Relationships among intramammary health, udder and teat characteristics, and productivity of extensively managed ewes

Mastitis is an economically important disease and its subclinical state is difficult to diagnose, which makes mitigation more challenging. The objectives of this study were to screen clinically healthy ewes in order to 1) identify cultivable microbial species in milk, 2) evaluate somatic cell count (SCC) thresholds associated with intramammary infection, and 3) estimate relationships between udder and teat morphometric traits, SCC, and ewe productivity. Milk was collected from two flocks in early (\u3c5 \u3ed) and peak (30 to 45 d) lactation to quantify SCC (n = 530) and numerate cultivable microbial species by culture-based isolation followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS; n = 243) identification. Within flock and lactation stage, 11% to 74% (mean = 36%) of samples were culture positive. More than 50 unique identifications were classified by MALDI-TOF MS analysis, and Bacillus licheniformis (18% to 27%), Micrococcus flavus (25%), Bacillus amyloliquefaciens (7% to 18%), and Staphylococcus epidermidis (26%) were among the most common within flock and across lactation stage. Optimum SCC thresholds to identify culture-positive samples ranged from 175 × 103 to 1,675 × 103 cells/mL. Ewe productivity was assessed as total 120-d adjusted litter weight (LW120) and analyzed within flock with breed, parity, year, and the linear covariate of log10 SCC (LSCC) at early or peak lactation. Although dependent on lactation stage and year, each 1-unit increase in LSCC (e.g., an increase in SCC from 100 × 103 to 1,000 × 103 cells/mL) was predicted to decrease LW120 between 9.5 and 16.1 kg when significant. Udder and teat traits included udder circumference, teat length, teat placement, and degree of separation of the udder halves. Correlations between traits were generally low to moderate within and across lactation stage and most were not consistently predictive of ewe LSCC. Overall, the frequencies of bacteria-positive milk samples indicated that subclinical mastitis (SCM) is common in these flocks and can impact ewe productivity. Therefore, future research is warranted to investigate pathways and timing of microbial invasion, genomic regions associated with susceptibility, and husbandry to mitigate the impact of SCM in extensively managed ewes

Impacts of Heifer Post-Weaning Intake Classification on Performance Measurements of Lactating and Non-Lactating Two-, Five-, and Eight-Year-Old Angus Beef Females

Heifer post-weaning intake classification was utilized to evaluate subsequent intake and performance measurements of 2-, 5-, and 8-year-old lactating and non-lactating Angus females. For both studies, heifers were categorized based on voluntary feed intake (expressed as g/kg BW) as either low (<−0.50 SD from the mean), average (±0.50 SD from the mean), or high (>0.50 SD from the mean) within one year. Intake and production data of pregnant, non-lactating (n = 59; Study 1) and lactating, non-pregnant (n = 54; Study 2) females were evaluated. Heifer post-weaning voluntary feed intake was calculated over 80 test days post-weaning using GrowSafe feed intake units. Cow body-weight (BW) for non-lactating cows showed a tendency for age × intake interaction (p = 0.10), with older cows weighing more than younger cows. Milk production expressed as kilograms and g/kg BW of the cow had an age × intake (p < 0.001) effect. Two-year-old cows with low- and average-intake classifications had greater milk production (p < 0.001) and milk produced expressed as g/kg BW (p < 0.001) than 2-year-old cows with high-intake classifications. Additionally, 5-year-old cows with average and high-intake classifications had greater milk production (p < 0.001) and g/kg BW (p < 0.001) compared to 5-year-old cows classified as low-intake. In summary, heifer post-weaning intake classification had minor impacts on performance measurements in the three age classes of beef females at two different production levels

Loci associated with conception rate in crossbred beef heifers.

The inability of beef cattle to maintain full term pregnancies has become an economic concern for the beef industry. Herd management and nutritional improvements have alleviated environmental impacts on embryonic and fetal loss, yet additional gains can be made through genomic selection. The objectives of this study were to identify loci and gene-sets in crossbred beef heifers associated with the number of services required to become pregnant (TBRD) and heifer conception rate at first service (HCR1). Heifers (n = 709) from a commercial beef operation underwent one round of artificial insemination, before exposure to bulls for natural service for 50 days. Pregnancy and time of conception was determined by ultrasound 35 days after the breeding season. Heifers were genotyped using the GeneSeek (Lincoln, NE) Bovine GGP50K BeadChip prior to genome-wide association analyses (GWAA) conducted using an EIGENSTRAT-like model to identify loci associated (P < 1 × 10-5) with TBRD and HCR1. One locus was associated (P = 8.97 × 10-6) with TBRD on BTA19 and included the positional candidate gene ASIC2, which is differentially expressed in the endometrium of fertility classified heifers, and the positional candidate gene, SPACA3. Gene-set enrichment analyses using SNP (GSEA-SNP) data, was performed and identified one gene-set, oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen as enriched (NES = 3.15) with TBRD and contained nine leading edge genes that contributed to the enrichment of the gene set. The enriched gene-set is involved in catalyzing oxidation-reduction reactions, which have been associated with oxidative stressors impacting pregnancy success. No loci were associated nor gene-sets enriched with HCR1. Identification of loci, positional candidate genes, gene-sets and leading edge genes enriched for fertility facilitate genomic selection that allows producers to select for reproductively superior cattle, reduce costs associated with infertility, and increase percent calf crop

The Influence of Environmental Conditions on Intake Behavior and Activity by Feedlot Steers Fed Corn or Barley-Based Diets

This study evaluated the influence of diet and environmental conditions on intake behavior and activity of feedlot steers. Feedlot rations used were comprised of a main concentrate: (1) corn or (2) barley. A GrowSafe system measured individual animal intake and behavior and HOBO accelerometers measured steer standing time. An Onset weather station collected on site weather data. Steer daily intake displayed a diet by temperature class interaction (p ≤ 0.05). Relative temperature change had no effect on variation in intake (p = 0.60); however, diet influenced variation of intake (p &lt; 0.01), where corn-fed steers had a greater coefficient of variation (CV) than barley-fed steers (21.89 ± 1.46 vs. 18.72 ± 1.46%). Time spent eating (min d−1) and eating rate (g min−1) both displayed a diet by temperature class interaction (p ≤ 0.05). Diet did not affect steer lying activity (p ≥ 0.12), however, time spent lying (min d−1) and frequency of lying bouts (bouts d−1) increased on relatively cold days while the duration of lying bouts (min bout−1; p &lt; 0.01) decreased. Short-term environmental temperature changes interacted with diet influencing feedlot beef cattle intake behavior; however, they did not interact with basal diet in respect to steer activity

Diurnal Ruminal pH and Temperature Patterns of Steers Fed Corn or Barley-Based Finishing Diets

This study evaluated the effects of corn or barley finishing diets on ruminal pH and temperature and their relationship to feed intake events using continuous reticulorumen monitoring of feedlot steers. Average daily ruminal pH and temperature were not impacted (p ≥ 0.17) by diet. However, diet did affect daily variation of ruminal pH and temperature (p &lt; 0.01). Average hourly ruminal pH displayed a diet by hour post-feeding interaction (p &lt; 0.01), where barley-fed steers had greater (p &lt; 0.01) ruminal pH than corn-fed steers at 0, 1, 18, 19, 20, 21, 22 and 23 h post feeding, but had lower (p ≤ 0.05) ruminal pH than corn-fed steers at 6, 7, and 8 h post-feeding. Variation in ruminal pH hour post-feeding also displayed a diet by hour post-feeding interaction (p &lt; 0.01), where barley-fed steers had greater (p ≤ 0.03) variation in ruminal pH at hours 1–17 post-feeding but did not differ (p ≥ 0.16) at 0, 18, 19, 20, 21, 22 and 23 h post-feeding. Additionally, average hourly ruminal temperature exhibited a diet by hour post-feeding interaction (p &lt; 0.01). In summary, basal grain interacted with time post-feeding influencing ruminal pH and temperature in feedlot steers