In plain words
Agriculture, care of cattle, and trade are vaiśya-Karma born of Svabhāva; work characterized by service is also śūdra-Karma born of Svabhāva.
Word for word
Farming, cattle-keeping and trade: the duty of the vaiśya, born of svabhāva; duty of the nature of service is also the śūdra's, born of svabhāva.
The commentators
Bhagavadgītābhāṣyam· bhāṣya
कृषिगौरक्ष्यवाणिज्यं कृषिश्च गौरक्ष्यं च वाणिज्यं च कृषिगौरक्ष्यवाणिज्यम् , कृषिः भूमेः विलेखनम् , गौरक्ष्यं गाः रक्षतीति गोरक्षः तस्य भावः गौरक्ष्यम् , पाशुपाल्यम् इत्यर्थः, वाणिज्यं वणिक्कर्म क्रयविक्रयादिलक्षणं वैश्यकर्म वैश्यजातेः कर्म वैश्यकर्म स्वभावजम् । परिचर्यात्मकं शुश्रूषास्वभावं कर्म शूद्रस्यापि स्वभावजम् ॥ ४४ ॥
In plain words
'Farming, cattle-tending, and trade' — that is farming, and cattle-tending, and trade, all bundled into one word. Farming means turning over the earth. Cattle-tending: someone who protects cows is a cowherd, and cattle-tending is simply what it is to be that — in other words, herding livestock. Trade is a merchant's work: buying, selling, and everything like that. 'Vaishya-duty' is simply the duty belonging to the vaishya class, born of his own nature. And service — work whose very character is eager attendance on others — is, just the same, born of nature for the shudra.
Close to the Sanskrit
'Kṛṣi-gaurakṣya-vāṇijya' means kṛṣi and gaurakṣya and vāṇijya, that is, kṛṣi-gaurakṣya-vāṇijya. Kṛṣi means the tilling of the earth. Gaurakṣya: 'he protects cows' — thus one is called a gorakṣa; the state of being that is gaurakṣya, that is, animal husbandry — that is the meaning. Vāṇijya means a merchant's work, characterized by buying, selling, and so forth; 'vaishya-karma' means the duty of the vaishya class — vaishya-duty, born of its own nature. Work in the nature of attendance, having the character of eager service, is also born of nature for the shudra.