Effects of prenatal and postnatal melatonin supplementation on overall performance, male reproductive performance, and testicular hemodynamics in beef cattle.

Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of prenatal and postnatal melatonin supplementation on overall calf performance and dam milking traits in relation to calves, molecular factors involved in growth and metabolism of calves, along with testicular physiology and fertility traits in subsequent bulls. On days 190, 220 and 250 of gestation, dams (N = 60) were administered either two subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves were blocked based on prenatal treatment and sex. Calves received either melatonin implants (posMEL) or none (posCON) on days 0, 30, and 60 of age. On day 60 of lactation, a subset of dams (N = 32) were selected based on age, weight, and calf sex for milk collection and analysis. At weaning, (day 210 postnatally) calf weight, morphometric data, liver samples, and loin samples were collected. At 12 mo of age, bull (N = 30) scrotal circumference, scrotal temperature, and testicular artery measurements were recorded. Milk yield and fat percent from dams tended to decrease in the preMEL group (P < 0.07) compared with preCON group. Prenatal melatonin administration did not affect (P = 0.95) calf birth weight and similarly calf weaning weight was unaffected (P < 0.10) by prenatal or postnatal melatonin supplementation. Blood analysis demonstrated that plasma concentrations of melatonin were not different (P = 0.12) in dams; however, an increase (P < 0.001) in plasma concentrations of melatonin was observed in posMEL vs. posCON calves. A tendency (P < 0.10) for decreased MYF5 and MYOD1 expression in loin muscle was observed in the posMEL calves. Prenatal and postnatal melatonin administration did not affect subsequent bull scrotal measurements or testicular hemodynamics (P ≥ 0.14). Administering supplemental melatonin via implants during the prenatal and postnatal phase did not alter performance characteristics in offspring. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature might have attributed to a lack of differences in melatonin levels during the prenatal phase. In the postnatal period, the level of developmental plasticity appears to be too low for melatonin properties to be effective.

Previous studies have examined maternal melatonin implants in fall calving Mississippi cattle during the third trimester of pregnancy. These studies have shown increased maternal uterine blood flow without any change in calf birth weight when supplemented with melatonin implants. However, calf weaning weights were increased in calves born to melatonin supplemented dams vs. their control counterparts. The objective of this study was to examine offspring performance following maternal melatonin supplementation (prenatal) and/or postnatal calf melatonin supplementation in spring calving Montana cattle. Calf performance and weight at weaning were not affected by maternal or postnatal melatonin supplementation. However, dam milk yield and fat percent were decreased in the melatonin supplemented dams. Maternal and postnatal melatonin supplementation did not affect bull measurements of reproductive performance. Interestingly, maternal concentrations of melatonin were not different between dam treatment groups; however, postnatal melatonin supplementation increased calf concentrations of melatonin. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature may attribute to a lack of differences in melatonin levels during the prenatal phase.

Next generation sequencing to define prokaryotic and fungal diversity in the bovine rumen.

A combination of Sanger and 454 sequences of small subunit rRNA loci were used to interrogate microbial diversity in the bovine rumen of 12 cows consuming a forage diet. Observed bacterial species richness, based on the V1-V3 region of the 16S rRNA gene, was between 1,903 to 2,432 species-level operational taxonomic units (OTUs) when 5,520 reads were sampled per animal. Eighty percent of species-level OTUs were dominated by members of the order Clostridiales, Bacteroidales, Erysipelotrichales and unclassified TM7. Abundance of Prevotella species varied widely among the 12 animals. Archaeal species richness, also based on 16S rRNA, was between 8 and 13 OTUs, representing 5 genera. The majority of archaeal OTUs (84%) found in this study were previously observed in public databases with only two new OTUs discovered. Observed rumen fungal species richness, based on the 18S rRNA gene, was between 21 and 40 OTUs with 98.4-99.9% of OTUs represented by more than one read, using Good's coverage. Examination of the fungal community identified numerous novel groups. Prevotella and Tannerella were overrepresented in the liquid fraction of the rumen while Butyrivibrio and Blautia were significantly overrepresented in the solid fraction of the rumen. No statistical difference was observed between the liquid and solid fractions in biodiversity of archaea and fungi. The survey of microbial communities and analysis of cross-domain correlations suggested there is a far greater extent of microbial diversity in the bovine rumen than previously appreciated, and that next generation sequencing technologies promise to reveal novel species, interactions and pathways that can be studied further in order to better understand how rumen microbial community structure and function affects ruminant feed efficiency, biofuel production, and environmental impact.

Effects of rumen-protected methionine on plasma amino acid concentrations during a period of weight loss for late gestating beef heifers.

This study determined changes in plasma amino acid concentration in late-gestating (beginning 58 ± 1.02 days prior to calving), primiparous, winter-grazing range heifers receiving wheat middling-based supplement without (CON) or with rumen-protected methionine (MET) to provide 15 g DL-MET each day. Plasma was collected on days -2 and 0 (start of MET supplementation just prior to individually receiving supplement at 0700 hours). Plasma was sampled again on days 40, 42 and 44 prior to supplementation at 0700 and 1100 hours (4 h after receiving daily supplement). Data were analyzed with cow as the experimental unit. Continuous variables were analyzed by the main effects of treatment, date, or time and their interaction when appropriate. Comparable BW (P = 0.32) and BCS (P = 0.83) over the 44-day metabolism trial were found between both CON- and MET-fed heifers. MET-supplemented heifers had greater (P < 0.01) plasma concentrations of methionine indicating that the rumen-protection technology successfully delivered methionine to the small intestine. Supplementation with rumen-protected DL-MET caused a significant supplement × date interaction for glutamine (P = 0.03), glycine (P = 0.02), methionine (P < 0.01), and serine (P = 0.05). In addition, trends for supplement × date interactions were detected for leucine (P = 0.07), threonine (P = 0.09), valine (P = 0.08), total amino acids (TAA; P = 0.08), non essential amino acids (NEAA; P = 0.08), branched chain amino acids (BCAA; P = 0.08), and glucogenic amino acids (GLUCO; P = 0.08). These results suggest that the BCAA (leucine and valine) were utilized more efficiently with MET supplemented heifers compared to CON supplemented heifers. Plasma AA concentrations for glutamic acid (P < 0.01), histidine (P = 0.01), tyrosine (P < 0.01), and EAA (P < 0.01), all decreased throughout the study. These results further confirm methionine is a limiting amino acid in forage fed late-gestating heifers and further suggests the limitation when grazing dormant range forages as shown by improved utilization of other plasma amino acids when supplemental methionine was provided.

Effect of reduced heifer nutrition during in utero and post-weaning development on glucose and acetate kinetics.

Energetic efficiency was evaluated in composite bred heifers born from dams receiving 1·8 or 1·2 kg/d winter supplementation for approximately 80 d before parturition. Heifers were then developed post-weaning and randomly assigned to heifer development treatments of either control (100 %; ad libitum; n 8/year) or restricted (80 %; fed 80 % of supplementation fed to controls adjusted to a common body weight: n 8/year) in a 2-year study. A glucose tolerance test (GTT) and acetate irreversible loss test (AILT) were administered to heifers at the termination of a 140 d development period when the heifers were approximately 403 d of age and consumed a silage-based diet, and again at 940 d of age when pregnant with their second calf and grazing dormant forage. No differences were measured (P>0·08) for dam winter nutrition or heifer development treatment for baseline serum metabolites or measures in either the GTT or the AILT. However, changes in baseline serum concentrations (P>0·05) were different between metabolic challenges, which occurred at different stages of development. No difference in acetate disappearance (P = 0·18) and half-life (P = 0·66) was measured between the two metabolic challenges. A trend for glucose half-life to be shorter in heifers born from dams receiving in utero winter treatments that supplied 1·2 kg/d of winter supplementation was observed (P = 0·083). Heifers developed with lower total DM intake during a 140 d development period had similar glucose and acetate incorporation rates as ad libitum-fed heifers when evaluated at two different production stages.

Effects of Euphorbia esula L. (leafy spurge) on cattle and sheep in vitro fermentation and gas production.

BACKGROUND: Euphorbia esula L. (leafy spurge) is indigenous to Eurasia and has been known to cause grazing aversion in ruminant species. As a result, E. esula encroachment has negatively impacted rangelands in the Northern Great Plains and Intermountain West of the USA, as well as southern Canada. Our objectives were to evaluate the effect of increasing concentrations of E. esula on in vitro dry matter digestibility (DMD) and gas production. Two ruminally-cannulated cows and ewes were used as rumen inoculum donors. To accomplish objectives, two studies were conducted. In study 1, animals were fed exclusively a barley hay (12% crude protein (CP), 55.4% neutral detergent fiber (NDF), DM basis) diet; whereas in study 2, animals were fed a diet of 15% E. esula (21.9% CP, 48% NDF, DM basis) and 85% barley hay based on previous day intake. RESULTS: The 24 and 48 h in vitro and 96 h gas production indicate that, regardless of inoculum source or substrate fermented, DMD was not influenced. Differences, however, were consistently observed across studies for NDF disappearance. CONCLUSION: Regardless of inoculum source NDF disappearance was greater when substrate being fermented contained 0%, 80%, or 100% E. esula.