"The Maasai love cattle and children, in that order". This statement very much captures the importance of pastoralism within Maasai culture. The Maasai have developed a highly specialised pastoralist way of living.
For the Maasai, cattle are the primary source of food and drink (Maasai do not eat vegetables, they believe it is food for cattle and as such part of a different stage in the food chain). Cattle are the currency for all kinds of interpersonal settlements, and the number of cattle one owns measures wealth.
The Maasai love for cattle also determines their attitude towards wild animals. Maasai have great respect for nature in general and do not kill wild animals, unless they form a threat to cattle and if so, its meat is not eaten. In fact, Maasai look down upon hunter-gathering people, who are considered greedy, unrestrained, and uncultured (farmers, are looked down upon too, as they destroy grazing land to plant crops in demeaning agricultural labour).
The love for cattle shows in other ways too. The sport of lion hunting Maasai warriors use to show their courage, is in reality just another way of getting rid of lions and their threat to livestock. Warriors also regularly engage in - highly riskful - cattle raids to show their bravery. They do not consider cattle raiding a crime. They believe that God has given cattle to the Maasai and that all cattle in the world belong to the Maasai people, so in cattle raids they are only taking what already belongs to them.