Reproduction Of Holstein Cows Research Articles

Impact of parity number, milk production and somatic cell count on the reproduction of Holstein cows - ERRATUM.

Impact of parity number, milk production and somatic cell count on the reproduction of Holstein cows - ERRATUM.

Impact of parity number, milk production and somatic cell count on the reproduction of Holstein cows.

This research communication describes the reproductive and productive parameters and somatic cell count (SCC) of primiparous and multiparous cows from specialized dairy Holstein herds in South region of Brazil, and correlates these parameters using test-day records. A total of 24 011 records of animals from 75 producers obtained between 2017 and 2018 were used. The variables analyzed included milk production, SCC, milk fat, protein and urea nitrogen contents and reproductive characteristics (number of services per conception, service period and percentage of pregnant cows). Data were analyzed using multivariate logistic regression and the statistical differentiation between the classes of SCC and milk production. Milk production, SCC, number of services per conception and service period were all higher in multiparous cows. The percentage of pregnant cows was higher when the SCC was less than 200 000 cells/ml and was higher in primiparous cows. There was no adverse effect of milk production on reproductive parameters in high producing cows (>40 kg milk/d), however, the percentage of pregnant cows with this production level was significantly higher in multiparous cows. In conclusion, the milk production level need not affect the reproduction of specialized dairy cows if the animals are kept under adequate environmental conditions.

Association of Residual Feed Intake With Blood Metabolites and Reproduction in Holstein Cows

The objectives of this study were to evaluate the associations between residual dry matter (DM) intake or residual feed intake (RFI) from 1 to 15 weeks postpartum and concentrations of metabolites in plasma in early lactation and reproduction in Holstein cows. Data from 9 experiments, including 851 cows, were used. Intake of DM, milk yield, and body weight were evaluated daily, whereas milk composition and body condition were evaluated twice weekly for the first 105 days postpartum. Blood was sampled on the day of calving and again on days 7, 14, and 21 postpartum and analyzed for concentrations of non-esterified fatty acids (FA), β-hydroxybutyrate (BHB), and glucose. Reproduction was evaluated for the first 300 days postpartum. Residual DM intake was calculated as the observed minus the predicted intake, with intake predicted based on a model that accounted for major energy sinks. Cows were ranked and categorized into RFI quartiles, from the smallest (Q1) to the largest (Q4) RFI (−1.87, −0.46, 0.39, and 1.90 kg/day). Increasing efficiency (i.e., from Q4 to Q1) resulted in linear decreases in DM intake (Q1 to Q4; 18.9, 20.4, 21.3, and 22.7 kg/day), and median days open (132, 125, 135, and 147 d). Conversely, improving efficiency was associated with a linear increase in pregnancy per artificial insemination (AI, 31.4, 30.6, 31.2, and 24.5%) and quadratic increases in the 21-day cycle pregnancy rate (21.2, 21.1, 22.0, and 16.6%) and the proportion of pregnant cows (79.0, 80.7, 82.4, and 71.5%). The estimated net energy for lactation (NEL) content of diets increased linearly with improved RFI (1.88, 1.76, 1.71, and 1.58 Mcal/kg), resulting in no association between RFI and energy-corrected milk yield or body energy change. Nevertheless, increased feed efficiency was associated with a linear increase in concentrations of blood FA (0.68, 0.63, 0.60, and 0.59 mM), but a quadratic association with BHB (0.75, 0.64, 0.64, and 0.65 mM), with no association with glucose. Collectively, the most feed efficient cows ate 3.8 kg/day less DM, produced the same amount of energy-corrected milk, and had improved reproductive performance compared with the least efficient cows, thus suggesting that the underlying mechanisms responsible for improved feed efficiency might also be linked with improvements in reproduction.

Association of post-partum serum Ca patterns with reproduction in Holstein cows

The objective of this study was to evaluate the effects of subclinical hypocalcemia (SCHCa) patterns on reproductive performance in dairy cows. In a prospective observational study 916 cows from 9 herds were blood sampled on DIMs 1, 2, 4 and 8; Ca concentration was measured with atomic absorption and SCHCa was defined as Ca ≤ 2.09 mmol/L. Cluster analysis revealed 2 normocalcemic (NORM and HIGH) and five hypocalcemic (SCH-1 to 5) clusters. Cows in cluster NORM (n = 151) had mean day-to-day serum Ca (DIMs 1–8) between 2.24 and 2.41 mmol/L, and cows in HIGH (n = 167) between 2.42 and 2.53 mmol/L. Cows in SCH-1 (n = 130) and SCH-2 (n = 102) had transient and mostly mild SCHCa on day 1 and day 2, respectively. Cows in SCH-3 (n = 123) had mostly severe SCHCa on days 1 and 2, extending to day 4. Cows in SCH-4 (n = 120) and SCH-5 (n = 145) had SCHCa which culminated on days 4 and 8, respectively. Information on reproductive outcomes including pregnancy status by 120 and 200 DIM and days open were retrieved from farm records. Median (±SE) days to 1st artificial insemination (AI) until 120 DIM estimated with Kaplan-Meier analysis for cows in SCH-3, SCH-4 and SCH-5 were 100.0 ± 7.2, 109.0 ± 6.6 and 120.0 ± 3.2, respectively, and were statistically significantly higher from those in NORM and HIGH (91.0 ± 3.4 and 87 ± 3.7, respectively). Mean days (±SE) to detected pregnancy until 200 DIM estimated with Kaplan-Meier analysis for cows in SCH-3 were 161.2 ± 4.8 and were statistically significantly higher from those in clusters NORM and HIGH (155.5 ± 4.2 and 151.6 ± 4.3, respectively). The association of Ca clusters with the odds of detected pregnancy for the 1st insemination until 120 and 200 DIM was evaluated with Linear Mixed Models. Odds for pregnancy by 120 DIM did not differ among clusters, however, cows in clusters SCH-3 and SCH-5 had lower odds for pregnancy by 200 DIM compared to HIGH (OR = 0.55, P = 0.02, and OR = 0.49, P = 0.004, respectively). Covariate adjusted survival curves generated by multivariable Cox proportional hazards model revealed that: a) clusters SCH-3 and SCH-5 had the highest (36% and 38%, respectively), while NORM and HIGH the lowest (16% and 17%, respectively) proportion of cows not inseminated for the 1st time by 120 DIM, b) compared to HIGH, cows in SCH-5 had a lower hazard of pregnancy by 120 DIM (HR = 0.42, P = 0.005), c) the proportion of open cows by 200 DIM for NORM and HIGH were 57% and 47%, respectively, while for SCH-3 and SCH-5 66% and 68%, respectively, and d) compared to HIGH, SCH-3 (HR = 0.54, P = 0.008) and SCH-5 (HR = 0.50, P = 0.001) presented the lowest hazard for pregnancy by 200 DIM. In conclusion, cows that during the entire first week after calving were continuously normocalcemic had the best reproductive performance, while those of SCH-3 and SCH-5 the worst.

INSEMINATION INDEX AND FERTILIZATION SUCCESS IN HOLSTEIN`S CATTLE RACE AFTER RETENTION OF THE PLACENTA

Reproductive capabilities are significant economic characteristics and they are given special attention and strives to maintain at a satisfactory level or even improve by different zootechnical measures. Reproduction in Holstein cows is an introduction to production and are indirectly linked, and better reproductive characteristics in cows also give positive economic effects. Significant reproductive characteristics are the index of insemination and the success of insemination after calving. The research work was based on proving the effect of residual placenta and its retention on the mentioned reproductive properties. The first group of cows X1 consisted of cows with normal calves and numbered 34 cows, and were characterized by on time plunged placenta, with an average index of insemination of 1.2. The insemination index in the group of cows X2 containing 20 cows with residual placenta, and where reteniting of placenta was up to 30 hours after calving, was 2.1. The largest oscillation index had a group of cows X3 that counted 14 heads, where the placenta retention was made after 30 hours from the calving moment with a 4.86 index. Detailed analysis of the insemination index showed the data for the success rate of insemination, for the group X1 from the first attempt was 79.41% and from the second was 20.59%. Group X2 has an insemination performance for the first attempt of 45.0%, the second attempt was 30.0%, the third 10.0% and the fourth was 15.0%. Cows that have placental retention after 30 hours of calving, X3, the success rate of insemination is very low, and for the first attempt it was 14.3%, the second and the third to 7.15% while for the fourth and subsequent attempts was 50.0%. The best reproductive indicators had a group of cows with normal calves and calves removed on time.

Negative effects of occurrence of clinical mastitis from calving to end of the voluntary waiting period on reproduction in Holstein cows

The objective was to evaluate the effects of clinical mastitis (CM) on reproductive performance in high-milk?producing cows before the service period. The data of Holstein Friesian cows (n = 550) in a commercial farm was retrospectively evaluated. The diagnosis of CM was made by the presence of visible abnormalities in milk or symptoms of inflammation of one or more of the quarters. Cows were checked to detect CM prior to each milking. Calving to first service interval (CFSI), calving to conception interval (CCI), and services per conception (SC) were evaluated as reproductive parameters. Calving to first service interval (83.68 ± 3.18 vs. 74.57 ± 1.08; P < 0.05) and CCI (168.48 ± 8.59 vs. 132.86 ± 3.44; P < 0.001) were prolonged by 11.77% and 26.81%, respectively, and the number of SC (3.16 ± 0.21 vs. 2.42 ± 0.09; P < 0.001) was increased by 30.58% in cows experiencing CM. The culling candidate rate in nonpregnant cows was higher in the mastitis group (4.35%; 6/132) than in the healthy group (0.48%; 2/418). Calving season, time period of CM, and lactation number were not associated with the negative effects of mastitis in reproductive performance (P > 0.05). In conclusion, CM in early lactation has an adverse impact on reproductive performance in high-milk?producing dairy cows. The negative effects of CM on CFSI, CCI, and SC were not interrelated with calving season, the timing of CM, or parity.

Effect of late prepartum fibre-based diets on the live weight changes and reproduction of Holstein cows in the subsequent lactation period

The objective of this study was to evaluate two late prepartum fibre-based diets that differed in non-structural carbohydrate (NFC) and protein levels on live weight (LW) changes and fertility traits of Holstein cows until 120 days postpartum. At 30 days before calving, 120 pregnant Holsteins (heifers, n = 54 and dry cows, n = 66) from the Elsenburg herd were assigned to two nutritional treatments according to parity, expected calving date, LW, and milk production during the previous lactation. Prepartum heifers and cows were fed independently a similar type and level of a prepartum concentrate, associated with an ad libitum intake of either unchopped oat hay for the control group or a partial total mixed ration (pTMR: oat hay (48%), lucerne hay (43%) and soybean oil cake meal (9%)) for the treatment group. After parturition, cows in both the control and treatment groups were maintained on ad libitum cultivated irrigated kikuyu-ryegrass pastures, supplemented each with a post-partum concentrate of 7 kg/day from calving until 120 days in milk (DIM). As expected, young and still growing primiparous cows were significantly lighter in pre- and post-partum LW traits compared with mature multiparous cows (parity &gt; 3). Prepartum LW of cows was similar between the control and the treatment in both parity groups. Post-partum LW of the primiparous cows differed significantly between the control and the treatment, which were 488 ± 9 and 507 ± 13 kg, respectively. However, no difference was observed in terms of post-partum LW of multiparous cows of the control and the treatment groups, which were 579 ± 10 and 579 ± 8 kg, respectively. Primiparous cows that received the prepartum oat hay-based diet showed significant decrease in post-partum LW loss changes, LWnadir, LW loss at nadir and rate of LW loss from calving to LWnadir in comparison with their counterparts on the prepartum pTMR-based diet, but these LW traits were similar in multiparous cows. Prepartum diets did not have an effect on post-partum fertility parameters of the multiparous cows, whereas primiparous cows that received the control diet recorded a significantly longer interval from calving to first service (CFS) in the subsequent lactation in comparison with their counterparts fed the treatment diet i.e. 117 ± 9 and 86 ± 8 days, respectively. Proportions of cows that were pregnant at 120 DIM were similar in the subsequent lactation between groups that received the prepartum oat hay- and pTMR-based diets in both parity groups. Further research is required to investigate different prepartum feeding periods and nutritional approaches involving various levels and sources of energy and protein nutrients to encourage post-partum metabolic and hormonal responses that benefit the fertility of dairy cows in the subsequent lactation.Keywords: Dairy, dry period, non-structural carbohydrate, protein, postpartum, pregnancy

Effects of rumen-protected methionine and choline supplementation on vaginal discharge and uterine cytology of Holstein cows

Methionine is one of the most limiting amino acids in dairy diets and low feed intake around the time of calving could lead to decreased synthesis of phosphatidylcholine. An alternative pathway for phosphatidylcholine is to have choline as a precursor. The objective of this study was to determine the effects of feeding rumen-protected methionine and choline pre – and postpartum on reproduction of Holstein cows. Seventy-two Holstein cows were randomly assigned to four treatments from 21days before calving to 30days in milk (DIM): supplementation with rumen-protected methionine (MET; n=20, received 0.08% of the dry matter (DM) of the diet/d as methionine, Smartamine M® to a Lys:Met=2.9:1), rumen-protected choline (CHO; n=17, received 60g/d choline, Reassure), both rumen protected methionine and choline (MIX; n=19, received 0.08% of the DM of the diet/d as methionine to a Lys:Met=2.9:1 and 60g/d choline), or no supplementation to serve as control (CON; n=16, fed total mixed ration with a Lys:Met=3.5:1). Cows were evaluated at 4, 7, 10, 13, 15, 17, and 30d after calving for the presence of secretion using the Metricheck® device. On 15, 30, and 72d after calving, the uterine endometrium of all cows was sampled using a cytological brush and streaked onto slides for analysis of the presence of polymorphonuclear neutrophils (PMN). We hypothesized that cows supplemented with methionine would have lower metricheck smell scores and lower rates of PMN than non-supplemented cows. On d 30, a treatment difference was detected using the metricheck score and smell (P<0.04), with treatment MIX (score=0.38) having a lower score than CHO (score=2.11). Supplementing cows with rumen-protected methionine may have a beneficial effect on cows’ uterine health.

Association among gestation length and health, production, and reproduction in Holstein cows and implications for their offspring

Objectives were to evaluate associations among gestation length (GL) and performance in Holstein cows and their offspring. A total of 8,095 Holstein cows and 3,635 female offspring born alive on 2 farms using only artificial insemination (AI) were evaluated. Gestation length averaged 276 ± 6 d in the 8,095 dams, and it was categorized as short (SGL; at least 1 SD below the population mean; mean = 266 d, range 256 to 269 d), average (AGL; population mean ± 1 SD; mean = 276 d, range 270 to 282 d), or long (LGL; at least 1 SD above the population mean; mean = 285 d, range 283 to 296 d). Responses evaluated in dams included incidence of diseases within 90 d in milk (DIM), pregnancy at first AI and by 300 DIM, and time to pregnancy. Milk yield and removal from the herd by culling or death were recorded for the first 300 DIM. Responses evaluated in female offspring born alive included removal from the herd and reproductive performance. Within primiparous cows, those with SGL had greater incidence of stillbirth, retained placenta, and metritis than primiparous with AGL or LGL; however, within multiparous cows, those with SGL or LGL had greater incidence of dystocia, stillbirth, retained placenta, and metritis than cows with AGL. Morbidity and rate of morbidity were greater for SGL and LGL than AGL. Rate of removal of dams from the herd was 38% faster for SGL than AGL. Milk production was greatest in AGL cows, but responses depended on parity. For primiparous cows, milk production was less in SGL and LGL than in AGL (AGL = 35.4, SGL = 34.6, LGL = 33.0 ± 0.4 kg/d), whereas for multiparous cows, production was less in SGL but greater in LGL than in AGL (AGL = 41.6, SGL = 38.6, LGL = 42.4 ± 0.3 kg/d). A smaller proportion of cows with SGL received at least one AI, but pregnancy at first AI did not differ among groups. Rate of pregnancy was 11% slower for LGL multiparous than for AGL multiparous. By 300 DIM, pregnancy was greater in AGL than SGL. Pregnancy by 300 DIM in multiparous cows was also greater for AGL than LGL. Heifers from dams with GL that deviated from AGL had greater mortality postweaning (AGL = 3.2 vs. SGL = 6.5 vs. LGL = 5.4%). The rate of removal from the herd was greater for SGL (adjusted hazard ratio = 1.78; 95% CI: 1.26 to 2.52) and LGL (adjusted hazard ratio = 2.00; 95% CI: 1.45 to 2.76) than for AGL heifers. Pregnancy at first AI was lowest for LGL and by 500 d of age a larger proportion of AGL heifers were pregnant than LGL (AGL = 82.3 vs. SGL = 79.2 vs. LGL = 74.0%). Cows with GL within 1 SD of the population mean (270 to 282 d) had improved health, production, and reproduction. Heifers from cows with GL within 1 SD of the population mean had improved health and reproduction. Gestation length affects performance of both dams and their offspring.

Use of single nucleotide polymorphisms in candidate genes associated with daughter pregnancy rate for prediction of genetic merit for reproduction in Holstein cows.

We evaluated 69 SNPs in genes previously related to fertility and production traits for their relationship to daughter pregnancy rate (DPR), cow conception rate (CCR) and heifer conception rate (HCR) in a separate population of Holstein cows grouped according to their predicted transmitting ability (PTA) [≤-1 (n=1287) and ≥1.5 (n=1036)] for DPR. Genotyping was performed using Sequenom MassARRAY(®) . There were a total of 39 SNPs associated with the three fertility traits. The SNPs that explained the greater proportion of the genetic variation for DPR were COQ9 (3.2%), EPAS1 (1.0%), CAST (1.0%), C7H19orf60 (1.0%) and MRPL48 (1.0%); for CCR were GOLGA4 (2.4%), COQ9 (1.8%), EPAS1 (1.1%) and MRPL48 (0.8%); and for HCR were HSD17B7 (1.0%), AP3B1 (0.8%), HSD17B12 (0.7%) and CACNA1D (0.6%). Inclusion of 39 SNPs previously associated with DPR in the genetic evaluation system increased the reliability of PTA for DPR by 0.20%. Many of the genes represented by SNPs associated with fertility are involved in steroidogenesis or are regulated by steroids. A large proportion of SNPs previously associated with genetic merit for fertility in Holstein bulls maintained their association in a separate population of cows. The inclusion of these genes in genetic evaluation can improve reliabilities of genomic estimates for fertility.

FACTORS AFFECTING PREGNANCY RATES AFTER OVUM PICK UP-DERIVED EMBRYO TRANSFER IN LACTATING HOLSTEIN RECIPIENTS UNDER TROPICAL CONDITIONS

ABSTRACTHigh milk production, heat, physiological status and management impair reproduction in Holstein cows. The use of in vivo-produced embryos has been reported as an alternative to enhance pregnancy outcome in the tropics; however there are several limitations for its production, especially from variations in superovulatory responses. The in vitro production of embryos would avoid such variations, but few studies have been reported. This study aims to verify the effects of variables related to recipients under a program of routine in vitro embryo transfer on a commercial dairy farm in southeastern Brazil. It was hypothesized that pregnancy rates after transfer of ovum pick up or OPUderived embryos (ET) to lactating Holstein recipients may be influenced by recipient GnRH-treatment at ET, parity, milk production and body condition score. Recipients (267) were allocated to one of three i.m. treatments given at ET: Control (92) - 2.5 ml saline; Buserelin (86) - 10 μg Buserelin acetate; Deslorelin (89) - 750 μg Deslorelin acetate. Ultrasound images and blood samples were taken at ET and seven days later. The first pregnancy diagnosis was performed between 30-40 days and the second between 60-80 days post ET. Data were analyzed by GENMOD (SAS(r)). The proportion of pregnant cows was greater (P&amp;lt;0.05) in Buserelin-treated recipients (38.3%) at the first pregnancy diagnosis than Controls (24.1%), but similar to Deslorelin and control cows at the second diagnosis (13.0, 20.9 and 14.6% in Control, Buserelin and Deslorelin, respectively). In conclusion, Buserelin improved pregnancy rate only transitorily, under the present conditions.

Protected Methionine Prolonged Provision Improves Summer Production and Reproduction of Lactating Dairy Cows

The objective was to establish prolonged effects of a rumen-protected Met (RPM) product (SmartamineM) on milk production and reproduction of high-producing early-lactation cows under extended very high ambient temperatures. Twenty four fresh Holstein cows (27 +/- 9 days in milk, 617 kg b.wt., 2.8 body condition score) including 12 second lactation and 12 higher lactation cows were randomly assigned to either control or RPM-supplemented total mixed rations (TMR, 520:480 g kg(-1) forage:concentrate), and were fed continuously for 5 months. Cows were offered TMR 3 times daily post-milking plus a top-dress alfalfa hay. The study was conducted from May through November of 2009 in central Iranian province of Isfahan. The RPM group had consistently greater 5-month-long average DM intake (21.9 vs. 19.1 kg day(-1)), milk yield (42.4 vs. 37.4 kg day(-1)), milk fat content (33 vs. 27.5 g kg(-1)), fat yield (1.40 vs. 1.04 kg day(-1)), milk protein content (29.6 vs. 27.5 g kg(-1)) and protein yield (1.25 vs. 1.02 kg day(-1)). Mature cows tended to produce more milk (42.2 vs. 37.6 kg day(-1)) and milk fat (1.30 vs. 1.13 kg day(-1)) than second lactation cows. The RPM significantly improved ovary function, estrus expression visibility and body condition score (3 vs. 2.6), while shortening days open (106 vs. 143) and calving interval (387 vs. 421 d). Findings provide compelling evidence for beneficial effects of prolonged RPM provision on feed intake, milk production, and reproduction of Holstein cows under concurrent metabolic pressures of early lactation and stressful high ambient temperatures.

Genetic Relationship of Body Energy and Blood Metabolites with Reproduction in Holstein Cows

Body condition score (BCS), energy content (EC), cumulative effective energy balance (CEEB), and blood serum concentrations of glucose, β-hydroxybutyrate (BHBA), and nonesterified fatty acids (NEFA) were measured throughout first lactation in 497 Holstein cows raised on a large commercial farm in northern Greece. All these traits are considered to be indicators of a cow's energy balance. An additional measure of BCS, EC, and blood serum glucose, BHBA, and NEFA concentrations were taken approximately 2 mo (61±23 d) before first calving. During first lactation, first service conception rate, conception rate in the first 305 d of lactation, interval from calving to conception, number of inseminations per conception, incidence of metritis, and incidence of reproductive problems of these cows were recorded; interval between first and second calving, and second lactation first service conception rate were also recorded. Random regression models were used to calculate weekly animal breeding values for first lactation BCS, EC, CEEB, glucose, BHBA, and NEFA. Single trait animal models were used to calculate breeding values for these traits measured on pregnant heifers before calving. Reproductive records were then regressed on animal breeding values for these energy balance-related traits to derive estimates of their genetic correlations. Several significant estimates were obtained. In general, traits that are known to be positively correlated with energy balance (BCS, EC, CEEB, and glucose) were found to have a favorable genetic relationship with reproduction, meaning that increased levels of the former will lead to an enhancement of the latter. On the other hand, traits known to be negatively correlated with energy balance (BHBA and NEFA) were found to have an unfavorable genetic association with reproductive traits. Body condition score, BHBA, and NEFA recorded early in lactation, and glucose concentrations measured in pregnant heifers had the highest genetic correlation with future reproductive performance. Results suggest that genetic selection for body energy and blood metabolites could facilitate the genetic improvement of fertility and overall reproductive efficiency of dairy cows.

Case Study: Effects of Supplemental Linoleic and Linolenic Acids on Reproduction in Holstein Cows

A trial was designed to compare reproductive outcomes in a commercial dairy herd fed Megalac (calcium salts of long-chain fatty acids, Ca-LCFA, n = 1,312) or Megalac-R (Ca-LCFA+EFA, n = 708; Church and Dwight Co. Inc., Princeton, NJ). Both products are rumen-inert fat supplements of Ca-LCFA, although Megalac-R contains higher amounts of linoleic and linolenic acids. Beginning at 21 d prepartum, every cow received 0.11 kg/d of Ca-LCFA. All cows were randomly assigned to either product beginning at parturition and continuing until 150 d postpartum (0.16 kg/d). Ultrasonography was utilized to monitor ovarian status on a subset of cows less than 30 DIM. Milk samples were collected for progesterone analysis, and prostaglandins were prescribed by the herd veterinarian as a uterine therapy. Approximately 250 cows were subjected to an Ovsynch regimen to evaluate conception rates. Ultrasound results indicate that by 30 DIM, 49% of cows fed Ca-LCFA+EFA had ovulated compared with 27% of cows fed Ca-LCFA (P < 0.005). Progesterone profiles from milk sample analysis for a subset of multiparous cows showed means of 2.0 and 2.8 estrous cycles per cow by 60 DIM for the Ca-LCFA (n = 18) and Ca-LCFA+EFA (n = 17) treated cows, respectively (P < 0.05). Within the first 60 DIM, 38.9% of cows fed Ca-LCFA and 29.0% of cows fed Ca-LCFA+EFA required prostaglandin treatment (P < 0.005). No difference was detected between treatments in terms of conception rates and services per conception. In summary, the higher concentrations of linoleic and linolenic acids in Ca-LCFA+EFA contributed to improved uterine health and ovulation rates early postpartum compared with Ca-LCFA.

Effect of Grazing and Fat Supplementation on Production and Reproduction of Holstein Cows

The objective of this trial was to investigate the effects of feeding a soybean oil refining by-product (SORB), made up mainly of sodium salts of long-chain fatty acids, on reproductive performance and productivity of 36 early lactation Holstein cows managed in a free-stall barn or on annual rye-ryegrass pasture. In this 2×2 factorial arrangement of treatments, cows consumed 0 or 0.5kg/d of SORB as part of a total mixed ration for barn cows or as part of a grain supplement fed to cows on intensively, rotationally stocked pasture. Blood was sampled 3 times weekly and plasma was measured for progesterone to assess ovarian activity. Estrus activity was recorded using the HeatWatch estrus detection system. Although average 14-wk milk production (37.2kg/d) was not different among treatments, barn cows had more persistent lactations than did grazing cows. Cows housed in the barn lost less body weight and returned to initial body weight sooner and had lower mean concentrations of plasma nonesterified fatty acids (464 vs. 261mEq/L) than those managed on pasture. The milk fat of cows on pasture contained greater proportions of conjugated linoleic acid and linolenic acid but a corresponding 0.22 percentage unit decrease in milk fat concentration (3.39 vs. 3.16%). Cows managed on pasture had greater peak concentrations of plasma progesterone during the first estrous cycle. Cows managed on pasture and fed SORB had the greatest accumulation of plasma progesterone over the 14 wk of the study (SORB×housing interaction). These cows experienced the most mounts during their first estrus (9.3) and pregnancy rate was also greatest for this treatment (62.5%). Feeding SORB did not affect production of milk, fat, or protein. Loss of body condition was less in cows fed SORB. Ruminal fluid concentration of propionate increased and ruminal pH decreased in cows fed SORB. A lower proportion of fatty acids less than 18 carbons in length was found in the milk fat of cows fed SORB, thus indicating lower de novo synthesis of fatty acids. Higher proportions of C18:2n-6 and conjugated C18:2 were found in the milk fat of cows fed SORB. Based on concentrations of plasma progesterone, cows fed SORB experienced their first ovulation earlier (26.7 vs. 42.4 d postpartum) than did cows not supplemented with SORB. Neither housing system nor SORB supplementation influenced detection of first estrus (50.5 d) or the mean length of each estrus period (447min).

Continuous lactation in dairy cows: effects on feed intake, milk production, and mammary nutrient extraction

1. Effect of dry period length on the subsequent production and reproduction in Holstein cows N. Ghavi Hossein-Zadeh, A. Mohit Spanish Journal of Agricultural Research CrossRef

Influence of Bovine Somatotropin on Characteristics of Estrus and Reproduction of Holstein Cows During Summer Months

A field trial was conducted to evaluate the effects of bovine somatotropin (bST) on estrous characteristics of multiparous, lactating Holstein cows (n = 44) during the summer months. Cows were randomly assigned to receive bST every 14 d or no bST (control) and were fitted with a HeatWatch® transmitter (HW; DDx Inc., Denver, CO). A temperature-humidity index (THI) was calculated for the day of estrous onset. Ranges of THI were 68 to 80 (THI < 72 = THI 1 [no heat stress], THI 72 to 76 = THI 2 [mild heat stress], THI > 76 = THI 3 [moderate heat stress]). Duration of estrus, number of standing events, and quiescent periods between standing events were similar (P>0.10) between bST and control cows. The number of standing events was influenced (P<0.05) by THI and averaged 20.3 ± 3.0, 8.6 ± 1.3, and 8.9 ± 1.2 for THI 1, THI 2, and THI 3, respectively. Quiescent periods observed between standing events tended (P=0.11) to be influenced by THI and were 1.2 ± 0.8, 3.0 ± 0.4, and 3.0 ± 0.4h for THI 1, THI 2, and THI 3, respectively. Days to first service were less (P=0.07) for bST-treated cows (90.9 ± 5.1 d) than for control cows (105.9 ± 6.1 d). First service conception rates and pregnancy rates were similar (P>0.10) between bST-treated and control cows. We conclude that estrous characteristics and pregnancy rates of lactating dairy cows were not influenced by bST treatment. However, the number of standing events was reduced, and quiescence between mounts tended to increase, in lactating dairy cows as ambient temperature and humidity increased.

Effect of beta-carotene supplementation on periparturient health and reproduction of Holstein cows

Two trials involving 57 Holstein cows were conducted to determine the effect of feeding 300 mg supplemental beta-carotene from 30 days before expected parturition to 98 days postpartum on periparturient health and subsequent reproductive performance. Feeding supplemental beta-carotene reduced ( P < 0.05) the dystocia score in trial 1 only. Supplementation had no effect ( P > 0.05) on the incidence of placental retention and ovarian cysts, rate of uterine involution, fertility, milk production or somatic cell counts. Thus, benefits in health, reproduction or milk production were not generally observed from feeding supplemental beta-carotene to Holstein cows fed a diet commonly used in the United States.

Relationships Between Conformation and Reproduction in Holstein Cows: Type and Calving Performance

Type information collected by the Holstein Association of Canada was matched with calving ease data provided by the Ontario Dairy Herd Improvement Corporation. Type traits considered were final class, general appearance, dairy character, capacity, rump, feet and legs, mammary system, fore udder, rear udder, and eight descriptive traits: stature, size, style, dairyness, chest floor, loin strength, thurl width, and pin setting. Edited data consisted of records on 7,193 first calf heifers from 775 sires in 2,133 herd-round of classification groups. A total of 3,546 sires also had proofs available for both conformation and calving ease as a maternal trait.Heritability for calving performance was .07. Heritability estimates for type ranged from .10 for style to .43 for size. Phenotypic correlations between type traits and calving performance were essentially zero. Type traits with the highest favorable genetic correlations with calving performance were style (−.36), fore udder (−.35), final class (−.33), mammary system (−.33), general appearance (−.28), and rump (−.28). Feet and legs, chest floor, size, and capacity were associated genetically with an increase in calving difficulty. After accounting for the direct genetic effect, the correlations between sire proofs for size of cow, capacity, and width of chest with calving ease as a maternal trait were favorable.Direct selection is more efficient in improving calving performance than indirect selection for any type trait considered.