Nutritional and reproductive management strategies to enhance sheep production efficiency

Abstract

Two studies were conducted at the Kansas State University Sheep and Meat Goat Center to evaluate nutritional and reproductive management strategies to increase sheep production efficiency. Experiment 1 assessed the effects of supplementing a liquid direct-fed microbial (DFM; RSG Prime by BIO S.I.) on growth performance, fecal consistency, blood parameters, and fecal microbial populations in feedlot lambs consuming a high-concentrate diet. Seventy-two Dorper × Katahdin lambs (60 d of age; 26.73 ± 0.35 kg BW) were assigned to either a control (CON; no DFM) or DFM treatment (15 mL/head daily) over a 63-day period. Growth performance variables, including average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F), were not affected (P > 0.05) by DFM supplementation. Fecal scores improved over time (P < 0.0001) but were not influenced by treatment. While no treatment × day interactions were observed for blood parameters, serum calcium tended to be lower (P = 0.06) in DFM-supplemented lambs, and several metabolites shifted over time (P ≤ 0.03). Additionally, DFM supplementation altered the relative abundance of specific fecal microbial taxa (P ≤ 0.05), with notable treatment × day interactions observed in select genera. Overall, DFM supplementation did not impact growth performance but influenced serum chemistry and fecal microbial composition. Experiment 2 evaluated the effects of estrous synchronization protocols using Controlled Internal Drug Release (CIDR) devices of differing durations on reproductive performance in ewes. Fifty-eight Polypay-influenced ewes were assigned to either a 5-day or 14-day CIDR protocol. A subset (n = 10/treatment) of ewes from each treatment were monitored via transrectal ultrasonography to assess follicular dynamics. The 5-day group had larger follicle diameters at CIDR insertion and 7 days post-removal, while the 14-day group had a higher follicle count at the protocol end. Marking by the ram was initiated in the 14-day group approximately 12 hours earlier than the 5-day group, however there was more variation in time to return to estrus in the group of ewes. Pregnancy outcomes differed, with the 5-day group showing more ewes with single fetuses, and the 14-day group producing more twins via ultrasound on d 75. Total lamb production was similar between treatments (34 vs. 36 lambs). A larger number of ewes remained open in the 14-day group (10 vs. 6 ewes). Limitations of transrectal ultrasonography and ram effect on breeding data make it difficult to establish differences in treatment. These limitations highlight the need for refined imaging technique to establish follicular changes in different CIDR estrous synchronization protocols in future studies. Collectively, these studies demonstrate nutritional and reproductive interventions may not always influence primary performance outcomes. However, these findings may indicate potential changes in sheep health and growth performance that warrants further investigation.