Guru Granth Sahib is not Diet Chart
Dhan Sri Guru Granth Sahib believes that same life is present in Goat, Chicken, Lamb, Fish, the same life is present in Pulses, Vegetables, Mushrooms, Trees, Herbs and Shurbs etc.
If Karma Philosophy(Non Gurmat) is applicable for chicken, goats, the same should be apply to other lives too.
Some of related concepts which got stick on mouths of Sikhs, due to intrusion of Vaishnav ideology into Sikhs, having no significance in Gurmat, are highlighted here under:
"Jaisa Ann waisa Mann":
Guru Granth Sahib does not believe in philosophy of "As is the food, So is the mind"(Jaisa Ann Waisa Mann).
This is Non-Gurmat baseless, impractical concept means that food can influence or degrade someone's mind, thoughts and behavior. One should make it clear that food must not change ideology of Gurmukh. It can not harm spiritual growth or degrade wisdom, or enlightenment, attained by a Soul, through Gurbani.
A healthy physical life is encouraged in Sikh ideology and food which helps in that is encouraged.
"Jeev Hatya":
Guru Granth Sahib does not believe in concept of "Jeev Hatya"(Killing of soul).
To understand this, First we should understand, What is Jeev? As per Guru Granth Sahib. Jeev term is designated to Soul(not 'Body'). For 'Body' Pind term is used. (ਜੀਉ ਪਿੰਡੁ ਸਭੁ ਤੇਰੈ ਪਾਸਿ ॥੩॥).
The Soul forms the body(Andaj, Jeraj, Setaj and Utbhuj) and abandon it, but never dies. (ਮਰਣਹਾਰੁ ਇਹੁ ਜੀਅਰਾ ਨਾਹੀ ॥੩॥ ).
Gurmat philosophy explains that everything happens in supreme command(called Hukam). Life and Death happen in Supreme Command. It is Human's illusion(Bharam) that Human can Kill, but truth is that The supreme command(Hukam) invokes to kill, on one side, and give birth, on other side.
Sikhs are worshiper of almighty which is creator, as well as destroyer.
"Daya":
Guru Granth Sahib believes in "Daya" but it is not limited to eating meat.
The only concept of Daya is to guide the Jeev(also called Soul), how to swim across the worldly ocean (also called Bhavsagar) so that Soul could merge in the supreme command (also called Surt Shabad Bhavsagar Tariyey) and go away from cycles of incarnation.
Gurbani guides Pundits(religious preists) to do Daya on people i.e not to tangle them into false worships and practices like rituals, idolatry(Karamkaand) and guide them to purify their thoughts and take Gurmat wisdom(Gurmat Gyan) to swim across.
This is real and only concept of Daya on Soul. Other life forms are lower then Human, so they need to come in Human form(MANUKH DEHI) to attain salvation before that they are slave to Human(AVAR JONI TERI PANIHAARI) the reason Human use most of animal and plants for their various purposes, without seeking their permission.
"Animal Business and Spiritual attainment":
Guru Granth Sahib contains hymns of Sri Bhagat Sadhna Ji and Sri Bhagat Ravidas Ji who had business related to Flesh of Animals. These both saints crossed temporal ocean(or Bhavsagar) and that too remained in same profession, But by taking Raam Naam i.e Wisdom of Rama.
If animal flesh did not harm their spirituality how could flesh degrade a learner? but do we learn?
Misinterpretations of Guru Granth Sahib on Meat Issue
