The present experiment was performed to assess the effects of different sources of milk on the growth performance, serum metabolism, immunity, and intestinal development of calves. Eighty-four Holstein male neonatal calves were assigned to one of the following four treatment groups: those that received bunk tank milk (BTM), untreated waste milk (UWM), pasteurized waste milk (PWM), and acidified waste milk (AWM) for 21 d. Calves in the BTM and AWM groups consumed more starter (P < 0.05) than those in the UWM group. Average daily gain in the UWM group was the highest (P < 0.05). Calves exhibited the highest (P < 0.05) serum total protein, albumin, total cholesterol, high density lipoprotein, triglycerides, growth hormone, immunoglobulin (Ig) A and IgM concentrations in the UWM group, highest malondialdehyde and tumor necrosis factor-α in the PWM group (P < 0.05), and highest glutathione peroxidase and IgG in the BTM group (P < 0.05). The jejunum and ileum of the calves in all treatments presented a slight inflammatory response. The jejunal inflammation scores were higher (P < 0.05) in the UWM and AWM groups than the BTM group; the ileal inflammation scores increased more (P < 0.05) in the AWM group than the BTM group. Jejunal immunohistochemical scores (IHS) were higher (P < 0.05) in the PWM and AWM groups than the BTM group. Compared to the other three groups, calves feeding on BTM had lower (P < 0.05) ileal IHS. Jejunal interleukin(IL)-1β, IL-8, and IL-10 mRNA expression in the UWM group was the highest (P < 0.05). Calves fed AWM increased (P < 0.05) mRNA expression of IL-8 and toll like receptor 4 (TLR-4) in the jejunum and IL-8, IL-1β, IL-6, IL-8, and IL-10 in the mesenteric lymph nodes. Overall, bunk tank milk is the best choice for calf raising compared to waste milk. The efficiency of feeding pasteurized and acidified waste milk are comparable, and the acidification of waste milk is an acceptable labor-saving and diarrhea-preventing feed for young calves.

Ketosis is one of the most prevalent and complex metabolic disorders in high-producing dairy cows and usually detected through analyses of β-hydroxybutyrate (BHB) concentration in blood. Our main objectives were to evaluate genetic parameters for blood BHB predicted based on Fourier-transform mid-infrared spectra from 5 to 305 d in milk, and estimate the genetic relationships of blood BHB with 7 reproduction traits and 6 longevity traits in Holstein cattle. Predicted blood BHB records of 11,609 Holstein cows (after quality control) were collected from 2016 to 2019 and used to derive 4 traits based on parity number, including predicted blood BHB in all parities (BHBp), parity 1 (BHB1), parity 2 (BHB2), and parity 3+ (BHB3). Single- and multitrait repeatability models were used for estimating genetic parameters for the 4 BHB traits. Random regression test-day models implemented via Bayesian inference were used to evaluate the daily genetic feature of BHB variability. In addition, genetic correlations were calculated for the 4 BHB traits with reproduction and longevity traits. The heritability estimates of BHBp, BHB1, BHB2, and BHB3 ranged from 0.100 ± 0.026 (± standard error) to 0.131 ± 0.023. The BHB in parities 1 to 3+ were highly genetically correlated and ranged from 0.788 (BHB1 and BHB2) to 0.911 (BHB1 and BHB3). The daily heritability of BHBp ranged from 0.069 to 0.195, higher for the early and lower for the later lactation periods. A similar trend was observed for BHB1, BHB2, and BHB3. There are low direct genetic correlations between BHBp and selected reproductive performance and longevity traits, which ranged from -0.168 ± 0.019 (BHBp and production life) to 0.157 ± 0.019 (BHBp and age at first calving) for the early lactation stage (5 to 65 d). These direct genetic correlations indicate that cows with higher BHBp (greater likelihood of having ketosis) in blood usually have shorter production life (-0.168 ± 0.019). Cows with higher fertility and postpartum recovery, such as younger age at first calving (0.157 ± 0.019) and shorter interval from calving to first insemination in heifer (0.111 ± 0.006), usually have lower BHB concentration in the blood. Furthermore, the direct genetic correlations change across parity and lactation stage. In general, our results suggest that selection for lower predicted BHB in early lactation could be an efficient strategy for reducing the incidence of ketosis as well as indirectly improving reproductive and longevity performance in Holstein cattle.

A study using four Holstein cows with ruminal cannulas was conducted to evaluate the degradability of different moisture content or particle size of maize silage and alfalfa haylage. The maize silage (MS; 20-mm length) and alfalfa haylage (AH; 40-mm length) samples were wet (wet maize silage, MSW; wet alfalfa haylage, AHW), dried (dried maize silage, MSD; dried alfalfa haylage, AHD), or ground to pass through a 2.5-mm screen (dried ground maize silage, MSG; dried ground alfalfa haylage, AHG). Samples were incubated in the rumen for 2, 6, 12, 24, 36, 48, and 72 h. Cows were fed ad libitum and allowed free access to water. High moisture content treatment of MSW expressed a lower rinsing NDF and ADF degradability at 2 h (P < 0.05) compared with dried samples (MSD and MSG). Different moisture content and particle size had a significant impact (P < 0.05) on the NDF degradability at 72 h, ADF degradability at 36, 48, and 72 h, and ruminally degradable ADF. All of the highest values were observed in small particle size and low moisture content AHG treatment. Based on this study, sample processing, such as drying and grinding, should be considered when evaluating nutritive values of forages.

Mid-lactation represents a critical production phase for high-yield dairy cows, where nutrient imbalance can compromise animal health and farm profitability. This study investigated the effects of dietary alkaline mineral complex (AMC)–water supplementation on milk yield, blood biochemistry, oxidative stress, immunity, hormone secretion and ion status in mid-lactation dairy cows. A total of 120 high-yield mid-lactation Holstein cows were stratified into three milk yield subgroups (EHYG, HYG, MHYG) based on pre-experimental milk yield records. Within each yield stratum, 20 cows were randomly assigned to either the control group or the AMC-supplemented group, resulting in three control subgroups and three AMC-supplemented subgroups (n = 20 per subgroup). Controls received a basal diet, while cows in experimental groups received the basal diet supplemented with diluted AMC concentrate solution (1:4 concentrate to water, v/v) for 90 d. Blood samples were collected on days 0, 15, 30, 45, 60 and 90, and milk samples were obtained on days 0, 30, 60 and 90 to evaluate the production performance, stress and immune status. Dietary AMC supplementation reduced plasma NEFA (p < 0.01) and BHBA concentrations (p < 0.05). For hormone, oxidative-stress and immune indices, significant differences were detected only at discrete individual sampling time points, with no consistent overall treatment effects across the entire experimental period. No significant overall treatment effect of AMC supplementation was observed on the milk yield. These results provide preliminary reference data for alkaline mineral complex additive application in practical mid-lactation dairy production.