This study evaluated the effects of feeding diets that were formulated to contain similar proportions of undigested neutral detergent fiber (uNDF) from forage, with wheat straw (WS) substituted for corn silage (CS), alfalfa hay (AH), or both. The diets were fed to lactating dairy cows and intake, digestibility, blood metabolites, and milk production were examined. Thirty-two multiparous Holstein cows (body weight = 642 ± 50 kg; days in milk = 78 ± 11 d; milk production = 56 ± 6 kg/d; mean ± standard deviation) were used in a randomized block design with 6-wk periods after a 10-d covariate period. Each period consisted of 14 d of adaptation followed by 28 d of data collection. The control diet contained CS and AH as forage sources (CSAH) with 17% of dietary dry matter as uNDF after 30 h of incubation (uNDF30). Wheat straw was substituted for AH (WSCS), CS (WSAH), or both (WSCSAH) on an uNDF30 basis, and beet pulp was used to obtain similar concentrations of NDF digestibility after 30 h of incubation (NDFD30 = 44.5% of NDF) across all diets. The 4 diets also contained similar concentrations of net energy for lactation and metabolizable protein. Dry matter intake was greatest for WSCS (27.8 kg/d), followed by CSAH (25.7 kg/d), WSCSAH (25.2 kg/d), and WSAH (24.2 kg/d). However, yields of milk, 3.5% fat-corrected milk (FCM), and energy-corrected milk did not differ, resulting in higher FCM efficiency (kg of FCM yield/kg of dry matter intake) for WSAH (1.83) and WSCSAH (1.79), followed by CSAH (1.69) and WSCS (1.64). Milk protein percentage was greater for CSAH (2.84%) and WSCS (2.83%) than for WSAH (2.78%), and WSCSAH (2.81%) was intermediate. The opposite trend was observed for milk urea nitrogen, which was lower for CSAH (15.8 mg/dL), WSCS (15.8 mg/dL), and WSCSAH (17.0 mg/dL) than for WSAH (20 mg/dL). Total-tract NDF digestibility and ruminal pH were greater for diets containing WS than the diet without WS (CSAH), but digestibility of other nutrients was not affected by dietary treatments. Cows fed WSAH had less body reserves (body weight change = -13.5 kg/period) than the cows fed the other diets, whereas energy balance was greatest for those fed WSCS. The results showed that feeding high-producing dairy cows diets containing different forage sources but formulated to supply similar concentrations of uNDF30 while maintaining NDFD30, net energy for lactation, and metabolizable protein constant did not influence milk production. However, a combination of WS and CS (WSCS diet) compared with a diet with CS and AH improved feed intake, ruminal pH, total-tract NDF digestibility, and energy balance of dairy cows.

This study examined the feeding effects of wheat straw (WS) and beet pulp (BP) substituted for corn silage (CS) and alfalfa hay (AH) based on forage 30-h undigested neutral detergent fiber (uNDF30) on lactation performance in high-producing dairy cows. Twelve multiparous (body weight = 611 ± 31 kg, days in milk = 97 ± 13; 51 ± 3 kg/d of milk; mean ± standard error) Holstein cows were used in a replicated 3 × 3 Latin square design with 28-d periods. Three treatments were established by substituting WS for CS and AH such that the concentration of forage uNDF30 in all diets was the same. The treatments were (1) 0% forage uNDF30 from WS (WS0; control), (2) 50% forage uNDF30 from WS (WS50), and (3) 100% forage uNDF30 from WS (WS100). Beet pulp was added in the straw diets to achieve similar dietary neutral detergent fiber digestibility after 30-h incubation (NDFD30). The 3 diets were similar in forage uNDF30 (14% of dry matter), total uNDF30 (∼18.5% of dry matter), and NDFD30 (approximately 42% of neutral detergent fiber). The substitution of WS and BP for AH and CS decreased the proportion of forage (40, 31, and 22.3% of dry matter) and forage neutral detergent fiber (21.2, 19.7, and 18.3% of dry matter) for WS0, WS50, and WS100, respectively, in the diet. However, the substitution linearly increased mean rumen pH (5.90, 6.09, and 6.28 for WS0, WS50, and WS100, respectively), digestibility of nutrients, and selection for long particles of diets without affecting dry matter intake. The substitution also linearly increased cholesterol and blood urea nitrogen concentration in the blood. Milk fat percentage, fat production, fat:protein ratio, and milk urea nitrogen increased linearly when treatments changed from WS0 to WS100, whereas the production of energy-corrected milk (ECM) was not affected by the treatments. Milk yield and milk protein yield were affected in a curvilinear manner and were lower in WS100 than other treatments. The efficiency of ECM production linearly increased in the diet with higher inclusion of WS and BP substitution in the diet (1.66, 1.70, and 1.72 for WS0, WS50, and WS100, respectively), but body weight, body weight change, and backfat thickness of cows were not different among treatments. In conclusion, the substitution of WS and BP for CS and AH with fixed uNDF30 improved feed efficiency and rumen pH, decreased milk and protein yield, and did not affect ECM yield.

Summary: Feeding behavior and ruminal fermentation characteristics of lactating cows were investigated when offered rations supplying similar forage undigested neutral detergent fiber (NDF) and dietary NDF digestibility (both measured after 30 hours of in situ incubation). Diets contained wheat straw (WS) and beet pulp (BP), which replaced corn silage and alfalfa hay. Time spent eating decreased linearly and rumination activity remained unaffected as the proportion of WS and BP increased. This resulted in a linear reduction in chewing behavior.

This study evaluated the efficacy of Eucalyptus globulus essential oil (EEO) supplementation in attenuating ascites incidence and physiological disturbances in broiler chickens exposed to a cold-induced pulmonary hypertension syndrome model. A total of 720 one-day-old male Ross 308 chicks were randomly assigned to six dietary treatments, each with six replicates of 20 birds. The thermoneutral control group received a basal diet under standard conditions (32°C on day 1, gradually reduced to 23°C by day 20 and maintained until day 42; relative humidity [RH] 50-60 %), whereas the remaining five groups were exposed to cold stress (temperature reduced by 4°C/day from day 11 until reaching 15°C, then maintained at 10-15°C until day 42, RH 55-65 %) to induce ascites, and were fed the basal diet supplemented with 0, 500, 1000, 1500, or 2000 mg/kg EEO. Cold stress decreased body weight gain and feed intake and increased ascites-related mortality (P < 0.05). It also elevated erythrocyte count, hemoglobin concentration, and hematocrit, while reducing pO₂ and O₂ saturation and inducing right ventricular hypertrophy (P < 0.05). In contrast, inclusion of EEO in the diet linearly improved body weight gain, partially restored hematological parameters, and favorably modulated blood gas values compared with the unsupplemented cold-stressed group (P < 0.05). Cold stress also suppressed superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in plasma and heart tissue, increased malondialdehyde (MDA) concentrations, and lowered plasma nitric oxide (NO) levels (P < 0.05). Dietary supplementation with EEO linearly increased SOD and GPx activities and plasma NO concentrations, while reducing MDA content (P < 0.05). Although EEO supplementation improved growth performance and physiological responses in cold-stressed broilers, values did not fully return to thermoneutral levels. Overall, these findings highlight the potential of EEO as a functional dietary additive to mitigate the adverse effects of cold-induced ascites and oxidative stress in broiler chickens.

Feeding behaviour and ruminal fermentation of dairy cows were evaluated when fed diets formulated to supply a similar proportion of undigested neutral detergent fibre (uNDF) after 30-h incubation (uNDF₃₀), while wheat straw (WS) replaced for corn silage (CS), alfalfa hay (AH) or both. In a randomised block design, 32 multiparous Holstein cows (days in milk = 78 ± 11 d, milk production = 56 ± 6 kg/d) were used. AH and CS were the only forage sources in control diet (CSAH). WS was substituted for alfalfa hay (WSCS), CS (WSAH) or both (WSCSAH) on uNDF₃₀ basis. Dry matter consumption from 6 to 24 h after feed delivery was lower in WSAH than in WSCS or CSAH. No difference existed in total time spent for eating (250 min/d), rumination (460 min/d) and chewing (710 min/d). Total concentration of volatile fatty acids (VFAs) in the rumen was not different between treatments but propionate proportion was lower for cows fed WSAH than CSAH diet (19.0 vs. 24.1 mM/100 mM). Ammonia nitrogen concentration in the rumen fluid was greater for WSAH than WSCS or CSAH. With combining uNDF₂₈₈ and peNDF, peuNDF₂₈₈ was calculated and its intake had the highest correlation with chewing time (r = −0.60), sorting index of particles retained on 8-mm sieve (r = 0.42) and rumen pH (r = 0.52). Forage replacement on uNDF₃₀ basis resulted in a relatively similar response on feeding behaviours and ruminal fermentation and enabled to replace high-quality forages with low-quality forages in the dairy cow rations.