Association between prepartum body condition score and prepartum and postpartum dry matter intake and energy balance in multiparous Holstein cows.

The objectives of this retrospective observational study were to investigate the association between BCS at 21 d before calving with prepartum and postpartum DMI, energy balance (EB), and milk yield. Data from 427 multigravid cows from 11 different experiments conducted at the University of Florida (Gainesville, FL) were used. Cows were classified according to their BCS at 21 d before calving as fat (BCS ≥ 4.00; n = 83), moderate (BCS = 3.25-3.75; n = 287), and thin (BCS ≤ 3.00; n = 57). Daily DMI from -21 to -1 and from +1 to +28 DIM was individually recorded. Energy balance was calculated as the difference between net energy for lactation consumed and required. Dry matter intake in fat cows was lower than that in moderate and thin cows both prepartum (fat = 9.97 ± 0.21, moderate = 11.15 ± 0.14, and thin = 11.92 ± 0.22 kg/d) and postpartum (fat = 14.35 ± 0.49, moderate = 15.47 ± 0.38, and thin = 16.09 ± 0.47 kg/d). Dry matter intake was also lower for moderate cows compared with thin cows prepartum, but not postpartum. Energy balance in fat cows was lower than in moderate and thin cows both prepartum (fat = -4.16 ± 0.61, moderate = -1.20 ± 0.56, and thin = 0.88 ± 0.62 Mcal/d) and postpartum (fat = -12.77 ± 0.50, moderate = -10.13 ± 0.29, and thin = -6.14 ± 0.51 Mcal/d). Energy balance was also lower for moderate cows compared with thin cows both prepartum and postpartum. There was a quadratic association between BCS at 21 d before calving and milk yield. Increasing BCS from 2.5 to 3.5 was associated with an increase in daily milk yield of 6.0 kg and 28 d cumulative milk of 147 kg. Increasing BCS from 3.5 to 4.5 was associated with a decrease in daily milk yield of 4.4 kg and 28 d cumulative milk of 116 kg. In summary, a moderate BCS at 21 d before calving was associated with intermediate DMI and EB pre- and postpartum but greater milk yield compared with thinner and fatter cows. Our findings indicate that a moderate BCS is ideal for ensuring a successful lactation.

Association of dry matter intake and energy balance prepartum and postpartum with health disorders postpartum: Part II. Ketosis and clinical mastitis.

The main objective of this study was to determine the association of dry matter intake as percentage of body weight (DMI%BW) and energy balance (EB) prepartum (-21 d relative to parturition) and postpartum (28 d) with ketosis (n = 189) and clinical mastitis (n = 79). For this, DMI%BW and EB were the independent variables and ketosis and clinical mastitis were the dependent variables. A secondary objective was to evaluate prepartum DMI%BW and EB as predictors of ketosis and clinical mastitis. For this, ketosis and clinical mastitis were the independent variables and DMI%BW and EB were the dependent variables. Data from 476 cows from 9 experiments were compiled. Clinical mastitis was diagnosed if milk from 1 or more quarters was abnormal in color, viscosity, or consistency, with or without accompanying heat, pain, redness, or swelling of the quarter or generalized illness, during the first 28 d postpartum. Ketosis was defined as the presence of acetoacetate in urine that resulted in any color change [5 mg/dL (trace) or higher] in the urine test strip (Ketostix, Bayer, Leverkusen, Germany). Cows that developed ketosis had lesser DMI%BW and lesser EB on d -5, -3, -2, and -1 than cows without ketosis. Each 0.1-percentage point decrease in the average DMI%BW and each 1-Mcal decrease in the average of EB in the last 3 d prepartum increased the odds of having ketosis by 8 and 5%, respectively. Cut-offs for DMI%BW and EB during the last 3 d prepartum to predict ketosis were established and were ≤1.5%/d and ≤1.1 Mcal/d, respectively. Cows that developed ketosis had lesser postpartum DMI%BW and EB and greater energy-corrected milk (ECM) than cows without ketosis. Cows that developed clinical mastitis had lesser DMI%BW but similar prepartum EB compared with cows without clinical mastitis. Each 0.1-percentage point decrease in the average DMI%BW and each 1-Mcal decrease in the average EB in the last 3 d prepartum increased the odds of having clinical mastitis by 10 and 8%, respectively. The average DMI%BW and EB during the last 3 d prepartum produced significant cut-offs to predict clinical mastitis postpartum, which were ≤1.2%/d and ≤1.0 Mcal/d, respectively. Cows that developed clinical mastitis had lesser postpartum DMI%BW from d 3 to 15 and on d 17; greater EB on d 18, from d 21 to 23, and on d 26; and lesser ECM. The main limitation in this study is that the time-order of disease relative to DMI%BW and ECM is inconsistent such that postpartum outcomes were measured before and after disease, which was diagnosed at variable intervals after calving. In summary, measures of prepartum DMI were associated with and were predictors of ketosis and clinical mastitis postpartum, although the effect sizes were small.

Association of dry matter intake and energy balance prepartum and postpartum with health disorders postpartum: Part I. Calving disorders and metritis.

The main objective of this study was to determine the association of dry matter intake as percentage of body weight (DMI%BW) and energy balance (EB) prepartum (-21 d relative to parturition) and postpartum (28 d) with calving disorders (CDZ; dystocia, twins, and stillbirths; n = 101) and metritis (n = 114). For this, DMI%BW and EB were the independent variables and CDZ and metritis were the dependent variables. A secondary objective was to evaluate prepartum DMI%BW and EB as predictors of CDZ and metritis. For this, CDZ and metritis were the independent variables and DMI%BW and EB were the dependent variables. Data from 476 cows from 9 experiments were compiled. Cows that developed CDZ had lesser postpartum DMI%BW from d 3 to 12 and lesser energy-corrected milk (ECM) than cows that did not develop CDZ. Dry matter intake as percentage of BW and EB prepartum did not affect the odds of CDZ. Cows with metritis had lesser prepartum DMI%BW and EB. Each 0.1-percentage point decrease in the average DMI%BW and each 1-Mcal decrease in the average EB in the last 3 d prepartum increased the odds of having metritis by 8%. The average DMI%BW and EB during the last 3 d prepartum produced significant cut-offs to predict metritis postpartum, which were ≤1.6%/d and ≤2.5 Mcal/d, respectively. Cows that developed metritis had lesser overall postpartum DMI%BW and ECM and lesser EB from d 2 to 5 and from d 7 to 11 than cows that did not develop metritis. The main limitation in this study is that the time-order of disease relative to DMI%BW and ECM is inconsistent such that postpartum outcomes were measured before and after disease, which was diagnosed at variable intervals after calving. In summary, prepartum DMI%BW and EB were associated with and were predictors of metritis although the effect sizes were small for metritis, and calving disorders and metritis were associated with decreased DMI%BW and ECM postpartum.

Short communication: Effect of heat stress during the dry period on gene expression in mammary tissue and peripheral blood mononuclear cells.

Heat stress (HT) during the dry period compromises mammary gland development, decreases future milk production, and impairs the immune status of dairy cows. Our objective was to evaluate the effect of cooling HT cows during the dry period on gene expression of the mammary gland and peripheral blood mononuclear cells (PBMC). Cows were dried off 46 d before their expected calving and assigned to 2 treatments, HT or cooling (CL). Cows in the CL group were cooled with sprinklers and fans whereas HT cows were not. After parturition, all cows were housed in a freestall barn with cooling. The PBMC were isolated at dry-off and at -20, 2, and 20 d relative to calving from a subset of cows (HT, n=9; CL, n=10), and mammary biopsies were taken at the same intervals (HT, n=7; CL, n=6) for RNA extraction. Gene expression was assessed using a custom multiplex gene expression assay based on traditional reverse transcription-PCR. Genes involved in prolactin (PRL) signaling [PRL receptor long form, PRL receptor short form, suppressor of cytokine signaling (SOCS)2, SOCS3, IGF2, IGF binding protein 5, and cyclin D1], fatty acid metabolism (acetyl-CoA carboxylase α (ACACA) and lipoprotein lipase (LPL)], and IGF1 were evaluated in mammary tissue, and genes related to fatty acid metabolism [ACACA, fatty acid synthase (FASN), and LPL], cytokine production [IL6, IL8, and tumor necrosis factor (TNF)], and IGF1 were evaluated in PBMC. No differences were observed in PRL signaling or fatty acid metabolism gene expression in the mammary gland. In PBMC, HT cows had greater mRNA expression of IGF1 and TNF during the transition period relative to CL and upregulated IL8 and downregulated FASN mRNA expression at 2 d relative to calving. We conclude that cooling HT cows during the dry period alters expression of genes involved in cytokine production and lipid metabolism in PBMC.

Effect of heat stress during the dry period on mammary gland development.

Heat stress during the dry period negatively affects hepatic metabolism and cellular immune function during the transition period, and milk production in the subsequent lactation. However, the cellular mechanisms involved in the depressed mammary gland function remain unknown. The objective of the present study was to determine the effect of heat stress during the dry period on various indices of mammary gland development of multiparous cows. Cows were dried off approximately 46 d before expected calving and randomly assigned to 2 treatments, heat stress (HT, n=15) or cooling (CL, n=14), based on mature equivalent milk production. Cows in the CL treatment were provided with sprinklers and fans that came on when ambient temperatures reached 21.1°C, whereas HT cows were housed in the same barn without fans and sprinklers. After parturition, all cows were housed in a freestall barn with cooling. Rectal temperatures were measured twice daily (0730 and 1430 h) and respiration rates recorded at 1500 h on a Monday-Wednesday-Friday schedule from dry off to calving. Milk yield and composition were recorded daily up to 280 d in milk. Daily dry matter intake was measured from dry off to 42 d relative to calving. Mammary biopsies were collected at dry off, -20, 2, and 20 d relative to calving from a subset of cows (HT, n=7; CL, n=7). Labeling with Ki67 antigen and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling were used to evaluate mammary cell proliferation and apoptosis, respectively. The average temperature-humidity index during the dry period was 76.6 and not different between treatments. Heat-stressed cows had higher rectal temperatures in the morning (38.8 vs. 38.6°C) and afternoon (39.4 vs. 39.0°C), greater respiration rates (78.4 vs. 45.6 breath/min), and decreased dry matter intake (8.9 vs. 10.6 kg/d) when dry compared with CL cows. Relative to HT cows, CL cows had greater milk production (28.9 vs. 33.9 kg/d), lower milk protein concentration (3.01 vs. 2.87%), and tended to have lower somatic cell score (3.35 vs. 2.94) through 280 d in milk. Heat stress during the dry period decreased mammary cell proliferation rate (1.0 vs. 3.3%) at -20 d relative to calving compared with CL cows. Mammary cell apoptosis was not affected by prepartum heat stress. We conclude that heat stress during the dry period compromises mammary gland development before parturition, which decreases milk yield in the next lactation.

Heat stress abatement during the dry period influences metabolic gene expression and improves immune status in the transition period of dairy cows.

Heat stress (HT) and photoperiod affect milk production and immune status of dairy cows. The objective was to evaluate the effects of HT abatement prepartum under controlled photoperiod on hepatic metabolic gene expression and cellular immune function of periparturient Holstein cows (n=21). Cows were dried off 46 d before expected calving date and assigned to treatments by mature equivalent milk production. The treatments were 1) HT and 2) cooling (CL), both imposed during a photoperiod of 14L:10D. Rectal temperature was measured twice daily, whereas respiration rate was measured 3 times/wk at 1500 h during the entire dry period. After calving, cows were housed in a freestall barn with cooling, and milk yield was recorded daily up to 140 d in milk. Liver samples were taken at dry off, -20, 2, and 20 d relative to calving by biopsy. Under a similar schedule, neutrophil function was determined in blood of cows on HT (n=12) and CL (n=9). Blood samples were taken on -46, -32, -18, 0, 14, 28, and 42 d relative to calving for measurement of metabolites and were collected twice daily from -7 to 2 d relative to calving for prolactin (PRL) analysis. The HT cows had greater concentrations of PRL at 0 d relative to calving (150 vs. 93; SEM=11 ng/mL) and had higher afternoon rectal temperatures (39.4 vs. 39.0; SEM=0.04°C) and elevated respiration rates (78 vs. 56; SEM=2 breaths/min) during the prepartum period compared with CL cows. Relative to HT cows, CL cows had greater hepatic expression of PRL-R, SOCS-3, and CAV-1 mRNA. Neutrophil oxidative burst was greater in CL cows relative to HT cows at 2 d (61 vs. 42; SEM=6%) and at 20 d (62 vs. 49; SEM=5%) relative to calving, and phagocytosis was greater in CL cows at 20 d (47 vs. 33; SEM=4%) relative to calving compared with HT cows. Humoral response, as measured by IgG secretion against ovalbumin challenge, was greater for CL cows at -32 d (0.44 vs. 0.33; SEM=0.05 OD) and -21 d (0.60 vs. 0.50±0.04 OD) relative to calving compared with HT cows. These results suggest that HT abatement during the dry period improved innate and acquired immune status as measured by neutrophil function and immunoglobulin secretion against ovalbumin challenge, and altered hepatic gene expression related to PRL signaling in the periparturient period or subsequent lactation.

Heat-stress abatement during the dry period: does cooling improve transition into lactation?

Environmental factors, especially temperature and light exposure, influence the health and productivity of dairy cows during lactation, possibly via similar physiological mechanisms. For example, heat stress is a critical component of decreased milk yield during summer. However, less is known about the effect of heat stress during the dry period. The objective of this study was to evaluate the effects of heat stress prepartum under a controlled photoperiod on lactation performance and hepatic metabolic gene expression of periparturient multiparous Holstein cows (n = 16). Cows were dried off approximately 46 d before expected calving date and assigned to treatment randomly after blocking by mature equivalent milk production and parity. Treatments consisted of either heat stress (HT) or cooling (CL) with fans and sprinklers, both under a photoperiod of 14L:10D. Rectal temperature was measured twice daily during the dry period. After calving, cows were housed in a freestall barn with cooling devices, and milk yield was recorded daily up to 210 d in milk. Blood samples were taken from dry off until +42 d relative to calving for metabolites and from -2 until +2 d relative to calving for hormone analysis. Daily dry matter intake was measured from -35 to +42 d relative to calving. Liver biopsies were collected at dry off, -20, +2, and +20 d relative to calving for cows on HT (n = 5) and CL (n = 4) to measure mRNA expression of suppressors of cytokine signaling-2 (SOCS-2), insulin-like growth factor binding protein-5 (IGFBP-5), a key transcription factor in lipid biosynthesis (SREBP-1c), and enzymes of lipid metabolism (FASN, ACACA, and ACADVL) by real-time quantitative PCR. Heat stress increased rectal temperatures (39.2 vs. 38.8 degrees C), plasma prolactin concentrations at -1 (171 vs. 79 ng/mL) and 0 d (210 vs. 115 ng/mL) relative to calving, and decreased dry matter intake at 0 and +14 d relative to calving and 3.5% fat-corrected milk postpartum (26.1 vs. 35.4 kg/d) compared with CL cows. Relative to CL cows, hepatic mRNA expression of SOCS-2 and IGFBP-5 was downregulated in HT cows. Expression of ACADVL was upregulated in CL cows at d +2 but downregulated at d +20 relative to HT cows. Concentrations of C16:0 and cis C18:1 were greater in the milk and liver of CL cows compared with HT cows, which reflects greater lipid mobilization. These results suggest that heat-stress abatement in the dry period improves subsequent lactation, possibly via suppression of plasma prolactin surge around calving, SOCS-2 expression, and regulation of hepatic lipid metabolism.

Effects of dietary unsaturated fatty acids on oocyte quality and follicular development in lactating dairy cows in summer.

Dietary sources of fatty acids were evaluated for their influence on oocyte quality and follicular development using 54 lactating cows in summer. Fat supplements were 1) sunflower oil (80% cis 18:1), 2) Ca salt of transoctadecenoic acids (57% trans 18:1), 3) Ca salt of vegetable oils (30% 18:2), and 4) linseed oil (56% 18:3 and 16% 18:2). Fats were fed at 1.35% of dietary dry matter beginning at 5 wk prior to expected calving date and at 1.5% (oils) and 1.75% (Ca salts) of dietary dry matter for 15 wk after parturition. Four days following a programmed induced ovulation, 5 transvaginal oocyte aspirations were performed 3 or 4 d apart. Three days after the last aspiration, PGF2alpha was injected, followed 3 d later by a GnRH injection and a timed artificial insemination (d 0) 16 to 20 h later. For the first 4 aspirations, oocytes grading 1 or 2 were used for in vitro embryo production. Total cell number and the proportion of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive blastomeres were analyzed at d 8. At the fifth aspiration, the occurrence of metaphase II, group II caspase activity, and TUNEL labeling were determined after oocyte maturation. A total of 1,011 oocytes were collected. The proportion of oocytes with high caspase activity was greater for grade 3 compared with grades 1 and 2 (37.5 vs. 1.54 and 1.61%). Feeding polyunsaturated fatty acids, as compared with monosaturated fatty acids, failed to affect oocyte quality, as demonstrated by subsequent embryo development. Cows fed 18:2- or 18:3-enriched diets had a larger preovulatory follicle at insemination and subsequent volume of the corpus luteum compared with those fed cis 18:1 or trans 18:1 diets (16.8, 16.2 vs. 15.0, 14.9 +/- 0.7 mm; 7,323, 8,208 vs. 6,033, 5,495 +/- 644 mm3, respectively). The previously documented benefits of polyunsaturated fatty acids on reproductive performance appear to reflect actions at alternative biological windows in lactating dairy cows.

Heat stress abatement during the dry period influences prolactin signaling in lymphocytes.

Heat stress perturbs prolactin (PRL) release and affects dairy cow lactational performance and immune cell function. We hypothesized that greater PRL concentration in plasma of heat-stressed cows relative to cooled cows would decrease expression of prolactin receptor (PRL-R) mRNA and increase mRNA expression of suppressors of cytokine signaling (SOCS) in lymphocytes, altering their cytokine production. To test this hypothesis, multiparous Holstein cows were dried off 46 d before their expected calving date and assigned randomly to heat stress (HT; n=9) or cooling (CL; n=7) during the entire dry period. A second study was conducted the following year with an additional 21 cows (12 HT; 9 CL). Lymphocytes were isolated from cows at -46, -20, +2, and +20 d relative to expected calving date and mRNA expression of PRL-R, SOCS-1, SOCS-2, SOCS-3, cytokine-inducible SH2-containing protein (CIS), and heat shock protein 70 KDa A5 (HSPA5), and housekeeping genes hydroxymethylbilane synthase (HMBS), ATP synthase, H+ transporting mitochondrial F1 complex, beta subunit (ATP5B), and ribosomal protein S9 (RPS9) was analyzed by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). Cows exposed to HT had greater PRL concentration in plasma compared with CL cows. Measurement of lymphocyte proliferation indicated that lymphocytes of CL cows proliferated more than those from HT cows and exressed more PRL-R mRNA and less SOCS-1 and SOCS-3 mRNA relative to HT cows. Further, lymphocytes from CL cows produced more tumor necrosis factor-alpha (TNF-alpha) than those from HT cows. These results suggest that changes in PRL-signaling pathway genes during heat stress are associated with differential cytokine secretion by lymphocytes and may regulate lymphocyte proliferation in dairy cows.