The effect of maturity at harvest on the digestibility and intake of large bale silage made from whole-crop barley and wheat when fed to growing heifers was evaluated. Two crops of spring barley (Hordeum distichum cv. Filippa and Kinnan) and 1 of winter wheat (Triticum aestivum cv. Olevin) were harvested at the heading, milk, and dough stages of maturity. The silage was fed to 36 dairy heifers in a balanced crossover experiment with 3 periods and 9 treatments (diets based on 3 crops and 3 stages of maturity), organized into 6 pairs of 3 × 3 Latin squares. No clear relationship was observed between intake and stage of maturity of whole-crop cereal silage, but intake was positively correlated to silage DM content (P < 0.001, r = 0.46) and negatively correlated to NDF content (P < 0.001, r = -0.42). Organic matter digestibility decreased between the heading and milk stages of maturity in all crops (P < 0.001), did not differ between the milk and the dough stages in the 2 barley crops, but increased in the wheat silage (P = 0.034). The NDF digestibility decreased between the heading and milk stages in all crops (P < 0.001), whereas it decreased in 1 barley crop (P < 0.001), increased in the other barley (P = 0.025), and was unchanged in the wheat between the milk and dough stages of maturity. Starch digestibility was less in the 2 barley crops compared with the wheat at the dough stage of maturity (P < 0.001). The feeding value of the whole-crop barley and wheat declined between the heading and milk stages of maturity, but thereafter the effect of maturity on the feeding value was minor.

Large variation exists in the potassium content of dairy cow feeds and also within a feed type due to soil type and fertilization. Increased ration K concentration causes a subsequent increase in urinary volume and could be expected to also lower milk urea concentration. Six multiparous mid-lactation Swedish Red dairy cows, all fitted with rumen cannulas, were subjected to 3 different levels of K intake in a Latin square experiment with three 2-wk periods to evaluate the effects on concentrations of milk urea and rumen ammonia, urinary output, and drinking water intake. The treatments were achieved by K supplementation on top of a low-K basal ration fed at individual allowances fixed throughout the experiment. The basal ration, consumed at 20.2 kg of dry matter (DM)/d, provided 165 g of crude protein/kg of DM and consisted of grass silage, concentrates, and urea in the proportions 39.3:60.0:0.7 on a DM basis. Potassium bicarbonate supplementation was 0, 616, and 1,142 g/d, respectively, to give total ration K concentrations that were low (LO; 12 g/kg of DM), medium (MED; 23 g/kg of DM), or high (HI; 32 g/kg of DM). Production and composition of milk was not affected by treatment. A linear effect on milk urea concentration was detected, being 4.48, 4.18, and 3.77 mM for LO, MED, and HI, respectively, and a linear tendency for rumen ammonia concentration with 6.65, 6.51, and 5.84 mg of NH₃-N/dL for LO, MED, and HI, respectively. Milk urea concentration peaked about 3h after the rumen ammonia peak from the morning feeding, at a level 1.3mM over the baseline. Urinary urea excretion declined linearly (105, 103, and 98 g of urea-N/d for LO, MED, and HI, respectively). Linear increases occurred in urinary output (0.058 ± 0.001 kg of urine/g of K intake; no intercept; coefficient of determination=0.997) and drinking water intake (65.9 ± 2.02 + 0.069 ± 0.004 kg of water/g of K intake; coefficient of determination=0.95). Urinary K concentration leveled off at 12.4 g/L. Urinary creatinine excretion was not affected by K addition, but allantoin excretion increased linearly by 27% from LO to HI, suggesting increased rumen microbial growth. Rumen pH, acetate proportion of total volatile fatty acids, and digestibility of DM, organic matter, and neutral detergent fiber increased linearly with increasing potassium intake. We concluded that increased ration K concentration lowers milk urea concentration with a magnitude significant for the interpretation of milk urea values, but other sources of variation, such as sampling time relative to feeding, may be even more important.

This study examined the effects of physical form and stage of maturity at harvest of whole-crop barley silage (WCBS) on feed intake, eating and rumination activity, diet selection and faecal particle size in dairy steers. Whole-crop barley was harvested and ensiled in round bales. Eight dairy steers (live weight (LW): 350 6 10 kg) in a duplicated 4 3 4 Latin square design were fed WCBS harvested at heading or dough stage of maturity in long form or chopped in a 2 3 2 factorial treatment arrangement. The WCBS was supplemented with soybean meal. Daily dry matter (DM) intake increased by 7% ( P , 0.05) due to chopping of dough-stage silage but was unaffected by chopping of heading-stage silage. The steers fed chopped, but not those fed long dough-stage silage, selected for starch in the WCBS ( P , 0.001). The neutral detergent fibre (NDF) intake was 5% higher ( P , 0.01) for heading than for dough-stage silage and was associated with lower concentration of indigestible NDF (96 v. 170 g/kg DM). Rate of intake of DM and NDF was 37% higher ( P , 0.001), daily eating time was 24% shorter ( P , 0.001) and daily chewing time was 8% shorter ( P , 0.05) for chopped silage compared with long silage but there was no effect of maturity. Daily rumination time was not affected by treatments, whereas rumination and chewing times per kg NDF intake were 15% and 13% higher ( P , 0.05), respectively, for dough-stage than for heading-stage silage. The proportion of faecal particles retained on a 1 mm screen was 30% higher ( P , 0.001) due to chopping and 45% higher ( P , 0.001) due to delayed harvest. Chopping the dough-stage silage reduced the proportion of grain in faeces from 97 to 43 g/kg DM ( P , 0.05) indicating higher starch digestibility. In conclusion, chopping increased DM intake of WCBS when harvested at dough stage but not at heading stage of maturity.

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A meta-analysis was conducted to establish linkages between crop and fermentation variables. Data from well-controlled mini silage studies were used in which no additives had been used and no ingress of air had occurred. The silage set consisted of data on crop chemical composition and epiphytic lactic acid bacteria count, and fermentation products (organic acids, alcohols, and ammonia-N) from 118 silages made from 30 grass, 7 legume, 15 grass and legume mixtures, and 66 whole-crop maize samples. The prediction models for fermentation products on crop variables were obtained by stepwise multiple regression analysis. Perennial forage and maize silages were analyzed separately. The best models were obtained for acetic acid in perennial forage silages, with a coefficient of determination of 0.63, and for lactic acid and ethanol in whole-crop maize silages, with coefficients of determination of 0.84 and 0.61, respectively. Fermentation products of perennial forage and maize silages were best related to dry matter and crude protein contents, respectively. Overall, the prediction equations were weak.