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Artificially rearing lambs on milk replacer impacts development of the ruminal microbiome. The objective was to evaluate the extent to which pre-weaning management influences the ruminal microbiome of lambs during finishing. A finishing study was conducted using 32 Polypay conventionally-raised (CR; n = 10 rams, 6 ewes) or artificially raised (AR; n = 10 rams, 6 ewes) lambs weaned at 56 d of age. Following weaning, lambs were adapted to a HC (85:15 concentrate:forage) diet for 35 d. Lambs were then blocked by sex and body weight and randomly assigned to either continue receiving HC or abruptly transition to a HF (50:50 concentrate:forage) diet. Individually-housed lambs were fed ad libitum through a target slaughter weight (rams: 59.0; ewes: 54.4 kg). Rumen fluid samples were collected via oral intubation on d 0, 14, 28, and when lambs reached slaughter weight. Analysis of 16S rRNA gene sequences was conducted in QIIME 2 (v.2023.2). Taxonomy was assigned with SILVA (SSU 138). Diversity was analyzed by PERMANOVA. Random forest classification was applied to determine if pre-weaning management and diet could be predicted using microbial composition. Alpha diversity did not differ in CR vs. AR lambs at the initial sampling (P > 0.22), but species richness was greater in HR lambs regardless of pre-weaning management from d 14 through slaughter (P < 0.01). Beta diversity did differ between CR and AR at the initial sampling (P ≤ 0.02). The influence of pre-weaning management was still present in weighted UniFrac distances by d 14 (P = 0.09), but effects of pre-weaning management were no longer apparent from d 28 through slaughter (P ≥ 0.28). Similarly random forest modeling was able to predict pre-weaning management in initial samples (accuracy: 0.75 ± 0.15). Accuracies decreased over the study period (d 14: 0.58 ± 0.07; d 28: 0.50 ± 0.15; slaughter: 0.45 ± 0.07), whereas model performance improved for prediction of diet (d 14: 0.83 ± 0.15; d 28: 0.87 ± 0.12; slaughter: 0.97 ± 0.07). The most important feature in predicting pre-weaning management at initial sampling belonged to Ruminococcus, and 9 ASV assigned to Prevotella were among the most important features in the model. Five features were present in the top 20 most important features for both the initial and finishing models, and included ASV assigned to Streptococcus, Lactobacillus, and Bifidobacterium. These results illustrated continued impacts of early-life management on ruminal microbiome composition at the beginning of the finishing period, even though CR and AR lambs had been adapted to the same diet for more than 1 mo. While pre-weaning effects were muted over the course of finishing as diet became the predominant factor, the influence of early-life management was still detectable by the end of the finishing period.

Pre-weaning strategies, such as artificially raising on milk replacer, can impact lamb quality. Limited studies have examined the influence of artificial raising on color attributes of lamb. The aim of this study was to evaluate how artificially raising on milk replacer affects the color and oxidative stability of longissimus lumborum (LL) muscle from ram lambs finished on a high-concentrate diet. For a 60-day pre-weaning period, Polypay ram lambs were reared either conventionally with ewes (CR; n = 5) or artificially on milk replacer (MR; n = 5). After 60 days, the lambs were finished on a high concentrate diet (85:15 concentrate: forage) containing 78% cracked corn and 22% pre-mixed protein pellet as the concentrate source as well as 15% orchard grass pellet as the forage source. The lambs were fed ad libitum high-concentrate diet until the target body weight of 59 kg. The lambs were harvested, and the LL muscles from both sides of the carcasses (24 h post-mortem) were fabricated into 2.5-cm thick chops. Carcass characteristics were recorded during harvesting and fabricating. The chops were placed on polystyrene trays, overwrapped with oxygen-permeable polyvinyl chloride film, and stored at 2°C in the darkness for 0, 3, and 6 d. Instrumental color, color stability (R630/580), pH, lipid oxidation, and myoglobin reducing activity of the chops were evaluated on the storage days. A split-plot design was employed to analyze the data. Pre-weaning management was the main plot, while the storage time was considered as the sub-plot. The LL muscles from each lamb carcass were considered as the experimental unit, whereas the sub-plot experimental units were the chops allocated for 0, 3, or 6 d storage. The data were analyzed using the PROC GLIMMIX. The least square means were separated utilizing the PDIFF option and adjusted with the Tukey-Kramer method. The differences among means were detected at a 5% level. There was no effect (P > 0.05) of pre-weaning management on carcass characteristics, surface redness (a* value), lightness (L* value), yellowness (b* value), color stability (R630/580), pH, or metmyoglobin reducing activity of LL chops. Color stability (R630/580) and metmyoglobin reducing activity declined (P < 0.05) during storage in both CR and MR chops. In contrast, lipid oxidation, lightness (L* value), yellowness (b* value), and hue value of the chops increased (P < 0.05) in both treatments during storage. Artificial raising on milk replacer for 60 d pre-weaning period did not influence color and oxidative stability of lambs finished on a high-concentrate diet. Carcass characteristics, color stability, and lipid oxidation were comparable in lambs raised through conventional method and those raised artificially on milk-replacer. These findings indicate that milk-replacer could be employed as a practical approach for artificial rearing in lamb production.

Red clover (RC) contains bioactive isoflavones. Supplementing RC as a functional feed (as little as 7.5% of the total diet) has been shown to alter ruminal fermentation and improve feed efficiency in ram lambs fed high-concentrate finishing diets. The objectives of this study were to determine if reduced RC inclusion will produce similar rumen microbiological effects. It was hypothesized that RC supplementation below 7.5% RC will alter rumen microbial community composition during the finishing period. Sixteen individually housed Polypay ram lambs (age; 134 ± 2.5 d; initial body weight: 31 ± 0.53 kg) were used in a complete block design and fed one of four isocaloric and isonitrogenous diets (85:15 concentrate:roughage ratio; n = 4 rams diet1): a control diet in which the roughage component (15.0% wt/wt of total diet) consisted of orchardgrass hay, 2.5%-RC (roughage: 2.5% RC; 12.5% orchardgrass wt/wt), 5.0%-RC (roughage: 5.0% RC; 10% orchardgrass wt/wt), and 7.5%-RC (roughage: 7.5% RC; 7.5% orchardgrass wt/wt). Rumen fluid was collected via oral intubation at 0, 2, 4, 6, and 8 h post-feeding at the end of the adaptation period (14 d; all rams on control diet) and at 21-d intervals during the trial. Rumen functional bacterial guilds, including hyper-ammonia-producing bacteria (HAB), amylolytic, lactate-utilizing (LU), and cellulolytic bacteria were enumerated via serial dilution at 4 h post-feeding. Data were analyzed using PROC MIXED with repeated measures in SAS (v.9.4, SAS inst. Inc., Cary, NC). There were no differences between diets on d 0 for any variable (P > 0.05). At d 21, all RC-containing diets exhibited a 10- to 100-fold reduction in ruminal HAB compared with the control (P < 0.05). While suppression of HAB was no longer apparent by d 42 in 2.5%-RC, HAB had decreased 100-fold (109to 107) in lambs fed the 5.0%-RC and 7.5%-RC diets (P < 0.01). No differences in amylolytic bacteria were detected on d 21 (P > 0.05), but were 10-fold less in all diets containing RC by d 42 in comparison with control (109to 108; P = 0.08). In contrast, LU increased by d 21 and were 100-fold greater (106to 108) by d 42 when compared with the control for all levels of RC supplementation (P < 0.05). Cellulolytic bacteria also increased across the study period in all lambs fed RC diets, with 100-fold greater cellulolytics (106to 108) by d 42 (P < 0.05). Consistent with the hypothesis, supplementing RC at levels as low as 2.5% wt/wt of the total diet decreased protein-wasting HAB and amylolytic bacteria while coincidingly increasing LU and cellulolytic bacteria in the rumen. These results indicate that adding red clover to finishing diets has the potential to increase lamb growth and feed efficiency through a functional feed action.

Ewes transitioning from late gestation to early lactation face a number of challenges including physiological stress, dietary changes, and metabolic adaptations, particularly when bearing and rearing multiple offspring. Furthermore, rumen microbial composition and function has been correlated with milk production and nutrient density in transitioning dairy cows. However, limited research has evaluated the rumen microbial community of ewes during early lactation. The objective of this study was to conduct a functional microbiological survey of the ewe rumen from parturition to weaning. We hypothesized that ewes would experience fermentative disturbances post-parturition and that the rumen microbiota, and consequently, circulating metabolites, would recover over time. Nine multiparous Polypay ewes bearing triplets were fed a lactation diet consisting of alfalfa hay and concentrate mix to meet protein and energy requirements. One lamb of each triplet set was randomly selected and placed on milk replacer 24 h after birth. The two lambs remaining on the ewe were weaned at 56 d of age. Blood and rumen samples from ewes were collected via jugular venipuncture and oral intubation, respectively, at 2, 7, and 15 d of lactation in addition to at the time of weaning. Rumen bacterial functional guilds were enumerated via serial dilution. Ruminal short-chain fatty acids (SCFA) were quantified via HPLC and serum metabolites by LC-MS. All data were analyzed using PROC Mixed with repeated measures in SAS (v. 9.4, SAS Inst. Inc., Cary, NC). Total starch-utilizing bacteria remained steady during early lactation but increased 100-fold by weaning (P = 0.03). In contrast, the starch-utilizing guild sub-population lactobacilli increased 10-fold by d 15 of lactation (P < 0.01) and remained constant through weaning (P > 0.05). No differences were found in the viable number of rumen cellulolytic bacteria (P = 0.37) throughout the study. Ruminal propionate concentrations increased 35% (P = 0.04) from d 2 to weaning and serum propionate (36.8 ± 4.42 µM; P = 0.08) and glucose (59.8 ± 2.97 mg dL-1; P < 0.01) peaked on d 15 of lactation. While ruminal acetate did not fluctuate in early lactation, it increased 58% by weaning (P < 0.01) leading to an 88% increase in serum acetate (P < 0.01). Ruminal butyrate increased 49% by d 15 (P = 0.01) and this was reflected in a 7-fold increase in serum butyrate (P = 0.02). However, serum β-hydroxybutyrate did not differ from parturition through weaning (P = 0.51). Results of this experiment demonstrate that rumen bacterial functional guilds, as well as rumen and serum metabolites, were lowest two days post-parturition and increased over the course of lactation. This may suggest that ruminal fermentation is suppressed post-parturition, which could have implications for early lactation management strategies of triplet-bearing ewes.

Red clover produces isoflavones, including biochanin A, which have been shown to have microbiological effects on the rumen while also promoting growth in beef cattle. The objective was to determine if supplementation of biochanin A via red clover hay would produce similar effects on the rumen microbiota and improve growth performance of lambs. Twenty-four individually-housed Polypay ram lambs (initial age: 114 ± 1 d; initial weight: 38.1 ± 0.59 kg) were randomly assigned to one of three experimental diets (85:15 concentrate:roughage ratio; N= 8 rams/treatment): CON—control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC—red clover hay substituted for half (7.5%, w/w, of the total diet) of the roughage component; and 15-RC—the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. Feed intake and weight gain were measured at 14-d intervals for the duration of the 56-d trial, and rumen microbiological measures were assessed on days 0, 28, and 56. Red clover supplementation impacted growth performance of ram lambs. Average daily gains (ADG) were greater in ram lambs supplemented with red clover hay (7.5-RC and 15-RC) than for those fed the CON diet (P< 0.05). Conversely, dry matter intake (DMI) was lower in 7.5-RC and 15-RC than for CON lambs (P= 0.03). Differences in ADG and DMI resulted in greater feed efficiency in ram lambs supplemented with red clover hay (both 7.5-RC and 15-RC) compared to CON (P< 0.01). Rumen microbiota were also altered by red clover supplementation. The total viable number of hyper-ammonia-producing bacteria in 7.5-RC and 15-RC decreased over the course of the experiment and were lower than CON by day 28 (P≤ 0.04). Amylolytic bacteria were also lower in 15-RC than in CON (P= 0.03), with a trend for lower amylolytic bacteria in 7.5-RC (P= 0.08). In contrast, there was tendency for greater cellulolytic bacteria in red clover supplemented lambs than in CON (P= 0.06). Red clover supplementation also increased fiber utilization, with greater ex vivo dry matter digestibility of hay for both 7.5-RC and 15-RC compared to CON by day 28 (P< 0.03). Results of this study indicate that low levels of red clover hay can elicit production benefits in high-concentrate lamb finishing systems through alteration of the rumen microbiota.Supplementation of low levels of red clover hay, rich in the isoflavone biochanin A, altered the numbers of rumen bacteria functional groups, changed ruminal fermentation, and promoted growth performance in high-concentrate lamb finishing. Red clover may serve as a functional feed with production benefits in addition to its traditional use as a forage feedstuff.Red clover is rich in the bioactive isoflavone, biochanin A. The goal was to evaluate the impacts of biochanin A supplementation via red clover hay on growth performance of ram lambs as well as the rumen microbiota and fermentation. Low levels of red clover hay inclusion (7.5% and 15.0%, w/w, of the total diet) in high-concentrate finishing diets improved feed efficiency of ram lambs, promoting weight gain while decreasing feed intake. Red clover hay supplementation suppressed ruminal protein-wasting, peptide- and amino-acid degrading and starch-utilizing bacteria compared to control diets without isoflavones. Red clover hay also promoted fiber degrading bacteria and fiber utilization. Lamb growth and microbiological effects of red clover were consistent regardless of supplementation level in the diet. Results of this study indicate that low levels of red clover hay can produce production benefits in lamb finishing systems and demonstrated the efficacy of red clover as a functional feed, or feed with biological activities, in the context of its traditional use as a forage feedstuff.