'There are four new years," explains the Mishnah (Rosh Hashanah 1:1). The best known is Tishri 1, the New Year par excellence, Rosh Hashanah, when "all who enter the world pass before God". Next most familiar is Shevat 15, the New Year for Trees, the Jewish "Earth Day". Least known is Ellul 1, the New Year for the Tithing of Cattle.

It sounds irrelevant: how many of us today keep cows? And anyway the date only really mattered while the Temple stood.

Yet there is a drive among Jewish environmentalists to develop the day into a Jewish New Year for Animals. This isn't merely sentimental. It's not about bringing our mongrels to shul for mi-sheberachs, let alone making a chopped-liver effigy of them or a vegetarian equivalent for kiddush, like the worst excesses of the bark-mitzvah catering market.

It's about seeing the sacred in all living beings and understanding our own place in an immense and intricate material and spiritual ecology. This belongs to what the sages called "accepting the yoke of the sovereignty of God", by acknowledging that we exist not to exploit and kill other forms of life, though we may use them thoughtfully and compassionately for our livelihood, but to protect the earth and its creatures which are entrusted by God to our care. It is a day on which to abjure cruelty and affirm our kinship with creation.

The Jewish way is not to invent a new date but to build on existing moments in the traditional calendar. What then was the New Year for the Tithing of Cattle? Maimonides describes it in Hilchot Bechorot (6:1): "It is a positive commandment to separate one out of every 10 kosher animals born to a person each year. This mitzvah applies only to cattle and sheep, as Leviticus 27:32 states: 'All the tithes of your cattle and sheep...'"

The Talmud deemed that most animals were born by the month of Av; a tenth of the newly born could therefore be consecrated for Temple sacrifice at the start of Ellul.

This hardly sounds like the best date to celebrate animal life. But it shows that our ancestors lived in close connection with animals. The Torah makes this clear. If a sheep or ox gets lost or an over-laden donkey collapses under its load we must help (Deuteronomy 22:1-4). Such occurrences must have been as frequent then as traffic accidents today. It was a civilisation less anthropocentric and less alienated from the natural world than now.

This closeness is expressed in Judaism's injunction against tza'ar ba'alei chayim, inflicting suffering on living creatures. Like Buddhist prayer for "all sentient beings", it shows deep compassion before the fact that animals also experience pain. Based on the Torah's ban against immediately separating young from their mothers, Maimonides understood this to include emotional suffering as well. If "God's mercies are upon all God's works" (Psalm 145:9), human mercies should include animals too.

This attitude is a sharp indictment of how we treat animals today. The meat industry may be less culpable for how it kills them than for how it makes them live, with the immense cruelties of factory production and mass transportation. The dairy industry is also far from innocent.

It's sometimes argued that compassion should be reserved for humans, that "Nazis were sentimental about pets". The latter may be true. Yet there's a profound connection between our attitudes to human pain and animal pain. What we don't see doesn't bother us. Just as we're generally untroubled by the pain entailed in meat and eggs arriving neatly on the shelf, so we're often heedless of the human misery behind so many products we want to buy cheap.

The Bible is also deeply sensitive to wild animals. The Psalmist feels in the deer's longing for water the image of our yearning for God. The author of Job finds in the secretiveness of animals a sign of God's mysteries. Rabbinic Judaism countenances encroachment on the natural world out of genuine human need, but not through carelessness, cruelty, greed, wastefulness, or ever to an extent which threatens biodiversity. After all, we say daily, "God, how manifold are your works."

What might a New Year for Animals look like? Ellul 1 is when we first blow the shofar, whose raw call awakens an awareness of a world deeper and more extensive than human society alone. This cry should be accompanied by two modes of liturgy: penitence, "For the sins we've committed in cruelty to lives with no political voice or economic power"; and praise, "Praise God, wild and domestic animals, creeping creatures and birds on the wing" (Psalm 148). If I was brave, I would add a Council of All Being, developed by Rainforest to help us recognise, not just intellectually but experientially, our bond with nature. Participants choose an animal, and through quiet reflection, try to imagine how life feels from inside its skin.

Then we should go out and care for the beautiful world committed to our trust.

Jonathan Wittenberg is senior rabbi of Masorti Judaism