Thirty-four mature Holstein cows were blocked into two groups on their 305-day, twice daily milked, mature equivalent milk production of the previous lactation; groups were assigned at random to a twice or thrice daily milking frequency. In addition, six pairs of paternal half-sisters and one pair of nonsibling heifers also were assigned to twice daily or thrice daily milking frequency. Half-sisters were assigned to milking frequency on alternate calvings, and the nonsibling pair was assigned at random. Milk production peaked at 6 wk lactation in mature cows in both treatments, at 7 wk for cows in first lactation milked twice daily, and at 9 wk for cows in first lactation milked thrice daily. Cows milked thrice daily reached higher peak milk production and were more persistent in milk production. Multiparous and first-lactation cows milked thrice daily produced 18.5 and 25.2% more milk than their counterparts milked twice daily, and after 15 wk heifers milked thrice daily were producing more milk per day than mature cows milked twice daily. The combined increased average production for cows and heifers milked thrice daily, 1299 kg, required only 92 kg more dry matter intake and resulted in an apparent preferential utilization of feed nutrients for milk production or higher rate of tissue catabolism in cows milked thrice daily. Milk composition was not influenced by milking frequency; total milk fat was 36 kg more for cows milked thrice daily. Reproductive performance measured as days to first estrus, days open, or services per conception also was not influenced by milking frequency.

Livestock do not like to graze high‐tannin (HT) sericea lespedeza [Lespedeza cuneata (Dum‐Cours) G. Don], but readily consume it as hay. Intake and digestibility of fresh‐frozen (FF) and field‐dried (FD) HT and low‐tannin (LT) sericea were studied in a feeding trial with sheep (Ovis spp.) in a 2 ✕ 2 factorial with a 4 ✕ 4 Latin square arrangement of treatments. Tannin concentrations were 181,87,31, and 44 g kg‐1 for HT‐FF, LT‐FF, HT‐FD, and LT‐FD sericea, respectively. There was no difference in digestibility due to preservation method, but HT‐FF was less digestible than LT‐FF [forage ✕ preservation method (P < 0.05)]. Digestibility of neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, lignin, N, neutral detergent insoluble N, acid detergent insoluble N (ADIN), and intake of HT‐FF sericea were lower than LT‐FF or the FD forages. Decreased intake and digestibility of HT‐FF sericea were related to the high tannin concentration. Elevated fecal recovery of lignin and ADIN in sheep fed HT‐FF forage resulted in negative digestibilities and may be related to formation of insoluble tannin‐protein complexes in the digestive tract. Field drying decreased analyzable tannin concentration in HT sericea.

Leaves of ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) and ‘Coastal’ bermudagrass (Cynodon dactylon (L) Pers.) were studied to relate microanatomical differences to differences in degradation. Leaf sections of each grass were incubated with rumen microorganisms for various times and examined using the scanning electron microscope. Data reveal that tall fescue is degraded more rapidly and extensively than Coastal bermudagrass. These differences agree with in vitro dry matter disappearance investigations conducted on leaf tissue of each grass. Portions of the lignified structures in tall fescue appear to be removed after a 72‐hour incubation, whereas all lignified tissues in Coastal bermudagrass are completely undegraded at this time. Data indicate that the amounts of particular tissues in grass leaves affect the rate of tissue degradation.

Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

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