Abstract
BackgroundReplacement gilts are typically fed ad libitum, whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits. The objective of this study was to investigate the effect of meal frequency on the metabolic status and ovarian follicular development in gilts.MethodsA total of 36 gilts (Landrace × Yorkshire) with an age of 150±3 d and a body weight of 77.6±3.8 kg were randomly allocated into one of three groups (n = 12 in each group), and based on the group allocation, the gilts were fed at a frequency of one meal (T1), two meals (T2), or six meals per day (T6) for 14 consecutive weeks. The effects of the meal frequency on growth preference, nutrient utilization, short-chain fatty acid production by gut microbial, the post-meal dynamics in the metabolic status, reproductive hormone secretions, and ovarian follicular development in the gilts were measured.ResultsThe gilts in the T1 group presented a higher average daily gain (+ 48 g/d, P < 0.05) and a higher body weight (+ 4.9 kg, P < 0.05) than those in the T6 group. The meal frequency had no effect on the apparent digestibility of dry matter, crude protein, ether extract, ash, and gross energy, with the exception that the T1 gilts exhibited a greater NDF digestibility than the T6 gilts (P < 0.05). The nitrogen balance analysis revealed that the T1 gilts presented decreased urine excretion of nitrogen (− 8.17 g/d, P < 0.05) and higher nitrogen retention (+ 9.81 g/d, P < 0.05), and thus exhibited higher nitrogen utilization than the T6 gilts. The time-course dynamics of glucose, α-amino nitrogen, urea, lactate, and insulin levels in serum revealed that the T1 group exhibited higher utilization of nutrients after a meal than the T2 or T6 gilts. The T1 gilts also had a higher acetate content and SCFAs in feces than the T6 gilts (P < 0.05). The age, body weight and backfat thickness of the gilts at first estrous expression were not affected by the meal frequency, but the gilts in the T1 group had higher levels of serum luteinizing hormone on the 18th day of the 3rd estrus cycle and 17β-estradiol, a larger number of growing follicles and corpora lutea, and higher mRNA expression levels of genes related to follicular development on the 19th day of the 3rd estrus cycle.ConclusionsThe current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts, and thus provide new insights into the nutritional strategy for replacement gilts, and the dietary pattern for other mammals, such as humans.
Highlights
Replacement gilts are typically fed ad libitum, whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits
The current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts, and provide new insights into the nutritional strategy for replacement gilts, and the dietary pattern for other mammals, such as humans
Replacement gilts are typically fed ad libitum, a growing body of evidence reveals that this free eating pattern is associated with an increased prevalence of metabolic diseases in humans and rodents [6,7,8], and in contrast, studies of laboratory animals and humans have shown that a decreased meal frequency (MF) can increase insulin sensitivity and thereby reduce obesity related metabolic diseases, and even extend the lifespan [7,8,9]
Summary
Replacement gilts are typically fed ad libitum, whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits. Decreasing the MF from 12 meals per day to 2 meals per day for 3 or 8 weeks can alter the nutrient utilization, and inflammation status of 30-kg or 60-kg growing male pigs [9, 12] This evidence indicates that the MF might play a critical role in the female reproductive system because a body of experimental evidence indicates a fundamental link between the metabolic status and the normal estrus cycle [3,4,5]. The objective of this study was to investigate the effect of MF on growth preference, short-chain fatty acids (SCFAs) production by the gut microbiota, the post-meal dynamics in the metabolic status, reproductive hormone secretion, and the ovarian follicular development in gilts
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