Heat stress (HS) in dairy cows can be classified into short-term heat stress (STHS) and long-term heat stress (LTHS) according to the number of consecutive days in HS. The comparative study of these 2 types of HS is limited in terms of their effects on the production and energy metabolism of cows. In this study, 4 lactating Holstein cows (102.5 ± 12 days in milk, 605 ± 22 kg of body weight, second parity) fitted with rumen fistulae were randomly assigned to 1 of 2 groups in a 2 × 2 crossover design and allocated to 1 of 2 climate-controlled chambers. This study contained 2 periods, each with a control phase and a HS phase. There was a recovery phase between 2 periods. The HS phase comprised either STHS (3 d) or LTHS (7 d) treatments. Data collected from the 3 d of STHS and the last 3 d of LTHS were compared. The chambers were set at thermal neutral conditions (20°C, 50% humidity) during the control and recovery phases or cyclical HS conditions (26-38°C, 50% humidity) during the HS phase. Compared with STHS, LTHS decreased milk yield by 17.2% and dry matter intake by 12.6%, indicating that LTHS caused a more severe decline in milk production and feed intake. In addition, LTHS decreased milk protein concentration by 6.8% and milk protein yield by 22.4%. In comparison with STHS, LTHS decreased rumen liquor volatile fatty acid (29.7%), blood glucose (11.6%), and nonesterified fatty acid (13.6%) concentrations, but increased milk urea nitrogen by 15.1%, blood urea nitrogen by 8.6%, and creatine concentrations by 15.4%. Our results suggest that although reduced feed intake may be mainly responsible for reduced milk production during STHS, impaired rumen metabolism and suppressed mobilization of adipose tissue could be the main reasons for further reduction in milk yield during LTHS.

This study used Rhodobacter sphaeroides protein (RSP) as an innovative dietary protein source for Holstein dairy calves. We investigated its effects on growth performance, nutrient digestibility, rumen fermentation, and serum metabolites, antioxidants, immunoglobulins, and inflammatory factors. A total of 45 female Holstein calves (mean ± SD, 36.54 ± 1.68 kg of BW; 1 d of age) were randomly assigned to 3 treatment groups and fed either a control diet (CON) or diets with 5.89% or 11.49% RSP (RS1 and RS2, respectively) on a diet DM basis for 14 wk. The inclusion of RSP linearly increased BW and ADG, whereas it quadratically decreased DMI. There was a quadratic effect for gain-to-feed ratio and hip height, with higher mean values for the RS1 group. In addition, the dietary RSP tended to result in a linear increase in the overall withers height and postweaning heart girth. The dietary RSP reduced linearly the digestibility of DM and OM and tended to reduce linearly the digestibility of NDF and ADF. The levels of rumen butyrate showed a linear decrease in RSP calves. There was a quadratic effect for serum aspartate aminotransferase, with the highest value being for RS2 group. Increasing dietary RSP quadratically affected serum triglyceride levels, with the highest value being for the RS1 group. Meanwhile, serum alanine aminotransferase levels were quadratically decreased by RSP, with the RS1 group having the lowest levels. A quadratic trend effect was observed for serum albumin and total protein, with the highest values being in the RS1 group. The levels of lactate dehydrogenase, BUN, malondialdehyde, IL-10, and immunoglobulins decreased linearly with RSP. In contrast, total antioxidant capacity and the levels of superoxide dismutase, catalase, tumor necrosis factor-α, IL-8, and IL-6 increased linearly. In addition, the serum levels of low- and high-density lipoprotein, cholesterol, IL-4, IL-22, and glutathione peroxidase tended to increase linearly with the inclusion of dietary RSP. In conclusion, dietary inclusion of RSP in dairy calves reduced DMI, nutrient digestibility, and serum immunoglobulins levels, particularly at higher inclusion rates, whereas it improved ADG and antioxidant capacity.

This study aimed to evaluate the effect of substituting soybean meal (SBM) with vitamin B₁₂ fermentation waste (VFW) on growth performance, nutrient digestibility, immune response, ruminal fermentation characteristics and microbiota in finishing lambs. Forty-eight male Hu lambs aged 80 ± 4 d, with an initial body weight of 26.5 ± 0.59 kg, were randomly assigned to one of the four groups (n = 12): Control, receiving a basal diet, while the other three groups were treated with 20% (low), 40% (medium) and 60% (high) VFW instead of SBM, with a 14-d adaptation and 56-d collection of data and samples. Feeding diets supplemented with VFW quadratically changed the dry matter intake (P = 0.045) and linearly increased the feed conversion ratio (FCR) of lambs (P = 0.048). Furthermore, the digestibility of neutral detergent fiber decreased with VFW supplementation (P = 0.034). Dietary VFW did not change blood metabolite concentrations. However, increasing doses of VFW linearly increased the concentrations of immunoglobulin M and total superoxide dismutase (P < 0.05) and linearly decreased the concentration of catalase (P = 0.030). Increasing dietary VFW doses linearly elevated ruminal pH, ammonia nitrogen, as well as the proportion of isobutyrate (P < 0.05), while linearly decreasing the concentration of total volatile fatty acid (P < 0.001). The ruminal alpha diversity indexes remained unaffected by VFW, whereas principal coordinates analysis (PCoA) based on unweighted UniFrac illustrated distinct separation of the ruminal clustering regarding bacterial microbiota between Control and VFW. At the phylum level, VFW increased the Bacteroidota abundance (P = 0.034) and decreased the Firmicutes abundance (P = 0.013), thereby reducing the Firmicutes-to-Bacteroidota ratio (F:B ratio; P = 0.031). At the genus level, VFW supplementation increased the abundances of Prevotella, Selenomonas, Bacteroidaceae _unclassified and Erysipelatoclostridiaceae _ UCG-004 (P < 0.05), while decreasing the abundances of Rikenellaceae _RC9_gut_group, NK4A214_group, Veillonellaceae _ UCG-001, Christensenellaceae _R-7_group, WCHB1-41_unclassified, Butyrivibrio, and [Eubacterium]_coprostanoligenes_group_unclassified (P < 0.05). Together, dietary VFW can reduce FCR and ruminal fermentation in a dose-dependent manner, while improving immune response and altering the ruminal bacterial composition in lambs. The findings indicate the potential of VFW as an alternative to SBM for sheep production.

This study was conducted to investigate the effects of coenzyme Q10 (CoQ) dietary supplementation on growth performance, rumen fermentation, diarrhea frequency, and serum biochemical metabolites of pre-weaned Holstein dairy calves. Forty-five Holstein female calves (37.86 ± 2.38 kg of body weight [BW]; 1 d of age) were randomly assigned into 1 of the 3 treatments: a control group (Q0; without CoQ supplementation) and CoQ supplementation at low dose (Q50; 50 mg/kg dry matter [DM] of CoQ) or high dose (Q100; 100 mg/kg of CoQ) (n = 15). All experimental calves were fed pasteurized whole milk twice daily (06:30 and 17:00) starting from d 2 of age. From d 61 to 70, the calves were gradually weaned following a step-down approach. Calves had free access to clean water and the starter diet, which was introduced from d 7 onward. The study terminated on d 70. The results showed that calves supplemented with both low and high doses of CoQ had significantly higher average daily gain (linear, P = 0.007) and dry matter intake (DMI, linear, P < 0.001) compared with the Q0 group. There was a treatment by age interaction for BW (P < 0.001), where BW at 10 weeks of age was greater at Q50 and Q100 groups than at the Q0 group. Diarrhea frequency from 1 to 5 weeks of age was significantly affected by treatment (P = 0.026), with Q100 calves showing the lowest values. At 10 weeks of age, the Q100 calves showed higher serum total antioxidant capacity (linear, P = 0.012), superoxide dismutase (linear, P = 0.018), glutathione peroxidase (linear, P = 0.012), and β-hydroxybutyrate (linear, P = 0.006) compared with the Q0 group. The serum malondialdehyde was lower in Q100 calves than Q0 calves (linear, P = 0.015). Compared with the Q50 and Q0 groups, serum contents of insulin, growth hormone, and non-esterified fatty acids increased in calves receiving high CoQ dose (linear, P = 0.006, 0.012, 0.006, respectively). Conversely, the Q50 calves showed higher serum glucose compared with the other treatments (quadratic, P = 0.003). The results of the present study suggest that the supplementation of CoQ to milk may promote growth performance, health status, blood metabolites, and hormones, and improve the antioxidant capacity of the Holstein dairy calves. The use of CoQ may be an alternative to feeding antibiotics at 100 mg/kg DM to improve calf health and decrease diarrhea frequency.