sexual development of beef bulls. I. Semen characteristics and serving capacity.

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effects of energy intake after weaning, degree of fatness, and short-term weight change on reproductive characteristics of yearling beef bulls. For 200 d (ending in May), 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Bulls then were adjusted to a roughage diet for 10 d before grazing brome pasture for 38 d (ending in June). Energy level did not affect motility or sperm morphology of semen collected with an artificial vagina in May and June. High energy levels were not detrimental to bull performance during a 30-min serving-capacity test in May or June. Backfat thickness was not related to semen characteristics or serving capacity. Amount of weight lost from May to June did not affect the semen quality or serving capacity of Herefords. Those Simmental bulls that had a more positive weight change from May to June had a more favorable change in semen quality from May to June (P less than .05) due to lower semen quality in May (P less than .05). The high level of energy was not detrimental to semen characteristics or serving capacity. Some of the Simmental bulls may have been underfed for maximum semen quality at the beginning of the pasture period. Within the normal range of energy fed to beef bulls from weaning to the beginning of the breeding season as yearlings, it may be more likely to underfeed breeds of large mature size than to overfeed British breeds.