## 1 Introduction  
Feed and feeding techniques are essential aspects of precision livestock farming to ensure birds' daily nutrient requirements are provided precisely and in a timely manner for efficient and sustainable animal production [1, 2]. Feed accounts for over 65% of the total production costs in the poultry industry [3]. By using precision feeding, which may more accurately meet poultry nutrient requirements, the cost could be reduced further while optimising bird performance and health and increasing the economic sustainability of the industry [4; 5]. The concept behind the precision feeding program for poultry involves blending two or more diets to accurately fulfil the birds' daily nutritional needs, thereby avoiding excess or deficiency of dietary nutrients [6; 7]. This is particularly important for layer production given the current economic instability caused by high feed costs and volatile egg prices. Hens are typically fed three dietary phases during the laying period, each consisting of a standard diet throughout the day. However, recent studies have shown that hens have different nutrient requirements across the day due to the bio-cyclic nature of egg formation [8; 9]. Based on reproductive physiology, hens require more protein, fat, and energy in their diet following oviposition, and the ovulation of the next egg yolk occurs in the morning when albumin and yolk start to form [10; 11]. On the other hand, there is a comparatively higher requirement for calcium (Ca) during egg membrane and eggshell formation in the afternoon and evening [12; 13]. This was further supported by the results of previous studies, which showed that hens' intake of protein and energy sources increased in the morning around the peak of egg production, and Ca intake was found to be higher later in the day when hens were offered self-selection of nutrients [14]. Therefore, in a conventional feeding strategy, birds fed a constant nutrient diet throughout the day might not achieve the optimal utilisation of all dietary nutrients [14; 15]. The recurring pattern of hen reproductive physiology may result in reduced energy and protein requirements in the afternoon, which should present substantial cost savings for egg producers. A feeding strategy that has garnered attention in recent years is AM/PM feeding, also referred to as split feeding. AM/PM feeding is a carefully structured feeding regime that involves dividing the daily feed allocation into two distinct dietary formulae, typically offered in the morning and evening separately [16; 17]. For laying hens, the practice of feeding in the morning and evening can involve providing a diet rich in energy and protein but low in Ca in the morning (AM), followed by a diet lower in energy and protein but higher in Ca in the afternoon/evening (PM) [18; 19; 20]. This approach is rooted in the fundamental understanding of layer hens' natural feeding behaviour and physiology, which might have profound impacts on egg production, egg quality, and health [9]. The AM/PM feeding strategy does not require significant investment in technology to employ and instead takes full advantage of the hens' biological cycles. A study by [PERSON] JR and [PERSON] [10] demonstrated that hens fed a low protein diet (13% crude protein, CP) in the morning (08:00 h-14:00 h) and a high protein diet (16% CP) in the afternoon (14:00 h-08:00 h) presented no difference in egg production and egg size compared to hens fed a 16% CP diet for the whole day. Another study by [PERSON] et al. [14] determined the effect of feeding a diet containing high energy (2900 kcal/kg ME) and protein (18.5% CP) and low Ca (1.6%) levels and a diet low in energy (2323 kcal/kg ME) and protein (13.3% CP) and high in Ca (4.5%), where hens were offered the experimental diets during the morning (2 h before expected oviposition) and also 2 h, 4 h, 6 h, 8 h, and 10 h after oviposition.