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Two experiments were conducted to evaluate the effects of calcium (Ca) levels in weanling pigs (Landrace × Yorkshire × Duroc). In experiment 1, one hundred and eighty weanling pigs were randomly allotted to one of the three treatments. The treatments were low (Ca 0.60% in phase 1 and 0.50% in phase 2), standard (Ca 0.72% in phase 1 and 0.66% in phase 2), and high (Ca 0.84% in phase 1 and 0.72% in phase 2). In experiment 2, hundred and forty weanling pigs were randomly assigned to one of four treatments differing in Ca levels (high and low) and sources (CaCl 2 and CaCO 3 ) in a 2 × 2 factorial arrangement. There were 10 pigs per replicate in both experiments, with 6 replicates in each treatment, and they were conducted in two phases (phase 1, days 0–14; phase 2, days 15–28). In experiment 1, body weight (BW), average daily gain (ADG), and growth to feed ratio (G/F) increased as the Ca level decreased ( p < 0.05). P digestibility was higher in the low-Ca diet group than in the high-Ca diet group ( p <0.05). In experiment 2, the final BW, ADG, and G/F increased in the CaCl 2 diet group compared with the case in the CaCO 3 diet group ( p < 0.05). The digestibility of crude protein (CP), Ca, and P was higher in the CaCl 2 diet group than in the CaCO 3 diet group ( p < 0.05). Cl − levels were higher in the CaCl 2 diet group than in the CaCO 3 diet group ( p < 0.05). The bicarbonate (HCO 3 − ), base excess (BE), and electrolyte balance (EB) levels were lower in the CaCl 2 diet group than in the CaCO 3 diet group ( p < 0.05). Hematocrit increased as the Ca level decreased ( p < 0.05). The HCO 3 − interacted with the Ca sources and thus, affected the Ca levels ( p < 0.05). Bone ash, Ca, and P were downregulated in the low-Ca diet group compared with the case in the high-Ca diet group. Overall, the low dietary Ca supplementation led to greater growth performance. Furthermore, CaCl 2 appeared to be a better Ca source than CaCO 3 because of the greater digestibility of CP, Ca, and P, and improved EB.

Context The occurrence of second parity syndrome is a major reason for culling sows depending on the bodyweight and energy level balance during the first lactation. Equally, the nutrition of gilts during the rearing period influences the age of first oestrus, longevity and reproductive performance. Aims The experiment investigated: (1) the influence of gilt mating age (early [EL], middle [MD] and late [LT]) at the first parity on reproductive performance, and (2) the interaction between dietary energy levels (high, 3320 kcal/kg; low, 3120 kcal/kg) and mating age. Methods A total of 120 crossbred (Duroc × Landrace × Yorkshire) gilts were allotted to six treatments according to a 3 × 2 factorial arrangement based on mating age (EL [222 days], MD [244 days] and LT [264 days]) at the first parity and dietary energy levels (high, 3320 kcal/kg; low, 3120 kcal/kg). The average weight of gilts were 141 ± 3, 153 ± 3 and 164 ± 3 for the EL, MD and LT groups, respectively. Results High-energy diets tended to increase the growth rate of gilts (P = 0.083). At insemination, bodyweight and back-fat thickness were higher (P < 0.05) in the LT group. Back-fat thickness at farrowing was lower (P < 0.05) in the EL group. The back-fat thickness loss during lactation was highest in the LT group (P < 0.05) during parity one and two. Feed intake during lactation was significantly reduced (P < 0.05) in the LT gilts in parity one. Insemination age and dietary energy levels had no significant effects on, litter size, litter weight and weaning to oestrus interval. A higher blood insulin-like growth factor (P < 0.05) was observed in the EL gilts during the first service and weaning. Conclusion Based on these findings, early inseminated gilts had a lower bodyweight loss during lactation without affecting litter size or growth, which in the long term may positively impact culling age. Implication This information may guide swine farmers on the most appropriate age to breed gilts at first service for increased reproductive life. The provision of high-energy feeds did not translate into any meaningful interaction towards improving reproductive performance in gilts.

Weaning stress is the most common issue in swine farms, which increases mortality and morbidity. The use of artificial light is an option for modifying the immune system and metabolic pathways. This study aimed to evaluate the influence of ultraweak light (Photonia) on growth performance, immune system and metabolism of weanling pigs, and the carry‐over effect on the growth performance in postweanling growing stages. A total of 30 weaned pigs with an average initial body weight of 7.06 ± 0.11 kg (age: 21 days) were allotted two treatments (Control and Photonia) with 15 replicates. The pelleted form diets were prepared for pigs in three phases including phase 1 (Days 0–14), phase 2 (Days 15–28) and phase 3 (Days 29–48). The gain‐to‐feed ratio (G:F) of pigs was significantly greater in the Photonia treatment. On Day 28, a higher concentration of immunoglobin A (IgA) (p < 0.01) and IgG (p < 0.01) was observed in the Photonia pigs. On Day 48, the Photonia treatment showed a greater serum IgA (p < 0.01) and IgG (p < 0.05). The concentration of interleukin (IL)‐6 was decreased (p < 0.05) in the Photonia treatment. At Day 48, the concentrations of tumour necrotic factor‐α, IL‐1β and IL‐6 in serum were decreased (p < 0.05) in pigs in the Photonia treatment. Metabolic pathways analysis showed that the Photonia treatment increased the d‐glutamine, d‐glutamate, alanine, aspartate, glutamate and phenylalanine compared with the control treatment. In conclusion, the use of Photonia for weanling pigs is recommended due to improved G:F, immune status and activation of amino acids metabolic pathways including d‐glutamine, d‐glutamate, alanine, aspartate, glutamate and phenylalanine.