Comparison of milk and grass composition from grazing Irish dairy herds with and without milk fat depression.

BACKGROUND: This study investigated the factors relating to pasture chemical and fatty acid (FA) composition that influence the milk fat percentage of spring calving, grazing dairy cows. The relationship between milk fat percentage and FA composition of the milk in these herds was also investigated. RESULTS: Milk protein percentage, milk casein percentage and cheddar cheese yield were increased in milk from HMF herds. Cows from LMF herds did not have negatively altered milk processability including rennet coagulation time (RCT), pH and ethanol stability. Crude protein, NDF, ADF, ether extract and total FA content of pasture was not different between LMF and HMF herds. Milk fat concentration of conjugated linoleic acid (CLA) t10, c12 was not different between HMF and LMF herds. Pre-grazing herbage mass and pasture content of crude protein, neutral detergent fibre (NDF) and total FA were similar between HMF and LMF herds. Pasture offered to LMF herds had a higher concentration of monounsaturated fatty acids (MUFA). A strong negative relationship (r = -0.40) was evident between milk fat percentage and pasture crude protein content for MMF herds (3.31-3.94% milk fat). CONCLUSIONS: This research reports improved milk protein percentage, milk casein percentage and cheddar cheese yield from HMF herds compared to LMF herds. Milk processability was not impacted by low milk fat percentage. Pasture NDF and total fatty acid content was similar in HMF herds and LMF herds. Milk fat percentage had a strong negative association (r = -0.40) with pasture crude protein content in MMF herds (MF 3.31-3.94%). Correlation values between pasture chemical and FA composition and milk fat percentage in LMF herds and HMF herds were low, indicating that diet is not the only causative factor for variation in milk fat of grazing dairy cows. Comparison of milk fatty acid composition from herds with and without milk fat depression suggests that there may be other fatty acids apart from CLA t10, c12 that contribute to the inhibition of milk fat synthesis during milk fat depression in grazing herds.

Effects of calcareous marine algae on milk production, feed intake, energy balance, mineral status, and inflammatory markers in transition dairy cows.

The objective of this experiment was to compare the effects of calcareous marine algae (CMA; Acid Buf, Celtic Sea Minerals) with a limestone-based control on feed intake, milk production, energy balance, serum mineral metabolites, and inflammatory markers in transition dairy cows. Twenty-two multiparous and 10 primiparous cows were assigned to 2 treatments from 25 d before expected parturition until 42 d postpartum. Cows were assigned to treatment according to a randomized complete block design based on parity, pre-experimental body condition score, previous 305-d milk yield, and either fat + protein yield (for multiparous cows) or predicted transmitting ability for milk yield and fat + protein yield (for primiparous cows). Cows were fed a negative dietary cation-anion difference [-50 mEq/kg] total mixed ration (TMR) based on corn silage, grass silage, and straw during the prepartum period and a 50:50 forage:concentrate TMR based on grass silage, corn silage, and concentrate during the postpartum period. The 2 dietary treatments consisted of a control (CON), which contained limestone as the primary calcium source, and CMA, in which limestone was replaced by CMA at 0.42% and 0.47% of dry matter for the pre- and postpartum periods, respectively. The dietary treatments were fed as 2 different concentrate pellets added to the TMR. Cows fed the CMA diet had higher dry matter intake in both the prepartum (+1.08 kg) and postpartum (+0.94 kg) periods compared with cows fed the CON diet. Fat yield (+0.11 kg), fat concentration (+0.43%), and 4% fat-corrected milk (+1.56 kg) were higher in cows fed CMA than in cows fed CON. The concentration of plasma serum amyloid A was reduced and that of serum P was increased on the CMA treatment compared with the CON treatment. These findings demonstrate the benefits of supplementing CMA to dairy cows during the transition period compared with a CON treatment containing limestone as the primary Ca source.

Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system.

This study used a stochastic simulation model to estimate the potential economic benefit of using timed artificial insemination (TAI) in combination with conventional unsorted (TCONV) and sexed (TSEX) semen in heifers only (TCONV-H, TSEX-H) and in both heifers and lactating cows (TCONV-HC, TSEX-HC) in a high-producing, pasture-based production system. The scenarios were compared with a conventional reproductive policy (CONV) in which heifers and cows were inseminated with conventional unsorted semen after estrus detection. Sensitivity analysis was also used to estimate the effect of hormone costs from TAI use on the profitability of each program relative to CONV. The mean annual (± standard deviation) profit advantage (ΔPROF) over CONV for TCONV-H, TCONV-HC, TSEX-H, and TSEX-HC scenarios were €3.90/cow ± 4.65, €34.11/cow ± 25.69, €13.96/cow ± 6.83, and €41.52/cow ± 42.86, respectively. Combined application of both technologies was shown to return a greater annual ΔPROF on average compared with that achievable from TAI alone. However, the risk of not returning a positive annual ΔPROF varied across the scenarios with higher risk in TCONV-H and TSEX-HC. Specifically, TCONV-H and TSEX-HC had a 24 and 18% chance, respectively, of not returning a positive annual ΔPROF. Sensitivity analysis showed that when hormone costs increased by €10/cow TCONV-H and TSEX-HC had a 38 and 23% chance, respectively, of not returning a positive annual ΔPROF. The range in ΔPROF for TCONV policies was most sensitive to the TAI pregnancy rate and TSEX policies were most sensitive to the relative fertility achieved with sexed compared with unsorted semen. This study has shown TAI and sexed semen are complementary technologies that can increase genetic gain and profitability in a pasture-based, dairy production system.

Effect of supplement crude protein concentration on milk production over the main grazing season and on nitrogen excretion in late-lactation grazing dairy cows.

The objectives of this study are to evaluate the effects of (1) a potential interaction between supplement crude protein (CP) concentration and differing cow genotypes on milk production, (2) differing cow genotypes on milk production, and (3) decreasing the supplement CP concentration on milk production and N excretion during the main grazing season within a spring-calving herd. A 2 × 2 factorial arrangement experiment, with 2 feeding strategies [14%; n = 30 (lower CP; LCP) and 18%; n = 28 (higher CP; HCP) CP concentrate supplements] offered at varying levels according to pasture availability and days in milk (DIM) was conducted over the main grazing season from April 3 to September 3, 2019, at University College Dublin Lyons Farm. Cows were also grouped into 2 genotype groups: lower milk genotype; n = 30 [LM; milk kg predicted transmitting ability (PTA): 45 ± 68.6 (mean ± SD); fat kg PTA: 10 ± 4.9; and protein kg PTA: 7 ± 2.3] and higher milk genotype; n = 28 [HM; milk kg PTA: 203 ± 55.0; fat kg PTA: 13 ± 3.8; and protein kg PTA: 10 ± 2.4]. A total of 46 multiparous and 12 primiparous (total; 58) Holstein Friesian dairy cows were blocked on parity and balanced on DIM, body condition score, and Economic Breeding Index. Cows were offered a basal diet of grazed perennial ryegrass pasture. The N partitioning study took place from August 25 to 30, 2019 (187 ± 15.2 DIM). No interactions were observed for any milk production or milk composition parameter. No effect of supplement CP concentration was observed for any total accumulated milk production, daily milk production, or milk composition parameter measured. The HM cows had increased daily milk yield (+1.9 kg), fat and protein (+0.15 kg), and energy-corrected milk (+1.7 kg), compared with the LM cows. Furthermore, HM cows had decreased milk protein concentration (-0.1%) compared with LM cows. For the N partitioning study, cows offered LCP had increased pasture dry matter intake (PDMI; +0.9 kg/d), dietary N intake (+0.022 kg/d), feces N excretion (+0.016 kg/d), and decreased N partitioning to milk (-2%), and N utilization efficiency (-2.3%). In conclusion, offering cows LCP had no negative influence on milk production or milk composition over the main grazing season where high pasture quality was maintained. However, any potential negative effects of offering LCP on milk production may have been offset by the increased PDMI. Furthermore, offering cows LCP decreased N utilization efficiency due to the higher PDMI and feed N intake associated with cows on this treatment in our study.

The effect of nutritional management in early lactation and dairy cow genotype on milk production, metabolic status, and uterine recovery in a pasture-based system.

High levels of milk production coupled with low feed intake cause negative energy balance in early lactation, especially in the first month postpartum (PP). Therefore, specific nutritional management at this time may improve nutritional and metabolic status with the possibility of contrasting genotypes responding differently. Thus, the objective of this study was to compare the effects of nutritional management strategies and dairy cow genotype on milk production, metabolic status, and some fertility parameters during early lactation in a pasture-based system. Sixty Holstein Friesian cows were blocked on parity and genotype [low-fertility high-milk (LFHM) and high-fertility low-milk (HFLM)] and were randomly assigned to 1 of 2 treatments in a 2 × 2 factorial arrangement, in a randomized complete block design based on calving date, previous 305-d milk yield, and precalving body condition score (BCS). The nutritional management treatments were: (1) ad libitum access to fresh pasture plus an allowance of 3 kg of concentrates per day (CTR, n = 30); and (2) ab libitum access to a tailored total mixed ration (TMR, n = 30). These diets were offered for the first 30 d PP. Following the first 30 d PP, cows fed TMR joined the CTR treatment and were managed similarly until 100 d PP. Blood samples were taken at d 7, 14, 21, and 28 PP to determine metabolic status. Milk samples for composition analysis were collected weekly and BCS assessed every 2 wk. Genotype had a significant effect on milk output, whereas LFHM had increased fat (+0.28 kg/d) and fat-plus-protein (+0.17 kg/d) yield in the first 30 d PP compared with HFLM cows. The LFHM group also exhibited higher protein and lactose yields over the first 100 d PP. Nutritional management did create significant differences in milk composition in the first 30 d: TMR cows had lower protein, milk urea nitrogen, and casein concentration and higher lactose concentration than CTR cows. Over the first 100 d PP, TMR cows had higher fat-plus-protein and lactose yields. Feeding TMR reduced concentrations of nonesterified fatty acids (-0.12 mmol/L) and ß-hydroxybutyric acid (-0.10 mmol/L) compared with the CTR group. Cows fed TMR had smaller BCS losses from calving to 60 d PP. There was no effect of any treatment on uterine recovery. Cows in the LFHM group demonstrated greater milk production in the first 30 and 100 d in milk. These results demonstrate that feeding cows a TMR for the first month of lactation has positive effects on milk output, metabolic status, and BCS profile.

Effects of herd fertility on the economics of sexed semen in a high-producing, pasture-based dairy production system.

This study used a stochastic simulation model to estimate the potential economic benefit of using sexed semen in heifers only and in heifers and lactating cows in a high-producing, pasture-based system under 3 fertility scenarios. Three breeding strategies were modeled: (1) only heifers inseminated with sexed semen and cows inseminated with conventional unsexed semen (SSH); (2) both heifers and cows inseminated with sexed semen (SSHC); and (3) a reference scenario in which all females were inseminated with conventional, unsexed semen (CONV). Each scenario was evaluated under 3 herd fertility states: high (HF), medium (MF), and low (LF), which, under the reference scenario, corresponded to herd replacement rates of 21, 25, and 31%, respectively. The model estimated the economic profit, including the net present value of the genetic gain from selection intensity. The economic return from adoption of sexed semen strategies declined, with reduced levels of baseline herd fertility turning negative in the LF state. The mean (±SD) sexed semen advantage (SSA) per cow for HF-SSH, MF-SSH, and LF-SSH scenarios were €30.61 ± 8.98, €27.45 ± 7.19, and €14.69 ± 11.06, respectively. However, the SSA per cow for HF-SSHC, MF-SSHC, and LF-SSHC scenarios were €49.14 ± 15.43, €18.46 ± 30.08, and -€19.30 ± 57.11. The range in economic profit for SSA for SSH was most sensitive to calf prices in HF-SSH and the pregnancy rate of sexed semen as a percentage of conventional unsorted semen in MF-SSH and LF-SSH. The range in economic profit for SSA for SSHC scenarios was most sensitive to the pregnancy rate of sexed semen as a percentage of conventional unsorted semen in HF-SSHC, MF-SSHC, and LF-SSHC. This study highlights the effect of baseline herd fertility state on the financial advantage of adopting sexed semen in a pasture-based dairy production system.

Effects of a novel heat-treated protein and carbohydrate supplement on feed consumption, milk production, and cheese yield in early-lactation dairy cows.

Protein is an expensive component of the dairy cow diet, and overfeeding protein can have adverse economic and environmental impacts. Our objective was to maintain milk production and components while decreasing dietary crude protein (CP) through use of a heat-treated, rumen-resistant sugar amino acid complex (SAAC) as the Schiff base, as an addition to low-protein diets. Dietary treatments included a negative control [NC, 146 g of CP/kg of dry matter (DM)], a positive control (PC, 163 g of CP/kg of DM), and the NC supplemented with SAAC in lieu of some barley grain (SAAD, 151 g of CP/kg of DM). Diets were fed to 30 multiparous Holstein-Friesian dairy cows for the first 50 d postpartum. Dry matter intake (DMI) was determined daily. Milk yield and content of fat, protein, lactose, and casein were recorded weekly from wk 2 to 7 of lactation. The fixed effects of treatment, week, treatment × week, month of calving, and BCS at calving, and a random effect of cow, were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). The SAAD treatment had greater energy-corrected milk yield than did NC. The PC treatment had greater DMI than did NC, and SAAD tended to have greater DMI than did NC. We found significant treatment effects for fat percentage and yield. The NC and SAAD treatments had higher fat percentages than did PC, and SAAD had a higher fat yield than did the NC and PC treatments. Treatment effects were found for casein yield and percentage. We discovered a treatment effect for protein percentage and yield. The PC treatment had higher protein percentage than did NC and SAAD. The PC treatment had a higher protein yield than did NC, and analysis revealed no difference in protein yield between PC and SAAD. The SAAD treatment had higher total milk solids than did the NC treatment. Lactose yield tended to be higher in PC than in NC, and no differences were found between PC and NC and SAAD treatments. The PC treatment had a higher casein percentage than did NC and SAAD; however, the SAAD and PC treatments had higher casein yields than did NC. The PC treatment had a higher casein:fat ratio than did the NC and SAAD treatments. The NC and SAAD treatments had higher Cheddar cheese yields than did PC. We found no treatment × week interactions for any parameter. Supplementing low-protein dairy cow diets with a heat-treated, rumen-resistant SAAC caused beneficial effects by improving milk components and increasing cheese yield to levels similar to those found when feeding expensive and environmentally damaging high-protein diets.

The effect of calcareous marine algae, with or without marine magnesium oxide, and sodium bicarbonate on rumen pH and milk production in mid-lactation dairy cows.

Two experiments were carried out to evaluate different dietary buffers and their influence on (1) rumen pH in dairy cows and (2) milk production in dairy cows. The supplements included were calcareous marine algae (CMA; Lithothamnion calcareum), with or without marine magnesium oxide (MM; precipitated magnesia derived from seawater), and sodium bicarbonate (SB). Dietary treatments in experiment 1 consisted of the control [32.9% starch and sugar, and 19.9% neutral detergent fiber from forage per kg of dry matter (DM)] including no dietary buffer (CON); the control plus 0.45% DM CMA (CMA); the control plus 0.45% DM CMA and 0.11% DM MM (CMA+MM); the control plus 0.9% DM SB (SB). Diets were formulated to a dry matter intake (DMI) of 18 kg per cow/d. Dietary treatments in experiment 2 also consisted of CON (28.3% starch and sugar, and 23% neutral detergent fiber from forage per kg of DM), CMA, CMA+MM, and SB and were formulated to achieve identical intakes of experimental ingredients (80 g of CMA, 80 g of CMA plus 20 g MM, and 160 g of SB per cow/d) with a DMI of 22.6 kg per cow/d. Experiment 1 used 4 rumen-cannulated dairy cows in a 4 × 4 Latin square design. Rumen pH was measured over five 2-h periods, following feeding, using rumen pH probes. In experiment 2, 52 multiparous and 4 primiparous cows (62.7 ± 3.4 d in milk) were assigned to 4 experimental treatments for 80 d. Both CMA treatments maintained a greater mean rumen pH than the CON during 4 of the 5 periods following feeding and the CON had a greater number of hours below rumen pH 5.5 compared with all other treatments. Dry matter intakes tended to be higher on the SB compared with CON. The CMA treatment increased the production of milk fat and protein yield (kg/d) compared with all other treatments. Both CMA and CMA+MM increased milk fat yield compared with CON but were similar to each other and SB. Protein yield was highest in the CMA treatment compared with CON, CMA+MM, and SB. All 3 buffer treatments increased milk fat concentration compared with CON but did not differ from each other. The SB treatment reduced milk protein concentration and milk production efficiency, energy-corrected milk per kilogram of DMI. Results indicate that the addition of CMA can benefit milk fat and protein production when included in diets based on typical feedstuffs of the northern European region. The use of CMA when compared with SB, in such diets, can increase milk protein production and milk production efficiency.

Bioeconomics of sexed semen utilization in a high-producing Holstein-Friesian dairy herd.

A bioeconomic, stochastic spreadsheet model, that included calculation of the net present value of the additional value of all future descendants resulting from increased selection intensity, was developed to study the profitability of using sexed semen in a high input-high output dairy herd. Three management strategies were modeled: (1) only heifers inseminated with sex-sorted semen and cows inseminated with unsorted semen; (2) both heifers and cows inseminated with sex-sorted semen; and (3) a reference scenario, in which all breeding females were inseminated with unsorted semen. A Monte Carlo simulation (@risk software, Palisade Corp., Ithaca, NY) was run to study the sensitivity of net profit and sexed semen advantage to key input parameters. Most input parameters were given truncated normal distributions, whereas the maximum numbers of inseminations in heifers and cows were given discrete distribution functions. The calculated intensity of selection accounted for the different numbers of dairy females born for each of the 100,000 iterations. Using sexed semen (X-sorted, female) was shown to be profitable, with insemination of both heifers and cows being most profitable. The returns on assets were higher when only heifers were inseminated with sexed semen (8.54% ± 2.94; ±SD) or all females were inseminated with sexed semen (8.85% ± 2.93) than when all females were inseminated with unsexed semen (8.38% ± 2.95). The range in net profit was most sensitive to the assumed distributions of milk protein price (€/kg), milk fat price (€/kg), cow pregnancy rate, fertilizer price (€/t), and concentrate price (€/t) when unsorted semen was used. When only heifers or both heifers and cows were inseminated with sex-sorted semen, the range in net profit was most sensitive to the same distributions, with fertilizer price and cow pregnancy rate in reverse order of sensitivity. However, the range in sex-sorted semen advantage (in net profit) when only heifers were inseminated with sex-sorted semen was most sensitive to the assumed distributions of cow pregnancy rate, sex-sorted semen pregnancy rate as a percent of unsorted semen rates, standard deviation of index, additional cost of sex-sorted semen (€/dose), dairy bull calf price (€/head), and dairy heifer calf price (€/head). When both heifers and cows were inseminated, the order of importance of the last 2 inputs was reversed. This study highlights the relatively high effect of pregnancy rate and the genetic value of dairy bulls in determining the level of financial advantage from using sex-sorted semen in a dairy herd.

A comparison of serum metabolic and production profiles of dairy cows that maintained or lost body condition 15 days before calving.

Body condition score (BCS) change is an indirect measure of energy balance. Energy balance before calving may affect production and health in the following lactation. It is likely that cows may experience BCS loss before calving due to negative energy balance. The objective of this study was to determine if loss of BCS 15d before calving affected milk production, BCS profile, and metabolic status during the transition period and early lactation. On d -15 to d 0 relative to calving, BCS was assessed (1=emaciated, 5=obese) for 98 Holstein-Friesian cows. The cows were divided into 2groups: those that did not lose BCS between d -15 and d 0 (maintained, BCS-M, n=55) and those that lost BCS from d -15 to d 0 (lost, BCS-L, n=43, average loss of 0.29±0.11 BCS). The fixed effects of BCS group, parity, week (day when analyzing milk production records), their interactions, and a random effect of cow were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Before calving, BCS-L cows tended to have higher concentrations of nonesterified fatty acids than BCS-M cows (0.88 vs. 0.78mmol/L). After calving, BCS-L cows had higher nonesterified fatty acid concentrations in wk 1 (0.93 vs. 0.71mmol/L), wk 2 (0.84 vs. 0.69mmol/L), and wk 4 (0.81 vs. 0.63mmol/L) than BCS-M cows. The BCS-L cows had higher concentrations of ß-hydroxybutyrate (BHB) in wk 1 (0.72 vs. 0.57mmol/L), wk 2 (0.97 vs. 0.70mmol/L), and wk 4 (0.94 vs. 0.67mmol/L) compared with BCS-M cows. We detected significant reductions in insulin concentrations in BCS-L cows from wk -1 (2.23 vs. 1.37 µIU/mL) to wk 2 (1.68 vs. 0.89 µIU/mL) and wk 4 (2.21 vs 1.59 µIU/mL) compared with BCS-M cows. Prevalence of subclinical ketosis increased in BCS-L cows in wk 3 and 4 when BHB was ≥1.4mmol/L and in wk 1, 3, and 4 when BHB was ≥1.2mmol/L. In wk 1, BCS-L cows tended to have lower levels of calcium than BCS-M cows (2.33 vs. 2.27mmol/L). We found no differences between the groups of cows for milk yield and energy-corrected milk. The BCS-L cows had lower BCS up to 75d in lactation. Overall, BCS-L cows had higher somatic cell scores with an elevated somatic cell score on d 45, d 60, and d 75. There was an overall tendency for BCS-L cows to have higher fat yield and an overall significant increase in fat percentage. Overall, BCS-L cows had lower lactose percentage, with a reduction on d 60. This work shows that BCS loss before calving may have significant consequences for metabolic status, milk composition, somatic cell score, and BCS profile in dairy cows.

Comparison of energy rationing systems for late gestation ewes: Impacts on ewe and lamb performance.

The objectives of this study were 1) to compare the effects of a ME () or a NE () system for rationing ewes during late gestation on ewe and progeny performance and 2) to investigate incremental increases in NE allocation above 100% of recommendation during late gestation on ewe and progeny performance. Fifty-two twin-bearing ewes ( = 13 per treatment) were rationed to either 100% of recommended ME requirements (100% ME) or 100, 110, or 120% of recommended NE requirements (100% NE, 110% NE, and 120% NE) from d 112 of gestation to parturition. Mean energy intake, measured as ME and NE, from Day 112 of gestation to parturition was higher in all NE treatments compared with 100% ME ewes ( = 0.01). Ewes offered the 3 NE treatments had a higher live weight at parturition compared with 100% ME ewes ( = 0.02), with 100% NE and 120% NE ewes still being heavier than 100% ME ewes at 35 d postpartum ( = 0.02). Increasing NE allowance resulted in a linear decrease in the level of BCS loss prepartum ( = 0.01) and a linear increase in the level of BCS loss postpartum ( = 0.01). There was no difference observed between any of the treatments in total colostrum produced to 18 h postpartum ( = 0.29) or in total colostrum intake to 18 h postpartum ( = 0.27). Increasing maternal NE allowance led to a linear increase in lamb serum IgG concentration at 24 h postpartum ( = 0.03). The estimated milk production of 120% NE ewes tended to be higher than all other treatments at wk 6 of lactation ( = 0.08). Colostral SFA levels from 100% ME ewes was lower than that of all 3 NE treatments ( = 0.01), and unsaturated fatty acid (UFA) levels in colostrum of the 100% ME ewes were lower than those of the 100% NE ewes ( = 0.01). Cumulative levels of milk SFA, UFA, and MUFA did not differ between treatments ( = 0.19). Lamb growth rates during the first 5 wk postpartum were unaffected by treatment ( = 0.18) as were days to slaughter ( = 0.34). It can be concluded that both ME and NE systems used in this study are appropriate for formulating ewe diets during late gestation. Increasing NE allocation above 100% altered the pattern of body reserve mobilization during late gestation and early lactation without observed variations in lamb performance during this time.

Endocrine and hematological responses of beef heifers divergently ranked for residual feed intake following a bovine corticotropin-releasing hormone challenge.

The objective of this study was to determine if beef heifers divergently ranked on phenotypic residual feed intake (RFI) differed in their physiological stress response to an exogenous bovine corticotropin-releasing hormone (bCRH) challenge. Yearling Limousin × Friesian heifers ( = 86) were ranked by RFI. The 15 highest (mean 0.66 kg DM/d; high RFI) and 15 lowest (mean -0.72 kg DM/d; low RFI) ranking animals were used for this study. During the study period, heifers (mean age 485 ± 13 d; mean BW 408 ± 31.4 kg) were housed in a slatted-floor facility. To facilitate intensive blood collection, heifers were fitted aseptically with indwelling jugular catheters. All heifers received dexamethasone (DEX; 20 µg/kg BW i.m.) 12 h before the bCRH challenge (d 0). Heparinized blood samples were collected at -60 and 0 min before administration of DEX, and 12 h after DEX administration. Following DEX administration, cortisol and dehydroepiandrosterone (DHEA) concentrations similarly decreased ( ≥ 0.22) between high and low RFI groups. The response of the HPA axis to a standardized dose of bCRH (0.3 µg/kg BW) was examined. On d 0, serial blood samples were collected at -20, 0, 20, 40, 60, 80, 100, 120, 150, 180, 210, 240, 270, 330, and 390 min relative to the time of bCRH administration (0 min) and were analyzed for plasma cortisol and DHEA concentrations. Blood hematology variables were also determined at -20, 0, 20, 80, 150, 270, 330, and 390 min relative to bCRH administration. Neither an RFI × sampling time interaction nor a direct effect of RFI were detected ( ≥ 0.36) for plasma cortisol, DHEA concentrations, or cortisol:DHEA ratio. An effect of sample time was observed for cortisol ( < 0.001), DHEA ( = 0.04), and cortisol:DHEA ( = 0.02), with cortisol concentration peaking at 60 min post-CRH administration. The maximum concentration and rate of change in cortisol and DHEA concentrations following bCRH administration were not different ( ≥ 0.20) between the high and low RFI phenotypes. Similarly, an effect of RFI was not evident ( ≥ 0.16) for any of the hematology variables examined including neutrophil, lymphocyte, and leukocytes counts; white and red blood cell numbers; and hemoglobin concentrations. Our results suggest that responsiveness of the HPA to stress, at least at the level of the anterior pituitary gland, is not a significant contributor to variation in RFI among growing beef heifers.

Genetic selection for increased mean and reduced variance of twinning rate in Belclare ewes.

It is sometimes possible to breed for more uniform individuals by selecting animals with a greater tendency to be less variable, that is, those with a smaller environmental variance. This approach has been applied to reproduction traits in various animal species. We have evaluated fecundity in the Irish Belclare sheep breed by analyses of flocks with differing average litter size (number of lambs per ewe per year, NLB) and have estimated the genetic variance in environmental variance of lambing traits using double hierarchical generalized linear models (DHGLM). The data set comprised of 9470 litter size records from 4407 ewes collected in 56 flocks. The percentage of pedigreed lambing ewes with singles, twins and triplets was 30, 54 and 14%, respectively, in 2013 and has been relatively constant for the last 15 years. The variance of NLB increases with the mean in this data; the correlation of mean and standard deviation across sires is 0.50. The breeding goal is to increase the mean NLB without unduly increasing the incidence of triplets and higher litter sizes. The heritability estimates for lambing traits were NLB, 0.09; triplet occurrence (TRI) 0.07; and twin occurrence (TWN), 0.02. The highest and lowest twinning flocks differed by 23% (75% versus 52%) in the proportion of ewes lambing twins. Fitting bivariate sire models to NLB and the residual from the NLB model using a double hierarchical generalized linear model (DHGLM) model found a strong genetic correlation (0.88 ± 0.07) between the sire effect for the magnitude of the residual (VE ) and sire effects for NLB, confirming the general observation that increased average litter size is associated with increased variability in litter size. We propose a threshold model that may help breeders with low litter size increase the percentage of twin bearers without unduly increasing the percentage of ewes bearing triplets in Belclare sheep.

Effects of gestation housing system and floor type during lactation on locomotory ability; body, limb, and claw lesions; and lying-down behavior of lactating sows.

This study evaluated the influence of housing system during gestation and floor type during lactation on the welfare and lying-down behavior of lactating sows. Multiparous sows (n = 85) were housed either in individual gestation stalls (n = 42) or loose (n = 43) in a single dynamic group with 2 electronic sow feeders moved to farrowing crates on either slatted steel (n = 48) or cast iron (n = 37) flooring. Lameness (0 = normal to 5 = severely lame) was scored on transfer to the farrowing crate (-5 d). Limb and body lesions were recorded on -5 d, 24 h after entering the farrowing crate (-4 d), 10-d postpartum, and before weaning. Claw lesions were recorded on -5 d and before weaning, whereas all behavioral observations were made on -5, -4, and 10 d. Median (Me) scores were calculated for claw, body, and limb lesions and classified as either less than or equal to the Me or greater than the Me lesion scores. Sows were classified as nonlame (≤ 1) or lame (≥ 2). Loose-housed sows had an increased (P < 0.01) risk of lameness; a reduced (P < 0.05) risk for claw lesions, particularly white line damage, horizontal wall cracks, and dewclaw injuries; and a reduced (P < 0.05) risk for calluses and bursitis on the limbs compared to stall-housed sows. Sows housed on cast iron floors during lactation had a reduced (P < 0.01) risk for heel overgrowth and erosion and heel-sole cracks compared with sows on slatted steel floors. There was no (P > 0.05) association between flooring type during lactation and body lesion score. On -4 d, loose-housed sows had a shorter latency to lie down (P < 0.01), spent more time inactive (P < 0.05), and shifted weight between the limbs more often (P = 0.05) while standing compared with stall-housed sows. Lame sows had a shorter (P < 0.01) latency to lie down compared to nonlame sows on -5 and -4 d. In conclusion, there was an increased risk of lameness in sows housed loose compared to those housed in gestation stalls on transfer to the farrowing crate. Claw health deteriorated in the farrowing crate regardless of gestation housing or floor type but the deterioration in claw health was increased on slatted steel compared to on cast iron.

Feeding behavior, ruminal fermentation, and performance of pregnant beef cows differing in phenotypic residual feed intake offered grass silage.

This study examined the relationship of residual feed intake (RFI) and performance with feeding behavior and ruminal fermentation variables in pregnant beef cows offered a grass silage diet. Individual grass silage DMI (dry matter digestibility = 666 g/kg) was recorded on 47 gestating (mean gestation d 166, SD = 26 d) Simmental and Simmental × Holstein-Friesian beef cows for a period of 80 d. Cow BW, BCS, skeletal measurements, ultrasonically scanned muscle and fat depth, visual muscular score, ruminal fermentation, blood metabolites, and feeding behavior were measured. Phenotypic RFI was calculated as actual DMI minus expected DMI. Expected DMI was computed for each animal by regressing DMI on conceptus-adjusted mean BW(0.75) and ADG over an 80-d period. Within breed, cows were ranked by RFI into low (efficient), medium, or high groups. Overall mean (SD) values for DMI (kg/d), RFI, initial conceptus-adjusted BW, and conceptus-adjusted ADG were 8.41 (1.09) kg/d, 0.01 (0.13) kg/d, 646 (70) kg, and -0.07 (0.32) kg, respectively. High-RFI cows ate 25% and 8% more than low- and medium-RFI cows, respectively. Live weight and ADG were not correlated (P > 0.05), and DMI was positively correlated (r = 0.80; P < 0.001) with RFI. The low- and high-RFI groups had similar (P > 0.05) BW, ADG, BCS, visual muscular scores, skeletal measurements, blood metabolites, calf birth weight, and calving difficulty scores. All ultrasonic fat and muscle depth measurements were similar (P > 0.05) for low- and high-RFI cows except for back fat thickness change, where low-RFI cows gained less fat (P < 0.05) than high-RFI cows. Low-RFI cows had greater pH and lower ammonia concentrations in ruminal fluid compared to their high-RFI contemporaries. Low-RFI cows had fewer (P < 0.001) daily feeding events, but these were of longer (P < 0.001) duration (min·feed event(-1)·d(-1)). Despite this, total daily duration of feeding was shorter (P < 0.001; min/d) for low- compared to high-RFI cows. High-RFI cows had more and a longer total duration of nonfeeding events (P < 0.001) than low-RFI cows. This study showed that compared to cows with high RFI, those with low RFI consumed less feed for similar levels of productivity, spent less time engaged in feeding-behavior-related activities, and differed in ruminal fermentation parameters. Feeding events are a significant (17%) contributory factor to variation in RFI in pregnant beef cows offered grass silage.

Management factors affecting mortality, feed intake and feed conversion ratio of grow-finishing pigs.

The aim of this study was to determine the effect of animal management and farm facilities on total feed intake (TFI), feed conversion ratio (FCR) and mortality rate (MORT) of grower-finishing pigs. In total, 310 batches from 244 grower-finishing farms, consisting of 454 855 Pietrain sired pigs in six Spanish pig companies were used. Data collection consisted of a survey on management practices (season of placement, split-sex by pens, number of pig origins, water source in the farm, initial or final BW) and facilities (floor, feeder, ventilation or number of animals placed) during 2008 and 2009. Results indicated that batches of pigs placed between January and March had higher TFI (P=0.006), FCR (P=0.005) and MORT (P=0.03) than those placed between July and September. Moreover, batches of pigs placed between April and June had lower MORT (P=0.003) than those placed between January and March. Batches which had split-sex pens had lower TFI (P=0.001) and better FCR (P<0.001) than those with mixed-sex in pens; pigs fed with a single-space feeder with incorporated drinker also had the lowest TFI (P<0.001) and best FCR (P<0.001) in comparison to single and multi-space feeders without a drinker. Pigs placed in pens with <50% slatted floors presented an improvement in FCR (P<0.05) than pens with 50% or more slatted floors. Batches filled with pigs from multiple origins had higher MORT (P<0.001) than those from a single origin. Pigs housed in barns that performed manual ventilation control presented higher MORT (P<0.001) in comparison to automatic ventilation. The regression analysis also indicated that pigs which entered to grower-finisher facilities with higher initial BW had lower MORT (P<0.05) and finally pigs which were sent to slaughterhouse with a higher final BW presented higher TFI (P<0.001). The variables selected for each dependent variable explained 61.9%, 24.8% and 20.4% of the total variability for TFI, FCR and MORT, respectively. This study indicates that farms can increase growth performance and reduce mortality by improving farm facilities and/or modifying management practices.

Methane emissions, body composition, and rumen fermentation traits of beef heifers differing in residual feed intake.

This study examined the relationship of residual feed intake (RFI) and performance with methane emissions, rumen fermentation, and digestion in beef heifers. Individual DMI and growth performance were measured for 22 Simmental heifers (mean initial BW 449 kg, SD = 46.2 kg) offered grass silage ad libitum for 120 d. Ultrasonically scanned muscle and fat depth, BCS, muscularity score, skeletal measurements, blood variables, rumen fermentation (via stomach tube), and total tract digestibility (indigestible marker) were measured. Methane production was estimated using the sulfur hexafluoride tracer gas technique over two 5-d periods beginning on d 20 and 75 of the RFI measurement period. Phenotypic RFI was calculated as actual DMI minus expected DMI. The residuals of the regression of DMI on ADG and midtest metabolic body weight, using all heifers, were used to compute individual RFI coefficients. Heifers were ranked by RFI and assigned to low (efficient), medium, or high (inefficient) groupings. Overall ADG and DMI were 0.58 kg (SD = 0.18) and 7.40 kg (SD = 0.72), respectively. High-RFI heifers consumed 9 and 15% more (P < 0.05) than medium- and low-RFI groups, respectively. Body weight, growth, skeletal, and composition traits did not differ (P > 0.05) between low- and high-RFI groups. High-RFI heifers had higher concentrations of plasma glucose (6%) and urea (13%) and lower concentrations of plasma creatinine (9%) than low-RFI heifers (P < 0.05). Rumen pH and apparent in vivo digestibility did not differ (P > 0.05) between RFI groups, although acetate:propionate ratio was lowest (P = 0.07) for low-RFI (3.5) and highest for high-RFI (4.6) heifers. Methane production expressed as grams per day or grams per kilogram metabolic body weight was greater (P < 0.05) for high (297 g/d and 2.9 g/kg BW0.75) compared with low (260 g/d and 2.5 g/kg BW0.75) RFI heifers, with medium (275 g/d and 2.7 g/kg BW0.75) RFI heifers being intermediate. Regression analysis indicated that a 1 kg DM/d increase in RFI was associated with a 23 g/d increase (P = 0.09) in methane emissions. Results suggest that improved RFI will reduce methane emissions without affecting productivity of growing beef cattle.

Longitudinal study of the effect of rubber slat mats on locomotory ability, body, limb and claw lesions, and dirtiness of group housed sows.

This study evaluated the influence of floor type on sow welfare with particular focus on lameness, claw lesions (CL), and injuries. The study used 164 gilts housed in groups of 8 from AI to 110 d of pregnancy in pens with concrete (n = 84) slatted floor left uncovered or covered by 10-mm rubber slat mats (n = 80) through 2 parities. Lameness (0 = normal to 5 = severe), limb (0 = normal to 6 = severe) and body (0 = normal to 5 = severe) lesions, and manure on the body (MOB; score 0 to 2) were recorded at AI, 24 to 72 h postmixing, between 50 and 70 d of pregnancy, and 2 wk before farrowing. Claw lesions (score 0 = normal to 3 = severe) were recorded at AI and between 50 and 70 d of pregnancy. The dirtiness and wetness of the floors was scored weekly (score 0 = clean to 4 = >75% of the pen soiled/wet). Data from the first and second parities were analyzed separately. Sows were categorized as nonlame (score ≤ 1) or lame (score ≥ 2). Median (M(e)) scores were calculated for CL and body and limb lesions and were classified as less than or equal to the median or greater than the median lesion scores. Sows on rubber slat mats had a reduced risk of lameness during both parities (P < 0.01) compared with sows on concrete. They also had an increased risk of scores greater than the median for toe overgrowth (M(e) = 2 and M(e) = 3 in the first and second parity, respectively) and heel sole crack (HSC; M(e) = 3) during both parities (P < 0.01) and for cracks in the wall (CW; M(e) = 4) and white line damage (WL; M(e) = 4; P < 0.01) in the first and second parity, respectively. There was a reduced risk of lameness in sows with scores greater than the median for HSC (P = 0.05) in the first parity and WL (M(e) = 3; P < 0.01) and CW (M(e) = 3; P < 0.05) in the second parity. Wounds (M(e) = 3) and severe lesions (M(e) = 0) on the limbs with scores greater than the median were associated with an increased risk of lameness (P < 0.01) in the first and second parity, respectively. Sows on rubber slat mats had a reduced risk of scores greater than the median for swellings (M(e) = 4) and wounds (P < 0.01) during both parities. Pens with rubber slat mats were dirtier than uncovered pens (P < 0.01); however, there was no association between MOB and flooring type. There was also no association between body lesion score and flooring type. In this study, CL were not associated with an increased risk of lameness. Therefore, even though rubber slat mats were associated with an increased risk of CL, they improved the welfare of group housed sows by reducing the risk of lameness and limb lesions.

Reducing sperm concentration is critical to limiting the oxidative stress challenge in liquid bull semen.

Because of the short breeding season, the use of liquid bull semen is a viable option in seasonal grass-based dairy systems such as Ireland. Currently in Ireland, liquid bull semen contains approximately 5 million sperm per insemination dose and is used within 2.5d of collection. The hypothesis of this study was that reducing the sperm number per insemination dose would enable bull sperm to be stored for longer. Semen was collected at a commercial AI center and diluted to 1 (T1), 2 (T2), 3 (T3), 4 (T4), and 5 (T5) million sperm per 0.25-mL dose in caprogen diluent. On d 0.25 (6 h postcollection), 1, 2, 3, 4, and 5 postcollection, viability, oxidative stress, and mitochondrial activity were assessed using flow cytometry and the fluorescent probes propidium iodide, CM-H2DCFDA, and rhodamine 123, respectively. On the same days, glucose consumption, total antioxidant capacity, and progressive linear motility were assessed. We observed an effect of day and treatment on sperm cell viability, with the highest percentage live found in T 0005 and the lowest in T 0025 on all days. Oxidative stress in live sperm increased with duration of storage and was affected by treatment, being highest in T 0025 and lowest in T 0005 on all days (d 5: 56.4±2.76% and 28.8±1.22%, respectively; mean ± SEM). Both the total antioxidant capacity and percentage of live sperm positive for rhodamine 123 were unaffected by treatment. The concentration of glucose in caprogen declined with time and was lowest in T 0025 and highest in T 0005 on d 5. In conclusion, higher concentrations of sperm have detrimental effects on sperm cell viability and increase oxidative stress but have no effect on the mitochondrial activity of sperm.

The effect of the in vitro supplementation of exogenous long-chain fatty acids on bovine sperm cell function.

This study aimed to investigate the effects of long-chain fatty acids (α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), linoleic acid (LA), oleic acid (OA) and palmitic acid (PA)) at concentrations of 10-100 µM, on extended bull spermatozoa stored in vitro for up to 7 days. Progressive linear motion (PLM), viability (Experiments 1-3), ability to penetrate artificial mucus (Experiment 1), reactive oxygen species (ROS; Experiment 2) and superoxide production (Experiment 3) were assessed. Spermatozoa maintained the ability to penetrate artificial mucus up to Day 4, irrespective of treatment. In Experiments 2 and 3, DHA and EPA had detrimental effects on PLM and viability. PA preserved PLM and viability at levels greater than the control (P<0.05), whilst keeping ROS levels to a minimum, particularly on Days 1 and 3 (P<0.01) when ROS generation peaked in other treatments. In contrast, superoxide production peaked on Day 0 (Experiment 3) and declined thereafter with no significant effect of fatty acid. This study supports the notion that superoxide dominates on Day 0, whereas its breakdown products, hydrogen peroxide and the hydroxyl radical as assessed by CM-H2DCFDA, contribute to ROS generation on subsequent days.