Perinatal nutrition greatly affects the productive success of chickens, and in-ovo feeding is the cutting-edge approach to this issue. This first article, of a series of two, explores the main events in the last days of embryo development, and how in-ovo feeding can enhance the performance of chickens in the perinatal period and throughout their lives.
Chicks are precocious birds. They start searching for food immediately after hatching, beginning to grow from the first moment of their lives. However, as shown in Figure 1, eggs placed in the same incubator tray can hatch in a timespan of up to 48 hours. Chicks that hatch earlier may not have access to feed for many hours. Therefore, early hatching entails a disadvantage respect of the medium and late hatchers, due to the long fasting period and the dehydration that may also occur.
Figure 1. Hatching curve showing early hatch (orange), medium hatch (light blue) and late hatch (dark blue) (after Wang et al., 2014)
Apart from the hatching window (length of time taken for all the eggs to hatch), procedures such as chick management at the hatchery (sexing, chick classification, vaccination. etc.) and transport to the farm, imply further delays in accessing feed and water for the first time. Therefore, chicks will continue losing weight due to dehydration and the utilization of yolk and muscle as energy sources.
Depending on the factors mentioned above, it is not unusual for chicks to be retained at the hatchery for up to 72 hours without feed or water. This results in a series of undesired effects, mainly:
Such undesirable effects will lead to irreversible delays in productive performance and growth until slaughter. Today, such effects are even more pronounced since the modem broiler strains are characterised by a higher metabolic rate (and higher maintenance requirements).
This article reviews strategies for perinatal feeding of chicks, designed to minimise the negative effect of delayed feed intake. Part 1 analyses the importance of the perinatal period on the intestinal and immunological development of chicks, as well as the new concepts on in-ovo feeding of embryos.
Currently, broilers can reach slaughter weight faster than a few years back. The incubation period and the first week of life represent a higher proportion of the total lifespan of the bird. Therefore, the processes occurring in the perinatal period- just before hatching and during the first days post-hatch- will have a large impact on the growth of the chicken throughout of its life.
Today’s high growth rates (>70g/day) demand a re-evaluation of nutrient supply during the perinatal period.
Each additional gram of body weight at 7 days of age, translates into additional 5 grams of body weight at day 49 (Leeson and Summers, 2001). Therefore, any delay in feeding during the first days of life will reduce the final body weight.
The perinatal period is critical for intestinal development. The sooner this development is completed, the faster the chick will be able to utilize dietary nutrients, maximising its genetic potential and developing a strong immune system.
Feeding strategies during the perinatal period
Today, it is possible to feed the embryo by injecting nutrients in the amniotic fluid, during the last phase of embryonic development. Although there are not yet regulations in place in the European Union, this is a practice growing in countries such as United Sates and Brazil.
Figure 2. In-ovo feeding
The injection of nutrients in the egg is timed with the moment in which the embryo starts ingesting amniotic fluid (around day 15 of incubation). This allows those nutrients to reach the embryo intestine without major problems. Figure 2 shows the method of in-ovo feeding. Different nutritional supplements can be administered using this technique
Shafey et al. (2014) inoculated a mix of lysin, arginine, glutamine, glycine, and proline in eggs, at day 15 of incubation. They observed not only a significant increase in embryo weight to egg weight ratio, but also a significant improvement in the performance of the chickens during the first three weeks of life. Similarly, Coşkun et al. (2014) showed that injecting DL-methionine in the amnion at day 16 resulted in increased chick weight relative to egg weight (72.7% vs. 70% of control group). Similar results had already been reported by Kadam et.al. (2009), who observed that injecting threonine in eggs had a positive effect on chick weight at hatch. More recently, Kermashashi et al. (2017) indicated that injecting threonine in quail eggs increased length and surface area of intestinal villi in newly hatched chicks.
The in-ovo injection of arginine is of particular interest, since it is glucogenic and can also be utilized in the synthesis of other amino.
Figure 3. Effect of in-ovo injection of arginine on the ratio between villi height and crypt depth in the duodenum of chicks during the first of life. Different letters next to values of same age indicate significant differences (p<0.001) (Gao et al., 2018a).
The injection of amino acids in the last stage of incubation has a positive effect on the growth and development of lymphoid organs, as observed by Gaafar et al. (2013). This contributes to establish the foundations of a solid immune system during the perinatal period.
Figure 4. The effect of inoculating arginine in-ovo at 17.5 days of incubation, on the body weight of chickens at 42 days of age (Gao et al., 2018b). Different letters show significant differences (P>0.001)
The fast growth of chicken embryos is associated with a high energy demand. Glucose is stored in embryos in the form of glycogen in liver and muscles. However, this natural source of glucose does not cover the metabolic requirements of the embryo in the last phases of development. Therefore, the embryo resorts to gluconeogenesis to produce glucose from available lipids and proteins, hence compromising embryonic growth.
As Kucharska-Gaca et al. (2017) indicated, the in-ovo administration of different types of carbohydrates (glucose, sucrose, maltose, dextrin) increases the availability of energy sources for the embryo, reducing the utilization of proteins and lipids in gluconeogenesis. However, Zhai et al. (2011) advise not to use fructose in-ovo because it reduces the body weight of newly hatched chicks.
Bhanja et al. (2008) and Kornasio et al.(2011), injecting in-ovo glucose and dextrose (respectively) at day 18, reported an improvement in intestine development in newly hatched chicks. These findings may explain higher body weights observed in chickens fed carbohydrates in-ovo in the last days of incubation.
Smirnov et al. (2006) injected a combination of sucrose, maltose, and dextrin at 17.5 days of incubation. They observed a higher morphological development of the intestinal epithelium, with an increased number of Goblet cells. They also reported a higher genetical expression of mucins (first intestinal barrier against pathogens) in newly hatched chicks (Fig. 5), which may a positive impact on the health status in the first hours of life.
Figure 5. Effect of in-ovo injection of carbohydrates on the genetic expression of mucins in chicks on perinatal period (after Smirnov et al., 2006). Different letters show statistical significance.
During embryonic development, several oxidative processes of the yolk lipids occur. They are accompanied by the production of a large amount of free radicals, which damage cellular membranes due to the degradation of polyunsaturated fatty acids. The presence of vitamins in the egg counteracts the negative effect of free radicals, hence protecting the embryo against cellular damage.
The in-ovo administration of exogenous vitamins contributes to the growth of broiler chickens and could modulate their resistance against diseases (Kucharska et al., 2017). The positive effect of injecting vitamins in fertile eggs have been demonstrated by different authors (Bhanja et al., 2007; Nowaczewski et al., 2012; Selim et al., 2012; Goel et al., 2013; Salary et al., 2014; Yair et al. 2015; Sgavioli et al., 2016).
The vitamins more frequently used in those studies were vitamin A, B1, B2. B6, C, E, and D3. The main observed effects were:
Together with amino acids, carbohydrates, and vitamins, the in-ovo administration of probiotics has become a widely extended practice in countries where in-ovo feeding is being implemented.
In the later years, the Poultry Science Department at the Mississippi State University has performed remarkable work in this topic. In one of their projects, they demonstrated that in-ovo administration of 1.4×107 colony forming units (CFU) of a strain of Enterococcus faecium at 18 days of incubation, reduced chick mortality in 50% during the first week of life (Beck et al., 2016). They have also confirmed that E. faecium colonises the embryo intestine and remains in it for, at least, the first week of life (Blanch et al., 2017).
More recently, the same team (Dittoe et al., 2018) observed that in-ovo administration of E. faecium results in significant increase of the ratio between intestinal size and chick body weight, when measured 12 hours after hatch (Table 1). The same work reported that,12 hours post-hatch, the yolk sac was smaller in chicks coming from eggs inoculated with probiotic. This suggested that those chicks utilised the nutrients of the yolk sac more efficiently during the last days of incubation.
Table 1. Effect of in-ovo administration of probiotic on relative intestine size (% vs. body weight) as measured in chicks 12 hours after hatch (Dittoe et al., 2018). Different superscripts show significant differences.
Similar to the response obtained after the in-ovo administration of probiotics, in-ovo administration of mannan oligosaccharides (MOS) resulted in day-old chicks with more mature enterocytes, having higher digestive and absorptive capacities (Cheled-Shoval y col., 2011).
The in-ovo administration of different nutrients before hatch seems to be a good strategy to promote not only high liveability of newly hatched chicks, but also the growth and immunity development of broiler chickens throughout their life.
In the second part of this article, we will discuss possible feeding strategies immediately after hatch during the first days of the chick’s life.
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