It is permissible to lend animals and it is recommended to pay in full, giving something better than that which ts owed
حَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا خَالِدُ بْنُ مَخْلَدٍ، عَنْ مُحَمَّدِ بْنِ جَعْفَرٍ، سَمِعْتُ زَيْدَ بْنَ أَسْلَمَ، أَخْبَرَنَا عَطَاءُ بْنُ يَسَارٍ، عَنْ أَبِي رَافِعٍ، مَوْلَى رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ اسْتَسْلَفَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَكْرًا . بِمِثْلِهِ غَيْرَ أَنَّهُ قَالَ " فَإِنَّ خَيْرَ عِبَادِ اللَّهِ أَحْسَنُهُمْ قَضَاءً " .
Abu Rafi', the freed slave of Allah's Messenger (ﷺ), said: Allah's Messenger (ﷺ) took as a loan (the rest of the hadith is the same), but with this variation that he (the Holy Prophet) said: Good amongst the servants of Allah is he who is best in paying off the debt.