Effects of diets differing in dietary cation-anion difference and calcium concentration on calcium homeostasis in neutered male sheep

Impact of Varying Dietary Calcium Contents on the Gut Metabolomics of Yunnan Semi-Fine Wool Sheep (Ovis aries)

Yunnan semi-fine wool (YSFW) is a recently developed dual-purpose (meat and wool) sheep breed mainly found in Yunnan Province, China. Moreover, dietary calcium is essential for animal health and productivity. The current experiment aimed to investigate the impact of dietary calcium on sheep gut metabolite profile. For this, thirty YSFW rams (male, age = 10 months, and body weight = 40.37 ± 0.49 kg) were randomized into three groups (n = 10 rams/group), followed by a completely randomized design, and the groups were allotted to one of three dietary calcium levels (Q_1 = 0.50%, Q_3 = 0.73%, and Q_5 = 0.98% on a dry basis). The rams were fed ad libitum by feeding twice a day (at 08:00 and 17:00 h/day) throughout the experimental period (44 day). On the 21st day of the experiment, fecal samples were collected from 27 rams (9/group) and untargeted metabolite profiling was performed by using ultra-performance liquid chromatography. The PCA plot showed that the Q_5 group metabolites were clustered more tightly than for Q_1 and Q_3, respectively. The tightly clustering molecules were mainly alkaloids and their derivatives, benzenoids, lignans and related compounds, lipids, nucleotides, organic acids, and nitrogenous-based derivatives. According to the Kyoto Encyclopedia of Genes and Genomes pathway analysis, these molecules potentially contribute to metabolic pathways, biosynthesis of secondary metabolites, proteinaceous compounds, and the metabolism of the protein derivatives, particularly amino acids. The PLS-DA plots revealed a significant difference between the Q_1, Q_3, and Q_5 groups, suggesting that Q_5 had a clear separation across the groups. Based on the metabolomic analysis, feeding different levels of dietary calcium significantly changed the metabolomic profile of YSFW rams, which primarily entails metabolic pathways such as energy, protein, and lipid metabolism.

Calcium Requirement of Yunnan Semi-fine Wool Rams (Ovis aries) Based on Growth Performance, Calcium Utilization, and Selected Serum Biochemical Indexes

Calcium (Ca) is required for the growth and development of sheep, but the requirement of Yunnan semi-fine wool (YSW) rams remains uncovered. The current study aims to estimate the Ca requirement of growing YSW rams based on their growth performance, Ca utilization, and serum biochemical indexes. Forty-five YSW rams (10-month-olds) were randomly allocated to five dietary treatments with varying Ca levels of 0.50% (D1), 0.68% (D2), 0.73% (D3), 0.89% (D4), and 0.98% (D5). A higher value for average daily gain and a lower value for the feed conversion ratio were observed in the D3 group compared to the D5 group (p < 0.05). The dry matter intake amount changed quadratically with the increased Ca levels (p < 0.05). The levels of Ca intake, fecal Ca, and excreted Ca were significantly higher in the D5 group than those in the D1 group (p < 0.05). The apparent Ca digestibility rate and the Ca retention rate were significantly higher in the D4 group than in the D1 group (p < 0.05). The serum Ca concentration increased linearly with the incremental levels of dietary Ca (p < 0.05). The activity of alkaline phosphatase was significantly higher in the D1 group than in the D2 group (p < 0.05). The serum levels of hydroxyproline, osteocalcin, and calcitonin decreased from the D1 group to the D2 group, and then significantly ascended (p < 0.05) with the dietary Ca levels from the D3 group to the D5 group. The serum parathyroid hormone content was elevated from the D1 group to the D3 group and then decreased from the D4 group to the D5 group. After calculation, the daily net Ca requirement for the maintenance of YSW rams was 0.073 g/kg of BW0.75, and the daily total Ca requirement was 0.676 g/kg of BW0.75. To optimize the growth performance and the Ca utilization of YSW rams, the recommended dietary Ca level ranges from 0.73% to 0.89% based on this study.

Effects of feeding a negative dietary cation and anion difference diet to twin-bearing Merino ewes in late gestation on parturition outcomes

In Australia, dystocia is responsible for 53% of lamb mortalities, and calcium deficiencies may be a contributing factor. A negative dietary cation-anion difference (DCAD) diet can increase calcium concentrations in sheep. Therefore, this study aimed to investigate the effects of a negative DCAD diet on metabolic state, mineral status, and parturition duration in ewes compared with those fed a positive DCAD diet. At approximately day 130 of gestation (dG), 71 twin-bearing ewes were placed in the following treatment groups; ewes receiving a positive DCAD TMR (total mixed ration; DCAD of total diet = 281.8 mEq/kg DM; n = 35) and twin-bearing ewes receiving a negative DCAD TMR (DCAD of total diet = -89.0 mEq/kg DM; n = 36). Urine and blood were sampled on dG 130, 140, and 145, and blood was also sampled at the onset of parturition and 4 h postpartum. Urine was analyzed for pH and blood was analyzed for metabolites, mineral concentration, and acid-base balance. Lambs' liveweight, rectal temperature, blood glucose and lactate, and body morphology were measured. Serum phosphate concentrations at dG 145 were significantly lower for negative DCAD ewes compared with positive DCAD ewes (1.9 ± 0.1 vs. 2.1 ± 0.1 mmol/L, P = 0.047). Ionized calcium (P = 0.09) and serum magnesium (P = 0.09) prepartum were marginally greater in the negative DCAD ewes (1.35 ± 0.06 and 1.06 ± 0.03 mmol/L, respectively) compared with the positive DCAD ewes (1.18 ± 0.08 and 0.98 ± 0.04 mmol/L, respectively). Urine pH was lower in the negative DCAD ewes compared with positive DCAD ewes at both dG 140 (7.38 ± 0.17 vs. and 8.10 ± 0.19. P = 0.01) and dG 145 (and 7.20 ± 0.19 vs. 8.25. P < 0.01). The birth interval between the first the second-born lamb was shorter in the negative DCAD ewes compared with the positive DCAD ewes (P = 0.02), but no differences in lamb survival or lamb viability (P > 0.05) were seen. The negative DCAD diet reduced parturition duration, most likely due to the marginally greater ionized calcium and magnesium concentrations. Despite this improvement, the negative DCAD ewes did not reach urinary acidification, indicating that the marginally significant greater ionized calcium and serum magnesium concentrations were due to the magnesium in the diets and not metabolic acidosis. Further research testing a negative DCAD diet that can achieve the target urine pH is required to determine whether this diet can decrease parturition duration and improve lamb viability.

Negative dietary cation and anion difference supplementation of twin-bearing Merino ewes grazing pasture in late gestation did not affect lamb growth or survival

Each year in Australia, 53% of lamb mortalities are attributed to dystocia, with subclinical maternal calcium deficiencies likely contributing to dystocia rates. A negative dietary cation and anion difference (DCAD) diet has increased circulating calcium in sheep. Therefore, this study aimed to investigate the effects of supplementing twin-bearing, grazing ewes with a negative DCAD partial mixed ration (PMR) during late gestation on ewe calcium and magnesium concentrations and subsequent lamb growth and survival. On day 120 of gestation (dG), blood samples were collected from 115 twin-bearing Merino ewes and analyzed for glucose, ketone bodies, pH, ionized calcium, and serum calcium and magnesium. On dG 130, ewes were moved into lambing paddocks and placed in the following 2 treatment groups; ewes receiving a positive DCAD PMR (DCAD = 287 mEq/kg DM; n = 58) and ewes receiving a negative DCAD PMR (DCAD = -125 mEq/kg DM; n = 57) fed as a PMR. On dG 140, a blood and urine sample were collected. The urine was tested for pH. Pasture samples were taken on dG 133 and 149 and tested for DCAD and mineral content. When a lamb was 6 to 18 h old, survival, vigor score, liveweight (LW), rectal temperature, blood glucose, and body morphology were recorded. At 10 d of age, lamb LW and survival were recorded and a milk sample was collected from ewes. At 44 d of age, lamb LW and survival were recorded. The DCAD of the pastures across the 6 paddocks ranged from 598 to 893 mEq/kg DM. There were no differences in lamb survival, weight, or viability at any timepoint (P > 0.05). There were no differences in mineral status, metabolic state, or acid-base balance between the positive and negative DCAD-supplemented ewes (P > 0.05) during supplementation (dG 140). Supplementing a negative DCAD diet to ewes grazing pasture during late gestation did not improve lamb survival. The blood and urine pH of the negative DCAD-supplemented ewes indicated a mild metabolic acidosis was not reached due to the high DCAD of the pastures. Further research needs to take careful consideration of the DCAD of pasture when designing a negative DCAD supplement in order for it to be effective.