The objective of this study was to investigate the effects of different stocking densities of 82 (0.82 cows per freestall and feed bin), 100, and 129% on behavior, productivity, and comfort indices of lactating Holstein dairy cows. Twenty-seven lactating cows (15 primiparous and 12 multiparous) were assigned to 1 of the 3 treatments, which were balanced for parity, milk yield, days in milk, and body weight in a 3×3 Latin square design with 14-d periods. After 7 d of adaptation to the treatments, lying time and bouts were recorded at 1-min intervals for 3 d, DMI and feeding time were monitored electronically by feed bins, and rumination time was quantified at 2-h periods for 5 d during each period. The cow comfort index, stall standing index, stall perching index, and stall use index (SUI) were calculated using 10-min scan samples of video recording from d 8 to 10 of each period. Milk yield was recorded from d 8 to 12 and milk composition was determined from composite samples on d 12 in each period. Daily lying time, lying bouts, and bout duration did not differ among the stocking densities. The ratio of lying time ≥12 h/d (the number of cows with daily lying time ≥12 h/d divided by number of cows per pen) was higher for cows housed at 82% stocking density compared with those housed at 100% stocking density, with stocking density of 129% intermediate. Hourly lying time was lower at 100% stocking density compared with 82 and 129% stocking densities during the peak period (2300-0400 h), determined based on diurnal pattern of lying time. Daily dry matter intake, feeding time, and feeding rate were not affected by stocking density. After morning milking, dry matter intake and feeding time was reduced at 129 versus 82% stocking density during peak feeding time (0600-0800 h), determined based on diurnal patterns of feeding behavior. Stocking density had no effect on rumination time, milk yield and milk composition. The ratio of SUI ≥85% (mean of the number of SUI ≥85% divided by the number of SUI at 10-min scan samples during a 24-h period) was lower at 129 versus 82% stocking density, with stocking density of 100% intermediate. During peak lying time after evening milking (2300-0400 h), both cow comfort index and SUI were higher at 129 than at 100% stocking density. The SUI was lower 2h after morning milking (0800-0900 h) for cows housed at 129% compared with those housed at 82 and 100% stocking densities. In conclusion, when compared with 100% stocking density, understocking contributed to natural behaviors of cows that including lying, feeding, and rumination behavior, whereas overstocking did not cause negative effect on behavior, productivity, and comfort indices of cows in this study.

The aim of the study was to evaluate the effects of early feed exposure (EFE) to different feedstuffs in dairy calves on feed preference once fed a free-choice diet and a total mixed ration later in life. Thirty (30) female Holstein calves were randomly assigned at birth to 1 of 3 EFE treatments-concentrate only (CON), hay only (HO), and concentrate and hay (COH)-from d 2 to 56. After that, all calves were offered both concentrate and hay in different buckets from d 57 to 70 to allow them free choice between the 2 feedstuffs. Calves were then transferred to a heifer barn, housed within treatment in pairs (2 calves/pen), and fed TMR from d 71 to 196. Feed intake was recorded daily from d 2 to 70 to determine the feed preference before and after weaning. Fresh TMR and orts were collected daily in the last week of the experiment (d 190 to 196) for analysis of feed sorting and intake. Body weight and structural growth were recorded at d 1, 28, 56, 70, and 190. Blood for determining glucose and rumen fluid for determining ruminal pH and volatile fatty acids concentrations were sampled on d 28, 56, 70, and 190. Early feed exposure did not affect feed intake, body weight, average daily gain, blood glucose, and structural growth before and after weaning but did affect feed preference and rumen fermentation. After transition to a free-choice diet, HO calves consumed more hay (550.2 g/d) than CON (177.4 g/d) and COH (396.4 g/d) calves on the first day only. However, COH calves consumed a greater amount of hay, resulting in a higher ratio of hay to total solids compared with either CON or HO calves during d 57 to 70. Upon transition to a TMR, a similar sorting pattern was exhibited between treatments, with calves sorting against the long and for the fine particle fractions. Although no significant long-term effects of different EFE on rumen pH, volatile fatty acids, and blood glucose persisted at wk 27 (from d 190 to 196), calves exposed to COH early had an improved ability to sort for long feed particles compared with CON and HO calves later in life. Our results suggest that EFE could influence choice of feed immediately after weaning and may have long-lasting effects on feed preference in heifers later in life. Further studies with more calves are recommended.

The aim of this study was to evaluate the effects of antibiotic residues in milk on growth, ruminal fermentation, and microbial community of dairy calves in their first 35 d of age. Twenty newborn Holstein bull calves were assigned to 1 of 2 treatments equally: milk replacer without antibiotics (control) and milk replacer plus 4 antibiotics: 0.024 mg/L of penicillin, 0.025 mg/L of streptomycin, 0.1 mg/L of tetracycline, and 0.33 mg/L of ceftiofur (ANT). Starter intake and fecal consistency scores of each calf were recorded on a daily basis. Body weight, withers height, body length, and heart girth were measured on d 1, 7, 14, 21, 28, and 35 before feeding in the morning. Rumen fluid was collected on d 15, 25, and 35 to determine ruminal pH, volatile fatty acids (VFA), and NH 3 -N concentrations. A total of 10 (5 per treatment) samples of rumen fluid taken on d 35 were analyzed for microbial community. Rumen tissues from the cranial ventral sac and cranial dorsal sac were collected from 8 calves of each group for morphology analysis on d 35 after being harvested. The results showed that calves in 2 treatments had similar starter intake, body weight, withers height, body length, heart girth, and average daily gain. The ANT group showed a lower diarrhea frequency in wk 4, and no differences were found for other weeks. Calves in the ANT group exhibited a greater concentration of acetic acid in the rumen and no differences for other VFA, total VFA, rumen pH, or NH 3 -N. As for rumen morphology, the length of papillae from cranial ventral sac of the ANT group was longer than that of the control group. The results of ruminal microbial community showed that antibiotic residues had minor effects on bacteria phyla and bacteria diversity. At the genus level, calves in the ANT group showed lower richness of Prevotella and higher richness of Acetitomaculum. In conclusion, antibiotic residues stimulated the development of ruminal papillae and increased the production of acetic acid in rumen, which might be caused by the influence of antibiotics on the ruminal microbial community.

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The objective of this study was to measure the effects of partially replacing wild rye (Leymus chinensis; WR), corn silage (CS), or corn grain (CG) in dairy cow diets with CaO-treated corn stover (T-CS) and corn dried distillers grains with soluble (DDGS) on performance, digestibility, blood metabolites, and income over feed cost. Thirty tonnes of air-dried corn stover was collected, ground, and mixed with 5% CaO. Sixty-four Holstein dairy cows were blocked based on days in milk, milk yield, and parity and were randomly assigned to 1 of 4 treatments. The treatments were (1) a diet containing 50% concentrate, 15% WR, 25% CS, and 10% alfalfa hay (CON); (2) 15% WR, 5% CG, and 6% soybean meal were replaced by 15% T-CS and 12% DDGS (RWR); (3) 12.5% CS, 6% CG, and 5% soybean meal were replaced by 12.5% T-CS and 12%DDGS (RCS); (4) 13% CG and 6% soybean meal were replaced by 7% T-CS and 13% DDGS (RCG). Compared with CON treatment, cows fed RCS and RCG diets had similar dry matter intake (CON: 18.2 ± 0.31 kg, RCS: 18.6 ± 0.31 kg, and RCG: 18.4 ± 0.40 kg). The RWR treatment tended to have lower dry matter intake than other treatments. The inclusion of T-CS and DDGS in treatment diets as a substitute for WR, CS, or CG had no effects on lactose percentage (CON: 4.96 ± 0.02%, RWR: 4.97 ± 0.02%, RCS: 4.96 ± 0.02%, and RCG: 4.94 ± 0.02%), 4% fat-corrected milk yield (CON: 22.7 ± 0.60 kg, RWR: 22.1 ± 0.60 kg, RCS: 22.7 ± 0.60 kg, and RCG: 22.7 ± 0.60 kg), milk fat yield (CON: 0.90 ± 0.03 kg, RWR: 0.86 ± 0.03 kg, RCS: 0.87 ± 0.03 kg, and RCG: 0.89 ± 0.03 kg), and milk protein yield (CON: 0.74 ± 0.02 kg, RWR: 0.72 ± 0.02 kg, RCS: 0.73 ± 0.02 kg, and RCG: 0.71 ± 0.02 kg). Cows fed the RWR diet had higher apparent dry matter digestibility (73.7 ± 1.30 vs. 70.2 ± 1.15, 69.9 ± 1.15, and 69.9 ± 1.15% for RWR vs. CON, RCS, and RCG, respectively) and lower serum urea N (3.55 ± 0.11 vs. 4.03 ± 0.11, 3.95 ± 0.11, and 3.99 ± 0.11 mmol/L for RWR vs. CON, RCS, and RCG, respectively) than cows fed other diets. No significant differences were noted in apparent neutral detergent fiber digestibility among the treatments. Compared with CON treatment, the RWR, RCS, and RCG treatments generated an additional $0.77, $0.70, and $0.81 income over feed cost per cow per day, respectively. In conclusion, feeding diets containing a portion of T-CS and DDGS can improve profitability of the treatment groups without negatively affecting the lactation performance of mid- to late-lactation cows.