W.R. Butler

Nutritional interactions with reproductive performance in dairy cattle

Increased capability for milk production has been associated with a decline in fertility of lactating cows. Nutritional requirements increase rapidly with milk production after calving and result in negative energy balance (NEBAL). NEBAL delays the time of first ovulation through inhibition of LH pulse frequency and low levels of blood glucose, insulin and insulin-like growth factor-I (IGF-I) that collectively restrain estrogen production by dominant follicles. Up-regulation of LH pulses and peripheral IGF-I in association with the NEBAL nadir facilitates ovulation. NEBAL reduces serum progesterone concentrations and fertility. Diets high in crude protein support high milk yield, but are also associated with lower reproductive performance. High protein can result in elevated plasma urea concentrations that affect the uterine environment and fertility. Nutritional interactions resulting in poor fertility of high producing dairy cows include the antecedent effects of NEBAL and effects of high dietary protein.

Energy balance relationships with follicular development, ovulation and fertility in postpartum dairy cows

Abstract Increased capacity for milk production in dairy cows has been associated with a decline in fertility. Following parturition, nutritional requirements increase rapidly with milk production and the resulting negative energy balance (NEBAL) extends for 10–12 weeks. NEBAL is strongly associated with the length of the postpartum anovulatory period through attenuation of LH pulse frequency and low levels of blood glucose, insulin and IGF-I that collectively limit oestrogen production by dominant follicles. Plasma concentrations of IGF-I and IGFBP-3 are higher in cows with an ovulatory vs. nonovulatory first dominant follicle. Evidence has accumulated that links the metabolic demands of high milk production and associated NEBAL with diminished quality of oocytes and capability for embryo development. Also NEBAL and body condition score (BCS) loss are related to reduced serum progesterone concentrations during the breeding period and to lower pregnancy rates. Overall, NEBAL is related to lower fertility in dairy cows both through effects exerted early in lactation and later during the breeding period.

Energy balance and pulsatile LH secretion in early postpartum dairy cattle

The relationships between energy balance (EB), pulsatile LH secretion and circulating levels of insulin and various energy metabolites were assessed in ten lactating Holstein cows. Cows were blood sampled every 12 min via indwelling jugular catheters for 8 hr twice weekly beginning in the first week postpartum (PP) through first ovulation (1stOV). Days to negative EB nadir and days to 1stOV were highly correlated (P less than .02). LH pulse frequency (P less than .01), LH baseline (P less than .05) and mean LH (P less than .1) increased, while LH pulse amplitude tended to decrease when comparing the frequent sampling series immediately before and after the negative EB nadir. Plasma levels of non-esterified fatty acids (NEFA, r = -.40, P less than .01), insulin (r = .38, P less than .01), glucose (r = .31, P less than .01) and beta-hydroxybutyrate (r = .19, P less than .06) were correlated with EB. For within animal comparisons, NEFA was significantly correlated (r = -.44 to -.89, P less than .05) with EB in 8 of 10 cows, but no other correlations were significant. Additionally, none of the metabolites nor insulin were significant in multiple regression models for 1stOV. Therefore, it appears that pulsatile LH secretion is suppressed until the negative EB nadir is reached, at which time LH pulse frequency increases stimulating 1stOV. Since NEFA and EB are directly related, NEFA may serve as a peripheral signal of EB to the central nervous system.

Effect of prostaglandin F2α on subclinical endometritis and fertility in dairy cows

The objectives were to determine the effects of PGF(2alpha) treatment on the prevalence of subclinical endometritis (SCE) and fertility of dairy cows. A total of 406 Holstein cows (167 primiparous and 239 multiparous) from 5 herds were used. Uterine lavage for diagnosis of SCE, PGF(2alpha) treatment, evaluation of body condition scores (BCS), and collection of blood samples for estrous cyclicity determination were performed at 21, 35, and 49 d in milk (DIM). Polymorphonuclear cells (PMN) were quantified and thresholds for diagnosing SCE were selected by receiver operating characteristics analysis. Cows classified as having SCE at 35 DIM (>or=6.5% PMN) and 49 DIM (>or=4.0% PMN) had increased time to pregnancy; however, cows classified as having SCE at 21 DIM (>or=8.5% PMN) did not. Median days to pregnancy were delayed by 30 (151 vs. 121 d) and 40 (169 vs. 129) d for cows classified as having SCE at 35 and 49 DIM, respectively. Treatment with PGF(2alpha) did not affect the prevalence of SCE either at 35 (37.9 vs. 38.4%) or at 49 DIM (34.0 vs. 40.4%). Treatment with PGF(2alpha) did not affect time to first insemination (AI; median 76 DIM for cows treated with PGF(2alpha); 79 DIM for control. Nonetheless, PGF(2alpha) treatment increased pregnancy to first AI in all the cows (35.5 vs. 24.1%) and hazard ratio (HR) of pregnancy in cows with BCS <or=2.5 when all of the cows were evaluated (HR = 1.5; 95% confidence interval; CI = 1.1 to 2.0) and when only cows without SCE were evaluated (HR = 1.8; 95% CI = 1.2 to 2.7). Treatment with PGF(2alpha) did not affect the hazard of pregnancy in cows with SCE at 49 DIM (HR = 0.9; 95% CI = 0.6 to 1.3). In these farms, treatment with PGF(2alpha) did not affect SCE or time to first insemination, but did increase first-service pregnancy per AI and decreased time to pregnancy in cows with low BCS.

Effect of Early Postpartum Ovulation on Fertility in Dairy Cows

Our objectives were to determine the effects of early ovulation on fertility and uterine health of dairy cows. Four hundred and forty-five Holstein cows (185 primiparous and 260 multiparous) from five herds were used. Blood samples were collected at 21, 35 and 49 days in milk (DIM) and cows were considered to be cyclic at 21 DIM (Cyc21) if serum progesterone (P4) concentration was above 1 ng/ml, cyclic by 49 DIM (Cyc49) if P4 concentration was above 1 ng/ml at 35 or 49 DIM, or not cyclic (NotCyc) if P4 concentration was below 1 ng/ml at all sample times. Endometrial cytology for diagnosis of subclinical endometritis was examined at 49 DIM in a subset of 414 cows. Cows in the group Cyc21 had increased hazard of insemination, for the first service, compared with cows in Cyc49 [hazard ratio (HR) = 1.40; 95% CI = 1.10-1.79; p = 0.006] and NotCyc (HR = 2.07; 95% CI = 1.52-2.82; p < 0.001). Cows in the Cyc49 group also had increased hazard of insemination compared with cows in the NotCyc group (HR = 1.47; 95% CI = 1.13-1.93; p = 0.005). Median days to insemination were, respectively, 71, 76 and 96 for cows in Cyc21, Cyc49 and NotCyc groups. Cows in Cyc21 had greater first service pregnancy per AI than Cyc49 [38.6 vs 28.1%; adjusted odds ratio (AOR) = 1.67; 95% CI = 1.01-2.75; p = 0.04] and NotCyc (38.6 vs 23.6%; AOR = 2.08; 95% CI = 1.08-4.00; p = 0.03). Pregnancy per AI was similar in Cyc49 and NotCyc cows (28.1 vs 23.6%; AOR = 1.25; 95% CI = 0.70-2.24; p = 0.45). Cows in Cyc21 had increased hazard of pregnancy up to 300 DIM compared with Cyc49 (HR = 1.52; 95% CI = 1.17-1.96; p = 0.002) and NotCyc (HR = 1.98; 95% CI = 1.41-2.78; p < 0.001). Cows in Cyc49 tended to have increased hazard of pregnancy compared with NotCyc (HR = 1.31; 95% CI = 0.96-1.77; p = 0.09). Median days to pregnancy were, respectively, 103, 147 and 173 for cows in Cyc21, Cyc49 and NotCyc groups. Cows in the Cyc21 group had decreased prevalence of subclinical endometritis compared with cows in the NotCyc group (29.9 vs 43.7%; AORu2003= 0.53; 95% CI = 0.29-0.97; p = 0.04); however, the prevalence did not differ from the Cyc49 group (29.9 vs 39.1%; AOR = 0.68; 95% CI = 0.41-1.14; p = 0.15). Cyc49 cows had similar prevalence of subclinical endometritis compared with NotCyc cows (AOR = 0.77; 95% CI = 0.46-1.29; p = 0.32). Early postpartum ovulation was associated with improved uterine health and fertility.

Acute and chronic hormone and metabolite changes in lambs fed the beta-agonist, cimaterol

The objective of this study was to determine if acute and chronic changes in circulating metabolic hormone and metabolite concentrations are associated with beta-agonist-induced nutrient repartitioning in young growing lambs. Two groups of 12 Dorset and Dorset-Finn cross ram lambs weighing 36 or 33 kg live weight were assigned to 3- or 6-week treatment intervals, respectively, to achieve similar slaughter weights. Six lambs within each treatment interval were fed ad libitum a complete mixed high-concentrate diet containing either 0 or 10 ppm cimaterol. During the first 12 hr of cimaterol administration plasma somatotropin (ST), thyroxine (T4), and triiodothyronine (T3) concentrations were not altered by treatment, but plasma insulin, glucose, non-esterified fatty acids (NEFA) and glycerol concentrations were elevated 2 hr after ingestion. These acute responses suggest direct stimulation of glycogenolysis and lipolysis by cimaterol, which is characteristic of beta-adrenergic alteration of carbohydrate and lipid metabolism. Chronic administration of cimaterol significantly decreased insulin concentrations by 36% and 52% at 3 and 6 weeks, respectively, while glucose concentrations remained unchanged. Serum IGF-I concentrations were not significantly altered by cimaterol. T4 levels were reduced 22.1% after 3 weeks of cimaterol treatment. Although plasma NEFA concentrations were chronically elevated 56% to 65% in lambs fed cimaterol, plasma glycerol concentrations remained at baseline levels. The relative changes in plasma NEFA and glycerol concentrations are consistent with a decreased rate of lipogenesis, rather than an increase in lipolysis.

Short communication: acute phase proteins in Holstein cows diagnosed with uterine infection.

The aim of this work was to monitor the pattern of serum acute phase proteins [paraoxonase (PON), haptoglobin (Hp) and albumin] during the peripartum period of normal healthy cows (n=16) compared to that in cows diagnosed with uterine infection (n=15). Albumin concentrations were lower at 21 days before expected calving in cows subsequently diagnosed with uterine infection and predicted the occurrence of uterine infection with an accuracy of 79.3%. Cows diagnosed with uterine infection had a postpartum reduction in serum PON activity and the concentration of Hp increased at 7 DIM for multiparous uterine infected cows. In conclusion, cows diagnosed with uterine infection had reduced serum albumin concentration 21 days before calving, lower PON activity at 7 days after calving, and increased Hp in multiparous cows at 7 DIM compared to healthy cows.

Temporal pattern of skeletal muscle changes in lambs fed cimaterol

The objectives of this study were to compare the efficacy of 3-week vs 6-week dietary administration of the beta-adrenergic agonist cimaterol on skeletal muscle growth, and to measure the changes in muscle nucleic acid and protein concentration and content to provide evidence regarding the mechanism(s) by which cimaterol stimulates muscle hypertrophy in growing ruminants. Two groups of 12 Dorset or Dorset-Finn cross ram lambs weighing 36 kg or 33 kg were assigned to treatment intervals of 3 or 6 weeks, respectively. Lambs within each weight group were randomly assigned to receive 0 or 10 ppm cimaterol in a complete mixed diet fed ad libitum. Initial live weights and treatment periods were chosen to achieve similar slaughter weights. Cimaterol increased the mass of three hind leg muscles 30% and 25% on average (both P less than .001) with 3- and 6-week administration, respectively, resulting in identical average muscle weights of treated lambs at both treatment intervals. The mean mass of these 3 muscles, expressed as a percentage of body weight, was increased 18.6% (P less than .001) at both treatment intervals. RNA concentration and content of the semitendinosus muscle were increased 24.8% (P less than .01) and 84.6% (P less than .001), respectively, after 3 weeks of treatment, but neither was significantly different from controls after 6 weeks. DNA concentration in the muscle was reduced 42% (P less than .05) with 3-week cimaterol administration, and was 25% less than controls (P greater than .05) in lambs fed cimaterol for 6 weeks. Total DNA content of the semitendinosus was unchanged at either treatment interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Paraoxonase (PON) 1, 2 and 3 Expression in Granulosa Cells and PON1 Activity in Follicular Fluid of Dairy Cows

Normal metabolic activity in ovarian follicles may result in oxidative stress and damage to oocytes. The aim of this study was to evaluate expression of the natural anti-oxidants paraoxonase (PON) 1, 2 and 3 in granulosa cells and PON1 activity in follicular fluid (FF) and plasma of dairy cows. For the first experiment, ovaries were collected from cows at slaughter, after which follicles were dissected and classified as oestrogen active (EAF) or atretic (ATF). Expression of PON1, PON2 and PON3 mRNA was evaluated in granulosa cells, and activity of PON1 was measured in FF. PON1 mRNA was undetectable in granulosa cells, PON2 mRNA expression was not different between follicle types, and PON3 mRNA tended to be higher in EAF (pxa0=xa00.11). The activity of PON1 in FF was higher (pxa0=xa00.01) for EAF (82.6xa0±xa08.0 kU/L) than ATF (53.9xa0±xa06.8 kU/L), as were high-density lipoproteins (HDL), low-density lipoproteins (LDL) and total cholesterol concentrations. In the second experiment, we aimed to compare plasma and FF PON1 activity in early lactation Holstein cows (nxa0=xa015) with pre-ovulatory EAF. Activity of PON1 was twofold higher (pxa0<xa00.0001) in plasma (122.5xa0±xa011.1 kU/L) than in FF (61.4xa0±xa05.2 kU/L). Plasma concentrations were also higher (pxa0<xa00.0001) for HDL, LDL and total cholesterol when compared to FF. In conclusion, FF concentrations of PON1, HDL, LDL and total cholesterol were higher in healthy oestrogen active bovine follicles than in atretic follicles. PON1 was not expressed by granulosa cells indicating that high PON1 activity in bovine FF is apparently derived by transfer from blood in association with HDL.

Exogenous paraoxonase-1 during oocyte maturation improves bovine embryo development in vitro.

Paraoxonase-1 (PON1) is an enzyme found in serum and follicular fluid that protects cell membrane and circulating lipids against oxidative damage. The aims of this study were to measure the direct effects of recombinant PON1 (rPON1) on bovine oocyte maturation at the molecular level (gene expression) and to measure the carry-over effects of PON1 on pre-implantation embryo development in vitro. COCs were submitted to IVM with the addition of 0.0, 0.02, 0.04 and 0.08xa0mgxa0ml(-1) of rPON1, corresponding to an average PON1 arylesterase enzyme activity of 2.2xa0±xa00.4, 15.5xa0±xa01.5, 30.2xa0±xa03.0 and 57.9xa0±xa05.0xa0Uxa0ml(-1) , respectively. The results indicated that addition of rPON1 during IVM improved embryo development in a dose-dependent manner as D7 embryo development was 22.2%, 29.4%, 32.2% and 37.0% for the treatment groups, respectively (pxa0=xa00.02). In conclusion, addition of PON1 enzyme during IVM exerted dose-related positive effects on embryo development rates to blastocysts.