Influence of low phosphorus intake during early lactation on apparent digestibility of phosphorus and bone metabolism in dairy cows

In this study, the effects of reducing the dietary phosphorus (P) supply during the first 4 months of lactation on P balance and bone metabolism were investigated in dairy cows during a full lactation, including the dry period. Twenty-two multiparous cows of the Swedish Red and White Breed were included in the experiment. Eleven cows received a dietary P concentration of 0.43% of DM during the whole lactation (NP), and 11 cows received a dietary P concentration of 0.32% of DM during the first 4 months of lactation, followed by 0.43% of DM during the rest of lactation (LP). Total collection of faeces was carried out during five different stages of lactation, for 5 consecutive days at each occasion. The dynamics of bone metabolism was investigated by monitoring one bone-formation marker, identifying osteocalcin (OC), and one bone-resorption marker identifying C-telopeptide fragments of collagen type I (CTx) in blood plasma. At the two first collection periods, 3–7 and 11–15 weeks after parturition, the apparent digestibility of P was higher in the LP cows (52%) than in the NP cows (42%). During the following collection periods, no difference in the apparent digestibility could be noted between the two groups of cows. Phosphorus retention did not differ between treatments at any collection period. The highest retention was observed during late lactation and during the dry period. The profiles of the bone metabolism markers indicated a net resorption of bone during early lactation, but there were no differences in marker concentrations between the groups during early lactation, indicating that the LP diet did not induce a further elevated net bone resorption.     

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background：Phosphorus（P） supplementation is costly and can result in excess P excretion.This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.Method：Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield,and assigned randomly to one of the three dietary treatments：0.37,0.47,and 0.57%P（DM basis）;these P levels represent the NRC recommendations,Chinese recommendations,and the amount of dietary P commonly fed by Chinese dairy farmers,respectively.Average daily feed intake was calculated from monthly data on feed offered and refused.Milk yields of individual cows were recorded weekly,and milk samples were taken for analysis of protein,fat,solids-not-fat,lactose,and somatic cell count.Blood samples were collected on days-6,-3,0,3,6 relative to calving,and then monthly throughout lactation,and analyzed for P and Ca concentrations.Spot samples of feces and urine were collected for 3 consecutive d during weeks 12,24,and 36,and P concentrations were analyzed.Reproduction and health data were recorded.Results：Dietary P did not affect dry matter intake or milk yield（P〉 0.10）.Milk fat content was slightly higher in cows fed 0.37%P than in cows fed 0.47%P（P = 0.05）.Serum concentrations of P and Ca did not reflect dietary P content（P〉 0.10）.Fecal and urinary P both declined linearly（P〈 0.05） as dietary P decreased from 0.57 to0.37%.Fecal P content was 25%less when dietary P was 0.37%compared to 0.57%.Health events and reproductive performance were not associated with dietary P content（P〉 0.05）.Conclusions：Lowering dietary P from 0.57 to 0.37%did not negatively affect milk production,but did significantly reduce P excretion into environment.     

Relationship among blood indicators of lipomobilization and hepatic function during early lactation in high-yielding dairy cows

Blood indicators are used as a tool to diagnose metabolic disorders. The present work was conducted to study the relationships among blood indicators of lipomobilization and hepatic function in high-yielding dairy cows. Two groups of Holstein cows were studied: 27 early lactation cows and 14 mid lactation cows from four different herds with similar husbandry characteristics in Galicia, Spain. Blood samples were obtained to measure beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), and the activity of aspartate transaminase (AST) and gamma-glutamyl transferase. Cows in early lactation had higher levels of BHB and NEFA than mid lactation cows. High lipomobilization (NEFA > 400 µmol/L) was detected in 67% and 7% of early lactation and mid lactation cows, respectively, while subclinical ketosis (BHB > 1.2 mmol/L) was detected in 41% and 28% of the early lactation and lactation cows, respectively. TG concentrations were low in all cows suffering subclinical ketosis and in 61% of the cows with high lipomobilization. During early lactation, 30% of cows suffered hepatic lipidosis as detected by levels of AST. Compromised hepatic function was observed in early lactation cows as shown by lower concentrations of glucose, total protein, and urea.     

The change of dry matter intake, milk yield and bone turnover in primiparous cows compared to multiparous cows during early lactation

Data from six primiparous and nine multiparous Holstein cows were used to clarify the difference of Ca and P mobilization between primiparous and multiparous cows during early lactation. The dry matter intake (DMI) of primiparous cows was lower (P < 0.01) than those of multiparous cows. Milk yield was lower in primiparous cows at 7, 14, 21 (P < 0.01), and 28 days (P < 0.05) after parturition. There was no significant difference in milk Ca and P concentrations between primiparous and multiparous cows. There were no significant differences in plasma Ca and P concentrations between primiparous and multiparous cows. The plasma P level at 7 days postpartum in primiparous cows was lower (P < 0.05) than 28 days postpartum. The concentration of plasma osteocalcin (OC) measured as bone formation marker of primiparous cows was significantly higher than multiparous cows (P < 0.01) at 21 and 28 days postpartum. The urinary deoxypyridinoline (DPD) as bone resorption marker of primiparous cows tended to be higher (P < 0.10) than multiparous cows at 21 days after parturition and decreased to the same level as that of multiparae toward the peak lactation. These results show that Ca and P mobilization of primiparous cows are more active than multiparous cows.     

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background

Phosphorus (P) supplementation is costly and can result in excess P excretion. This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.

Method

Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield, and assigned randomly to one of the three dietary treatments: 0.37, 0.47, and 0.57% P (DM basis); these P levels represent the NRC recommendations, Chinese recommendations, and the amount of dietary P commonly fed by Chinese dairy farmers, respectively. Average daily feed intake was calculated from monthly data on feed offered and refused. Milk yields of individual cows were recorded weekly, and milk samples were taken for analysis of protein, fat, solids-not-fat, lactose, and somatic cell count. Blood samples were collected on days −6, −3, 0, 3, 6 relative to calving, and then monthly throughout lactation, and analyzed for P and Ca concentrations. Spot samples of feces and urine were collected for 3 consecutive d during weeks 12, 24, and 36, and P concentrations were analyzed. Reproduction and health data were recorded.

Results

Dietary P did not affect dry matter intake or milk yield (P > 0.10). Milk fat content was slightly higher in cows fed 0.37% P than in cows fed 0.47% P (P = 0.05). Serum concentrations of P and Ca did not reflect dietary P content (P > 0.10). Fecal and urinary P both declined linearly (P < 0.05) as dietary P decreased from 0.57 to 0.37%. Fecal P content was 25% less when dietary P was 0.37% compared to 0.57%. Health events and reproductive performance were not associated with dietary P content (P > 0.05).

Conclusions

Lowering dietary P from 0.57 to 0.37% did not negatively affect milk production, but did significantly reduce P excretion into environment.     

Effects of feeding and animal performance on nitrogen, phosphorus and potassium excretion by Holstein cows

Thirty‐four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume.     

Preanalytical factors affecting blood inorganic phosphate concentration in dairy cows

BACKGROUND: Hypophosphatemia is a condition that affects feed intake and milk production in dairy cows, and, to assess it, a precise biological parameter is needed. Plasma inorganic phosphate (Pi) can be used as a potential indicator of bioavailability of feed phosphorus in dairy cows. OBJECTIVE: The purpose of this study was to evaluate the effects of sample type (serum vs. plasma), blood sampling site (jugular vs. coccygeal), and morning feeding on blood Pi concentration in dairy cows. METHODS: Blood samples from 28 clinically healthy multiparous Holstein cows were analyzed for Pi concentration. The animals were sampled twice by coccygeal vessel into Vacutainer tubes both with and without sodium heparin, 3 hours after the morning feeding. In 4 additional cows, the concentration of Pi was measured in blood samples obtained simultaneously by jugular and coccygeal venipuncture into heparinized tubes before the morning feeding and 2, 4, and 6 hours after the feeding. The results were analyzed using parametric statistical tests. RESULTS: Serum and plasma concentrations of Pi were correlated (r(2) = 0.999, P < .0001), but serum Pi concentration was higher than plasma Pi (P < .02). Plasma Pi concentration 2 hours after feeding tended to be higher than that before feeding in jugular samples, but the difference was not significant. There was no significant variation in plasma Pi during the morning postfeeding times, although jugular concentrations were 19% lower than coccygeal (P = .04). CONCLUSION: To increase the precision of plasma Pi measurements as an indicator of bioavailability of feed phosphorus, sample type, sampling time, and site must be taken into account, to correctly interpret plasma Pi concentrations.     

Heritability and genetic correlations between rumination time and production traits in Holstein dairy cows during different lactation phases

So far, rumination has been used as a proxy for monitoring dairy cow health at farm level. However, investigating its genetic aspects as well as its correlation with other important productive traits may turn this management tool into a new informative selection criterion. However, scientific evidences on genetic correlation among rumination time (RT) and milk production and milk composition are still scarce. Therefore, the objective of this study was to estimate the heritability of RT across three lactation phases and its genetic correlation with milk production, milk composition and somatic cell count (SCC). Results of our study showed that heritability for RT was 0.34 and was constant across lactation. The mean genetic correlations between RT and milk production and composition traits were 0.07 (milk production), ?0.07 (protein yield), ?0.31 (fat yield), and ?0.32 (fat/protein ratio). The mean genetic correlation between RT and the SCC was 0.05.     

Effect of nutrient levels during the far‐off period on postpartum productivity in dairy cows

The present study aimed to determine the effects of differing nutrient levels during the far‐off period on postpartum metabolism and milk production in lactating cows. Twenty‐six multiparous cows were assigned to three dietary treatments in the far‐off period: a low‐energy diet (L, n = 9, 80% intake of the total digestible nutrients requirement), a moderate‐energy diet (M, n = 8, 105%) and a high‐energy diet (H, n = 9, 130%). During the close‐up period, all cows were provided with 105% intake. After parturition, all cows were fed a lactation diet. The BCS recovery was slow, and low milk yield was found in the H group. In the L group, BCS recovery was favorable after parturition, and lactation persistence was increased. The L group had low rumen endotoxin activity and a high initial ovulation rate after parturition. These findings indicate that a high‐energy diet during the far‐off period has a deleterious effect on milk production. In contrast, the restricted diet in the far‐off period increased adaptability with respect to peri‐parturition metabolic changes, improved the post‐parturition nutritional state, and increased milk production. Furthermore, it suggests that the nutrient levels in the far‐off period affect rumen endotoxin activity and reproductive function after parturition.     

The effect of high ambient temperature on Ca,P and Mg balance and bone turnover in high‐yielding dairy cows

We investigated the effect of heat stress on Ca, P and Mg balance and bone turnover in lactating cows. In a 2 × 2 crossover design, four multiparous lactating Holstein cows were kept in a chamber and subjected to a constant moderate (18°C) ambient temperature (MT) or high (28°C) ambient temperature (HT). The cows were fed total mixed ration (Ca, 0.7%; P, 0.4%; Mg, 0.2%) ad libitum. The milk yield under HT (35.4 kg/day) tended to be lower (P < 0.10) than that under MT (43.2 kg/day). The concentrations of milk P (P < 0.05) and Mg (P < 0.01) were significantly lower under HT than MT. The Ca, P and Mg intake (P < 0.10); Ca (P < 0.10), P, and Mg (P < 0.05) secretion into milk; and Ca (P < 0.05), P (P < 0.01), and Mg (P < 0.05) absorption in the intestine were lower under HT than MT. The plasma osteocalcin, a marker of bone turnover, was significantly lower (P < 0.05) under HT than MT. Heat stress did not affect plasma C‐telopeptide of collagen type I, a bone resorption marker, and plasma parathyroid hormone concentration.     

Characterization of ruminal dynamics in Holstein dairy cows during the periparturient period

We used four pregnant Holstein cows to delineate ruminal adaptations as cows transitioned from one lactation to the next. Cows were fed typical diets through far-off and close-up dry periods and lactation. We measured ruminal characteristics on day 72 (late lactation), 51 (far-off dry), 23 and 9 (close-up dry) prepartum and on days 6, 20, 34, 48, 62, 76 and 90 postpartum (early lactation). Measurements included: ruminal fill (weight of actual contents), ruminal capacity (volume of rumen when fully filled), digestibilities and ruminal passage rates. Ruminal capacity tended to increase linearly during early lactation but was stable during dry and transition periods. Both total and liquid fill decreased linearly during the dry period, increased across parturition, and increased linearly through early lactation. Dry matter fill decreased as cows were fed the close-up diet at day 23 prepartum then increased near parturition and continued to increase across early lactation. Solid passage rate was greatest when cows were fed the close-up diet, and decreased throughout the transition period. In lactation, solid passage rate responded quadratically with peak at day 48 followed by decreases through day 90 postpartum. Liquid passage increased linearly across the transition period. Total tract organic matter digestibilities increased linearly over the dry period with significant increases prior to or immediately after parturition, then they remained relatively stable over early lactation until they increased at day 90. Fibre digestibilities demonstrated quadratic responses over early lactation, being higher on day 6 and day 90 than at other times. Starch digestibilities decreased linearly across both the dry and transition periods with decreases in lactation until day 62 followed by increases until day 90. High producing lactating dairy cows go through a multitude of ruminal adaptations, in terms of digestion, passage, capacity and fill, as they transition from one lactation to the next.     

Expression of fibroblast growth factor 21 in the liver of dairy cows in the transition period and during lactation

Fibroblast growth factor 21 (FGF21) has been identified as a novel hormonal factor involved in the regulation of metabolic adaptations during energy deprivation. The present study aimed to investigate the expression of the FGF21 gene in the liver of dairy cows during the transition from pregnancy to lactation. Therefore, the relative mRNA abundance of FGF21 in liver biopsy samples of 20 dairy cows in late pregnancy (3 weeks pre‐partum) and early lactation (1, 5, 14 weeks post‐partum) was determined. It was observed that hepatic mRNA abundance of FGF21 at 1 week post‐partum was dramatically increased (110‐fold) compared to 3 weeks pre‐partum (p < 0.001). With progress of lactation, mRNA concentration of FGF21 was declining; nevertheless, mRNA abundance at 5 and 14 weeks post‐partum remained 25‐ and 10‐fold increased compared to 3 weeks pre‐partum (p < 0.001). Using a gene array technique, it was found that many genes involved in fatty acid oxidation, gluconeogenesis and ketogenesis were up‐regulated during early lactation compared to late pregnancy. Moreover, there were positive linear correlations between hepatic mRNA concentration of FGF21 and mRNA concentrations of genes involved in ketogenesis as well as carnitine synthesis and carnitine uptake at various time‐points during lactation, indicating that FGF21 could play a role in ketogenesis and carnitine metabolism in the liver of dairy cows (p < 0.05). In overall, the present study shows that expression of the FGF21 gene is strongly up‐regulated during the transition period. It is assumed that the up‐regulation of FGF21 might play an important role in the adaptation of liver metabolism during early lactation in dairy cows such as in other species.     

Feed intake, lactation performance, blood metabolites and fertility in early lactation dairy cows grazing a timothy pasture

The present study was conducted to investigate feed intake, milk yield, milk composition, blood metabolites and fertility in early lactation dairy cows grazing a timothy pasture. Fourteen multiparous Holstein cows that calved between 20 May and 19 July were used over a 3‐year period. The stocking rate was 3.6–4.3 cow/ha. Concentrates were fed separately at 9.5–11.5 kg/day per cow (dry matter basis) from 1 to 13 weeks postparturition. Herbage intake was estimated using chromium oxide as an indigestible marker. The mean contents of crude protein, total digestible nutrients and neutral detergent fiber of pasture during the 3‐year study period were 22.3%, 71.8% and 51.7%, and those of total diet were 18.9%, 77.3% and 40.3%, respectively. The mean herbage dry matter intake was 13.0 kg/day from 2 to 13 weeks postparturition during the study, total dry matter intake was 23.7 kg/day, the total digestible nutrients sufficiency rate was 105%, milk yield was 39.7 kg/day, and milk fat percentage was 3.30%. The decrease in bodyweight postparturition was slight. Urea nitrogen concentrations in serum were below 18.3 mg/dL. The mean days to first estrus and days open were 36 and 104 days, respectively. These results indicate that energy deficiency, decrease in bodyweight and fertility in early lactation barely occur when high producing dairy cows are fed enough grazing grass and suitable concentrates.     

乳牛产后期生理性免疫状态的研究

为了研究乳牛在产后期的生理性免疫状态，检测了产后期乳牛淋巴细胞及其亚群数量和淋巴细胞增殖活化功能及其变化。结果发现，乳牛淋巴细胞及其亚群数量和淋巴细胞增殖活化功能在分娩后第1d最低，然后表现出缓慢上升的总体趋势。CD3细胞数在产后第15d低于产后第1d，到产后第30d时达到最高值；CD4细胞数一直多于CD8细胞数；CD21细胞数在产后第15d时达到最高值，以后缓慢下降；淋巴细胞的增殖活化能力在产后第30d最高，未观察到淋巴细胞有明显的凋亡和增生现象。结果表明，乳牛免疫状态在产后第1d最低，以后逐渐升高，第15d时细胞免疫最低而体液免疫最高，第30d时细胞免疫最强。     

Kinematic gait analysis and lactation performance in dairy cows fed a diet supplemented with zinc,manganese, copper and cobalt

This study investigated how supplementation of the diet of dairy cows with trace minerals (zinc, manganese, copper and cobalt) affected kinematic gait parameters and lactation performance. Eight Holstein cows were divided into two groups, with each group receiving a different dietary treatment (control diet, or control diet supplemented with trace minerals) in a two‐period crossover design. Kinematic gait parameters were calculated by using image analysis software. Compared to cows fed the control diet, cows that received the trace mineral‐supplemented diet exhibited significantly increased walking and stepping rates, and had a shorter stance duration. Feed intake and milk production increased in cows fed the trace mineral‐supplemented diet compared with control groups. The plasma manganese concentration was not different in control and experimental cows. In contrast, cobalt was only detected in the plasma of cows fed the supplemented diet. These results provide the first evidence that trace mineral supplementation of the diet of dairy cows affects locomotion, and that the associated gait changes can be detected by using kinematic gait analysis. Moreover, trace mineral supplementation improved milk production and only minimally altered blood and physiological parameters in dairy cows.     

Follicular cysts in dairy cows

Follicular cysts are the most critical reproductive disorder in dairy cows and disturb the normal ovarian cycle, resulting in a prolonged interval from calving to conception. Therefore, this condition causes significant economic losses to the dairy industry. Two direct causal factors for cysts are suggested in this review; ovulation disorder and the delay of regression. Ovulation disorder has been accepted to be a main etiology of cystic follicle. This seems to be caused by the deficiency of positive feedback of estrogen to the hypothalamus, leading to the lack of luteinizing hormone surge. On the other hand, if a large anovulatory follicle is regressed immediately after the failure of ovulation, its follicle does not continue to grow, resulting in no cystic follicle being formed. Therefore, it is proposed that another cause of a cystic follicle is the delay (or absence) of the degeneration system of the follicle. This review will introduce these two causes separately, referring to recent advances in understanding the follicular cyst in dairy cows.     

我国奶牛磷需要量

饲喂奶牛应该满足而不是超过其营养需要量。给奶牛饲喂过量的磷会降低磷的利用率,增加磷向外围环境的排泄,从而造成严重的环境污染问题。降低奶牛日粮中磷的含量将减少磷的排泄和土壤中磷的蓄积,同时降低了生产成本,节约了不可再生的磷矿资源。     

Effect of dietary net energy concentration on dry matter intake and energy partition in cows in mid‐lactation under heat stress

This study aimed to determine the net energy requirement of Holstein cows in mid‐lactation under heat stress. Twenty‐five multiparous Holstein cows were randomly allocated to five groups corresponding to five isonitrogenous total mixed rations, with net energy for lactation (NE_L) content of 6.15 (NE‐6.15), 6.36 (NE‐6.36), 6.64 (NE‐6.64), 6.95 (NE‐6.95), 7.36 (NE‐7.36) MJ/kg of dry matter (DM), respectively. Throughout the experimental period the average temperature humidity index at 07.00, 14.00 and 22.00 hours was 72.1, 88.7, and 77.6, respectively. DM intake decreased significantly with the elevated dietary NE_L concentration. Fat corrected milk increased quadratically, and milk fat content and milk energy (MJ/kg) reached the greatest in the NE‐6.95 group with increasing dietary NE_L content. Strong correlations were found between dietary NE_L content and: (i) DM intake; (ii) NE_L intake; (iii) milk energy (E_l); (iv) E_l/metabolizable energy intake (MEI); (v) E_l/NE_L intake, as well as between NE_L intake and fat corrected milk yield (FCM). The suitable net energy required for dairy cows producing 1 kg FCM ranged from 5.01 to 5.03 MJ, was concluded from the above‐stated regressions. Correlation between heat production (HP) and MEI could be expressed as: Log (HP) = ?0.4304 + 0.2963*MEI (n = 15, R² = 0.99, Root Mean Square Error (RMSE) = 0.18). Fasting HP was 0.3712 MJ/kg^0.75 when extrapolating MEI to zero.     

仙人掌果实对奶牛泌乳性能、氮利用及采食行为的影响

本研究评估了仙人掌果实与不同粗饲料结合对荷斯坦奶牛采食量、营养物质消化率、氮平衡、摄食行为和泌乳性能的影响。试验选择泌乳期为(72±11)d的8头奶牛,采用4×4拉丁试验设计,共4种试验日粮:T1组为75%青贮高粱组,T2组为75%象草组,T3组为37.5%青贮高粱+37.5%仙人掌果实,T4组为37.5%象草+37.5%仙人掌果实。结果:青贮高粱组干物质摄入量最高(P<0.05)。不同日粮组干物质、粗蛋白质、粗脂肪、非纤维碳水化合物和总可消化养分摄入量存在显著差异(P<0.05)。仙人掌果实组较青贮高粱和象草组日饮水量降低44.52%(P<0.05)。与象草组、象草+仙人掌果实组相比,青贮高粱组、青贮高粱+仙人掌果实组氮平衡降低59.71%和27.49%(P<0.05)。结论:奶牛日粮中以仙人掌果实与青贮高粱或象草的组合并没有改变荷斯坦奶牛的产奶量,但降低了营养物质和水分摄入量,同时提高了养分消化率。